Abstract:

The backfill grouting time of hollow behind primary support of tunnel on ChengduKunming Doubletrack Railway of Xigeda Formation and the reserved deformation need to be cleared. As a result, the deformation law of tunnel surrounding rock and primary support and reserved deformation in Xigeda Formation are further studied by site monitoring and statistical analysis method. The study results show that: 1) There is initial gaps between surrounding rock and primary support after top heading excavation; the differential settlement between surrounding rock and primary support of tunnel crown top is 1-2 mm; as a result of geological conditions, tunnel buried depth and construction conditions, middle bench excavation induced tunnel collapse should be paid attention to and backfill grouting should be carried out for hollow behind arch primary support before middle bench excavation. 2) The reserved deformation can be appropriately adjusted based on construction situation of tunnel face; the reserved deformation should be 24-30 mm when the shale takes the main component of Xigeda Formation, and that should be 118-123 mm when the sandstone takes the main component of Xigeda Formation.

Key words: Xigeda Formation, tunnel surrounding rock, primary support, differential settlement, backfill grouting, reserved deformation