Geotechnical Investigation Report Templates

Solium Bore Consult Inc. Geotechnical Investigation Report

Dagupan Health Center Two (2) Storey Building

PROJECT INFORMATION Project Reference #: Project Name:

1305DE03 DAGUPAN HEALTH CENTER

Project Location: Client:

DAGUPAN ST. TONDO, MANILA DPWH North Manila Engineering District

Client’s Address: Consultant:

Solium Bore Consult Inc.

Contact Number:

1.0

DPWH Nagtahan, Sta. Mesa, Manila

09066892177

INTRODUCTION

The DPWH North Manila Engineering District, henceforth known as the Client, obtains the services of Solium Bore Consult Inc. to perform a subsurface investigation of a Proposed Two (2) Storey Building (Dagupan Health Center) located at Dagupan St., Tondo, Manila, Philippines. The objective of this report, by using the soil samples obtained underneath the site, is to provide geotechnical assessments based on the laboratory tests results. For

an

elaborate

and

systematic

plan of action

for

the

foundation,

recommendations will be provided on the following: Evaluation of the general suitability of the site for the proposed project. Anticipating and provision against difficulties that may ascend during construction due to ground and other local conditions. Attainment of physical and mechanical properties of soils for sufficient and economic design.

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Knowledge of groundwater conditions. Knowledge of the suitability of materials for construction General guidelines and strategies in the implementation of the construction procedures. Allowable bearing capacities of probable foundations

2.0

SCOPE OF WORK SUMMARY

A borehole is drilled within the vicinity of the proposed building. Standard Penetration Testing (SPT) is performed every 1.50 meters and core samples are taken in each interval. The borehole reaches a depth of 12.00 meters for good measure of the underlying material. The samples are subjected to routine laboratory tests to determine the classification of the materials using the Unified Soil Classification System (USCS) and their corresponding engineering properties. 2.1 DETAILS OF FIELD WORKS Table 1. Summary of field works Borehole No.

Drilling Depth (m)

1

12

No. of Samples SPT Coring 8 0

2.2 DETAILS OF LABORATORY WORKS Table 2. Summary of laboratory works Laboratory Test

No. of Samples

Particle Size Distribution Moisture Content Atterberg Limits Unified Soil Classification System

8 8 8 8

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3.0


GENERAL GEOLOGY AND SITE CONDITION

3.1 General Area The project area is located in Dagupan St. Tondo, Manila; the location is undoubtedly underlain by alluvial soils. The general topography was relatively flat surface. An unlined creek was located near the site at a distance approximately 240 meters. (Refer to Figure 1).

Figure 1. General Location (Google Earth) 3.2 Site Specific The proposed building is located in a crowded and with an existing structures area. Since the location of the structure is not on the list of the flood prone area made by the MMDA and Project NOAH researchers in Manila City, it is free from flooding, hence the water level will not reach into the grade elevation.

3.3 Seismicity It has been predicted by the study made by PHIVOLCS, the MMEIRS, that an earthquake with a magnitude of 7.5 may occur within this era, when the West Valley fault moves. By using Google earth, it was measured to have an

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approximate distance of 12 km from the site to the nearest line of the West valley Fault.

4.0

METHODOLOGY OF THE INVESTIGATION

4.1 FIELD SAMPLING & TESTING The boreholes are advanced by rotary drilling and wash boring method. Alternately with these methods, SPT is conducted at every 1.5 meter depth interval on soil layer, while rotary drilling on hard materials down to the bottom of the hole. Protective casings are inserted around the hole with a drop hammer to prevent materials from collapsing. The boring operation entails the following phases:

4.1.1 DRILLING WORKS a) Rotary Drilling A method employed when hard materials are encountered or where the N-value exceeds fifty (50). Under rotary action, the 46 mm diameter core bit is advanced into the rock with core runs between 1.00 to 1.50 meters. b) Wash Boring A process in advancing the borehole by applying an up and down twisting motion of a drill or chopping bit attached to the ends of drill rods while simultaneously allowing a stream of water pumped through the rods to the soil. The combined action of the water jet and chopping loosens the soil and is flushed to the surface. c) Standard Penetration Test (ASTM-D1586) The main sampling procedure conducted at every 1.50 meter depth interval using a Donut free fall type of hammer. It involves placing a 50.80 mm (O.D.) diameter split spoon sampler with the drilling rod into the ground at the bottom of the

