Classification Evaluation Method And Its Application Of Goaf Ground "Activation" For High-Speed Railway

China’s coal production is the highest in the world,a large number of coal resources mining,leaving a large area of goaf sites.With the rapid development of China’s highspeed railway,some key lines will inevitably pass through the goaf site.The activation deformation of goaf foundation has a major safety hazard to the safe operation of highspeed railway.Taking the foundation of mined out area under DK259+135.94-DK259+710.00 line section of taijiao high-speed railway as the engineering background,this paper first introduces in detail the influencing factors of "activation" of high-speed railway mined out area foundation,and on this basis,establishes a unified "activation" classification evaluation model of high-speed railway mined out area foundation,and carries out "activation" classification before and after grouting treatment.Then,MIDAS/GTS NX finite element software is used to analyze the deformation of the goaf foundation of the high-speed railway,and the grouting treatment effect of the goaf foundation in the later stage is simulated.Finally,a pseudo dynamic loading model test device for the goaf foundation of the high-speed railway is developed.The main conclusions are as follows:(1)This paper puts forward the main factors affecting the "activation" of high-speed railway goaf foundation,expounds the interaction mechanism between goaf foundation and high-speed railway subgrade,puts forward the criterion of "activation" of goaf foundation under high-speed railway load,and deduces the maximum influence calculation depth of goaf site under high-speed railway load.(2)Five major factors and nineteen influencing factors affecting the "activation" classification of high-speed railway goaf foundation are determined,and the "activation" classification standard of high-speed railway goaf foundation based on the influence degree of factors is proposed.The evaluation model of "activation" classification of highspeed railway goaf foundation is established by using the basic principles of AHP and fuzzy mathematics.(3)Using MIDAS/GTS NX finite element software,a three-dimensional numerical model of high-speed railway subgrade in goaf site is established.The vibration displacement,vibration speed and vibration acceleration produced by the train dynamic load have obvious consumption effect in the high-speed railway subgrade in goaf area,among which the bottom layer of the subgrade has the largest attenuation effect,and the embankment is the second,the surface layer of the subgrade bed is the smallest;the vibration acceleration produced by the train dynamic load is relatively shallow relative to the vibration displacement and vibration speed.(4)The influence factors of "activation" of high-speed railway goaf foundation are analyzed numerically.With the increase of train axle load,the settlement deformation value of goaf foundation increases;within a certain speed range,with the increase of train speed,the dynamic displacement of high-speed railway goaf subgrade also increases,beyond the speed range,the peak value of dynamic displacement does not change significantly;the cross load of two trains aggravates the deformation of goaf foundation obviously,so it is recommended not to meet trains in goaf foundation.Considering the limitation of numerical simulation in high-speed railway dynamic load simulation,a pseudo dynamic loading model test device for high-speed railway goaf foundation is developed.(58 pictures,27 tables,93 references)...