| With the fast development of different types of the constructions, a lot of engineering geological problems have been increasing remarkably in China, and the sustainable development of the urban constructions has been affected by factors of geology and environment significantly. An important research orientation which means to make full use of geological environment conditions has become one of the most important orientations in the engineering geological fields in order to prevent the possible engineering geological problems and decrease the geological disasters. It is the fundamental work of the city planning constructions which included the estimation and regionalization of the rock and soil foundations. Thus, it is great significant of the optimization utilization of the rock mass and soil mass.Site area of Shanghai world expo 2010 is located in the waterfront along Riversides of Huangpu which is at the intersection of Nanshi, Luwan and Pudong new area in Shanghai World Expo Park can make great effect of urban functions, and the leap-forward development of the city can be realized. The Shanghai world expo venues will become the most beautiful waterfront landscapes and the zone of economic centers as well as the multifunction zones of culture and sports so as to adjust the city industrial structure and promote the formation of new growing points for economy in Shanghai. Therefore, the construction of Shanghai World Expo Park has very important functions in the development of Shanghai. The liquefaction of sand soil and uneven settlement of foundation can be caused by silty soil, sandy soil as well as soft clay distributed widely in Site area of Shanghai world expo. At the same time, series of engineering problems can also be caused by the existence and movement of the underground water which has influenced the physical and chemical properties of foundation soil directly. In order to ensure the engineering quality and prevent the possible environmental engineering geological problems, it is necessary to make the comprehensive zoning evaluation for the engineering geological availability of foundation soil in Site area of Shanghai world expo.The study is based on the project of"Study on the influence of organic matter in the progress of marine soft soil foundation consolidation"sponsored by the national scientific fund,and the project of"Extension synthesize evaluation and analysis on the building availability of the underground space in Shanghai World Expo Park"cooperated by Shanghai Institute of Geological Survey and Jilin University. The concept of engineering geological availability has been proposed in the paper, and the engineering geological availability of the foundation soil in the site area has been evaluated. According to the characteristics of the environmental engineering geology of the area, the evaluation index systems of the soft clay property, the vibrating liquefaction and the seepage liquefaction of sand soil have been established respectively, in this way, the evaluation model of the engineering geological availability of the foundation soil in Shanghai World Expo Park has been established. In this paper, the engineering geological availability of the ground building and the underground space of the foundation soil in site area of Shanghai world expo has been studied. By using Surfer and MapGIS, the visualized expressions of extension evaluation results have been realized which made the results more intuitively in order to guide the practical engineering construction.By means of the deep study on the engineering geological availability of foundation soil in Site area of Shanghai world expo, some conclusions have been got as follow:1. Based on the investigation data of the boreholes, the foundation soil in the site area is composed of soft soil, clay soil, silty soil and sandy soil. The study shows that the distribution of shallow sand soil layer is unstable, and some serious accidents such as water-inrush from pits, slope failure may be caused by the liquefaction of sand soil. Therefore, it is important to evaluate the engineering geological availability of the soil layers in the site area of Shanghai World Expo.2. By comparing various evaluation methods of engineering geologic, the software based on extension theory has been used in the evaluations of the engineering geological availability, the study on the evaluation results shows that the software can apply well in the evaluation of the engineering geological availability of the foundation soil, and because of the wide applicability of the extension theory, it can also be applied in other fields of studies.3. On the basis of the study on the fundamental engineering properties in the area, 8 parameters have been chosen in the evaluation of the properties of soft soil included void ratio, water content, density, liquid index, internal friction angle, cohesive force, compression coefficient and compression modulus. In the evaluation of the vibrating liquefaction of sand soil, 10 parameters have been taken out, they are void ratio, water content, density, internal friction angle, cohesive force, standard penetration number, specific penetration resistance, uneven coefficient, average diameter of sand, relative density. In the evaluation of the seepage liquefaction of sand soil, 8 parameters have been chosen included porosity, clay content, silt content, uneven coefficient, water content, internal friction angle, cohesive force, compression coefficient. According to《Foundation ground and foundation design specification》(GB50007-2002) and《Geotechnical engineering investigation specification》(GB50021-2001), the evaluation of the engineering geological properties of soft soil has been divided into 5 grades: the softest, soft, the middle grade of soft, hard and the hardest. The evaluation of the liquefaction of sand soil has also been divided into 5 grades: be apt to liquefaction, be apt to liquefaction comparably, be apt to liquefaction in the middle grade, and be not apt to liquefaction. The study on the results of extension evaluation of soft soil shows that the main type of soft soil in the area is the middle grade of soft soil in the area. The study on the extension evaluation of vibrating liquefaction and seepage liquefaction of sand soil shows that sand soil and silty soil which has the characteristics of vibrating liquefaction and seepage liquefaction distributed widely in the area, so engineers and technicians should pay more attention to the problems caused by sand soil.4. In the evaluation of engineering geological availability of ground building, 7 parameters have been chosen composing of the evaluation system, they are: grade of soft and hard, buried depth, soil thickness of the softest soft soil layer; grade of liquefaction, buried depth, soil thickness of the sand soil layer which is tend to liquefaction; buried depth of ground water. Combining with the visualized expressions implemented by Surfer and MapGIS, On the basis of the extension study on the engineering geological availability of ground building in the area, the best availability ground is 30% of all, the good availability ground is 65% of all, and the bad availability ground is 5% of all. Therefore, within the site area of Shanghai world expo, the evaluation grade of the engineering geological availability of the ground construction is mainly good; however, importance should still be attached to the possibilities of the deformation of soft ground and the sand liquefaction.5. On the study of the engineering geological evaluation of the underground space in Shanghai world expo, 6 parameters have been chosen in the evaluation of the engineering geological availability of the underground space by comprehensive considering the types and the engineering geological properties of the foundation soil as well as the spatial distribution characteristics of the foundation soil layer, the specific parameters are as follow: average thickness, thickness ratio, average buried depth of soft soil layer; average thickness, thickness ratio, average buried depth of drift sand layer. The study on the results of visualized expressions of the extension evaluations shows that: In 0m -3m soil layers, the engineering geological availability of the underground space is mainly middle degree, and grounds of bad engineering geological availability only occur in a few places in the area; in 3m -15m layers, most of places near the Huangpu River, the engineering geological availability of the underground space is mainly bad, and in other places of the site area, the availability is middle degree;in 15m -40m layers, the engineering geological availability of the underground space is mostly good, meanwhile, a few parts near the south of Huangpu River, the engineering geological availability of the underground space is middle degree. In the evaluation of the three layers, the most important layers are 3m -15m layers due to the engineering geological properties of the underground construction layers. In this layer, soil included muddy clay, mucky silty clay and silty soil, sand soil etc. distributes widely, and the engineering geological availability is not good. Therefore, more attentions should be attached in the practical engineering in order to solve series of the engineering geological problems.In order to explore new methods of engineering geological availability of foundation soil, different kinds of evaluation parameter indexes of different types of foundation soil have been carried out which enriched the methods of the evaluations of engineering geological quality. By using Surfer and MapGIS, visualized expressions of extension evaluation results have been realized. Based on the evaluation of the engineering geological availability of foundation soil in site area of Shanghai world expo, the evaluation results of the engineering geological availability have been given for the planning and management of the construction. Therefore, it provides the fundamental basis included the determination of the optimum scheme of the land utilization and good region of the construction. On the engineering construction condition of Shanghai world expo, the engineering geological availability has been reflected by the visualized expressions of extension evaluation results intuitively, and it plays an important role throughout the constructions in the site area of Shanghai world expo.
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