According to this principle, the backflow patterns in the impeller with differently offset short blades are analyzed for a situation in engineering practices by using the slippery theory.

According to the data simulated and the pump performance experimentally measured,the slippery theory can be used to accurately predict the pump head at design condition and the effect of blade angle on the pump performance.

In this article, the roll-cutting and grip forces are investigated by the cutting theory and the slip line theory.

The plastic zone and pressure distribution on conditions of width-height ratio ,friction coefficient of contact surface f≠0 and any given value of relative density of workpiece in plate upsetting compressible sintered material are determined based on the slip line theory and numerical solution of slip line field.

The ultimate bearing capacity of the soil around the Push-extend Multi-under-reamed Pile is decided, according to the failure principle of soil and the theory of sliding line, at the same time, the calculate model of the soil stress is applied, to combine the theory of plasticity potential energy wi.

Through test and analysis about the principle of the soil around the push-extent multi-under-reamed pile, it is provided that the failure of soil under the multi-under-reamed of bearing loads is based on the theory of sliding line.