A sandstone bed with RQD 5 70% and g 5 26.0 kN/m3 lies beneath 1.5 m of overburden soil. A 2.0 m 3 2.0 m square foundation is to be placed on top of the sandstone rock (i. e., at a 1.5 depth below the ground level) to carry a column load. The unit weight of the soil is 18.0 kN/m3. Assuming the rock strength parameters from Problem 7.17

Awall of 0.5m thickness is to be constructed from a material which has average thermal conductivity of 1.4 w/mk. the wall is to be insulated with a material having an average thermal conductivity of 0.35 w/mk so that heat loss per square meter shall not exceed 1450 w. assume inner wall surface temperature of 1200°c and outer surface temperature of the insulation to be 15°c. calculate the thickness of insulation required.