Study On Temperature Effect Of Shear Strength Of Hydrated Needle-Punched GCL Composite Liner

The GM+GCL composite liner which consist of geomembrane(GM)and geosynthetic clay liner(GCL)is one of the most common impermeable structures used in landfill.Shear strength of GM/GCL interface and GCL internal interface are usually controlled the slope sliding stability of the composite liner which containing GCLs.The existing researches on the characteristics of the composite liner shear strength are commonly conducted under the normal temperature of 25?.However,due to a variety of biochemical reactions,sunlight exposure and seasonal alternation.The temperature of the landfill has a large changes interval.In this paper,in order to reveal the shear properties of GCL liner under the influence of temperature changes.A lot of temperature-controlled shear texts have been carried out on the whole composite liner and the interfaces of various geosynthetics which composite the GCL liner.Based on the test results and phenomena,gradually analysed the shear characteristics of the geosynthetics interfaces and the composite liner under the influence of temperature changes,proposed the shear failure mechanism and established the temperature effect model of each interface.The main research work includes the following parts:(1)A large-scale temperature-controlled shear apparatus is designed and manufactured,and the temperature-controlled shear text method which suitable for geosynthetics interfaces and the whole composite liner is proposed.The accuracy of the apparatus and the rationality of the test method are verified by early repeated tests.(2)Large scale direct shear tests were carried out on the interface of smooth geomembrane(GMS)/non-woven geotextile(GT),textured geomembrane(GMX)/GT and GMX/GCL under constant temperature condition.By comparing the shear test results and phenomena of these different interfaces which composed of three similar materials,the interrelation and the causes of their interface shear strength are established and analyzed.The shear failure mechanism and strength characteristics of the interfaces of geomembrane(smooth and textured),geotextile and GCL are proposed.(3)Based on the shear test results and failure mechanism of GMS/GT and GMX/GT under constant temperature condition,further carried out a large number of temperature-controlled shear tests on GMS/GT and GMX/GT at different temperature conditions.By comparing the shear test results and phenomena,the influence of temperature effect on the shear strength and failure mode of GMS/GT and GMX/GT are analyzed,the shear failure mechanism of these two interfaces under the influence of temperature are proposed,and the temperature effect model of the shear strength of there two interfaces are established.(4)A large number of temperature-controlled simple shear tests of GM+GCL composite liner were carried out under different temperature conditions.Based on the test results and phenomena,the shear failure mechanism of GM+GCL composite liner and the extrusion mechanism of hydrated Bentonite in GCL under the influence of temperature effect are proposed.Duncan-Chang model is used to fit the peak shear strength of composite liner under each test temperature,and the functional relation between model parameters and temperature is established to obtain the peak shear strength temperature effect model of GM+ GCL composite liner.