聚丙烯纤维对风积沙改性土三轴压缩特性的影响研究

Study on the influence of polypropylene fibers on triaxial compression properties of aeolian sand modified soil

为了研究聚丙烯纤维加固风积沙改性土(95%风积沙+5%水泥)的效果和机制,改善风积沙改性土的脆性破坏特性,将聚丙烯纤维以0.1%、0.2%和0.4%质量百分比掺入到风积沙改性土中,进行固结不排水三轴压缩试验。试验结果表明:风积沙改性土的应力-应变曲线具有弹塑性变形特征,应变初始阶段出现应力陡增的孔隙压密期后有完整的弹性阶段、塑性变形阶段和破坏阶段;聚丙烯纤维的掺入增加了土样的塑性变形能力,提高了残余强度,破裂面因纤维的拖拽牵引而呈现圆弧形,抑制了土样的脆性破坏,增加了其延展性;风积沙改性土的内聚力随着聚丙烯纤维含量的增大而增大,基本呈线性正相关关系,内摩擦角随着聚丙烯纤维含量的增大而减小,整体呈现负相关关系;风积沙改性土的峰值应变随着聚丙烯纤维含量的增大而增大,应力-应变曲线由应变软化转变为应变硬化型,可用双曲线进行有效拟合;同一围压下应力-应变双曲线拟合模型参数b随聚丙烯纤维的含量增大而减小,在同一聚丙烯纤维含量下,模型参数b均随围压的增大而减小。本文研究成果可为风积沙改性土的实际工程应用提供试验参考。

To study the effect and mechanism of polypropylene fibers in reinforcing aeolian sand modified soil(95%aeolian sand+5%cement)and to improve the brittle failure properties of aeolian sand modified soil,polypropylene fibers were divided into 0.1%,0.2%and 0.4%by mass percentage and perspectively incorporated into the aeolian sand modified soil.A consolidated undrained(CU)triaxial compression test was conducted.The test results show that the stress-strain curve of the aeolian sand modified soil has the characteristics of elastic-plastic deformation.The initial phase is pore compression with a sudden stress increase followed by a complete elastic phase,a phase of plastic deformation,and a phase of failure after the contact phase.The incorporation of propylene fibers increases the plastic deformation of the soil sample and improves the residual strength.The fracture surface becomes arc-shaped due to the pulling and tugging of the fibers,which prevents the brittle failure of the soil sample and increases its ductility.The cohesion of aeolian sand modified soil increases with the increase of fiber content,which basically shows a linear positive correlation,and the internal friction angle decreases with the increase of polypropylene fiber content and shows an overall linear negative correlation.The peak strain increases with the increase of polypropylene fiber content,and the stress-strain curve changes from strain softening type to strain hardening type,which can be effectively fitted by a hyperbola.The parameter\%b\%of stress-strain hyperbolic fitting model under the same confining pressure decreases with the increase of polypropylene fiber content.The research results can provide an experimental reference for the practical engineering application of aeolian sand modified soil.