不同排水方式的湿陷性黄土力学特性试验及邓肯-张模型的改进

Mechanical property test of collapsible loess with different drainage methods and improvement of Duncan-Chang model

为分析渠坡变形破坏机理,针对新疆某输水明渠工程的湿陷性黄土进行了固结排水和固结不排水三轴剪切试验,并通过改进的邓肯-张模型对三轴剪切试验曲线进行了模拟,同时与邓肯-张模型和驼峰型三次曲线模型进行了对比分析。研究结果表明:随着围压增大,固结排水试验的应力-应变曲线和体变曲线均由软化型转变为硬化型;固结不排水试验应力-应变曲线均为硬化型,孔压曲线均表现为软化型;固结排水试验得到的有效黏聚力大于固结不排水试验得到的黏聚力,固结排水试验得到的有效内摩擦角与固结不排水试验得到的内摩擦角相差较小;改进后的邓肯-张模型参数共有9个;邓肯-张模型不能合理描述软化型三轴试验曲线,驼峰型三次曲线模型对强软化型三轴试验曲线契合度较差,而改进的邓肯-张模型能够较好地描述各种形态的湿陷性黄土三轴试验曲线,有较好的准确性。

In order to analyze the deformation and failure mechanism of canal slopes,the consolidated drained and consolidated undrained triaxial shear tests were carried out on the collapsible loess of an open-channel water transfer project in Xinjiang.The triaxial test shear curve was simulated by the improved Duncan-Chang model and compared with those obtained from the Duncan-Chang model and the hump-type cubic curve model.The results show that with the increase of confining pressure,the stress-strain curve and volume change curve of consolidated drained test change from softening type to hardening type.The stress-strain curves of consolidated undrained test are all hardening type,and the pore pressure curves are all softening type.The effective cohesion obtained by the consolidated drained test is greater than that obtained by the consolidated undrained test,and the effective internal friction angle obtained by the consolidated drained test is slightly different from that obtained by the consolidated undrained test.There are nine parameters in the improved Duncan-Chang model.The Duncan-Chang model cannot reasonably describe the softening triaxial test curve,and the hump-type cubic curve model has a poor fit to the strong softening triaxial test curve,while the improved Duncan-Chang model can better describe various types of triaxial test curves of collapsible loess and has good accuracy.