Behavior of Overdeformed Shield Tunnel Lining under Grouting Treatment: Field Experiment

Abstract

Shield tunnel structures are commonly found to be over-deformed in Eastern China soft ground due to adjacent engineering activities. Grouting treatment could serve as a viable solution to reduce the excessive diametrical expansion of tunnel linings actively. However, understanding the groutinginduced effects on adjacent tunnel structures remains preliminary due to the scarcity of welldocumented case histories. In this study, a field experiment was conducted to explore a shield metro tunnel's real performance during grouting treatments. An extensive monitoring scheme was deployed while varied geometrical grouting arrangements were carried out. The tests provided a comprehensive database of the tunnel responses in multiple temporal resolution levels, both during the entire course of the grouting treatment and within single grouting operations. Investigations are carried out over the influencing factors of the grouting efficiency. The experimental observations suggest that grouting efficiency tends to evolve with time and can be affected by various geometrical grouting parameters.Observations are also presented and discussed in detail for the influence of grouting history on the convergence distribution and the tunnel's performance after the termination of all grouting operations. Time-variant behaviors of the tunnel are depicted in detail, such as the convergence recovery and rebound during the grouting process. Overall, this case study brings new insights into understanding the grouting-induced tunnel lining response. It can also serve as a benchmark for further theoretical and numerical studies.

Resilience of metro tunnel structures: monitoring deformation due to surrounding engineering activities and effect of remediation treatment

“…This section gives an overview of an example case of a shield metro tunnel that was affected by large-scale excavations in the soft soil area during the redevelopment of a city area in China, which was reported in detail in Han et al [15]. The twin tunnels were put into operation in 2010, and two years later, large excavations took place near the tunnels as part of the construction of 10 highrise towers (total basement area around 90,000 m 2 ).…”

“…A recent study [15] reported a full-scale field experiment of grouting treatment in Eastern China soft ground in connection to a retrofitting operation to reduce the convergence of the tunnels under consideration. The effects of different routing arrangements and grouting history on the grouting efficiency, the timevarying response of the tunnel linings, and the characteristics of the tunnel lining rebounding after grouting, were examined.…”

“…As introduced in Sect. 2, the twin tunnels under consideration incurred significant over-deformation with [15,16] a convergence reaching the order of twice the design serviceability limit in the worst affected region, primarily due to the deep excavation taking place in the close vicinity on both sides of the tunnels. In order to rectify the problem and maintain the safety of the metro lines carried by the tunnels, the metro company decided to resort to grouting treatment with an aim to correct the over deformation of the tunnels back to an acceptable level and to strengthen the resistance of the ground.…”

“…By adjusting the mixture ratio of the sodium silicate and Portland cement, a desirable initial setting time of the grouting slurry can be achieved, avoiding plugging of the injection pipe and ensuring a target diffusion radius of grout in the soil. Further details of the mix ratios, the flow rates and the corresponding initial setting times can be found from Han et al [15].…”

“…12 Correlation between convergence recovery and convergence rebound [16] after the grouting operations. It should be noted that the convergence time histories are the accumulated convergence results over the whole set of grouting operations, with each data point corresponding to a particular stage of staggered grouting scheme (for details see [15]. Several observations may be made from the graphs, as summarised below: i) the maximum recovery convergence at the time of completion of all 10 grouting operations ranged from 15.6 to 20.9 mm, with an average at about 19.1 mm.…”