| In recent years,in order to meet the special conditions of geological conditions and line requirements in some areas,a new type of tunnel-small cross-over tunnel has emerged.Using a small clear distance cross-tunneling scheme has significant economic,and also does benefit to social and environment.However,a series of construction problems caused by small clear-distance tunnels and the influence of cross tunnels have aroused people's attention.It is of great practical significance to formulate and adopt reasonable construction measures to ensure the stability of adjacent tunnels.In this paper,the blasting vibration of the construction of the small clear distance cross-section tunnel is systematically studied by relying on the newly constructed Beijing-Zhangjiakou railway tunnel near Beijing-Zhangjiakou Railway.In order to provide the necessary theoretical and technical skills for the newly-built Beijing-Zhangjiakou Railway to go through the Tang-Zhang Railway,and to ensure the operational safety of the Tang-Zhang Railway Tunnel,a reference for the construction of similar tunnels is provided.The main research contents and achievements of this paper are as follows:(1)A test section was selected to carry out blasting vibration test where the geological conditions was similar to the cross-section.According to the on-site monitoring data,the law of propagation attenuation of blasting vibration wave is obtained,and the formula of blasting vibration attenuation sui Tab.for this project is obtained.The monitoring point of blasting is determined to be ±30 m at the intersection point,and the maximum blasting dose in single stage should not exceed 4.97 kg.(2)To obtain the blasting vibration spectrum curve,the fast Fourier was used to transform the monitoring data.It is found that the main frequency range of blasting vibration is in the range of 10 Hz-115 Hz,which is higher than the natural frequency of buildings(structures),but the protective measures for the structures which near the construction area shuoud be taken.(3)Numerical simulation results showed that,in order to ensure the construction progress of the new tunnel as much as possible,a 2 m footage construction scheme can be adopted 20 m away from the crossing point.While a 1 m footage construction program can used when entering the 20 m away from the crossing point.Compared with the measured construction monitoring data,numerical results are larger and partial to safe.(4)When the new tunnel and the existing tunnel edge begin to cross the 30 m position,a 2m footage construction scheme should be adopted.When the distance between the new tunnel and the existing tunnel is within 30 m from the crossing point,a 1m footage construction scheme should be adopted instead of the previous step Slot and Expansion Blasting is divided into two sides(?,?)detonated twice to control the single hole on both sides of the cut section of the dose of 0.8 kg,cut section of a single section of the maximum dose of 3.2 kg(5)Through optical fiber communication,setting up an automated monitoring system.Throughout the construction monitoring process found that the maximum vibration speed of 2.004 cm/s,less than the control standard value.It has showed that the improved blasting parameters and blasting schemes can meet the safety requirements in practical construction and the structure is safe and reliable. |
PDF Full Text Request