STUDY OF CRITICAL EXIT GRADIENT WITH RESPECT TO PARTICLE SIZE AND GRADATION OF SANDY SOILS

Abstract

Sandy foundations subjected to underseepage are suscep-tible to quicksand phenomenon at the exit point. Review of studies made by various researchers with respect to critical exit gradient of sandy soils clearly indicates the desirability of further study on a mixture of sand and gravel to simulate the field conditions. in view of this, effect of particle size and gradation has been studied with the help of a quick-sand tank setup. Particle size and gradation have no significant effect on the theoretical critical exit gradients. However, the ex-perimental critical exit gradient increases with the increas-ing gradation but shows no proper trend with respect to parti-cle size. It is further inferred that is is less than and bears a relation, is 5). The permeability of uniform as well as graded sands has been found to bear a relation with the effective size and gradation of soils given by k = 100 [CU /C ] where k is the flarcy's coefficient of permeability in cm/sec. and D10 is the particle size or effective size in cm.