反复荷载作用下软土地基的长期沉降计算

发布时间：2018-04-29 12:25

本文选题：软土地基 + 反复荷载　；参考：《河南工业大学》2017年硕士论文

【摘要】：能够科学合理预测软土地基上建筑物的长期沉降是保证建筑物安全使用的关键环节。我国软土地基分布广泛,随着发展需要,不可避免在软土地基上修建许多储存粮食和石油等物质的仓储设施。这些建筑物的特点是在施工结束后,于仓储设施自重产生的永久荷载基础上多次加载和卸载,这一问题已引起学者的广泛关注。目前对交通荷载产生的反复荷载研究比较多,且方法比较成熟,但是它的变化频率很高。而仓储设施产生的反复荷载属于低频荷载,且相对波动较大,针对这类反复荷载作用下长期沉降预测还没有形成较成熟的计算方法。结合软土地基复杂的工程特性,现有的沉降方法假设条件与实际工程中的土体不完全相符,往往造成沉降结果和实测结果相差较大。因此,一般采用基于实测数据的经验公式法来进行地基沉降预测,但是是否适用这种低频率反复荷载产生的沉降变形还有待研究。本文首先针对仓储设施产生的反复荷载特点进行分析,然后对国内外预测沉降的计算方法进行综述介绍,很多方法都是在太沙基一维固结理论的基础之上提出的。考虑到反复荷载的无规律性,采用使用广泛的基于实测数据的拟合经验公式法,并对其中常用的几种拟合曲线法进行单独分析,列出其中的优点和局限性,结合仓储设施的结构特点,利用Origin软件的数据处理功能提出双曲线法和指数曲线法、三点法可以用于仓储设施的沉降预测。利用工程实例验证这三种方法的可行性,通过这三种方法拟合值与实测值的对比分析,得出指数曲线法拟合度很高更适合仓储设施的长期沉降,但是这种方法只针对运营期的沉降预测。因此,本文还提出了另外一种方法—叠加法,利用施工期的沉降观测数据进行地基沉降预测。叠加法的原理就是根据仓储设施在使用期间重复着加载-卸载-加载产生多级荷载的过程,对无规律的反复荷载进行分析,把荷载进行分级处理,大小相近的为一个级别,得到每个级别荷载作用下的以指数形式发展的沉降拟合曲线,所有沉降曲线加在一起为总沉降,最后用实例验证叠加法的科学合理性。通过对软土性质和仓储设施产生的反复荷载分析,提出了指数曲线法和叠加法适合预测软土地基长期沉降,叠加法还可以预测多级荷载下的地基沉降,并验证了它们的合理性,以便以后能够有效合理的为沉降预测提供依据。
[Abstract]:It is the key to ensure the safe use of buildings to predict the long-term settlement of buildings on soft soil foundation scientifically and reasonably. The soft soil foundation is widely distributed in China. With the need of development, it is inevitable to build a lot of storage facilities to store food and oil on the soft soil foundation. The characteristics of these buildings are that they are loaded and unloaded many times on the basis of the permanent load caused by the self-weight of storage facilities after the construction. This problem has attracted extensive attention of scholars. At present, there are many researches on the repeated loads caused by traffic loads, and the methods are more mature, but their frequency of change is very high. However, the cyclic load generated by storage facilities belongs to low-frequency load and is relatively fluctuating. There is no mature calculation method for long-term settlement prediction under this kind of repeated load. Combined with the complex engineering characteristics of soft soil foundation, the existing settlement method assumption condition is not completely consistent with the actual soil mass, which often results in a big difference between the settlement results and the measured results. Therefore, the empirical formula method based on the measured data is generally used to predict the settlement of the foundation, but whether it is applicable to the settlement deformation caused by the low frequency repeated load has yet to be studied. In this paper, the characteristics of repeated loads generated by storage facilities are analyzed firstly, and then the calculation methods of predicting settlement at home and abroad are summarized and introduced. Many of the methods are based on the one-dimensional consolidation theory of Terzaghi. Considering the irregularity of repeated load, the empirical formula method based on measured data is widely used, and several fitting curve methods commonly used are analyzed separately, and the advantages and limitations of these methods are listed. Combined with the structural characteristics of storage facilities, the hyperbolic method and exponential curve method are proposed by using the data processing function of Origin software. The three-point method can be used to predict the settlement of storage facilities. The feasibility of these three methods is verified by an engineering example. Through the comparison and analysis of the fitting values and the measured values of the three methods, it is concluded that the high fitting degree of exponential curve method is more suitable for the long-term settlement of storage facilities. But this method is only used to predict the settlement of the operation period. Therefore, another method, the superposition method, is put forward in this paper to predict the foundation settlement by using the settlement observation data during the construction period. The principle of superposition method is that according to the process of repeated loading, unloading and loading of storage facilities during use, the random repeated loads are analyzed, and the loads are classified and treated, and the same size is a grade. The fitting curve of the settlement developed in exponential form under each grade load is obtained. All the settlement curves are added together as the total settlement. Finally, the scientific rationality of the superposition method is verified by an example. Through the repeated load analysis of soft soil properties and storage facilities, the exponential curve method and superposition method are proposed to predict the long-term settlement of soft soil foundation, and the superposition method can also predict the foundation settlement under multistage load, and verify their rationality. In order to effectively and reasonably provide the basis for settlement prediction in the future.
【学位授予单位】：河南工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU433;TU447

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