Abstract
To address the environmental concerns of oil shale waste (OSW) accumulation and improve road engineering sustainability, this paper proposes a novel cold resistance structure (CRS) incorporating extruded polystyrene (XPS) insulation plates and OSW-modified soil. OSW primarily consists of two components: residual semi-coke from retorting processes and combustion-derived ash residues. The improper disposal of accumulated OSW poses significant environmental risks. Following a comprehensive feasibility assessment, this study identifies the application of OSW in highway subgrade construction as an eco-friendly solution that achieves triple objectives - waste valorization, pollution mitigation, and alleviation of material shortages in road infrastructure. Targeting the freeze-thaw challenges prevalent in northeast China's road structures, the CRS system combines XPS insulation technology with OSW-modified subgrade soil through three key phases. First, the optimal XPS plate thickness was determined using thermal resistance equivalence principles. Second, controlled freeze-thaw experiments employing a specialized unidirectional testing system evaluated the CRS's frost resistance through triplicate comparative trials. Third, field validation involved constructing a CRS test road and conducting in-situ assessments of bearing capacity and dynamic stress responses, with conventional sand-gravel subgrade sections serving as controls. Environmental impacts and economic viability were systematically analyzed. Results demonstrate that the CRS system reduces the subgrade freezing depth by up to 52.8%, limits surface water migration by over 60%, and decreases dynamic stress amplitudes by more than 50% compared to conventional structures. The effective stress buffering depth of the XPS insulation is equivalent to an 89.75 cm thick gravel layer, while subgrade deflection is reduced by 21%. Additionally, the CRS system achieves a 43% reduction in material cost per kilometer and enables the reuse of over 9300 tons of solid waste, offering both economic and environmental benefits.