The Subgrade Settlement Research Based On The Relative Position Of Goaf Under Highway

As an important part of road transportation, highway plays an irreplaceable role in the national economy rapid development.In the mining industry developed regions, More and more road inevitably need to built across mined-out area. because of its own gravity and traffic load, rock mass overlying the goaf may generate horizontal movement, inclination,subsidence,and other deformation, which may cause cracking of the road surface, roadbed subsidence,or even a large area of subsidence and other damage. This would seriously threaten traffic safety.In order to ensure traffic safety in the mined-out area and reduce economic losses, must evaluate the stability of goaf before the construction of roads in mined-out area. Goaf section of 323 Henan Road is taken as the engineering background in this paper, consider the activity of goaf foundation, the location of goaf distribution and time effect,use numerical simulation software FLAC3 D and adopt improved creep constitutive model to calculate and analyze the law of subgrade settlement.Determine the critical security zone of goaf,then establish the subgrade settlement prediction model within the scope of the goaf.Which provide reference for the design and construction of the actual project. The main conclusions are as follows:(1)Compared with Mohr-Coulomb constitutive model,the results with the improved creep constitutive model are more consistent with subgrade settlement theory and closer to the real.(2) according to analysis of foundation settlement mechanism, the goaf foundation settlement is divided into instantaneous settlement period,active settlement period and stable settlement period.By comparing the foundation settlement in different period found that the settlement difference is very greatly,subgrade settlement occurs mainly in the instantaneous settlement period and active settlement period.(3) Change goaf and subgrade relative position,analyze the rule of subgrade settlement and differential settlement in different positions,then determine the critical security zone of goaf.(4) By comparing the existing common subgrade settlement prediction model,select simple and practical three-point exponential curve,analyze settlement mechanism during the excavation of the tunnel,consider differences between goaf hole and tunnel,then correct Peck formula to be used to predict the instantaneous settlement of goaf subgrade,and combined with three-point exponential curve to establish the goaf subgrade settlement prediction model.In this paper,the results of the prediction model is basical consistent with the measured results,so it can provide reference for design and construction.