自由边界影响下定向断裂爆破裂纹尖端应力分布与扩展机理  

Stress Distribution and Propagation Mechanism of Crack Tip in Directional Fracturing Blasting under the Influence of Free Boundary

作　　者：邱鹏 岳中文[2] QIU Peng;YUE Zhongwen(Key Laboratory of In-Situ Property-Improving Mining of Ministry of Education,Taiyuan University of Technology,Taiyuan 030024,Shanxi,China;School of Mechanics and Civil Engineering,China University of Mining and Technology(Beijing),Beijing 100083,China)

机构地区：[1]太原理工大学原位改性采矿教育部重点实验室,山西太原030024 [2]中国矿业大学(北京)力学与土木工程学院,北京100083

出　　处：《高压物理学报》2024年第5期149-159,共11页Chinese Journal of High Pressure Physics

基　　金：国家自然科学基金(52204106,52174094);国家重点研发计划(2021YFC2902103);山西省基础研究面上项目(202203021211133)。

摘　　要：天然岩体常含自由边界,对定向断裂爆破产生干扰。为探究自由边界对定向断裂爆破的影响,采用爆炸焦散线方法和高速摄影技术,研究了含自由边界时定向爆炸裂纹尖端的应力分布和扩展机理。自由边界的反射P/S波作用于定向爆炸裂纹,改变了裂尖应力分布,产生了“弧线形”裂纹扩展路径。定向爆炸裂纹扩展可分为3个阶段。(1)反射波作用前:裂尖受爆生气体“气楔”作用,产生Ⅰ型断裂,并沿直线扩展。(2)反射波作用时:反射P/S波均使裂尖受张拉-剪切作用,产生Ⅰ-Ⅱ复合型断裂,裂纹偏转趋向自由边界;在反射P波的作用下裂尖产生畸变焦散斑,裂尖应力由K场主导变为非K场主导,而在反射S波的作用下裂尖应力恢复为K场主导。(3)反射波作用后:裂尖在惯性作用下恢复为Ⅰ型断裂,沿直线扩展。在明确反射P/S波对定向爆炸裂纹作用的基础上,推导了自由边界影响下定向断裂爆破炮孔间距的计算公式,可为精细化定向断裂爆破提供理论参考。Natural rock masses often contain free boundaries,which can interfere with directional fracturing blasting.To investigate effects of free boundary on directional fracturing blasting,the caustics method and high-speed photography were used to study the crack-tip stress distribution and propagation of directional blast-induced cracks.The reflected P/S waves from the free boundary act on a directional blast-induced crack,and change the crack-tip stress distribution and generate an“arc shaped”crack path.Directional blastinduced crack propagation can be divided into three stages.Stage one:before the action of reflected waves,the crack tip is subjected to the action of a blast-induced gas wedge,resulting in a modeⅠcrack that propagates along a straight line.Stage two:under the action of reflected waves,both reflected P and S waves cause the crack tip to be subjected to tension and shear action,resulting in a mixed modeⅠ-Ⅱcrack which deflects towards the free boundary.Under reflected P waves,the crack tip produces distorted caustics,and crack-tip stress changes from K-dominated field to non-K-dominated field,while under reflected S waves,crack-tip stress returns to K-dominated field.Stage three:after the action of reflected waves,the crack tip is subjected to inertial action and then returns to a modeⅠcrack which propagates along a straight line.On the basis of clarifying effects of reflected P/S waves on the tip of directional blast-induced cracks,a calculation formula for the distance between two directional fracturing blasting holes under the influence of free boundary is derived,providing a theoretical basis for refined directional fracturing blasting.

关 键 词：自由边界 定向断裂爆破 反射P/S波 裂尖应力分布 裂纹扩展 

分 类 号：O389[理学—流体力学] O521.9[理学—力学]