A cut slope was excavated in saturated clay for installation of water piping system. The angle Bof cut slope is 45° with the horizontal. During excavation works, slope failure was occurred when the cut reached a depth of 4.0 m. Previous soil explorations showed that a hard layer was located at a depth of 6 m below the ground surface. The unit weight of saturated clay is 17.5 kN/m. (Assuming an undrained condition). a) Determine the undrained cohesion of the clay. b) Determine Factor of Safety (FoS) if the depth of cut slope is 3m. What is the maximum depth of saturated clay can be exeavated if the Factor of Safety (FoS) 1.4 to be implemented? c)

A cut slope was excavated in saturated clay for installation of water piping system. The angle Bof cut slope is 45° with the horizontal. During excavation works, slope failure was occurred when the cut reached a depth of 4.0 m. Previous soil explorations showed that a hard layer was located at a depth of 6 m below the ground surface. The unit weight of saturated clay is 17.5 kN/m. (Assuming an undrained condition). a) Determine the undrained cohesion of the clay. b) Determine Factor of Safety (FoS) if the depth of cut slope is 3m. What is the maximum depth of saturated clay can be exeavated if the Factor of Safety (FoS) 1.4 to be implemented? c)

Fundamentals of Geotechnical Engineering (MindTap Course List)

5th Edition

ISBN:9781305635180

Author:Braja M. Das, Nagaratnam Sivakugan

Publisher:Braja M. Das, Nagaratnam Sivakugan

Chapter17: Settlement Of Shallow Foundations

Section: Chapter Questions

Problem 17.15P: A shallow square foundation for a column is to be constructed. It must carry a net vertical load of...

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A vertical cut is to be made in a purely cohesive clay deposit (c'=30kPa, φ'=0deg, γ=16kN/m3). Find the maximum height of the cut which can be temporarily supported. From the stability chart, the stability number can be used as 0.261.
A braced cut is carried out to 10 m depth at a site where the soil consists of 4 m of sand ( = 17.0 kN/m3, = 33) at the top underlain by 6 m of clay ( = 18.5 kN/m3, c = 35 kN/m2). a. What would be the average value of cohesion and the unit weight for the equivalent homogeneous soil profile? b. Show the lateral earth pressure envelope you would use in determining the strut loads.
(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?
Q.4 A 40° slope is excavated to a depth of 8 m in a deep layer of saturated clay having strength parameters c = 60 kN/m2 , Ø = 0, and ɣ = 19 kN/m3 . Determine the factor of safety for the trial failure surface shown in Fig. 4
If a soil has a Swell Factor of 1.5, then 10 m3 of banked soil when excavated will have 15 m3 in the loose state.a) TRUEb) FALSE
A 9m cut slope is shown in the figure. The unit weight of soil is 17kN/m3. Friction angle and cohesion along the rock surface are 20 degrees and 24kPa respectively. The slope makes an angle of 300 from horizontal and the failure plane is at 150. Determine the developed frictional force on the failure plane.
A wide excavation is made on a site which has the following soil conditions: 0-2 m Gravel: gsat = 21.8 kN/m3, gdry = 18.5 kN/m3 2-6 m Silty sand: gsat = 19.6 kN/m3, gdry = 18.4 kN/m3 6-21 m Heavy Clay: gt = 20 kN/m3 21 m and below: PERVIOUS sandstone The water table is at a depth of 1.5 m below the ground level. The piezometric pressure head at the top of the pervious sandstone is 5 m above the ground surface. If an excavation of depth 10 m is required, and a factor of safety of 1.5 against heave at the bottom of the clay layer is set, calculate the pressure head reduction required in sandstone.
A 6m high vertical retaining wall is used to retain a soil of unit weight 18 kN/m3 and slope 20°. The soil is a cohesionless soil with internal friction angle of 40°. Compute the coefficient of active earth pressure from the given data.
A shallow square foundation for a column is to be constructed. It must carry a net vertical load of 1000 kN. The soil supporting the foundation is sand. The standard penetration numbers (N60) obtained from field exploration are as follows: FIG. 17.15 The groundwater table is located at a depth of 12 m. The unit weight of soil above the water table is 15.7 kN/m3, and the saturated unit weight of soil below the water table is 18.8 kN/m3. Assume that the depth of the foundation will be 1.5 m and the tolerable settlement is 25 mm. Determine the size of the foundation.
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.
Q.3. 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 = 19 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?
A soil excavation was done until 4m below the surface of the soil. It was identified that the shallow ground water level is 2m below the ground level and the upper is dry. The properties of the soil are: Gs = 2.7, e = 0.50, and ϕ’ = 30degrees. Assuming no seepage. What is the value of the in-situ soil’s unit weight above G.W.T. in kN/m3? What is the maximum neutral stress at the deepest point of excavation in kPa? What is the value of the total stress of soil at the surface of the ground water table in kPa? What is the value of the effective stress at the deepest point of excavation in kPa?