Abstract:  To determine the construction timing of secondary lining in a squeezing rock tunnel and to operate the secondary lining construction flexibly, the deformation measurement data of 412 squeezing rock tunnel cross-sections are fitted and statistically analyzed based on the deformation rate limit. Consequently, the deformation stabilization time range of various deformation levels and the prediction method of construction timing of staged secondary lining are obtained. Some specific conclusions are drawn as follows: (1) A prediction method of deformation stabilization time based on deformation rate is proposed; a prediction method of deformation amountus and final stabilization time [WT《TNR#I》]t[WT《TNR》]′s in a stable stage is obtained by fitting the optimal exponential function curve. (2) The range of deformation stabilization time [WT《TNR#I》]t[WT《TNR》]′s under various deformation levels and spans is determined through statistical analysis, which can be used to preliminarily determine the construction timing of secondary lining in the design stage. (3) A phased prediction method for the construction timing of secondary lining during construction is proposed; the final deformation stabilization time can be predicted by stages according to the measured relative deformation at 20, 30, and 40 days and stable time. (4) The measured deformation data validate the feasibility of the proposed phased prediction method. (5) The proposed phased prediction method avoids operation trouble by considering the deformation rate as the judgment index and can be directly used in engineering practice.

Key words:  squeezing rock; railway tunnel, construction timing of secondary lining, deformation classification, deformation stabilization time