斜井掌子面形状与倾角对隧道开挖面稳定性影响

Analysis of the influence of the tunnel face shape and the inclination of the inclined shaft on the tunnel face stability

基于强度折减极限有限元法,建立直立形、倾斜形和曲面形3种掌子面形状的模型。针对不同倾角的斜井模型,研究网格多少以及局部加密自适应网格对计算结果的影响,分析掌子面安全系数与破坏形状之间的关系,并将安全系数同有限元分析作对比。研究结果表明:网格越精细,安全系数越低;曲面形掌子面的稳定系数小于直立形式的,直立形式的小于倾斜形式的;掌子面越倾斜,越稳定,类似于起到核心土的作用;掌子面底部与拱顶存在次应变集中带,隧道在纵断面上存在分区破坏;当掌子面形状为微椭圆形时,其稳定性略有提高,但随着椭圆度增大,安全系数降低,实际施工中,椭圆度不宜控制,建议有条件下可采用斜掌子面;斜井倾角越大,掌子面稳定性越低,所以大倾角斜井与大反坡隧道施工,更要采取措施控制掌子面的稳定;低黏聚力的破碎围岩,应通过注浆等措施,改善围岩力学参数,提高掌子面稳定性。

Based on the strength reduction finite element method,three models of face shapes,vertical,different inclination,different ellipticity were studied,and inclined shaft models with different inclination angles were established.The influence of the number of mesh and the local encryption of adaptive mesh on the calculation results were studied.The safety factor and failure shape of the face were analyzed and compared with the limit analysis.The results show that:the finer the grids,the lower the safety factor;the coefficient of stability of a circular face is smaller than that of an vertical form,and that of an vertical form is smaller than that of an inclined form;The more inclined the face is,the more stable it is,which is similar to the role of core soil.There is a sub-strain concentration zone at the bottom and the crown of the tunnel face,and there is zonal failure in the longitudinal section of the tunnel.The stability of the face is slightly improved under the micro ellipticity,but with the ellipticity increasing,the safety factor decreases.In actual construction,the ellipticity is not suitable to be controlled,it is suggested that the inclined face can be used under certain conditions;The larger the inclination of inclined shaft is,the lower the stability of the face is.Therefore,measures should be taken to control the stability of the tunnel face in the construction of inclined shaft with large angle and large reverse slope.For broken rock with low cohesiveness,grouting and other measures should be adopted to improve the mechanical parameters of the rock and improve the tunnel face stability.