长三角最深！南京地铁4号线二期过江隧道顺利贯通

Core Viewpoint - The successful completion of the Nanjing Metro Line 4 Phase II underwater tunnel marks a significant milestone in the construction of urban rail transit, achieving a record depth of 68.58 meters below the Yangtze River surface, enhancing the connectivity of Nanjing's cross-river transit network [1][3]. Group 1: Project Overview - The Nanjing Metro Line 4 Phase II project starts from Zhenzhuquan East Station and runs approximately 10 kilometers, featuring six underground stations [3]. - The underwater tunnel spans 3,062.6 meters and employs a single-tube double-track design, utilizing a large-diameter slurry balance shield tunneling machine with a diameter of 11.64 meters [3][4]. Group 2: Technical Challenges - The construction faced significant challenges, including traversing 2,200 meters of the Yangtze River's middle section, characterized by high water permeability and extreme underwater pressure of nearly 90 meters [4]. - The tunnel had to pass through 13 different geological strata, with the most challenging being a 788-meter section of moderately weathered mudstone, which has a quartz content of 90% and poses risks such as increased tool wear and reduced tunneling efficiency [4]. Group 3: Technological Innovations - The project utilized a custom-designed shield machine, "Xin Zheng Cheng Hao," equipped with advanced systems for pressure balance and high-pressure flushing, enhancing cutting efficiency and tool lifespan [5]. - The application of synchronous double-liquid slurry technology was a first in domestic metro underwater tunnels, effectively controlling the segment uplift to within 5 millimeters and ensuring high-quality tunnel formation with no leakage [6].