Geotechncial Report - Tran Van Viet

REPORT ON

GEOTECHNICAL INVESTIGATION INVESTIGATION Item: main factory Stage: first phase for construction design

Reported by: P.E.

HANOI JANUARY JANUARY 2010

TRAN VAN VIET

TEXT I II

INTRODUCTION OUTLINE OF NATURAL CONDITION II.1 II.2 II.3 II.4

5 5

Location & Topographic Condition Regional Climate Condition Regional Geology Condition Regional Earthquake Condition

5 5 9

III RESULT OF GEOTECHNICAL INVESTIGATION III.1 Boring and Sampling III.2 Standard Penetration Test (SPT) III.3 Menard Pressuremeter Test (PMT) III.4 Criterion for Soil & Rock Classification Classification III.5 Soil & Rock Description & Layers Division III.6 Engineering Properties of Soil & Rock Layers III.7 Groundwater III.8 Embankment Material

12 12 12 13 14 15 18 24 25

IV GEOPHYSICAL EXPLORATION IV.1 Earth Resistivity Sounding Method (RSM) IV.2 Seismic Down-hole Sounding Method (SDM)

26 26 27

V

30 30 30 33 40

GEOTECHNICAL ENGINEERING ANALYSIS V.1 Principal Matters for Geotechnical Geotechnical Analysis V.2 Analysis of Shallow Foundation V.3 Analysis of Pile Foundation V.4 Analysis of Liquefaction of Ground due to Seismic

VI CONCLUSION AND RECOMMENDATION RECOMMENDATI ON REFFERENCE DOCUMENTS

APPENDICES Appendix 1 Appendix 2 Appendix 3

45 47

- Plan of Location of Boreholes - Geotechnical Cross-Sections Cross-Sections - Record of Boring Logs

VOLUME 2 Appendix 4 Appendix 5

- Synthesis Table of Laboratory Test on Soil & Rock - Tables on Chemical Analysis for Groundwater and Soil

Appendix 6 Appendix 7

- Tables and Graphics of Pressuremeter Pressuremet er Test - Report on Earth Resistivity Resistivit y Sounding Method

Appendix 8

- Report on Seismic Down-hole Sounding Method

Appendix 9 - Graphics and Tables Tables of Laboratory Laboratory Test Test on Soil Soil

Union of Survey Companies (USCo. (USCo.))

91 Phung Hung, Ha Noi, Viet Nam - Phone: (04) 39231540, Fax: 38245708

2

TEXT I II

INTRODUCTION OUTLINE OF NATURAL CONDITION II.1 II.2 II.3 II.4

5 5

Location & Topographic Condition Regional Climate Condition Regional Geology Condition Regional Earthquake Condition

5 5 9

III RESULT OF GEOTECHNICAL INVESTIGATION III.1 Boring and Sampling III.2 Standard Penetration Test (SPT) III.3 Menard Pressuremeter Test (PMT) III.4 Criterion for Soil & Rock Classification Classification III.5 Soil & Rock Description & Layers Division III.6 Engineering Properties of Soil & Rock Layers III.7 Groundwater III.8 Embankment Material

12 12 12 13 14 15 18 24 25

IV GEOPHYSICAL EXPLORATION IV.1 Earth Resistivity Sounding Method (RSM) IV.2 Seismic Down-hole Sounding Method (SDM)

26 26 27

V

30 30 30 33 40

GEOTECHNICAL ENGINEERING ANALYSIS V.1 Principal Matters for Geotechnical Geotechnical Analysis V.2 Analysis of Shallow Foundation V.3 Analysis of Pile Foundation V.4 Analysis of Liquefaction of Ground due to Seismic

VI CONCLUSION AND RECOMMENDATION RECOMMENDATI ON REFFERENCE DOCUMENTS

APPENDICES Appendix 1 Appendix 2 Appendix 3

45 47

- Plan of Location of Boreholes - Geotechnical Cross-Sections Cross-Sections - Record of Boring Logs

VOLUME 2 Appendix 4 Appendix 5

- Synthesis Table of Laboratory Test on Soil & Rock - Tables on Chemical Analysis for Groundwater and Soil

Appendix 6 Appendix 7

- Tables and Graphics of Pressuremeter Pressuremet er Test - Report on Earth Resistivity Resistivit y Sounding Method

Appendix 8

- Report on Seismic Down-hole Sounding Method

Appendix 9 - Graphics and Tables Tables of Laboratory Laboratory Test Test on Soil Soil



2

INTRODUCTION This report presents the result on Geotechnical Investigation for Construction Design Stage of the Main Plant ….. The purposes of geotechnical investigation investigation are: - To clarify, as detail as possible, sub ground condition of the project items. - To make zoning of various subsurface areas with the same sub ground condition for recommendation recommendation of the foundation design. - To analyze various foundation types and geotechnical process for suggestions in foundation design study based on the comprehensive professional knowledge and local experiences. The Geotechnical Investigation was carried out on the bases of: - Geotechnical Engineering Investigation Outline for Construction Design Stage, which is prepared by Consultant Designer . Designer . - Program of Geotechnical Investigation Work prepared by Subsurface Investigation Contractor (USCo). ), dated November ….th, 2009, - Economical Contract No……..: Order …………. between the ………………………………………………………………. and the Union of Survey Companies (USCo-Vietnam). actual Vietnamese Standards Standards in combination with with the developed countries - Appropriate actual standards (ASTM, JIS, BSI,CHINA, NF...), which are suggested in use by Ministry Of Construction (see (see Reference). Reference). * * * All Site Investigation Information collected from site was analyzed, synthesized and compiled in “Geotechnical Investigation Report” by P.E. Tran Van Viet, USCo.’s Soil & Foundation Specialist and his assistants.

* * The completed quantity of the soil investigation for “ Preliminary Phase” for EPC Construction Design Stage is summarized in the table t able 1. Table 1: 1: Summarized Implemented Quantity of Site Investigation No

1

Work Items g n i l l i r D

No. of boreholes Total drilling length Drilling length in Soil Drilling length in Rock

Implemented Quantity 96

Method Wash water rotary drilling and coring



3

2

3

4

t s e T y r o t a r o b a L

Insitu h l p a o c y e S G

- Grain-size distribution - Physical Properties - Density - Organic matter - Direct Shear Test. - Unconfined Comp. Test - Triaxial Compression Test UU - Triaxial Compression Test CU - Long term Consolidation. Consolidation. - Short term Odometer - Permeability Test in Lab. - Test on rock cores - Chemical Anal. of Ground water - Chemical Analysis of Soil - Compaction Test of backfill Standard Penetration Test (SPT) Menard Pressuremeter Pressuremeter Test (PMT) Earth Resistivity Measurement Measurement Electrical Deep Sounding Wave Velocity by Seismic Down-holes

TCVN (4195 – 4202) – 1995 & Appropriate Appropriat e ASTM

ASTM 1586-94 D10, D60, FOND 72 Ρk (ohm-m)



Vp & Vs

4

II

OUTLINE OF NATURAL CONDITION OF PROJECT’S REGION

II.1

LOCATION & TOPOGRAPHIC CONDITION

The Mao Khe coal fired thermal power plant is located on a fairly high-land, which layout at the middle of Dong Trieu and Mao Khe towns and distanced from National Road 18 about 5km toward Northern (see figure 1). The site of main power plant and stack area (MPF) has been already razed-filled (see Drawing MK-KDC-00-G01-02), so it’s fairly smooth with ground elevation may vary about +9m to +10m. The dimension of MPF is about 454m x 454m, which is distanced to Cam River about 5 Km and distance to Mountains about 3km. II.2

REGIONAL CLIMATE

The Quang Ninh area is located within the Red River Delta, so the climate is which is classified in “AIII.1 Climate Zone” (after QCVN 02:2009/BXD)[13], which are characterized by tropical climate, monsoon with 02 separated seasons: - The rainy season (or summer season) extends from May to October with the weather is hot, wet, heavy precipitation and usually effected by typhoon, flood and torrent. This season is affected by South-East monsoon, so the wind-direction impacts from Tonkin Gulf. The maximum wind speed of storm may reach to grade XII or more (33.33 m/s or more). - The Dry season (or winter season) extends from November to April (next year); where the weather is cool, some time coldly, less rainy and usually drizzling rain. This season is effected by North-East monsoon (cold-air from Siberia), so the wind-direction fans from China Continental. According to basic data of Metheology & Hydrology of Viet Nam [13,14], the main information of climate for region of Red-River Delta may be summarized as follows: - Precipitation: Average annual precipitation about 1554.3mm and average evaporation is about 928.3mm. Yearly, the precipitation is highest in July and August (average monthly 288318mm) and the lowest values occurred in January (average 18.6mm). - Temperature: The average annual temperature is about 23.5 0C. The highest temperature occurred in Mai & June (annual average 28 0C, Max. 40.80C, Min. 210C; Max. Maximum 42.80C). The lowest temperature occurred in January (annual average 16 0C; Min. 2.70C; Max. 33.10C). - Humidity varies monthly in the years with and annual average about is 83-84%. The highest humidity encountered in March & April & August (average 86 - 87%) and lowest humidity encountered in November & December (average 81%) - Wind speed: varies monthly in the years with the highest values occurred from May to September (annual average is about 28 – 31m/s) and the lowest values occurred from January to March (annual average is 15m/s).

II.3

REGIONAL GEOLOGY CONDITION

According to Geology & Mineralogical Map, (scale 1/200 000), Sheet of Qu ảng Ninh, the sedimentation of this area is characterized by following typical formations. II.4

REGIONAL EARTHQUAKE CONDITION

According to the “Report of seismic hazard in Quang-Ninh Area”, prepared by Prof. Dr. Nguyen Dinh Xuyen (Institute of Physical Globe), the scenario of earthquake in the Dong Trieu Quang Ninh area (included Mao Khe thermal power plant) is follows: II.4.1 Tectonic Structure

Union of Survey Companies (USCo.)


