Fundamentals of Geotechnical Engineering (MindTap Course List)
5th Edition
ISBN: 9781305635180
Author: Braja M. Das, Nagaratnam Sivakugan
Publisher: Cengage Learning
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Chapter 17, Problem 17.15P
A shallow square foundation for a column is to be constructed. It must carry a net vertical load of 1000 kN. The soil supporting the foundation is sand. The standard penetration numbers (N60) obtained from field exploration are as follows:
FIG. 17.15
The groundwater table is located at a depth of 12 m. The unit weight of soil above the water table is 15.7 kN/m3, and the saturated unit weight of soil below the water table is 18.8 kN/m3. Assume that the depth of the foundation will be 1.5 m and the tolerable settlement is 25 mm. Determine the size of the foundation.
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Q.3) Considering the given test setup answer the following questions.
a) Calculate the coefficient of permeability if the cross-sectional area of the soil sample is 28 cm² and the
flow rate is 8.2 cm³/s.
b) Calculate the vertical effective stress acting on 10cm above plane A-A if the saturated unit weight of the
soil sample is 19 kN/m³. Take unit weight of water as 10kN/m³
Sample
A
10 cm.
50 cm
40 cm
10 cm.
Borings indicate that at a Staten Island, NY site, the top 6 meters is a
loose sand with a groundwater level at 3 meters below the ground surface. Below
the sand is a 12 meter thick soft clay stratum. Assume sand unit weights are
ymoist = 15 kN/cubic meter and ysat = 16 kN/cubic meter. Assume clay ysat = 20
kN/cubic meter. Calculate total, pore and effective stresses at 4, 13 and 18
meters deep.
Plz give the correct answer.
Compute the intensities of active and passive earth pressure at depth of 8 m in dry cohesionless sand with an angle of internal friction of 30 degrees , and unit weight of 18kN / (m ^ 3) What will be the intensities of active and passive pressure if the water level rises to the level? Take the saturated unit weight of sand as 22kN / (m ^ 3) .
Chapter 17 Solutions
Fundamentals of Geotechnical Engineering (MindTap Course List)
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- Give the correct option In a drained triaxial test on consolidated clay the stress and angle are as follows: Deviator stress is 20 lb/in2 and friction angle is 21°. Calculate the effective confining pressure at failure?a) 21 lb/in2 b) 22.2 lb/in2 c) 25.4 lb/in 2 d) 17.9 lb/in2arrow_forward2) Borings indicate that at a Staten Island, NY site, the top 6 meters is a loose sand with a groundwater level at 3 meters below the ground surface. Below the sand is a 12 meter thick soft clay stratum. Assume sand unit weights are ymoist = 15 kN/cubic meter and ysat = 16 kN/cubic meter. Assume clay ysat = 20 kN/cubie meter. Calculate total, pore and effective stresses at 4, 13 and 18 meters deep. %3Darrow_forwardA net contact pressure equals 160 kN/m2 is applied to a stiff clay layer 15 m thick. The footing is 6 m square founded at 2 m depth below ground surface. A layer of silty sand, 2 m thick, overlies the clay and a firm stratum lies immediately below the clay. Oedometer tests on specimens of the clay gave the value of mv =0 13 m2/MN, and triaxial tests gave the value of pore pressure parameter A = 0 35. The undrained Young’s modulus for the clay Eu was estimated equal 55 MN/m2. Determine the total settlement under the footing centre.arrow_forward
- Question 1 Figure Q1 shows a vertical cross-section of a site. The ground water table is located at 2 m below the ground surface. Dry and saturated unit weights of the sand are 16 kN/m³ and 20 kN/m³, respectively. The clay is normally consolidated and has a saturated unit weight of 18 kN/m³ and an effective friction angle of 32°. The unit weight of water is taken as 10 kN/m³. (a) (b) (c) (d) (e) Calculate the vertical effective stress at Point A. Calculate the horizontal effective stress at Point A. Calculate the normal stress and shear stress acting on a plane oriented 60° from the horizontal plane at Point A What is the maximum horizontal shear stress that the soil at Point A can take before failure? What is the maximum shear stress along a plane oriented 60° from the horizontal plane that the soil at Point A can take before failure? 