Research Of Environmental Influence Induced By Construction Of Rectangular Pipe-jacking

The development and utilization of urban underground space has become increasingly complex. As a kind of trenchless technology, Rectangular pipe-jacking has strength in projects like contact passage, road overpass, utility tunnel with less disturbance and high utility. Nevertheless, the research about rectangular pipe-jacking is still at a fledging period. Based on the project of underground passages between North Huaqiang Station and Huaxin Station in Shenzhen, with methods including theoretical calculation, numerical modeling and measurement analysis, the thesis implemented multi-tier research on the environmental influence induced by construction of rectangular pipe-jacking. Conclusions were made as below:(1) The two-stage method was taken to calculate the upheaval value of shield tunnel caused by upper construction of rectangular pipe-jacking. After calculation of additional load induced by unloading behaviors on the surrounding faces and excavation face using Mindlin theory, Winkler model was then taken to simplify the tunnel. Results acquired by resolving balance equation showed agreement between theoretical values and measured ones.(2) The stochastic medium theory was used to calculate soil surface settlement induced by rectangular pipe-jacking construction, which was then compared with Peck Formula. It turned out that with the increase of pipe depth, the results of Peck Formula came to according with that of stochastic medium theory under uniform convergence condition, while differed from that under non-uniform convergence condition. Compared with observed values, the results calculated by stochastic medium theory under non-uniform convergence condition were closer to practical situation than that of Peck Formula.(3) During the period of construction, Monitoring work in high frequency and large area was done to measure the displacement of ground surface and below existent shield tunnels. Results showed that the influence area of pipe-jacking construction was about 15m～20m wide. Peak Regions appeared when all the construction was done. The upheaval of tunnels mainly increased between the excavation face arrived and left the border of the shield tunnel. The tunnel cross sections in the influenced area was distorted like an egg. Monitoring points on the soil surface went through a process of subside-uplift-subside.(4) Plaxis3D was used to create a 3-dimensinal finite numerical model and the Hardening Soil Model was taken as the soil’s constitutive relationship. Results accorded with filed displacement data. The radius of curvature of underground pipelines and shield tunnels and the displacement of shield tunnels were both in the allowed range. The dynamic advancement was modeled by static steps and the similarities and differences of analogue values and measured values.