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II.4.2

Tectonic Faults

II.4.3

Seismicity in Project Area

II.4.4

Selection of Seismic Parameters for Geotechnical Analysis

Based on analysis result of sub-ground condition of the project area and according to TCXDVN – 375 – 2006, the anti-seismic design parameters may be summarized and presented in the Table 2. Table 2: Summarise parameters for anti-seismic design from project area

Intensity, Imax (MSK)

Grade VII (After Seismic Zoning Map of Intensity) Grade VII (After correlation in Appendix K from TCXDVN – 375 – 2006) 0.1118 (After TCXDVN – 375 – 2006 ) Max. 5.9 (After Viet Nam Institute of Physical Globe - VIPG ) C Dense to medium dense Sand and Gravel or stiff Clay with ten to hundred meters (According to TCXDVN – 375 – 2006 - Table 3.1; Page 30)

Ground acceleration (PGA), Amax (g) Magnitude M, (Richter degree) Soil type symbol, S

Sc

Response spectrum horizontal Sc (T)

Sc Sc Sc

Response spectrum of elastic displacement SDc (T)

Period

TR (s) TC (s) TD (s)

⎤ ⋅ (η ⋅ 2 ,5 − 1) ⎥ ⇒ 0 ≤ T ≤ ⎣ T B ⎦ = Ag . S .η ⋅ 2 ,5 ⇒ T B ≤ T ≤ T C ⎡ T ⎤ = Ag . S .η ⋅ 2 ,5 ⋅ ⎢ C ⎥ ⇒ T C ≤ T ≤ T D ⎣ T ⎦ ⎡ T .T ⎤ = Ag . S .η ⋅ 2 ,5 ⋅ ⎢ C 2 D ⎥ ⇒ T D ≤ T ≤ 4 s ⎣ T ⎦ =

⎡

Ag . S .⎢1 +

T

⎡ T ⎤ S DC = Sc (T ) ⋅ ⎢ ⎣ 2.π ⎥⎦

T B

2

0.15 0.50 2.0



6

III

RESULT OF GEOTECHNICAL INVESTIGATION

Summarized data of boring, sampling, in-situ test and laboratory test for the Main Power Plant area (MPF), the synthesis of result shall be presented as follows: III.1

BORING AND SAMPLING

According to boreholes plan layout for MPF area, 96 boreholes have been disposed by Kadi Consortium for the “first phase” of geotechnical investigation. All drilling and sampling methods are in accordance to Vietnamese Standards in combination with the relevant developed Ameriacano-Erropean’s countries. However, the boring depth of all boreholes has been decided by the Kadi’s Supervisor (Chinese) at site. 11 drill rigs have been mobilized at the for boring exploration and the used are Model XY1A made in China (see Figure 3). Based on equipment characteristics, the rotary drilling method is appropriate for this sub-ground condition, with the function in sampling all type of soil & rock samples and preboreholes for in-situ tests (SPT, Pressuremeter and Groundwater…)

Figure 3: Drilling rig Model XY1A

Single or double tube core barrels fitted with diamond or tungsten tipped Figure 4: Standard open sampler core bits shall be selected at site depe nding of the rock type and weathering-jointing degree. The conventional tube core barrel consists of a tube in diameter varies from 76mm to 127mm with 1,5m to 2.0m in length. Basically, drilling and boring method is according to TCVN 2683-1991 & 22TCN 259-2000 and reference to ASTM D 1452 -80 and BS 5390-1999. Sampling of soil and rock samples in using of equipment and procedure is in accordance to 22TCN 2592000 and referenced to standards: ASTM D 1587-00 or BS 5930-1999. Generally, the undisturbed samples are recovered by open-samples, thin-walled sampler (see Figure 4) and for hard residual soil and weathered rock; the samples are taken form core in single or double barrel samplers (see Figure 5). The disturbed samples shall be taken in SPT’s split-spoon sampler or rest soil from undisturbed sampling and coring. Figure 5: Coring samplers

III.2

STANDARD PENETRATION TEST (SPT)



7

SPT is the most widely in-situ test for sub ground investigation carried out right in boreholes and the equipment is attached with drilling rig. The result of SPT may provide the sol samples for identification and classification at site and test result for soil state judgment and for foundation analysis. Beside, dynamic resistance (illustrated by number of blows per conventional penetration, N30), the SPT may also provide the undisturbed samples contained in split-spoon sampler (see figure 6) for soil & rock identification, description and some identification tests. According Kadi Consortium’s Consultant’s requirement, the SPT needs to be carried out in all soils and weathered soft rock, with general spacing varies from 2.0m-3m and in every change of the stratum, but total tests are illustrated on table 1. The equipment and procedure shall be in accordance to TCXD Figure 6: Split-spoon sampler from SPT 226:1999 or ASTM D 15782000. The bottom of boreholes must be well cleaned before driving test. Three driving attempts shall be executed for every 15cm penetration and the N 30 values shall be the sum of the last two. All SPT result shall be illustrated on the Boring Logs and the values of N30 shall be presented on Charts (see Appendices 2, 3). In case of very dense gravelcobble (or soft rock) encountered, if the first attempt (blows per 15cm) is more than 50 blows, test may be finished. The recording shall be 50 blows per the real penetration (example first: 50/8cm). Otherwise, the same manner shall be dealing with the second or the third attempt. III.3

MENARD PRESSUREMTER TEST (PMT)

Pressuremeter is an effective In-situ Test Method in Geotechnical Investigation, which is to provide concomitantly engineering properties of soil and rock layers such (Limit pressure “P L” and lateral modulus “E P” along borehole), which are the important parameters for foundation engineering analysis. The PMT is very effective for sub-ground investigation of jointed & weathered rocks; granular soils, where they are impossible in recovering of undisturbed samples or cores for Laboratory Test. Pre-borehole from PMT is also provide the soil for identification, description and simple classification and of soil and rock. The actual equipment used for this geotechnical investigation is the latest version “Type G” (see Figure 7). Testing standards and interpretation are in accordance to the Menard’s Notices and Technique Regles: D10 & D60; FOND.72 from LCPC-SEATRA, France’s Normes & Regles Techniques: NF-P94-110, DTU.13.2 and F62 ( Note: There is still no Standard for PMT in Viet Nam ). 03 positions of PMT have been requested by China’s supervisors, such as CK46.PR, CK80.PR & CK95.PR). The result is presented in form of 02 kinds of graphics (see Appendix 6): Figure 7: Menard Pressuremeter • “Pressuremeter Test” presents the testing result for every depth in boreholes, which illustrates 03 curves: curve of “standard testing on sonde”, curve of “testing on ground” and curve of “difference time”. Union of Survey Companies (USCo.)


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• Pressuremeter Logs presents 02 main engineering parameters (P L & EP) in function of depth, along soil & tock columns. Two above parameters may be used for calculation of shallow foundation, pile foundation and pile subjected to lateral thrust. III.4

CRITERION OF SOIL & ROCK CLASSIFICATION

As mentioned above, based on geological map, there may identified two main zone of stratification within project area: 1) Covering Zone is formatted by Quaternary Deposit (included backfill), which includes two main geological formations: * Vinh Phuc Formation (ambQ III vp ) consists of clayey soil, sandy-gravely soils and organic soil. * Ha Noi Formation (apQ II-III hn ) consist silty-sandy gravel and pebble. 2) Bed rock Zone is formatted mainly by Hong Gai formation of Triassic System (K2 n-r hg 1,2 ), which consists of interbedding of claystone (included shale or coaly shale), silty claystone, silty sandstone, sandstone and conglomerate, and sometime quartzitic sandstone. This bedrocks have bee suffered various degree of weathering, from residual soil (grade V-VI) to fresh rock (grade I). However, in combination with geotechnical investigation result and for “geotechnical engineering purposes”, the stratification of project area site may shall be identified and classified by following principle: 1) For Covering Zone Based on Geological Stratification, the following strata may be identified and classified: a) Stratum number “1” is Made Ground. b) Stratum number “2” is cohesive soil. For “geotechnical engineering purposes”, stratum 2 shall be identified and classified into “geotechnical layers” based on its state: • Layer “2a”: Stiff to very stiff Clay (or silty Clay). Commonly, the SPT resistance includes: N30 = 8 – 30. • Layer “2b”: Soft to medium stiff Clay (or silty Clay) with little or no organic matter. Commonly, the SPT resistance includes: N30 = 2 – 7. • In case of mud of pound or river-bed, the geotechnical layer number “2c” is continued. c) Stratum number 3 is intermediate soils (clayey-silty Sand, sandy Clay, Sand intercalated clayey lenses). For “geotechnical engineering purposes”, stratum 3 shall be identified and classified into 02 “geotechnical layers” based on its state: • Layer “3a”: Loose to medium dense clayey Sand (with/no gravel). Commonly, the SPT resistance includes: N30 = 5 – 25. • Layer “3b”: Dense to very dense clayey Sand with Gravel (with/no cobble & rock fragments). Commonly, the SPT resistance includes: N 30 > 30. d) Stratum number “4” is Sand and Sand mixed Gravel & Cobble. For “geotechnical engineering purposes”, stratum 4 shall be identified and classified into 02 “geotechnical layers” based on its state: • Layer “4a”: Medium dense Sand (usually medium to coarse grains) with variable gravel and may be with some cobble or rock fragments. Commonly, the SPT resistance includes: N 30 < 30 (13-30). • Layer “4b”: Dense to very dense Sand (usually medium to coarse grains) mixed variable gravel and may be with some cobble or rock fragments. Commonly, the SPT resistance includes: N 30 > 30 (30 - >50). Union of Survey Companies (USCo.)