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borehole. The hammer weighs 63.50 kg and is dropped a distance of 762 mm to produce a theoretical input driving energy (Ein) of 473.28 Nm. The number of blows to penetrate every 150 mm interval is recorded successively until the third interval is penetrated. The first interval blow count is considered as the seating drive and is discarded. The last two blow counts from the second and third intervals are added to give what is known as the N-value. Disturbed soil samples obtained by the split spoon were collected for visual inspection and laboratory testing. d) Ground Water Level This measurement is done by lowering a weighted tape down the hole until water contact is made. Readings are made after water is allowed to stand for a minimum period of 12 hours following completion of the drilling. The observation made during this period is assumed as the ground water level.

4.2 DETAILS OF LABORATORY WORKS The following laboratory tests are performed in accordance with the specified procedures from the American Society for Testing and Materials (ASTM). Appropriate test procedures are referenced in ASTM Manuals for the soil tests discussed in the following sections:

a) Natural Moisture Content (ASTM-D2216) This test is also known as water content. It is the ratio expressed as a percentage of the weight of water in a given mass of soil to the weight of the solid particles. b) Grain Size Analysis of Soils (ASTM-D422)

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A process wherein the proportion of each grain size present in a given soil sample (grain-size distribution) is determined. The grain- size distribution of coarse – grained soils is determined directly by sieve analysis, while that of fine-grained soils is determined indirectly by hydrometer analysis. The grain-size distribution of mixed soils is determined by combined sieve and hydrometer analyses. c) Atterberg Limits of Soils (ASTM-D4318) A procedure that consists of several parameters that are primarily water contents which define the limits of various stages of consistency for fine-grained soils. The liquid limit (LL) and the plastic limit (PL) define the upper and lower limits, respectively, of the plastic range of a soil; the numerical difference between these two limits expresses the plasticity of a soil and is termed the plasticity index (PI). d) Classification of Soils for Engineering Purposes (ASTM-D2487) In general, soils are classified based on the Unified Soil Classification System (USCS). In this system, soil falls within one of the three major categories: coarsegrained, fine- grained, and highly- organic soils.

5.0

OBSERVATION OF RESULTS

The table below shows the summary results of the borehole. The profiles of the index properties and in-situ moisture content of each borehole are also illustrated.

DEPTH

NVal ue

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USC S

DESCRI PTION

BOREHOLE CONSISTE NCY

INDEX PROPERTIES

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0.00 1.50

13

SCSM

1.50 3.00

22

SCSM

3.00 4.50

3

SM

4.50 6.00

3

6.00 7.50 7.50 9.00 9.00 -10.50 10.50 12.00


Silty clayey SAND with gravel Silty clayey SAND with gravel Silt SAND

MEDIUM DENSE

CL

Sandy LEAN CLAY

SOFT

7

CL

Sandy LEAN CLAY

MEDIUM STIFF

59

GC

VERY DENSE

67

SC

72

SC

Clayey GRAVEL with sand Clayey SAND with gravel Clayey SAND with gravel

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MEDIUM DENSE

VERY LOOSE

VERY DENSE VERY DENSE

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6.0 ENGINEERING ANALYSIS AND CONSIDERATIONS 6.1 SITE CONDITIONS The borehole shows sand deposits found in the surface layer, described by mostly sand in varying portions of fine-grained materials. There is irregularity with increasing depth; a deeper soil layer may less dense compare to shallower layers. This just confirms the predicted geology of the dynamic alluvial depository area. With the inconsistencies of the surface soils, it is highly likely that the site will experience differential settlement. After the first 7.5 meters, the soils encountered to be competent layers. Since these soil types are potentially liquefiable, the existence of alluvial soils on the surface is also cause for immediate concern. These layers warrant a closer inspection prior to recommending foundation schemes.

