Answered: 7.2 through 7.3 Refer to Figure 7.19.…

Structural Analysis

6th Edition

ISBN:9781337630931

Author:KASSIMALI, Aslam.

Publisher:KASSIMALI, Aslam.

Chapter2: Loads On Structures

Section: Chapter Questions

Problem 1P

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Question 7.2

hapter 7: Stresses in a Soil Mass
Layer I
Groundwater table
H2
Layer II
Layer III
ODry sand
Sand
Clay
E Rock
Figure 7.19
grains is 2.70. Determine the void ratio and the unit weight of the soil. What would ba
total stress, effective stress. and pore water pressure at a 5 m depth into the bottom of the I
If the water level in the lake in Problem 76 rises by 2 m. what would be the total stress,
water
and the c rtive sress at the same looation

Transcribed Image Text:obiems State whether the following are true or false. a. In dry soils, total stress is the same as the effective stress. b. Due to upward seepage, effective stress increases. c. During upward seepage, the larger the hydraulic gradient, the larger pore water pressure. d. Vertical stress increase due to surface load decays with depth. e. At quick condition, the effective stress becomes zero. 7.2 through 7.3 Refer to Figure 7.19. Calculate o, u, and o' at A, B, C, andD for the following cases and plot the variations with depth. (Note: y= dry unit weight, and Ysat = saturated unit weight.) 7.1 Detalls of soll layer Problem II II 7.2 H, = 2 ft H2 H, = 6 ft 130 lb/ft' = 4 ft Ya =115 lb/ft Yat = 118 lb/ft Ysat = 7.3 Н — 9 ft Ya= 100 lb/ft H, = 21 ft Ysat = 122 lb/ft' Н. — 36 ft Yat = 128 lb/ft' 7.4 Refer to the soil profile shown in Figure 7.20 a. Calculate and plot the variation of o, u, and o' with depth. b. If the water table rises to the top of the ground surface, what is the change in the effective stress at the bottom of the clay layer? C. How many feet must the groundwater table rise to decrease the effective stress by 300 lb/ at the bottom of the clay layer? 7.5 The soil profile at a site consists of 10 m of gravelly sand underlain by a soft clay layer. The water table lies I m below the ground level. The moist and saturated unit weights of the grav-

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