Post-liquefaction shearing behaviour of saturated gravelly soils: Experimental study and discrete element simulation

To investigate the post-liquefaction shearing behaviour of saturated gravelly soil, laboratory tests were conducted using a static-dynamic multi-purpose triaxial apparatus. In addition, numerical simulations using the discrete element method (DEM) were performed to preliminarily understand the micro-mechanism of gravelly soil in monotonic loading after liquefaction. The influences of dry density, initial confining stress and degree of liquefaction on the post-liquefaction shearing behaviour of gravelly soil were discussed, and the evolution of the micro-parameters of the granular system was also analysed. The results show that the stress-strain responses of gravelly soil after liquefaction can be divided into three stages: (1) low strength stage, (2) super-linear strength recovery stage, and (3) sublinear strength recovery stage, which are distinctly different from those of the general saturated gravelly soil without previous cyclic loading. The initial state and prior dynamic stress history have significant influences on the post-liquefaction shearing behaviour of gravelly soil. The DEM simulation revealed that the average coordination number sharply increases, the contact normal shows an obvious orientation distribution, and the destroyed force chain backbones are reconstructed in the monotonic reloading process after liquefaction. The evolution of the micro-parameters of the granular system clearly reflects the interior interaction process and micro-mechanisms in the particles during the three different stages of the macro-mechanical behaviour of gravelly soil.