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e) Stratum number “5” is the second cohesive soil. For “geotechnical engineering purposes”, stratum 5 shall be identified and classified into single “geotechnical layer”, which is generally soft to medium stiff (firm) in state and with little (or no) organic matter and gravel. Commonly, the SPT resistance includes N 30 = 2 - 17. 2) For Bedrock Zone Based on Geological Stratification, the following strata may be identified and classified: a) Stratum number “6” is silty Claystone. For “geotechnical engineering purposes”, stratum 6 shall be identified and classified into following “geotechnical layers” based on its weathering jointing degree and state: • Layer “6a” is very stiff to hard residual silty Clay, which is product of completely weathered silty Clayestone & Claystone, becoming “clayey soil”. Conventionally the SPT resistance taken: N30 < 70 blows. • Layer “6b” is soft silty Claystone, which is product of highly to completely weathered silty Clayestone & Claystone, becoming very hard “clayey soil” but very soft “clayey rock”. Conventionally the SPT resistance taken: N 30 > 70 blows. • In cased of less weathering rock and more hard rorck encountered, the “geotechnical layer” number “6c” (or 6d) shall be continued. b) Stratum number “7” is silty Sandstone. For “geotechnical engineering purposes”, stratum 7 shall be identified and classified into following “geotechnical layers” based on its weathering jointing degree and state: • Layer “7a” is very compact residual silty Sand, which is product of completely weathered silty Sandstone, becoming “silty-sandy soil”. Conventionally the SPT resistance taken: N30 < 100 blows. • Layer “7b” is soft silty Sandstone, which is product of highly to completely weathered silty Sandstone becoming very dense sandy soil but very weal & broken “silty-sandy rock”. Conventionally the SPT resistance taken: N 30 > 100 blows. • In cased of less weathering rock and more hard rorck encountered, the “geotechnical layer” number “7c” (or 7d) shall be continued. III.5

SOIL AND ROCK DESCRIPTION & LAYERS DIVISION

Based on the site observation and soil identification in combination with the in-situ test and laboratory test, the description of “geotechnical layers” for soils and rocks from ground surface downward as follows: III.5.1 Covering Zone 1 of Quaternary Deposit (Q) Layer (1): Made ground (MG) consists of silty, sandy clay mixed gravel of rock fragments, grayish brown to bluish grey in color spotted black, instable in compaction state. This is backfill of “residual soil & weathered rocks” excavated from next hills and mountains. Made ground is encountered almost area of MPF with thickness varies from 0.3m to 1.4m. Layer 2a: Siff Clay (CL): This is cohesive soil of clay and silty clay, reddish brown-bluish grey– grayish iellow mottled in color, stiff to very stiff in state. Top layer is cultivated soil, so it’s usually blackish grey to bluish grey in color with little organic. Layer 2a is usually developed just from ground surface, sometime under soft organic clay 2b, with layer top encountered from 0.20m (CK62) to 1.3m (CK93) in depth and respectively thickness varies from 1.1m (CK62) to 6.5m (CK06), average about 4m . According to geological map, layer 2a may be in Vinh Phuc Formation (amQ III vp ). Union of Survey Companies (USCo.)


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Layer 2b: Soft to firm Clay (CL-CM): This is cohesive soil of clay and silty clay, blackish grey to grayish brown in color, soft to firm (medium stiff) in state. Sometime contained little organic and decay. Layer 2b is usually developed under layer 2a (sometime overlying); with layer top encountered from 1.7m (CK07) to 7.5m (CK64) in depth and respectively thickness varies from 1.0m (CK71) to 3.5m (CK43) . According to geological map, layer 2a may be in Vinh Phuc Formation (abQ III vp ). Layer 3a: Clayey Sand (SW-SC): This is intermediary soil of clayey Sand, ash grey to yellowish grey in color, loose to medium dense in state. Sometime contained some gravel. Layer 3a is developed under stratum 2 with layer top encountered from 1.2m (CK01) to 9.1m (CK80) in depth with variable thickness from 1.5m (CK87) to 4.0m (CK40). According to geological map, layer 3a may be in Vinh Phuc Formation (aQ III vp ). Layer 3b: Clayey Sand mixed Gravel (SC-SG): This is intermediary soil in nature of clayey Sand mixed Gravel, light grey to yellowish grey in color, dense to very dense in state, contained variably gravel, some cobble and rock fragments. Layer 3b developed jus under layer 3a, with layer top encountered from 5.0m (CK18) to 10.0m (CK93) in depth and respectively thickness varies from 2.9m (CK18) to 12.8m (CK51). According to geological map, layer 3b may be in Vinh Phuc Formation (aQIII vp ). Layer 4a: Medium dense Sand with Gravel (SP-SW): This is generally fine to medium Sand, light grey to yellowish grey in color, commonly medium dense in state, sometime contained gravel and grits. Stratums 4 is usually developed interbeddedly with stratum 3. The top of layer 4a is usually encountered in depth from 5.6m (CK22) to 10m (CK33) and respectively thickness varies from 2.3m (CK59) to 7.0m (CK22) . According to geological map, layer 5a may be in Ha Noi Formation (aQ II-III hn ). Layer 4b: Sand mixed Gravel (SW-SG): This is medium to coarse sand, ash grey to grayish brown in color, dense to very dense in state, contained variably gravel cobble and rock fragments. Layer top is encountered from 7.0m (CK65) to 12.1m (CK96) in depth and respectively thickness varies from 1.9m (CK26) to 17.2m (CK67). According to geological map, layer 5a may be in Ha Noi Formation (apQ II-III hn ). Layer 5: Soft to firm Clay (CL-CM): This is cohesive soil clay and silty clay , blackish grey to grayish brown in color, soft to firm (medium stiff) in state. Sometime contained little organic and decay. Layer 5 is usually overlying developed just upper lying bedrock with layer top encountered from 11m (CK79) to 14m (CK49) in depth with variable thickness from 1.0m (CK49) to 5.2m (CK22) . According to geological map, layer 2a may be in Vinh Phuc Formation (bQII-III hn ).

III.5.2 Bedrock Zone 2 of Triassic System (T2 n-r hg 1,2 )

Layer (6a): Residual silty Clay (W5,6-CMst): This is product of the completely weathered claystone silty claystone or siltstone becoming soil of silty clay , brownish grey to grayish yellow in color, stiff to very hard in state. Basically, residual clay (6a) may be identified with soft claystone by lower in soil state (30< N 30 <70).



11

Layer residual (6a) is usually developed at surface of bedrock silty-claystone, encountered at most boreholes with layer top encountered from 4.0m (CK13) to 19.5m (CK74) in depth with variable thickness from 3m (CK46) to 34m (CK22). Layer (6b): Soft Claystone (W4-6.Cst): This is highly to completely weathered Claystone and silty Claystone; thickly bedded no jointed so good coring (RQD > 80%); grayish brown spotted bluish gray in color. By its strength this material may be considered as but very soft rock but hard soil and core may be broken by hand. Generally, this layer 6b is identified with layer 6a by conventional N 30 > 70. Layer soft silty claystone (6b) developed almost project site and depth, usually under residual silty clay. The layer top encountered from 14.5m (CK45) to 29.8m (CK86) in depth with thickness tens meters. Layer (7a): Residual silty Sand (W5,6-SMst): This is product of the completely weathered silty sandstone and sandstone becoming residual silty sand with gravel and rock fragments ; light gray to ash grey in color, dense to very dense in state. During drilling, soil layer 7a was been disintegrated in silty Sand mixed gravel with some stone-pieces. The identification of residual soil (layer 7a) with broken silty sandstone (layer 7b) by conventional SPT resistance in ranged about 30< N 30 <100. Residual soil (7a) is usually developed intercalate with layer “6a” with variation in depths encountered and thickness. Layer (7b): Broken silty Sandstone (W4-5.CMst): This is highly to completely weathered sandstone and silty sandstone becoming very weak silty sandstone. The coring is usually broken and des-integrated in silty sand mixed gravel and rock fragments. The identification broken rock “7b” with residual soil “7a” by SPT resistance, where usually N30 > 100 for layer “7b” and N 30 < 100 for layer “7a”. This material may be considered as very soft rock mass but very compact soil. This broken silty sandstone is usually intercalatedly developed with layer “6b” with variable depth encountered and thickness. A typical cross-section along turbine hall-boiler-stack is illustrated on the figure 8.



12

Figure 8: Typical Cross-section along main “Power House & Stack”

III.6

ENGINEERING PROPERTIES OF SOIL AND ROCK LAYERS

The engineering properties of the geotechnical investigation for MPF are implemented by Laboratory Test and In-situ Tests of SPT and PMT. The in-situ test result is presented in boring logs and geotechnical cross-sections and the laboratory test result is shown in the appendices 2, 3, 4, 5, 6 and 9.



13

- For Laboratory Test on soil and rock, 251 soil & rock samples and 02 filling material were selected (by Kaidi’s Supervisor) for laboratory test. The detail testing result is shown in Appendices 4 & 9. Summarized representative engineering properties from laboratory test are shown in the table 3 (a & b). - In-situ Test of SPT carried out in all boreholes and the detail result is presented boring logs (Appendix 3), geotechnical cross-section (Appendix 2). Representative result of SPT resistance (N30) and deducted engineering parameters are summarized in the table 3. - Similarly, In-situ Test of PMT (Menard Pressurementer Test) was carried out in 03 boreholes within Main Power Plant (CK46.PR, CK80.PR, CK95.PR). Detail result of PMT is presented in Appendix 6 and representative values of P L & EP, and deducted engineering parameters for every soil and rock layer, are summarized in the table 3 (a & b).

