Evaluation of Face Support Pressure Prediction for Earth Pressure Balance (EPB) Tunnelling using Analytical and 3-Dimensional Finite Element Modelling

Abstract

A shield tunnelling technique is usually selected using earth pressure balance or slurry methods for tunnel construction in urban areas with soft and saturated ground. Although shield tunnelling has many advantages, incorrect determination of face pressure could cause ground surface settlement or lifting during tunnel construction. Numerous approaches for determining face support pressure have been published internationally, but a suitability evaluation based on local ground conditions in Indonesia has not been conducted yet. The completion of Mass Rapid Transit Jakarta (MRTJ) tunnel construction project using the earth pressure balance method, along with its adequate data, has become a sample case of the effectiveness of each method to determine face support pressure. The study discussed in this paper aimed to determine the linear relationship between the calculated value and the actual measurement of face support pressure and to identify which method most closely represents the actual condition according to the MRTJ case study. An analytical approach using the limit equilibrium method and the numerical approach using Plaxis 3D were conducted, followed by statistical evaluation in the terms of coefficient of variation. The result shows that the limit equilibrium method is effective in predicting the mean value face support pressure and the upper and lower perimeters for tunnel construction, while the overall face support pressure result using the shell model of the finite element method are lower than the actual measured values. The result probably indicates the balance state condition at the tunnel face, and the additional 80 kPa after the second phase of excavation could indicate the need for greater pressure for tunnel boring machine movement.

Keywords

• face support pressure
• finite element method
• mass rapid transit
• tunnels