确定交叉巷道锚杆支护参数的围岩平均应力集中系数分析方法

Parameter Determination of Bolt Support for Cross Roadway Based on Mean Stress Concentration Factor of Surrounding Rock

大跨度交叉巷道多采用锚杆支护,支护后巷道周壁应力分布的均匀程度可以作为评价支护参数合理性的指标。将支护后巷道周壁某一点大主应力与周壁大主应力均值的比值定义为围岩平均应力集中系数,用该系数表征巷道围岩的应力分布均匀程度。以某铁矿交叉巷道为研究对象,根据矿山工程条件及均匀设计试验方法,选取锚杆长度、锚杆间距和锚杆排距3个锚杆支护参数设计4种不同的支护方案,分别计算未支护与4种支护方案下巷道周壁的围岩平均应力集中系数,通过对比分析,确定最优的交叉巷道锚杆支护参数。结果表明:未支护时,巷道周壁围岩平均应力集中系数在0.3~2.9,应力分布极不均匀;锚杆支护后,最大围岩平均应力集中系数与未支护时相比降低幅度超过50%,围岩应力分布得到较好的改善;确定最优的支护参数为锚杆长度2.2 m、锚杆间距1.1 mm、锚杆排距1.0 mm,此时巷道周壁的围岩平均应力集中系数在0.9~1.19,其变化幅度仅有0.29,围岩应力分布较均匀;围岩平均应力集中系数能对围岩应力分布的均匀性进行有效评价。

Bolt support is widely used in large span intersecting roadway support engineering. The uniformity of roadway stress distribution after supported can be used as an index to evaluate the rationality of support parameters. The ratio of large principal stress at a point of roadway wall to the mean large principal stress of roadway wall is defined as the Mean Stress Concentration Factor of surrounding rock（MSCF）. This factor is applied to characterize the uniformity of surrounding rock stress distribution. Taking the crossing roadway as the research object,four different support schemes which consist of bolt length,bolt spacing and bolt array pitch parameters are designed based on the mine engineering conditions and the uniformity design test method. The MSCF of unsupported and four support schemes are calculated,respectively. The reasonable bolt support parameters of cross roadway are determined by comparison. The result shows that the MSCF of roadway wall is between 0.3 and2.9 and the stress distribution is not uniform when the roadway is not supported. Compared with the MSCF under unsupported condition,the decrease of MSCF is more than 50% after bolt support,which indicates that the stress distribution of surrounding rock is improved. The determined reasonable support parameters of bolt length,bolt spacing and bolt array pitch are 2.2 m,1.1 m and 1.0 m,respectively. The MSCF of roadway wall calculated by the aforementioned support parameters is between0.9 and 1.19,and the variation amplitude is only 0.29,which indicates that the stress distribution of the surrounding rock is more uniform. Therefore,the MSCF can effectively evaluate the uniformity of surrounding rock stress distribution.