Table 3a: Representative Engineering Properties of Soil & Rock Layers

No

Soil Engineering Parameters

Summarized Representative Engineering Parameters

Layer 2a

Layer 2b

Layer 3a

Layers 3b

Layer 4a

Layer 4b

SW-SP 12 98 0

SW-SG No sample Requested

Result of Laboratory Test

Soil Group Gravel > 4.25mm 1 Sand: 0.075 – 4.25 Finer < 0.075mm Moisture, W (%) 2 Number of tests Standard Deviation (STDEV) Bulk Density, γ (kN/m3) 3 Number of tests Standard Deviation (STDEV) Dry Density, γd (kN/m3) 4 Number of tests Standard Deviation (STDEV) Spec Gravity, γs (kN/m3) 5 Number of tests Standard Deviation (STDEV) Void Ratio e 6 Number of tests Standard Deviation (STDEV) Porosity n (%) 7 Number of tests Standard Deviation (STDEV) Saturation Sr (%) 8 Number of tests Standard Deviation (STDEV) Liquid Limit WL (%) 9 Number of tests Standard Deviation (STDEV) Plastic Limit WP (%) 10 Number of tests Standard Deviation (STDEV) Plastic Index, IP (%) 11 Number of tests Standard Deviation (STDEV) Liquid Index IL 12 Number of tests Standard Deviation (STDEV)

CL 1.0 41.5 57.5

CL-OL 0.5 51.3 48.2

SW-SC 4.7 69.1 26.2

SW-SG 7.0 69.5 23.5

23.3

31.7

19.4

19.1

62 2.3 19.9 56 0.4

16 0.5 18.8 11 0.9

10 1.9 20.5 7 3

7 1 20.5 6 0.2

16.1

14.5

17.3

17.2

56 0.6 27.2 62 0.04 0.690 56 0.063 40.7 56 2.1 91.8 56 2.3 44.3 62 2.1 22.8 62 0.8 21.6 62 1.9 0.019 31 0.115

11 1.4 27.0 16 0.1 0.891 11 0.19 46.4 11 5.1 93.2 11 3.0 43.2 16 4.3 23.5 16 1.1 19.7 16 3.5 0.41 16 0.23

7 4 27 11 1 0.568 7 0.036 36.2 7 1.4 88.9 7 2 31 10 5.4 20.6 10 1.6 11 10 4 -0.1 9 0.22

6 0.3 27.0 7 0.1 0.577 6 0.033 36.5 6 1.3 90.3 6 0.4 31.5 7 2.9 22.5 7 1.2 9.0 7 3.68 -0.47 7 0.3



26.0 1 -

14

13 16

Organic (%) Number of tests Standard Deviation (STDEV) Permeability k .10-5 (cm/s) Number of tests Standard Deviation (STDEV)

ϕ (deg) 17

18

No STDEV C (kPa) No STDEV

Direct Shear Test (DST)

ϕ’ (deg)

Triaxial Compression Test

No STDEV C’ (kPa) No STDEV

TCT – CD

ϕcu (deg) 19

No STDEV Ccu (kPa) No STDEV

Triaxial Compression Test TCT - CU

20

21

UCT, qu, (kPa) Number of tests Standard Deviation (STDEV) Pc (kPa) No STDEV Cc No. STDEV Odometer Cv (cm2/s) Compression No. Test STDEV (OTC) a1-2 (m2/KN) No. STDEV E01-2 kPa) No. STDEV

7.16 7 3.85

3.6 1 -

1.266 7 0.917

4.02 1 -

40.2 1 -

15059’ 18 0056’ 31.7 18 3.3

14039’ 3 0 1 13’ 29.7 3 4.4

13044’ 23 0044’ 30.2 23 0044’

8041’ 3 0 0 36’ 26 3 2.7

14026’ 3 0 0 9’ 26.5 3 3.6

10023’ 1 31.9 1 -

13041’ 23 0038’ 29 23 2.2

8005’ 3 0 0 50’ 24.8 3 3

13041’ 3 0 0 25’ 23.6 3 3.6

10002’ 1 30.4 1 -

85 17 7.6

72.5 5 11.5 120 3 19 0.14 3 0.038

78.5 1 -

51.4 1 -

0.00029 40 0.00003 5850 40 370

0.00041 8 0.00012 5000 8 900

0.00027 3 0.00002 5880 3 550

0.00025 1 6060 1 -

27.1 1 25015’ 1 11 1 -

RESULT OF SPT AND DEDUCTED ENGINEERING PROPERTIES

1 2

N30 (SPT)

ϕ (deg) deducted After

8 - 30

2-7

5÷ 25

30 ÷ 50

13 ÷ 30

30 ÷ 50

15

4

11

39

21

44

0

0

26 ÷ 35

36 ÷ 40

31 ÷ 36

36 ÷ 42

30

37

34

40

50.0 ÷ 187.5

13 ÷ 47

0

0

0

0

93.8

27

4200 ÷ 14800

2400 ÷ 3900

3900 ÷ 14900

20200 ÷ 29200

17300 ÷ 29200

40000 ÷ 60000

10300

3000

6000

24300

22900

54000

Terxaghi & Peck 3 4

C (kPa). Deducted After Sower E1-2 (kPa) deducted After Anagnostapoulos



15

ESTIMATED BEARING CAPACITY using SPT DATA (N30)

1

ESTIMATED RESULT OF SHALLOW FOUNDAITON B = D After CP 2004 – 72 (United Kingdom) 80 – 300 < 70 50 – 250 300 – 500 150 110 400

Allowable Resistance Ru (kPa) for Fs = 3

130 – 300 210

300 – 600 450

ESTIMATED RESULT OF PILE FOUNDAITON After Mayerhof, Martin, Decourt’s Experiences for Pile

1

2

Allowable Point Resistance, qa (kPa) with Fs = 3 Allowable Skin Friction, f a (kPa) with Fs = 2

Driven Pile Bored Pile Driven Pile Bored Pile

533 - 2000

133 - 467

583 - 2917

3500 - 5833

1867 - 4000

4500 - 7500

1000

267

1283

4550

2800

6600

533 - 2000

133 - 467

250 - 1250

1500 - 2500

650 - 1500

1500 - 2500

1000

267

550

1950

1050

2200

18 - 55

8 - 17

20 - 40

45 - 65

28 - 45

45 - 65

30

12

26

54

36

59

8 - 30

2-7

4 - 19

23 - 38

10 - 23

23 - 38

15

4

11

29

16

41

RESULT OF PRESSUREMENTER & ESTIMATED BEARING CAPACITY After FOND.73, Chapter 5.2 & F.62 (France)

1 2

3

4

5

440 ÷ 1010

Limit Pressure PL (kN/m2) Menard Modulus EP (kPa)

703

3500÷9900

370 ÷ 1090

-

2300÷5700

730

1450

20100 6700 4000 ESTIMATED RESULT OF SHALLOW FOUNDAITON

Allowable Resistance Ra (kPa) for Fs = 3 Allowable Point Resistance, qa (kPa) with Fs = 3 Allowable Skin Friction, f a (kPa) with Fs = 2

No Representative


147÷337

-

123÷363

483 234 243 ESTIMATED RESULT OF PILE FOUNDAITON 264÷606 456÷1344 1788 422 900 176÷404 148÷436 580 328 292 16÷30 16÷41 49 23 30 10÷30 9÷19 20 23 15

820÷ 1230

1400÷1420

1075 9900÷13700

1410 13600÷10500

11800

12050

273÷410

467÷473

358

470

1011÷1517

1727÷1751

1326

1739

328÷492

560÷568

573

564

33÷45

48÷49

41

49

16÷19

20÷20

18

20

Table 3b: Representative Engineering Properties of Soil & Rock Layers (continued)

No

Soil Engineering Parameters

Summarized Representative Engineering Parameters

Layer 5

Layer 6a

Layer 6b

Layers 7a

Layer 7b

0 39.5 60.5

SC Re.SMst 13.1 70.4 16.5

SC W4-5.SMst 0 68.5 31.5

Result of Laboratory Test

Soil Group 1 2 3

CL-OL

Gravel > 4.25mm Sand: 0.075 – 4.25 Finer < 0.075mm Moisture, W (%) Number of tests Standard Deviation (STDEV) Bulk Density, γ (kN/m3) Number of tests

0.4 46.8 52.8

CL (Re.CMst) 0.3 36 63.7

CL

29.6

20.0

19.0

22.5

18.3

28 3.7 19.0 25

33 2.0 20.4 32

85 1.0 20.5 83

3 6.1 20 3

3 0.7 20.7 3

(W4-5.CMst)



16

4 5 6 7 8 9 10 11 12 13 16

Standard Deviation (STDEV) Dry Density, γd (kN/m3) Number of tests Standard Deviation (STDEV) Spec Gravity, γs (kN/m3) Number of tests Standard Deviation (STDEV) Void Ratio e Number of tests Standard Deviation (STDEV) Porosity n (%) Number of tests Standard Deviation (STDEV) Saturation Sr (%) Number of tests Standard Deviation (STDEV) Liquid Limit WL (%) Number of tests Standard Deviation (STDEV) Plastic Limit WP (%) Number of tests Standard Deviation (STDEV) Plastic Index, IP (%) Number of tests Standard Deviation (STDEV) Liquid Index IL Number of tests Standard Deviation (STDEV) Organic (%) Number of tests Standard Deviation (STDEV) Permeability k .10-5 (cm/s) Number of tests Standard Deviation (STDEV)

ϕ (deg) 17

18

Direct Shear Test (DST)

Triaxial Compression Test TCT – CD

No STDEV C (kPa) No STDEV

ϕ’ (deg) No STDEV C’ (kPa) No STDEV

ϕcu (deg) 19

Triaxial Compression Test TCT - CU

20

No STDEV Ccu (kPa) No STDEV

UCT, qu, (kPa) Number of tests

0.5

0.3

0.2

0.7

0.1

14.7

17.1

17.3

12.3

17.5

25 0.8 27.1 28 0.1 0.851 25 0.099 45.7 25 3.0 93.6 25 2.6 42.6 28 2.7 23.0 28 0.9 19.6 28 3.3 0.33 28 0.18 3.21 8 0.94

32 0.4 27.2 33 0.1 0.597 32 0.044 37.2 32 1.6 90.3 32 2.4 45.7 33 1.6 23.3 33 0.9 22.4 33 1.1 -0.14 33 0.10

83 0.4 27.2 85 0.1 0.576 83 0.036 36.5 83 1.4 89.6 83 2.0 45.0 85 2.1 23.3 85 1.1 21.7 85 1.6 -0.2 85 0.09 3.3 1 -

3 0.2 26.9 4 0.2 0.660 3 0.152 39.2 3 5.2 91.1 3 4.4 32.4 3 5.4 22.6 3 2.0 9.8 3 4.4 -0.26 3 0.56

