Study on the damage mechanism of subgrade in seasonal frozen soil region under dynamic loading

Abstract

Highway subgrade constructed in seasonal frozen soil region of Northeast China is subject to damage under dynamic loading of vehicles and alternating seasonal temperatures. In order to investigate the damage mechanism of the subgrade in the seasonal frozen soil region, indoor tests were conducted. It was found that the dynamic load has a large effect on the temperature field, moisture distribution, and pore water pressure distribution of the subgrade. Under the repeated cycles of dynamic loading, a region of high pore water pressure and high pore water pressure gradient was formed below the load. In addition, a region of high temperature gradient was formed at the same location under the influence of cyclic temperature changes. The combined effect of the temperature gradient and the pore water pressure gradient redistributes water in the soil, resulting in moisture gathering below the load and an increase in soil moisture content, leading to an increase in frost heave during freezing. During the thawing period, the thawing of permafrost reduces its strength, and the gathering of moisture under the load caused by dynamic loading will become an inducing factor for the damage of the subgrade. This study provides a novel explanation for the damage of subgrade in seasonal frozen soil regions during the spring thaw period. It also suggests strengthening the base layer during subgrade construction to reduce the impact of traffic loads on the subgrade during the spring thaw period.