Question

The Reinforced concrete cantilever retaining wall has a cohesionless backfill soil with unit weight of 17 kN/m3 (above GWT) and 20 kN/m (saturatec). The resisting moment about the toe, due to the weight of the backfill soil, is 10 kN/m2 100kN 0.4m 2.6 m 3.9m GWT 2.7 m 0.4m concrete 23.5 kN/m3 4.0m

Answer 1

Given unit weight of soil above water table=17 kN/m³

Unit weight of saturared soil=20 kN/m³

Fruction angle if soil=38°

Active pressurre coefficient=(1-sin38)/(1+sin38)=0.237

Unit weight if water=9.8 kN/m³

Surcharge=10kN/m²

Lateral pressure due to surcharge=0.237*10=2.37 kN/m²(along the entire height of wall)

Earth pressure at topmost point of wall=0

Earth pressure at 3.9 m from top of wall=0.237*17*3.9=15.71 kN/m²

Unit weight of submerged unit weight of soil=20-9.8=10.2 kN/m³

Active earth pressure at bottom of wall=0.237*10.2*(3.9+2.7-0.4)=14.99 kN/m²

Hydrostatic pressure at bottom of wall=9.8*(2.7-0.4)=22.54 kN/m²

Total pressure at bottomnof wall=14.99+22.54=37.53 kN/m²

Total lateeal.load due to surcharge=2.37*6.2=14.69 kN

Total lateral load due to earth pressure abive watee table=0.5*3.9*15.71=30.63 kN

Total lateral load due earth presure below watee table=0.5*2.3*(15.71+37.53)=61.23 kN

Total force=14.69+30.63+61.23=106.55 kN

This load is per unit length of wall