浅埋富水地层特大断面矩形顶管隧道掘进参数分析

Analysis of Tunneling Parameters of a Shallow-Buried Super-Large Cross-Sectional Rectangular Pipe Jacking Tunnel

为保障特大断面矩形顶管隧道在浅覆土、小净距下的安全高效掘进,依托世界上首个直径15 m级3车道矩形顶管隧道工程,对顶管多刀盘开挖系统、减摩注浆系统、三螺机出渣系统进行针对性优化设计。通过对顶管主要掘进参数及地层沉降监测结果进行统计分析,得到以下结论:1)本工程采用的减阻措施有效降低了管节受到的地层摩擦阻力,实际总推力为理论值的40%左右;2)刀盘直径和安装高度对刀盘转矩影响较大,多数刀盘转矩均值小于额定转矩的一半,说明刀盘额定转矩有较大的优化空间;3)顶管掘进过程中盾壳受到较大的地层挤压力,土舱内渣土压力也显著大于地层侧向土压力,停机后上述压力均有较大幅度降低;4)顶管掘进后地表横向沉降槽呈“盆”状,隧道两侧0.5倍开挖宽度内的地层沉降较大。

The rectangular pipe jacking tunnel under Nanhu avenue in Jiaxing,China,is the world′s first 15-m diameter and three-lane pipe jacking tunnel.Targeted designs are implemented on the multi-cutterhead excavation,antifriction slurry grouting,and triple screw conveyor mucking systems to ensure the safe and efficient excavation of super-large cross-section pipe jacking under shallow soil and small clear distance conditions.Furthermore,statistical analysis is conducted on the main tunneling parameters of the pipe jacking machine and ground settlement monitoring results.Some conclusions are drawn as follows:(1)The friction reduction measures adopted effectively reduce the ground friction resistance of the pipe joint,and the actual total thrust is approximately 40%of the theoretical value.(2)The cutterhead diameter and mounting height considerably affect the torque.The average torque is less than half of the rated torque,so it can be optimized.(3)In the pipe jacking process,the shield shell is subjected to large stratum extrusion pressure,the residual earth pressure in the soil chamber is significantly greater than the lateral earth pressure of the stratum,and they both reduce after shield shutdown.(4)After pipe jacking excavation,the transverse surface settlement groove shows a U shape,and the stratum settlement within 0.5 times the excavation width on both sides of the tunnel is large.