The Environmental Effect On Urban Soil Bodies

With accelerating the progress of urbanization,the sharp increase of the population and the rapid development of social economy, the quantity and quality of the resource of urban soil are profound changing. Thus it caused a series of environmental engineering problems. The research by native and foreign scholars lack systematicness, because they seldom analysis the soil's environmental effect from the angle of field directly. Starting with basic effects of the character change of urban soil, by consult a great deal of literature and datum and combined with theory calculation, all inducements of changing about the soil under city environment are discussed from the angle of field.Environmental effects of urban soil includes the following four factors: the effects of the field of additional stress,the effects of hydrogeochemical field,the effects of thermal field,the effects of superimposed magnetic field. The additional stress is induced by the loading of building on the foundation, and it spread distributes in great rang of the soil beyond the foundation. When building group is formed in some region, additive effect of additional stress is obvious and regional land subsidence is appeared. in addition, unloading and loading in geotechnical engineering also can induce stress redistribution in the soil, and result in the effects of the field of additional stress. The geo-environmental changes result in the change of hydrogeochemical field. Based on the test results, the geo-environmental changes can influence the structure and mineral composition of soil by chemical action and physical action. Macroscopically, physical and mechanical properties of soil are changed. With accelerating the progress of urbanization, the urban heat island effect has an important effect on the thermal field of soil. Based on discussion the interaction between thermal, chemical and mechanical mechanism, temperature to be driving force, though changing the component and content of porosity fluid in the soil, the experiment reveals the significance of the effects of thermal field. Urban electromagnetic pollution is produced with the development of technology. The superimposed magnetic field on city produces an effect on electric double layer and changes on the surface of cohesive particle, thus causing change of mesostructure conformational feature of cohesive soil.