STRESS-HISTORY BASED MODEL FOR G(E) OF COHESIONLESS SOILS

An empirical, stress-history-based model for the small strain (or elas tic) shear modulus G(e) of cohesionless soils has been developed. Vari ous sands were tested in an 18 cm diameter oedometer equipped with lat eral-stress measuring capabilities and bender elements for propagating and recording elastic waves through the specimens. While previous eff orts have found G(e) scaling with approximately the 1/2 power of confi ning stress (n = 0-5), the present work shows n on virgin loading n1 r anging from 0.39 to 0.72. Furthermore, n1 was shown to be related to t he maximum dimensionless stiffness coefficient for 1-D strain (S1Dmax) . The values of n on unloading and reloading n(u) displayed a much nar rower range than n(l). The average value of n(u) was 0.38, a value muc h closer to the theoretical n = 1/3 for perfect spheres. This is attri buted to the smaller changes in number and quality of intergranular co ntacts during unloading and reloading than during virgin compression. The developed model for G(e) includes overconsolidation ratio (OCR) te rms for the horizontal and vertical directions. However, to implement it. an estimate for the OCR term can be made based solely on the in si tu K0.