煤岩水压裂缝扩展行为特性研究

RESEARCH ON BEHAVIOR CHARACTER OF CRACK DEVELOPMENT INDUCED BY HYDRAULIC FRACTURING IN COAL-ROCKMASS

对坚硬煤体预裂中存在的问题,采用地应力场控制下水压致裂的方法,通过来自铜川矿区的九块大型煤块试件,研究了水压裂缝扩展行为的控制参数。在此基础上对水压裂缝的形成、扩展与煤体渗透性改变、水压作用的关系,进行了系统试验研究。克服了常规小试件试验的局限性,建立了起始渗透压力和最大破坏压力与煤样裂缝扩展变化过程的对应关系,研究了水压裂缝破坏煤体结构的力学机制,为解决煤岩体介质材料中水压裂缝扩展行为控制提供了科学依据。试验表明,本文结果中水压裂缝扩展控制参数对改善顶煤预裂设计效果具有实际意义。

Aiming at the problem existing in hard coal mass with prefracturing,using the method of hydraulic fracturing controlled by strata stress field,the control parameters of crack development induced by hydraulic fracturing are studied by nine large coal samples with hardness f = 3.0～3.5,which came from the Tongchuan mining area. Systematic experiments were carried out for researching the relation among formation and extension of the hydraulic crack,change of coal mass permeability,and hydraulic pressure effect. The limitation of conventional test with small samples was overcome,and the correspondence was built between original osmotic pressure and maximum destruction pressure during crack extension of coal sample. The mechanical mechanism of destructing coal mass structure by hydraulic crack is studied,and the scientific basis is provided for behavior control of crack development induced by hydraulic fracturing in coal-rock medium. The experiments indicate that the control parameters of crack development induced by hydraulic fracturing have practical meaning for improving the effect of prefracturing design for hard top coal.