Risk Control Of The Construction Of Xiamen Tunnel Through Regolith Sections

Xiamen East Tunnel (Xiang'an Tunnel), designed and constructed by Chinese domestic professionals and engineers, is the first large cross-section submarine tunnel in the mainland of China. This is of great significance.Kinds of unfavorable geological conditions make the construction through the regolith sections fraught with uncertainty. Thus, the construction through these sections inevitably becomes one of the most difficult subjects of the whole project. And the most important and significant work during the construction is risk analysis and control.In this paper, the geological conditions and the construction features of the regolith sections are introduced. And the cause of the risks during the construction through the regolith sections is analyzed. Therefore, the prevention of risk appears quite necessary and important.In the way of texture decomposition, main risk factors of the construction are identified. And the factors are graded by judging their probability and severity. Obviously, measures should be taken during the construction of Xiang'an Tunnel through regolith sections to reduce or avert the risks. In this paper, according to the characteristics of construction in soft wall-rock layer, adopting some results of risk theory, the source of risks of tunnel construction under special geological conditions is identified and the measures to deal with each risk factor are put forward. At the same time, advance geological forecasting before construction, special excavation methods in regolith sections determined by using numerical simulation, the parameter controlling of grout injection are emphasized as important measures to reduce the risks. Besides, emergency programmes should be taken into consideration during tunnel construction.