INTI COLLEGE MALAYSIA

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1 EGC373 (F) / Page 1 of 5 INTI COLLEGE MALAYSIA UK DEGREE TRANSFER PROGRAMME INTI ADELAIDE TRANSFER PROGRAMME EGC 373: FOUNDATION ENGINEERING FINAL EXAMINATION : AUGUST 00 SESSION This paper consists of FIVE (5) questions. Answer FOUR (4) questions in the answer booklet provided. All questions carry equal marks. 1. (a) A wall footing is to be constructed on a uniform dense sand deposit as shown in Figure Q1(a). The footing is to support a wall that imposed vertical load 400 kn/m and a eccentric moment of 30 kn-m/m of wall length. The depth of footing is 1. m below ground surface. Determine the required width of footing using Meyerhof s Bearing Capacity equation with a safety factor of 3.0. (1 marks) An eccentrically loaded shallow foundation measuring 3 m x 3 m is shown in Figure Q1. The sand deposit has the following soil properties: friction angle φ = 30, cohesion c= 4 kn/m, total unit weight γ t = 18.1 kn/m 3, and saturated unit weight γ sat =19. kn/m 3.Use a factor of safety of 3, determine the maximum allowable load that the foundation can carry. (13 marks) Figure Q1(a) Figure Q1

2 EGC373 (F) / Page of 5. (a) A concrete pile 0 m long has a cross section of 381 mm x 381 mm. The pile is embedded in sand having unit weight γ = 18.9 kn/m 3 and frictional friction φ = 38. The allowable working load is 760 kn. If 450 kn are contributed by the skin friction resistance and 310 kn are from point load, determine the elastic settlement of the pile. The elastic modulus of the pile E p is 1 x 10 6 kn/m. The sand has the following soil properties: elastic modulus E s = 35 x 10 3 kn/m, poisson ratio µ s = 0.35 and skin friction distribution factor ξ along the pile shaft = 0.6, and influence factor I wp =0.85. Given I ws = L. D b) A concrete pile of 500 mm diameter is driven through a 6-m depth clay fill placed over the dense sand deposit to a further 10 m depth. The clay fill is recently placed and will settle under load. The pile is a low displacement pile with earth pressure coefficient k=1-sin φ; and has a soil-pile friction angle δ = 0.70φ. Refer to the Figure Q for details. (i) (ii) Determine the allowable pile capacity, assuming this is a pure friction pile with a factor of safety of 4.0. (10 marks) Determine the allowable pile capacity, assuming this pile has both the end bearing and friction capacity with a factor of safety of 4.0 using the Coyle & Castello s method of determining the end bearing capacity in sand. (7 marks) Figure Q

3 EGC373 (F) / Page 3 of 5 3. (a) In an industrial building, two columns are placed close to each other and will be supported on a common rectangular foundation. The foundation soil is clay with the following soil properties: friction angle φ u = 0, undrained cohesion c u =90 kn/m and total unit weight γ t = kn/m 3. Given that the estimated weight of foundation is kn/m. Using Meyerhof Bearing Capacity equation with a factor of safety of 3.0, determine the footing dimensions. Refer to Figure Q3(a). (16 marks) A mat foundation has a dimension of 1 m x 18 m. The combined dead and live load from the structure is 44.5MN. The saturated clay has the following soil properties: c u =50 kn/m, φ u = 0, γ t =17.6 kn/m 3. Determine the depth of mat for a factor of safety of 3.0 against bearing capacity failure. Refer to Figure Q3. Figure Q3(a) Figure Q3

4 EGC373 (F) / Page 4 of 5 4. (a) A cut is made for a service road creating a finite slope shown in Figure Q4(a). For the soil in the slope, the following values are given: c = 18 kn/m, φ =0 and density ρ= 1700 kg/m 3. Assume the critical surface for sliding to be a plane (Culmann s assumption), determine the maximum safe height of the slope using a factor of safety of.0 against sliding. (c) A cut is made for a railway construction by the Malaysian Railway authority as shown in Figure Q4. Determine the factor of safety according to the Bishop and Morgenstern s method. (1 marks) List a few stabilizing methods that can be used to improve the stability of slopes that are susceptible to landsliding. (4 marks) Figure Q4(a) Figure Q4

5 EGC373 (F) / Page 5 of 5 5. A surcharge and sand drain installation is proposed for an airport project to accelerate the consolidation settlement of a 9m thick clay layer underlying the construction area. In this project, 0.50m-diameter sand drains are installed to accelerate consolidation settlement of this clay layer deposit. The diameter of effective zone of drainage (d e ) is found to be 4.5 m and the coefficient of consolidation for radial drainage (c vr ) and vertical drainage (c v ) is 0.8 m per month. The ratio of horizontal hydraulic conductivity in the unsmeared to smeared zone (k h /k s ) is.5. The radial distance (r s ) from center of sand drain to the farthest point of smear zone is 0.4 m. Assume surcharge is applied instantaneously. (a) Determine the degree of consolidation of the clay layer caused only by the sand drains after six month of surcharge application. (c) Determine the degree of consolidation of the clay layer that is caused by the combination of vertical drainage (drained on both top and bottom) and radial drainage after six month of surcharge application. Determine the temporary surcharge that will be required to eliminate the entire primary consolidation settlement in 4 months by pre-compression technique. Assume that the average effective overburden pressure at the middle of clay layer is 1000 kn/m and the increase in the pressure due the average permanent load on the clay layer is 100 kn/m. 8Tr (- ) m C vt T = d ; e Ur = 1- e ; v t de n = ; r w T v π U = v n n 3 s kh n s = ln + + ( ) ln s ; U v =1-(1-U r )(1-U v ) n s s 4 4n ks n m Appendix 1 Appendix Appendix 3 Appendix 4 Table of Bearing Capacity Factors and other related factors Variation of N q with Friction Angle φ per Coyle & Castello s Method Morgenstern and Bishop s charts for slope stability analysis Plot of mid-plane degree of consolidation against T v Plot of P f / P p against U% for various values of P p / P o -THE ENDegc373apr`0/final/lee

Chapter (11) Pile Foundations

Chapter (11) Pile Foundations Chapter (11) Introduction Piles are structural members that are made of steel, concrete, or timber. They are used to build pile foundations (classified as deep foundations) which cost more than shallow