The construction of subsea tunnel is high risky and water inrush is one of the main risk sources. If water inrush into the tunnel

it will have an important influence on the safety of construction as well as the control of operation cost after the subsea tunnel is completed. So making water inrush forecast is very important in the construction phase. Numerical analysis is the most popular method used in the prediction of water inrush at present

of which ascertaining the permeability coefficient is one key problem. Taking Qingdao Jiaozhouwan Subsea Tunnel as the project background

this paper deals with water inrush forecast during the subsea tunnel construction period by comprehensive usage of numerical computation

model test and local monitoring data analysis. Firstly

variation curves of the water inrush are got by monitoring the water inrush after tunnel excavation. Then numerical method is used to calculate the water inrush. During the process of calculating

parameters are adjusted constantly to fit the curve successfully. The permeability coefficient obtained is reasonable; it should be used in the numerical computation. Combined with the model geology

the relationship between the reasonable permeability coefficient and the permeability coefficient which is got from geological packer test in the early stage is obtained by comparison. Then model test is used to verify above conclusions. Finally

the conclusions can be used to other sections of subsea tunnel to make water inrush forecast. The result has significance for practice reference.