Abstract:

The cavity expansion theory provides a theoretical basis for the displacement prediction of the installed piles and the analysis of pressuremeter test results. However, there is a lack of systematic analysis of the influences of soil structure in the existing solutions. In this paper, based on the Cemented-CASM considering the cementation effect, an elastoplastic solution for the cylindrical cavity expansion under undrained condition was presented by deriving the elastic-plastic.pngfness matrix reflecting the soil stress-strain relationship in combination with the hardening laws and larger-strain theory. To verify the validation of the present solution, it was compared with the solution in Modified Cam Clay soils when ignoring the soil structure and compared with the numerical results of pressuremeter tests when the soil structure was considered. Parametric analyses were conducted to illustrate the effects of soil structure and destructuration on the cavity expansion process. The results show that the effective stresses and pore water pressure caused by the cavity expansion in structured soils are larger than those in reconstituted soils, while the plastic range around the cavity becomes smaller due to the soil structure. With the damage of the structure, the soil exhibits a strain softening behavior, while the radial stress increases and then decreases as the distance from the cavity wall decreases. When the soil structure is completely destroyed, the effective stresses around the cavity are consistent with those in the reconstituted soils. As the soil structure strengthens, destructuration become faster under the same variation in cavity expansion pressure or cavity radius, and the strain softening behavior becomes more pronounced.

Key words: geotechnical engineering, cylindrical cavity expansion, elastoplastic solution, structured soils, cementation effect, strain softening