Abstract:

Large immersed tunnels constructed in the middle reach of an inland river encounter strong riverbed erosion, deep permeable strata, and stringent flood control requirements. In this study, a case study is conducted on the Yuliangzhou immersed tunnel in Xiangyang, China. Several methods, including engineering research, theoretical analysis, physical model testing, numerical simulation, and onsite testing, are employed to apply innovative construction technology in the construction of an immersed tunnel under an inland river. Some achievements related to this case study are as follows. (1) A quantitative evaluation method for the scouring safety of the immersed tunnel is proposed and five evaluation indices and a standard system for their evaluation are provided. (2) A frictionthrusttype final joint, which utilizes the frictional force around the immersed tunnel to resist the elastic force of the waterstop and does not require large masonry structures, is developed. (3) A domestically produced waterstop strip is developed on the outer side of the joint and massproduced to achieve the water tightness required to withstand 0.3 MPa of external water pressure and to offer a design service life of 100 years. Its stress relaxation attenuation rate over 100 years is only 255%, and its predicted service life is 144 years. The domestic production of the strip enables the localization of the entire production chain of immersed tunnel technology to China. (4) A continuous pouring prefabrication method is proposed without pouring postpouring strip for whole sections of integral tunnel joints. This method achieves a 52% improvement in the prefabrication efficiency of immersed tunnel structures, a 61% reduction in structural joints, and a 60% reduction in pouring cracks. (5) Initially, a pebble cushion foundation is laid, and a fully floating and highprecision leveling ship for the pebble foundation is developed. (6) An unwelded assembly end sealing door and a flexible water compression system with water bag ballast are developed and applied for convenience and recyclability of the outfitting facilities, as well as to improve construction efficiency.