Concept explainers
(a)
Check whether the statement “In a soil, the effective stress can be greater or less than the pore water pressure” is true or false.
(a)
Answer to Problem 8.1P
The given statement is true.
Explanation of Solution
The clay has low hydraulic conductivity and the compressibility is high. The capillary pressure will occur in this condition. The pore water pressure in this condition is greater than the effective stress.
The hydraulic conductivity for the sand is high. The water will be squeezed out easily. The pore water pressure will be less than the effective stress.
Therefore, the given statement is true.
(b)
Check whether the statement “Upward seepage increases the effective stresses and downward seepage decreases the effective stresses” is true or false.
(b)
Answer to Problem 8.1P
The given statement is false.
Explanation of Solution
Write the equation for effective stress in upward seepage condition as follows:
Refer to the upward seepage concept, when the seepage is upward, the effective stress decreases and the pore water pressure increases.
Write the equation for effective stress in downward seepage condition as follows:
Refer to the downward seepage concept, when the seepage is downward, the effective stress increases and the pore water pressure decreases.
Therefore, the given statement is false.
(c)
Check whether the statement “Quick condition cannot occur when the seepage is downward” is true or false.
(c)
Answer to Problem 8.1P
The given statement is true.
Explanation of Solution
Write the equation for effective stress in upward seepage condition as follows:
When the upward seepage pressure is equal to submerged weight of soil, the effective pressure is equal to zero. i.e.,
This condition is only possible in upward seepage.
Write the equation for effective stress in downward seepage condition as follows:
In downward seepage condition it is not possible that, the downward seepage pressure is equal to submerged weight of soil.
Therefore, the given statement is true.
(d)
Check whether the statement “Seepage force does not depend on the permeability of the soil” is true or false.
(d)
Answer to Problem 8.1P
The given statement is true.
Explanation of Solution
Write the equation to find the seepage force
Here, the thickness of the soil is z, the submerged unit weight is
Refer to the equation, the seepage force is independent of the permeability of the soil.
Therefore, the given statement is true.
(e)
Check whether the statement “Critical hydraulic gradient is greater for loose sands than dense sands” is true or false.
(e)
Answer to Problem 8.1P
The given statement is false.
Explanation of Solution
Critical hydraulic gradient occurs in the upward seepage condition.
When the soil pores are dense, the possibility of occurring the quick sand condition is high. This is due to the spacing between the particles are very less.
Therefore, the given statement is false.
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Chapter 8 Solutions
Fundamentals of Geotechnical Engineering (MindTap Course List)
- sand layer 5m thick is underlain with a thick layer of clay. the sand has a void ratio of 0.52 and specific gravity 2.64. The clay has a water content of 42% and specific gravity of 2.64. The ground water table is located 3 m below the ground surface. The sand above the water table is 30% saturated. a.) Determine the unit weight of the clay b.) Determine the total stress at a depth of 10 m below the ground surface. c.) Determine the effective stress at a depth of 10m below the ground surface.arrow_forwardneed fast please A soil profile consists of sand (6-m thick) which overlies a layer of clay (6-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 = 0.88, Specific gravity = 2.75, Degree of Saturation = 0.79 For clay layer: Void Ratio = 0.99, Specific gravity = 2.86 Round off to two decimal places.arrow_forwardA layer of soil has the following properties: void ratio = 0.44, effective diameter = 12 μm, capillary constant C = 0.18 cm2 . Groundwater table is 10 m below the ground surface. (a) Find the height of capillary rise in the soil in mm. (b) What is the effective stress in kPa at 7 m depth if unit weight of solids is 25.55 kN/m3 and soil above the capillary zone is 40 % saturated? (c) What is the effective stress in kPa at 14 m depth?arrow_forward
- Dry Sand H Groundwater Table Clay H, Refer to the soil profile shown. Given H1 = 9.46 m., and H2 = 4.79 m. If the ground water table rises by 2.58 meters, determine the change in effective stress (numerical value only, in kPa) at the bottom of the clay layer. Properties of dry sand: Gs = 2.57, e = 0.63. Properties of clay: Gs = 2.74, e = 0.88. Round off to two decimal places.arrow_forwardA ground profile consists of 2m silty sand underlain by 3m of clay. The ground water table is 3m below the ground surface. The sand has a unit weight of 14kN/cum. The clay has a unit weight of 16kN/cum above the water table and 20kN/cum below the water table. Determine the Total stress at the surface of the water table (kPa). Determine the effective stress at the bottom of the clay layer (kPa). Determine the effective stress 1m from the bottom of the clay layer (kPa). Please answer this asap. For upvote. Thank you very mucharrow_forwardA soil profile consists of sand (6-m thick) which overlies a layer of clay (5-m thick). The groundwater 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 = 0.72, Specific gravity = 2.61, Degree of Saturation = 0.6 For clay layer: Void Ratio = 0.99, Specific gravity = 2.72 Round off to two decimal places.arrow_forward
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- The ground water table in a deep deposit of sand is located at 4 m from the ground level. Due to capillary action, sand is saturated for a height of 1 m from the water table. The degree of saturation of the sand above the capillary fringe is 40%. If the specific gravity of solids and average void ratio of the sand are 2.68 and 0.72 respectively. Determine the effective stress (in kPa) at 4 m and 10 m from the ground level. Consider the standard value for unit weight of water.arrow_forwardgeotech. engineering A Thick layer of clay underlies a sand formation having a thickness of 4m. the groundwater is located 2m below the ground surface. The specific gravity of sand and clay is 2.65 with sand having an average void ratio of 0.52. the clay has a water content of 42%. Degree of saturation above the water table is 0.37. a. Compute the moist unit weight of the sand b. Total stress at a depth 10 m below the ground surface c. Effective stress at a depth of 10 m below the ground surfacearrow_forwardQuestion 33 Dry Sand H, Groundwater Table Clay H, Refer to the soil profile shown. Given H1 = 9.89 m., and H2 = 5.8 m. If the ground water table rises by 3.78 meters, determine the change in effective stress (numerical value only, in kPa) at the bottom of the clay layer. Properties of dry sand: Gs = 2.53, e = 0.63. Properties of clay: Gs = 2.75, e = 0.81. Round off to two decimal places.arrow_forward
- Fundamentals of Geotechnical Engineering (MindTap...Civil EngineeringISBN:9781305635180Author:Braja M. Das, Nagaratnam SivakuganPublisher:Cengage Learning