拱顶空洞对浅埋暗挖隧道的影响及其防制

Influence of Vault Cavity on the Shallow Buried Tunnel and Its Prevention and Control

研究目的:在城市地铁修建中,空洞的存在往往会加剧地层的变形,甚至引起坍塌事故的发生。在隧道开挖扰动下,探究空洞存在对地层稳定性产生的影响,可以为施工过程中事故的防制提供有效的参考。本文依托青岛地铁工程,通过模型试验与三维有限元模拟,研究空洞在隧道正上方时,开挖过程中地层的失稳机制,并为解决该地层现象提出合理的控制对策。研究结论:(1)随隧道开挖,拱顶处塌落范围逐渐向上扩大,上方地层空洞会受到扰动,轮廓线逐渐闭合,最后完全消失与隧道拱顶塌落融合,同时空洞的存在会加剧地表的沉降,甚至造成隧道上方地表的贯通式坍塌;(2)采用超前地质预报手段可以有效地确定施工地区地层中不良地质体的位置,通过地面注浆与洞内注浆相结合的方法预防空洞坍塌事故的发生,并通过现场地表沉降实测数据证实了超前地质预报与注浆处治相结合的方法对地层空洞预防控制工作的有效性,可为后期的隧道工程中含空洞地层的治理提供参考。

Research purposes: In the construction of urban subway,the existence of voids often aggravates the deformation of the stratum and even causes the collapse accident. The study on the mechanism of formation instability caused by tunnel excavation disturbance can provide effective reference for the prevention and control of this kind of accidents. Based on the Qingdao subway project,this paper studies the instability mechanism of the stratum during excavation when the cavity is directly above the tunnel through model test and numerical simulation method,and designs a reasonable control strategy for solving this phenomenon.Research conclusions:( 1) As the tunnel excavates,the collapsed area of the vault gradually expands upwards,the upper stratum will be disturbed,the contour will gradually close,and finally disappear completely and merge with the tunnel vault collapse. At the same time,the existence of the cavity will aggravate the surface subsidence and even cause the through-type collapse of the surface above the tunnel.( 2) The advanced geological prediction method can effectively determine the location of the unfavorable geological body in the stratum of the construction area,and prevent the occurrence of the cavities collapse accident by combining the ground grouting with the grouting in the cave. The field surface sedimentation measured data confirms the effectiveness of the combination of forecasting and grouting treatment on the prevention and control of formation cavity,which can provide reference value for the treatment of cavity formations in later tunnel engineering.