盾构平衡压力理论计算与应用技术

Theoretical calculation and application technology of the shield balancing pressure

为了确保盾构穿越附近地表及建(构)筑物的安全,无论是土压平衡盾构还是泥水平衡盾构开挖面平衡压力的准确选取十分重要。对现今常用的周边圆弧形刀盘开挖面进行分析,通过开挖面几何尺寸理论计算准确推导出圆弧形刀盘开挖面原状土体无变形的各个点平衡压力计算公式。依据平衡压力计算和穿越不同地层、不同危险源提出周边圆弧形刀盘盾构土舱压力选取原则:在软弱地层、穿越重大危险源地段要严格按照平衡压力保压掘进,盾构土舱压力选取介于盾构上覆水土自重应力与静止侧向水土压力之间;在地层有一定成拱效应并且无重大危险源地段,根据地表沉降监测情况可适当降低平衡压力,盾构土舱压力选取介于地层水土自重应力与最小极限平衡压力之间,让地层土拱效应起作用,降低刀盘、刀具等的磨损。对于前大后小盾体的盾构机提出盾构在穿越软弱地层或重大危险源地段在盾体周围以平衡压力注入一定量的粘土,可有效降低盾体上方地表的沉降。对土压平衡和泥水平衡盾构施工有一定的指导作用。

In order to guarantee the safety of shielding crossing neighborhood ground surface and buildings,it is rather important for the accuracy selection of excavation balancing pressure no matter soil arching balancing shielding or slurry balancing shielding.The paper analyzes common circular arc cutterhead excavation surface at present,accurately induces the balancing pressure calculation formula of each circular arc cutterhead excavation soil point on the basis of geometry theories of the excavation surface.According to balancing pressure calculation and crossing various stratum and different risk sources,it puts forward the Earth-Pressure-Balanced(EPB)selecting principles of surrounding circular arc cutterhead:at the section of weak stratum and crossing major hazard source section,it is a must to strictly follow balancing pressure protecting shielding and to select the shielding EPB between shielding floating self-weight stress and static lateral water-soil pressure;at the section of stratum with certain soil arching effect and without major hazard source,according to the surface settlement monitoring conditions,it can reduce balancing pressure and select the shielding EPB between stratum water self-weight stress and minimum limit balancing stress,with a view to play the role of soil arching effect,to reduce the cutterhead and cutter abrasion.As far as the shield tunneling machine with large in front and small in back,it is suggested to infuse certain clay with balancing pressure surrounding the shield tunneling machine while shielding crossing soft weak stratum and major hazard source section,which can effectively reduce the ground surface settlement.Therefore,it has certain guiding role for EPB and slurry balancing shielding construction as well.