Principles of Geotechnical Engineering (MindTap Course List)
9th Edition
ISBN: 9781305970939
Author: Braja M. Das, Khaled Sobhan
Publisher: Cengage Learning
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Chapter 9, Problem 9.7P
To determine
Find the safe depth of excavation before the bottom heaves.
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An exploratory drill hole was made in a stiff saturated clay (Gs = 2.72, and w = 35%). The sand layer underlying the clay was observed to be under artesian pressure. Water in the drill hole rose to a height of 12 ft above the top of the sand layer. If an open excavation is to be made in the clay, how deep can the excavation proceed before the bottom heaves?
An exploratory drill hole was made in a stiff saturated clay having a moisture content of 38.9% and Gs = 2.34 as shown in the figure. The sand layer underlying the clay was observed to be under artesian pressure. Water in the drill hole rose to a height of 13.8 ft above the top of sand layer. If an open excavation is to be made in the clay,
determine the
(a) unit weight of the clay, and the
(b) maximum cut before the bottom heaves.
A hole was made in a stiff saturated soil having a Gs = 2.71 and moisture content of 0.30. The sand layer underlying
the clay was observed to be under artesian pressure. Water in the drill hole rose to a height of 6.30 meters above the
top of the sand layer
%3D
Exploratory drill hole
10 m
6.3 m
4.5 m
Saturated clay L Sand
a. If an open excavation is to be made in the clay, determine the safe depth of excavation before the bottom
heaves. Round your final answer to three significant figures.
b. How much is the pressure at the interface of the clay and sand?
c. f a factor of safety of 2.0 is to be ensured, how deep should be the excavation from the ground surface?
Note: Draw Free Body Digram and show full solution
Topic: Soil Stresses (Soil Mechanics_
Chapter 9 Solutions
Principles of Geotechnical Engineering (MindTap Course List)
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- 9.7 An exploratory drill hole was made in a stiff saturated clay having a moisture content of 29% and G, = 2.68 (Figure 9.27). The sand layer underlying the clay was observed to be under artesian pressure. Water in the drill hole rose to a height of 6 m above the top of the sand layer. If an open excavation is to be made in the clay, determine the safe depth of excavation before the bottom heaves. Exploratory drill hole 10 m 45 m Saturated clay Sand Figure 9.27arrow_forwardAn exploratory drill hole was made in a stiff saturated clay having a moisture content of 29% and Gs = 2.68 (Figure 9.27). The sand layer underlying the clay was observed to be under artesian pressure. Water in the drill hole rose to a height of 6 m above the top of the sand layer. If an open excavation is to be made in the clay, determine the safe depth of excavation before the bottom heaves.arrow_forward4.An exploratory drill hole was made in a stiff saturated clay having a moisture content of 22% and Gs = 2.82 as shown in Figure 1.3. The sand layer underlying the clay was observed to be under artesian pressure. Water in the drill hole rose to a height of 8 m above the top of sand layer. If an open excavation is to be made in the clay, determine: a. The maximum depth of excavation before the bottom heaves. b. What would be the required height of water inside the cut in order to ensure a factor of safety of 2? Exploratory drill hole 12m 8m 4.5 m Saturated clay O Sand Figure 1.3.arrow_forward
- An exploratory drill hole was made in a stiff saturated clay, as shown in Figure 1, having a moisture content of 25% and Gs = 2.56. The sand layer underlying the clay was observed to be under artesian pressure. Water in the drill hole rose to a height of 3 m above the top of sand layer. If an open excavation is to be made in the clay. a.What is the maximum depth of excavation before the bottom heaves? b.What would be the required height of water inside the cut in order to ensure a factor of safety of 1.5?arrow_forwardAn exploratory drill hole was made in a stiff saturated clay having a moisture content of 29% and G, = 2.68 (Figure 9.27). The sand layer underlying the clay was observed to be under artesian pressure. Water in the drill hole rose to a height of 6 m above the top of the sand layer. a. If an open excavation is to be made in the clay, determine the safe depth of excavation before the bottom heaves. b. How much is the pressure at the interface of the clay and sand? c. If a factor of safety of 2.0 is to be ensured, how deep should be the excavation from the ground surface?arrow_forwardAn exploratory drill hole was made in a stiff saturated clay (see Figure 9.9). The sand layer underlying the clay was observed to be under artesian pressure. Water in the drill hole rose to a height of 4 m above the top of the sand layer. If an open excavation is to be made in the clay, how deep can the excavation proceed before the bottom heaves? Exploratory drill hole G,= 2.72 Moisture content =w= 35% 6.1 m 4. 4 m Saturated clay Sandarrow_forward
- Exploratory drill hole 12m 8m 4.5 m An exploratory drill hole was made in a stiff saturated clay having a moisture content of 22% and Gs = 2.16 as shown in Figure. The sand layer underlying the clay was observed to be under artesian pressure. Water in the drill hole rose to a height of 8 m above the top of sand layer. If an open excavation is to be made in the clay, determine: a. The maximum depth of excavation before the bottom heaves. b. What would be the required height of water inside the cut in order to ensure a factor of safety of 2.1?arrow_forward8. An exploratory drill hole was made in a saturated stiff clay having a water content of 32%. It was observed that the sand layer underlying the clay was under artesian pressure water in the drill hole rose to a height of 4 m. above the top of the sand layer. If an open excavation is to be made in the clay. (See picture below) Determine the void ratio of clay. (Answer: 0.864) Determine the saturated unit weight of clay. (Answer: 18.76 kN/m3) How deep can the excavation proceed before the bottom of the saturated clay heaves or when its effective stress is zero. (Answer: 5.91 m)arrow_forwardAn oedometer test on a 1" thick, doubly-drained sample from the clay stratum (shown below) attained 50% consolidation in 6.5 minutes. Find: (a) The total differential settlement of the fully loaded tank. (b) The time required for 75% consolidation in the field. (c) The depth of excavation for minimal settlement. = 35° Y-120 pcf = 10 ° c = 250 psf Ysat 110 pcf - Ca 1.27 Ce=0.40 40 ft 10 ft 57 ft D = 150 ft Steel Oil Tank Flexible steel foundation Sand Clay A You = 60 pcf Sand B Uniform, normally consolidated clay W.T.arrow_forward
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