Research On Mini-structure Of Foundation Soil And Variation Of Site Dynamic Character Under City Construction

This topic was received unite subsidization by the Ministry of Education science and technology research key project (2003-77), Guangxi natural sciences fund project (0447001,0575019), Guangxi scientific research and technology development plan project(0632006-lB), Guangxi Water conservancy department science and technology special fund (2004-4)The city is a product of the history progresses, and it is a symbol of human moving towards modernization, prosperity, developing and civilization, it is also the place where the human lives and works. However, human play a negative role in the progress of urbanizing, the geological environment of the city is destroyed inevitably, and the urban construction is the strongest ways of humans' activities impose on the geological environment.With the fast development of economy, the enhancement of the urbanization process, construction is multiplied and amplified in our country, the urban construction load function on the geologic body is more obvious, to will affect inevitably the geologic body and the foundation soil character change. This paper's goal is to explore the change rule for the foundation soil mini-structure and the dynamic character under the urban construction environment, in particular after them has these variations, whether different the natural vibration period of the site from building in this region, and whether can have the resonance effect. The research results have the vital scientific significance to the structure earthquake resistance protection, preventing and reducing earthquake disasters work.First, embarks from the urban construction and the mini-structure, elaborated each kind of load function form, the function characteristic and the action mechanism which impact on the geologic body, made the preliminary appraisal about the city geological environment is destroyed by the urban construction. Introduced systematically Professor Wu Heng proposed mini-structure physical concept and practice significance about "macro-structure, mini-structure, micro-structure" three level of division theories in soils structure. After collected and using the material of other people studied in the full, mini-structure variation was analysis and research thoroughly under the urban construction environmentIn order to understand the rule of the earthquake wave spread in the soils, analysis the influence factors, done the soil sample wave velocity experiment in laboratory, the influence rule has analyzed the physical mechanics change to the wave velocity under the urban construction function, Searches each kind of factor influence wave velocity spread, build the model relation physical mechanics characteristics to shear wave velocity which soil density and water content, analyzes its change rule of shear wave velocity under the stress condition. And then two field shear wave velocity separately was test in constructs before and after to the Guiping commercial buildings, the dynamic character variation question was further analysis and research under urban construction.After tests wave velocity in laboratory and field, establishes the computing analyses model of the three dimensional finite element. Through two example model of ANSYS modal analysis and the earthquake time interval analysis, understood change rules about earthquake wave spread effect and site dynamic character, which after the foundation soil rigidity and the density changes under urban construction factor as building deadweight load increase and the ground water level changes.The comprehensive wave velocity test and the computer simulation computed result, it has discussed that intrinsic mechanism of the soil mini-structure 1 variation by the urban construction behavior, has analyzed each kind of factor of site predominant period variation under the urban construction, and establishes the relations between the major effect factor and the dynamic character, gives the formula, established the model of site predominant period variation under the urban construction and the model of the earthquake disaster for the predominant period variation change.Finally, coordinate with the results gained, some feasible proposals are put forwarded to ultimately make a further study on solving the existent problems in this paper.