ENGINEERING GEOLOGICAL PROBLEMS ASSOCIATED WITH KARST TERRAINS: THEIR INVESTIGATION. MONITORING, AND MITIGATION AND DESIGN OF ENGINEERING STRUCTURES ON KARST TERRAINS

The design and construction of civil engineering structures in karst regions confronts many problems due to unpredictable location, dimensions and geometry of the karst structure and voids. Karst terrain is one of the most intricate grounds to be assessed for civil engineering purposes. Conventional methods of site exploration like desk studies, site reconnaissance, borings, test pits, geophysical techniques, have their advantages and disadvantages; none of them are 100% accurate; therefore they should be used in concert, adapted to each project, the available budget and the undertaken risk. As not two sides are identical in karst, site investigation should be tailored to each site. Factors that should be considered when designing site investigation in karst are: maturity of karst landforms, depth of the karst features, overburden thickness, lateral extent of the karst features, hydrogeology of the area, laoding, etc. The main problems confronted by engineers designing structures on or in karst terrain are: difficulties in excavation and grading the ground over pinnacled rockheads; collapse of the roof over subsurface voids, subsidence of cover soil over sinkhole, difficulties in founding a structure over an irregular or pinnacled rockhead, loss of water from dam reservoirs, pollution of groundwater, etc. A number of solutions have been practiced by engineers to solve these problems like: relocating the structure on a safer site, filling the voids and the fractures with concrete, improving the foundation ground with grouting and/or geogrids, replacing foundation soil, bridging the voids with rigid mats orbeams, using deep foundations (piling, drilled shafts, etc.), minimizing future sinkhole development by controlling surface and ground water, etc