强风化软岩地层盾构隧道荷载及受力特性分析

External Load and Stress Characteristics of Shield Tunnel in Strongly Weathered Soft Rock

为探明既有隧道衬砌设计理论能否较好契合强风化软岩盾构隧道并获取管片实际受力特性,依托南昌地铁1号线北延段区间盾构隧道工程开展现场测试,对管片所受外荷载及结构内力进行长期监测。同时,建立相应的盾构管片精细化数值模型,并与实测数据对比验证,进一步探究管片受力特性。结果表明:1)管片环外水土压力受同步注浆影响最显著是在脱环5环内,隧底土压力小于隧顶,水压力占总土压力的绝大部分;2)管片所受竖向土压力呈“中间大、两头小”的分布模式,拱顶附近实测值最大,与太沙基理论、普氏理论、隧规法计算值分别相差近20%、30%、42%,故该地层下隧道竖向土压力按太沙基理论计算较为合适;3)数值模拟所得管片内力与实测值吻合较好,管片弯矩整体呈“蝴蝶形”,拱顶弯矩值略大于拱底。

In order to find out whether the existing tunnel lining design theory can better fit the actual stress characteristics of the strongly weathered soft rock shield tunnel and lining segment,a case study is conducted on the shield tunnel project in the northern extension section of Nanchang Metro Line 1,and the field test is carried out to monitor the external load and structural internal force of the segment for a long time.Meanwhile,a refined numerical model of the shield is established,and the mechanical characteristics of the segment are further explored and compared with the measured data.The results show that:(1)The most significant influence of the earth pressure and water pressure outside the ring of the pipe sheet is within five rings off the segment.The earth pressure at the bottom of the tunnel is less than that at the top of the tunnel,and the water pressure accounts for the majority of the total earth pressure.(2)The distribution mode of the vertical earth pressure on the segment is"large in the middle and small at both ends".The measured value near the vault is the largest,which has a difference of nearly 20%,30%and 42%respectively compared with the calculated values of Terzaghi theory,Platts theory and tunnel specification method.It is more appropriate to calculate the vertical earth pressure of tunnel in strongly weathered soft rock stratum according to Terzaghi theory.(3)The internal force of the segment obtained by numerical simulation is in good agreement with the measured value.The overall bending moment of the segment exhibits a butterfly shape.The bending moment of the vault is slightly larger than that of the arch bottom.