2m 4m 2m 8A Sand Clay Figure Q1arrow_forwardThe results of two drained triaxial tests on a saturated clay are given next: Specimen 1: Chamber confining pressure = 15 lb/in.? Deviator stress at failure = 31.4 lb/in.? Specimen II: Chamber-confining pressure = 25 lb/in.? Deviator stress at failure = 47 lb/in.? Calculate the shear strength parameters of the soil.arrow_forwardA)Plot graphically all the vertical stresses, pore water and effective vertical stresses throughout the depth. B)How would the effective vertical stress value at the midpoint of the clay layer change if the groundwater level increased 2 m? (g = 10 m / s2)arrow_forward
- 2- Subsurface geotechnical investigations carried out in a deposit of sand provided the field standard penetration numbers N60 as given in the table below. During the geotechnical investigations, it is also observed that underground water table is encountered at a depth of 2.0 m below the ground surface. Laboratory tests have shown that physical properties of deposit of sand are as: Dry unit weight = 17.6 kN/m³ and saturated unit weight = 19.6 kN/m³. Determine, for an earthquake magnitude of 8.25, if liquefaction will occur at the site. Assume that maximum peak ground acceleration at the site is: amax = 0.25g. (6 points) DEPTH (M) N60 (BLOWS/30CM) 3 5 6 7 9 11 12 14 18 21 Note: the gravitational acceleration could be taken as 9.81 m/s².arrow_forward2- Subsurface geotechnical investigations carried out in a deposit of sand provided the field standard penetration numbers N60 as given in the table below. During the geotechnical investigations, it is also observed that underground water table is encountered at a depth of 2.0 m below the ground surface. Laboratory tests have shown that physical properties of deposit of sand are as: Dry unit weight = 17.6 kN/m³ and saturated unit weight = 19.6 kN/m. Determine, for an earthquake magnitude of 8.25, if liquefaction will occur at the site. Assume that maximum peak ground acceleration at the site is: amax = 0.25g. DEPTH (M) N60 (BLOWS/30CM) 6. 7 9 11 12 14 18 21 Note: the gravitational acceleration could be taken as 9.81 m/s.arrow_forward1. Triaxial compression tests are done on quartzite rocks, the results are shown below. (0₁+03)/2 -964.25 14500 19575 23200 29000 43210 63075 psi (01-03)/2 964.25 14500 18850 21750 26100 35960 48575 psi Comment on the applicability of each of the Mohr-Coulomb, Griffith, and Hoek-Brown criteria for the testing results.arrow_forward
- 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 ? a. 10m b. 6m c. 9m d. 8marrow_forwardShear Strength of Soil The following are the results of two consolidated-drained triaxial tests on a clay: Test I: 03 = 140 kN /m2; o, ʻi failure) = 368 kN /m² Test II: 03 = 286 kN/m²; ơ,(ailure) = 701 kN /m²? Determine the shear strength parameters; that is, c' and o'. (Enter your answers to three significant figures.) d' kN /m² || 3.arrow_forward46. Consolidation of Clay: Given Exercise Figure 7.4 and the accompanying information, what is the ultimate settlement in the clay under the applied load? Note: 1 ft = 0.3048 m; 62.4 lb/ft³ = 1 Mg/m³. Assuming the sand will not settle, determine the ulti- mate settlement in the clay using: Proceeding in steps: a. Determine the effective stress for the cross section prior to loading. Show the stresses at depth using an appropriate diagram. b. What is Ao' on the clay layer caused by the imposed load? (Hint: Calculate this for the center of the clay layer at 5.8 m [19 ft] deep.) (ft) 0 c. What is the value of eo based on the original poros- ity of the clay? d. How much settlement will occur in the clay? 5 H ΔΗ =· -C log 1+- 1+e 16 22 40' o' P= 125 tons Sand: Yd=105 lb/ft³ Silty sand: Ysat Clay: Ysat=121 lb/ft³ n = 0.629, C = 0.82 Exercise Figure 7.4 = 127 lb/ft³ GWTarrow_forward
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