Environmental and engineering problems of karst Geology in China

Abstract

Karst terrane is generally regarded as a fragile and vulnerable environment. Its underground drainage system can aggrevate both drought and flood problems; the lack of filtration in an underground conduit makes waste disposal more difficult; and the lack of soil cover in bare karstland can enhance deforestation. Moreover, karst terranes are quite often haunted by a series of engineering problems, such as water gushing into mines or transportation tunnels; leakage from reservoirs; and failure of building foundations. In China, there are more than 200 cases of karst collapse, which include many thousands of individual collapse points. Some of these are paleo and natural collapses, but most of them are modern collapses induced by human activities and they have caused serious damage. Many factors such as geologic structure, overburden thickness and character, lithologic features of karstified rock, and intensity of karstification are related to development and distribution of modern collapses. However, China's karst is mainly developed in pre-Triassic, old phase, hard, compact, carbonate rock. Consequently most modern collapses have occurred only in the overlying soil. So it is understandable that the fluctuation of the water table in the underlying karstified strata plays an important role in the process of collapse. Nevertheless, there are different explanations as to how the groundwater activities can induce collapse.