Weathering mechanism of the Cretaceous argillaceous siltstone caverns, Longyou, China

The Longyou caverns in the Zhejiang province of China were hand dug more than two thousand years ago. Five of these caverns were drained in 1992 and are now a major tourist attraction. Brick red argillaceous siltstones locally mingled with greyish-white flecks are present in the geological sequence in which these caverns have been created. Stress cracks have developed in the roof, walls and pillars and the cavern faces are showing distinct signs of powdering. The paper discusses the nature of the rocks, highlighting the smectititic clay which causes disintegration in the argillaceous siltstones. In addition, in the greyish-white speckled material, dissolution of the calcareous cement results in unbound grains forming on the rock face. The rate of disintegration due to weathering is most pronounced near the openings of the caverns where the effects of the external atmosphere are most marked.