Answered: Refer to the soil profile shown in…

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 7.4

An exploratory drill hole was made in a stiff saturated clay (see Figure 7.21). The sand lay
underlying the clay was observed to be under artesian pressure. Water in the drill hole rose t
height of 18 ft above the top of the sand layer. If an open excavation is to be made in the cl
how deep can the excavation proceed before the bottom heaves?
7.8
e = 0.49
G, = 2.68
15 ft
Groundwater table
12 ft
e = 0.9
G, = 2.75
O Dry Sand N Clay
Figure 7.20
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Transcribed Image Text:7.2 through to Figure cases and plot the variations with depth. (ote: y. weight.) dry unit weight, and y= saturated unit Detalls of soll layer Problem II 7.2 H, = 2 ft H, 118 lb/ft = 4 ft H, = 6 ft %3D Ya = 115 lb/ft Ysat = Yzat = 130 Ib/ft 7.3 H, = 9 ft Ya 100 lb/ft H, = 21 ft 122 lb/ft H, = 36 ft 128 lb/ft %3D Ysat Yint 7.4 Refer to the soil profile shown in Figure 7.20 a. Calculate and plot the variation of o, u, and or' 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 lbft 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 1 m below the ground level. The moist and saturated unit weights of the grav- elly sand are 17.0 kN/m and 20.0 kN/m. respectively. Due to some ongoing construction work, it is proposed to lower the water table to 3 m below the ground level. What will be the change in the effective stress on top of the soft clay layer? 76 Ibr The depth of water in a lake is 4 m. The soil at the bottom of the lake consists of sandy clay. The moisture content of the soil was determined to be 25.0%. The specific gravity of the soil

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