A retaining wall $6$ m high with smooth vertical back supports a cohesive backfill having unit

weight $18$ kN$/$m$3$

$,$ apparent cohesion $26$ kN$/$m$2$

and angle of internal friction zero. Derive the

formula for active earth pressure and calculate

$(2+2+2+2+2+2)$

a$)$ Active pressure intensity at the top of the wall

b$)$ Depth of tension crack

c$)$ Active pressure intensity at the base

d$)$ Resultant earth pressure considering soil cannot take tension