深部地下硐室与应力场轴变关系及其围岩损伤破裂分析

Mechanism analysis of rock damage and failure based on the relation between deep chamber axial variation and in situ stress fields

针对深部地下硐室与地应力场之间的轴变关系及其对硐室围岩损伤破裂的影响,建立了非均质围岩统计损伤力学模型;分析了不同断面形状、地层侧压系数、构造应力场对硐室围岩损伤破裂的作用机制和影响规律,定义了地层临界侧压系数;开展了三山岛金矿西岭矿区埋深2000 m地层硐室损伤破裂数值模拟,得到了该矿区深部地下硐室设计与布置原则.研究结果表明,“等应力轴比”情况下硐室围岩应力集中程度最小,损伤破裂区面积最小;地应力场是围岩损伤破裂的根本原因,侧压系数越大,硐室顶、底板处应力峰值越大,围岩以拉伸破裂为主,围岩损伤破裂区面积随侧压系数增大呈指数性增大;随着地层深度的增加,硐室临界侧压系数不断减小并趋近于1,深部地下硐室对水平构造应力更加敏感;构造应力场诱使围岩损伤破裂程度增大,损伤破裂区向构造应力场围岩应力集中区转移,使得硐室围岩发生冒顶和岩爆风险升高.因此,深部地下硐室的设计与布置应结合实际地应力条件,硐室轴向、断面形状、轴比尽可能符合地应力条件,从而最大程度降低地应力场对硐室围岩损伤破裂及稳定性的不利影响.

The demands for deep underground mining and construction are increasing with the continuing development of society and the economy.Deep underground chambers function as primary elements in deep underground mining and other subsurface facilities.Therefore,rational designs of such chambers would play a pivotal role in construction safety and economic efficiency.The primary goal of this study is to reveal the relation between the in situ stress field and axes of an elliptical cross section of an underground chamber.Based on the rock deformation and damage,a numerical model is developed to define the heterogeneous damage evolution near the chamber.In this parametric study,we characterized the damage evolution in response to the chamber’s cross-sectional shape,lateral stress coefficient,and tectonic stress azimuth,thus introducing the critical lateral stress coefficient to define the chamber stability.Furthermore,a case study of a−2000 m chamber in the Sanshandao gold mine was conducted using the proposed model to optimize the shape,design,and location analysis of the underground mining chamber.Simulation outcomes show that the damaged area and stress concentration near the chamber are minimized when the axis ratio is equal to the lateral stress coefficient.The damaged area is determined by the in situ stress configuration;a high lateral stress coefficient sees a pronounced increment in the tension stress inside the roof and floor of the chamber,resulting in an exponential enlargement of the damaged area.Compared with the shallow underground chamber,the deep chamber is more sensitive to an increase in the lateral stress coefficient.With an increase in depth,the critical lateral stress coefficient gradually decreased to 1.The larger horizontal tectonic stress in the deep strata causes damage accumulation in the roof and the floor,encouraging rock outbursts in the damaged zones.To conclude,to optimize the design and minimize the outburst hazard for a deep underground chamber,the chamber’s cross-sectional shape,axes ratio,and direction must reasonably reflect the in situ stress field.