Impact of horizontal soil strain on flexible manhole riser deflection based on laboratory test results

Abstract

Underground mining extraction causes deformation of the rock mass and the surface, which may cause damage to the construction of manholes, thus leading to the failure of the sewage system. To ensure the proper operation of sewer systems in mining areas, it is important to consider the interaction between the manhole and the horizontally strained soil. The impact of continuous mining deformations of the ground around the manhole manifests itself through the impact of horizontal strains, which mainly affect the manhole riser. These strains cause the horizontal cross-sectional deflection of the flexible manhole riser, which is made of thermoplastics.This article presents the results of laboratory (model) tests conducted in conditions similar to in-situ conditions. The aim of these studies was to determine the impact of horizontal strains of the non-cohesive soil on the relative deflection of the horizontal cross-section of the manhole riser, which was made of thermoplastic. The laboratory tests have been performed for manhole riser models with various ring stiffnesses, which are used in practice, and at various manhole foundation depths. The values of the relative cross-sectional deflection of the manhole riser models have been determined for both the horizontal loosening and horizontal compaction of the soil. The research methodology has been presented, and the results of laboratory tests have also been analysed. The horizontal cross-sectional deflection of the flexible manhole riser depends not only on the values of the horizontal soil strain but also on the ring stiffness and the foundation depth of the discussed cross-section of the riser.