Experimental and Modeling Studies for Deformation Characteristics of Coal Mines’ Overburden Soil under Cyclic Loadings in Construction of Haul Roads

The premature failure or early deterioration of mine haul roads due to increasing problems of overrutting, potholes, and excessive settlement is a major issue. These problems mainly arise from the mismatch of overburden soil strength and stresses exerted by moving dumpers, inadequate compaction of soil, and improper assessment of the load–deformation characteristics of overburden soil under repeated loading. In the past, several research studies have been conducted; however, most of the studies are related to the geotechnical characterization and stabilization of mine overburden soil. In this study, the deformation characteristics, i.e., plastic and resilient deformations, of an overburden soil extracted during mining operations have been addressed, taking into account the influence of varying compaction densities, cyclic deviatoric stress, and loading frequencies. Compaction density notably affects soil strength, with 5.82% and 16.4% increases in density resulting in 23%–48% and 297%–410% strength gains, respectively. Meanwhile, cyclic deviatoric stress and confining pressure primarily influenced the axial strain behavior of mine overburden soil subjected to cyclic loading. At higher compaction densities, higher resilient modulus values were obtained. For a confining pressure of 48 kPa, increases of 5.82% and 16.4% in compaction density resulted in an increase in the resilient modulus by 32.6%–48.9%, 36.5%–67.6%, and 73%–201.3%, for increasing levels of cyclic deviatoric stress. The plastic deformations obtained were also notably high. Thus, mine overburden soils with high resilient modulus values can still experience premature failure, owing to the significant accumulation of plastic strain under high repeated deviatoric stresses. From the analysis of test results, three-parameter strain models have also been developed as a function of the number of load repetitions and the applied cyclic deviatoric stress to predict the rutting phenomenon in overburden soil at different compaction densities, applied cyclic deviatoric loads, and loading frequencies.