红层泥岩填料强度特性及石灰改良效果研究OA

Objective Red mudstone,a prevalent geological material in China,is frequently encountered during slope excavation and tunnel construction projects.These activities inevitably produce substantial amounts of red mudstone waste,creating significant challenges for disposal and environ-mental management.In addition,red mudstone waste exhibits high susceptibility to weathering,fragmentation,and water-induced disintegration and softening,which limits its engineering applications.Currently,it primarily serves as subgrade fill material.If red mudstone waste is improved for use as subgrade fill material,it reduces waste generation,expands application scenarios,and contributes to waste reduction,pollution control,and resource efficiency. Methods This study investigated the shear strength characteristics of red mudstone fill material and lime-stabilized fill material,and analyzed the influence of the degree of saturation on the strength properties of red mudstone fill.The effects of lime content and curing age on the strength characteristics and dilatancy behavior of stabilized fill were clarified.In addition,scanning electron microscopy(SEM),mercury intrusion poro-simetry(MIP),and X-ray diffraction(XRD)tests were conducted to reveal the stabilization mechanisms of lime-stabilized red mudstone fill mate-rial at the microscopic level. Results and Discussions The experimental results indicated that the cohesion of red mudstone fill material initially increased with the degree of saturation but then decreased,and reached its peak near the optimum water content.This strength variation demonstrated a typical"peak effect"in which cohesion followed a quadratic function relationship with degree of saturation,while the internal friction angle decreased based on a power function.The cohesion of red mudstone fill material reached its maximum near the optimum water content,whereas the internal friction angle significantly increased under drier conditions,which indicated that red mudstone fill material achieved higher shear strength in a relatively dry state.Compared to the fill material at its optimum water content,the cohesion of saturated red mudstone fill material significantly decreased to only 12.5%of its peak value,while the internal friction angle remained at 86%of its optimum state,which indicated that the substantial reduc-tion in shear strength after saturation was primarily attributed to cohesion loss.Drainage and waterproofing measures should be emphasized in red mudstone subgrade construction to mitigate water-induced softening and excessive settlement.After lime stabilization,the cohesion of saturated red mudstone fill increased by more than 6.5 times,and the internal friction angle increased by over 1.4 times,which significantly enhanced the shear strength.In addition,the shear behavior transitioned from strain hardening and shear contraction in untreated samples to strain softening and shear dilation in lime-stabilized samples.The pore structure of lime-stabilized fill remained essentially unchanged after saturation compared to the unsaturated state,and retained a bimodal distribution.With increasing curing age,the proportion of micropores decreased,while nanopores became more prevalent.In addition,lime treatment maintained the particle integrity of red mudstone fill material and formed a three-dimensional interlocking framework that strengthened interparticle bonding,markedly improving shear strength compared to untreated red mudstone fill material. Conclusions The findings of this study provide theoretical guidance for the design,construction,and engineering application of improved red mudstone subgrades and further raise the resource utilization of red mudstone waste in high-speed railway construction.