变径灌注桩竖向承载力影响因素分析.docx

摘要
摘要
随着我国工程建设的发展,变径灌注桩基础越来越多的应用于大(重) 型建(构)筑物,虽然已有资料对变径灌注桩的单粧承载机理有了介绍,但到目前为止,对变径灌注桩这一新粧型的在竖向荷载作用下的沉降规律, 以及其他因素对它竖向承载力大小的影响规律和粧及桩侧、桩底土破坏规律的研究成果还是不够,有待进一步研究。
本文采用数值计算的方法对竖向荷载作用下单粧基础承载性状进行了研究。将研究主体桩身视为弹性体,而桩侧和粧底的土体假定成理想弹塑性材料,根据以往前人对灌注桩的研究经验采用大型有限元软件ANSYS 作为计算工具对变径灌注桩进行模拟计算;针对变径灌注粧的受力特点将计算模型简化为平面轴对称模型,并选用Goodman接触面单元来模拟桩土之间的滑移问题。
本文研究对象是变径灌注粧,它的桩底和桩侧是利用振动杆等向压缩得到的夯实土,同时得到桩侧土对桩的初始侧向应力,文中对桩侧和粧底夯实土不同压缩模量的土层厚度予以了假定。分析内容如下:振动杆头强行施加给土大小不同的侧向压力时,桩的沉降规律;侧向力使桩的承载力提高的原因;侧向力大小对桩的承载力提高多少;当桩只加垫层时,桩底垫层厚度对桩的承载力提高多少和桩的沉降大小影响。
关键词有限元;接触;桩基;变径灌注桩;承载性状
Abstract
With the development of municipal engineering and lots of large-scale Buildings and constructions being built, Variant section cast-in-situ piles are used more and more widely in engineering, and there is some date on bearing behaviors of Vertical load of the Variant section cast-in-situ piles for the practice .but the study on the settlement disciplinarian of the new pile of the Variant section cast-in-situ piles, the carrying capacity change rules and the break rules when other factors are varied, is not enough, the fiirther studies are expected.
The main part studied in this paper, pile body, was considered as elastic body and the soil body of the side and bottom of the pile was assumed as the ideal elastic-plastic material According to the former studies on driven cast-in-place pile,the large-scale finite element analysis software,ANSYS,was used here as the calculation tool for analogy calculation of the variant section cast-in-situ piles cast-in-situ piles. Based on the stress characteristic of the variant section cast-in-situ piles cast-in-situ piles, the calculation model was simplified to plane rotational symmetry model, and Goodman contact surface unit was chose to simulate the slipping between the soil of the side and bottom of the pile*
The object of numerical simulation is Variant section cast-in-situ piles and the soil under or beside the pile is tamped homology in each direction with vibration staff. The thick