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Civil engineering difficulties in the karst of China

Karst landscapes, developed by solutional erosion of massive limestones, are characterized by underground drainage and the development of closed depressions. In tropical areas, with high solution rates, long uninterrupted periods of erosion and a lack of glacial planation, the expansion and deepening of these closed depressions creates a rugged relief dominated by either conical hills or steeper-sided towers. The form of the cones and towers is a function of both the carbonate lithology and the erosional history; the towers develop only in massive, mechanically strong, compact limestones where erosional planation and tectonic uplift have kept pace over a long period of time (Smart et al 1986). These karst landscapes are characteristic of huge areas of southern China, largely in the provinces of Guangxi and Guizhou (Fig. 1) and the spectacular scenery of the limestone has often been represented in classical Chinese painting. They are now also becoming a major tourist attraction, with Guilin, in Guangxi, frequently visited by Westerners. These terrains do, however, pose serious difficulties to the civil engineer. Where relief is not great, or where rates of uplift have been low, corridors of flatter ground have often been created by lateral planation at the water table. These corridors may be lithologically or structurally controlled, and form obvious routes through the karst. Where the relief is higher and the regional water table is not intersected, coalescence of the depressions to form flatter ground is rare, and road and rail development is more problematic. In order to avoid excessive and