A study of the mechanical characteristics of structured soft clay under impact loading

To examine the great effect of impact loading on the soil mechanic characteristics, impact loading was simulated by hollow cylindrical torsional shear apparatus using the Tianjin coastal structural soft clay. The mechanical characteristics of the structural soft clay under different experimental conditions are comparatively analyzed from the results of non-consolidation and non-drainage triaxial tests before and after impact loadings. The experiments results show that the soil exhibits weak strain softening in the conventional triaxial shear tests under the low confining pressure, and the shear strength envelope of the soil is approximately fit by two straight lines other than one straight line. In the impact loading tests, the axial strain, pore pressure and the peak values of the principal stress difference grow with the increasing impact loading. After the impact loading, the soft clay shows strain hardening under all kinds of confining pressures in the triaxial shear tests, and the peak values of the principal stress difference reduces drastically. The shear strength envelopes of soils are straight lines, and the values of c, φ are far less than the values of the soil which were impacted. Finally, the influence of impact loading to the strength of the soft clay was summarized and analyzed, and the relationship between the strength reduction, confining pressure and impact loading were proposed with the fitting formula. The results of tests for determining the strength of structural soft clay under the impact loading has a guiding significance in practical engineering.