盾构输水隧洞灌浆式预应力衬砌结构有限元分析

北京市南水北调配套工程东干渠工程输水隧洞施工工法为盾构法,为了提高其抗渗和抗裂特性,并优化内外衬的协同变形,衬砌结构采用了灌浆式混凝土预应力衬砌。研究了隧洞衬砌结构设计参数及工作机理,采用二维有限元计算方法,分析了预应力注浆压力和连接螺栓型号的影响。结果表明:内外衬之间的预应力式注浆可以提高二衬混凝土承受内水压力的能力,预应力注浆压力不宜大于0.3 MPa,否则将影响管片的结构和防水安全;连接螺栓刚度变化对管片和二衬混凝土环向应力的影响很小,结合管片张开对防水、防渗的影响,连接螺栓型号采用M20以上型号均可;随着预应力注浆压力的增加,二衬混凝土受力状态得到明显改善,由全断面受拉构件变成受弯构件,拉应力区明显减小,内外衬协同受力状态得到优化。

Finite element analysis on pre- stressed grouted concrete lining of water conveyance tunnel constructed by shield tunneling method

The construction method for the water conveyance tunnel of the east main canal———ancillary works for South-to-North Water Transfer Project in Beijing is the shield tunneling method. In order to enhance the impermeable and anti-cracking characteristics of the tunnel and optimize the collaborative deformation of its inner and outer linings，the pre-stressed grouted concrete lining is adopted for its lining structure. The design parameters and working mechanism of the lining structure of the tunnel is studied herein，while the impacts from the pre-stressed grouting pressure and the type of the connection-bolt are analyzed with 2 － D finite element analysis method as well. The result shows that the pre-stressed grouting between the inner and outer liningsn can enhance the capacity of the secondary lining concrete to bear the internal water pressure，for which the pre-stressed grouting pressure is inadvisable to be higher than 0. 3 MPa，otherwise，the safety of the water-proof performance of the lining segment is to be impacted. The impact from the variation of the stiffness of the connection-bolt on the circumferential stress of the secondary lining concrete is quite less，and then all the types of the connection-bolt above M20 can be adopted in combination with the impact from the opening of the lining segment on the impermeable and waterproof performances. Along with the increase of the prestressed grouting pressure，the stress status of the secondary linin concrete is obviously improved and becomes the bending member from the full-section tensioning member with significant decrease of the tensile stress zone，thus the collaborative stress status of the inner and outer linings is optimized.