6.2 LIQUEFACTION POTENTIAL In assessing the possible of the soil for liquefaction, the simple criteria provided by the National Structural Code of the Philippines, (NSCP) 2010, Section 303.4 is used. Soils conforming all three of the following provisions will be considered liquefiable: 1) Shallow ground water, two meters or less 2) Unconsolidated saturated alluvium (N<15) 3) Seismic Zone 4 The project site is clearly located in a Seismic Zone 4. The upper 7.5 meters of soil is also considered to be unconsolidated alluvium as derived from the index properties. Finally, the same upper layers show samples having N-values less than or close to 15.

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The hazard map provided by the Philippine Institute of Volcanology & Seismology (refer to Figure 2) further calls for attention. It illustrations that the project area is problematically at the boundary of the said liquefiable soils. This, however, helps only as a guide and detailed calculations of engineering properties is needed for confirmation.

Figure 2. Liquefaction hazards in Metro Manila (Philvocs) The loose to medium dense layers classified as predominantly cohesionless soils are the primary target. Due to lack of testing specific to liquefaction, analysis is done by correlating to SPT N-values. The Factor of Safety (FS) for liquefaction potential is calculated as the ratio of the Cyclic Resistance Ratio (CRR) to the Cyclic Tress Ratio (CSR).

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Where:

Where:

DEPTH (m) 0 – 1.5 1.5 – 3.0 3.0 – 4.5 4.5 – 6.0 6.0 – 7.5 7.5 – 9 9 – 10.5 10.5 - 12 *amax = 0.4g

CRR 0.3371 0.3872 0.0572 0.0552 0.0732 1.6416 0.9393 0.9096

CSR 2.6605 2.3947 2.3175 2.2808 2.2593 2.2452 2.2352 2.2278

FS 0.1267 0.1617 0.0247 0.0242 0.0324 0.7312 0.4202 0.4083

**the factor of safety is at earthquake magnitude 7.5

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These data indicates that the project area is prone to liquefaction. The distribution of potentially liquefiable soils within the project area is not fully known since the boreholes show variations in consistencies. What is consistent is the fact that the hazardous layers are encountered only up to depths of 7.5 meters. But, as mentioned, this general analysis is based only on SPT correlations. It is recommended that further testing should be conducted specific to liquefaction.

6.3 FOUNDATION DESIGN RECOMMENDATION In this report the exact structural details of the proposed building are not known and the recommendations listed below are based only from the soil profile of the borehole results and the potential problems that may occur during the project construction. The proposed building is recommended to be fitted with the following foundation schemes. 

Shallow Foundation:



Spread Footing (Square & Rectangular)

The listed options above are provided for the discretion of the structural designer. Since the soil properties used for the design of the proposed building foundation came from only one borehole, inconsistency in the soil properties for the entire project area must be taken into consideration, saying so, it is important to verify the consistency of the soil properties during construction. 6.4 SHALLOW FOUNDATION The maximum load that the underlying soil may carry from the structure is estimated using Terzaghi’s (1943) bearing capacity equation below. Qu = cNcsc + γ1DfNq + 0.5γ2B Nysy where: Qu = ultimate bearing capacity c = cohesion Nc,Ny,Nq = bearing capacity factors

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B = width of footing Df = footing depth (embedment depth) γ1 = effective unit weight of soil above footing level γ2 = effective unit weight of soil below footing level sc = shape factor (strip=1.0, square=1.3) sy = shape factor (strip=1.0, square=0.8) Qa = Qu / FS where:

Qa = allowable bearing capacity FS = factor of safety (standard practice=3.0)

a) Spread Footing In shallow foundations, spread footings is simply an enlargement of a load-bearing Wall or column which allows this load carrying members to spread the load of the structure over a large area of soil. Listed below are the computed possible bearing capacities for spread footings. The building’s shorter width corresponds to the listed footing widths. An estimated value of 18kN/m3 is used in this computations. Footing Width (B), m

Table

0.80 1.00 1.50 2.00

Allowable Bearing Capacity (Qa), kPa Df = 1.0m Df = 1.5m Df =2.0m 213.82 288.76 363.70 229.80 304.74 379.68 269.76 344.70 419.64 309.72 384.66 459.60

