LABORATORY 3
Geotechnical Engineering Laboratory [Consolidation Test]
Table of Contents
Introduction............. Introduction.......................... ........................... ....................... ......... 2 Purpose and Objectives.... Objectives................. ......................... ...................... .......... 2 Theory................... Theory................................. ........................... ...................... ......... 2 Equipment and Apparatuses... Apparatuses................ .......................... .................... ....... 4 Method and Procedure................ Procedure............................. ......................... ............ 6 Numerical example....... example................... .......................... ......................... ........... 6 Lab Data Observation.............. Observation........................... ........................... .............. 7 Calculation.............. Calculation........................... ........................... ....................... ......... 9 Spring No.2 ......................... ....................................... ....................... ......... 9 Spring No.3 ......................... ....................................... ...................... ........ 11 Discussion............... Discussion............................ ........................... ...................... ........ 14 Question and Answer: ......................... ...................................... ............. 14 Advantages and Disadvantages: Disadvantages: ......................... ............................. .... 15 Conclusion............... Conclusion............................ ........................... ...................... ........ 15 References............... References............................ ........................... ...................... ........ 16 Appendix................. Appendix.............................. ........................... ...................... ........ 16 Appendix A: ......................... ....................................... ...................... ........ 16
SAYED ASADULLAH
UNISEL, FACULTY OF ENGINEERING, CIVIL DIVISION
LABORATORY 3
Geotechnical Engineering Laboratory [Consolidation Test]
Vane shear test is used to measure the shear strength of a soil. It also estimated and measured the fully saturated clay’s undrained shear strength without derangement in the specimen. This test can be conducted in field and laboratory however, in laboratory can only execute the experiment with low shear strength (0.3 kg/cm2) for which unconfined test cannot be performed. The test apparatus are composed of 3 different diameters of 4 -blade stainless vane that is attached in a steel rod that pushed vertically in the soil. The pocket value that can get in small vane should multiply by two however, the value can get in large vane should divide by two and the value v alue that can get in medium vane is as it is. The test is performed by pushing the vane vertically in the soil and rotated it clockwise from the surface to determine the torsional force. The soil will resist the rotation of the vane and its resistance is the force of soil that causes the cylindrical area to be sheared by the vane. When the rotation of the vane is continues it means that the soil fails in shear and it is normal that the rotation is continued after measuring the shear strength.
The vane test provides a measure of the stress-strain behavior, the undrained shear strength, and the remolded strength of soft saturated cohesive soils.
Fairly reliable results for the in situ undrained shear strength, c u(ɸ=0 concept) ofsoft plastic cohesive soils may be obtained directly from vane shear tests during the drilling operation (ASTM Test Designatin 2573). The shear vane usually consists of four thin, equal –sized steel plates welded to a steel torque rod. First, the vane is pushed into the soil. Then torque is applied at the top of the torque rod to rotate the vane at a uniform speed. A cylinder of soil of height h and diameter d will will resist the torque until the soil fails. The undrained shear strength of the soil can be calculated as follows; if T is is the maximum torque applied at the head of the torque rod to cause failure, it should be equal to the sum of the resisting moment of the shear force along the side surface of the soil cylinder (M s) and the resisting moment of the shear force at each end (M e).
Two Ends
SAYED ASADULLAH
UNISEL, FACULTY OF ENGINEERING, CIVIL DIVISION
LABORATORY 3
Geotechnical Engineering Laboratory [Consolidation Test]
The resisting moment Ms can be given as
⁄ Surface Area Moment Arm
o
The standard rate of torque application is 0.1 /sec . the maximum torque T is applied to cause failure can be given as;
Or
According to ASTM (2010), for rectangular vanes,
( ( ) If h/d=2,
Thus
For tapered vanes,
( ) Field vane shear tests are moderately rapid and economical and are used extensively in field soil-exploration programs. The test gives good results in soft and medium stiff clays, and it is also an excellent test to determine the properties of sensitive clays.
SAYED ASADULLAH
UNISEL, FACULTY OF ENGINEERING, CIVIL DIVISION
LABORATORY 3
Geotechnical Engineering Laboratory [Consolidation Test]
1. Laboratory Vane Apparatus [Figure 1] 2. Calibrated springs supplied with the vane apparatus [Figure 2] 3. Standard vane, 12.7mm 12.7mm [Figure3] 4. Attachment for holding soil sample tubes or glass sampling jars.
