Study on liquefaction mechanism of saturated sand considering stress redistribution

•The liquefaction process and mechanism are revealed.•Stress redistribution is achieved by confined test.•A new concept called “continued liquefaction” is proposed.•A new method of building the PWP development model is proposed. Most of the saturated soil in actual condition is anisotropically consolidated, and can liquefy during minor earthquake. Based on the analysis of stress state in actual soil, the present paper considers that the stress redistributed during loading process, which result in the liquefaction. However, in present conventional element tests, the liquefaction in anisotropically consolidated saturated sands (ACS) cannot be induced under dynamic cyclic loading without stress reversal. It contributes to the uncertainty about the liquefaction resistance of soil and the development model of excess pore water pressure (PWP). A brief theoretical interpretation within the theory of limit state of soils is given to explain why the liquefaction in ACS could not be induced using the conventional element test under dynamic cyclic load with low or moderate amplitude, and the validity of the theoretical analysis is verified by experiments. The stress redistribution is realized by confining the lateral deformation based on the conventional test, and the liquefaction in ACS under minor cyclic load is realized. Furthermore, a new concept called “continued liquefaction” is proposed. Apart from “transient liquefaction”, the PWP, the total confining pressure and the total vertical stress are always at the same level, and the mean effective stress of sands is always zero in the “continued liquefaction” stage. Finally, a suggestion that the development model of PWP should be established on the basis of the ratio of the PWP to the initial vertical stress is recommended.