湿干循环作用对冻土-复合土工布界面常法向应力剪切特性的影响试验研究

Experimental study on the effect of wet-dry cycles on constant normal stressshear characteristics of frozen soil-composite geotextile interface

土工合成材料广泛应用于寒区工程建设,但土体与材料界面的剪切强度是其薄弱环节。受降雨、灌溉等因素影响,土体在一定深度范围内经历湿干循环作用。为研究湿干循环作用对冻土与土工合成材料界面剪切强度的影响,本文基于控温直剪仪对粉质黏土-复合土工布在常法向应力条件下界面剪切特性开展试验研究,试验因素包括湿干循环次数、温度和法向应力。结果表明,常温条件下湿干循环对界面剪切强度有劣化作用,负温条件下界面剪切强度随湿干循环次数增大整体呈现增大趋势,经过一定循环次数后趋于稳定。湿干循环作用下界面黏聚力和内摩擦角的变化规律与界面剪切强度变化规律相对应,而界面黏聚力的变化是引起剪切强度变化的主要因素。通过对剪切强度的影响变量及其交互作用进行显著性分析,发现法向应力、冻结温度和湿干循环次数均对剪切强度有强显著影响,法向应力和温度的交互作用以及温度和湿干循环次数的交互作用也对剪切强度有显著影响。本文研究成果可为复合土工布在冻土工程中的应用提供参考。

Geosynthetics is widely used in civil engineering in cold regions,but the shear strength of the inter-face between soil and geosynthetics is weakly.Influenced by rainfall,irrigation and other factors,the soil under-goes wet-dry cycles in the shallow,which affects the shear strength of the interface between soil and geosynthet-ics.In this paper,based on the temperature-controlled direct shear apparatus,a series of experimental research on the shear characteristics of clay-composite geotextile interface under constant normal stress are carried out,and the test factors include the number of wet-dry cycles,temperature and normal stress.The results show that the shear stress-displacement curves at room temperature are all hardening type under different numbers of wet-dry cycles,and more visible at the higher normal stress.While the curve tends to soften at the decrease of tem-perature and the increase of numbers of wet-dry cycles.The wet-dry cycle has a deteriorating effect on the inter-face shear strength under room temperature conditions,especially the first wet-dry cycle.In contrast,the inter-face shear strength under negative temperature conditions shows an overall trend of increasing with the number of wet-dry cycles,and tends to stabilize after a certain number of cycles.Taking the condition of-6℃as an ex-ample,the shear strength of the sample no longer increases after 5 wet-dry cycles.Under the action of wet-dry cycles,the change rule of interface cohesion and internal friction angle corresponds to the change rule of inter-face shear strength,but the change of interface cohesion is the main factor that causes the change of shear strength,that it is average increase more than 10%under different temperature after 10 wet-dry cycles.Through significance analysis of the influence variables of shear strength and their interaction,it is found that normal stress,freezing temperature and the number of wet-dry cycles have strong significant influence on the shear strength,and the interaction between normal stress and temperature,and the interaction between temperature and the number of wet-dry cycles also have significant influence on the shear strength.