1
2
4 5
3 6 7 8 9 15 10 11
12 13 14
Figure 1; Laboratory Vane apparatus apparatus
SAYED ASADULLAH
UNISEL, FACULTY OF ENGINEERING, CIVIL DIVISION
LABORATORY 3
Geotechnical Engineering Laboratory [Consolidation Test]
1. Hand Knob 2. Vertical screw control 3. Knurled Knob 4. Electrical motor 5. Pointer 6. Carrier 7. Vane deflection scale 8. Spring deflection scale 9. Vertical shaft 10. Rotating socket 11. Vane 12. Cylinder 13. Both for tighten the cylinder to plate. 14. Plate 15. Calibrated springs. 15
Figure 2 ; Calibrated Springs
11
Figure 3 ; Vane
SAYED ASADULLAH
UNISEL, FACULTY OF ENGINEERING, CIVIL DIVISION
LABORATORY 3
Geotechnical Engineering Laboratory [Consolidation Test]
The vane apparatus is assembled by mounting the vane and spring appropriate for the soil to be tested. Instruction provided with the vane apparatus are to be followed for adjustment of the pointer used in reading the spring and vane deflection.
The soft clay to be tested may include tube samples – 38mm (1 ½ in) or 115mm (4 ¼in) – or soil in glass sampling jars or Proctor molds. The clamping attachment will hold the soil container vertically below the vane shaft.
The soil surface should be trimmed so as to permit the vane to be lowered into the soil to a depth sufficient to ensure that shearing shearing will take place on the horizontal edges of the vane without movement of the soil sample surface.
With the vane in position, apply torque to the vane at a rate that should not exceed 0.1 deg/s. This rate will normally give a time to failure of from 2 to 5 min. In very soft clays the time to failure may be longer. Record the maximum torque with motorized apparatus.
Record values of spring and vane deflection at intervals of 1 5 s or less as needed to prepare torque or strength curves. Following determination of the vane shear strength, remold the soil by rotating the vane rapidly through a minimum of 10 revolutions.
Immediately repeat the vane test to determine the remolded vane shear strength. After the test select a representative portion of the sample for a water content determination.
Data from the vane test are recorded in the term of a spring deflection and a vane deflection on the data and calutation sheet. The torque is obtained by noting the angular spring deflection and reading the relecant spring spring calibration chart. chart. Alternatively the torque maybe computed using the relevant spring constant. The vane shear strength is now computed suing the vane constant T as defined at the bottom of the data sheet. The data maybe summaried as illustrated in figure. Water content data included for use in making, comparisons with other vane test data.
SAYED ASADULLAH
UNISEL, FACULTY OF ENGINEERING, CIVIL DIVISION
LABORATORY 3
Geotechnical Engineering Laboratory [Consolidation Test]
Vane Diameter (D) =12.7mm Vane Length
(L) =12.7mm
Vane Height
(H) =12.7mm
Observed Data from Spring No.2
SAYED ASADULLAH
UNISEL, FACULTY OF ENGINEERING, CIVIL DIVISION
LABORATORY 3
Geotechnical Engineering Laboratory [Consolidation Test]
Observed Data from Spring No.3
SAYED ASADULLAH
UNISEL, FACULTY OF ENGINEERING, CIVIL DIVISION
LABORATORY 3
Geotechnical Engineering Laboratory [Consolidation Test]
Vane Constant
( ( ) Spring No.2 From the plotted Graph [Appendix B] Gradient
Spring Data Point 1:
Time
Spring No.2 point 1 o Spring( ) Torque (Nm)
Shear strength (KN/m)
30 60 90 120 150 180 210 240 270 300 330 360 390 420 450 480 510
4.5 8.5 13.5 18 21 26 34 34 38 43.5 48.5 52.5 54.5 57 59 59.5 61
0.01 0.03 0.04 0.05 0.06 0.08 0.10 0.10 0.11 0.13 0.15 0.16 0.16 0.17 0.18 0.18 0.18
3.15 5.94 9.44 12.59 14.69 18.18 23.78 23.78 26.57 30.42 33.92 36.71 38.11 39.86 41.26 41.61 42.66
