Prevention and Remediation in Karst Engineering

In karst areas, a special approach must be applied in order to counteract seepage from future reservoirs, to prevent groundwater intrusion into underground excavations, to prevent groundwater contamination from waste disposal, or to predict and stabilize subsidence prone sites. To cope with such problems, two considerations have to be kept in the mind: effectiveness and costs. In many cases, grouting alone is definitely not adequate, as in the case of large karst voids or huge collapses (subsidence). On the other hand, large surface and underground structures are very expensive. Certain flexibility is necessary during construction of remedial structures in order to find the best compromise between these two basic ways to treat karst. To deal with karst treatment successfully, innovation, engineering practice, execution feasibility and commercial understanding must all be employed. In this regard it has to be understood that an economic solution needs investment in both investigations and the solution. In karst engineering, the final design of a grout curtain or any other remedial structure, can only be defined during the execution phase. Such an approach is the basic rule in the fight against hydrogeological and geological engineering problems in the karst environment, worldwide. The most frequent technical difficulties are: the presence of caverns along tunnel routes or at dam sites; leakage from reservoirs; groundwater intrusion during underground excavations, and natural or induced subsidences in reservoir bottoms and urban areas. To reduce or eliminate the above listed difficulties, two alternatives of prevention and remediation are feasible: surface treatment and sealing underground, by different geotechnical approaches.