Our company’s NPT3700 slurry balance shield-jack machine has been successfully applied to the comprehensive renovation power cable project of Tianjin Yanji Road 220kV Substation, completing the full tunneling construction of the southern 3#–2# tunnel section. Featuring dual-function integrated shield and jacking construction capabilities, the equipment perfectly adapts to the project’s special alternating construction technology of pipe jacking and shield tunneling. With stable tunneling performance, precise attitude control and high crossing accuracy throughout the construction, the machine successfully completed tunnel crossing works over complex pipelines and structures, ensuring the safe and steady implementation of the power renovation project.

The Tianjin Yanji Road 220kV Substation power cable renovation project features extremely complex working conditions. The southern 3# to 2# tunnel extends 952 meters in total and adopts a segmented and differentiated construction scheme: the front 496 meters are constructed by pipe jacking, while the rear 456 meters are completed by shield tunneling, placing extremely high requirements on the comprehensive adaptability of construction equipment. The tunnel advances downhill from the high elevation of the 3# launching shaft to the low elevation of the 2# receiving shaft, with a total elevation difference of 3.41 meters, resulting in significant longitudinal gradient changes and great difficulties in tunneling attitude control. In addition, the tunnel route sequentially crosses two power tower foundations, two sewage pipelines and the Nan cao Railway. With densely distributed surrounding pipelines and highly sensitive structures, the project demands strict standards for settlement control and safety protection, constituting the core difficulties of the construction.

Facing the complex working conditions of segmented construction, large gradient fluctuations and intensive crossing of high-risk structures, the NPT3700 slurry balance shield-jack machine demonstrates outstanding working condition adaptability. Integrating dual construction advantages of pipe jacking and shield tunneling, the equipment flexibly switches between jacking and tunneling modes, fully matching the project’s segmented construction process. Equipped with a high-precision slurry pressure balance system and intelligent attitude adjustment system, the machine dynamically optimizes construction parameters according to gradient changes and stratum disturbances. It effectively overcomes technical challenges of long-distance large-height-difference tunneling, accurately controls tunnel alignment and ground settlement, greatly reduces construction risks during crossings over railways, tower foundations and sewage pipelines, and ensures continuous and stable operation under complex geological conditions.

Throughout the construction process, the NPT3700 slurry balance shield-jack machine maintained stable performance and smooth technological switching, fully adapting to the variable working conditions of the 952-meter long-distance tunnel. It successfully completed key construction procedures including alternating high and low gradient tunneling and precise crossing of multiple important structures. The equipment effectively avoided potential construction hazards such as tunneling deviation, settlement and stratum disturbance caused by terrain fluctuations and close-distance structure crossing. The whole construction process remained safe, controllable and quality-compliant, efficiently finishing all segmented pipe jacking and shield tunneling tasks and fully highlighting the unique technical advantages of the integrated shield-jack machine.

The successful completion of the project fully verifies the excellent performance of the NPT3700 slurry balance shield-jack machine in long-distance power tunnel construction, large-gradient tunnel excavation and intensive structure crossing projects. It highlights the core competitiveness of the equipment with integrated shield-jack technology and multi-process adaptability. Furthermore, the project accumulates valuable practical experience for domestic complex power renovation tunnels, segmented variable-process construction and large-gradient crossing works, strongly supporting the upgrading of urban power grids and the high-quality development of urban underground infrastructure.