| Domestic basic transportation construction and resource extraction are developing towards deep stratum,and engineering geological conditions are getting worse and worse.The problem of large deformation in surrounding rock caverns cannot be ignored.The exploitation of resources and the construction of basic transportation gradually develop to the deep underground.Therefore,the excavation process of the tunnel will inevitably disturb the mechanical balance of the original geology.Geological disasters such as spalling,collapsing and rock bursting will also occur more and more frequently.As an economical and practical support technology,bolts have been available for more than 100 years,among which the traditional bolt is difficult to meet the support needs of large deformation tunnel due to its high rigidity and low ductility.Therefore,it is necessary to develop a new type of bolt,which can provide stable support force and release the accumulated energy in the surrounding rock by displacement sliding under the condition of large deformation and failure of surrounding rock cavern.At the same time,in order to ensure the safe construction and follow-up use of surrounding rock cavern,the new anchor bolt is also required to have the function of monitoring and early warning of surrounding rock displacement.The main purpose of this paper is to analyze the mechanical properties of the large deformed self-adaption release energy bolt developed by the scientific research team of Professor Zhou Xiaoping of Chongqing University,using numerical simulation and indoor static tensile test to analyze its mechanical properties and verify the rationality of its stress state,so as to choose the optimal structure size.Through the numerical analysis method,the dynamic impact analysis is carried out,the bearing capacity and deformation characteristics under different dynamic impact speeds are studied.Based on the analysis of the geometric parameters of the bolt,the mechanical characteristics of the large deformation self-adaptive energy release bolt under different rod friction head diameter and different sleeve thickness are studied.Finally,we combined the early warning device and bolt as a set of surrounding rock deformation early warning system for field test in a tunnel project,and obtained the deformation characteristics of bolt under the field test,further verifying the prospect of its engineering early warning application.Through the above research,compared with traditional bolts,large deformed self-adaption release energy bolts show better mechanical deformation characteristics,innovative early warning functions,and better control of nonlinear large deformation failure of surrounding rock cavern.Innovation in this article:(1)In the structural design,the sleeve is used as a part of the bearing body,and the sliding of the bar body plays a role in the deformation energy release.This structure simplifies a series of processes such as the production,use and installation of bolts.(2)Based on a tunnel excavation project,the in-situ experimental research on the early warning function of the surrounding rock deformation of bolt was carried out.The experimental results were theoretically studied and analyzed,and the result show that the large deformed self-adaption release energy bolts are feasible and effective as early warning tools.(3)Make full use of the tensile strength of the material,so that the large deformed self-adaption release energy bolt has a tensile strength similar to that of traditional bolts in the process of maintaining deformation and energy release.(4)Finite element numerical analysis is a low-cost,fast and efficient experimental method.Few cases use the finite element analysis method to study the dynamic characteristics of new bolts.Based on ANSYS / LS-DYNA finite element numerical analysis software,the author of this paper carried out a dynamic analysis of the large deformed self-adaption release energy bolt.The research results can provide guidance for subsequent related tests. |
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