【作者】 陈乾星；

【导师】 马克生；

【作者基本信息】 太原理工大学 ， 岩土工程， 2008， 硕士

【摘要】 单桩静载荷试验是确定单桩极限承载力的最直观、可靠的方法之一,也是我国规范规定的方法。但在工程实践中,由于荷载装置、试桩费用、工程施工进度及试验终止条件等限制,未能将试桩压至破坏,无法获得完整的Q-S曲线,直接得到单桩的极限承载力。因此,如何利用已获得的有限的静载荷实测数据,通过相关数学模型合理的预测单桩极限承载力就具有重大的意义。作为上世纪九十年代发展起来的一种新型桩基础,挤扩支盘桩以其较高的承载力和较低的沉降量取得了良好的经济和社会效益。但其荷载传递性状比较复杂,如何通过预测的方法来获取其极限承载力的相关研究还比较少。针对这种情况,本文首次从灰色系统理论的角度出发,在不需要预先知道挤扩支盘桩完整Q—S曲线的形状情况下,仅依据静载试验初始加载阶段的少量实测数据,通过灰色预测法,将沉降S作为灰作用量,利用MATLAB7.01,编写适用于挤扩支盘桩单桩极限承载力及对应沉降的全信息、自调整非等步长GM(1,1)预测模型程序。依据资料所提供的挤扩支盘桩Q-S曲线,在各级GM(1,1)预测模型下,进行了挤扩支盘桩单桩最大加荷条件下对应沉降的预测,通过对预测值的统计分析:各级非等步长GM(1,1)预测模型预测值均满足工程要求。然而从工程经济、合理、安全综合角度出发,1—9级全信息非等步长GM(1,1)预测模型预测效果好于其它各级预测模型的预测结果。此外,本文还将灰色系统理论中的关联度分析理论应用于挤扩支盘桩静载荷试验数据的分析,从而对挤扩支盘桩的承载特性,从新的角度进行了有意义的尝试,深化了对其承载特性的认识:在影响挤扩支盘桩极限承载力的各因素中,支盘端承力对单桩极限承载力的影响最大,其次是桩侧摩阻力的影响,桩端阻力对桩极限承载力的影响最小,随荷载加大,支盘作用增大,承载力逐步发挥。最后,采用双曲线法对挤扩支盘桩竖向极限承载力进行了预测,同灰色预测结果相比,二者在分布上相接近,均服从正态分布,且预测值满足工程需要。更多还原

【Abstract】 The field vertical load test of a single pile is one of the best and intuitionistic method of determining the ultimate bearing capacity of a single pile, it’s also the prescript method of our country’s criterion. But in many cases we can’t destroy the testing pile, achieve the integrated curve of the Q-S and the exact value of ultimate bearing capacity of a single pile for the limit of the testing equipment, expenditure, work plan and the condition of the terminate testing ect.So it is an event of significance to acquire the prognosticate data through the finite data which obtain by the field vertical load test.The Squeezed branch Pile is a kind of new-type pile foundation which developed at the beginning of the 1990s. It has made the good economic and social benefits for its higher bearing capacity and low settlement. But little correlative researches had been done because of the complex load transferring rules of this kind pile. In respect to this case, this paper proposes to predict the ultimate bearing capacity of squeezed branch pile by Grey system theory. According to the Grey system theory, this paper proposes the non-same step GM(1,1) model which can be applied to predicate the ultimate bearing capacity of squeezed branch pile. And applies them to practical projects, their corresponding programes were written in MATLAB7.01 language, and predicate the settlement of squeezed branch pile based on the curve of piles in different load-level. The results show that the non-same step GM(1,1) model can meet the project requirement. And the one to nine degree GM(1,1) is the best for the ultimate bearing capacity prediction.At the same time, based on the results of static loading test, the influence factors of the ultimate bearing capacity of squeezed branch pile are analyzed by gray system theory in this paper.The analysis result shows that the correlation index order is plates resistance, shaft resistance and toe resistance.At last, use the Hyperbola method to predict the Ultimate bearing capacity of single pile and compare with the prognosticate results which by Grey method, the predicated results obey the Gaussian distribution and meet the demand of the project.更多还原