3 0.2 27.0 3 0.1 0.548 3 0.017 35.4 3 0.7 90.3 3 1.5 38.6 3 4.4 24 3 1.3 14.5 3 5.1 -0.55 3 0.33

1.02 1 -

1.637 7 1.316

1.003 25 0.374

12058’ 7 2049’ 28.1 7 3.3

15038’ 13 0056’ 32.8 13 1.5

16000’ 46 1017’ 32.2 46 2.4

16032’ 1 25.0 1 -

18051’ 2 3058’ 23.0 2 13

12010’ 13 0017’ 29.3 13 3.8

13059’ 8 0 0 44’ 31.6 8 1.6

14009’ 9 0 0 41’ 33 9 0.5

19007’ 1 13.1 1 -

11038’ 13 1037’ 27.2 13 4.1

13052’ 8 0 0 40’ 29.0 8 1.5

13041’ 9 0 0 41’ 30.4 9 0.6

18018’ 1 9.1 1 -

76.4 8

91.3 8

89.7 37

67.6 2



17

21

Standard Deviation (STDEV) Pc (kPa) No STDEV Cc No. STDEV Cv (cm2/s) Odometer No. Compression STDEV Test (OTC) a1-2 (m2/KN) No. STDEV E01-2 (kPa) No. STDEV

9.2 125.8 4 12.1 0.132 4 0.02 0.952 4 0.024 0.00036 19 0.00004 5400 19 540

2.3

5

13.8

0.00026 16 0.00002 6070 16 360

0.00026 52 0.00002 6120 52 340

0.00029 3 0.00006 5820 3 650

0.00025 1 6190 1 -

RESULT OF SPT AND DEDUCTED ENGINEERING PROPERTIES

1 2

N30 (SPT)

ϕ (deg) deducted After

3 ÷ 17

21 ÷ 70

6

48

> 100

47

> 100

0

No correlation No correlation No correlation




Terxaghi & Peck 3 4

C (kPa). Deducted After Sower E1-2 (kPa) deducted After Anagnostapoulos

18.8 ÷ 106.3 37.5

2700 ÷ 10900 3600

16÷ 75

ESTIMATED BEARING CAPACITY using SPT DATA (N30)

1

Allowable Resistance Ru (kPa) for Fs = 3

ESTIMATED RESULT OF SHALLOW FOUNDAITON B = D After CP 2004 – 72 (United Kingdom) 37 – 210 21 – 500 160 – 500 75 400 600 400

600

ESTIMATED RESULT OF PILE FOUNDAITON After Mayerhof, Martin, Decourt’s Experiences for Pile

1

2



200 - 1133

1400 - 3333

400

3200

200 - 1133

1400 - 3333

400

3200

10 - 33

40 - 88

15

84

3 - 17

21 - 50

6

48

1333 - 4167 3333

3917

4167

800 - 2500 2500

2350

2500

31 - 65 88

62

65

12 - 38 50

35

38

RESULT OF PRESSUREMENTER & ESTIMATED BEARING CAPACITY (After FOND.72, Chapitre 5.2 & Fascicule 62 - France)

1 2

Limit Pressure PL (kN/m2) Menard Modulus EP (kPa)

780 - 870 825

1600 - 2780 1720

5500 - 6500 6000

16300-39500 9600

No Testing

2504

2320 – 2770 2473

No Testing

28300

2330 – 38100 29933

ESTIMATED RESULT OF SHALLOW FOUNDAITON

3

Allowable Resistance Ra (kPa) for Fs = 3

260÷290 275

573

533÷927 835

773÷923 No Result



824

18

ESTIMATED RESULT OF PILE FOUNDAITON

4

5

III.7



468÷522 495

1333÷2317 1032 688 39

No Result

40

39

40

1237

60÷60 No Result

38÷40

25 - 27 26

1252

2638

1165 - 1385

38÷40

25 - 27 26

2485÷2955 No Result

148÷436

312 - 348 385

900

60

40÷40 No Result

40

GROUND WATER CONDITION III.7.1

Groundwater Level Recording in Boreholes

Ground water level was recorded in boreholes during drilling and the result is shown in “Record of Boring Logs” (see Appendix 3) and “Geotechnical Cross Section” (see Appendix 2). Generally, the groundwater level measured in boreholes during drilling varies from 2.15m to 3.13m, which may be mainly contained in granular soils (layers 3a, 3b, 3c and 4a, 4b). The accurate ground water level have been determined in boreholes CK02, CK59 and CK81, where casing protection and wash pumping carried out for groundwater recording and sampling. The first recording data of groundwater depth, measured at 8h 27 November 2009, are shown: 3.76m (in CK02); 3.41m (in CK59) and 3.50m (in CK81). III.7.2

Result of Chemical Analysis of Groundwater

02 water samples taken from Cam River and 03 groundwater samples recovered in boreholes (CK02, CK59 and CK81) for chemical analysis in Laboratory. The detail result of chemical components of groundwater is shown in the Ap pendix 5 and summarized main corrosive components and corrosion appraisal for building material are presented in the table 4. Table 4: Summarized Result of Chemical Analysis of Groundwater & Judgment of Corrosion to Building Materials

Components Ca2+ pH N+, K+ Mg 2+ Ca2+ pH N+, K+ Mg 2+

According to BS 8004-1986

Chemical Analysis Result of Main Components Unity Value range Components Unity Goundwater in Boreholes mg / lít 16.03 mgЗ / lit HCO3 – 2 7.05 - 7.15 SO4 Mg / lit mg / lít 9.6 - 54.87 CL Mg / lit mg / lít 9.73 CO2 (free) Mg / lit Surface Water from Cam River mg / lít 16.03 mgЗ / lit HCO3 – 2 7.45 - 7.50 SO4 mg / lit mg / lít 15.82-16.53 CL mg / lit mg / lít 9.73 CO2 (free) mg / lit

Value range 0.6 – 2.4 10.5 – 35 26.23 13.2 - 26.4 1.8 14.0 – 15.5 26.23 8.6 – 13.2

Corrosion Assessment to Building Material No corrosive to Ordinary Portland Cement (OPC). Rigid Hardening Portland Cement (RHPC). Portland Blastfurnace pH > 5 Cement (PBFC). No Corrosive to Ordinary Portland Cement (OPC). Rigid 2hardening Portland Cement (RHPC). Portland Blast furnace SO4 < 300 mg/L Cement (PBFC).



19

pH > 6.5 2-

According to CHuΠ II.28.74 (Russia)

SO4 < 300 mg/L (CL- < 1000) HCO3 = 0.6 < 0.7 mgЭ/L CO2 (free) = 26 > a[Ca2+] + b = 22.6 Mg 2+ < 1000 mg/L (Na+ + K+) < 50 g/L

III.8

No corrosive to “Normal Building Concrete” No corrosive to “Normal Building Concrete” with Normal Portland cement (NPC), Portland-Pusoland Cement (PPC) and Portland Cement with Slag (PCS) “Moderately corrosive” with “Normal Building Concrete”. But no corrosive with “Dense Building Concrete” “Slightly corrosive” with “Normal Building Concrete” But no corrosive with “Dense Building Concrete” No corrosive to “Normal Building Concrete” No corrosive to “Normal Building Concrete”

EMBANKMENT MATERIAL

The project site is fairly high-land and the embankment is constructed for un-smooth ground surface. The plan site has been already filled up before time of site investigation. The filling material is residual soil extracted from next hills & mountains which consists of silty clay mixed gravel and pebble of weathered rock fragments. The embankment was not compacted as standard, but freely filled up, so its is denser next to ground surface and looser at embankment’s bottom, natural soil is organic clay of cultivated soil. Some samples of embankment material have been recovered for Soil Compaction Test in using of 2.5 kg in ram weight, 30.48mm in falling height, 2118.8 cm 3 in mould volume (modified mould). Detail testing result of prepared sample from made ground is presented in Appendices 4 & 9 and summarized result of soil compaction test is follows: - Maximum Dry Density γdmax = 17.4 – 17.6 kN/m3 - Optimal Moisture Content Wopt = 16.0 – 16.7 % Comment & Recommendation 1:

1) The values of engineering properties of clayey Sand stratum 3 (3a & 3b) as shown in “ Table 3 ”, are representative for “clayey soil” part only, which were recovered as undisturbed samples. However, the principal part of stratum 3 is “sandy soil”, even mixed gravel or cobble, so no undisturbed samples recovered unless disturbed samples taken from SPT’s sampler. Therefore, the representative engineering properties for foundation calculation taken from In-situ Tests (SPT & PMT) shall be more representative. Above situation is the same applied for layers 7a and 7b. 2) The values of PMT engineering parameters presented in “ Table 3 ” (P L, E P ) from layers 2b (soft to medium stiff Clay with little organic matter) seems to be not good compatible with SPT’s result and it seems to be “fewer representative” for this layer. The reason may be the testing layer is too thin (CK46.PR) while the “measurement probe”’ is long, so the “measuring sonde” may not be really posited in “soft part of soil” and may be in stiff part. Otherwise, only 3 or 4 locations of PMT were requested to be carried out, so the values must be “fewer representatives” for all geotechnical layers. 3) The values of SPT’s engineering parameters presented in “ Table 3 ” (N 30 & deducted parameters) are “more representative” for Quaternary deposit (strata 2, 3, 5 & 5), because they are quite compatible with Laboratory Test on soil samples. However, for the “residual soils” and “weathered soft rocks” (from strata 6 & 7), the SPT’s resistance is less compatible with Laboratory Test result on samples. The reason may be explicable by variation in weathering degree and in-place in deposition, which are always manifested specially characteristic in comparing with transported deposition. In reality, both SPT and Laboratory Test for residual soil & weathered soft rocks are “fewer representative”, so the “prudence” must be taken in calculation. In this case the pressuremeter test seems to be more reliable.



