Numerical investigation on the mechanical behaviour of karst sinkholes

Abstract

The mechanical behavior of soils overlying weathered bedrock is often a concern when it comes to the risk of sinkhole occurrence. Cavities often form near the interface between cover soil and fissured bedrock, and propagate upwards with internal soil erosion, ultimately resulting in surface collapse known as sinkhole. This paper presents and discusses the mechanical behavior of sinkholes by investigating the stability associated with the size and depth of cavity. Two failure modes considered in this study corresponds to tensile failure and excessive yielding around a subsurface cavity. Numerical modeling with the finite difference (FD) software (FLAC) was employed to determine the stress distributions and deformations around the cavity. The results of numerical analyses were used to quantify the effects of factors affecting sinkholes as bedrock depth, cavity size, overburden thickness, and soil strength. The results also illustrate the yielding behavior, which is related to a cover-subsidence sinkhole with a gradual depression over time but no structural collapse. The analysis result exhibits that the critical overburden thickness of around 25 m that turns the yielding condition from unstable to stable.