新世界会展中心大直径桩检测及数值模拟分析

发布时间：2018-05-22 18:53

本文选题：大直径桩 + 静载试验　；参考：《昆明理工大学》2010年硕士论文

【摘要】：随着我国基本建设事业的迅速发展,桩基础在高层建筑、重型厂房、桥梁、港口码头、海上采油平台以及核电站等工程中应用广泛。桩基础朝着大直径高承载力的方向发展,大直径桩的检测也越来越重要。本文依托沈阳新世界会展中心一期试桩检测工程,该桩桩径0.85m、桩长52.0m、长径比为56～62属大直径长桩。由于此前本地区未有类似的工程,施工及检测经验缺乏,需通过试验结果来验证设计,以保证工程质量。本文采用目前最直接、最可靠的检测方法--基桩静载试验法进行承载力测定,得出的Q-s曲线为缓变型,且该工程中桩的长度变化并没有引起桩的Q-s曲线发生太大的波动,表明增加桩长对于承载力的提高不明显,还不利于沉降控制。若要改进设计需综合考虑桩长、桩径,选择合适的长径比。可适当缩短桩长至44m,改变长径比以便发挥端阻作用、降低成本。并针对该地区的地层结构近似地将该地区的砂土地基视为同一介质的地基。通过回归分析得出了Y=A+B×X公式和A=C+D×L；B=C+D×L公式,能有效描述该地区类似土层介质条件下桩身轴力与深度变化关系,对本地区或类似的工程有一定的借鉴作用。针对成桩过程中可能出现断桩、离析等情况的缺陷桩。经过与其他完整性检测方法的对比,选择了适合于本工程桩身的完整性检测的方法—低应变反射波‘法。该法具有快速、经济、可大面积普查等特点。由于现场的检测条件复杂,影响因素较多,难以得到非常标准的完整检测波形,本文采用了通过联系地质情况分析实测波形的方法对其桩身完整性类别作出了判断,综合判别为Ⅰ类桩。因现场试验用桩均为工作用桩,不可以也不可能进行破坏性试验,因而本文运用FLAC 3D(三维快速拉格朗日法)对桩进行了破坏性模拟分析,采用结合地质报告提供的力学参数以模拟结果与桩承载试验结果基本一致为原则,并将模拟结果与实测数据进行比对,对参数不断调整,最终确定了与实际相近的模拟参数。以此进行桩极限承载数值模拟,得到了桩的极限承载力,并提出了后压浆及扩大头的优化设计方案,同时对该方案进行数值模拟,所得结果表明可以缩短桩长、减小钢筋用量、节省了工程费用。并为本地区类似桩基工程的设计和施工提供了一定的参考依据。
[Abstract]:With the rapid development of capital construction in China, pile foundation is widely used in high-rise building, heavy plant, bridge, port wharf, offshore oil recovery platform and nuclear power plant. The pile foundation is developing towards the direction of large diameter and high bearing capacity, and the detection of large diameter pile is becoming more and more important. This paper relies on the first phase test pile test project of Shenyang New World Convention and Exhibition Center. The pile diameter is 0.85 m, pile length is 52.0 m, and the ratio of length to diameter is 560.62 belong to large diameter long pile. Due to the lack of construction and testing experience in this area, the design should be verified by test results to ensure the quality of the project. In this paper, the most direct and reliable testing method, the static load test method of foundation pile, is used to measure the bearing capacity. The Q-s curve obtained is of a slowly modified type, and the change of pile length in the project does not cause too much fluctuation of the Q-s curve of the pile. It shows that the increase of pile length is not obvious for the increase of bearing capacity and is not conducive to settlement control. In order to improve the design, it is necessary to consider the pile length and diameter and choose the appropriate ratio of length to diameter. The length of the pile can be shortened to 44m and the aspect ratio can be changed in order to play the role of end resistance and reduce the cost. According to the stratigraphic structure of this area, the sand foundation in this area is regarded as the foundation of the same medium. By regression analysis, the formulas of Ya A B 脳 X and A C D 脳 L are obtained, which can effectively describe the relationship between the axial force and the depth of the pile under the condition of similar soil layer in this area, and can be used for reference in this area or similar projects. The defect pile may appear in the process of pile formation, such as broken pile, segregation and so on. By comparing with other integrity detection methods, the method of low strain reflected wave is selected for the integrity detection of pile body in this project. The method has the characteristics of fast, economical and large area census. Because of the complex testing conditions and many influencing factors on the spot, it is difficult to obtain a very standard complete detection waveform. In this paper, the integrity of pile body is judged by the method of analyzing the measured waveform by connecting with the geological conditions. Comprehensive discrimination is classified as class I pile. Because all the piles used in field test are working piles, it is not possible and impossible to carry out destructive tests. In this paper, FLAC 3D (three dimensional fast Lagrangian method) is used to simulate and analyze the damage of piles. The mechanical parameters provided by the geological report are taken as the principle that the simulation results are basically consistent with the pile bearing test results, and the simulation results are compared with the measured data, the parameters are adjusted continuously, and the simulation parameters close to the actual ones are finally determined. The ultimate bearing capacity of pile is obtained by numerical simulation, and the optimum design scheme of post-grouting and enlarged head is put forward. The results show that the length of pile can be shortened and the amount of steel bar can be reduced. The cost of the project was saved. It also provides some reference for the design and construction of similar pile foundation engineering in this area.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2010
【分类号】：TU473.16

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