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