Principles of Geotechnical Engineering (MindTap Course List)
9th Edition
ISBN: 9781305970939
Author: Braja M. Das, Khaled Sobhan
Publisher: Cengage Learning
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Question
Chapter 15, Problem 15.20P
(a)
To determine
Find the undrained cohesion
(b)
To determine
Find the nature of the critical circle.
(c)
To determine
Find the distance that the surface of sliding intersects the bottom of the excavation.
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(Note:Depth of rock layer is 2m not 12 m.)
Q A cut slope was excavated in a saturated clay with a slope angle β = 57 ͦ with the horizontal. Slope failure occurred when the cut reached a depth of 8 m. Previous soil explorations showed that a rock layer was located at a depth of 2 m below the ground surface. Assuming an undrained condition and that ɣsat = 21 kN/m3 : Determine the undrained cohesion of the clay (Fig 3). What was the nature of the critical circle? With reference to the top of the slope, at what distance did the surface of the sliding intersect the bottom of the excavation?
3.25 In a site consisting entirely of clays, an electric friction cone
penetrometer measures the cone resistance q, at a depth of
8.0 m as 0.75 MN/m2. The water table is at 3.0 m below the
ground level. The unit weights of the clay above and below
the water table are 16.5 kN/m3 and 19.0 kN/m2, respectively.
Estimate the undrained shear strength, preconsolidation
pressure, and overconsolidation ratio at this depth.
Compute the angle of internal friction. The results of a three consolidated undrained tri-axial test on saturated clay are as follows: a. 15.03°b. 12.06°c. 18.40°d. 31.05°
Chapter 15 Solutions
Principles of Geotechnical Engineering (MindTap Course List)
Ch. 15 - Prob. 15.1PCh. 15 - Prob. 15.2PCh. 15 - Prob. 15.3PCh. 15 - Prob. 15.4PCh. 15 - Prob. 15.5PCh. 15 - Prob. 15.6PCh. 15 - Prob. 15.7PCh. 15 - Prob. 15.8PCh. 15 - Prob. 15.9PCh. 15 - Prob. 15.10P
Ch. 15 - Prob. 15.11PCh. 15 - Prob. 15.12PCh. 15 - Prob. 15.13PCh. 15 - Prob. 15.14PCh. 15 - Prob. 15.15PCh. 15 - Prob. 15.16PCh. 15 - Prob. 15.17PCh. 15 - Prob. 15.18PCh. 15 - Prob. 15.19PCh. 15 - Prob. 15.20PCh. 15 - Prob. 15.21PCh. 15 - Prob. 15.22PCh. 15 - Prob. 15.23PCh. 15 - Prob. 15.27PCh. 15 - Prob. 15.28PCh. 15 - Prob. 15.29PCh. 15 - Prob. 15.30PCh. 15 - Prob. 15.31PCh. 15 - Prob. 15.32P
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Similar questions
- For the fully saturated clay layer depicted below, calculate the undrained shear strength in kPa of the clay layer if the factor of safety against failure is equal to 1.2 for short-term stability. Hint: use a simplified chart-based approach. (Acceptable tolerance = 10%) 10 m 10 m 12° WT ▼ Homogeneous clay Ysat = 19 kN/m³ Bedrock wwwarrow_forwardAn embankment consists of clay fill for which c′ = 25 kN/m2 and φ = 27° (from consolidated undrained tests with pore-pressure measurement). The average bulk unit-weight of the fill is 2 Mg/m3. Estimate the shear-strength in kPa of the material on a horizontal plane at a point 20 m below the surface of the embankment, if the pore pressure at this point is 180 kN/m2 as shown by a piezometer.arrow_forwardCompute the cohesion of the clay. The results of a three consolidated undrained tri-axial tests on a saturated clay are as follows : a. 10.45 kPab. 12.25 kPac. 11.62 kPad. 15.62 kPaarrow_forward
- In a tri-axial test for a normally consolidated soil, the deviator stress is equal to 700 kPa and the angle of failure plane makes with the major principal plane is equal to 60 degrees. Determine the shearing stress at the failure plane. a. 285.57 kPa b. 327.15 kPa c. 346.12 kPa d. 303.11 kPaarrow_forward10.24 A road embankment is being placed across a shallow section of a bay. The existing profile consists of 1 m of water over a 5-m thick normally consolidated clay soil which overlies a very dense and stiff gravelly sand. A consolidation test on the clay generated the follow- ing results: C = 0.21, e0 = 1.21. The embankment material is expected to be place at a unit weight of 18.1 kN/m³. Determine the thickness of the embankment such that the final elevation of the embankment is 2 m above the water level. This will require an iterative 10. solution.arrow_forwardT2arrow_forward
- An unconfined cylindrical specimen of clay fails under an axial stress of 240 kN/m. The failure plane was inclined at an angle of 35° to the vertical. The cohesion of the soil is a. 84 kN/m² b. 74 kN/m² c. 172 kN/m² d. 98 kN/m²arrow_forwardSoil Mechanics An embankment consists of clay fill for which c′ = 25 kN/m2 and φ = 27° (from consolidated undrained tests with pore-pressure measurement). The average bulk unit-weight of the fill is 2 Mg/m3. Estimate the shear-strength in kPa of the material on a horizontal plane at a point 20 m below the surface of the embankment, if the pore pressure at this point is 180 kN/m2 as shown by a piezometer. a. 133 b. 100 c. 166 d. 200arrow_forwardA clean rock discontinuity is dipping towards a slope face. The basic friction angle of the rock is 38 degrees. The discontinuity has a Joint Compressive Strength of 10 MPa and the Joint Roughness Coefficient of 10. If the average normal stress along the entire stretch of the discontinuity is 200 kPa, estimate the average shear strength along the discotinuity using Barton's approach. a) 252.3 kPa b) 324.9 kPa c) 285.5 kPa d) 82.4 kPaarrow_forward
- The stresses on a failure plane in a drained test on a cohesionless soil are as given below: Normal stress, o = 100 kN/m2, Shear stress = 57.73 kN/m2 The failure plane makes an angle of B with the minor principle plane. The value of B will bearrow_forward(Derive the Rankine active earth pressure of a soil at a depth of z using Mohr Circles, and failure envelope when the retaining wall has horizontal ground surface and the unit weight, cohesion, and internal friction angle of the soils are 7, c, and ø. In addition, what is the maximum depth of tensile crack at the retaining clay when Y =15.72kN/m³, cu=6.77kN/m² 9 and ø=30°) Ir 10000arrow_forwardA cut slope was excavated in sand. The slope is shown in following attachment . To find the properties of the sand, representative samples were taken for the soil and tested in atriaxial apparatus. A consolidated drained triaxial test was conducted. The result is given below:Chamber pressure = 103 kN/m2Deviator stress at failure = 234.6 kN/m2We know the unit weight of the sand is 16 kN/m3.Use the ordinary method of slices (use 7 slices) and estimate the factor of safety against sliding forshown slip surface and comment on the calculated factor of safety.Please note that:1. The figure is not in scale. You may resketch it in scale and calculate the factor of safety2. The slip surface is circular and passes through the toe of the embankmentarrow_forward
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