粗粒土三轴试样端部约束影响研究

Effects of end restraint in triaxial tests on coarse-grained soil

对两种级配的砾石料,分别进行了两种中三轴固结排水剪试验,一种是试样端部采用润滑试样帽法以减轻端部约束对三轴试验的影响;另一种试样则是常规三轴固结排水剪试验,即不采取端部减摩措施。对比分析两种试验的结果,以研究端部约束对三轴试样变形及强度的影响,分析润滑试样帽法对粗粒土试样的端部减摩效果。结果表明:试样在剪切过程中均表现出不同程度的剪胀性,常规三轴试样体积变形比减轻端部约束试样体积变形略小;当试验围压较低时,减轻端部约束对试样偏应力峰值(σ_1-σ_3)_f影响相对显著,而高围压下,润滑试样帽法的减摩作用几乎消失;同样,内摩擦角φ,初始切线模量E_i,割线弹性模量E_1均比常规三轴试验的小;随着围压的不断增大,润滑试样帽法减轻端部约束的效果明显减弱。

The end restraint can be eliminated by lubrication sample cap to some extent in the conventional triaxial tests. A comparison is made between the conventional triaxial tests and the end friction reduced triaxial tests in order to study the effects of the end restraint on the test results. The results show that different degrees of dilatancy is shown during the tests. The degree of volume deformation of the conventional triaxial test specimen is smaller. The measures to reduce the end friction have marked effects on the peak strength(σ_1-σ_3)_f under low confining pressure. But with the increase of the confining pressure the effects of the lubrication sample cap method to reduce the end friction become worse. Under the same confining pressure, the internal friction angle φ, the initial Young's modulus Ei and the secant modulus E_1 of the end friction reduced triaxial tests are smaller than those of the conventional triaxial tests.