9.4 An 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? Ans: 3.97 m 6.1m E 4m £ Exploratory drill hole Saturated clay Sand Figure (9.9) G₁=2.72 Moisture content=w=35%

9.4 An 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? Ans: 3.97 m 6.1m E 4m £ Exploratory drill hole Saturated clay Sand Figure (9.9) G₁=2.72 Moisture content=w=35%

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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A cut slope was excavated in sand. The slope is shown in following attachment . To find the properties of the sand, representative samples were taken for the soil and tested in atriaxial apparatus. A consolidated drained triaxial test was conducted. The result is given below:Chamber pressure = 103 kN/m2Deviator stress at failure = 234.6 kN/m2We know the unit weight of the sand is 16 kN/m3.Use the ordinary method of slices (use 7 slices) and estimate the factor of safety against sliding forshown slip surface and comment on the calculated factor of safety.Please note that:1. The figure is not in scale. You may resketch it in scale and calculate the factor of safety2. The slip surface is circular and passes through the toe of the embankment
gerotechnical engineering question
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. 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?
geotechnical engineering question
5. A CPT sounding is carried out at a site. The water table is found to be 2 meters underground. A layer of soil is identified, from z = 3m to z = 7m. The raw cone tip resistance for the layer is 900 kPa, the sleeve friction resistance is 65 kPa, and the penetration pore pressure is 220 kPa. Calculate the friction ratio for the soil layer.
The answer should be 9.56"
9.4 An 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 G₁=2.72 6.1 m Moisture content -35% m 4m £ Saturated clay Sand
Question 8 A gulf coast formation at 7,500 ft is drilled using 10.5 lb/gal mud. Total circulation pressure is 2500 psi; out of which 60% is lost across bit nozzles and the other 40% is lost equally between drilling string and annulus. Find formation pressure, fracture pressures, overburden pressure, and ECD. Is this a safe drilling operation?
Time left 1:24:08 An excavation is to be performed in a stratum of clay, 9 m thick, underlain by a bed of sand. In a trial bore hole, the ground-water is observed to rise up to an elevation 3 m below ground surface.Find the depth of which the excavation can be safely carried out without the bottom becoming unstable under uplift pressure of ground-water. The specific gravity of clay particles is 2.70 andthe void ratio is 0.70. If the excavation is to be safely carried to a depth of 7 m, how much should the water table be lowered in the vicinity of the trench ? O a. 6 m O b. 9 m C. O c. 10 m O d. 8 m SHOT ON POCO F3
(a) Compute the intensity of passive earth lios pressure at a depth of 8m in a cohesionless sand with an angle of internal ange friction of 30° when water table rises to the ground level. Saturated unit weight of sand is 21 kN/m3; yw = 9.81 kN/m (b) A vertical excavation was made in a clay deposit having unit weight of 22 kN/m3. It caved in after the digging reached 4m depth. Assuming = 0, calculate the magnitude of cohesion.