Large‐Scale Loading Tests of Shallow Footings in Pneumatic Caisson

Abstract

A series of large‐scale loading tests of square and rectangular footings on a naturally deposited dense scoria (a granular material produced by volcanic activities) was conducted in a pneumatic caisson. Standard penetration tests (SPTs) showed that the blow counts required for a 30‐cm penetration (TV‐value) were more than 70. This paper presents the method of the loading tests, characteristics of load‐settlement relations and failure mechanisms observed. The test results showed that bearing‐capacity factors decreased with increasing footing size. A set of stress characteristic equations incorporating stress dependency of angle of shearing resistance was solved numerically by use of the finite difference method to interpret the experimental data. Parameters required for the numerical computations were determined from the triaxial compression test data on an undisturbed sample. Good agreement was obtained between the numerical results and the experimental observations. A close examination of the failure mechanisms revealed that visible shear bands were developed because of particle crushing during shearing under high pressure.