True Triaxial Strength and Failure Modes of Cubic Rock Specimens with Unloading the Minor Principal Stress
True Triaxial Strength and Failure Modes of Cubic Rock Specimens with Unloading the Minor Principal Stress
复制标题
卸载小主应力的立方体岩石试件的真三轴强度和破坏模式
DOI：
10.1007/s00603-014-0701-y
复制
发表时间：
2015-11-01
影响因子：
6.2
通讯作者：
Li, Diyuan
中科院分区：
文献类型：
--
作者：
Li, Xibing;Du, Kun;Li, Diyuan
本文对花岗岩、砂岩和水泥砂浆进行了卸载小主应力的立方体试件真三轴试验。利用新研制的真三轴试验系统，研究了3种岩石材料在卸σ 3和加σ 1过程中，在不同σ2下的强度和破坏模式，旨在研究岩石在深基坑开挖中的力学响应。结果表明，当σ 3卸荷为零时，岩石强度随中间主应力σ 2的增大而增大。利用幂律关系建立的真三轴强度准则可以较好地拟合试验数据。“最佳拟合”材料参数A和n（A> 1.4和n < 1.0）几乎位于与Al-Ajmi和齐默尔曼（Int J Rock Mech Min Sci 563 42（3）：431-439，2005）预期的相同范围内。结果表明，立方体试件高宽比引起的端部效应对真三轴试验结果影响不大。真三轴卸载条件下立方体岩石试件的强度和破坏模式均受中间主应力的影响。当σ 2增加到一个临界值时，对于坚硬的岩石（R4、R5和R6），岩石的破坏模式可能由剪切型转变为板状。然而，对于中等强度和中等强度的岩石（R3和R2），即使具有相对较高的中间主应力，它们也倾向于在大量塑性变形后发生剪切破坏。Stacey（Int J Rock Mech Min Sci Geomech Abstr 651 18（6）：469-474，1981）的最大延伸应变准则可以用来解释在真三轴卸荷试验条件下坚硬岩石的破坏模式从剪切到板裂的变化。
True triaxial tests have been carried out on granite, sandstone and cement mortar using cubic specimens with the process of unloading the minor principal stress. The strengths and failure modes of the three rock materials are studied in the processes of unloadingσ3and loadingσ1by the newly developed true triaxial test system under differentσ2, aiming to study the mechanical responses of the rock in underground excavation at depth. It shows that the rock strength increases with the raising of the intermediate principal stressσ2whenσ3is unloaded to zero. The true triaxial strength criterion by the power-law relationship can be used to fit the testing data. The “best-fitting” material parametersAandn(A> 1.4 andn< 1.0) are almost located in the same range as expected by Al-Ajmi and Zimmerman (Int J Rock Mech Min Sci 563 42(3):431–439, 2005). It indicates that the end effect caused by the height-to-width ratio of the cubic specimens will not significantly affect the testing results under true triaxial tests. Both the strength and failure modes of cubic rock specimens under true triaxial unloading condition are affected by the intermediate principal stress. Whenσ2increases to a critical value for the strong and hard rocks (R4, R5 and R6), the rock failure mode may change from shear to slabbing. However, for medium strong and weak rocks (R3 and R2), even with a relatively high intermediate principal stress, they tend to fail in shear after a large amount of plastic deformation. The maximum extension strain criterion Stacey (Int J Rock Mech Min Sci Geomech Abstr 651 18(6):469–474, 1981) can be used to explain the change of failure mode from shear to slabbing for strong and hard rocks under true triaxial unloading test condition.