20

IV IV.1

GEOPHYSICAL EXPLORATION EARTH RESISTIVITY SOUNDING METHOD (ERM) IV.1.1 Principle of Sounding Method

The principle of method is simple of a system of electrodes, as illustrated in f igure 9, which used to measure the apparent resistivity of ground. A current is passed through the ground between ‘current electrodes’ (A, B) and the potential drop between ‘voltage electrodes’ (M, N) is measured. Usually all four electrodes are spaced evenly apart and by altering of the spacing ‘L’, the “apparent resistivity” of the ground will change, depending of ground condition, and a plot can be obtained of apparent resistivity against electrodes spacing. This is then matched against standard curves of idealized condition. However, the result interpretation needs the skill and experience person Th¨m dß ®Þa vËt lý b»ng ph − ¬ng ph¸p ®iÖn tr −ê ng and the reference with boring is required. This technique may provide an inexpensive investigation Figure 9: Electric Sounding at Site method for simple ground condition and it uses to detect with both horizontal and vertical variation in ground condition. There are two methods for arrangement of the electrodes, which may apply for various investigation purposes: After Wenner’s

:

P2

C1 a

C2

a

a

ρa = 2 π a R N

M

A

After Schlumberger’s:

(1) B

l

l

L

ρa =

π (L2 − l 2 ) 2. l

xR

(2)

IV.1.2 Result of Earth Resistivity Measurement In order to determine earth receptivity within shallow depth of project, 11 survey lines were arranged in direction E-W with singed T1 to T11 and 172 measurement points were operated. The spacing of lines varies about 30m to 70m and the spacing of points varies about 20m t0 30m. Equipment used is digital electrical instrument IPR-12 (made in Canada). The measuring apparent resistivity, ρa (oh-m), were analyzed by Software RESIXIP 2DIV4 manufactured by INTERPREX Firm (USA). Detail result is presentation in Appendix 7 and summarized result is shown in the table 5. Table 5: Summarized result of earth receptivity measurement Depth (m)

Range of Receptivity, ρa (oh-m) Union of Survey Companies (USCo.)


Soil Type

21

IV.2

From ground surface to 2m

184 – 714

Made ground & Stiff Clay

From 2m to 5m

115 - 4900

Stiff Clay

From 5m to 7m

98 – 472

Silty Clay & Silty Sand

SEISMIC DOWN-HOLE SOUNDING METHOD (SDM) IV.2.1 Principle of Sounding Method

The seismic down-hole method is ‘economic alternative’ to cross-hole testing (see figure 10). It needs only one borehole inside with the receivers is placed at various depths, while the Lateral source is at surface, 2 to 5m away. Impact Travel-time of body waves (S or P) Geophone between surface and receiver (s) are recorded, and then travel-time versus depth plots are constructed from which Vs or Vp of all layers can be determined. Wave path An effective and economic S-wave source consists of a steel-jacked rigid beam weighted down the ground and struck horizontally with the Transducer sledge-hammer. However, if the source is place too close to the borehole, parasitic waves are created and S-wave arrivals cannot be easy identified. In reverse if it’s too far from the source, the direct Figure 10: Sketch of Seismic Down-hole wave path may not be straight line. These problems are largely avoided by seismic crosshole method (SCM). IV.2.2 Result of Wave Velocity Measurement The seismicity measured by down-holes were operated in 05 boreholes ( CK13, CK 17CK 64, CK67 and CK72) with depths from 30m to 60m and total 200 observation points. The sounding procedure, presentation and interpretation result are in accordance to “The Guide of Geophysical Exploration in Suevey for Engineering and Environment” and the equipment used is recording station of Strata Visor NZII-48 manufactured by Geometric (USA). Detail survey result of seismic down-hole test is shown in Appendix 8. Equipment used is Strata-Visor-NZ made in Geometrics (USA) with sample step 125 μs. The elastic properties of soil and rock shall be determined in using wave’s velocity as follows: G = ρ Vs2

(3)

E = 2 (1+ ν).G

(4)

ν = Where:

0 ,5 . ( V p / V s ) 2 (Vp / Vs )

2

−1

−1

(5)

E : Elastic modulus, G : Shear modulus ν : Poison coefficient, Union of Survey Companies (USCo.)


22

ρ : Bulk density. The seismic wave velocity and deducted engineering properties of soil and rock layers are summarized in Table 6: Table 6: Representative Seismic Parameters and Deducted Engineering Properties Soil & Rock Layer

ρ

3

kN/m

Vp m/s

Vs m/s

E Mpa

G Mpa

ν

Covering Zone of Quanternary Deposit Made Ground: Silty Clayey mixe

18

474

231

2574.14

960.50

0.34

19.9

1031

249

3627.43

1233.82

0.47

18.8

742

177

1731.63

588.99

0.47

rock fragements Layer 2a: (N30 = 8 – 30/ 15)

Stiff to very stiff Clay Layer 2b: (N30 = 2 - 7/ 4) Sof to firm Clay. Layer 3a: (N30 = 5 - 25/ 11) Loose to medium dense clayey Sand Layer 3b : (N30 = 30 - >50/ 39) Clayey Sand mixed gravel & cobble. Layer 4a : (N30 = 13 - 30/ 21) Fine to medium Sand Layer 4b: (N30 = 30 - >50/ 44) Medium to coarse Sand Layer 5: (N30 = 3 - 17/ 6) Soft to stiff Clayl.

0.47 18.5

902

211

2421.50

823.64

1277

292

4762.86

1620.02

0.47

19

1095

244

3325.67

1131.18

0.47

19

1303

296

4894.22

1664.70

0.47

19

948

193

2094.88

707.73

0.48

19

Bedrock Zone of Weathered Silty Claystone & Silty Sandstone Stratum 6a: (N30 = 21 – 70 / 48)

Residual silty Claystone Stratum 6b: (N30 > 100) Soft silty Clayeystone Stratum 7a: (N30 = 26 - 75 / 47) Residual silty Sand Stratum 7b: (N30 > 100) Broken silty Sandstone

20.4

1742

440

11610.06

3949.44

0.47

20.5

1921

522

16308.20

5585.92

0.46

20.0

1595

378

8779.66

2986.28

0.47

20.7

1678

409

10180.40

3462.72

0.47



23

a Drillin & Sam lin

d Undisturbed & Core Sam les

d) Menard Pressuremeter Test

e) Seismic Down-hole Sounding

f) Groundwater Measurement Well

g) Off-shore Drilling

b) Standard Penetration Testing

f) Earth-resistivity Survey

h) Filling Material Sampling

Figure 11: Some Figures of Subground Investigation at Project Area



24

V

GEOTECHNICAL & FOUNDATION ENGINEERING ANALYSIS

V.1

PRINCIPAL MATTERS FOR GEOTECHNICAL ANALYSIS V.1.1 Foundation Analysis for Main Building Structures

There are various components within Main Power Plant area (MPF), from which the most heavy and important structures are the turbine hall, boiler, stack, heavy oil storage tank… The other shall be medium to light structures. Therefore, the foundation problems of building structure in MPF area shall be consecutively analyzed as follows: - Firstly is to analyze shallow foundation founded direct on natural soil for typical subground condition. Generally, different footing sizes and raft foundation are usually taken in computation for various scales of structures. - Secondly to analyze pile foundation penetrated to good bearing layers and from its order, the various foundation types (driven, bored…) and sizes shall be taken in computation. - Finally, the appropriate foundation type & size selected for every structure scale is implemented by principle for safe in bearing capacity for foundation supported superstructure and acceptable for structural and foundation displacement. V.1.2 Stability Analysis for Main Earth Structure The most important Earth-structure in the Thermal Power Plant is Coal Yard, where dimension of stockpile may attain: B = 20 – 35m, L = 140m, H = 10 – 20m, γ = 16 kN/m2 V.2

ANALYSIS OF SHALLOW FOUNDATION

Shallow foundation founded directly on natural soil is usually applied following types: isolated footing, continued-footing with tie-beams and raft foundation. In calculation of shallow foundation shown that they are satisfied two main below conditions, the application of shallow foundation shall always be the most simple and economic: - Safety in bearing capacity of ground (qa ≥ PST), and - Acceptable in displacement (St ≤ SghST, ΔS ≤ ΔSghST), V.2.1 Calculation Method a) Theoretical Soil-mechanic Method In this sub-ground condition and superstructure, the theoretical soil-mechanic method applied is suitable and the Caquot-Kerisel and Terxaghi’s methods are commonly used in many design codes – included in DTU.13.1 - France [8, 2] - with the main expressions:

=

Resistance:

qa

Settlement:

St =

1 Fs

Σ

⋅[

B 2(1 + B/L)

σ i .h i E oi

γ N . γ

= Σ hi

+ q'o .(Nq − 1) + (1 + 0.3

C ci 1 + e 0i

log(

Δ σ zi + P0zi Pci

B L

).C.N c ]

)

(6) (7)

b) Menard Pressuremeter Method



25

Based on Menard’s theory, the calculated of shallow foundation in using of PMT’s parameters shall be in accordance to Menard’s regles (D.60) or FOND.72 (LPC) or France’s Codes F62, which are described in “Geotechnical Engineer’s Handbook” [2], the following main expressions shall be applied: qp = kp. PLe PLe = St =

b + 3a 3E p

kp.PLe + γ D Fs(2 − 3)

Log PL

D

B 1,5B

(8)

D + 3a

1

1 + ν

qa =

PLe

∫ P (z). dz

(9)

L

D− α

⎛ R ⎞ α ⎟⎟ + q.R 0 ⎜⎜ λ 2 . .q.λ 3 .R R 4,5.E 0 ⎠ p ⎝

(10)

Figure 12: Calculation of Shallow Foundation using PMT method

V.2.2 Calculation Result All required design parameters introduced in a computer program of “shallow foundation calculation” as follows: - Conventional footing dimensions: B = 2m with B/L ratio = 1, 2, 3, 5, 10 and D = 2.0m. - Conventional raft-foundation with dimension: B x L x D = 30m x 40m x 2.0m. - Foundation base founded right on stiff clay (2a) with sub-ground condition of boreholes CK46 & CK.46.PR and engineering parameters presented in tables 2 and 3, a) Result of Classical Method A Computer program used with input data as mentioned above and the calculation result is shown in the table 7. Table 7: Result of Shallow Foundation Analysis using Classical Method



26

b) Result of Pressuremeter Method Similarly, a computer program used with input data as mentioned above and the calculation result is shown in the table 8. Table 8: Result of Shallow Foundation Analysis using PMT Method

Comment & Recommendation 2:

•

For conventional shallow footings (B = 2m, L/B = 1, 2, 3, 5, 10) founded right upon stiff clay layer 2a (D = 2m) may provide: + Allowable resistance under foundation base shall be: qa = 190 kPa (Classical Method), and qa = 255 kPa (Pressurementer Method). + Respectively, the expected settlement under net applied pressure (P n = q a - P o) may reach: St = 2.8 – 3.6 cm (Classical Method), and St = 1.6 – 2.3 cm (Pressurementer Method).

