THE VARIATION OF CRITICAL-STATE PARAMETERS WITH WATER-CONTENT FOR 2 AGRICULTURAL SOILS

Triaxial tests were conducted on 436 reconstituted samples of two agri cultural soils (a sandy loam and a loam) at moisture contents from air dryness to close to the respective liquid limits. Volume-change behav iour was largely consistent with the critical-state concept, the role of soil-moisture content being expressed in the values of the measured critical-state parameters. The most important parameters, and their i nherent variability, have been specified. Most of the parameters varie d systematically with soil-moisture content, but differently for the t wo soils. Some of the parameters were linearly correlated. The specifi c volume (v) was a linear function of the logarithm of the mean normal stress (ln p) during normal compression and along the critical-state line (CSL) with significantly different gradients (lambda and lambda, respectively) at most moisture contents except close to the liquid li mits. The standard errors of lambda were typically of the same magnit ude as the gradients found during hydrostatic unloading from two diffe rent v-levels whereas the standard errors of A were up to a factor of ten smaller. The linear projections of the CSLs on the deviatoric stre ss (q)-mean normal stress plane showed intercepts on the q-axis. Gener ally, precompaction leading to brittle failure had very little influen ce on the shear strength as compared with the strength in critical sta te.