Surveying Network Design for HongKong-Zhuhai-Macao Bridge Link Immersed Tunnel

For the construction of HongKong-Zhuhai-Macao(HZM) Bridge link immersed tunnel with the harsh environment and ultrahigh precision requirement, particular care should be taken in the perspective of geodetic control. Firstly, the breakthrough error is distributed reasonably based on the error distribution theory. The design and implementation of surveying network are discussed. To improve the configuration strength and increase the number of redundant observation compared with traverse, the design of underground surveying network named duo-linear joint chain is presented. It is verified that the precision of duolinear joint chain is high and this configuration can meet the requirement of immersed tunnel underground survey by a simulation experiment. The index of precision and reliability is improved 15%-30% and 4% based on the data analysis that measured in HZM link immersed tunnel. The work is demonstrated by the gratifying results of the breakthrough of HZM immersed tunnel.