•

For a conventional raft foundation (B = 30m, L = 30m) founded right upon stiff clay layer 2a (D = 2m) may provide: + Allowable resistance under foundation base shall be: qa = 292 kPa (Classical Method) + Respectively, the expected settlement under net applied pressure (P n = q a - P o) may reach: St = 2.8 cm (Pn = 100kPa); = 5.7 cm (Pn = 200kPa); = 8.5cm (Pn = 300kPa)



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V.3

ANALYSIS OF PILE FOUNDATION

Pile foundation must be applied when the shallow foundation was not acceptable. Depending of the sub-ground condition and superstructure, the selection of the appropriate pile type, sizes and bearing layers for an adequate design bearing capacity are required. V.3.1 Calculation Method for Pile Foundation General formulas for pile foundation include:

QP

+

QF

+

f S .A S

Qa =

Bearing capacity of material:

Qm = AP.f’C.αC

(12)

Selected design load:

Q w ≤ Min ( Qa , Qm)

(13)

FS1

=

q P .A P

Bearing capacity of ground:

FS2

FS1

FS1

(11)

The determination of unit point-resistance (q p) and unit shaft friction (f s) of pile may be calculated by following methods: 1) Meyerhof’s Method using SPT resistance (N30) When pile founded in soils (especially coarse grains soil or highly weathered rock where no undisturbed samples recovered) the Meyerhof’s method [5, 2] using of N30(SPT) is suitable and commonly applicable (included in TCVN 205:1998). However, it should be in combination with the experiences of Martin’s, Decourt’s, Shoiu-Fukui’s, Yamashita for various pile and soil types. The main calculation expressions as follows: qp = Kp.N30

Lb n.B

≤ qL (Kp.N30)

(14)

f s = α + β.N30

(15)

2) Menard’s Method using Pressuremeter Data (PL , EP) For granular soil and weathered rock where the undisturbed samples are impossibly recovered for laboratory testing, the pressuremeter test (PMT) is the most adequate. In calculation of shallow foundation (in using PMT) the following expressions may be applied in accordance to France’s norms [2, 6, 7] D60, FOND.52 Chapitre 5.2 and F60: qp = kp. PLe

PL

D Lb

PLe

De b

(16) 3a

Where: pLe =

D + 3a

1 b + 3a

f s = q sn .

PL Pn

∫ P (z). dz

(17)

L

z

D−

⎛ PL ⎜2 − ⎟ ⎝ Pn ⎠

with

PL Pn

≤1

(18)

Figure 13: Pile Foundation using PMT

3) Method of Pile Calculation for Rock There are various methods for calculation of pile foundation founded in rock. However, the Ladanyi & Roy’s method (1974) [12, 2] may be suitable for a fairly good jointed-weathered Union of Survey Companies (USCo.)


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rock in using 03 parameters: compressive strength (q u), joint spacing (s), aperture ( δ) and including the socket condition (K sp, d). The main expressions of method are follows: Qa = qa Ap and Ksp =

qa = qu.Ksp.d

3+ s/ B 10. 1 + 300.δ / s

(19) (20)

4) Method for Settlement of Pile The settlement of single pile shall be calculated after Woodward, Gardner & Greer‘s Method [12; 2] and pile group settlement shall be calculated in according to Skempton’s or Vesic‘s empirical methods [12, 2]. Similarly, negative skin friction of pile uses the method described in FOND-72 (LCPC) [6, 2]. V.3.2 Analysis of Driven Pile Driven pile is one of the commonly used in pile foundation, which is usually effective for moderate structure, caused by its advantages: + Facile in piling work, which is traditionally and commonly used techniques, equipments and procedure for long time. + Quick in piling work and it’s reasonable in cost price. + Easily in controlling of pile material and piling work and driven pile makes densification of surrounding soil, so it’s bearing mobilization is usually overestimated. However, driven pile foundation may present some its limitations: + Limited in pile sizes and difficult in penetration through hard lenses, so the mobilization possibility of pile bearing capacity is limited. + Difficult socket in sloping layer of hard soil or rock that is susceptible in failure or slipping of pile, especially pile penetrated through thick soft clay overlain. + Vibration produced during piling that may damage the surrounding structures. In overcoming of vibration from driven piles, the compressed pile (jacked piles) is usually used within city area. V.3.3 Analysis of Bored Pile In dealing with important and heavy structure, cast in place bored pile is commonly used because of advantages: + Pile diameter may be widened as required (may be reached to 2m or more), may be deeply penetrated (down to 50/70m or more) and may be penetrated through rock, even sound rock. + Therefore, it may mobilize high to very high bearing capacity (thousand tons/pile or more). + Piling work shall not make vibration and may be carried out at many site conditions. However, bored pile may be manifested the limitations: + Complicated and sophistic in equipments, techniques, materials and piling technology that lead to high price cost. Therefore, bored pile is un-suitable for small projects. + Difficulty in control of piling and concreting quality, especially flushing-out and clearance of slurry settled at holes-end before concreting and uniformity of concrete. Some recent checking shown that the poor concrete or slurry-concrete mixture is discovered about 0.5m to 1.5m from end of bored piles. V.3.4 Calculation Result of Pile Foundation Generally, the thickness of foundation-cap may vary about 2 - 3m, so foundation-cap may be founded right on stiff clay (2a) or on sandy clay (3a) or dense sand with gravel 3b, 3c. Because of thin soft organic clay is usually just overlying upon granular soil stratum (5) or soft rocks, so he pile-tips must be deeply penetrated in such soft rocks (layer 6b or 7b). A typical “soil-pile modeling” of “main power house & stack” is presented in the figure 14.



29

Figure 14: Soil-structure model of pile foundation



30

1) Calculation Result of Driven Pile a) Selection of Parameters:

• •

•

03 sizes in section: a x b = 0.3m x 0.3m; 0.4 x 0.4m; 0.5 x 0.5m. Pile depth must be penetrated in dense sand mixed gravel (N ≥ = 30) and embedded in under soft rock surface about 0.5m with conventional N 30 = 50. Therefore, the conventional depth for driven pile is 17m, but the actual depths shall be changed from position to position due to variation of rock surface. Conventional borehole CK70 with its SPT resistance (N 30) is selected for classical method and boreholes CK.46.PR is selected for PMT method.

b) Computation Result of Driven Pile A computer program for “Pile Foundation Analysis” is established for calculation. The result of SPT method is shown in the table 9a and result of PMT method is shown in the table 9b. Table 9a: Calculation Result of Driven Pile using SPT Method

Table 9b: Calculation Result of Driven Pile using PMT Method



31

Comment & Recommendation 3: 1) In referring to driven pile with pile-sizes: 0.3; 0.4; 0.5m and embedded about 0.5m in soft rock (6a, 6b, 7a, 7b), the following “design bearing parameters” may be referenced for design study: a) Working design load of a pile:

• •

For SPT Method: Qw = 800 kN (Pile 0.3m); Qw = 1200 kN (Pile 0.4m); Q w = 1700 kN (Pile 0.5m). For PMT Method: Qw = 720 kN (Pile 0.3m); Qw = 1000 kN (Pile 0.4m); Qw = 1300 kN (Pile 0.5m).

b) Expected settlement of single pile under design load:

•

For SPT Method: Si = 3.7mm (Pile 0.3m); Si = 4.3mm (Pile 0.4m); Si = 5.0mm (Pile 0.5m). • For PMT Method: Si = 2.7mm (Pile 0.3m); Si = 2.7mm (Pile 0.4m); Si = 3.0mm (Pile 0.5m). However, the settlement of pile group is higher depending of group dimension. 2) Basically, result of pile foundation calculated by both SPT & PMT methods are quite agreement. However, above values are typical representative for location of CK.46. The sub-ground condition and the surface depth of soft bed-rock are varied from location to location (about from 15m to 18m), so the actual pile depth (or length) shall be varied accordingly. 2) Calculation Result of Bored Pile

a) Selection calculation parameters

• •

Diameters of pile for computation shall be selected conventionally 03 sizes: Ф0.8m, Ф1.0m, Ф1.2m. Pile penetrated in soft rocks as bearing layer (6b or 7b) with conventional 02 embedment length: Lp1 = 5m and Lb2 = 10m.



32

•

Representative location for calculation is borehole CK46 using for SPT method, on which the N30 resistance is conventionally taken maximum 50 for both soft silty claystone (6b) and weak silty sandstone (7b). For PMT method, the pressuremeter log of CK.46.PR is selected for typical calculation.

b) Computation Result A computer program for “Pile Foundation Analysis” used for calculation and the result of SPT method is shown in the table 10a and result of PMT method is shown in the table 10b. Table 10a: Calculation Result of Bored Pile using SPT Method



33

Table 10b: Calculation Result of Bored Pile using PMT Method

Comment & Recommendation 4 : 1)

In referring to bored pile with pile-diameters: Ф0.8m, Ф1.0m, Ф1.2m, embedded about from 5m to 10m in soft silty claystone (6b) or weak silty sandstone (7b), may mobilize following design parameters: c) Working design load of a pile:

•

For SPT Method (conventionally taken max-value of N 30 = 50): + Embedded 5m in 6b: Q w = 2750 kN (Ф0.8m); Qw = 3840 kN (Ф1.0m); Qw = 5080 kN (Ф1.2m). + Embedded 10m in 6b: Q w = 3230 kN (Ф0.8m); Qw = 4430 kN ( Ф1.0m); Qw = 5780 kN (Ф1.2m).

