Question

Figure 1.1, below, shows a proposed concrete cantilever retaining wall Assess the stability of the wall assuming that u 0.45, Yconc. =24 kN/m8, the maximum (i) allowable bearing pressure for the sand is 200 kPa, and the wall rotates about point O. (18 marks) (ii) f the proposed wall does not satisfy the design criteria, list 4 options that might be employed to improve the wall's stability. (2 marks) 1 2. 3. 4. 300 mm с, — 20 kPa = 0° Y 18 kN/m3 Clay 3 m c' 0 kPa 35° Y = 20 kN/m3 Sand 400 mm 400 mm 4 m Sand Figure 1.1 Concrete cantilever retaining wal 8 m

Answer 1

9iven figure KPa 3 00mm 40 Gu=2okPa 2.23m 3 m CLAY 18 K/ O78m 4 14.58 c O BM SAND -35 2 Sm Y= 20y/m3 400mm 400mm 1OXO.4 W2 91-58 4 KN/ 4-m 1-Sindu Fa clay Kai 1 Achve ese 1+sinfu Pressure coetfi 1-sinp Kaz O-27 1 Fo Sand cients sing

Active pressute Calcwehion PKa-2cJKa 0-2 Jka Pa @ top = - 40kfa - 2X 20 JI 2x20 JT 1x iSx3] Just above 3m Pa e = 14 KPa 18x3] - O Pa @ Just below 3m 14.58kPa O+1oxs Pa Bottom + B18x 3 O2X 91.58 kPa depth "h GV=O Kah 2cKa = o Karh =2cKa acJKa 2C JKa Kay 2X20 h (i) = 2.23m 18x CKN-m) Maments Force s S.NO Levenanm Fom 0 Venhcal Houzontal (H) (v) (1 W24X0.3x8 0-ISm 8.64 57.6kN/m Wan 34 xo-4x3.7 = २ 04 35. 52 k/m

Pa,40 18 5.46 K/m 5+ O78 28 7196 5.२6m Pa 4 1.39m 9158) S03.08 265.4 KN/m - O.4 Pasox4 3 O.106 O.8 KN/m O)34 m +ve - ve EMR EV= S1.6+35 52 EH=5.46+265.4-0.8 EMO = 79.786 S31 79 -93.12 270.06 KN 14 58 A9 +A292 AitA 2 -sK4 5) 5m 1.89m X 4 58XS]+ - 14. 58 7 91 58 ।৪২ ২S+ 320 83 y> 1२.१+।१२.ऽ >1.89 m 2%

Factol of Safety against ovestuning EMR F.S= EMo 79-786 531 79 =O.15 FS<I Not sabe atainst oventuan shean friction facter SFF Facta of Safety against sliding u EV F.S = E H O.45X 93.12 210.06 O-155 F.S< Not sabe against sliding o'] Distance of Resullant fom Toe EM E V 531 79-19 786 93.12 d = 4.85 m eccenticity e 4 +4.85 = 3.85 m =0.6 Tenim devdlps e Bl Not sabe

the foundahom Soil PYessure E V 1+ 93 12 1 + 6X२.85 4 4 1 4.215] 23 28 + max 122.802 MPa Pmin -76. 24 MP 76.24MP 122.8 MPa Fa Sabehy Pax S SB.C Soil Beaning Cafact 122.8 2 00 kPa MPa O-2MPa Not Sabe (it) weiskt of the wall by Providing Increase width and thickness Backfill 3m depth with above 2 Coanse gyained Inslead of clay Soil 3. do Dewaltuing Nean he wall to Yeduce oachve pressure 4 . PYovide backfill Soil Left side of the wall On