Abstract
In the excavation process of a drilling and blasting tunnel, it takes multiple blasting excavations to form, so it is inevitable to produce multiple blasting impact loads, which will cause certain vibration damage to the surrounding rock-support structure. To solve this problem, based on the attenuation formula of blasting vibration wave and considering the cumulative effect of short footage blasting load, the radial displacement formula of surrounding rock particles is derived, and the analytical solution of vibration velocity field is obtained by using the method of separating variables. Then, taking Cuobuling station of Qingdao Metro as the engineering background, the finite element software is used to simulate the tunnel excavation process under the action of short footage multiple blasting. The vibration damage impact of multiple blasting loads on the surrounding rock-supporting structure is analyzed from the accumulated displacement value and vibration velocity cumulative value of the excavation tunnel. The results show that the damage accumulation effect is produced in the surrounding rock of each section during the blasting construction, among which the accumulation is the largest at the arch bottom. With the increase of blasting times, the damage of the surrounding rock is still accumulating gradually. Compared with the first blasting, the peak value of vibration velocity of the second blasting increased by 114%, and with the increase of blasting times, the variation trend of maximum vibration velocity of the measuring point showed an upward trend, but the subsequent vibration acceleration decreased. Under the condition of grade V surrounding rock, when the thickness of the concrete spray layer is 350 mm, the maximum displacement cumulative value of each measuring point in profile 1-1 is reduced by about 50.4% compared with that without support. According to the displacement nephogram of the concrete spray layer, the displacement of the concrete spray layer accumulates after three times of blasting, which affects the stability of the supporting structure. Finally, an example analysis is carried out and compared with the analytical model results to verify the accuracy of the mechanical model.
Highlights
It is inevitable that the cumulative effect of blasting load on the surrounding rock and initial support structure within a certain range from the blasting face will be produced. is cumulative effect is especially obvious in short footage blasting excavation
Based on the analytical model, the vibration damage of the surrounding rock and initial support structure under short footage blasting load is numerically simulated by using finite element software. e influence law of short footage blasting load on the vibration of the surrounding rock and supporting structure of the tunnel is analyzed, and the results are compared with the analytical model to verify the accuracy of the dynamic response analytical model
In order to analyze the influence of short footage blasting on the surrounding rock and supporting structure of tunnel, the numerical simulation software MIDAS/GTS NX is used to study the stability of the surrounding rock and initial support structure under the influence of short footage blasting vibration, so as to guide and improve the tunnel construction scheme and provide theoretical support for construction safety
Summary
Due to the advantages of high excavation efficiency, strong adaptability to surrounding rock, low economic cost, and relatively mature technology, the drilling-blasting method is still the main construction method in the selection of mountain tunnel construction scheme [1,2,3,4,5]. e blasting vibration produced by the drilling-blasting method will damage the surrounding rock and supporting structure of the tunnel, especially in the process of short footage blasting construction, in which the surrounding rock and supporting structure will be damaged by blasting vibration for many times, and the stability of the surrounding rock and support structure in the construction process plays a decisive role in the safety of drilling and blasting construction. erefore, ensuring the stability of the surrounding rock and supporting structure is the key to the design and construction of short footage blasting tunnels. There is little systematic research on the influence of short footage blasting load on the surrounding rock and support structure vibration. Erefore, this study takes Qingdao Metro blasting excavation as an example; considering the cumulative effect of short footage blasting load, the dynamic response analytical model of surrounding rock under blasting vibration is derived from the two dynamic response parameters of vibration peak value and displacement peak value. Based on the analytical model, the vibration damage of the surrounding rock and initial support structure under short footage blasting load is numerically simulated by using finite element software. E influence law of short footage blasting load on the vibration of the surrounding rock and supporting structure of the tunnel is analyzed, and the results are compared with the analytical model to verify the accuracy of the dynamic response analytical model. Related research can provide theoretical basis and technical guidance for the stability of the subway tunnel surrounding rocksupporting structure under multiple blasting loads with short footage
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
