Research On Foundation Evaluation Of Sand Mined Goaf And Treatment Technology Of Bridge Foundation Pile

In the survey and design of highway and bridge,the determination of the boundary and influence scope of the sand mined goaf,the evaluation of the foundation deformation and stability of the sand mined goaf,and the formulation of the treatment technical scheme of the sand mined goaf directly affect the selection,optimization and project investment of the whole scheme.At present,there are few research results on sand mined goaf,and there are not many related norms and regulations involved in this aspect.How to effectively identify the distribution scope and engineering characteristics of sand mined goaf,scientifically carry out stability evaluation and reasonably determine the treatment of sand mined goaf have become urgent issues to be solved.Relying on a super large bridge project of 344 provincial highway in Northern Jiangsu Province,the foundation evaluation of sand mined goaf and the treatment technology of bridge foundation pile are studied(1)Exploration technology and method of sand mined goaf: This paper discusses the feasibility of application of engineering geophysical exploration technology in river sand mined goaf exploration,puts forward suitable geophysical exploration methods through comparison and selection,and considers that the comprehensive geophysical exploration method combining shallow seismic exploration and shallow stratum profile can be effectively applied to river sand mined goaf exploration,which has been verified in practical engineering;The principle of sedimentology particle size analysis is used to analyze the particle size composition of soil,and the method and process of determining the influence range of river sand mined goaf based on the principle of sedimentology particle size analysis are proposed.(2)Evolution law of physical and mechanical properties of disturbed soil with large deformation in sand mining area: combined with the data of actual engineering investigation drilling and geotechnical test,the evolution law of soil physical and mechanical properties parameters before and after sand mining disturbance is compared and analyzed from horizontal and vertical directions,and the influence law of sand mining disturbance on soil physical and mechanical properties is summarized.(3)Disposal measures of sand mined goaf engineering: the common disposal measures of sand mined goaf engineering are analyzed,and the disposal methods suitable for practical engineering are put forward;ABAQUS finite element software is used to establish the analysis model of bridge pile foundation pile end post grouting plus solid in sand mining disturbed area,and analyze the influence of sand mining on the vertical bearing capacity of pile foundation and the influence of post grouting on the bearing capacity of pile end.