•

For PMT Method: + Embedded 5m in 6b: Q w = 2530 kN (Ф0.8m); Qw = 3320 kN (Ф1.0m); Qw = 4170 kN (Ф1.2m). Union of Survey Companies (USCo.)


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+ Embedded 10m in 6b: Qw = 3030 kN (Ф0.8m); Qw = 3950 kN (Ф1.0m); Qw = 4926 kN (Ф1.2m). d) Expected settlement of single pile under design load:

•

•

For SPT Method: + Embedded 5m in layer 6b: Si = 14.9mm (Ф1.2m). + Embedded 10m in layer 6b: Si = 14.8mm (Ф1.2m). For PMT Method: + Embedded 5m in layer 6b: Si = 10.8mm (Ф1.2m). + Embedded 10m in layer 6b: Si = 11.9mm (Ф1.2m).

6.6mm (Ф0.8m); Si = 9.9mm (Ф1.0m); Si = 6.7mm (Ф0.8m); Si = 10.2mm (Ф1.0m); Si =

8.2mm (Ф0.8m); Si = 9.5mm (Ф1.0m); Si = 9.7mm (Ф0.8m); Si = 10.7mm (Ф1.0m); Si =

However, the settlement of pile group shall be higher depending of group dimension. 2) Basically, result of pile foundation calculated by both SPT & PMT methods are quite agreement. However, above values are typical representative for location of CK.46. The sub-ground condition and the surface depth of soft bed-rock are varied from location to location, so the actual pile depth (or length) shall be varied accordingly. V.4

ANALYSIS OF LIQUEFACTION OF GROUND DUE TO SEISMIC

V.4.1 Japan’s Method for Liquefaction due to Seismic According to “Standard Specifications for Highway Bridge, Vol.- Earthquake-Proof Design; 1996 Japan Highway Association”, liquefaction of ground due to earthquake is presented as follows: 1) Necessary Condition: The saturated sandy soil has a possibility to occur the liquefaction phenomenon, which the ground becomes liquid state due to the increase of pore water pressure caused by seismic repeated shearing force and the sandy soil spouts on the ground surface, in case of fulfilling as the following three conditions: - Depth of ground water is in being the range between 0.0 to 20 m from ground surface, - Fine grained content (Fc) is less than 35 %, or the plastic index (Ip) is less than 15 in case of that Fc is more than 35%, - Average grading size (D 50) is less than 10.0 mm and the grading size of 10 % (D 10) is less than 1.0 mm. 2) Calculation Method: In the case of that the below FL-value is less than 1.0 the ground is shall be regarded to be subjected by liquefaction: FL = Where,

R L

(21)

FL : Liquefaction resistance rate L : Shearing stress ratio during earthquake R : Dynamic shearing strength ratio

- Shearing Stress Ratio during Earthquake: L σ v L = r d ･ K h ･ σ v ' Union of Survey Companies (USCo.)


(22)

35

Where r d : Decrease coefficient proportional to depth r d = 1.0 - 0.015z, in which z is depth (m) Kh : Design horizontal seismic coefficient, σv : Total overburden pressure (kg/cm2) σ’v : Effective overburden pressure (kg/cm2) - Dynamic Shearing Strength Ratio: R Na < 14 :

R = 0.0882

14 < Na :

R = 0.0882

Na 1.7 Na 1.7

(23)

+ 1.6 × 10 −6･ ( Na − 14) 4.5 (24)

Where, for Sandy Soil: Na = c1N1 + c2 N1 =

(25)

1.7･ N σ v'+0.7

⎧ 1 ⎪⎪ c1 = ⎨ (Fc + 40) / 50 ⎪ ⎪⎩ Fc / 20 − 1 ⎧⎪ 0 c2 = ⎨ ⎪⎩ (Fc − 10) / 18

(0 % < Fc < 10 %) (10 % < Fc < 60 %) ( 60 % < Fc ) (0 % < Fc < 10 %) ( 10 % < Fc )

for Gravely Soil: Na = N1 ･( 1 − 0.36 log 10

N1 =

Where,

D50 2

)

(26)

1.7･ N σ v'+0.7

N : N-value from standard penetration test N1 : Corrected N-value, equal with 1.0 kg/cm 2 of effective Over-burden pressure Na : Corrected N-value considered with fine grained content Fc : Fine grained content (%)

2) Result of Liquefaction Determination after Japanese’s Method Based on the result of the sub-ground condition, the following observations may be provided: - The stratum 3 is basically clayey sand, fine sand or sand interbedded lenses of silty clay. Layer 3a is generally loose to medium state and no or little gravel, so the liquefaction possibility is susceptible occurred. The other dense gravelly sand layers (3b, 4a, 4b) may difficulty to be liquefied. - More-ever, above loose silty fine sand is mostly under groundwater level, so the liquefaction this more susceptible to be occurred. The groundwater depth recorded in April 2009 (starting of rainy season) is about 1.9m. However, groundwater depth recoreded in Dember 2009 (dry season) is about 3.2m, so the depth of 2.0m shall be taken in calculation. The result of liquefaction analysis due to a “computer program” for some typical locations within project area is shown in the table 11.



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Table 11: Calculation Result of Liquefaction Possibility

a) Result from Soil Investigation in March 2009



37



38

b) Result from Soil Investigation in December 2009

Comment & Recommendation 5 : Based on liquefaction analysis from both stages (feasibility soil investigation stage for bidding implemented in March 2009 and preliminary stage for construction design implemented in December 2009), the following comments and recommendations may be made: 1) The liquefaction may be occurred in layer 3a (silty fine sand, clayey sand) developed under groundwater, especially it’s susceptible occurred in loose soil (N 30 < 10). Result of both analysis methods (Japan’s standard & China’s standard) shown that the liquefaction may be occurred with seismicity grade VII to VIII in intensity. 2) Based on “Japan Highway Bridge Design Standard”, the design parameter (coefficient of ground reaction, skin friction of pile, and elastic modulus of ground, and so on) shall be reduced according to FL-value, by multiplying with the following decrease parameter (DE): Table 12: Decrease Parameter DE

FL-value FL < 0.6 0.6 < FL < 0.8 0.8 < FL < 1.0

Depth (m) 0 < z < 10 10 < z < 20 0 < z < 10 10 < z < 20 0 < z < 10 10 < z < 20

Decrease coefficient DE 0 1/3 1/3 2/3 2/3 1



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VI

CONCLUSION AND RECOMMENDATION

1 - Subsurface condition of project item is fairly clarified by two main geological zones (unless made ground), which is described from ground surface as follows: a) Quaternary System (Q) includes Vinh Phuc Formation (abQIII vp ) anf Ha Noi Formation (abQII-III hn), which consists of: Stiff to very stiff brown clay (2a), sof to firm grey silty Clay (2b); loose to medium dense clayey sand (3a), medium dense clayey sand mixed gravel-cobble (3b), medium dense sand with little or no gravel (4a), dense and coarse sand mixed gravel-cobble and soft to medium stiff clay (5). This Quaternary Zone is usually developed from ground surface to about 15-18m in depth. a) Weathered Rocks of Cretassic System, Hong Gai Formation (T2 n-r hg 1,2 ) includes claystone & silty claystone (stratum 6), silty sandstone & sandstone (stratum 7), which may be classified by various jointing-weathering degree and strength (6a, 6b… and 7a, 7b…). Basically, these silty claystone and sandstone interbedded each other, highly to completely weathered becoming very soft in rock state, but very hard in soil state, which are developed to more than 60m in depth. 2 - The engineering properties of “geotechnical layers” for above soils and rocks are studied by both in-situ test (by SPT, MPT) and laboratory test in soil and rock samples, which are presented in the paragr aph III.6 and tables 3 (q,b). 3 - The groundwater level was measured in boreholes and the result is presented in paragraph III.7. The static water depth recorded during drilling (at 8h 27 November 2009), are shown that: 3.76m in CK02; 3.41m in CK59 and 3.50m in CK81. This groundwater depth is recorded in dry season, so in rainy season, groundwater level shwll be higher . The chemical analysis of groundwater and corrosion to building material is shown in the table 4. 4 - The geophysical exploration was carried out by earth resistivity method, seismic down-hole sounding method. Detail result is shown in Appendices 7, 8 and summarized result is shown in the tables 5 & 6. 5 - Shallow foundation founded right upon stiff clay (layer 2a) may mobilize allowable bearing resistance qa ≠ 190 – 220 kPa (of footing width B = 2m width) may attained St = 3 - 5 cm , (under net applied pressure Pn). The design parameters may be referenced to “Comment and Recommendation 2”, which may be suitable for light to medium heavy building structures. 5 – Driven Pile shall be alternatively useful for moderately heavy structure, where shallow foundation is not compatible. The pile-tip should be penetrated in dense sand (layers 3b, 4a, 4b). However, the pile tip must be penetrated through soft to firm clayey layer 5 (where it’s encountered) and at least 0,5m in soft claystone (6b). The typical design loads of various pile-sizes may be referenced to “Comment and Recommendati on 3”. 6 – Bored Pile must be used for very heavy and important structures and the pile must be embedded deeply in soft rocks of silty claystone (6b) and silty sandstone (7b). Detail analysis result is described in paragraph V.3 and the typical design parameters may be referenced to “Comment and Recommendation 4”. 7 - The loose silty-clayey fine sand layer 3a is susceptible with liquefaction due to seismic intensity grade VII & VIII. Analysis result presented in paragraph V.4 and “Comment & Recommendation 5” may be referenced for design study. Union of Survey Companies (USCo.)


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Geotechncial Report - Tran Van Viet

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