Impact of Horizontal Soil Strains on Sewer Manholes and Pipelines within Mining Areas

Abstract

The main purpose of the paper is to assess and compare the values of horizontal soil unit loads, acting on the construction of sewer manholes and pipelines within mining areas. The examples of failures of these building objects buried within mining areas are also presented. Flexible (e.g. thermoplastics) and rigid (e.g. concrete, reinforced concrete) objects are taken into account. The impact of mining extraction on sewer manholes and pipelines is mainly manifested by horizontal strains. Soil strains lead to additional loads acting on the construction of the objects, which are buried in the subsurface soil layer, during horizontal soil compaction and loosening. The horizontal strain in the subsurface soil layer within mining areas causes both considerable value changes in horizontal loads acting on the object walls and significant uneven load distribution in comparison to non-mining areas. It should be emphasised that these strains pose a threat to building objects, especially, during horizontal soil compaction. In the case of sewer manholes and pipelines, it is a reason for their failures and a lack of tightness, and changes in the cross-section shape of flexible objects. In the case of flexible manholes and pipelines made of thermoplastics, a deflection of construction elements can occur. The deflection of the elements should be limited to ensure the functionality of manholes. The additional loads should be considered when determining the foundation conditions of sewer manholes and pipelines within mining areas in order to aid their design, protection and resistance assessment to horizontal soil strains. The load values were determined for horizontal soil compaction and loosening caused by horizontal soil strains. For load determination in the case of flexible sewer manholes and pipelines, experimental test results were taken into account. The values of the determined external horizontal soil unit loads acting on the flexible and rigid object walls during horizontal soil compaction within mining areas vary a lot. The uneven distribution of horizontal soil loads is lower for flexible objects than rigid ones buried in the same soil conditions within mining areas. The differences between the values of horizontal soil unit loads, acting on the construction of flexible and rigid sewer manholes as well as pipelines, are also caused by the interaction between soil and these objects within mining areas.