Study on'activation'and critical load of the foundation in the mined-out area under a high-speed railway

Gao Baobin; Chen Zhibin; Ren Lianwei; Zou Youfeng; Wang Xin; Zhu Hongbo; Ren Chuangnan

doi:10.16186/j.cnki.1673-9787.2023090030

Abstract：Objectives This study aims to reasonably predict the threshold at which the dynamic load of high-speed trains may cause'activation'of the foundation in mined-out areas.Methods A combination of theoretical analysis and numerical simulation was employed to systematically investigate the determination of foundation'activation'in mined-out areas beneath high-speed railways,the dynamic loads imposed by trains,and the corresponding calculations of train speed and axle load.Based on the'activation'criteria and dynamic load analysis,a method for calculating the critical load of high-speed railway foundations above mined-out areas was established and applied to engineering practice to obtain the critical load,corre-sponding critical static axle load,and critical train speed.Numerical simulations using MIDAS software were conducted to determine the height of water-conducting fractured zones and the range of critical loads,thereby verifying the feasibility and accuracy of the proposed method and theoretical calculations.Results The results indicate that when a high-speed train passes over a mined-out area,the critical load is 26.60 t.For a designed static axle load is 17 t,the corresponding critical speed is 188.24 km/h;for a designed speed of 250 km/h,the critical static axle load is 15.20 t.When the train operates below the critical load of 26.60 t,the foundation in the mined-out area is unlikely to be'activated'.However,if the train simulta-neously runs at the design speed of 250 km/h and a static axle load of 17 t,the load reaches 29.75 t,ex-ceeding the calculated critical load.In this case,treatment of the mined-out area is necessary to ensure the safety of both the railway and the train.Conclusions The findings provide valuable guidance for the con-struction and treatment schemes of high-speed railway foundations above mined-out areas.