KarstALEA a ground investigation method for karst risk assessment the use for dam construction and remediation

Many recent dam constructions and remediation around the World have shown that uncertainties related to karst processes are a major issue, since they may lead toeconomic, social, security-related and environmental problems. The main difficulty beyond these problems is the poor predictability of the location and characteristics(e.g. active/fossil, phreatic/vadose, size, sediment filling) of the karst structures. Most ground investigation methods and classifications that are presently available forkarst issues do not include speleogenetic considerations and consider karstoccurrence as random distributed in space. These make any inter/extrapolation of observed/detected karst feature almost impossible. In the last years differenttechniques have been developed for the detection of voids a few metres in below the surface. But no method for the prediction of karst occurrences at the planning phasesof a project is available today. The lack of such a methodology of karst risk assessment is due to gaps inunderstanding speleogenesis, but above all to a missing transfer of knowledge from karst research to karst applied domains. Recent research results on the analyse of the 3D geometry of several large cavesystems around the world show that the development of karst conduits is not randombut predictable and linked to the existence of a few inception features. An inception feature is a discontinuity (e.g. joints, faults, bedding planes) or a part of alithostratigraphic succession that is particularly susceptible to the effects of the earliest cave forming processes. The evidence of the existence of inception featuresand the enhancements on the understanding of the development of underground karst structures in time and space, significantly improves the design and interpretation ofground investigation. Essentially, it is now possible to quantify the probability of karstoccurrences inside a karstic rock mass by identifying the few inception features that guide the karstification in regional scale, reconstructing the hydrogeolgical historyand winnowing different speleogenetical zones. Although the reconstruction of the true geometry (i.e. the exact position of the karstconduits and their characteristics) is yet not feasible, it is possible to delimitate zones of different risk levels (KarstALEA zones).The KarstALEA Method is a scientific based karst risk assessment for engineering it treats the karst related hazards, investigations and remediation in an appropriatemanner for each construction phase. The applicability and efficiency of the method was demonstrated by back analysis ofcase studies. This presentation outlines the concept and applicability of the KarstALEA method and shows that the KarstALEA method is an efficient, adequate and applicableinvestigation method for karst related hazards.

کلیدواژه ها:

Dam construction and remediation in karst areas ، Prediction of karst occurrences ، Understanding karst network