Assessment of Deterioration Characteristics of Solid Waste-Based Binder-Stabilized Laterite Under Multiple Environmental Factors Based on Micro-Drilling Resistance

Solid waste-based binder-stabilized laterite is prone to progressive deterioration under multiple coupled environmental factors in practical engineering applications. Conventional compression and direct shear tests fail to accurately characterize the gradient deterioration pattern of stabilized laterite specimens. In this study, a multi-factor test scheme was designed using response surface methodology, with wet–dry cycle number, initial humic acid content, and magnesium sulfate solution concentration selected as environmental factors. Continuous drilling resistance–drilling depth curves of stabilized laterite specimens were obtained using a drilling resistance measurement system, thereby quantitatively determining the deterioration depth and indirectly characterizing structural integrity via the drilling resistance in the stable drilling stage. Scanning electron microscopy observations were used to reveal the microscopic deterioration mechanism of stabilized laterite under the effects of environmental factors. The results of the regression show that the micro-drilling resistance in the stable drilling stage of undeteriorated stabilized laterite has a significant linear correlation with shear strength, indicating that micro-drilling resistance, as an indirect index of specimen integrity, also has potential for application in evaluating the strength of stabilized laterite. All three environmental factors increase the deterioration depth of stabilized laterite; wet–dry cycles exert the most significant effect and exhibit a statistically significant interaction within the investigated experimental domain with humic acid content, followed by magnesium sulfate concentration. For stabilized laterite subjected to wet–dry cycles and sulfate attacks, there exists a change point depth on the drilling resistance curve. Below this depth, the average micro-drilling resistance of the interior soil is mainly governed by the initial humic acid content. Microscopically, humic acid particles form weakly cemented zones in surrounding areas, which gradually evolve into preferential flow paths under wet–dry cycles, accelerating water infiltration and expanding deterioration depth. Magnesium sulfate crystallizes within pores to generate ettringite and other products, inducing extrusion stress on the cemented structure and further aggravating soil loosening and microcrack propagation.