基于真三轴单面卸荷强度双折减法修正D-P准则研究

Modified D-P criterion based on the double-fold reduction method of the true triaxial single-side unloading strength

为了准确地评价巷(隧)道开挖面附近围岩的稳定性,采用真三轴卸荷扰动岩石测试系统对大理岩进行不同主应力加卸载试验,研究大理岩强度参数的演化特征。基于Mohr-Coulomb(M-C)准则与Drucker-Prager(D-P)系列准则匹配关系推导分析,探讨黏聚力c、内摩擦角?和Lode参数值的变化规律,确定最大衰减路径,得出黏聚力c和内摩擦角?的强度双折减系数。研究结果表明:(1)M-C准则和D-P准则计算破坏强度的条件是主应力为对称加卸载,在最小主应力单面卸荷的条件下,其准则计算的破坏强度值偏高;(2)M-C准则通过强度双折减后计算的破坏强度值偏低;(3)基于M-C准则强度双折减法对D-P准则进行修正,计算的破坏强度值更接近实际情况。研究结果对于控制地下工程灾害、保障施工安全具有重要的指导意义。

To evaluate the safety of rock around the excavation front of roadway in mine or mountain ridge, tests on griotte under different loadings and unloadings of principal stress were conducted using true triaxial system. The variation of cohesion c,internal friction angle φ,and Lode parameter of griotte were discussed in detail according to the Mohr-Coulomb and Drucker-Prager criterions. The maximum attenuation path was obtained and the double attenuation coefficient of the cohesion c and internal friction angle φ was calculated. The results indicate that the condition for calculating the fracture strength based on M-C and D-P criterion is that the principal stress is loaded symmetrically. Under the condition of single sided unloading in the direction of minimum principal stress,the fracture strength calculated with the criterion is higher. The fracture strength value calculated with the double attenuation coefficient method based on M-C criterion is lower. The calculated fracture strength value using the D-P criterion that is modified by the strength reduction method based on the M-C criterion is closer to the actual situation.