砂土剪胀剪缩特性及其对抗剪强度的影响

Shear Dilatancy and Shear Shrinkage Characteristic of Sand and Its Influence on Shear Strength

为了研究饱和砂土的剪胀剪缩特性及其对抗剪强度的影响,选取滹沱河细砂,利用空心圆柱扭剪仪较系统地开展了一系列不同初始密度、不同固结压力条件下的排水与不排水纯扭剪试验研究,在总应力保持不变的情况下研究了砂土的剪胀剪缩特性,着重探讨了在排水与不排水试验中,不同密度和不同有效围压的砂土在单调剪切荷载作用下的应力-应变关系、硬化与软化、土体的剪胀剪缩以及强度等特性。结果表明:砂土密度和固结压力对砂土剪胀剪缩特性具有显著的影响;砂土的剪胀剪缩特性对砂土的排水、不排水强度以及应力-应变关系产生显著的影响;由于剪胀剪缩特性的影响,砂土的不排水抗剪强度甚至可能高于排水抗剪强度;研究成果可为今后砂土的本构模型和数值模拟提供试验资料。

In order to study the shear dilatancy and shear shrinkage characteristic of saturated sand soil and its influence on shear strength, the Hutuo River fine sand was selected and the hollow cylindrical torsional shear apparatus was used to carry out a series of experimental research on the drainage and undrained pure torsional shear under different initial densities and different consolidation pressures. The shear dilatancy and shear shrinkage characteristics of sand soil were studied under the condition that the total stress remained unchanged. The stress-strain relationship, hardening and softening, shear dilatancy and shear shrinkage characteristics and strength of sand soil with different densities and different effective confining pressures under the action of monotonic shear load in the drainage and undrained tests were discussed. The results show that the effects of sand density and consolidation pressure on shear dilatancy and shear shrinkage characteristics of sand soil are significant. The shear dilatancy and shrinkage characteristics of sand soil have significant effects on the drainage, undrained strength and stress- strain relationship. Due to the influence of shear dilatancy and shear shrinkage characteristics, the undrained shear strength of sand soil may even be higher than that of drained shear strength. The research results can provide experimental data for future constitutive models and numericalsimulations.