Principles of Foundation Engineering (MindTap Course List)
9th Edition
ISBN: 9781337705028
Author: Braja M. Das, Nagaratnam Sivakugan
Publisher: Cengage Learning
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Chapter 2, Problem 2.10P
The soil profile at a site consists of 10 m of gravelly sand underlain by a soft clay layer. The water table lies 1 m below the ground level. The moist and saturated unit weights of the gravelly sand are 17.0 kN/m3 and 20.0 kN/m3, respectively. Due to some ongoing construction work, it is proposed to lower the water table to 3 m below the ground level. What will be the change in the effective stress on top of the soft clay layer?
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A sediment settling lagoon has a depth of water of 4 m above the clay base. The clay layer is 3 m thick and this overlies 4 m of medium sand, which in turn overlies impermeable rock. Given the unit weight of clay, medium sand and sediment of silty fine sand is 18 kN/m², 20 kN/m³ and 16 kN/m², respectively. Calculate the effective stress at the top of the clay and at the top and bottom of the second layer under the following condition;
i) initial, before any sediment is deposited.
ii) After a 2m layer of sediment of silty fine sand has been deposited.
iii) After draining the lagoon down to base level, with the same thickness (2m) of sediment still in place
A river is 3 m deep with the riverbed consisting of a thick bed of sand having a saturated unit weight of 19.0 kN/m3. What would be the effective vertical stress at 4 m below the riverbed? If the water level rises by 2 m, what would be the new effective vertical stress at 4 m below the riverbed? If the water level drops by 2 m, what would be the new effective vertical stress at 4 m below the riverbed?
A clay formation having a depth of 4 m. underlies a sand formation having a depth of 3 m. The dry unit weight of sand is 16.5 kN/m3 and the saturated unit weights of clay and sand are 20.4 kN/m3 and 19.6 kN/m3 respectively. The groundwater table is at the interface of the sand and clay. Compute the effective stress in kPa at the bottom of the clay if water rises 2 m. above the ground surface.
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Principles of Foundation Engineering (MindTap Course List)
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- The soil profile at a site consists of 10 m of gravelly sand underlain by a soft clay layer. The water table lies 1 m below the ground level. The moist and saturated unit weights of the gravelly sand are 17.0 kN/m3 and 20.0 kN/m3, respectively. Due to some ongoing construction work, it is proposed to lower the water table to 3 m below the ground level. What will be the change in the effective stress on top of the soft clay layer?arrow_forwardA river is 2 m deep. The riverbed consists of a depth of sand of saturated unit weight of 20 kN/m3. What is the effective vertical stress 5 m below the top of the sand? If the water level is raised by 1 m, what would be the new effectivevertical stress?arrow_forwardA uniform soil deposit has a dry unit weight of 15.6 kN/m³ and a saturated unit weight of 17.2 kN/m³. The groundwater table is at a distance of 4 m below the ground surface. Point A is at a depth of 6 m below the ground surface. If the water table rises by 3.5 m, determine the change in effective stress at A. Indicate if it is maintained, increased or decreased.arrow_forward
- A saturated clay layer has a thickness of 10 meters with a water content of 51% and a specific gravity 2.72. Determine the following: 1. Saturated unit weight of the clay * a. 21.46 kN/m³ b. 18.12 kN/m³ c. 16.87 kN/m³ d. 14.95 kN/m³ 2. total stress at depth of 10 meters a. 122.1 kPa b. 151.3 kPa c. 168.7 kPa d. 142.5 kPa 3. Effective stress at depth of 10 meters a. 42.1 kPa b. 70.6 kPa c. 68.7 kPa d. 82.5 kPaarrow_forwardIn an area where the ground surface is level, the underlying soil has a unit weight of 16 kN/m3. Determine the principal stresses acting at a depth of 5 m if the lateral pressure is one-half the vertical. The vertical pressure (stress) is the product of the soil unit weight and depth, and is the major principal stress.arrow_forwardEffective Stress in Soil Problem 1. The water table in a certain deposit of soil is at a depth of 2m below the ground surface. The soil consists of clay up to depth of 4m from the ground and below which lies sand. The clay soil is saturated even above the water table: Clay strata: ? = 30%,?? = 2.72 Sandy Strata: ? = 26%, ?? = 2.64 1. Compute the total pressure. 2. Compute the pore water pressure. 3. Compute the effective stress pressure at a depth of 8m below the ground surfacearrow_forward
- A soil stratum has two layers a 4m-thick dry sand underlain by a 5m–thick saturated sand. Dry unitweight and saturated unit weight of sand are respectively 16.21 KN/m3 and 20.88 KN/m3. a. What is the total stress at the bottom of the soil stratum?arrow_forwardA soil profile consists of a sand layer underlain by a clay layer, as shown. If the degree of saturation of the sand above water table was 50%. Saturated and dry unit weight of sand are 21.2 kN/m^3 and 18.22 kN/m^3 respectively. The saturated unit weight of clay is 18 kN/m3. Determine the total stress, pore pressure and effective stress at point A,B,C.arrow_forwardIn a clayey sandy silt deposit, the water table is 3.5 m below the surface, but the sand to a height of 1.5 m above the water table is saturated by capillary water. The top 2 m of sand can be assumed to be dry. The saturated and dry unit weights of the soil are 19.5 kN/m^3 and 18.0 kN/m^3, respectively. Calculate the effective vertical stress at 8 m below the surface. Express answers in kPa rounded to the first decimal place.arrow_forward
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