冻融循环对泥炭土力学特性及微观结构演化的影响研究OA

This study investigates the mechanical properties and microstructural evolution of peaty soils under freeze-thaw(F-T)cycles through unconsolidated undrained(UU)triaxial shear tests and scanning electron microscopy(SEM).The effects of F-T cycles(0-30),confining pressure(100-400 kPa)and fiber content(0％-12％)were systematically evaluated.Results indicate that the ultimate strength and shear strength decrease as the number of freeze-thaw cycles increases,with the most pronounced reduction occurring during the first 5 cycles.Beyond 15 cycles,the rate of decrease diminishes,and the curves tend to flatten.The fiber reinforcement significantly mitigates the strength degradation caused by freeze-thaw cycles.The most significant improvement is observed at a fiber content of 12％.The fibers act as bridging elements that improve soil particle connectivity,thereby strengthening cohesion and mitigating particle displacement and deformation during freeze-thaw processes.SEM analysis reveals that fiber-soil interaction mechanism undergoes a progressive transformation with increasing fiber content,evolving from localized fiber embedding to comprehensive network formation through fiber entanglement.This structural evolution establishes robust inter-aggregate connections that enhance the soil matrix integrity.Following 30 freeze-thaw cycles,no apparently penetrating fissure was formed although the freeze-thaw process damaged the connection between fibers and soil aggregates,demonstrating the effectiveness of fiber reinforcement in mitigating freeze-thaw damage.These findings provide critical insights into the microstructure-mechanical properties relationships of peaty soils,offering practical guidance for foundation treatment in seasonal frozen peat regions and controlling the engineering diseases problems.