Additional Stress Induced By The Construct Of City And The Limit Of Geological Environment

City is a result of human activities, a dense resident place, and also an area influenced by people most hardly. The geological environment of city is a dynamic balance system, a space with itself character and function in the nature condition along nature rule.View from geology and mechanics, large-scale construct of city is equal that city put increase scale and intensity load on geological environment. When city environment is disturbed system will maintain balance though itself adjusting .But if the disturb is beyond the system endure limit, the balance will not resume. So we call the city construct limit load which act on geology object as geological environment limit of city. In short, as geological limit.So we study geological environment of city and geological disaster from a new side and pay attention to potential and slow action of city geology. This paper aimed at the limit of carrying capacity and lay stress on the action which additional stress put on geological medium. By that disturbing mechanism can be found which caused ground invalidity, large-scale ground subsidence, quality of aquifer, vibration characteristics of ground and Induced earthquake.First this paper analysis the meaning, forms and spring conditions of the geological limit by theory reasoning and numerical simulation. The direct mode, building load and unloading of excavation, is not the only one. The expression of load caused by activity of city construct and the mechanism that equivalent load is transformed into additional stress were analysis.The essential reason is that the transfer of additional stress caused by construct load changed original stress state of geological mass which induced geological limit. Hereby the study of additional stress is one of important key in this problem.The influencing factors of additional stress were discussed in this paper. Because mesoscopic structure is bridge and carrier of additional stress, we built the mesoscopic structure mode about the transfer and distribution of stress and explained the phenomenon of stress congregate and diffuseness in stratification ground successfully by theory reasoning.We waked up to that additional stress system of mass is a complex and nonlinear system with credibility, randomicity and internal randomicity. Five types of experiments are designed to further reveal the characters of additional stress system. They are experiments of additional stress distribution (including the distribution in even soil, in soil with hardcore and with extension loaded areas), transfer (vertical and horizontal transfer), Chaos, its affect to soil dynamic character and validating experiment. Analysis to the experimental results and phenomenon in tests are given in details in this paper.Not only large number of develop patterns about the additional stress system are obtained; the system is also verified to be an Chaos system with main development pattern through the Chaos calculation from the experimental data. A serial of theory models are established based on the theory analysis and the experimental results. The models describe time and space (determine), Chaos characters of the soil additional stress system, and its affect to the soil dynamic character. The main develop trend of the additional stress system is summarized. The additional stress triggering cities' geological limit is synthesize analyzed. Base on the models and patterns in the experiment, successful explain to the practical geological limit phenomenons is presented, and the patterns behind the geological limit phenomenon test the results strongly.