长短桩复合地基沉降变形规律研究

发布时间：2018-01-08 05:14

本文关键词：长短桩复合地基沉降变形规律研究　出处：《太原理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：长短桩复合地基是岩土工程领域提出的一种新型复合地基,大量的工程实践证明了这种地基处理方法的优越性和安全性。在进行地基处理过程中,不仅要满足承载力的要求,也要对沉降变形进行控制。当前对长短桩复合地基沉降变形规律的研究较少、理论支持不足,因而对其开展进一步的研究既是复合地基理论发展的重要前提,也是工程界的迫切需求。本文以河北廊坊某地的长短桩复合地基实际工程为原型,依托国家自然科学基金项目“刚性基础下组合桩复合地基沉降变形特性及预测方法研究”,采用室内缩尺模型试验对刚性长短桩复合地基的沉降变形规律进行了初步研究和探讨。应用FLAC3D软件对模型试验进行数值模拟及对比分析,采用灰色关联分析方法对影响沉降变形特性的几个主要因素综合考量和排序,旨在为长短桩复合地基的设计提供参考建议。具体完成了以下研究工作:1、试验中设有九根素混凝土预制桩(五长四短),模型试验箱规格为(长?宽?高)2000mm?1500mm?1500mm,且在复合地基特定位置处均埋设沉降标来检测复合地基的内部压缩变形量。根据长桩长度不同(500mm、550mm、600mm)、桩径不同(35mm、45mm)、桩距不同(3倍桩径、4倍桩径),设计3类9组试验,并增设天然地基作为对照组。2、研究长短桩复合地基室内试验的沉降变形特性,分析长短桩复合地基的任一位置处的沉降以及复合加固区、单桩加固区和下卧层的压缩变形量随着长桩长度、桩径、桩距变化,得到以下规律:(1)长短桩复合地基中任一位置处的沉降均随荷载的增加而增大,沉降初期增大速率较为缓慢,后期会有提高。(2)加载完毕系统稳定后的沉降随着深度的增加而减小,且沉降减小的速率也在减小;(3)增加长桩长度可对沉降起到良好的控制作用,但该控制作用会随着深度加深而减弱,增加桩径和减小桩距也有这种作用。(4)随着荷载的增加,复合加固区、单桩加固区和下卧层三个区域的压缩变形量均在增大。加载完成系统稳定后,三个区域的压缩变形量的规律为:单桩加固区最大,复合加固区次之,下卧层最小。(5)改变长桩长度、桩径、桩距均会对复合加固区压缩变形量、单桩加固区压缩变形量和下卧层的压缩变形量带来影响,且影响程度各有不同。3、采用FLAC3D软件对长短桩复合地基沉降变形特性进行模拟分析,得出:长短桩复合地基能够有效控制地基整体沉降和差异沉降。利用控制变量法,分别改变长桩长度、桩径和桩距,对长短桩复合地基的沉降变形规律和最大荷载下不同深度处的沉降变形特性的进行模拟分析,其结果与试验结果一致。4、利用灰色关联分析方法,对影响沉降变形特性的四个因素按影响程度大小排序为:上部荷载桩距桩径长桩长度。
[Abstract]:Long-long pile composite foundation is a new type of composite foundation in geotechnical engineering field. A large number of engineering practices have proved the superiority and safety of this method. Not only to meet the requirements of bearing capacity, but also to control the settlement and deformation. At present, there is less research on the settlement and deformation law of long-long pile composite foundation, and the theoretical support is insufficient. Therefore, the further research is not only the important premise of the development of composite foundation theory, but also the urgent need of the engineering community. This paper takes the actual project of long-long pile composite foundation in Langfang, Hebei Province as the prototype. Based on the project of National Natural Science Foundation of China, "study on settlement and deformation characteristics and Prediction method of Composite Foundation with Composite piles under rigid Foundation". The settlement and deformation law of rigid long-long pile composite foundation is studied and discussed by scale model test in laboratory. The numerical simulation and comparative analysis of the model test are carried out by using FLAC3D software. The grey relational analysis method is used to synthetically consider and rank several main factors affecting the settlement and deformation characteristics in order to provide reference suggestions for the design of long-long pile composite foundation. The following research work: 1 is completed. There are nine prefabricated concrete piles (5 long and 4 short), and the model test box specification is (long? Wide? High 2000mm? 1500mm? 1500mm, and the settlement scale is embedded at the specific position of the composite foundation to detect the internal compression deformation of the composite foundation. According to the length of the long pile, it is 500mm / 550mm / 600mm). Three types of 9 groups of tests were designed, and natural foundation was added as the control group (2. 2). The diameter of pile was 35 mm / 45 mm and the distance of pile was 3 times (3 times) and 4 times (diameter of pile). The settlement and deformation characteristics of long-long pile composite foundation are studied in laboratory test. The settlement at any position of long-short pile composite foundation and the composite reinforcement zone are analyzed. The compression deformation of single pile consolidation zone and subhorizontal layer with the length of long pile is analyzed. The settlement at any position of the long-long pile composite foundation increases with the increase of the load, and the initial increase rate of settlement is relatively slow. After loading, the settlement decreases with the increase of depth, and the rate of subsidence decreases. 3) increasing the length of long pile can control the settlement well, but the control effect will weaken with the deepening of the depth, and the increase of pile diameter and the decrease of pile spacing will also play this role with the increase of load. The compression deformation of the composite reinforcement zone, the single pile reinforcement area and the horizontal layer is increasing. After the system stability is completed, the law of the compression deformation in the three areas is: the single pile reinforcement area is the largest. The length of long pile, the diameter of pile and the distance of pile will affect the compression deformation of composite reinforcement zone, the compression deformation of single pile reinforcement area and the compression deformation of subhorizontal layer. And the influence degree is different. 3. FLAC3D software is used to simulate the settlement and deformation characteristics of long-long pile composite foundation. It is concluded that the long pile composite foundation can effectively control the whole settlement and differential settlement of the foundation. By using the control variable method, the length, diameter and distance of the long pile are changed respectively. The law of settlement and deformation of long-long pile composite foundation and the characteristics of settlement and deformation at different depths under maximum load are simulated and analyzed. The results are consistent with the experimental results. 4. The grey correlation analysis method is used. According to the degree of influence, the four factors affecting settlement and deformation characteristics are listed as follows: the length of pile between the upper load and the diameter of the pile.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU433

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