加筋红砂岩风化土强度和变形特性

CHARACTERISTICS OF SHEAR STRENGTH AND DEFORMATION OF REINFORCED RED SAND SILTY CLAY WITH GEOSYNTHETICS

红砂岩风化土是湖南公路路堤工程中应用较多的填筑材料,采用直剪试验研究了不同压实度的红砂岩风化土的强度和变形特性,以及加筋对其工程性质的影响。试验表明,随压实度增大,红砂岩风化土的峰值抗剪强度明显提高,但主要由粘聚力的增大引起,随剪切位移增大,粘聚力减小,抗剪强度大幅度降低,其应力–应变曲线呈现随应变软化型。加筋提高了红砂岩风化土的峰值抗剪强度和残余强度,更重要的是明显减小了峰值后强度的降低幅度,且达到峰值抗剪强度的剪切位移增大,峰值区域增宽,土体延性提高,改善了红砂岩风化土的强度和变形特性;对于不同的加筋层数和不同的筋材模量,以及在不同的压实度和试验竖向压力下,加筋对红砂岩风化土的强度和变形特性的改变不同;根据试验结果,还对红砂岩风化土的工程性质以及加筋的抗剪作用机理进行了初步探讨,阐述了加筋材料在土的应力–应变关系中的主要功能和作用。

Red sand silty clay is used widely in highway engineering in Hunan Province. The direct shear tests on red sand silty clay with various geosynthetics were carried out to investigate the strength and deformation performances, the influence of parameters such as reinforcement layers and modulus, soil compactness, as well as confining pressures of test. Results show that with increasing compactness, the shear strength of soil increases significantly, but this is mainly caused by cohesive forces, which will disappear gradually with shear displacement increasing, and usually the stress-strain curve of red sand silty clay has a strain-softening phase. Reinforcement improves the stress-strain behaviors of red sand silty clay that both the peak strength and residual strength are increased, but the most important is the amount of reduction of residual strength, and the peak shear strength arrives at a larger shear displacement; as a result, the soil becomes more ductile. Based on the test results, the mechanism of the shear strength of reinforced soil is proposed tentatively; and the role and function of reinforcement in the stress-strain behaviors are also illustrated.