This paper analyzes on the reasons why the accidents of the gas explosion occur in the tunnel,and puts forward some methods,measures and matters needing attention of the safe discharge of the gas.

The key technique in large caisson construction of marine works is introducing precast concrete works off site,rolling method,floating and installation in this paper.

Analysis of laying position of new inner blowout preventer;

The laying position and well blowout pressure are analyzed and discussed briefly and the relationship curve of drill bit pressure drop vs flowrate and fluid density i.