Maximum Degree of spring deflection =61.0 Maximum Torque, T = Maximum spring x Gradient for spring no 2 Tmax = 61 × 0.003 = 0.18 Nm
SAYED ASADULLAH
UNISEL, FACULTY OF ENGINEERING, CIVIL DIVISION
LABORATORY 3
Geotechnical Engineering Laboratory [Consolidation Test]
Spring Data Point 2:
Time
Spring No.2 point 2 o Spring( ) Torque (Nm)
Shear strength KN/m)
30 60 90 120 150 180 210 240 270 300 330 360 390 420 450 480 510
5 7 7.5 10 15.5 21 26.5 30 34.5 38 44 46 47.5 48 53 55 55
0.015 0.021 0.0225 0.03 0.0465 0.063 0.0795 0.09 0.1035 0.114 0.132 0.138 0.1425 0.144 0.159 0.165 0.165
3.50 4.90 5.24 6.99 10.84 14.69 18.53 20.98 24.13 26.57 30.77 32.17 33.22 33.57 37.06 38.46 38.46
Maximum Degree of spring deflection =55.0 Maximum Torque, T = Maximum spring x Gradient for spring no 2 Tmax = 55× 0.003 = 0.165 Nm
Spring Data for point 3:
Time
Spring No.2 point 2 o Spring( ) Torque (Nm)
Shear strength (KN/m)
30 60 90 120 150 180 210 240 270 SAYED ASADULLAH
5 7 7.5 9 12.5 20 24.5 28.5 33
0.015 0.021 0.023 0.027 0.038 0.060 0.074 0.086 0.099
3.50 4.90 5.24 6.29 8.74 13.99 17.13 19.93 23.08
UNISEL, FACULTY OF ENGINEERING, CIVIL DIVISION
LABORATORY 3 300 330 360 390 420 450 480 510
Geotechnical Engineering Laboratory [Consolidation Test] 36.5 40.5 44.5 45.5 47.5 50.5 51.5 51.5
0.110 0.122 0.134 0.137 0.143 0.152 0.155 0.155
25.52 28.32 31.12 31.82 33.22 35.31 36.01 36.01
Maximum Degree of spring deflection =51.5 Maximum Torque, T = Maximum spring x Gradient for spring no 2 Tmax = 51.5× 0.003 = 0.155 Nm
Spring No.3
From the plotted Graph [Appendix B] Gradient
Spring data, point one:
Spring 3 point 1 Time
Spring(o)
Torque (Nm)
Shear strength (KN/m)
30 60 90 120 150 180 210 240 270 300 360 390 420 450 480 SAYED ASADULLAH
4.5 8.5 13.5 18 21.5 26.5 34 34.5 38.5 43.5 48.5 52.5 54.5 57 59
0.009 0.017 0.027 0.036 0.043 0.053 0.068 0.069 0.077 0.087 0.097 0.105 0.109 0.114 0.118
2.10 3.96 6.29 8.39 10.02 12.35 15.85 16.08 17.95 20.28 22.61 24.48 25.41 26.57 27.51
UNISEL, FACULTY OF ENGINEERING, CIVIL DIVISION
LABORATORY 3 510 540 570
Geotechnical Engineering Laboratory [Consolidation Test] 59.5 61.5 61.5
0.119 0.123 0.123
27.74 28.67 28.67
Maximum Degree of spring deflection =61.5 Maximum Torque, T = Maximum spring x Gradient for spring no 2 Tmax = 61.5× 0.002 = 0.123 Nm
Spring data, point two:
Time
Spring 3 point 2 Torque (Nm) Spring ( )
Shear strength (KN/m^2)
30 60 90 120 150 180 210 240 270 300 360 390 420 450 480 510 540 570
3.5 8 12.5 17.5 21 24 31 33 35.5 37.5 38.5 41 42.5 45 46.5 51 53.5 53.5
0.007 0.016 0.025 0.035 0.042 0.048 0.062 0.066 0.071 0.075 0.077 0.082 0.085 0.090 0.093 0.102 0.107 0.107
1.63 3.73 5.83 8.16 9.79 11.19 14.45 15.38 16.55 17.48 17.95 19.11 19.81 20.98 21.68 23.78 24.94 24.94
Maximum Degree of spring deflection =53.5 Maximum Torque, T = Maximum spring x Gradient for spring no 3 Tmax = 53.5× 0.002 = 0.107 Nm
SAYED ASADULLAH
UNISEL, FACULTY OF ENGINEERING, CIVIL DIVISION
LABORATORY 3
Geotechnical Engineering Laboratory [Consolidation Test]
Spring Data Point 3:
Time
Spring 3 point 2 Torque (Nm) Spring ( )
Shear strength (KN/m^2)
30 60 90 120 150 180 210 240 270 300 360 390 420 450 480 510 540 570 600
3.5 4.5 8.5 13 15 16.5 25 26 28.5 31.5 33 35 36 40 43 54 58 61 61
0.007 0.009 0.017 0.026 0.030 0.033 0.050 0.052 0.057 0.063 0.066 0.070 0.072 0.080 0.086 0.108 0.116 0.122 0.122
1.63 2.10 3.96 6.06 6.99 7.69 11.66 12.12 13.29 14.69 15.38 16.32 16.78 18.65 20.05 25.17 27.04 28.44 28.44
Maximum Degree of spring deflection =61.0 Maximum Torque, T = Maximum spring x Gradient for spring no 3 Tmax = 61.0× 0.002 = 0.122 Nm
2
/m
SAYED ASADULLAH
UNISEL, FACULTY OF ENGINEERING, CIVIL DIVISION
LABORATORY 3
Geotechnical Engineering Laboratory [Consolidation Test]
Question and Answer:
I.
