黄土天然节理大型直剪试验研究

Large-scale direct shear test study on natural loess joint

黄土节理的抗剪强度及变形规律对工程稳定性有重要影响,但目前对此的研究尚不充分.为此本次研究首先采集了黄土天然垂直节理土样,然后采用室内大型直剪试验方法,研究了黄土天然节理的剪切强度及变形性质,最后与小型直剪试验结果进行对比,得到了尺寸效应对黄土节理剪切强度的影响规律.结果发现,大型直剪试验得到黄土节理剪切峰值内摩擦角为47.37°,小型直剪试验值为35.17°;黄土节理直剪试验存在尺寸效应,试样尺寸主要影响节理面起伏度对剪切强度的贡献,尺寸越大,其剪切强度也越大;法向应力较小时,初始剪切刚度较大,应力-应变曲线存在峰值;法向应力较大时,初始剪切刚度较小,应力-应变曲线无峰值,剪切强度随应变增大而增大,最终趋于稳定.

Shear strength and deformation law of loess joint has important influence on the engineering stability,but the research of this area is still inadequate.Therefore this study first collected loess vertical joints and natural soil samples,and then used the lab large-scale direct shear test method,in studiing the natural joint shear strength and deformation properties of loess.Finally compared with small direct shear test results,the size effect of joint shear strength of loess are studied.Research has shown that large direct shear test to get the angle of internal friction peak is 47.37 DHS,small direct shear test to get the angle of internal friction peak of 35.17 DHS;As the normal stress is small,initial shear stiffness is bigger,and the stress-strain curve peak;As the ormal stress is larger,the initial shear stiffness is small,no peak stress-strain curve occurs,and the shear strength increases with strain,while ultimately tend to be stable.Loess joint size effect,and direct shear test mainly affects the sample size′s contribution to the shear strength of joint surface fluctuation degree.The greater the size,the greater the shear strength.