地应力对脆性岩体洞群稳定性的影响

Influence of in-situ stress on stability of underground openings in hard rock

利用岩体脆性破坏准则和Examine2D软件,分析不同地应力及洞形、洞群下围岩破坏深度af变化规律。基于中国大陆地应力分布规律,分析三大岩类代表性岩石性质随洞室埋深af变化规律并与实际工程进行对比。研究结果表明:af与主应力比k近似呈直线关系,随着k增加,屈服范围逐渐偏离最小主应力向45°夹角发展;单洞室破坏范围呈轴对称形式,多洞室破坏范围呈点对称方式;当主应力方向与洞轴连线呈45°时,屈服范围最易于合并;洞群效应随洞间距增加逐渐降低;洞形不同应力集中系数不同,选择长短轴长度之比与应力比k相接近的椭圆形谐洞,可有效降低破坏深度;af与岩石单轴抗压强度σc呈指数函数关系,当σc大于(9σ10-3σ30)(其中,σ10和σ30分别为最大、最小初始地应力)时,不会发生脆性破坏;af变化规律与实际结果具有较好的一致性;采用脆性岩体破坏准则可对破坏深度进行预测。

Based on the brittle failure criterion, the relationship between different in-situ stress environments, opening shapes, openings and the depths of brittle failure af were analyzed by Examine2D software. Based on the rule of in-situ stress in China, a series of analyses were carried out to investigate the depth of brittle failure for circular shape in sedimentary. The results show that with the increase of principal stress ratio k, the depth of brittle failure αf increases in the form of line and damaged region diverges the direction of the minimum principal stress to the angle of 45° between the minimum in-situ stresses. The damaged region in single opening is axisymmetric, but point-symmetric in openings. Yield region of openings is easy to merge when the angle between the maximum principal stress direction and cavern connection line is 45°. With the increase of the spacing of openings, cavern group effect reduces gradually and the depth of brittle failure is almost equal to that of the single opening. Stress concentration factors in different excavation shapes are different. The depth of brittle failure effectively reduces when the length of prolate axis and minor axis equals k. With the increase of σc, αf shows increase trend in the form of exponent. When σc is greater than （9σ1^0-3σ3^0）, there will be no brittle failure. Magmatic and metamorphic are compared with those in practical engineering, indicating that the results agree well to each other. It can be used to predict the depth of brittle failure in underground excavation.