Research On Settlement Deformation And Estimation Of Stability Of The Chaiwen River Bridge Foundation Overlying Mined Out Area

The mined out area is more extensive in our country.With the acceleration of the process of social modernization,the construction of highway,railway,bridge,tunnel and other infrastructure changes with each passing day,and some have to be built on the mined out area.The Chaiwen River bridge,located in Xintai city,is a 6-20m reinforced concrete simply supported beam.The bridge is mainly located in the mining range of Huayuan coal mine(formerly Zhangzhuang mine).The mined out area is characterized by long mining time,repeated mining in time and space,and multilayer mining.With the influence of Wennan F1 fault,the division and characteristics of goaf are more complex,seriously affect the safety of bridge.In this thesis,the mined out area is taken as the research object,and the following research work was carried out.(1)Research on the factors influencing the settlement of bridge foundation,determine the main factors.(2)Research on the distribution of mined out area,Including spatial distribution,roof management,surrounding rock structure and physical and mechanical properties.(3)Determine the working condition of bridge foundation settlement analysis.The deformation law of the bridge foundation in 4 different working conditions,is analyzed by UDEC(Universal Distinct Element Code).(4)Research on the stability of bridge foundation in different working conditions,and the effect of grouting treatment.The qualitative and quantitative evaluation of the study area is carried out by means of the method of mining conditions and the method of probability integration.As a building site,the study area belongs to unstable site,and as a foundation of the bridge belongs to unstable foundation.The results of the two methods are consistent.According to UDEC simulation results,under the condition of no grouting in the goaf and karst,there is a large amount of residual subsidence,residual slope and residual horizontal deformation,so the study area is unstable site(foundation).In goaf and karst roof has obvious boundary sliding and yield phenomenon,a larger shear displacement,and the stress field in the goaf and karst roof stress concentration,the minimum principal stress in the roof at both ends of tension stress in the mined area and karst area near the settlement of a sudden increase of the deformation in the vertical discontinuity.Under the condition of goaf and karst grouting,the residual subsidence,the residual slope and the residual horizontal deformation of the building site are obviously reduced,so it is a stable site(foundation).There is no obvious boundary sliding and yielding phenomenon in rock mass,the shear displacement is almost zero,the stress concentration phenomenon disappears,and no tensile stress appears.The settlement and deformation process of the rock mass under the condition of this kind of work is actually consolidation compaction process,and the deformation curves accord with the consolidation compaction characteristics.Through comparative analysis of two kinds of conditions before and after the grouting simulation calculation results,show that the grouting can greatly reduce the settlement of the bridge,making the original unstable abutment becomes stable,and the engineering effect is ideal.Through the research,we can see that the main factors affecting the stability of the bridge foundation are the existence of goaf and karst and the load of the bridge.The grouting method has obvious effect on controlling the settlement deformation of bridge foundation,to make The bridge foundation settlement within the allowable range.