多形态裂隙砂岩水力耦合破坏过程与增透机理试验研究  

Experimental investigation on hydromechanical coupling-induced failure and permeability evolution for sandstone with multiple-shape prefabricated fractures

作　　者：张英[1,2] 郭奇峰 席迅[1,2] 蔡美峰 伦嘉云[3] 潘继良 ZHANG Ying;GUO Qi-feng;XI Xun;CAI Mei-feng;LUN Jia-yun;PAN Ji-liang(School of Civil and Resource Engineering,University of Science and Technology Beijing,Beijing 100083,China;Key Laboratory of High Efficient Mining and Safety of Metal Mines(Ministry of Education),University of Science and Technology Beijing,Beijing 100083,China;Information Institute of the Ministry of Emergency Management of the PRC,Beijing 100029,China)

机构地区：[1]北京科技大学土木与资源工程学院,北京100083 [2]北京科技大学金属矿山高效开采与安全教育部重点实验室,北京100083 [3]应急管理部信息研究院,北京100029

出　　处：《工程科学学报》2022年第10期1778-1788,共11页Chinese Journal of Engineering

基　　金：国家重点研发计划资助项目(2021YFC3001301)。

摘　　要：水力耦合激活岩石天然裂隙,诱导裂隙扩展形成复杂裂隙网络,增加岩石渗透性是矿产地热共采体系中的关键技术.本文通过预制含单裂隙、T型裂隙和Y型裂隙的砂岩试样,进行三轴水力耦合试验,研究多形态裂隙砂岩的关键阈值(闭合应力、起裂应力、损伤应力、峰值强度)、弹性模量、泊松比以及破坏模式等力学特性,同时开展裂隙渐进演化过程中声发射和渗透率的演化规律研究,进一步分析水力耦合作用下裂隙岩石增透机理.结果表明:多形态预制裂隙砂岩试样在水力耦合作用下,既有裂隙均通过拉伸、剪切或混合模式扩展形成次生裂纹,构成裂隙网络,试样渗透率显著增加.单裂隙试样的次生裂隙以剪切破坏为主,T型和Y型裂隙试样的次生裂隙为剪切破坏和张拉-剪切破坏两类.此外,多形态裂隙对试样强度的影响大于水的弱化作用.随着轴压增大,岩石渗透率峰前阶段先减小后增大,达到强度破坏时突跳增大.当试样达到峰值后应力突然下降时,渗透率达到最大值,渗透率增透效果最好.预制裂隙角度和形态的变化对突跳系数的影响幅度较小,单裂隙的平均突跳系数值大于Y型裂隙大于T型裂隙.研究结果有助于理解裂隙破坏和流体流动行为,进而指导矿产地热共采的工程.In mineral and geothermal resource co-mining,the underground rock is often affected by mining stress,and fractures of different shapes,such as single fractures,T-shaped fractures,and Y-shaped fractures,are generated.To increase the reservoir permeability,the existing fractures need to be reactivated,causing them to expand under force and propagate in shear and tension modes,generating new fractures and finally forming a fracture network to increase permeability.Waterjet cutting and wire cutting equipment are used to prefabricate sandstone samples with different inclinations and single,T-shaped,and Y-shaped fractures on standard samples.This paper conducts hydromechanical coupling experiments to investigate the possibility of increasing permeability by expanding and merging fractures in prefabricated fractured sandstone samples under triaxial conditions.In addition,the focus is on mechanical properties,such as critical thresholds(crack closure stress,crack initiation stress,damage stress,and peak strength),elastic moduli,and Poisson's ratio,and the failure modes of multiple-shape prefabricated fracture sandstone samples are mainly studied.Simultaneously,the evolution law of acoustic emission and permeability during the progressive failure of fractured rock is studied,and the mechanism of permeability enhancement of fractured rocks under the action of hydraulic coupling is analyzed.The results show that under the action of hydromechanical coupling,all multi-shape prefabricated fracture specimens form secondary cracks that expand in tensile,shearing,or mixed modes through the existing fractures and generate new fractures or fracture networks,which can effectively increase the flow rate.All single-fracture specimens are shear failures,and the T-shaped and Y-shaped fracture specimens have two types of shear failure and tension-shear failure.Furthermore,the weakening effect of water has a smaller effect on strength than the effect of multiple-shape prefabricated fractures.With increasing axial pressure,the rock permeab

关 键 词：水力耦合 裂隙扩展 混合型裂隙 突跳系数 渗透率增加 

分 类 号：TG142.71[一般工业技术—材料科学与工程]