反倾角裂隙岩体压剪断裂及破碎特征研究

Investigation on compression-shear fracture and fragmentation characteristics of rock mass containing counter-inclined flaw

为了研究反倾角裂隙对边坡岩体压剪断裂及破碎特征的影响,制备反倾角裂隙模型试件并对其进行压剪试验;同时,建立断裂力学数值模型计算裂隙尖端应力强度因子。此外,对这些试件压剪试验后的碎屑进行筛分试验,引入分形理论定量描述压剪破碎特征及其与断裂特征的相关性。研究结果表明:(1)随着裂隙倾角数值的增大,试件抗剪强度总体呈先增大后减小的趋势;而裂隙尖端应力强度因子以及碎屑分形维数与裂隙倾角的变化规律正好相反。(2)试件压剪破坏模式可分为I型(沿裂隙剪切型)、II型(互锁型)、III型(穿切裂隙剪切型)3类;对于I型破坏模式,裂隙尖端应力强度因子最高,导致抗剪强度最低;对于II型破坏模式,裂隙尖端应力强度因子最低,导致抗剪强度最高;对于III型破坏模式,裂隙尖端应力强度因子较低,导致抗剪强度较高。(3)试件压剪试验后的碎屑尺度分布具有分形特征,分形维数位于2.06~2.59,在断层破碎带中也发现类似的结果;模型试件抗剪强度与对应的碎屑分形维数之间近似呈负线性相关关系,岩体压剪破碎特征与裂隙几何特征、应力状态以及断裂特征密切相关。

In order to study how the compression-shear fracture and fragmentation characteristics of rock mass of slope is influenced by counter-inclined flaw,model specimens containing counter-inclined flaw were prepared and compression-shear tests were conducted. The numerical model of fracture mechanics was established to calculate the stress intensity factor of flaw tip. Sieve tests were carried out for the fragments of these specimens after compression-shear tests. The fractal theory was introduced to quantify the compression-shear fragmentation characteristics and its correlation with fracture characteristics was investigated. With the increase of the absolute value of flaw inclination,the shear strength of specimens increases first and then decreases,which breaches the trends of the stress intensity factor of flaw tip and the fractal dimension of fragmentation. The failure generated in the specimen can be classified into three modes,namely mode I（sliding along the flaw）,mode II（interlocking） and mode III（cutting through the flaw）. The specimen failing in mode I,has a largest stress intensity factor of the flaw tip,resulting in a lowest stress strength. The specimen failing in mode II,has a lowest stress intensity factor of the flaw tip,resulting in a largest stress strength. The specimen failing in mode III,has an intermediate stress intensity factor of the flaw tip,resulting in a stress strength between those in modes I and II. The fragment size distribution of fragments under the compression-shear tests exhibits significant fractal property. The fractal dimensions of these fragmentations are in the range of 2.06 to 2.59,which is similar to those in the fault cores There exists negative correlation between the shear strength of specimen and the fractal dimension of fragmentation. The compression-shear fragmentation characteristics of rock mass are closely related to the flaw geometry,stress condition and fracture characteristics.