(a)
Find the change in effective stress
(a)
Answer to Problem 9.4P
The change in effective stress at point C when the water table drops by 2 m is
Explanation of Solution
Given information:
The thickness
The thickness
The thickness
The void ratio (e) of soil in the first layer is 0.7.
The specific gravity
The void ratio (e) of soil in the second layer is 0.55.
The depth (h) of water table drop is 2 m.
Calculation:
Determine the dry unit weight
Here,
Take the unit weight of the water as
Substitute 2.69 for
Determine the dry unit weight
Substitute 2.7 for
Determine the saturated unit weight
Substitute
Calculate the total stress at point C (13 m) using the relation.
Substitute
Calculate the pore water pressure at point C (13 m) using the relation.
Substitute
Calculate the effective stress at point C (13 m) using the relation.
Substitute
Water table drops by 2 m:
Calculate the total stress at point C when the water level drops by 2 m using the relation.
Substitute
Calculate the pore water pressure at point C when the water table drops by 2 m using the relation.
Substitute
Calculate the effective stress at point C when the water table drops by 2 m using the relation.
Substitute
Determine the change in effective stress when the water level drops by 2 m from the original position using the relation;
Substitute
Thus, the change in effective stress at point C when the water table drops by 2 m is
(b)
The change in effective stress
(b)
Answer to Problem 9.4P
The change in effective stress at point C rises to the surface up to point A is
Explanation of Solution
Given information:
The thickness
The thickness
The thickness
The void ratio (e) of soil in the first layer is 0.7.
The specific gravity
The void ratio (e) of soil in the second layer is 0.55.
Calculation:
Determine the saturated unit weight
Substitute
Calculate the total stress at point C (13 m) using the relation.
Substitute
Calculate the pore water pressure at point C (13 m) using the relation.
Substitute
Calculate the effective stress at point C (13 m) using the relation.
Substitute
Water table rises to the surface up to point A:
Determine the change in effective stress when the water table rises to the surface up to point A using the relation;
Substitute
Thus, the change in effective stress at point C rises to the surface up to point A is
(c)
Find the change in effective stress
(c)
Answer to Problem 9.4P
The change in effective stress at point C when the water level rises 3 m above point A due to flooding is
Explanation of Solution
Given information:
The thickness
The thickness
The thickness
The void ratio (e) of soil in the first layer is 0.7.
The specific gravity
The depth (h) of water rises above point A is 3.0 m.
Calculation:
Calculate the total stress at point C (16 m) using the relation.
Substitute
Calculate the pore water pressure at point C (16 m) using the relation.
Substitute
Calculate the effective stress at point C (16 m) using the relation.
Substitute
Water level rises 3 m above point A due to flooding:
Determine the change in effective stress when the water level rises 3 m above point A due to flooding using the relation;
Substitute
Thus, the change in effective stress at point C when the water level rises 3 m above point A due to flooding is
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Chapter 9 Solutions
MindTap Engineering for Das/Sobhan's Principles of Geotechnical Engineering, SI Edition, 9th Edition, [Instant Access], 2 terms (12 months)
- Refer to Figure 10.48. If R = 4 m and hw = height of water = 5 m, determine the vertical stress increases 2 m below the loaded area at radial distances where r = 0, 2, 4, 6, and 8 m. Circular contact area of radius R on the ground surface Figure 10.48arrow_forwardIV. A soil element is shown in Figure 3. (use equations) 130 kN/m² +35kN/m² 30⁰ 60 kN/m² 10 11. 12 + + B SITY FICAT 35 kN/m² Figure 3 What is the value of the maximum stress in kPa? What is the value of the normal stress acting at the plane AB in kPa? What is the value of the shear stress acting at the plane AB in kPa?arrow_forwardThe 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_forward
- Solve the following problems. Provide complete solutions and summary of answers. The water table in a 5-meter soil profile is located 1 meter below the ground. The soil above the water is also saturated due to capillary action. The saturated unit weight of the soil per cubic meter is 20.15 KN. What is the total effective stress acting at point A, which is 0.70 meter above the lowest point?arrow_forwardA soil profile is shown in figure below. Dry sand 6m Ydry = 16.5 kN/m³ B Groundwater table Saturated sand 13m Ysat = 19.25 kN/m² C Dry sand Saturated sand Clay Calculate the following: a. Effective stress at point A in kPa. b. Effective stress at point B in kPa. c. Effective stress at point C in kPa. 5.arrow_forwardA soil element is shown in the figure below. 128 kN/m2 32 kN/m 32 kN/m2 162 kN/m2 55 Determine the following: (in kPa) a. Maximum Principal Stress b. Minimum Principal Stress C. Normal Stress on plane AB d. Shear Stress on plane ABarrow_forward
- Plot the stress profile for total stress, effective stress and pore water pressure. Show all calculation A Diy sand 0,61 2.66 41 Salurated sand, =0.48° 2.67 Clayarrow_forwardA soil profile is shown in figure below. Calculate the following:a. Effective stress at point A in kPa.b. Effective stress at point B in kPa.c. Effective stress at point C in kPa.arrow_forwardFigure 2 shows the zone of capillary rise within a clay layer above the groundwater table. Using: H1 = 3 m., H2 = 2 m., H3 = 4 m. a.What is the value of the total stress 9m below the ground surface in kPa? b.What is the value of the effective stress 5m below the ground surface in kPa? c.What is the value of the effective stress 9m below the ground surface in kPa?arrow_forward
- The diagram below shows a multi-layered soil, write an expression for the stress at each layer and the vertical total stress at depth z. (all symbols have their usual meaning)arrow_forwardGround surface 2. The soil profile for a proposed construction site is shown. The groundwater table is located 2 m below the ground surface. Assume geostatic conditions and ignore any negative pore-water pressures due to capillary rise. Yt = 13.2 kN/m 2. Sand Ysat =? G, = 2.70 n= 0.5 (a) What is the effective stress (kPa) at point A? (Ans: 43 kPa) (b) What is the effective stress (kPa) at point B? (Ans: 82 kPa) (c) Ten years from now, the depth of the groundwater table will change, resulting in a new effective stress at point B of 72.6 kPa. Based on this information, how far below the ground surface will the new location of the groundwater table be? (Ans: 0 m; GWT is at the ground surface) A Clay Ysat = 19.6 kN/marrow_forwardEvaluate the figure shown and solve what is being asked in the problem with the following given: e = 0.42 G = 2.8 H1 = 0.3 m H2 = 3.3 m h1 = 0.9 m z = 1.2 m a. What is the saturated unit weight of sand in kN/m³? b. Calculate the total stress at point C in kPa. c. Calculate the effective stress at point B in kPa.arrow_forward
- Principles of Geotechnical Engineering (MindTap C...Civil EngineeringISBN:9781305970939Author:Braja M. Das, Khaled SobhanPublisher:Cengage LearningPrinciples of Foundation Engineering (MindTap Cou...Civil EngineeringISBN:9781305081550Author:Braja M. DasPublisher:Cengage Learning