The pipeline crossing plan of cofferdam, diversion and deep-wide excavation is chosen finally by comparing it with other river crossing plans such as underwater trench digging and directional control drilling.

The construction diversion of the Tankeng Hydropower Station has the characteristics of big discharge and quick flow speed on its overflow cofferdam.

Design and construction methods on river diversion and river closure for the Laxiwa hydro project on the Yellow River, developed based on the hydrologic, climatic, topographic and geologic conditions, are described.

Through the research and the implementation of the navigation of the d iversion channel in TGP, and under the conditions of huge river diversion discha rge and extremely high navigation stream, the diversion channel satisfied the tr ansit capacity of passenger and goods and successfully solved the key technologi cal problems of the river diversion and the construction navigation.

Opinion about viscous flow conductance;

Two methods of measuring conductance are introduced under the condition of molecular flow,namely,with constant volume method and constant pressure method.

The principle and method ofmeasuring conductance with PID constant pressure control mode and sawtooth variation constant pressure control mode are introduced.

It is al-so pointed out that the formulae of calculation of the flow conductance in physics of vacuurn are wrong be-cause of the incompressibility of the steady flow of viscous gas in conhadiction to the ideal gas equation.

When water to be drained and dropping head o f foundation delve are small, filter diversion, duct diversion, well draining an d blind ditch diversion can be adopted.