6. Summary of Allowable Bearing Capacities for Spread Footing If the desired dimension for the footing is not included in the list above, computations for the allowable bearing capacity (Qa) of soil must be computed only based solely from Terzaghi’s (1943) bearing capacity equation, bearing capacity factors may found in Table 12.2 of the book Geotechnical Engineering (Philippine Edition) by Braja M. Das. 6.5 FILL CONSTRUCTION According in AASHTO sec. 18, the fill shall not consist of any organics, frozen lumps and larger than 1.5 in. in greatest dimension. And it was specified that the backfill moisture content shall be in the range of optimum and that backfill shall be

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compacted to a minimum of 90% standard density as established by AASHTO T99. (Das, 2015)

6.6 HYDROLOGICAL FACTORS

There is no occurrence of ground water level in 15 m deep bore. But there must be an effective drainage to release water from rain or other external source. Water canal can be use as drainage. 6.7 EXCAVATION

There is no presence of groundwater table in the site based on the bore log. However it is somehow needed to provide temporary support system like tiebacks or rakers during construction (Day, 2012). Consider the possible instability in any exposed slope. The sliding potential behind the tieback should also be evaluated. Also include in stability analysis the weight of surcharge or weight of other facilities in close proximity to the excavation (Day, 2012). 6.8 PAVEMENT DESIGN

The site is free from flood and has a great value of allowable soil strength as being computed on the previous part. Although light cracks might occur due to alkali-silica reactivity (Rosas, 2014) the client may request to add reinforcement bar for a more durable pavement.

6.9 SEISMIC DESIGN CONSIDERATION 1104DDI1_RGIR_RCS_0

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The nearest fault from the structure that can generate seismic force is the West Valley Fault based on the large scale-active fault map of the Philippine fault made by Tsutsumi and Perez of 2013. It is measured using Google earth application to have a 12 Km distance from the structure to the nearest section of the fault. The parameters in which the NSCP code provision (2010) for the earthquake design of the building may satisfy was determined. The seismic source type falls under the A category, in which the near source factors are N a= 1.00 and Nv= 1.2.The site has a soil profile type Sc and it falls in zone 4 having Z= 0.4. The seismic response coefficient are Ca= 0.40Na and Cv= 0.56Nv.

7.0

LIMITATIONS

Qualified judgment and recommendations are delivered in this report. The geotechnical assessments and recommendations stated above were analysed and determined based on the results from the one (1) borehole drilled from Tondo, Manila for the construction of Dagupan Health Center. This has been developed as a guide for the design of the proposed project. The analyses, evaluations and recommendations submitted in this report are founded on the technical information and data from field borings and laboratory test conforming to the generally accepted engineering principles and practices. There may be inconsistencies and variations of subsoil conditions among borings which may only be evident until the construction is started.

Some unfavourable/unanticipated subsurface conditions

are commonly encountered and the owner/clients must be aware of it. Perched aquifers, soft deposits, hard layers, or cavities are examples of unforeseen soil/rock conditions that may occur on confined areas. These may require

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exploring, examining or corrections in the field to conduct a well-constructed structure.

We do not secure the performance of the project in any aspect other than our engineering specialty. The conclusions and recommendations rendered meet the standards and care of our profession. We request to be immediately noticed if: during the construction the soil conditions vary from that of the report or some differences occur in location or design features as we comprehend it and as stated in the test borings. Please do reach us on the contact number provided on the first page of this report or come through our office stated below to immediately apply changes and corrections.

8.0

REFERENCE

Das, B. M. (2015). Fundamentals of Geotechnical Engineering . Day, R. W. (2012). Geotechnical Engineer's Portable Handbook. Rosas, A. (2014). Experiment Investigation on the Alkali Silica Reaction Effect on Concrete Strength Degradation.

(National Structural Code of the Philippines, 2010) (AASHTO Green: A Policy on Geometric Design of Highways and Streets, 2001)

Prepared by: Camille Angelie J. Soribello Civil/Geotechnical Engineer PRC No.: 0927995 PTR No.: 022729 SEPTEMBER 27, 2014 1104DDI1_RGIR_RCS_0

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