Risk assessment and optimization of supporting structure for a new recyclable pipe jacking shaft during excavation process

Abstract

Pipe jacking shaft is an important part of pipe jacking construction, its support structure can support the soil around the pipe jacking shaft to prevent soil destabilization and collapse and ensure construction safety. Most of the existing support structures of pipe jacking shafts are made of cement materials, which have the advantages of high bearing capacity, good integrity and easy access to materials, but also have inherent disadvantages such as high construction cost, long construction period, difficulty in dismantling, and inability to reuse demolition waste, which are not conducive to the sustainable construction. Based on the concept of sustainable construction, this paper proposes a reusable support structure for pipe jacking shafts, which is made of H-shape steel, steel plate and water stop by welding or bolting assembly, easy to install and disassemble, and can be recycled and reused. In order to verify the bearing performance of the new support structure and evaluate the risk of destabilization during excavation, finite element numerical simulation and full-scale test were carried out, and gives the safety design parameters of new supporting structures by using orthogonal tests. The results show that the finite element numerical simulation results are basically consistent with the full-scale test results, further proving that the numerical simulation results can be used to guide the design and construction feasibility of the support structure during the excavation of the pipe jacking shaft. The construction machinery has a great effect on the safety and stability of the support structure during excavation, and the distance between the construction machinery and the pipe jacking shaft should be reasonably controlled to avoid the risk of structural instability. The results of the sensitivity analysis show that the steel type of the support structure and the spacing of the piles are the two most important factors, which play a key role in the safety and stability of the support structure and should be highly noted in the design and calculation process.