Hydraulic deterioration of geosynthetic filter drainage system in tunnels – its impact on structural performance of tunnel linings

Abstract

This paper presents the results of an investigation into the effect of decrease in drainage capacity by hydraulic deterioration of tunnel geosynthetic drainage systems on the structural performance of tunnel linings. The use of geosynthetics in tunnel construction is first introduced together with a summary of geotextile filter design principles and practices. A series of stress–pore-pressure-coupled finite-element (FE) analyses were then carried out on a number of tunnel cases in order to investigate the effect of hydraulic deterioration of the tunnel drainage layer on the structural performance of tunnel linings. It is shown that the decrease in drainage capacity of the drainage layer significantly increases the axial thrust and bending moment of the tunnel lining, with more pronounced increases in the bending moment. It is also revealed that hydraulic deterioration-induced lining forces tend to increase with the hydraulic head and slightly decrease with the cover depth. It is also shown that the progressive development of hydraulic deterioration-induced lining forces can be best fit with an exponential function which can be used to predict the lining force increase for a given tunnel condition. Practical implications of the findings are discussed.