南昌典型地层土压平衡盾构掘进参数演化规律及地层可掘性分析

Evolution Patterns of Tunneling Parameters of Earth Pressure Balance Shield in Typical Strata in Nanchang,China,and Its Stratigraphic Boreability

为评价土压平衡盾构在南昌典型地层施工时的掘进效能,依托南昌地铁3号线绳金塔站—六眼井站区间盾构隧道工程,基于土压平衡盾构在全断面砾砂、全断面中风化泥质粉砂岩和砂-岩复合地层掘进时的施工记录数据,分析土压平衡盾构主要掘进参数在这3种典型地层中的演化规律,并引入贯入度、场切入指数和掘进比能等地层可掘性指标建立主要掘进参数间的相关关系,进一步基于此开展这3种典型地层的可掘性评价。研究结果表明:1)盾构在全断面砂层和全断面岩层掘进时主要掘进参数相对稳定,而在砂-岩复合地层掘进时总推力和刀盘转速明显增长;2)盾构由复合地层向全断面岩层掘进时,刀盘转矩逐渐减小,且在全断面岩层内刀盘转矩和总推力具有良好的线性正相关性;3)盾构由全断面砂层向全断面岩层掘进时,贯入度逐渐减小且其振荡性显著减小,场切入指数在复合地层和全断面岩层内具有相似的分布特征,但变化趋势相反,3种地层的掘进比能基本相近;4)在砾砂层和复合地层内,场切入指数与贯入度间存在显著的相关性,但在全断面岩层内相关性较弱;5)砾砂层的贯入度最大且场切入指数和掘进比能最小,表明土压平衡盾构在该地层掘进效能最优;6)整体上,相比于砂-岩复合地层,全断面砾砂和全断面中风化泥质粉砂岩地层的可掘性更好。

To evaluate the tunneling effect of the earth pressure balance(EPB)shield in typical strata in Nanchang,China,a case study is conducted on a shield tunnel from Shengjinta station to Liuyanjing station.The evolution patterns of the main tunneling parameters of the EPB shield in full-section gravel sandstone stratum,full-section argillaceous siltstone,and composite sand-rock strata are investigated.Then,some characteristic parameters of the stratigraphic boreability including penetration degree,field penetration index,and tunneling specific energy are introduced to establish the relationships between the investigated key tunneling parameters.On this basis,the stratigraphic boreability of these three types of strata is evaluated.The research results indicate the following:(1)The main tunneling parameters are stable relatively when tunneling in gravel sandstone and argillaceous siltstone strata.The total thrust and the rotation speed of the cutterhead increase considerably in the composite sand-rock strata.(2)The cutterhead torque decreases gradually when shield tunnels from composite sand-rock strata to argillaceous siltstone strata.There is a satisfied positive linear relationship between the cutterhead torque and the total thrust in the argillaceous siltstone strata.(3)The value and oscillation of the penetration degree decline obviously when the shield tunnels from gravel sandstone to argillaceous siltstone strata.There are similar distributed characteristics of the field penetration index in the composite sand-rock strata and argillaceous siltstone strata but exhibit an opposite variation trend.Nevertheless,the tunneling specific energies of shield in these three strata are close to each other.(4)Significant correlations between the field penetration index and the penetration degree are observed in both gravel sandstone and composite sand-rock strata,but the correlation is weak in argillaceous siltstone strata.(5)The shield has a highest penetration degree and lowest field penetration index and tunneling specific energy in gravel sandstone strata,indicating the best tunneling effect of EPB shield in such strata.(6)On the whole,the gravel sandstone strata and the intermediately-weathered argillaceous siltstone strata show a better boreability than composite sand-rock strata.