深部软弱围岩叠加拱承载体强度理论及应用研究

STUDY OF STRENGTH THEORY AND APPLICATION OF OVERLAP ARCH BEARING BODY FOR DEEP SOFT SURROUNDING ROCK

目前,长锚索与锚喷网支护相结合的支护方式在深部软弱围岩中已经得到了广泛应用,但是对于这种联合支护结构的承载特点缺乏深入了解,特别是对于初次支护和二次支护的承载能力没有量化解析式。因此,在岩石力学理论的基础上,针对深部软弱围岩的"锚喷网+锚索"联合支护特点,提出由主压缩拱(锚杆支护)和次压缩拱(密集型锚索支护)共同构成的叠加拱承载体力学模型;根据弹塑性理论、锚杆的中性点理论和锚索的力传递机制推导初次支护和适当让压后二次支护的承载体强度方程;并将"围岩-支护结构"组成的共同体看作一种等效耦合围岩,运用弹塑性力学方法得到这种等效耦合围岩的力学参数随释放位移(让压位移)变化的关系式。工程计算表明,金川III矿区破碎硐室经叠加拱支护后,极限承载能力q′max可达到513.34kN,等效耦合岩体?e值可达到47.54°,ce最大值为1.37MPa,提高围岩的峰后强度,有利于硐室围岩的长期稳定;现场监测也表明,进行叠加拱承载体支护后的硐室围岩变形趋于平稳,收敛速率小于0.1mm/d。

At present,the combined support method of long anchor cable and bolt shotcrete mesh is widely used in deep soft surrounding rock,but it is very deficient in understanding on bearing behavior of the combined supporting structure;and it still lacks quantitative analytical formulae especially for bearing capacities of primary supporting and secondary supporting.In allusion to the united supporting characteristics of anchor,spray net and cable of deep wall rock,the mechanical model of overlap arch bearing body were put forward based on rock mechanics theory,which are composed with the main compression arch（bolt supporting） and the secondary compression arch（intensive cable supporting）.By means of elastoplastic theory,neutral point theory of bolt and force transferring mechanism of cable,strength equations of the bearing body of primary supporting and second supporting were deduced.Community composed of wall rock and supporting structure is regarded as an equivalent coupling surrounding rock;and relation equations of rock mechanics parameters of surrounding rock with release displacements（yield displacements） were obtained from the method of elastoplastic mechanics.Computational results of engineering indicate that the peak intensity and bearing capability of rock mass were enhanced obviously for the breaking cavity of Jinchuan Mine III after the support of overlap arch;the limit bearing capacity qm＇ ax of equivalent coupling surrounding rock can reach 513.34 kN;the value of ？ e can reach 47.54o and the value of ce can reach 1.37 MPa.Monitoring data also show that deformations of surrounding rock supported by overlap arch bearing body trend to be stable,convergence rate of which is less than 0.1 mm/d.