Question

103 35) 15:59 A rectangular footing (1.4 mx 1.6 m) of shallow foundation is designed to receive ad from a column of a building constructed on over consolidated sand, Figure 2 shows the properties of sub-ground and initial design of the footing. Ground water level is located at 25 m below ground surface. (use ES - 2.5) 25000ks - 1630 kw H POKER Figure 2 a) Using appropriate bearing capacity equation, evaluate whether the width of footing design in Figure 2 is sufficient using considerable design assumption (CO2: POS 9 marks) b) Evaluate the elastic settlement of the foundation using elasticity theory if the value standard penetration number from SPT best of various soil layer is given in Table 1 (C02: PO3 - 8 marks) Table 1 Depth Standard penetration number, Ne 1.5 IL 3.0 10 12 4.3 6.0 c) Based on similar information in Table 1, evaluate the attement using Meyerhof's method for determination of foundatice settlement in elastic soil medium. Discuss your findings and compare with your wer in (b). (CO2. PO3 Smarks)

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Answer 1

25000kg. Given ca) Factor of safety=2.5 8=1630 kg/m3 – о 01-32 le=0.35 1.2m H=2.5m 1.4m D GWT p=2150kg 1 m3 1.6 m 1.4m fig: - Plan of foundation

We know that For rectangular footing Ne = 5 (1 +0.2 DF) (1+0-28 for Df <2.5 Where Nc = Bearing capacity factor = 5 (1+0.2012 Ito-201-4 If = 1.2m 1.4 B = 104m 5.85 X 1.14 = 6.66 From Terzaghi Equation Ultimate Bearing capacity (20) = (1+0.34) CNC TYDENG +05-02.XYB My For $=32° Nc=3702 , Nq=22.5, Ny = 1907 رنا c=0 Put the above value in equation (i), we get

qu=0+1630X1.2X22:5 +0.5 (1-0-2 X 14 ) X2150X14X19.7 1.6 =0+44010 +24460.01 :qu = 68470.01 kg/m2 Also safe Bearing capacity (as) = qu_YDf TY DE fooos. 68470.01 -1630X1.2 2.5 + 1630X12 = 26605 ta 1630X1-2 i. q. = 28561.6 kg/m² Sate load carried by footing = qs X Area of footing - 28561.6 X 1.4x1.6 = 63977.gokg > 25000kg Hence, footing wiath is sufficient. Answer

(bo) Elastic settlement of foundation using elastic theory :- We know that settlement(si) = qb If -612 E where, q=het foundation pressure B = width of foundation = Poisson's ratio = modulus of elasticity If = Influence factor For rigia foundation Ru = 106 = 1.1, If = 1 14 q = А ll 20.35 = 25000 =11160.71 kg/m2 1-481.6 put the above value in equation ijineget. where, E=1200 (N16) Si=11160.71X1.4 / 1 - X1 N=SPT value 204000. N = 11 0.0671 m = 1200X(1146) = 204000 kg Ing² i. Sii = 0.067 im 67 mm Elastic settlement = 67mm (1-6:33 Answer

C) Noo - Mayerhoff's Method of Settlement A/T expression given by Mayerhoff quet ( B+ 1)2 fd. Se met = Net pressure on foundation Noo = Spe value = 11 B= width of foundation in feet Fd=depth factor = +0.33 Df Where B - to 33x1.2 1.28 4.55+1 + 1.282x se 4.55 Se 2.5 inches 62.5mm Se = settlement of foundation Discusson :- Settlement = 67mm 67 mm from elastic theory settlement - 62.5mm Mayerhoff's theory