深部裂隙煤岩体变形破坏机理及高压注浆改性强化试验研究

为了对深部高应力裂隙煤岩体变形破坏特征及改性强化机理进行研究,首先采用小孔径水压致裂法对埋深500 m左右和1000 m左右的地应力分布特征进行现场实测研究,以此为基础对比分析了不同埋深条件下地应力分布特征、煤岩体破裂强度及典型裂隙分布发育特征,拟合得到了不同埋深条件下裂隙煤岩体摩尔强度包络线公式。采用数值模拟方法对比研究了不同埋深不同应力水平条件下煤岩体不同角度裂隙变形破坏特征。根据裂隙扩展应变能释放率与能量吸收率间的关系,探讨了影响深部裂隙煤岩体改性强化的主要影响因素。通过建立裂隙悬臂梁力学模型,采用格里菲斯裂纹扩展破坏准则分析了裂隙扩展临界载荷和裂隙不同角度间的关系。基于现场实测及数值模拟研究结果,通过对不同埋深煤岩体破裂强度的统计分析,结合煤岩体改性强化的工艺及装备要求,提出了深部裂隙煤岩体改性强化的基本原则及临界值范围。基于上述研究成果,在千米深井工作面巷道进行了现场试验,得到了裂隙煤岩体改性强化高压注浆全过程改性压力曲线。通过对裂隙煤岩体不同改性强化阶段浆液扩散特征的分析,最大注浆改性强化压力为30 MPa,一般为15~20 MPa,与提出的改性原则相符。通过现场取样表征分析、实验室扫描电镜对尺度2~20μm浆液固结体特征进行对比分析,采用纳米压痕试验对浆液固结体和煤岩体的界面弹性模量效应进行了分析,从宏观到微观验证了裂隙煤岩体改性强化效果良好。

Deformation failure mechanism of fractured deep coal-rock mass and high-pressure grouting modification strengthening testing

In order to study the deformation failure characteristics of fractured deep coal-rock mass with high in-situ stress and its modification strengthening mechanism,firstly,the in-situ stress distribution characteristics of coal-rock mass with buried depth about 500 m and 1000 m were tested by means of small borehole hydraulic fracturing method in field.The in-situ stress characteristics in different buried depths,coal-rock mass rupture strength and its typical fracture features were studied by comparative analysis.The Mohr envelopes formula of fractured coal-rock mass with different buried depths were put forward.The deformation characteristics of coal-rock mass fractures with different angles and different stress levels in different buried depths were studied through numerical simulation,and the main influence factors for coal-rock modification strengthening with deep buried depth were discussed based on the relationship between the strain energy release rate of fracture development and specific absorption rate.The cantilever beam mechanical model was built,and then the relationship between fracture propagation critical load and different fracture angles was analyzed through Griffith fracture failure criterion.With field testing and numerical simulation results,based on the rupture strength statistic analysis of coal-rock mass with different buried depths and technology and equipment required,the modification strengthening principles of fractured deep coal-rock mass and its relevant modification pressure critical range were put forward.Based on the above-mentioned achievements,the underground testing was conducted in working face roadway of 1000 m deep coal mine,and the fully process modification and strengthening grouting pressure curve was derived.The grouting diffusion in different modification and strengthening phases of fractured coal-rock mass were analyzed,the maximal grouting pressure was no less than 30 MPa,and its normal scope was 15 MPa to 20 MPa.All of the results were accord with the criteria that put forward above.The grouting stone features from sizes 2 to 20μm were verified by field sampling and laboratory SEM testing,the elastic modulus effect of interface between coal-rock mass and grouting stone was analyzed by means Nano indentation test,the modification strengthen was verified as good from macros to micro size.