残坡积粉质黏土遇水强度衰减机制及其稳定性评价模型优化

Strength attenuation mechanism and stability evaluation modeloptimization of eluvial silty clay under water action

本文以大渡河某公路工程区残坡积粉质黏土为研究对象,通过一系列试验对其遇水后强度变化规律及衰减机制展开研究,并优化该类边坡稳定性评价模型。研究表明:随含水率提高,残坡积粉质黏土剪应力—剪切位移曲线由应变硬化型向应变软化型发展,而饱水后剪应力—剪切位移曲线基本保持为低缓的应变硬化型特征,抗剪强度呈现出持续衰减直至稳定的发展趋势。粉质黏土强度参数均随含水率提高而快速降低,黏聚力水敏感性强于内摩擦角,研究构建出黏聚力、内摩擦角与含水率的函数模型;以饱水24h为临界时间点构建强度参数与饱水时间的分段函数。受粉质黏土中黏土矿物与少量易溶矿物影响,遇水后土体内水解、化合、置换反应将导致细观结构损伤缺失,加之孔隙水对细小矿物颗粒的润滑、软化作用,综合导致摩擦强度、黏聚强度的降低,进而表现为粉质黏土力学强度衰减。以瑞典条分法为基础,结合粉质黏土在不同含水率、饱水时间条件下的强度变化函数规律,优化建立由非饱和至持续饱和状态下的稳定性评价过程模型。

Taking the residual slope silty clay in a certain highway engineering area of Daduhe River as the study object,a series of physical and mechanical tests are carried out to study its strength change law and attenuation mechanism after encountering water,and the stability evaluation model is optimized.The study has found that as the water content increases,the shear stress-strain displacement curve of the residual slope silty clay develops from strain hardening type to strain softening type.However,after saturation,the shear stress-strain displacement curve basically maintains a low and gentle strain hardening type characteristic,and the shear strength shows a continuous decline until stable development trend.The strength parameters of the silty clay rapidly decrease with the increase of water content,and the cohesion for water sensitivity is stronger than the internal friction angle.A function model of cohesion,internal friction angle and water content has been developed;a segmented function between strength parameters and saturation time at a critical time point with 24 hours saturation is constructed.Affected by clay minerals and a small amount of soluble minerals in the silty clay,the hydrolysis,combination and displacement reactions in the soil after encountering water will lead to the loss of microstructure damage.In addition, the lubrication and softening effect of pore water on small mineral particles will comprehensivelylead to the decrease in friction strength and cohesive strength, which in turn manifests as the decrease inthe mechanical strength of silty clay. Based on the Swedish slice method and combined with the strengthvariation function of silty clay under different water content and saturation time conditions, an optimizationprocess model for stability evaluation from unsaturated to continuously saturated state is established.