The development of modern cities has often led to increased traffic congestion and limited usable space. One effective solution to these problems is to construct roadway tunnels, which can expand urban space and alleviate traffic congestion. However, building large underpass tunnels in urban areas, especially in soft ground, presents technical challenges owing to its extensive environmental disturbance. The pipe-umbrella box jacking method offers a promising solution to these challenges as this method does not require breaking the ground from the surface or disrupting surface traffic. This study reviews the key techniques of the pipe-umbrella box jacking method for constructing large rectangular tunnels with small burial depths in soft ground. The study focuses on three main technical issues: pipe umbrella installation, soil face excavation, and box jacking control. Furthermore, two tunnel projects in Shanghai, China, are presented as case studies to showcase the construction challenges and countermeasures during box jacking tunneling with pipe-umbrella. Practical construction experience has revealed that the installation of the pipe umbrella before box jacking serves as an effective method of ground pre-support. However, its performance can be influenced by factors such as pipe installation deviation and inter-pipe connection design. Both open-face steel grid extrusion (SGE) shields and closed-face earth pressure balanced (EPB) shields can be used for soil excavation during box jacking, with different work modes resulting in distinct ground deformation patterns. Additionally, lubrication grouting has been found to effectively reduce friction resistance and affect vertical ground deformation. The study also examines the lessons learned from case studies and proposes optimization measures. This study can serve as a valuable reference for the tunneling industry, providing insights into the pipe-umbrella box jacking method and its application in constructing large rectangular tunnels in soft ground.@en

Backfill grouting plays a vital role in shield tunneling. This paper aims to present a comprehensive review of the development and progress of backfill grouting materials specifically designed for shield tunneling. Initially, the various components of grouts, such as pozzolanic materials, filling fine aggregates, and chemical additives, are introduced and discussed in detail. Subsequently, this study investigates critical properties including workability, mechanical properties, and durability of the grouts. Additionally, the principal factors influencing the properties are summarized, along with recommended ranges for specific geological conditions. Furthermore, the paper elucidates the diffusion mechanism of grouting mortars by presenting the current grouting models employed in shield tunneling. Recent advancements in grouting materials are extensively studied and extended, offering new perspectives for future grouting technology in shield tunneling. This study provides valuable insights into overcoming the existing challenges associated with shield tunnel grouting and promoting the evolution of current grouting materials.

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Pipe jacking has been the dominant trenchless technology for constructing small (\2 m) to medium-diameter (\4 m) tunnels. Uncertainties and construction difficulties increase significantly when the diameter of the tunnel exceeds 4 m. This paper presents a case study of the largest concrete pipe-jacking tunnel project in the world, the sewerage tunnel along Jinshan Lake, Zhenjiang, China. In this project, an underwater tunnel with a diameter of 4.67 m was constructed by the earth pressure balance (EPB) pipe-jacking method. The case study reports project background, and geological and hydrogeology conditions. The key techniques such as the selection of pipe-jacking machine, jacking force estimation and control, design of intermediate jacking station, grouting process control, launching, and reception of the tunnel boring machine, trajectory control of pipe jacking, and ventilation and gas monitoring during the construction period were investigated and discussed. Furthermore, to overcome the technical difficulties associated with the oversized jacked tunnel, the corresponding countermeasures were adopted point by point, so that the safety of the whole project could be guaranteed. This study filled the knowledge gap of technical know-how for large-diameter (over 4.5 m) pipe-jacking tunnel and is expected to provide practical guide for future large-diameter pipe-jacking tunnels.

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With the acceleration of urbanisation in China, land shortage has become a severe problem in metropolises. As the medium and shallow underground space in central urban areas has been developed to a matured or even saturated extent, development of deep underground space (DUS) becomes inevitable. Based on the DUS utilisation planning in Shanghai, the depth classification and the conceptual model of DUS utilisation are discussed. Furthermore, deep geological conditions in Shanghai are described and the corresponding impact on deep foundation pit engineering and shield tunneling are analysed. Finally, a deep sewage tunnel system under construction in Shanghai is introduced as a case study.

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