| Because tunnel construction inevitably disturbs stratum, ground settlement with different degree is generated resulting in unfavorable effect on safety of tunnel construction and surrounding environment. Especially in building undersea tunnel, there will be more risks caused by ground deformations. One of the most prominent characters of subsea tunnel is that it is very rich in water because of the infinitude of the ocean above. The control of strata settlement induced by tunnel construction especially for some unfavorable geologic bodies is one of the key techniques during tunnel construction.By the method of analysis field monitoring measurement data in detail and numerical calculation about Xia'men undersea tunnel:â‘ The regularity and features in shallow tunnels in clay are described in this paper. At the same time, the whole process of ground deformation is described in detail and reasons of the large settlement of ground deformations are analysed. The relation between ground surface crack space and ground surface settlement is made. The relation of crown and ground settlement is discussed too;â‘¡The relation between the thickness of grouting circle and ground surface settlement is made to determine the optimal grouting circle thickness of unfavorable geologic bodies;â‘¢By the measure of regression analysis and numerical simulation, we can get some main conclusions. The ground settlement caused by tunnelling is dependent on not only the distribution of stratums, ground properties, overburden, underground water and other objective factors, but also on the construction of method and technique level;â‘£Both site measurement and numerical simulation show that the deformation due to the change of initial stress in ground caused by excavation, loss of ground, consolidation owing to drainage are the principal factors for the ground surface settlement. The analysis method and result can guide the late construction in the optimization of construction method and controlling deformation.
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