岩石围岩盾构钢筋混凝土内衬高内压输水隧洞受力简化分析方法

长距离输水工程在穿越城市群时,往往需要深埋以规避地表及浅层地下的各类建(构)筑物。这种情况下盾构隧洞成为极具优势的选择方案。当这种深埋隧洞的围岩具有较好承载能力时,可以采用钢混凝土内衬与盾构组成复合衬砌,与围岩一起共同承担管道内的高内水压力。而这种隧道结构的内衬往往会发生开裂,进而改变其受力特征,此时内衬、盾构管片与围岩如何共同受力成为了工程设计的重点和难点,对此目前还没有成熟的计算方法和规程。针对钢筋混凝土受内水压开裂后的受力变形特点,提出了钢筋混凝土内衬开裂后刚度减少的等效刚度计算方法,计算在内水压力作用下复合衬砌与围岩共同作用的受力特点。结果表明:当围岩弹性模量达到2 GPa时,这种结构可以具有较好的承载能力;当围岩弹性模量达到5 GPa时,可以承担1 MPa以上的内水压力,围岩具有较好的利用价值。研究结果为盾构钢筋混凝土内衬高压输水隧洞联合受力提供了简化的计算方法。

Simplified Analysis of Forces Acting on Reinforced Concrete Lining inHigh Pressure Water Conveyance Shield Tunnel under SurroundingRock Condition

Long-distance water conveyance projects often need to be buried in deep to avoid surface and shallow underground structures when crossing urban agglomerations. Shield tunnels have become an advantageous option. When the surrounding rock of tunnel is of good bearing capacity, composite lining comprising reinforced concrete inner lining and shield can be adopted together with the surrounding rock to share the high water pressure inside the tunnel. In this case, cracks are often found on the inner lining, hence changing its force characteristics. The joint forces acting on inner lining, shield segments, and surrounding rock have been the emphasis and challenge for engineering design. Yet, mature calculation method or specification is still in lack. In view of the deformation characteristics of reinforced concrete subjected to internal pressure and cracking, a simplified method of calculating the equivalent stiffness of reinforced concrete lining after cracking is proposed to calculate the joint actions of composite lining and surrounding rock under internal water pressure. Calculation result indicate that such composite structure is of good bearing capacity when the elastic modulus of rock reaches 2 GPa; when the elastic modulus amounts to 5 GPa, the composite structure could bear an internal pressure over 1 MPa. Surrounding rock can be well utilized.