Research On Mechanism And Application Of Intelligent Sensing Of Roadway Anchored Rock Mass Based On FBG

Due to the complexity of rock mass structure of anchor support engineering and the hysteresis of sensing technology,there is still lack of systematic and reliable understandings on bearing mechanism of anchored rock mass,coupling relationship between surrounding rock and bolt,load transfer in rock mass and failure mechanism of anchored rock mass.In this paper,the sensing method of roadway anchored rock mass based on FBG is studied by means of theoretical analysis,laboratory test,simulation,industrial test.The main working is as follows:(1)On the basis of summarizing and deeply studying on the failure mechanism of anchored rock mass,the theoretical solution of axial tension stress distribution alone bolt in anchorage zone under menanical conditions of elasticity,sliding shear expansion,plastic softening and debonding in the process of failure is constructed.According to the evolution of axial force distribution alone anchor in anchorage zone during the interfacial debonding process,a mechanism for realizing the sensing of interface mechanical state of anchored rock mass based on axial force distribution monitoring in anchorage area is put forward.And the sensing key parameters of anchored rock mass,such as crack development of surrounding rock,deformation of anchor and convergence of surrounding rock surface,are put forward,which provide theoretical support for realizing sensing based on FBG of anchored rock mass.(2)Based on the basic sensing theory of FBG,sensing principles of central wavelength and 3dB bandwidth of FBG is discussed.The modulation characteristics of FBG under uniform strain field and non-uniform strain field are studied by the means of theoretical and simulated analysis.A linear relationship between 3dB bandwidth and strain gradient is determined by comparing modulation characteristics of FBG central wavelength and 3dB bandwidth between equal increasing strain field and non-equal increasing strain field.It is possible to distinguish style of strain field and measure the strain gradient.(3)In order to solve the load transfer problem of surface-bonded FBG,a separate FBG strain transfer coupling model is proposed,which transforms the FBG strain coupling mechanism into an axial symmetric problem in protective coating,plane stress problem in adhesive and semi-plane problem on measured surface.A more accurate analytical solution of FBG axial strain distribution is obtained.Then the influence of the mechanical and geometric characteristics of the pasted structure on the accuracy of the theoretical solution is also discussed.(4)Using the method of arc cutting on cantilever beams,the approximate fitted linear,quadratic and cubic function distribution strain fields are obtained.Modulation characteristics of uniform FBG spectra for different types of non-uniform strain fields are experimentally studied.The sensitivity of the central wavelength drift and 3dB bandwidth to the strain distribution parameters is explored,and realization and measurement of non-uniform strain feild based on the combination of the two factors are verified and determined.(5)In order to solve the limitation of FBG in identifying and measuring strain field of high order function,the reconstruction of strain distribution of FBG under non-uniform strain field modulation is studied.By introducing simulated annealing algorithm,the strain distribution reconstruction model for target spectrum is established,and the optimal decision criterion function is determined.Then the error source and error transfer rule in reconstruction process are analyzed.As a result,the high-order strain distribution function with multi-characteristic parameters is reconstructed,with improving reconstruction accuracy and confidence.(6)Based on the above theoretical research results,aiming at the problems of convergence deformation and anchorage interface perception of anchored rock mass,an FBG grid shape reconstruction method based on discrete curvature array and deflection is proposed.A self-sensing anchor with functions of interface mechanical state perception and deformation reconstruction of anchored rock mass is designed,and a system network model with self-repair function is developed.The system has been successfully applied to the perception practice of anchored rock mass in coal mine roadway,which can provide useful reference for the study of bolt support mechanism and the perception and evaluation of anchored rock mass in site.