Developing a Risk Assessment Model for Trenchless Technology: Box Jacking Technique

Abstract

Overcut is required during bore excavation in the box jacking (BJ) technique to facilitate steering of culverts and to reduce friction. BJ is a trenchless construction technique to install rectangular box culverts under existing facilities such as highways and railroads. In this method, box culverts are pushed through the ground using the thrust power of a hydraulic jack. Soil may collapse into the annular space during project execution and cause surface or subsurface settlement. Several investigations have examined this phenomenon in pipe jacking (PJ) and tunneling. Although some aspects of BJ are similar to PJ, there are significant differences between the two methods. The objective of this paper is to investigate surface settlement and determine the associated risk for BJ projects in sandy soil. In this research, finite-element modeling (FEM) software, PLAXIS 2D, was used as the main tool to simulate BJ. Since FEM results are limited to a specific project, artificial neural network and multiple linear regression analysis were adopted in conjunction with PLAXIS 2D to understand the effects of different parameters on determining surface settlements. It was concluded that soil cohesion, box culvert depth from the surface, and overcut size have the highest impact on determining a surface settlement, and their associated risk was determined. The analytical results were validated through two case studies.