地裂缝场地地铁隧道施工CRD工法优化研究

STUDY ON OPTIMIZATION OF CRD CONSTRUCTION METHOD FOR METRO TUNNEL THROUGH GROUND FISSURE SITE

以西安地铁6号线区间隧道浅埋暗挖施工穿越地裂缝场地为研究工程背景,考虑地裂缝场地的特殊性构建了基于传统CRD工法的施工优化工法,并对传统CRD工法和优化CRD工法施工开挖过程进行了三维动态的有限元数值模拟,结合现场监测试验数据,对比分析了两种工法下地裂缝场地地表沉降变形规律和地铁隧道受力变形特征。结果表明:两种CRD工法下地表沉降变形均呈反S型,大致可分为开挖前微小变形、开挖时急剧下沉变形及开挖后平稳变形等3个阶段;与掌子面距离越近,地面沉降速率越大;与传统CRD工法相比,优化CRD工法通过适当增加锁脚、锁腰锚杆数量,提高初支喷混强度,达到简化临时支护、扩大下台阶施工面、方便临时支护施作拆除和提升初支闭合、临时中隔壁拆除速度的目的,整体施工速度提升1.37倍,地表最大沉降量降低52.96%,影响范围减少22.17%,隧道拱顶最大沉降量降低54.53%;优化CRD工法具有施工速度快、影响范围小以及地表与结构沉降控制好等优点,不仅可以提高工程效益,而且可以保障施工安全性和隧道建成使用的可靠性。研究结果可为西安市及其他地裂缝发育区地裂缝场地地铁隧道暗挖施工提供科学参考和借鉴。

Based on the background of Xi’an Metro Line 6 section tunnel with shallow excavation construction through the ground fissure site,and considering the particularity of the ground fissure site,the construction optimization method based on the traditional CRD method was constructed.The three-dimensional finite element numerical calculation was carried out to simulate the excavation process of traditional CRD and optimized CRD method.Combined with in-situ monitoring test data,the surface settlement deformation of the ground fissure site and the stress deformation characteristics of the metro tunnel were analyzed.The results show that the surface settlement deformation is anti-s-shaped,which can be roughly divided into three stages:small deformation before excavation,rapid settlement deformation during excavation and stable deformation after excavation.The closer the monitoring points are to the tunnel face,the higher the ground settlement.Compared with the traditional CRD method,the optimized CRD method can increase appropriately the number of locking feet and waist bolts,improve the concrete strength of primary support properly,and so as to simplify the temporary support,expand the construction surface of the lower stage,facilitate the removal of temporary support,and improve the speed of the closure of the initial support and the removal of the temporary middle diaphragm.The construction speed of the optimized CRD method is 1.37 times faster than that of the traditional CRD method.The maximum surface settlement is reduced by 52.96%,the influence range is reduced by 22.17%,and the settlement of the tunnel roof is reduced by 54.53%.The optimized CRD method has the advantages of rapid construction speed,lower influence range,easily controlled surface and structure settlement,which can not only improve engineering benefit,but also guarantee the construction safety and the reliability of the tunnel construction.The research results can provide a scientific reference for the underground excavation construction of metro tunnel through ground fissure site in Xi’an city and other areas.