Abstract
In this paper, the field monitoring method is used to study the variation of rock mass pressure during the construction of a tunnel in phyllite stratum, and three functions are used to fit and analyze the variation of rock mass pressure with deformation, excavation time, and space. The results show the following (1) When the deformation increases significantly, the rock mass pressure decreases firstly and then increases. This is caused by the insufficient bearing capacity of the rock mass in the arch foot of the supporting structure after the excavation of the upper bench, which leads to a settlement of supporting structure and surrounding rock. (2) Compared with other kinds of fitting functions, the logistic function can better characterize the variation of the pressure of surrounding rock with deformation, excavation time, and distance from the face. This paper provides a reliable reference for the design and construction of the tunnel in phyllite stratum. The logistic function can be used to present and predict the change of rock mass pressure with deformation, excavation time, and space in similar rock mass conditions.
Highlights
Rock mass pressure is the pressure acting on supporting structure, and it is caused by deformation or loosening of the surrounding rock after a tunnel is excavated
(2) Compared with other kinds of fitting functions, the logistic function can better characterize the variation of the pressure of surrounding rock with deformation, excavation time, and distance from the face. is paper provides a reliable reference for the design and construction of the tunnel in phyllite stratum. e logistic function can be used to present and predict the change of rock mass pressure with deformation, excavation time, and space in similar rock mass conditions
Considering the above factors, the fitting trend of logistic function with a higher correlation coefficient is more consistent with the measured data, and it has the minimum fluctuation of the constant range in characterizing the variation of rock mass pressure with deformation
Summary
Rock mass pressure is the pressure acting on supporting structure, and it is caused by deformation or loosening of the surrounding rock after a tunnel is excavated. The changing pattern of rock mass pressure during tunnel construction has been studied by analytical method, numerical simulation, onsite monitoring, and laboratory model tests [4,5,6,7,8,9,10,11,12]. Chen et al studied the change of rock mass pressure during the construction of soft rock tunnel through the combination of field monitoring and numerical simulation and found that the surrounding rock pressure was stable 65 to 70 days after the completion of support structure [20]. Based on the monitoring of the Mingyazi tunnel, this study analyzes the variation of rock mass pressure with the deformation, time, and distance from excavation face during the construction process of the phyllite tunnel and summarizes a changing pattern.
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