基于大型三轴试验的红砂岩粗粒土强度与变形特性研究

Study on the strength and deformation characteristics of red sandstone coarse-grained soil based on large-scale triaxial tests

红砂岩粗粒土常作为我国南方地区的路基填料,因其易发生颗粒破碎而影响路基的安全稳定性,故深入开展其力学特性研究十分必要。文中选取湘南地区的红砂岩为研究对象,对其开展大型三轴试验,研究不同粗颗粒含量的试样在不同围压、不同压实度下的强度与变形特性。试验结果表明:在低围压时,粗颗粒含量较少的试样变形特性表现出应变软化,而在高围压时,表现为应变硬化特性;对于粗颗粒含量较多的粗粒土,在不同围压下均表现出应变硬化特性。在压实度相同的情况下,随着围压增大,峰值强度逐渐增大,应变硬化特征更趋明显。在围压和级配不变的情况下,随着压实度提高,抗剪强度逐渐增大,表现出低压实度应变软化向高压实度应变硬化特性的转变。应力-应变曲线表明,峰值强度与粗颗粒含量、围压、压实度具有良好正相关关系。通过绘制莫尔圆,发现其强度包络线表现为非线性,可采用幂函数进行拟合。计算结果表明,内摩擦角随着围压的增大而逐渐减小。

Red sandstone coarse-grained soil is often used as a roadbed filler in southern of China. As it is prone to particle breakage and affects the safety and stability of the roadbed,it is necessary to conduct in-depth research on its mechanical properties. In this paper,the red sandstone coarse-grained soil in southern region of Hunan is selected as the research object,and performing a large-scale triaxial test to discuss the strength and deformation characteristics of samples with different coarse particle contents under different confining pressures and different degrees of compaction.The test results show that at low confining pressure,the deformation characteristics of samples with less coarse particles show strain softening,while at high confining pressures,they show strain hardening characteristics.For coarse-grained soils containing more coarse particles,it displays characteristics of strain hardening under different confining pressures. In the case of the same degree of compaction,as the confining pressure increases,the peak strength gradually increases,and the strain hardening characteristics become more obvious.Under the condition of constant confining pressure and gradation,as the degree of compaction increases,the shear strength gradually increases,showing the transition from strain softening in low-pressure compaction to strain hardening characteristics in high-pressure compaction. The stress-strain curve shows that the peak strength has a positive correlation with the content of coarse particles,confining pressure and degree of compaction.By drawing the Mohr circle,founding its intensity envelope is nonlinear,and using a power function for fitting. The results show that the internal friction angle gradually decreases with the increase of pressure.