Abstract: Combined with the example of a deep excavation of a comprehensive utility tunnel, this paper introduces in detail the general conditions, surrounding environment, engineering geological and hydrogeological conditions of the foundation excavation at the intersection section of the utility tunnel and three existing pipelines. To ensure the stability of the soil on the side walls of the deep excavation and the safety of pipelines when the deep excavation of the utility tunnel crosses a large-diameter pipe group, the support measures of bored cast-in-place piles + internal supports + Metro Jet System (MJS) sidewall soil reinforcement + MJS bottom sealing are adopted for this section of the deep excavation. This paper systematically introduces the design ideas, design contents, construction process flows and construction requirements of the support options. The implementation of the project and the monitoring results show that by adopting this support plan, the safety of the deep excavation of the utility tunnel and the normal operation of the existing pipelines can be ensured, the technical problem that it is difficult to close the support structure when a large-diameter pipe group crosses the deep excavation of the utility tunnel can be solved. Compared with the option of rectangular pipe jacking crossing existing pipelines, the support plan shortens the construction period, saves costs and has good social and economic benefits.

Key words: Metro Jet System (MJS) Construction Method, Large-Diameter Pipe Groups, Crossing Pipe Gallery, Deep Excavation Support