Energy evolution characteristics of frozen silty clay under triaxial cyclic loading and unloading conditions

Objective The evolution of frozen soil energy under external load is an important basis for understanding its deformation mechanism; however, there are few studies on the internal relationship between frozen soil deformation and energy change.

Method Taking frozen silty clay as the test object, a series of triaxial cyclic shear loading and unloading tests under different confining pressures were carried out to explore the deformation characteristics and energy evolution.

Results With the increase of confining pressure, the deviatoric stress corresponding to the same axial strain gradually increased. The stress-strain curve of frozen soil shows strain softening characteristics under low confining pressure, and gradually changes to strain hardening with the increase of confining pressure. When the confining pressure is greater than 6 MPa, the degree of hardening no longer increases. Based on the hysteresis loop area, the calculation method for energy was established.

Conclusion The total energy, dissipation energy, elastic strain energy, and damping energy all show a rapid increase-slow growth-stable pattern with increasing loading–unloading cycles. The shear elastic modulus is positively correlated with the confining pressure and negatively correlated with the number of cycles, and shows a trade-off relationship with the damage variable. The damage variable increases nonlinearly with the increase of dissipative energy. Under the same confining pressure, the slope of damage-dissipated energy curve decreases initially and then increases as dissipated energy accumulates, while the initial slope under different confining pressures also shows a decrease-increase trend. The results can provide a theoretical basis for the construction of frozen soil areas and the design and calculation of artificial frozen foundations.