Subgrade reaction modulus of rock masses under the load of single and multiple footings

Abstract

ABSTRACT Subgrade reaction modulus is an essential parameter in the structural design of footings. Determination of this parameter is difficult, especially in rock masses containing an irregular distribution of discontinuities. In this paper, the subgrade reaction modulus of rock masses obeying Hoek-Brown failure criterion was investigated. It was assumed that the rock masses are under the pressure of a single isolated footing and also two adjacent strip footings. The subgrade reaction modulus was determined from the pressure-settlement curve of the rock masses. This study’s results were presented in two forms, which include the subgrade reduction factor and the interference coefficient. The obtained results show that the subgrade reaction modulus of rock masses may be smaller than 50% of intact rocks. Likewise, based on the distance between the multiple footings, the subgrade reaction modulus may be in the range of 0.7 to 1.3 times the subgrade reaction modulus in the case of a single isolated footing.