千米盲竖井注浆帷幕围岩塑性劣化特征研究

Study on the plastic deterioration characteristics of surrounding rock of grouting curtain for kilometric blind shaft

为了研究凿井开挖卸荷对千米竖井注浆帷幕堵水性能的影响,采用理论分析和数值模拟方法研究了竖井注浆帷幕围岩开挖卸荷塑性劣化特征。建立了轴对称荷载条件下竖井注浆帷幕和外部岩体的组合圆筒模型,采用厚壁圆筒理论对竖井注浆帷幕围岩进行了弹塑性分析,推导了竖井注浆帷幕塑性劣化区半径计算公式,得到了井筒开挖卸荷后注浆帷幕围岩二次应力分布特征和围岩响应曲线。以毛坪矿千米级盲竖井为案例,分析得到开挖卸荷后,竖井注浆帷幕围岩塑性劣化区半径为5.14 m,峰值切向应力为51.69 MPa,最大应力集中系数为1.72。结果表明:凿井开挖卸荷会导致注浆帷幕产生较大的塑性劣化范围,明显减小有效堵水帷幕厚度,不利于保证注浆帷幕堵水效果;竖井注浆帷幕围岩开挖卸荷塑性劣化半径对支护力敏感,增加支护力可有效控制注浆帷幕围岩塑性劣化范围,建议在凿井过程中及时支护,避免注浆帷幕围岩劣化范围继续扩大。论文研究成果可为千米竖井井筒基岩含水层注浆堵水提供技术参考。

In order to study the influence of excavation unloading on water sealing performance of grouting curtain for kilometric shaft,the plastic deterioration characteristics of surrounding rock of grouting curtain for vertical shaft was studied by theoretical analysis and numerical simulation.The.combined cylindrical model of the shaft grouting curtain and the external rock mass under the condition of axial symmetric load was established.The elastic plastic analysis of the surrounding rock of the shaft grouting curtain was carried out by using the thick-wall cylinder theory,and the calculation formula of the radius of the plastic deterioration zone of the shaft grouting curtain was derived.Also,the secondary stress distribution characteristics and response curve of the surrounding rock of grouting curtain were obtained after the excavation and unloading.The case study took Maoping Mine's kilo-meter-level blind shaft as an example,and the analysis shows that after excavation unloading,the radius of the plastic deterioration zone of the surrounding rock of the shaft grouting curtain is 5.14 m,the peak tangential stress is 51.69 MPa,and the maximum stress concentration factor is 1.72.The results show that the excavation unloading of shaft sinking will lead to a large range of plastic deterioration of the grouting curtain,and the effective water plugging curtain thickness will be significantly reduced,which is not sufficient to ensuring the water plugging effect of shaft pre grouting.In addition,the excavation and unloading plastic radius of the surrounding rock of the shaft grouting curtain is sensitive:to the support force.And by increasing the support force,the plastic radius of the surrounding rock of the grouting curtain can be effectively controlled.It is suggested to support in time during the shaft sinking to avoid the expansion of the plastic zone of the surrounding rock.The research results of this paper can provide technical reference for grouting to seal the bedrock aquifer in kilometric shaft sinking.