Principles of Foundation Engineering, SI Edition
9th Edition
ISBN: 9781337672085
Author: Das, Braja M., SIVAKUGAN, Nagaratnam
Publisher: Cengage Learning
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Question
Chapter 10, Problem 10.6P
(a)
To determine
Find the depth of the foundation.
(b)
To determine
Find the factor of safety.
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Students have asked these similar questions
It is proposed to build an 8 story building with a footprint
of 15 m X 20 m, resting on a mat foundation of the same
dimensions, in a saturated clay where cu = 50 kN/m²,
y = 19.0 kN/m³. Assume approximately 15 kN/m² per floor
for the live and dead loads.
a. At what depth would you place the mat to make this a
fully compensated foundation?
b. What should be the factor of safety if the mat is placed at
3.0 m depth?
An office building is to be supported on 150 ft : 300 ft mat foundation. The sum of the columnloads plus the weight of the mat will be 90,000 k. According to a settlement analysis conductedusing the techniques described in Chapter 8, the total settlement will be 1.8 in. The groundwatertable is at a depth of 10 ft below the bottom of the mat. Using the pseudo-coupled method,divide the mat into zones and composite each zone. Then indicate the high-end and low-endvalves of ks that should be used in the analysis.
Q3.
A mat foundation is shown in figure below. The design considerations are L 12 m, B
-10 m, Df 2.2 m, Q = 30 MN, x1 =2 m, x2 2 m, x3 -5.2 m, and preconsolidation pressure oe
= 180 kN/m?. Calculate the consolidation settlement:
under the center of the mat.
• Under the corner of the mat
Size of mat = BXL
Sand
Dr
y = 16.0 kN/m3
X1
Groundwater
table
Sand
Yeat = 18.0 kN/m
Clay
= 17.5 kN/m3
EYsat
e, = 0.88
C = 0.38
C; = 0.1
Chapter 10 Solutions
Principles of Foundation Engineering, SI Edition
Ch. 10 - Refer to the rectangular combined footing in...Ch. 10 - Prob. 10.2PCh. 10 - Prob. 10.3PCh. 10 - Prob. 10.4PCh. 10 - Prob. 10.5PCh. 10 - Prob. 10.6PCh. 10 - Prob. 10.7PCh. 10 - Prob. 10.8PCh. 10 - A plate loading test was carried out on a medium...Ch. 10 - A 300 mm 450 mm plate was used in carrying out a...
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- It is proposed to build an 8-story building with a footprint of 20 m x 30 m, resting on a mat foundation of the same dimensions, in a saturated clay with undrained shear strength of 60 kPa. Assume approximately 12.5 kPa per floor for dead and live loads. Unit weight of soil is 18kN/m3 . a) At what depth would you place the mat to make this a fully compensated foundation?b) What would be the depth of this mat foundation for the net factor of safety of 5?c) What is the gross factor of safety for the depth determined in the answer to question b)?arrow_forward10.6 It is proposed to build a 8 story building with a footprint of 15 m X 20 m, resting on a mat foundation of the same dimensions, in a saturated clay where c, = 50 kN/m², y = 19.0 kN/m. Assume approximately 15 kN/m² per floor for the live and dead loads. a. At what depth would you place the mat to make this a fully compensated foundation? b. What should be the factor of safety if the mat is placed at 3.0 m depth?arrow_forwardFind the settlement due to consolidation of a 9ft × 9ft coloumn foundation (figure) with a load of 1500 Ibs. The foundation is placed at 3 ft below the top surface and the clay layer is 25 ft thick. There is a sand layer underneath of the clay layer. The density of the clay layer is 115 Ibs/cf the compression index of the clay layer is 0.32 and the initial void ratio of the clay is 0.085. Assume that the pressure is distributed at a 2:1 ratio and clay is normally consolidated.arrow_forward
- It is proposed to build an eight- story building with a footprint of 15 m x 20 m, resting on a mat foundation of the same dimensions. Mat foundation is located in saturated clay with undrained shear strength of 60 kPa and unit weight of 20 kN/m3 . Assume approximately 15 kN/m2 per floorfor live and dead loads (together). a) At what depth would you place the mat to make this a fully compensated foundation?b) What is the gross factor of safety of the fully compensated foundation against the bearing capacity failure?arrow_forwardA water tank is required to be constructed with a circular foundation having a diameter of 20m founded at a depth of 2m below the ground surface. The estimated distributed load on the foundation is 300 kN/m². Assuming that