Prediction and safety analysis of additional vertical stress within a shaft wall in an extra-thick alluvium

An alluvium with a sandy aquifer at the bottom, but lacking an effective impermeable layer between the sandy aquifer and bedrock is referred to as a special alluvial stratum. Impacted by the drainage of the aquifer due to mining activities, a shaft wall in this special alluvial stratum will be subject to a downward load by an additional vertical force which must be taken into consideration in the design of the shaft wall. The complexity of interaction between shaft wall and the surrounding walls makes it extremely difficult to determine this additional vertical force. For a particular shaft wall in an extra-thick alluvium and assuming that the friction coefficient between shaft wall and stratum does not change with depth, an analysis of a numerical simulation of the stress within the shaft wall has been carried out. Growth and size of the additional vertical stress have been obtained, based on specific values of the friction coefficient, the modulus of elasticity of the drainage layer and the thickness of the drainage layer. Subsequently, the safety of shaft walls with different structural types was studied and a more suitable structural design, providing an important basis for the design of shaft walls, is promoted.