On the genesis of karst in red beds and underground engineer risks analysis

Abstract

Red beds are a series of red or dark-red clastic rocks that have been deposited in continental basins under dry climate conditions since the Mesozoic. Long-term investigation and research have found that karst caves in red beds mainly develop as formations composed of coarse-grained clastic rocks in the periphery of the basin. When combined with the overlying water-rich loose soil, these formations pose a significant risk to underground projects. The present study systematically analyzes several large-scale engineering implementations in the red bed layer, reveals the development characteristics of karst caves in red beds, and discusses the relevant causes (or mechanisms) of karst formation, which include the long-term effects of abundant soluble debris, tectonic fissures, and paleochannel systems. The characteristics of underground engineering methods, such as pile foundations, foundation pits, and underground tunnels, were evaluated to determine the main risks causing ground collapse and structural damage, such as water inrush, mud bursting, and slurry leakage. Risk models for different construction methods were finally established.