the subsoil extends to a great depth and is isotropic and homogeneous, determine the stresses °z at points (i) z = 6m, r = 0, (ii) z = 6m, r = 10m, (iii) z = 20m, r = 0 and (iv) z = 20m, r= 10m, where r is the radial distance from the central axis. Use the Influence Diagram below to calculate the I. Neglect the effect of the depth of the foundation on the stresses. Influence value l, (x100) 0.1 1.0 10 100 1.25 1.5 1.0 1 2.5 3 0.0 0.25 0.5 0.75 3 Note: Numbers on curves indicate value of r/Ro 5 6. -B = 2R, mi HR 7 10 0, = 1.9 10 Fig. 1. Influence Diagram for the Vertical Normal Stress at Various Points Under a Uniformly Loaded Circular Area (Foster and Ahlvin, 1954) 4. 00 Depth z/Roarrow_forwardProblem.№₂3 - The plan of a mat foundation is shown in Figure. Calculate the soil pressure at points A, B, C, D, E, and F. (Note: All column sections are planned to be 0.5 m 3 0.5 m.) All loads shown are factored loads according to ACI 381-11 (2011). 550 KN 2000 KN 5.25 m 2000 KN 550 kN F *K 0.25 m G H 10 m ! B i 660 kN 2000 KN 10 m 2000 KN 660 kN E 600 KN 1600 KN 5.25 m 10 m 1600 KN 470 kN C D *K 0.25 m 9 m 9 m 9 m 0.25 m 0.25 marrow_forward
- It is proposed to build a 8 story building with a footprintof 15 m x 20 m, resting on a mat foundation of the samedimensions, in a saturated clay where cu=50 kN/m2, Unit weight=19.0 kN/m3. Assume approximately 15 kN/m2 per floorfor the live and dead loads.a. At what depth would you place the mat to make this afully compensated foundation?b. What should be the factor of safety if the mat is placed at3.0 m depth?arrow_forwardPROBLEM 5. A water tank is required to be constructed with a circular foundation having a diameter of 20m founded at a depth of 2m below the ground surface. The estimated distributed load on the foundation is 300 kN/m. Assuming that the subsoil extends to a great depth and is isotropic and homogeneous, determine the stresses z at points (i) z = 6m, r = 0, (i) z = 6m, r= 10m, (i) z = 20m, r = 0 and (iv) z = 20m, r = 10m, where r is the radial distance from the central axis. Use the Influence Diagram below to calculate the I. Neglect the effect of the depth of the foundation on the stresses. Influence value I, (x100) 1.0 10 100 .25 1.5 1.0 0.0 0.25 2.5 0.75 3. Note: Numbers on curves indicate value of r/Ro B = 2R, 10 o, = 1.4 8 10 Fig. 1. Influence Diagram for the Vertical Normal Stress at Various Points Under a Uniformly Loaded Circular Area (Foster and Ablvin, 1954) Depth z/R.arrow_forwardA load of 800 Kip will be distributed on a circular foundation with a diameter of 20 feet, this structure will be located on the existing ground. The soil at the site has a unit weight of 105 lb/ft^3. Prepare a situation diagram to determine the vertical effective stress (lb/ft^2 no decimals) after building and loading the foundation at a point located: a) 12 feet below its center. b) 12 feet below its edge.arrow_forward
- A water tank is required to be constructed with a circular foundation having a diameter of 20m founded at a depth of 5m below the ground surface. The estimated distributed load on the foundation is 400 kN/m2. Assuming that the subsoil extends to a great depth and is isotropic and homogeneous, determine the stresses at points (i) z = 10 m, r = 0, (ii) z = 10 m, r = 10 m, (iii) z = 20 m, r = 0 and (iv) z = 20m, r = 10m, where r is the radial distance from the central axis. Use the Influence Diagram below to calculate the I. Neglect the effect of the depth of the foundation on the stresses.arrow_forwardA 10 m * 30 m mat foundation is to be built on the surface of a 20 m thick layer of unsatu-rated silty sand. The silty sand is underlain by a stiff bedrock material. The water table is at a great depth. The silty sand is relative uniform and in situ testing indicates it has a constrainedmodulus of 19 MPa. The building applies a uniform stress of 50 kPa at the base of the mat.Compute the settlement under the center of the mat.arrow_forwardQ3- A raft foundation (12 * 8) m carrying a net pressure of 183 kN/m² is located at a depth of 3.8 m below the surface in deposit of dense sandy gravel 6 m deep. The water table is located at a depth of 4.3 m. Below the sandy gravel is a layer of clay 3.8 m thick which in turn is underlain by dense sand. The value of mv for the clay is 0.28 m²/MN. Determine the settlement below the center and below the corner of the raft due to consolidation of the clay.arrow_forward
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