富水砂层冻结暗挖法C形联络通道设计与工程实践

Design and Engineering Practice of C-Shaped Connecting Gallery for Frozen Excavation Method in Rich Water Sand Layer

为解决复杂环境和富水砂层中地铁盾构叠落区间C形联络通道安全实施的问题,采用以“先下、后上、再中间”为施工工序的分部暗挖工法和与之匹配的分时间、分区域冻结辅助工法。首先,根据埋深确定各部位的冻结壁厚度及其他主要冻结参数,并对冻土进行试验,取得各层位冻土强度指标;对冻结壁进行强度验算,验算结果满足安全系数要求。其次,合理布置地面垂直及隧道内水平冻结管并采取技术措施减小交叉冻结、冻胀的影响,保证冻结效果。再次,在联络通道各部位预埋注浆管,根据解冻进程,从下至上以“多点、少量、多次、均匀”的方式进行融沉注浆,控制结构和地层沉降。最后,施工期间对冻结壁、结构、地面及周边环境状态进行监测,并根据监测数据对施工进行修正指导。结果表明:采用该冻结暗挖法施工C形联络通道安全可靠,冻结壁强度高、止水性好、冻胀融沉小,结构受力变形及对周边环境的影响均较小。

In order to solve the problem for safe implementation of C-shaped connecting gallery in the overlapping section of metro shield tunneling in complex environments and rich water sand layers,a segmented hidden excavation method with"first lower,then upper,and finally middle"as the construction process and a matching time-based and regional freezing auxiliary method is adopted.First,the thickness of the frozen wall and other main freezing parameters for each part are determined,and tests are conducted on the frozen soil to obtain the strength indicators for each layer of frozen soil.Strength verification is conducted on the frozen wall,and the verification results meet the safety factor requirements.Second,the ground vertical and horizontal freezing pipes inside the tunnel are reasonably arranged,and technical measures are used to reduce the impact of cross freezing and frost heave,ensuring the freezing effect.Then,pre-embedded grouting pipes are used in various parts of the connecting channel and thawing and settlement grouting are carried out from bottom to top,using the way of"multi-point,small amount,multiple times,and even"according to the thawing process,to control structural and geological settlement.Finally,the status of frozen walls,structures,ground,and surrounding environment during construction is monitored,providing guidance for construction correction.The results show that:by using the proposed method to construct the C-shaped connecting gallery,high strength of the frozen wall,good water sealing performance,small frost heave and thaw settlement,minimal structural deformation and impact on the surrounding environment can be achieved.