| The project in collapsible loess field is more and more, accompanied by the NSF problem is complex, pile negative resistance varies greatly in different conditions and soil conditions. In order to study the interaction of soil-pile, analysis of regional collapsible loess NSF's feature, to avoid wasting by direct application of the relevant technical specifications caused, Based on this, studied the related issues of pile's negative friction in collapsible loess by theoretical analysis and experimental method, the main conclusions as follows:(1) Reference large amounts of data, combined with laboratory test, Xi'an area's collapsible loess characteristics were studied, analyzed the factors of affecting the region collapsible coefficient, established the regression model by the natural water content, void ratio, plasticity index, analysis the influence of heavy weight of each factor, determined the coefficient prediction model collapsible.(2) Application of Fuzzy Mathematics Assessment in the region of loess collapsibility,establishing the fuzzy relationship matrix approximation of natural moisture and natural void ratio between the weight loess collapsibility coefficient, using fuzzy inference, by centralizing information, using the error analysis to verify the reliability of the model, evaluated the collapsible areas. Determining the area of collapsible type is self-weight collapsible loess,collapsible classification is grade ?, so providing a reference for similar projects.(3) Based on load transfer method, using bilinear hardening transfer function model to establish a mechanical model of single pile, considering the effect of negative skin friction caused by collapsible loess flooding. Supposed soil subsidence flooding curve in line with a straight line or an exponential distribution, derived the pile of negative friction resistance,neutral point and analytical expression of axial force in load, water, load and water three cases.With examples to analyze the effect of soil properties and pile on the pile parameters of sustained force.(4) The pit and pile foundation water immersion were test in region of Xi'an area, got the surface settlement curve, the test area's curve of deep settlement is with soil depth exponentially distributed, each cross-section showed a Gaussian distribution, the settlement of field test pit table is amount from the test center to test pit outward direction gradually decreases, and the amount of soil collapsible amount related to flooding, according to this can determine the scope of the test pit flooding; compared the experimental and theoretical natural state of flooding conditions axial force and pile side resistance calculations, analysis of pile foundation for collapsible loess soaking influence. |
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