For the Tapered Vane shown in [Figure 6] de velop an expression for the constant K needed in computation of S u=T/K, where T is the torque required to rotate the vane.
Figure 4 ; Geometry of field vane “Tapered Vanes”
Answer:
( ) II.
For the same vane, develop an expression for evaluation of the vertical (S uv) and horizontal (SUH) undrained shear strengths.
Answer:
( ) Where: T is is the Maximum Torque measured H/D is H/D is the aspect ratio of the vane
SAYED ASADULLAH
UNISEL, FACULTY OF ENGINEERING, CIVIL DIVISION
LABORATORY 3
Geotechnical Engineering Laboratory [Consolidation Test]
D is the Diameter of the vane Suh /Suv is the ratio of the u ndrained strength in both vertical and horizontal planes. X is the factor describing the the location of the failure surface with respect respect to diameter of the vane . n is the power law describing the shear stress distribution on the horizontal planes.
Advantages and Disadvantages: Advantages:
The test is simple and quick. It is ideally suited for the determination of the undrained shear strength of non-fissured fully saturated clay. The test can be conveniently used to determine the sensitivity of the soil. The test can be conducted in soft clays situated at a great depth, samples of which are difficult to obtain. Disadvantages:
The test cannot be conducted on the clay containing sand or silt laminations or the fissured clay. The test does not give accurate results when the failure envelope is not horizontal.
Vane shear test is used to measure the shear strength of a soil. It also estimated and measured the fully saturated clay’s undrained shear strength without derangement in the
specimen. This test can be conducted in field and laboratory however, in labor atory can only execute the experiment with low shear strength (0.3 kg/cm2) for which unconfined test cannot be performed. The test apparatus are composed of 3 different diameters of 4 -blade stainless vane that is attached in a steel rod that pushed vertically in the soil. The pocket value that can get in small vane should multiply by two however, the value can get in large vane should divide by two and the value v alue that can get in medium vane is as it is. The test is performed by pushing the vane vertically in the soil and rotated it clockwise from the surface to determine the torsional force. The soil will resist the rotation of the vane and its resistance is the force of soil that causes the cylindrical area to be sheared by the vane. When the rotation of the vane is continues it means that the soil fails in shear and it is normal that the rotation is continued after measuring the shear strength . SAYED ASADULLAH
UNISEL, FACULTY OF ENGINEERING, CIVIL DIVISION
LABORATORY 3
Geotechnical Engineering Laboratory [Consolidation Test]
1. Mr. Khatta Marwah, Laboratory Sheet, 2014, 2014 , UNISEL, Civil Engineering Department. 2. Braja M Das, Fundamentals of Geotechnical Engineering. 3. ASTM Standards, 2002, copyright ASTM International, 100 Barr Hrbor Drive. 4. Roy Whitlow, Basic Soil Mechanics.
Appendix A:
Figure 6; Vane Apparatus
Figure 7; Top View of the Vane & Spring Deflection Scale
Figure 5 ; Calibrated Spring Supplied
SAYED ASADULLAH
UNISEL, FACULTY OF ENGINEERING, CIVIL DIVISION
