土压平衡盾构机土舱压力的设定方法及原位实测反分析

Configuration Method and Field Measurement Back Analysis of Earth Pressure in Working Chamber of Earth Pressure Balance Shield Machine

通过分析盾构机刀盘开口率、穿越土层性质、隧道线型和地面超载4个因素对EPB盾构机土舱压力设定的影响,提出土舱压力的土性修正系数和曲线修正系数,建立既能体现土层性质又能反映隧道线型的土舱压力设定方法。基于杭州地铁盾构隧道施工的监测数据,以地表变形为筛选指标析出典型区段土舱压力的原位实测数据,并以此对开口率为36%的辐板式盾构机和开口率为65%的辐条式盾构机在淤泥质粉质黏土中分别以直线和曲线掘进时的修正系数进行反分析,得出相应的土性修正系数和曲线修正系数,并通过实例验证了修正系数的取值。结果表明:在给定土层中掘进时,开口率为36%的辐板式盾构机与开口率为65%的辐条式盾构机相比,前者挤土效应更明显,在曲线掘进时土舱压力的增量也较大;而后者的土舱压力更稳定。

The influence of four factors, including aperture ratio of shield cutter head, soil property, tunnel alignment and surcharge, on the configuration of the earth pressure in the working chamber of EPB shield machine was analyzed. Two correction factors concerning soil property and tunnel alignment were defined respectively to build an improved computing method to configure earth pressure in working cham- ber. Based on the in-situ monitoring data of the shield tunneling projeet of Hangzhou Metro, the in-situ measured earth pressure in the working chamber of typical sections were separated out with ground surface deformation as screening index. Then the two correction factors were analyzed respectively through back a- nalysis method by considering three main aspects, namely, the aperture ratios of shield machines （36~ for panel wheel type and 65% for spoke wheel type）, soil property （muddy silt clay） and tunnel alignment （straight and curve）. Finally, the corresponding under different conditions were obtained and also correction factors of soil property and tunnel alignment verified by a case study. The results show that, corn- pared panel wheel shield machine （the aperture ratio of 36~） with spoke wheel shield machine （the aper- ture ratio of 65~）, the compaction effect on soil from the former is larger than that＂ from the latter when tunneling in given stratum, and the earth pressure increment in the working chamber of the former is also larger than that of the latter during curve tunneling; while the earth pressure in the working chamber of the latter is more stable than that of the former.