• International Journal of Technology (IJTech)
  • Vol 12, No 3 (2021)

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

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

Title: Evaluation of Face Support Pressure Prediction for Earth Pressure Balance (EPB) Tunnelling using Analytical and 3-Dimensional Finite Element Modelling
Fahmi Aldiamar, Masyhur Irsyam, Bigman Hutapea, Endra Susila, Desyanti

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Cite this article as:
Aldiamar, F., Irsyam, M., Hutapea, B., Susila, E., Desyanti, 2021. Evaluation of Face Support Pressure Prediction for Earth Pressure Balance (EPB) Tunnelling using Analytical and 3-Dimensional Finite Element Modelling. International Journal of Technology. Volume 12(3), pp. 485-494

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Fahmi Aldiamar Institute of Road Engineering, Ministry of Public Works, Jl A H Nasution No 264, Bandung 40294, Indonesia
Masyhur Irsyam Bandung Institute of Technology, Jl Ganesa No 10, Bandung 40132, Indonesia
Bigman Hutapea Bandung Institute of Technology, Jl Ganesa No 10, Bandung 40132, Indonesia
Endra Susila Bandung Institute of Technology, Jl Ganesa No 10, Bandung 40132, Indonesia
Desyanti Institute of Road Engineering, Ministry of Public Works, Jl A H Nasution No 264, Bandung 40294, Indonesia
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Abstract
Evaluation of Face Support Pressure Prediction for Earth Pressure Balance (EPB) Tunnelling using Analytical and 3-Dimensional Finite Element Modelling

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.

Face support pressure; Finite element method; Mass rapid transit; Tunnels

Introduction

        In urban areas, tunnel construction through soft and saturated ground requires special caution because unsuitable construction methods can disturb the surrounding infrastructures causing them to collapse. Under such conditions, shield tunnelling is usually selected using the earth pressure balance (EPB) method or slurry method. Both methods reduce the disturbance at the tunnel face and around the excavation area using a tunnel boring machine (TBM). Although shield tunnelling has many advantages, incorrect determination of face pressure could cause ground surface settlement or lifting during tunnel construction. Numerous analytical, empirical, and numerical approaches for determining face pressure have been published in international journals or in technical guidelines, but a suitability evaluation according to local ground conditions in Indonesia has not yet been conducted. The Mass Rapid Transit Jakarta (MRTJ) tunnel construction project was recently completed using the EPB method, and face pressure data according to earth pressure gauges, along with soil profile and the results from in situ and laboratory testing, are available as a sample case demonstrating the effectiveness of the limit equilibrium method and the 3-dimensional (3D) finite element method to determine the 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.

        The EPB method is based on equilibrium between soil pressure and water pressure with jacking force applied on the cutterhead. A screw conveyor has the ability to adjust or control the face pressure during an excavation. For a tunnel constructed below the ground water level, the length of the screw conveyor must be designed to withstand hydrostatic pressure and transform water pressure into atmospheric pressure. An illustration of the EPB machine used in the MRTJ project is shown in Figure 1a, and the position of the pressure gauge instrumentation is shown in Figure 1b. pressure gauges were installed to measure the soil pressure exerted on the cutterhead and to inform the machine operator as to whether the estimated pressures were still safe.