Implementing Of 3D Permeable Bed Modeling Algorithm

Comprehensive development and utilization of urban underground space and long-term large-scale exploitation of groundwater will cause the permeable bed to compress and deform,eventually leading to a wide range of groundwater level decline and ground subsidence.Therefore,the scientific research on the permeable bed is particularly urgent and important.Three-dimensional visualization modeling is a most intuitive and effective method to describe the permeable bed.It is the basis of underground space analysis,geological phenomena interpretation and mineral resource evaluation.And it is important in the fields of groundwater resources assessment and underground pipeline lying.In this thesis,a residential construction site in Xindu District of Chengdu is taken as the study area,and the borehole data of the site are collected as the data source.Based on analysis of the basic permeable bed information of the site,a 3D permeable bed modeling algorithm based on the irregular tetrahedral network and topological relation is designed.The prototype system is established to implement the 3D permeable bed model and evaluate the model accuracy.The main work and achievements of this thesis are as follows:(1)In the study area,278 borehole data were collected as the information source of the permeable bed.The minimum,maximum and average of the borehole depth were 12,29 and 20.46 m,respectively.The minimum,maximum and average values of the permeable bed numbers were 2,12,5.76 layers.Based on the analysis of borehole data in the study area,the regional general sequence table is established,and the sequence relation of the permeable bed is found from the borehole sample information.(2)The grid-shaped profile model based on the element structure is constructed(ie,point-line-plane).The Delaunay triangulation algorithm is used to generate the irregular triangulation on the surface to ensure that each section has a definite topological relation.The grid-shaped profile model is composed of a lot of finite plane to simulate the permeable bed.(3)The irregular tetrahedral model based on the voxel structure is constructed(ie,plane-body).In order to simplify the irregular permeable bed composed of finite plane,the virtual borehole is introduced to interpolate the study area.Then generate a more accurate,smooth and reasonable surface element model by model reconstruction.The irregular tetrahedral model is modeled by element structure from top to bottom.(4)The 3D permeable bed model are modeled by 90% borehole data,and the remaining borehole data is used to evaluate accuracy of the algorithm.From the difference between thickness of the permeable bed model and actual,the root mean square error can be seen that the algorithm can accurately establish the 3D permeable bed model in the study area.Especially the RMSE is less than 0.5 in the partition modeling and depth interval is set to 0.1m.