Concept explainers
State whether the following are true or false.
- a. The higher the friction angle, the higher the value of K0.
- b. K0 is greater for normally consolidated clays than overconsolidated clays.
- c. Active earth pressure coefficient is greater than the passive one.
- d. The larger the cohesion, the larger is the depth of the tensile cracks in clays in active state.
- e. Lateral earth pressures increase linearly with depth.
(a)
Whether the statement “The higher the friction angle, the higher the value of
Answer to Problem 14.1P
The given statement is
Explanation of Solution
Write the equation of coefficient of earth pressure at rest
Here,
Find the coefficient of earth pressure at rest when
Substitute
Find the coefficient of earth pressure at rest when
Substitute
Tabulate the values of coefficient of earth pressure at rest with two different drained friction angles of
Drained friction angle, | Coefficient of earth pressure at rest, |
0.5 | |
0.134 |
Table 1
Refer Table 1.
The coefficient earth pressure at rest
Therefore, the given statement is
(b)
Whether the statement “
clays” is true or false.
Answer to Problem 14.1P
The given statement is
Explanation of Solution
The value of over consolidated ratio (OCR) is a whole number.
Write the relationship between earth pressure at rest for over consolidated clay
The multiplication of square root of over consolidated ratio (OCR) with earth pressure at rest for normal consolidated clay gives the earth pressure at rest for over consolidated clay. Hence, the value earth pressure at rest for over consolidated clay is greater than the earth pressure at rest for normal consolidated clay.
Therefore, the given statement is
(c)
Whether the statement “Active earth pressure coefficient is greater than the passive one” is true or false.
Answer to Problem 14.1P
The given statement is
Explanation of Solution
Write the equation of active earth pressure coefficient
Here,
Find the active earth pressure coefficient
Substitute
Write the equation of passive earth pressure coefficient
Substitute
Tabulate the values of active and passive earth pressure coefficients with corresponding friction angle of
Friction angle, | Active earth pressure coefficient, | Passive earth pressure coefficient, |
0.333 | 3 |
Refer Table 1.
The active earth pressure coefficient
Therefore, the given statement is
(d)
Whether the statement “The larger the cohesion, the larger is the depth of the tensile cracks in
clays in active state” is true or false.
Answer to Problem 14.1P
The given statement is
Explanation of Solution
Write the equation of depth of tensile crack
Here,
From Equation (4), cohesion
Therefore, the given statement is
(e)
Whether the statement “Lateral earth pressures increase linearly with depth” is true or false.
Answer to Problem 14.1P
The given statement is
Explanation of Solution
Write the equation of lateral earth pressure
Here,
The lateral earth pressure equation is a linear equation and the lateral earth pressure
Therefore, the given statement is
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Chapter 14 Solutions
Fundamentals of Geotechnical Engineering (MindTap Course List)
- The soil profile shown consists of dry sand (4-m thick) which overlies a layer of clay (3-m thick). Ground water table is located at the interface of the sand and clay. a. If the water table rises to the top of the ground surface, what is the change in the effective stress (in kPa) at the bottom of the clay layer? Round off to two decimal places. (ANSWER: 26.336) b. Compute the effective stress at the bottom of the clay layer in kPa. Round off to three decimal places (ANSWER: 97.686) c. How many meters must the ground water table rise to decrease the effective stress by 14 kPa, at the bottom of the clay layer? Round off to two decimal places (ANSWER: 2.13)arrow_forwardA soil profile consisting of three soil layers is shown. Assume: layer 1 as drysoil. Characteristics of the layers are: a=4 b=7 c=5 d=1 Determine:a.) The effective stress at Point Cb.) The maximum Neutral Stress at Point Darrow_forwardA normally consolidated clay is consolidated under a triaxial chamber confining pressure of σ = o'₁ = 495kN/m² and '= 29° (again for normally consolidated soil assume c' = 0). Calculate the axial stress and radial stress at failure for the following cases and draw the stress path in p'-q plane a. By increasing the axial stress and reducing the radial stress such that 20%, +0% = const. b. By reducing the axial stress and increasing the radial stress such that 2σ +σ = const .arrow_forward
- A vertical stress of 100 kPa is applied to a saturated clay, the excess pore water pressure (kPa) at t = 0 is 50 O 100arrow_forwardThe following figure is a layer of sand (γ s a t=130 lb/ft3 ) in a tank of water. If point C is located at the middle of the soil layer, what is the effective stress at point C: (a) when the valve is closed (there is no seepage) (b) when the valve is open (there is downward seepage)arrow_forward11. J The effective stress friction angle of a saturated, cohesionless soil is 38°. The ratio of shear stress to normal effective stress on the failure plane is (A) 0.781 (B) 0.616 (C) 0.488 (D) 0.438arrow_forward
- 3. [Mohr's Circle] (: ). For the stressed soil element shown below, determine a. Major Principal Stress in psi. b. Minor Principal Stress in psi. c. Normal Stress at Failure Plane AE in psi. d. Shear Stress at Failure Plane AE in psi. 150 psi 60 psi D. 90 psi 60 psi 45° A Barrow_forwardDetermine shear strength of clay having value of cohesion 31 KPa Normal stress 100 KPa and angle of internal is 31 degreearrow_forwardA 25 m thick layer of clay is underlain by a layer of silt, as shown in the Figure. 1. Determine the effective stress at point A when Z = 3 m. 2. Determine the effective stress at point B when h=3 m. 3. By changing h and Z, would you expect that the effective stresses at A and B can have the same value? wy Z 12 m B Clay e=0.6, G₁-2.69 Clay w=30% Silt w=50%, G,=2.70arrow_forward
- 2. The state plane stress in a mass of dense cohesionless sand (c=0) is described by the following stresses: Normal stress on horizontal plane = 100 kPa Normal stress on vertical plane = 50 kPa Shear stress on horizontal and vertical planes = ± 30 kPa Determine by means of the Mohr circle the magnitude and direction of the principal stresses. Is this state of stress safe against failure assuming φ= 30o?arrow_forwardA soil profile consists of sand (5-m thick) which overlies a layer of clay (4-m thick). Ground water table is located at the interface of the sand and clay. The effective stress at the bottom of the clay layer was determined. If the water table rises to the top of the ground surface, what is the change in the effective stress (in kPa) at the bottom of the clay layer? For sand layer: Void Ratio = 0.82, Specific gravity = 2.75, Degree of Saturation = 0.76 For clay layer: Void Ratio = 1.09, Specific gravity = 2.76arrow_forwardQuestion 20 A soil profile consists of sand (5-m thick) which overlies a layer of clay (9-m thick). Ground water table is located at the interface of the sand and clay. The effective stress at the bottom of the clay layer was determined. If the water table rises to the top of the ground surface, what is the change in the effective stress (in kPa) at the bottom of the clay layer? For sand layer: Void Ratio = 0.82, Specific gravity = 2.68, Degree of Saturation = 0.6 For clay layer: Void Ratio = 0.92, Specific gravity = 2.86 Round off to two decimal places.arrow_forward
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