三维应力状态下粗粒料强度特性试验研究

Experimental investigation on strength characteristic of coarse-grained materials in three-dimensional stress state

粗粒料所处的应力状态具有随时间和空间而变的特点,往往处于较复杂的三维应力状态下。通过粗粒料大型真三轴各向等压固结等比例加载试验,研究了不同中主应力系数条件下粗粒料的强度特性。试验结果表明:中主应力对粗粒料的强度有重要影响,三维应力状态下,粗粒料的强度比常规三轴应力状态下有较大提高,大小主应力之差与大主应变关系曲线也更加陡峭;中主应力系数b从0增大到0.25时,破坏时大小主应力之差增加了39%~50%;摩尔–库仑强度参数咬合力c和内摩擦角?均随着中主应力系数b的增大而增大,其中咬合力c的增长较为显著,特别是b从0增大到0.25时;相同小主应力条件下,b=0时,破坏偏应力与球应力之比最小,b=0.25时,破坏应力比达到最大值,随着b的增大破坏应力比又有所减小;相同中主应力系数条件下,随着小主应力的增大,破坏应力比逐渐减小。

The coarse-grained materials are normally in three-dimensional（3D） stress state which changes with time and location. To investigate the strength characteristic of coarse-grained materials at different coefficients of intermediate principal stress, large-scale true triaxial tests were performed under isotropic consolidation and proportional loading conditions. The results show that the intermediate principal stress has an important effect on the strength of coarse-grained materials. The strength of coarse-grained materials in 3D stress state increases greatly compared to the strength in conventional triaxial stress state. The relationship of the major principal strain and the difference between the maximum and the minimum principal stresses in 3D stress state is steeper than that in conventional triaxial stress state. The difference between the maximum and the minimum principal stresses increases from 39% to 50% when the coefficient of intermediate principal stress increases from 0 to 0.25. Both the interlocking force c and internal friction angle j increase with the increase of the coefficient of intermediate principal stress b. Especially, the interlocking force c increases significantly when b increases from 0 to 0.25. With the same minimum principal stress, the ratio of deviatoric stress to spheric stress at the failure state is the smallest with b=0, whereas the failure stress ratio reaches the maximum with b=0.25. However, the failure stress ratio decreases with the increase of b from 0.25 to 0.75. The stress ratio at failure state decreases with the increase of the minimum principal stress at the same coefficient of intermediate principal stress.