- Use X 7 If Needed 1 (53.87 KiB) Viewed 31 times
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Sand (1+0.X) m Gravity wall (2+0.X) m Figure 2 for Question 2 3 m 4 m 2 m Backfill Sand
Use X = 7 if needed.
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answerhappygod
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Use X = 7 if needed.
Use X = 7 if needed.
Question 2 Figure 2 (given in the next page) shows a mass concrete retaining wall. The wall is cast into the foundation soil (sand) to a depth of 2 m and retains a backfill to a height of 4 m. The soil properties of the sand and backfill are listed in Table 2. A surcharge of (15+X) kPa acts on top of the retained backfill (see Figure 2). Table 2: Soil properties Soil layer Depth Unit Critical angle Soil/wall of friction Cohesion (kPa) (m) weight interface friction (kN/m³) (degrees) 30 angle (degrees) Backfill 0-4 (17.5+0.X) 0.67-p' 0 Sand >4 (19.5+0.X) 32 0.67-p' 0 Assuming the unit weight of concrete is 24 kN/m³ and the water table is 20m below the ground surface, answer the following questions: a) Calculate the lateral pressures behind and in front of the wall and plot their distribution with depth. (10 marks) b) Calculate the factor of safety against overturning. Comment on the wall stability. (12 marks) c) Calculate the factor of safety against sliding. Comment on the wall stability. (8 marks) d) Explain the additional considerations that a designer should make if the water table rose to the ground surface behind the retaining wall (on the retained side). What changes in the design of the wall would you suggest in order to increase its stability? (6 marks)
Sand (1+0.X) m Gravity wall (2+0.X) m Figure 2 for Question 2 3 m 4 m 2 m Backfill Sand
Question 2 Figure 2 (given in the next page) shows a mass concrete retaining wall. The wall is cast into the foundation soil (sand) to a depth of 2 m and retains a backfill to a height of 4 m. The soil properties of the sand and backfill are listed in Table 2. A surcharge of (15+X) kPa acts on top of the retained backfill (see Figure 2). Table 2: Soil properties Soil layer Depth Unit Critical angle Soil/wall of friction Cohesion (kPa) (m) weight interface friction (kN/m³) (degrees) 30 angle (degrees) Backfill 0-4 (17.5+0.X) 0.67-p' 0 Sand >4 (19.5+0.X) 32 0.67-p' 0 Assuming the unit weight of concrete is 24 kN/m³ and the water table is 20m below the ground surface, answer the following questions: a) Calculate the lateral pressures behind and in front of the wall and plot their distribution with depth. (10 marks) b) Calculate the factor of safety against overturning. Comment on the wall stability. (12 marks) c) Calculate the factor of safety against sliding. Comment on the wall stability. (8 marks) d) Explain the additional considerations that a designer should make if the water table rose to the ground surface behind the retaining wall (on the retained side). What changes in the design of the wall would you suggest in order to increase its stability? (6 marks)
Sand (1+0.X) m Gravity wall (2+0.X) m Figure 2 for Question 2 3 m 4 m 2 m Backfill Sand