液氮磨料射流破碎高温花岗岩机理

Breakage mechanism of high-temperature granite by abrasive liquid nitrogen jet

液氮磨料射流是一种高效的破碎干热岩方式。为进一步探究其破岩机理,开展液氮磨料射流喷射高温花岗岩室内实验。从宏观角度分析岩石破碎形式、射流孔眼形态及表面特征,从微观角度分析断裂面形貌和微裂缝分布等,探究液氮磨料射流破碎高温岩石特征。同时,开展磨料水射流和氮气磨料射流破岩实验作为对照。实验结果表明,液氮磨料射流形成的孔眼形状不规则,表面凹凸不平,且破碎体积明显大于磨料水射流和氮气磨料射流。扫描电镜实验显示,低温、冲击载荷作用下,在孔眼壁面和孔眼附近区域生成大量微裂缝,其主要断裂方式为拉伸、剪切作用下岩石的脆性断裂,表现为穿晶断裂和沿晶断裂。理论分析和数值模拟研究表明,液氮低温作用对岩石造成损伤,而热应力、磨料冲击载荷和流体水楔作用在损伤岩石基础上主要以剪切和拉伸两种方式破碎岩石。

Abrasive liquid nitrogen jet is an efficient method for breaking hot dry rock. In order to further explore its rock-breaking mechanism, this study carries out the laboratory experiments of abrasive liquid nitrogen jet spraying on high-temperature granite. The characteristics of high-temperature granite crushed by abrasive liquid nitrogen jet are explored by analyzing the forms of rock fragmentation, the shapes and surface characteristics of jet perforation cavity from a macro perspective, as well as the morphology of the fracture surface and micro-crack distribution from a micro perspective. Meanwhile, rock breaking experiments with abrasive water jet and abrasive nitrogen jet are carried out as control. The experimental results show that the perforation cavities formed by abrasive liquid nitrogen jet are irregular in shape, and its surface is uneven.The crushing volume is significantly larger than that formed by abrasive water jet and abrasive nitrogen jet. SEM experiments show that a large number of micro-cracks are generated in the wall surface of the perforation cavity and the nearby area under low-temperature action and impact loads. The fracturing mode of rocks is dominated by brittle fracture under tensile and shear action, shown as transgranular and intergranular fractures. The theoretical analysis and numerical simulation researches show that the low-temperature action of liquid nitrogen causes damage to rocks, while the rocks are further damaged by thermal stress, abrasive impact load, and the effect of fluid water wedge.