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为解决在软弱岩层中钻孔易塌孔、成孔难的工程问题,认为岩体黏聚力沿塑性区呈线性弱化,得出应变软化条件下钻孔围岩二次应力、位移和塑性区分布表达式。利用FLAC3D内嵌FISH语言,自定义岩体黏聚力,对钻孔围岩弹塑性分布进行数值模拟分析。研究表明,理想弹塑性模型下的塑性区半径公式为文中解黏聚力co=cs时的特解;考虑黏聚力弱化特性后,相同地应力条件下塑性区半径显著扩大,为修正Fenner解的1.4倍,钻孔围岩最大切向应力位于距钻孔中心约2.9倍钻孔半径处,应力集中系数小于2。成果应用于四川某矿井钻孔工程,表明当加固半径约为3倍钻孔半径时,成孔率在90%以上,取得较好技术经济效果。
In order to solve the engineering problems of easily collapsible borehole and difficult hole formation in soft rock formations, the cohesion of rock mass is linearly weakened along the plastic zone. The secondary stress, displacement and plastic zone of surrounding rock under strain softening condition are obtained Distribution expression. Using FLAC3D embedded FISH language, the cohesion of rock mass is defined and the elastic-plastic distribution of surrounding rock is numerically simulated. The results show that the formula of the plastic zone radius under the ideal elastic-plastic model is the special solution of cohesion co = cs. After considering the weakening property of cohesion, the radius of plastic zone expands significantly under the same stress condition. , The maximum tangential stress of the surrounding rock is about 2.9 times the hole radius at the center of the borehole, and the stress concentration factor is less than 2. The results are applied to the drilling project of a mine in Sichuan Province. It shows that when the radius of reinforcement is about 3 times of the drilling radius, the porosity of the formation is above 90%, which achieves better technical and economic results.