上坡条件下盾构开挖面极限支护压力研究

A Study on the Support Pressure Limit of the Excavation Face of Shield Tunnel under Upslope Conditions

近年来盾构施工技术已广泛应用于隧道工程,在盾构掘进过程中维持开挖面的稳定是整个盾构施工的关键。在越江隧道中,由于江底土的埋深较地面要低许多,盾构在穿越时必然比一般的平地隧道具有更大的纵坡坡度,研究坡度条件下的开挖面极限支护压力大小具有实际工程价值。采用极限分析上限法,建立土体破坏模型,推导上坡条件下的开挖面极限支护压力理论公式,并与平坡条件下和上坡条件下的有限元分析结果进行对比,分析结果表明:理论计算能很好地用于粘聚力较大或内摩擦角较大的土体,可以很好地用于实际工程;随着坡度角的增大,维持开挖面稳定所需的极限支护压力显著增大,且与坡度角呈线性关系。

Shield construction technique has been widely used in tunnel project in recent years,and the stability of the excavation face is a key problem in the design of shield tunneling.Because the buried depth of the river subsoil is much lower than ground surface,the cross-river tunnel will have heavier gradient than that of average tunnel.The study on the support pressure limit of the excavation face under upslope conditions will be of practical engineering value.In this paper,the soil damage model is proposed and its corresponding theoretical formulas are derived based on the upper-bound method of limit analysis.The theoretical results are compared with those of the finite element analysis in both flat and upslope cases.The results indicate that the theoretical method is suitable for the soils with larger cohesion or internal friction angle and it can be well applied to practical engineering.Along with the increase of slope angles,the support pressures limit for the excavation face increase significantly and are correlated linearly with the slope angles.