盾构隧道管片施工期上浮影响因素的现场试验研究

FIELD TEST RESEARCH ON INFLUENCE FACTOR OF UPWARD MOVING OF SHIELD TUNNEL SEGMENTS DURING CONSTRUCTION

针对盾构掘进施工时常面临的管片局部或整体性上浮问题,依托宁波地区2例施工期发生较大上浮的地铁盾构隧道工程实例,选择地层特性、埋深等外部条件相似的区段建立掘进速度、总推力反力的竖向分力、同步注浆压力等盾构施工参数以及同步注浆浆液配比的现场试验段,并结合试验段管片上浮的现场监测数据分析上述不同单一因素对施工期管片上浮的影响规律。研究结果表明:管片下半侧注浆压力高于上半侧注浆压力时,管片上浮量增大,当压力差达0.3 MPa时,管片上浮量增加约20 mm;总推力反力变化不大的基础上,其竖直向上的分力增大时,管片上浮量相应增大,当分力增加260 kN,管片上浮量增加约15 mm;在同步注浆胶凝材料总量不变、且非胶凝材料掺量不变的基础上,随着粉灰比、水灰比的减小,浆液抗压强度、黏聚力提高,初凝时间缩短,管片上浮量减小,当每3 m3浆液中水泥的相对掺量增加100 kg,管片上浮能减小19.8 mm;掘进速度单因素对施工期管片上浮无明显影响。

Aiming at the problem of partially or integrally upward moving of tunnel segments during shield tunnel construction,based on the two metro shield tunnel project cases in which the great upward moving occurs in Ningbo, the field test of shield construction parameters,such as tunneling speed,vertical component force of reaction force of total thrust,synchronized grouting pressure and grout proportion,is conducted in the section that the external conditions(formation characteristic and burial depth) are similar. And combined with the monitoring data in the test section,the influence law of aforementioned single factor on segments upward moving during construction is analyzed. The results show that the amount of segment upward moving increases,when the grouting pressure of the lower segment is higher than that of the upper part. When the pressure difference is up to 0.3 MPa,the amount of upward moving increases about 20 mm. On the basis of little change of reaction force of the total thrust,when its vertical component force increases,the amount of upward moving raises correspondingly. When the component force increases by 260 kN,the amount of segment upward moving grows greater to about 15 mm. Keeping the same amount of cementitious material and mixing in equivalent non-cementitious material during synchronized grouting,the compression strength and cohesion of grout improve,the initial setting time shortens and the segment moves less higher with the reduction of ash cement ratio and water cement ratio. When the relative addition of cement in every 3 m3 of grout increases by 100 kg,the amount of segment upward moving decreases by 19.8 mm. the tunnelling speed,alone,has no distinct impact on upward moving of segments during construction.