(i) A multistory building with a basement is to be constructed. Top 4 m consists of loose silt, below which dense sand layer is present upto a great depth. Ground water table is at the surface. The foundation consists of the basement slab of 6 m width which will rest on the top of dense sand as shown in the figure. For dense sand, saturated unit weight = 20 kN/m³ and bearing capacity factors N₁ = 40 and N₁ = 45. For loose silt, saturated unit weight = 18 kN/m³, N = 15 and N, = 20. Effective cohesion C is zero for both soils. Unit weight of water is 10 kN/m³. Neglect shape factor and depth factor. Average elastic modulus E and Poisson's ratio of dense sand is 60 × 103 kN/m² and 0.3 respectively. 9 Ground surface X 4 m Loose silt] Basement foundation slab 1 6 m * Loose silt Dense sand

(i) A multistory building with a basement is to be constructed. Top 4 m consists of loose silt, below which dense sand layer is present upto a great depth. Ground water table is at the surface. The foundation consists of the basement slab of 6 m width which will rest on the top of dense sand as shown in the figure. For dense sand, saturated unit weight = 20 kN/m³ and bearing capacity factors N₁ = 40 and N₁ = 45. For loose silt, saturated unit weight = 18 kN/m³, N = 15 and N, = 20. Effective cohesion C is zero for both soils. Unit weight of water is 10 kN/m³. Neglect shape factor and depth factor. Average elastic modulus E and Poisson's ratio of dense sand is 60 × 103 kN/m² and 0.3 respectively. 9 Ground surface X 4 m Loose silt] Basement foundation slab 1 6 m * Loose silt Dense sand

Principles of Foundation Engineering (MindTap Course List)

9th Edition

ISBN:9781337705028

Author:Braja M. Das, Nagaratnam Sivakugan

Publisher:Braja M. Das, Nagaratnam Sivakugan

Chapter2: Geotechnical Properties Of Soil

Section: Chapter Questions

Problem 2.10P: The soil profile at a site consists of 10 m of gravelly sand underlain by a soft clay layer. The...

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The soil profile at a site consists of 10 m of gravelly sand underlain by a soft clay layer. The water table lies 1 m below the ground level. The moist and saturated unit weights of the gravelly sand are 17.0 kN/m3 and 20.0 kN/m3, respectively. Due to some ongoing construction work, it is proposed to lower the water table to 3 m below the ground level. What will be the change in the effective stress on top of the soft clay layer?
A 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.
Estimate 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 FA
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
1) A 30-ft x 30-ft square mat foundation will be constructed at ground surface. The subsoil profile is shown in the figure. The average stress increase due to mat foundation in clay layer is 360 psf. The primary consolidation settlement (in.) of the clay layer directly below the center of the mat is most nearly: a. 0.2 b. 1.0 c. 21 d. 3.6 ORIGINAL GROUND SURFACE BLEV t a. 3.9 b. 3.3 C. 4.8 d. 4.4 wwwwwwww ELEV-St THE WE ELEV-13 SAND yo 115 pdf ELEV-23 MIAT FOUNDATION GROUNDWATER TABLE SAND = S + 4 MIN NORMALLY CONSOLIDATED CLAY SATURATED COMPRESS VOD RATIO=12 308 **** NOT TO SCALE 2) Assume that the primary consolidation in the previous question is 5 in. what is the primary consolidation (in.) taking into account the three-dimensional effect. (A = 0.6).
4. A square foundation will be constructed at ground surface. The subsoil profile is shown in the figure below. The mat will have a net uniform load of 500 psf at El. O. The mat will have a net uniform load (Induce stress) at El. -15 of 360 psf, the primary consolidation settlement (in.) of the clay layer directly below the center of the foudnation is? fr ORIGINAL GROUND SURFACE ELEV. O ft ELEV-5 ft. ELEV-10 ft ELEV-20 ft 30 ft SAND Y = 115 pcf MAT FOUNDATION SAND Y = 105 pcf GROUNDWATER TABLE NORMALLY CONSOLIDATED CLAY SATURATED UNIT WEIGHT = 95 pcf COMPRESSION INDEX C₂ = 0.29 VOID RATIO=1.0
The plan of a rectangular foundation shown in figure transmits a uniform contact pressure of 120 kN/m². Determine the vertical stress induced by this loading at point B under a depth of 5 m. (40 marks) 25.0- 15.0 6.0- 4.0 B•
In a site investigation for a large foundation project it is determined that there is a clay layer with capillary rise of 6.0 m above the groundwater table. What would be the effective stress and the pore pressure at point A located 2m above the groundwater table? Assume clay has Gs=2.70 and moisture content in capillary zone is 10%. Clay Gs=2.7, w=10% 10 m A. 2m
A foundation (Figure 1) transmits a stress of 100 kPa on the surface of a soil deposit. a. Evaluate increases of vertical stresses points A, B, and C at the depth of 2m and Sm (2 points) b. At what depth is the increase in vertical stress below A less than 10% of the surface stress? 6 m +2 m- A 2 m -4 m- Figure 1: Plan of foundation
In the soil profile shown, the clay layer is normally consolidated and the ground water location maybe assumed to remain constant. The raft foundation is 15 m x 15 m with a uniform loading of 192 kPa. a) Compute the initial effective stress at the mid-point of clay layer. b) Compute the change in stress at the mid-point of the clay layer if it has an influence factor of 0.90. c) Compute the approximate settlement due to placement of the raft foundation.
Refer to Figure 5.12. For a rectangular foundation on layered sand, given:●● B = 4 ft, L = 6 ft, H = 2 ft, Df = 3 ft●● γ1 = 98 lb/ft3, Φ'1 = 30º, c'1 = 0●● γ2 = 108 lb/ft3, Φ'2 = 38º, c'2 = 0Using a factor of safety of 4, determine the gross allowable load the foundation can carry.
A 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)…