Dissolution Features of Karst Foundations at Different Depth Sections

Abstract

The dissolution of karst foundations can be divided into rock surface dissolution and hole dissolution. The dissolution features of karst foundations at different depths must be clearly identified before taking proper karst treatment measures. In this paper, more than 200 engineering data samples are collected from typical carbonate karstic regions in southwestern China, and 12 most representative engineering site were picked out. The rock surface dissolution ratio, hole dissolution ratio, and total dissolution ratio were measured at each engineering site, and used to fit the relationship between rock surface dissolution ratio and hole dissolution ratio at different depth sections. The results show that the karst foundation can be split into three sections from top to bottom: rock surface dissolution section Ⅰ, composite dissolution section Ⅱ, and hole dissolution section Ⅲ. The three sections occur inevitably as the rock surface dissolution occurs naturally from the inside. The dissolution degree decreases exponentially with the growing depth, and the rock surface dissolution ratio drops faster than the total dissolution ratio. Moreover, the hole dissolution ratio per unit volume of rock decreases with the increase of depth. If the holes are not developed, the engineering sites will only have rock surface dissolution section; if the holes become more developed, the composite dissolution section will expand gradually and dominate site dissolution. At most locations, the hole dissolution ratios under the minimum elevation of rock surface are within 10%. Finally, it is suggested that the final elevation of the drilling holes must be controlled above the minimum elevation of rock surface. The research results shed new light on the mitigation of dissolution of karst foundations.