支撑桩加承台的斜抛撑支护体系在深大基坑中的应用研究

发布时间：2018-06-16 22:40

本文选题：深基坑工程 + 斜抛撑　；参考：《哈尔滨工业大学》2015年硕士论文

【摘要】：紧邻既有建筑物地下室的深基坑工程越来越多,传统的桩锚支护体系在深基坑施工空间上受到限制,而斜抛撑支护体系由于布置灵活,可以不受用地红线、基坑周围建(构)筑物的影响限制。另外,与整体内支撑结构相比,斜抛撑支护体系方便土方开挖,可以加快施工进度,缩短施工工期,并且造价低,可以节省大量的费用,具有明显的经济效益。本文利用大型通用有限元软件ABAQUS,针对支撑桩加承台的斜抛撑支护体系,采用数值模拟的方法,对该斜抛撑支护体系在深大基坑中的应用进行研究。本文首先验证了ABAQUS对深基坑建立数值模型的方法、步骤和手段是合理的,然后利用ABAQUS对支撑桩加承台的斜抛撑在工程实例中的应用建立了数值模型,将数值模拟得到的支护桩向基坑内的水平位移和基坑外地表土体沉降分别与工程实测数据做对比,结果表明各个工况下的支护桩向基坑内的水平位移和坑外地表土体沉降与工程实测数据的曲线趋势相近或一致。表明了该工程实例数值模拟的方法和结果是可行的,验证了ABAQUS有限元软件对支撑桩加承台的斜抛撑支护基坑建立的数值模型方法和步骤是合理的。针对支撑桩加承台的斜抛撑支护体系在第2章工程实际中的应用,本文利用ABAQUS有限元软件重点分析了斜抛撑及承台下两个支撑桩的受力特点。并将斜抛撑与水平对撑作用下基坑变形进行对比,结果表明支撑桩加承台的斜抛撑支护体系对抑制基坑底部土体隆起具有显著的作用,但这种抑制基坑底部土体隆起的范围是一定的(约为基坑底部距支护桩的水平距离23 m),超出了这一范围,支撑桩加承台的斜抛撑支护体系抑制基坑底部土体的隆起效果不明显。结果还显示,虽然斜抛撑支护体系作用下的支护桩向基坑内的水平位移和坑外地表土体沉降均大于水平对撑作用下相对应的值,但在斜抛撑支护体系的作用下,支护桩向基坑内的水平位移和坑外地表土体沉降均在基坑安全等级要求的警戒值和控制值内,该斜抛撑支护体系能够保证基坑的安全。最后本文利用ABAQUS有限元软件验证了现行设计斜抛撑方法的合理性。本文利用ABAQUS有限元软件进一步对该斜抛撑支护体系的几何参数进行研究,主要进行了斜抛撑在承台上不同支撑点位置、承台下两个支撑桩之间不同间距、斜抛撑与承台和支护桩的不同连接(刚接和铰接)形式、承台下支撑桩的不同桩径及在不同土体参数影响下的数值模拟。通过对比分析在斜抛撑支护体系的不同几何参数影响下,坑外地表土体沉降、支护桩向基坑内的水平位移和坑内底部土体隆起及支护桩、承台下支撑桩的受力特点,得出一些结论,为类似基坑工程项目的设计和施工提供有益的参考借鉴。
[Abstract]:There are more and more deep foundation pit projects close to the basement of existing buildings. The traditional pile-anchor support system is restricted in the construction space of deep foundation pit, while the inclined throwing bracing support system is not subject to the red line of land because of its flexible arrangement. The influence of construction around foundation pit is limited. In addition, compared with the whole internal support structure, the oblique brace support system is convenient for earthwork excavation, can speed up the construction progress, shorten the construction period, and the cost is low, which can save a lot of expenses and have obvious economic benefits. Based on Abaqus, a large scale finite element software, the application of this support system in deep and large foundation pit is studied by numerical simulation. In this paper, the method of establishing numerical model of deep foundation pit by Abaqus is verified, the steps and means are reasonable, and then the numerical model is established by using Abaqus for the application of inclined throwing brace of braced pile and pile cap in engineering example. The horizontal displacement of the supporting pile to the foundation pit and the settlement of the surface soil of the foundation pit obtained by numerical simulation are compared with the measured data of the project respectively. The results show that the horizontal displacement of the supporting pile and the settlement of the surface soil in the pit are similar or consistent with the measured data. It is shown that the numerical simulation method and results of the engineering example are feasible, and the numerical model method and steps of Abaqus finite element software for the foundation pit supported by supporting pile and pile cap are proved to be reasonable. In view of the application of inclined support system of supporting pile with pile cap in chapter 2 engineering practice, the stress characteristics of inclined throwing brace and two supporting piles under pile cap are analyzed in this paper by using Abaqus finite element software. The deformation of foundation pit under the action of oblique brace and horizontal bracing is compared. The results show that the supporting system of inclined throwing bracing with pile and pile cap plays a significant role in restraining the uplift of soil at the bottom of foundation pit. However, the range of restraining the soil uplift at the bottom of the foundation pit is certain (about 23 m / m) from the bottom of the foundation pit to the supporting pile, which is beyond this range, and the effect of the slanting supporting system with supporting pile and pile cap on restraining the uplift of the soil at the bottom of the foundation pit is not obvious. The results also show that, although the horizontal displacement of the supporting pile to the foundation pit and the settlement of the surface soil in the pit under the action of the inclined support system are larger than the corresponding values under the action of the horizontal bracing, but under the action of the slanting brace support system, The horizontal displacement of the supporting pile to the foundation pit and the settlement of the surface soil outside the pit are within the warning value and the control value required by the safety grade of the foundation pit, and the inclined support system can ensure the safety of the foundation pit. Finally, the rationality of the current design of skew support method is verified by Abaqus finite element software. In this paper, the geometric parameters of the inclined brace support system are further studied by using Abaqus finite element software. Different connections (rigid and hinged) of inclined brace with pile cap and supporting pile, numerical simulation of different pile diameter under pile cap and under different soil parameters. Under the influence of different geometric parameters of inclined support system, the settlement of surface soil, the horizontal displacement of supporting pile to foundation pit, the uplift of soil and supporting pile at the bottom of the pit, and the bearing characteristics of supporting pile under pile cap are analyzed. Some conclusions are obtained to provide useful reference for the design and construction of similar foundation pit projects.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU473

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