The determination of the cover thickness of the submarine tunnel is very important,because it will be very dangerous if the cover thickness is too small,whereas the length,slope gradient and cost will be increased after a larger cover thickness is chosen.

In underwater tunnel construction,the cover thickness not only plays the decisive role in its security,but al- so is a leading factor determining the underwater tunnel s cost and length.

In underwater tunnel construction,to confirm the reasonable cover thickness is the key in the technology.

The method can determine the overburden thickness based upon the electricity difference between overburden and lower datum rock, and is one of the most valid method with high-efficiency, depth and accuracy for ground electricity section imaging in hydrogeology and engineering geology.

12 construction schemes are constituted according to the space temporal relationship between construction steps,the excavating method,the length of drivage cycle,the space distance among each working face and the overburden thickness of each tunnel.

The principle,applicability range,advantage and disadvantage of electromagnetic,eddy current method、βbackscatter method and XRF methods for nondestructive testing coating thickness of material have been reviewed.