Question

RCD3601/101/0/2019 QUESTION 8 Figura o shows the section through a neonased reinforced concrete cantilever retaining wall that will be situated on a property boundary. Grade 30/19 concrete and high tensile steel reinforcement is to be The backfill behind the wall is sloping at an angle of 15º measured from the horizontal and is subjected to an imposed load of 2.5 kN/m². A geotechnical report gave the following soil parameters: • Unit weight of soil (V) = 17 kN/m • Angle of internal friction (0) = 33 • Allowable bearing pressure (P.) = 150 kPa • Friction co-efficient (1) = 0,47 Assume that the backfill will be well-drained and that the soil in front of the wall is adequately compacted and it will be used to offer passive resistance to sliding. 0 Check the stability of the wall considering overturning, sliding and ground pressure. (6) Design suitable reinforcement (ignore curtailment thereof) for flexure in the stem of the retaining wall and provide a simple sketch to illustrate your design 0 - 15" 0000 2501 1500 1750 Figure Q8 [10 marks) 17

Answer 1

Answer). Given unit weight of Soil(0)= 17 KNIM 3 Angle of internal friction (o)-33º. Allovable bearing pressure (PL) - 150 kPa friction coefficient (u) = 0.44. + 250 0 150 3000. 5000 7300 ISAU 177. 25419 il check for overtuning | No - PAYH2 -0 where PH = 0.58 Ka x7x3.52_@. Load & moment calculations : - Load Magnitude Distance from ” | -TW, = 3.200.25625 20kn 0.125m as: 1.75*0.3x25 W₃ = 1.5x2.8x17 | 71.4 KN Ew=104.2525kn| Moment 2:5 K-m 13.125kw 0. 875m 11-48 km 71.4 KNM im 24-8538 km

Horizontal Carth Pressure CPH) PH = 1/2Xka XQX H2 ka= cosp. Cosße costß-cos² Cosßt.cos 23-cos26 ka=(0-96) (0.96) -56096)2 (083)2 (096)+)(0.96)2-(0-83)2 Ika=0.349) from @ => PH -0.540.349x17x3:52 PH = 3634 kW/m2 from = Mo = PHX H2 = 36.34x 1.75 Mo - 63595 KNM factor of safety for over tuning : 09X5M mo : 0.9x8538 6359 =1.208 $ safely should be s "14" The calculated Value < 1.4. It is unsate for overtunning. check for ground Pressure :- Oman = a (i top] where e =0.56-[MWA - MPA] /w =0.581.75 (85-38 - 63-595) 104.525

16=0.6667 104:525 (14 64. 666] Amax = 196.11 Pmax > Allowable bearing pressure (iso kPa] It is safe against ground pressure. ii) Design of suitable reinforcement : - * Maximum horizontal pressure on Steam P= Kayl height of stem = 0.349x17x2.8 IP = 16.612] * Maximum Moment - Plz. 16631x3.22 12 M = 14:19 KNM $ reinforcement (ast): 05.fear ( er bad 0.5X30 46x14:19 X 106 consider b-im = 1000 mm d.250, fck=30, fy=415 Asl = 0.9830 CL-J ,- 46x14:19 xuosa 4100x250 Ast = 1737mm21 Provide 16mm diameter bars at loomm cross section 415 Xloo x 250