Experimental study on dynamic elastic modulus of thawing subgrade sandy loam soil under vibration load

Railway construction in the Arctic sandy loam region of the Russian Federation is developing continuously. Due to global warming, permafrost degradation is inevitable. Thawing of permafrost will inevitably reduce the deformation resistance of the subgrade, affecting the safety of railway operation. The soil's dynamic elastic modulus (E_d) is the most important factor in studying the dynamic response of subgrade under train loads. Based on dynamic triaxial tests, the research deals with the change regularities in the E_d of thawing sandy loam soils under different conditions of temperature, water content, confining pressure and loading frequency. The regression function of the thawing sandy loam soil E_d under various single factors was constructed. Based on the correlation assessing rule, a multivariate linear regression function between thawing sandy loam soil E_d and multiple factors was established. The prediction error of this function ranges from −8.33 % to 7.14 %. The results show that water content has the greatest influence on the E_d of thawing sandy loam soil, and its influence weight coefficient is 51.07 %, followed by loading frequency, temperature and confining pressure. Based on Pearson correlation coefficient and Spearman rank correlation coefficient, it can be seen that temperature and water content are negatively correlated with the E_d, while confining pressure and loading frequency are positively correlated with the E_d. In general, the proposed prediction model can effectively solve the non-linear problem between the E_d of thawing sandy loam soil and the influencing factors, thus providing valuable support material for studying dynamic response of subgrades operating in permafrost areas during thawing period.