花岗岩残积土的室内外剪切特性对比

Shear Property of Granite Residual Soil Based on Laboratory and In-situ Direct Shear Test

为研究花岗岩残积土的剪切特性,分别进行了不同含水率下未扰动土和重塑土试样的室内直剪试验及原位试样的原位大型直剪试验,分析了花岗岩残积土的室内外剪切特性及差异性。结果表明:花岗岩残积土的结构性显著,扰动对其结构性的损伤具有不可逆性;未扰动土试样的应力应变关系特征以应变硬化型为主,并有应变软化型;重塑土试样的应力应变关系特征基本为应变硬化型;原位试样的应力应变关系特征以应变软化型为主,兼有应变硬化型;原位试样的黏聚力分别为未扰动土试样、重塑土试样的2.2倍和2.6倍,内摩擦角分别为未扰动土试样、重塑土试样的2.7倍和3.1倍;黏聚力受花岗岩残积土中细粒土的显著影响,随含水率的增大而减小;内摩擦角主要取决于花岗岩残积土中的粗粒土,随粗粒含量的增大而增大,与含水率的相关性很小;原位大型直剪试验更适宜于准确获取花岗岩残积土的抗剪强度指标,可为花岗岩残积土路堑高边坡的稳定性分析提供支撑。

To study the shear properties of granite residual soil,the laboratory direct shear tests on undisturbed soil and remodeled soil samples with different water contents,and the in-situ large-scale direct shear tests on in-situ samples were carried out respectively.The laboratory and field shear strength properties and differences of granite residual soil were analyzed.The result indicates that the structural properties of granite residual soil are significant,and the disturbance has irreversible damage to its structure.The stress-strain relation characteristics of undisturbed soil samples are mainly strain hardening type,and with strain softening type as well.The stress-strain relation characteristics of remolded soil samples are basically strain hardening type.The stress-strain relation characteristics of in-situ specimens are mainly strain softening type,and with strain hardening type as well.The cohesive forces of in-situ samples are 2.2 and 2.6 times that of the undisturbed and remolded soil samples,and the internal friction angles are 2.7 and 3.1 times that of the undisturbed and remolded soil samples respectively.The cohesion is significantly influenced by fine-grained soil,and decreases with the increase of water content.The internal friction angle mainly depends on the coarse-grained soil in granite residual soil,which increases with the increase of coarse-grained content,and has little correlation with water content.The in situ large-scale direct shear test is more suitable for accurately obtaining the shear strength indicator of granite residual soil,that can provide support for the stability analysis on granite residual soil cutting high slope.