Engineering Properties Of Soils And Initial Establishment Of Engineering Geological Database Of Chengdu Urban District

The main purpose of the site geotechnical investigation is to identify the engineering geological conditions of the site,providing the basis for the design of construction and guaranteeing a smooth construction and the later stabilization.The soils of Chengdu urban district are complicated,physical and mechanical properties of all kinds of soil are quite different.In addition,there are expansive soils in Chengdu urban district,they will expand upon imbibing water and shrinkaging after water loss,which is very unfavorable for construction,so it's important to research the geotechnical investigation and engineering characteristic.Urban engineering geological data is so complex and abundant,in order to facilitate the management of engineering geological data,Estabishing engineering geological database of Chengdu urban district is of great significanceBased on the study of the environmental geological conditions of the study area,soil engineering properties have been studied,it's summarized what main engineering geological problems exist in every engineering geologic unit.Engineering geological database is established on the grounds of ArcGIS.Combined with the research of geological data structure and spatial distribution,three-dimensional geological model is built with ArcGIS three-dimensional module,initially realizing 3D visualization.Then some conclusions are attained following as:(1)Basing on the systemic analysis of Chengdu geological environmental conditions,soil engineering properties of Chengdu urban district is studied in detail,some engineering geological problems are existed,such as expansive soil,sand liquefaction and mucky clay.Expansive soil exists in second and three terraces and presents scattered-island distribution.Liquefied sands are made of silt and fine sands,mainly distributed in first terrace.Silt clay is soft-fluid plastic state,scattered in the research area.Based on the study,the variability and correlation of parameters characterizing engineering properties are analyzed,the result shows that mechanical index is more variable than physical index,and that mechanical index is closely related to moisture content,void ratio and liquidity index,then we can use them to evaluate cohesion,angle of internal friction,compression modulus and characteristic value of bearing capacity.In addition,SPT blow count/ dynamic penetration blow count and compression modulus are used to evaluate characteristic value of bearing capacity,the result is consistent with standard,which has practical value and provides a reference for the construction.(2)According to GIS,we established the engineering geological database by collecting the geological environment data of study area.It implements the integrated management of the study area,and its system includes two respects: graphic data and attribute data.Analyzing and evaluating the engineering properties can be achieved with graphic data,such as,distribution of sand liquefaction and the compression zoning of gravel layer.Based on the analysis of correlation between physical and mechanical properties,we researched the space differentiation of some indicators,then predict the mechanical indicators and engineering properties.The results are accurate.As with relationships it has some advantages and disadvantages.(3)The three-dimensional display of Chengdu engineering geological data was achieved by using the ArcScene module.It can present stratum structure in partial study area intuitionally and imitate stratigraphic section,and query physical and mechanical parameters.On account of measured borehole data,the model has high precision with some practical value.