Influence of location of subsurface structures on development of underground cavities induced by internal erosion

This paper revealed the influence of buried structures on the development of underground cavities with internal erosion from the breakage of sewer pipes, and investigated the spatial distribution of a loose ground where the strength was decreased due to this erosion. Moreover, the collapse of the underground cavities induced sinkhole accidents. A series of laboratory model tests was conducted to examine the relevance of the locations of subsurface structures and the expansion of underground cavities. Following the model tests, the strength of the model ground was examined by means of a series of laboratory penetration tests. The results of these laboratory tests showed that the subsurface structures brought about a variation in the formation of cavities as a result of a variation in the pathway of localized seepage that had developed throughout the nearest path from the surface to the cracks in the pipes. In addition, this paper found that developments in the loose ground were induced without the accompaniment of visible deformation. A large-scale model test indicated the applicability of the results of the laboratory model tests to the practical scale of the ground. Overall, we proposed the necessity of considering the mutual effect of subsurface structures on the progression of cavity expansion due to internal erosion.