含齿形裂隙类岩石材料单轴压缩试验研究

为研究含齿形裂隙岩石在单轴压缩下的破坏特征及强度特性，制作了含不同裂隙倾角和起伏角的齿形裂隙类岩石材料试件，并采用岩石力学伺服试验机进行单轴压缩试验。试验结果表明：（1）试件主要产生拉伸、剪切和拉剪复合裂纹，且根据裂纹的扩展路径可划分为A型（拉伸破坏）、B型（剪切破坏）、C型（复合破坏）3种破坏模式，裂隙倾角对试件最终破坏模式影响显著；（2）当裂隙倾角较小时，试件应力—应变曲线为多峰曲线，随着裂隙倾角的增大，曲线呈单峰形式，表现为延性减弱，脆性增强，而裂隙倾角相同但起伏角不同的试件应力—应变曲线大致相同；（3）当裂隙起伏角相同时，试件当量峰值强度随裂隙倾角的增大呈先减小后增大的规律，且裂隙起伏角对试件当量峰值强度的影响小于裂隙倾角。

Experimental Study of Rock-like Material with Zigzag Fracture Under Uniaxial Compression

As a complex natural medium，rock has formed cracks with different geometrical sizes and spatial combination characteristics in its interior after a long process of geological tectonics，which seriously affects the physical and mechanical properties of rock.Therefore，the study on crack initiation，propagation and penetration of rock materials and rock-like materials with cracks is of great significance for practical engineering.In order to investigate the strength and failure characteristics of the rock with zigzag fissure under uniaxial compression,the rock-like specimens are made by mixing C42.5 portland cement，fine sand，and water at a mass volume ratio of 2∶2∶1.The uniaxial compressive strength of this material is between 30~60 MPa，belonging to the sub-hard rock，which can represent the fracture behavior of most rocks in nature.The zigzag fissures are created by inserting aluminum shims into cement mortar paste and removing them during curing.Finally，the tooth-shaped specimens with different crack dip angle （β） and fluctuation angle （α） were obtained.The uniaxial compression test were conducted through rock mechanical servo test machine and loading process，crack initiation were observed and recorded by the camera.The test results show that：（1） There are three types of cracks observed,which are tensile cracks，shear cracks and tensile-shear cracks，and the failure modes of the specimen can be classified into three categories,that is A （tensile failure），B （shear failure），and C （compound failure）. For β∈（0°，30°），tensile wing crack is initiated from the tips of fissure which lead the flawed specimens to fail,naming A mode. For β∈（45°，60°），shear crack is observed in all flawed specimens,naming B mode.Tensile-shear compound failure (B mode)is observed in the specimens with β=75° and 90°. The inclination angle strongly affects failure modes，while the undulating angle seem to play only a minor role with respect to failure characteristics of specimen. （2）When the dip angle is small，the stress-strain curve of the specimen is multi-peak curve.With increasing of inclination angle，the stress-strain curve gradually transform to single-peak shape，and the post peak curve shows ductility weakening and brittleness enhancement.The residual strength curve of the specimens indicate that particle friction play a major role for residual strength under uniaxial compression.However，for the specimen with same inclination angle，the stress-strain curves for different undulating angles are roughly the same.（3）The lowest equivalent peak strength of the specimens is normally observed when β=30°. When the undulating angle is the same，the equivalent peak strength of specimens decreases as inclination angle increases from 0° to 30°，and increases for inclination angle α>30°, while the influence of the fracture undulation angle on the equivalent peak strength of specimens is smaller than the dip angle of fracture.