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Analysis of Vibration Velocity Maximum of the Linging of Existing Tunnel by the Blasting of the Tunnel Near-by

Author: ZhangChengHong
Tutor: LiDeWu
School: Lanzhou Jiaotong University
Course: Bridge and Tunnel Engineering
Keywords: Blasting vibration Threshold analysis Dynamic finite element Close neighbors tunnel Lining Country rock
CLC: U455.6
Type: Master's thesis
Year: 2009
Downloads: 340
Quote: 8
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Abstract

New tunnel blasting excavation may cause adjacent to the existing tunnel injury risk in the case of relatively small pitch with the existing tunnel blasting and excavation of the new tunnel, blasting seismic waves generated by the excavation would endanger the existing tunnel surrounding rock and lining The security and stability of the structure. In this paper, the new Kulutage Tunnel as the background, using the finite element method, MIDAS / GTS software for both the tunnel by the construction of new tunnels blasting a two-dimensional and three-dimensional numerical analysis in different footage, whether the case of the pilot tunnel, a new tunnel blasting existing tunnel deformation velocity, stress. Firstly, the value of the existing tunnel near the tunnel blasting impact and safety assessment of existing tunnel, the research status at home and abroad, old and new research methods to compare the detailed generalization and elaboration. By consulting the relevant literature, a more systematic introduction to rock blasting damage theory and the theory of stress wave, finite element calculation and analysis methods of processing power for blasting vibration simulation, boundary conditions, nonlinear analysis, and solving a series of problems discussed. Destruction theory, rock blasting stress wave theory and dynamic finite element method based on analysis of transient dynamics through MIDAS / GTS nearby blasting construction of the existing tunnel impact of two-dimensional and three-dimensional numerical different conditions simulation analysis, which mainly consider the level III rock conditions under different blasting footage, the guide hole and no pilot tunnel segment, the new tunnel blasting the existing tunnel deformation velocity, the impact of stress and strain. Major analysis of the existing tunnel lining and the surrounding rock under the influence of neighboring blasting vibration velocity, stress, strain, lining deformation and various situations calculation results are compared and analyzed, the following conclusions. (1) a new tunnel blasting vibration effect, the existing tunnel waist to welcome burst side wall the maximum sidewall lining of vibration velocity and displacement within the scope of the arch of the foot, a higher sensitivity to changes in blasting footage arch ring and the wall below the waist area vibration velocity and displacement is relatively small: the lining of the existing tunnel Ying burst side arch back to the dome, skirting to the bottom plate part of the first principal stress, higher sensitivity to changes in blasting footage, the side walls of the first principal stress small, which is the vibration velocity and displacement distribution is just the opposite. (2) from the blasting vibration response along the existing tunnel vertical distribution, and blasting a source close to the cross-section lining vibration speed, otherwise smaller vertical distribution along the existing tunnel velocity curve, the maximum displacement curve maximum tensile stress curve is essentially symmetrical about the center section (parallel to the existing tunnel blasting tunnel face cross-section). Maximum velocity zone is mainly distributed in the range of 5 meters before and after the cross-section of the center, the maximum deformation zone is mainly distributed in the range of 8 meters before and after the central cross section, the maximum stress zone is mainly distributed in the range of 5 meters before and after the central cross section. (3) both the peak vibration velocity of tunnel lining are mainly concentrated in the first four paragraphs, and the more the number of segments on the slower the vibration damping. Therefore, in order to reduce the maximum blasting vibration velocity response to the first four paragraphs of blasting control. (4) blasting footage of the same, the pilot tunnel conditions after the new tunnel blasting existing tunnel welcome critical side of the lining of the response (vibration velocity, displacement, strain, stress) than under the conditions of the pilot tunnel blasting is much smaller. This shows that the new tunnel blasting blasting vibration the folder system conditions by blasting free face constraints. Blasting on face clip system conditions the smaller (if the pilot tunnel), adjacent to the existing tunnel blasting vibration caused the smaller. (5) new tunnel blasting, 2.0 m, 2.5 m, 3.0 m, 3.5 m, 4.0 m blasting footage of blasting vibration of the condition of two-dimensional and three-dimensional elastic-plastic finite element numerical simulation analysis obtained in the absence of pilot tunnel blasting under the conditions existing tunnel lining vibration velocity threshold of 10.7 cm / s, the threshold of the existing tunnel lining in the pilot tunnel conditions blasting vibration velocity is 11.1 cm / s.

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