ANALYSIS OF PIPE-SOIL INTERACTION FOR

ANALYSIS OF PIPE-SOIL INTERACTION FOR

A MINIATURE PIPEJACKING

K. J. Shou * F. W. Chang **

Department of Civil Engineering

National Chung-Hsing University

Taichung, Taiwan 40227, R.O.C.

ABSTRACT

In this study, physical and numerical models were used to analyze pipe-soil interaction during pipe-jacking work. After calibrating with the physical modeling results, the finite element software ABAQUS [1] was used to study the pipejacking related behavior, such as surface subsidence, failure mechanism, pipe-soil interaction, etc. The results show that the driving force in the tunnelling face is very important and critical for pipejacking. Surface subsidence is mainly due to the lack of driving force, however, ex-cessive driving force could cause the unfavorable surface heaving problem. It also suggests that the depth of the pipe is critical to determine a proper driving force to stabilize the tunnelling face.

Keywords : Pipejacking, Pipe-soil interaction, Finite element analysis, Physical modeling, Trenchless construction, Underground excavation, Geotechnical engineering.

1. INTRODUCTION

Pipeline construction, either new-installation or re-newals, is one of the major construction works during development of an urban area. Traditional trench ex-cavating method has advantages, such as easy working and low construction cost, however, it has strong impact not only on the environment but also on the traffic of the construction area. Therefore, trenchless construction methods were developed and applied to avoid those difficulties. In recent years, due to the rapid develop-ment of the Taiwan area, there are more and more trenchless pipejacking constructions. However, diffi-culties are frequently encountered due to poorly under-standing the pipe-soil interaction behaviour.

Due to the uncertainty of geological conditions and the complexity of construction processes, most of geo- technical engineering works are difficult to analyze. Physical and numerical models provide us alternatives to investigate those complicated geotechnical engi-neer-ing problems. In this study, three-dimensional physi-cal model and numerical model were established and applied to simulate real pipejacking systems.

The objective of the study is focused on the behavior of the soil-pipe interaction of pipejacking, to investigate and countermeasure the difficulties during pipejacking construction. In this study, physical and numerical models were adopted for the analyses. After calibra-tion and comparison was made with three-dimensional physical modeling results. The finite element software ABAQUS was also used to study the pipejacking related behavior.

In the three-dimensional pipejacking simulation, ac-cording to the laboratory works, the extended Drucker- Prager model is adopted. As part of the calibration, we analyzed the behavior of two typical geomaterials under the pipejacking process and compare the numerical re-sults with those from physical modeling and theoretical model. Then, a series of analyses were performed fo-cusing on surface subsidence, failure mechanism, and pipe-soil interactions. Based on the numerical results, suggestions are given for future pipejacking works.

2. PHYSICAL MODELING

Based on reasonable assumptions, analytical, physi-cal and numerical models provide us alternatives to in-vestigate complicated engineering problems. Analyti-cal models can mathematically simulate engineering problems and obtain accurately results. But their ap-plicability is very limited as their mathematical formu-lations are based on restricted geometry or boundary conditions only. On the contrary, physical model and numerical model can more practically simulate engi-neering problems, as their assumptions can be more flexible.

In this study, a three-dimensional physical model was

*Professor **Graduate student