Study On The Calculation Method Of Grid Size Of Urban 3D Geological Modeling Based On Error Constraint

In order to support the geological application such as presentation of the result of urban geological surveys,geological analysis and numerical simulation,3D modeling of urban geology facing the development from 3D geological structural model to the high precision integrated vector-raster modeling cored by grid/property model,so it is one of major problems,should be solved urgently,in urban 3D geological modeling that how to synthetically use the various geological data and through the appropriate research method to obtain the suitable grid size.The objective of this paper is that,through the statistics and analysis of geological data,propose the method that can obtain the appropriate grid size of 3D geological modeling matching the characteristics of shallow sediments in urban area,and offer theorical basis for grid size of urban 3D geological modeling.(1)The shallow sediments in urban area of plain are deposited relatively horizontally and its sedimentary characteristics are strong.The sedimentary scales in areal and vertical direction are different and therefore the vertical and lateral grid size can be separately discussed by their own sedimentary characteristics.(2)Through the analysis and study on thickness of sediments interpreted by drill and so on,this paper,based on the method of mathematical statistics and the principle of maximum error,synthetically consider all of sediments or the target sediment and then proposed three methods,including minimum thickness method,expressed one by one and thickness statistics,to calculate the vertical grid size,from which the researcher can choose the suitable method to calculate the appropriate vertical grid size.(3)Through the analysis of the extent range and its shape of sediments,obtain the boundaries of shallow sediments in urban area such as sedimentary zoning map and simplify the boundaries by using equal area substitution method,then determine the lateral grid size of each sediment by choosing the suitable calculation method based on its shape of extent range.finally,synthetically consider the impact of all of sediments to determine the lateral grid size for the whole grid model.In order to verify the methods proposed above,the drill data in Huhehaote and the boundaries of quaternary sediments in Huaibei plain are selected to calculate the vertical grid size and lateral grid size respectively and the result shows that the vertical and lateral calculation methods can offer suitable vertical and lateral grid size within the allowable relative-error.