Transient Seepage Analysis of Qingyuan Power Station Underground Caverns and Drainage Hole Arrays with Excavation Process

Abstract

The disasters caused by groundwater during underground cavern excavation, are inevitable and difficult to predict. In this study, transient seepage analysis was performed during the excavation of Qingyuan power station's underground caverns and drainage hole arrays. The drainage hole arrays around the caverns were simulated using a new method, and the groundwater surface during transient seepage analysis was confirmed with the hydraulic conductivity adjustment method, by using ABAQUS user subroutines USDFLD and GETVRM. By simplifying the drainage hole into face geometry, the proposed drainage hole simulation method could reach the accuracy of the widely used substructure method with half nodes of the computational boundary, and reflect the influence of drainage hole diameter on seepage analysis results. Moreover, a sensibility analysis of the diameter and space of drainage hole arrays could be conducted using one simulation model with the proposed finite element mesh type. Transient seepage analysis showed the evolutions of the groundwater level, flow rate and maximum hydraulic gradient of drainage holes and underground caverns, during the construction of Qingyuan power station. Such results could provide a reference for the creation of design and construction schemes. The previous excavation of the drainage hole arrays could control the seepage field, and reduce the flow rate and maximum hydraulic gradient of the underground caverns. This study may provide valuable reference to the design and construction of similar projects.