As shown in Figure 1, a long gravity retaining wall, 4 m high, with a fully smooth vertical back face, retains a flat cohesionless backfill with a uniform surcharge of 10 kN/m². During the dry season, the groundwater table drops far below the base of the wall, and the unit weight of the backfill equals its dry unit weight ya = 15.5 kN/m³. During the rainy season, however, the drain holes become clogged due to a poor design, and the groundwater table rises to the backfill surface and develops hydrostatic pressure behind the retaining wall, while the unit weight of the backfill equals its saturated unit weight sat 19.0 kN/m³. Herein, the unit weight of the retaining wall is y = 24.0 kN/m³, the unit weight of water is yw = 9.8 kN/m³, and the friction angle of the backfill is = 35°. According to Rankine's active earth pressure, answer the following questions. Note that the uplift force under the base of the retaining wall above the original ground can be neglected, and the soil parameters of the original ground are assumed to be the same as those of the cohesionless backfill. = 4 m 1 m 1 m Surcharge q = 10 kN/m² Groundwater table rose to the backfill surface = Yw 9.8 kN/m³ Retaining wall: Yc = 24 kN/m³ Clogged drain holes Cohesionless backfill Ya= 15.5 kN/m³ = Vsat 19.0 kN/m³ 0 = 35° Collector pipe 8=26/3 Original ground 2 m Groundwater table dropped far below the base of the wall Figure 1 (1) Calculate the resisting moment per unit length of the wall around point O, considering its top width of 1 m and base width of 2 m. (2) Calculate the total resultant force per unit length of the wall and the corresponding overturning moment per unit length of the wall about point O during the dry season. (3) Calculate the total resultant force per unit length of the wall and the corresponding overturning moment per unit length of the wall about point O during the rainy season. (4) Determine the safety factors against overturning for dry and rainy seasons. Later, after some filter material was utilized to prevent clogged drain holes, the groundwater table remained far below the base, even during the rainy season. Answer the extra questions below. (5) Check whether the eccentricity (e) is located within the middle third of the base. (6) Find the soil pressures at the toe and the heel. (7) Using the maximum soil pressure at the corner of the base, determine the safety factor against bearing capacity failure. Note that the general bearing capacity equation becomes 9'u = 0.5ya B'Ny where B' = B - 2е and N=48. и (8) Using the base's angle of shearing resistance 8 =², calculate the safety factor against sliding. (9) Discuss the importance of drainage systems in retaining walls from the viewpoint of their stability.

As shown in Figure 1, a long gravity retaining wall, 4 m high, with a fully smooth vertical back face, retains a flat cohesionless backfill with a uniform surcharge of 10 kN/m². During the dry season, the groundwater table drops far below the base of the wall, and the unit weight of the backfill equals its dry unit weight ya = 15.5 kN/m³. During the rainy season, however, the drain holes become clogged due to a poor design, and the groundwater table rises to the backfill surface and develops hydrostatic pressure behind the retaining wall, while the unit weight of the backfill equals its saturated unit weight sat 19.0 kN/m³. Herein, the unit weight of the retaining wall is y = 24.0 kN/m³, the unit weight of water is yw = 9.8 kN/m³, and the friction angle of the backfill is = 35°. According to Rankine's active earth pressure, answer the following questions. Note that the uplift force under the base of the retaining wall above the original ground can be neglected, and the soil parameters of the original ground are assumed to be the same as those of the cohesionless backfill. = 4 m 1 m 1 m Surcharge q = 10 kN/m² Groundwater table rose to the backfill surface = Yw 9.8 kN/m³ Retaining wall: Yc = 24 kN/m³ Clogged drain holes Cohesionless backfill Ya= 15.5 kN/m³ = Vsat 19.0 kN/m³ 0 = 35° Collector pipe 8=26/3 Original ground 2 m Groundwater table dropped far below the base of the wall Figure 1 (1) Calculate the resisting moment per unit length of the wall around point O, considering its top width of 1 m and base width of 2 m. (2) Calculate the total resultant force per unit length of the wall and the corresponding overturning moment per unit length of the wall about point O during the dry season. (3) Calculate the total resultant force per unit length of the wall and the corresponding overturning moment per unit length of the wall about point O during the rainy season. (4) Determine the safety factors against overturning for dry and rainy seasons. Later, after some filter material was utilized to prevent clogged drain holes, the groundwater table remained far below the base, even during the rainy season. Answer the extra questions below. (5) Check whether the eccentricity (e) is located within the middle third of the base. (6) Find the soil pressures at the toe and the heel. (7) Using the maximum soil pressure at the corner of the base, determine the safety factor against bearing capacity failure. Note that the general bearing capacity equation becomes 9'u = 0.5ya B'Ny where B' = B - 2е and N=48. и (8) Using the base's angle of shearing resistance 8 =², calculate the safety factor against sliding. (9) Discuss the importance of drainage systems in retaining walls from the viewpoint of their stability.

Principles of Foundation Engineering (MindTap Course List)

8th Edition

ISBN:9781305081550

Author:Braja M. Das

Publisher:Braja M. Das

Chapter15: Braced Cuts

Section: Chapter Questions

Problem 15.6P

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