CHEN Lijie, ZHANG Xiaoping, LIU Huabin, HAN Gengyou. 2010: SETTLEMENT CHARACTERISTICS OF TUNNEL EXCAVATION AT SHALLOW DEPTH IN SOFT ROCK AND COUNTERMEASURES. JOURNAL OF ENGINEERING GEOLOGY, 18(2): 281.
    Citation: CHEN Lijie, ZHANG Xiaoping, LIU Huabin, HAN Gengyou. 2010: SETTLEMENT CHARACTERISTICS OF TUNNEL EXCAVATION AT SHALLOW DEPTH IN SOFT ROCK AND COUNTERMEASURES. JOURNAL OF ENGINEERING GEOLOGY, 18(2): 281.

    SETTLEMENT CHARACTERISTICS OF TUNNEL EXCAVATION AT SHALLOW DEPTH IN SOFT ROCK AND COUNTERMEASURES

    • The control of settlementdeformation of shallow tunnel in soft rock during operation is a difficult task. The most basic content is to master the law of settlementdeformation induced by excavation. This paper presents the observation and analysis of the surface subsidence deformation at Longyan railway tunnel. The deformation of surface subsidence versus time is divided into three main phases: the initial settlement stage,the accelerated settlement stage and the decelerated settlement stage. Combining the results of sedimentation monitoring of the tunnel vault,the positive correlation of surface subsidence and sedimentation of the tunnel vault is concluded. The influenced ranges of the tunnel excavation in front of and behind of the work face are 15D and 3D respectively,where D is the tunnel span. The influenced ranges of traverse are 4D in both sides of the center line. The influenced ranges of the structures are 2D in both sides of the center line. Due to large ground and vault settlements were predicted,a whole section pregrouting was adopted to prevent the large settlements. Monitoring results indicate that the whole section pregrouting can reduce the ground and vault settlements effectively. Convergence reduction is not markable. The scheme achieved the aim of settlement reduction.
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