A field trial of the reinforcing effect of a stone column in soil

The load-settlement relationship for plate loading of an isolated stone column in soft clay was predicted prior to field testing. The column was constructed by vibro-replacement and, after the test, was excavated to check its dimensions. The theory used was proposed on the basis of laboratory model tests by Hughes and Withers (1974). The purpose was to verifv the theory on a field scale. A standard site investigation supplemented by Cambridge and Menard pressuremeter tests provided basic soil parameters. The ultimate column load depends on the friction angle of the gravel used to form the column, the size of the column formed and the restraint of the clay on the uncemented gravel. To predict the load-settlement curve the essential radial stress-strain data for the clay were obtained from a Cambridge pressuremeter. The prediction is excellent if allowance is made for transfer of load from column to clay through side shear and correct column size. Accurate estimation of column diameter is the major factor i...