Evaluation method of development degree based on features of intense dissolution layer

It is common to make errors in the selection of building foundation in karst terrains. The root reason is that the practical difficulty of karst treatment in foundation cannot be reasonably reflected by the existing evaluation of karst development degree. Taking New Terminal of Nanning Wuxu International Airport as an engineering case， this article analyzes the limitation of the existing evaluation indices of karst degree， demonstrates the advanced rationality of using intense dissolution layer’s thickness as the evaluation index of karst degree， and proposes the recommended standard of this evaluation. Results show that the intense dissolution layer， divided by the curve of dissolution ratio depth distribution in a foundation， comprehensively considers the main depth range of dissolution degree of rock surface and the development of cave dissolution， and its distribution characteristics can reflect the depth range of most complex karst foundation. As the evaluation index of karst degree， it is reasonable. Its recommended values are suggested as follows， when the thickness of an intense dissolution layer is less than 3.0 m， more than or equal to 3.0 m and less than 6.0 m ，and more than or equal to 6.0 m， the karst degree can be determined as weak development， medium development and strong development， respectively.