Laboratory test and prediction model of dynamic resilient modulus of carbonaceous mudstone coarse-grained soil

Abstract

Carbonaceous mudstone is widely distributed in southwest China. With the rapid development of transportation construction in this region, the use of carbonaceous mudstone for subgrade filling has good economic and environmental benefits. At present, studies on the dynamic characteristics of carbonaceous mudstone coarse-grained soil are few. The shape characteristics of mudstone particles and the compaction characteristics of subgrade fillings with different grades are analyzed then dynamic triaxial tests are conducted to explore the variation of the dynamic resilient modulus MR of carbonaceous mudstone coarse-grained soil under different stresses and physical states. The influence of different gradation, confining pressure σ3, dynamic deviatoric stress σd, moisture content w, and degree of compaction K on MR of carbonaceous mudstone coarse-grained soil was studied. Results indicate that the particle shape index of carbonaceous mudstone is insensitive to particle size. With the increase in the gradation parameter D, the optimal moisture content wopt of the sample increases, whereas the maximum dry density ρdmax initially increases, and then decreases. MR is positively correlated with σ3 and K, but negatively correlated with σd and w. The decrease of MR caused by w decreases gradually with the increase of D. When w≤ 1.1 *wopt, the increase in D reduces MR, but when w= 1.2 *wopt, the trend changes to a positive correlation between MR and D. Carbonaceous mudstone subgrade filling can be used for the highway with light or medium traffic load grade. The recommended gradation parameter D ranges from 2.43 to 2.63. A resilient modulus prediction model considering the influence of gradation, stress state, moisture content, and physical state is proposed and its rationality is verified. The research results can provide reference for the design of carbonaceous mudstone coarse-grained soil subgrade.