Clay hardening grouts is overwhelmingly superior to others when it is applied for consolidation on shallow-hidden karst roadbed in Louzhan Railway Line by stuff and horizontal curtain grouting,for example,its lower construction cost,simple and practical technology,good property in intercepting ground.

According to problems and present academic disputes around geotechnical engineering survey on engineering with blind karst,some analysis and demonstration were made based on the general condition of surveyed area.

Evaluation on the karst collapse susceptible degree in covered karst region ——Example for Taian City;

The covered karst is the great important engineering geologic problem recently discovered in Three Gorge Reservoir region.

To eliminate the hidden disasters of covered karst, to ensure safety of rail transportion, and to research on the mechanism and operational technology of the grouting remediation, to optimize design parameters, to reduce construction costs, the five subgrade sections of typical karst phenomena are selected and tested for grouting treatment prior to construction in large scale.

This paper proposes the problem of classification concerned with the two kinds of hidden karst which are quite different in engineering geological specialities.

The paper adopting integrated geophysical technique of ground penetrating radar combination with seismic imaging method and using an application of the successful detection of the karst and fissure zone in a tunnel of Yiwan railway as example,confirms the effectiveness and feasibility of the method in the exploration of hidden karst in railway tunnel.

The covered karst water in Dacha valley is consider ed as an independent rectilinear system by the exponent\|piston model(EPM).