Principles Of Foundation Engineering 9e
9th Edition
ISBN: 9781337705035
Author: Das, Braja M.
Publisher: Cengage,
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The initial principal stresses at acertain depth in a clay soil are 200 kPa on the horizontal plane and 100 kPa on the vertical plane.Construction of a surface foundation induces additional stresses consisting of a vertical stress of 45 kPa, a lateral stress of 20 kPa, and a clockwise(with respect to the horizontal plane) shear stress of 40 kPa. Determine the change in shearing stress in kPa.
A vertical column load, P = 600 kN, is applied to a rigid square concrete foundation. The
foundation rests at a depth Df= 0.75 m on a uniform dense sand with the following properties:
average modulus of elasticity, Es = 20,600 kN/m², and Poisson's ratio, µs = 0.3. Calculate the
required foundation dimensions if the allowable settlement under the center of the foundation is
25mm.
600 kN
Foundation
0.75 m
Вхв
Soil
Hs = 0.3
E, = 20, 600 kN/m²
5.0 m
Rock
Problem II. The initial principal stresses at a certain depth in a clay soil are 100 kPa on the horizontal plane
and 50 kPa on the vertical plane. Construction of a surface foundation induces additional stresses consisting
of a vertical stress of 45 kPa, a lateral stress of 20 kPa, and a counterclockwise (with respect to the horizontal
plane) shear stress of 40 kPa.
a.
Plot Mohr's circle (1) for the initial state of the soil and (2) after construction of the foundation.
b. Determine the change in magnitude of the principal stresses.
C.
the change in maximum shear stress
d. the change in orientation of the principal stress plane resulting from the construction of the foundation.
Chapter 9 Solutions
Principles Of Foundation Engineering 9e
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- refer to the figure below. Determine the average stress increase in the clay layer below the center of the foundation due to the net foundation load of 50 tons.arrow_forwardThe initial principal stresses at a certain depth in a clay soil are 200 kPa on the horizontal plane and 100 kPa on the vertical plane. Construction of a surface foundation induces additional stresses consisting of a vertical stress of 45 kPa, a lateral (horizontal) stress of 20 kPa, and a counterclockwise (with respect to the horizontal plane) shear stress of 40 kPa. Plot Mohr's circle (1) for the initial state of the soil and (2) after construction of the foundation. Determine (a) the change in magnitude of the principal stress, (b) the change in maximum shear stress, and (c) the change in orientation of the principal stress plane resulting from the construction of the foundation.arrow_forwardRefer to Figure 5,determine th eaverage stress increase in the clay layer below the center of the foundation due to the net foundation load of 490,500kN (net load). Using Eq.(7.25)arrow_forward
- A flexible foundation is 2 m x 4 m rests on granular soil at ground level. It carries a uniformly distributed load of 160 kN/m2. The sand has an elastic modulus of 39 MPa , a Poisson's Ratio of 0.3 and is 5 m thick. Estimate the elastic settlement below the center of the loaded foundation. Give your answer in cm rounded to 2 decimal places.arrow_forwardA mat foundation, 15 m x 15 m, is made of reinforced concrete and to be supported by a three-layer soil profile, as shown. The mat is 1 m thick, and the average stress on the surface of the slab assessed from the structural engineering analysis is 75 kPa. (Unit weight of concrete = 23.58 kN/m^3) The 5-m thick sand layer immediately below the mat foundation has been compacted to standard Proctor specifications, most likely to optimum moisture content, which is why its moist density is given. (A) Determine the pre-construction effective stress at Point A (bottom of the clay layer). This is the in situ effective stress (overburden pressure) measured from the ground surface prior to the placement of the mat foundation. (B) Determine the vertical stress increase induced by the mat foundation at Point A using the “Influence Chart,” commonly referred to as the “Spider Web.” (C) Determine the vertical stress increase induced by the mat foundation at Point A using the “Stress Isobars.” (D)…arrow_forwardThe attached figure shows the plan of rectangular foundation which transmits a uniform contact pressure of 120 kN/m2. The width of the foundation is 15 m. A) Determine the increase in vertical pressure at a depth of 10 m below point A B) The vertical stress at a depth of 10m below point Barrow_forward
- The subgrade reaction of a sandy soil obtained from the plate load test (plate dimensions 1 m × 0.7 m) is 18 MN/m3. What will be the value of k on the same soil for a foundation measuring 5 m × 3.5 m?arrow_forwardEstimate the increase in vertical stress at 0.5 m depth intervals, within the clay layer, below point A (See figure below). The foundation exerts a uniform vertical stress of 120 kPa at ground level. Using these values estimate the settlement due to the clay layer. (Hand in any graphs used) 5m 5m 2m 3m Very Dense Sand 2m 1.5m Clay E=3.5 MPa 2m Bedrock Soil profile A Plan of building 3m Soil profile and plan for Question 4 3m FAarrow_forwardA circular foundation (D = 6 m) is built on a construction site where the soil profile is shown in Figure 5 below. The circular foundation applies a uniform pressure of 80 kPa to the surface of clay. The properties of the clay are: Specific gravity, G₁ Saturated unit weight at Compression index Ce Recompression index Cr Consolidation coefficient, c Over-consolidation ratio, OCR 10 m 6m Ø Clay Impervious rock Figure 5 2.6 20 kN/m³ 0.25 0.10 2.5 m²/year 1.2 (b) Calculate the stress increase at the center of the clay layer and 1) beneath the foundation center and 2) beneath the edge of the foundation; (c) Calculate the consolidation settlement beneath the center of the foundation due to the stress increase; (d) Determine the settlement at the center of the clay after 1 year of applying the pressure; (e) A 50 mm thick clay sample was taken from the site and consolidated in the oedometer, how long it will take for the clay to reach 90% consolidation?arrow_forward
- The initial principal stresses at a certain depth in a clay soil are 100 kPa on the horizontal plane and 50 kPa on the vertical plane. Construction of a surface foundation induces additional stresses consisting of a vertical stress of 45 kPa, a lateral stress of 20 kPa, and a counterclockwise (with respect to the horizontal plane) shear stressof 40 kPa. Determine the change in orientation of the principal plane resulting from the construction of foundation. CHOICES ( WITH COMPLETE SOLUTION): a. principal stress plane rotates 23 degree counterclockwise from horizontal plane b. principal stress plane rotates 46 degree clockwise from horizontal plane c. principal stress plane rotates 23 degree clockwise from horizontal plane d. principal stress plane rotates 46 degree counterclockwise from horizontal planearrow_forwardThe plan of a foundation of uniform thickness for a building is shown in Figure 2. Determine the vertical stress increase at a depth of 10 m below the centroid. The foundation applies a vertical stress of 300 kPa on the soil surface.arrow_forwardplease solve.arrow_forward
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