长期水平荷载作用下吸力式沉箱基础承载性能试验研究

发布时间：2018-06-10 15:18

本文选题：吸力式沉箱 + 水平荷载　；参考：《东南大学》2015年硕士论文

【摘要】：21世纪社会经济发展的强大推动力离不开对海洋石油资源和海上风能的大规模开发利用,但由于深水条件下的海洋环境与地质条件的复杂性,传统的重力式基础、桩基础等基础形式在技术难度和施工难度上都遇到极大困难。吸力式沉箱基础作为一种新型的基础形式,具有适用于深水和软弱土质等优点,可能会成为海洋平台或风电场基础的一个新选择。目前,针对水平荷载作用下吸力式沉箱基础承载特性研究中很少有考虑软土流变效应的研究现状,有必要对长期水平荷载作用下吸力式沉箱基础承载特性展开相关试验研究和理论计算分析。本文通过室内模型试验和理论分析,对吸力式沉箱基础在长期水平荷载作用下的承载特性进行了研究,主要内容和结论如下：1.通过一组短期模型试验,确定了吸力式沉箱基础的极限承载力。试验中模型采用钢制沉箱,其沉箱壁和顶板厚均为20mm,沉箱外直径为500mm,高为800mm。2.采用宏细观方法对长期水平荷载作用下的半模型试验进行了分析,利用PIV技术研究了吸力式沉箱基础前侧土体流变效应。试验表明在长期水平荷载作用下,模型试验中特征点的水平位移持续增加,在加载前期位移增加较快,后期增加趋势逐渐变缓。3.通过两组不同水平荷载作用下的长期模型试验,对吸力式沉箱基础随时间的位移变化规律与土压力分布规律进行了分析。随着加载时间的持续,土面水平位移、转角以及土压力不断增大,前期位移增加较快,后期逐渐趋于稳定,而土压力沿深度方向类似呈抛物线分布。4.为考虑土体的流变效应对基础承载特性的影响,通过建立理想弹塑性p—y曲线法中的土抗力系数k与时间变量t的关系,并对沉箱基础底部抵抗矩与侧摩阻力的影响进行了修正,提出了考虑土体流变效应的吸力式沉箱基础长期性能分析方法。采用该方法对全模型试验结果进行分析,理论计算结果与试验结果相差10%左右。最后结合某工程悬索桥方案的中塔吸力式沉箱基础进行计算,预测了长期水平荷载作用下位移与时间的变化规律,可为工程设计提供参考。
[Abstract]:The powerful driving force of social and economic development in the 21st century cannot be separated from the large-scale exploitation and utilization of offshore oil resources and offshore wind energy. However, due to the complexity of the marine environment and geological conditions under deep-water conditions, the traditional gravity basis, Pile foundation and other foundation form meet with great difficulty in technical difficulty and construction difficulty. As a new type of foundation, suction caisson foundation has the advantages of being suitable for deep water and weak soil, and may become a new choice for offshore platform or wind farm foundation. At present, the research status of rheological effect of soft soil is seldom considered in the study of load characteristics of suction caisson foundation under horizontal load. It is necessary to study the bearing characteristics of suction caisson foundation under long term horizontal load and to carry out theoretical calculation and analysis. In this paper, the bearing characteristics of suction caisson foundation under long term horizontal load are studied by laboratory model test and theoretical analysis. The main contents and conclusions are as follows: 1. Through a group of short-term model tests, the ultimate bearing capacity of suction caisson foundation is determined. The steel caisson is used in the test, the thickness of the caisson wall and roof is 20mm, the diameter of the caisson is 500mm and the height is 800mm. 2. The semi-model test under long-term horizontal load was analyzed by macroscopical method, and the rheological effect of soil in front of suction caisson foundation was studied by PIV technique. The experimental results show that the horizontal displacement of the characteristic point in the model test increases continuously under the long-term horizontal load, increases rapidly at the early loading stage, and slows down gradually at the later stage. Based on two groups of long-term model tests under different horizontal loads, the law of displacement and earth pressure distribution of suction caisson foundation with time are analyzed. With the continuous loading time, the horizontal displacement, rotation angle and earth pressure of the soil surface increase continuously, the early displacement increases rapidly, and gradually tends to stabilize at the later stage, and the earth pressure is parabola distribution along the depth direction. In order to consider the influence of rheological effect of soil on the bearing characteristics of foundation, the relationship between soil resistance coefficient k and time variable t in the ideal elastoplastic p-y curve method is established. The influence of resistance moment and side friction on the bottom of caisson foundation is modified, and the long-term performance analysis method of suction caisson foundation considering soil rheological effect is put forward. This method is used to analyze the experimental results of the whole model, and the difference between the theoretical results and the experimental results is about 10%. Finally, combined with the calculation of the mid-tower suction caisson foundation of a suspension bridge project, the variation law of displacement and time under long-term horizontal load is predicted, which can be used as a reference for engineering design.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU476

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