不同材料组合及配比下类岩石试件单轴压缩损伤破坏过程分析

Analysis of damage and failure process of rock-like specimens under uniaxial compression with different material combinations and ratios

井下大尺寸真实岩芯难以获取且数量有限,通常采用类比法在室内制作类岩石材料试件模拟实际煤岩,以此开展水压致裂试验。为精确研究类岩石材料试件的力学特性,以水泥、石英砂、石膏和煤粉为原材料浇筑不同组合及配比的类岩石材料试件,通过单轴压缩试验,探究水膏比、砂胶比以及煤粉对试件力学特性及破坏形态的影响。结果表明:水泥-石英砂-石膏试件的抗压强度随水膏比的增加而增大,随砂胶比的增加而减小;砂胶比对试件抗压强度的影响更为显著,砂胶比与水膏比分别为0.33,0.75,1和0.5,1,2时,试件抗压强度由23.19 MPa降至19.14MPa;同种类岩石材料试件随水膏比增加峰值破坏时间提前,试件内部损伤程度加剧,水膏比由0.5增大至2,声发射累计振铃计数增大约5.1倍,宏观上表现为裂缝增多;相对石英砂、石膏而言,煤粉会加剧试件裂隙发育程度进而弱化其力学性质,保证配比不变,用煤粉分别代替水泥-石英砂-石膏试件中的石英砂、石膏,试件在峰值破坏时的最大声发射振铃计数分别为替换前的1.5和2倍,表面由较规整的裂缝变为更加发育贯通的裂缝;试件破坏后裂缝在其表面两侧呈反拱形分布,为X状共轭斜面剪切破坏,最大主应变较大值位于试件裂缝处,试件表面产生裂缝情况与声发射监测数据描述现象基本吻合。

Due to the difficulty of obtaining large size real cores in the well and the limited number,the analog method is usually used to make rock-like material specimens in the laboratory to simulate the actual coal rock,so as to carry out the hydraulic fracturing test.In order to accurately explore the mechanical properties of rock-like material specimens,cement,quartz sand,plaster,and coal powder were used as raw materials to cast specimens with different combinations and ratios.Through uniaxial compression test to explore the effects of cement-plaster ratio,sand-binder ratio and coal powder on the mechanical properties and destruction form of the specimens.The results show that the compressive strength of cement-quartz sand-plaster specimen increases with the increase of cement-plaster ratio,and decreases with the increase of sand-binder ratio;The sand-binder ratio has a more significant effect on the compressive strength of the specimen.When the sand-binder ratio and the cement-plaster ratio are 0.33,0.75,1 and 0.5,1,and 2,respectively,the specimen compressive strength decreases from 23.19 MPa to 19.14 MPa;The peak failure time of the same type of rock-like material specimens is advanced with the increase of the cement-plaster ratio,and the internal damage degree of the specimen intensifies.The cement-plaster ratio increases from 0.5 to 2,and the acoustic emission ringing count increases by about 5.1 times,macroscopically,it is manifested as increased cracks in the specimen,Compared with quartz sand and plaster,Coal powder will aggravate the development of cracks in the specimen and weaken its mechanical properties,so as to ensure that the ratio remains unchanged,and replacing quartz sand and plaster in cement-quartz sand-plaster specimens with coal powder,the maximum acoustic emission ringing count of the specimen at peak failure is 1.5 times and 2 times that before replacement,respectively,and the surface changes from more regular cracks to more developed through cracks;After the specimen is damaged,the cracks are distributed in reverse arches on both sides of the specimen surface,which is the X-shaped conjugate inclined plane shear failure,and the maximum principal strain is located at the crack of the specimen,which the cracks on the surface of the specimen are basically consistent with the phenomenon described by the acoustic emission monitoring data.