北京市某超高层建筑基础灌注桩后压浆技术的研究与应用

发布时间：2018-03-13 05:10

本文选题：超高层建筑　切入点：大直径灌注桩　出处：《吉林大学》2013年博士论文　论文类型：学位论文

【摘要】：我国自20世纪后半叶，特别是从20世纪最后20余年至21世纪前十年以来，由于国民经济持续高速增长，基本建设投资规模不断升级，而建设场地的地质条件和环境条件却日趋复杂，因而使深基础尤其是桩基础的应用、研究与发展达到了前所未有的程度。灌注桩后压力注浆是指在钻孔、挖孔和冲孔等各种形式的灌注桩成桩之后，通过埋设在桩身或桩周的注浆管，将能够固化的浆液(如纯水泥浆、水泥砂浆、掺外加剂的水泥浆、化学浆液等)均匀地注入桩端底层或桩身周围的土体中。浆液经过渗透、填充、置换、劈裂、压密及固结等物理或化学形式的单独或共同作用，改变了桩端及桩侧周围土体的物理力学性质，使桩端阻力和桩侧阻力得到不同程度的提高，使桩的沉降量得以减小，桩的承载能得到提高。合理工艺的后注浆不但可以提高单桩承载而且可以减小桩的沉降量和群桩的不均匀沉降，具有显著的经济效益。近十几年来，高层建筑及超高层建筑在我国的广泛兴起，使大直径钻孔灌注桩得到大量应用，特别是在沿海地区，需要承载力高且承载性能稳定的桩基础，同时要满足沉降量的要求，给桩基础设计提出新的课题。桩端（侧）后压浆钻孔灌注桩可以满足大型建筑物对承载力的要求，，同时在满足工程应用的条件下，利用桩端（侧）后压浆桩承载力高的特点，可以考虑减少桩的数量，那么在布置桩的平面位置时可以增加桩的间距，从而减小群桩效应。由于桩端（侧）后压浆钻孔灌注桩在工作荷载作用下变形很小，因而可以减小高层建筑中主楼与裙房之间的差异沉降。在建设场地存在良好桩端持力层的前提下，运用桩端（侧）后压浆工艺势必给高层建筑的发展带来新的活力。随着现阶段国内建设工程的逐步发展，国家及人们对建设事业的逐渐支持，大量建设工程正在得到施工。灌注桩后压浆法能适用各种复杂地质条件的地基基础施工，应用市场十分巨大。通过对灌注桩后压浆法在桩基础施工中的应用进行深入系统研究，对桩基础施工的安全性和经济性具有十分重要的社会效益和经济效益，对推动压浆技术和桩基础加固技术的发展也有着极为重要的作用，其应用价值体现在以下几个方面。 ⑴继承了普通灌注桩的所有优点，适用各种地质条件、无振害、无噪声等等。 ⑵创造性地提出并实现了桩底桩侧压力灌浆的施工工艺，使得单桩承载力与相同直径和长度的普通灌注桩相比，提高幅度很大。因此大大缩短了桩的设计长度，降低了施工费用，经济效益十分明显。 ⑶沉降量大大减少，适用于上部结构对沉降比较敏感的工业建筑和机械设备基础等。 ⑷桩侧压力灌浆既使桩侧的泥皮与土进行了混合与挤密处理，又使土体与桩身混凝土联结成整体，浆液硬化后的结石还会在桩侧形成楔体。这些都会使桩与土之间的磨擦面积增大，提高侧摩阻力。这一优势可以更广泛地应用在抗拔桩设计当中。灌注桩后压浆法在提高桩基承载力中的理论分析，压浆（灌浆）加固地基土的作用有三点：渗透、挤密、劈裂。后压浆对单桩承载力的提高取决于后压浆技术的工艺参数的选择，其中以后压浆材料的选用、后压浆压力的允许值、后压浆的压浆量的多少以及后压浆的时间间隔等参数最为关键。文中通过对北京市超高层建筑财富中心Ⅱ期的建筑的工程场区的地质地震、地形周边、区域水文地质条件、场地与地基的地震效应以及地基综合承载力标准值等因素的充分分析评价，研究分析该工程建筑场区在岩土工程勘察中出现的相关问题，提出相应的基础方案及结构施工措施来解决高层主塔楼和纯地下室之间的差异沉降问题，提出大直径钻孔灌注桩方案并采取可靠的桩端、桩侧后压浆工艺，提高基桩承载力，以满足该工程的地基基础以及整体稳定性的要求。本文借助通用有限元软件ANSYS12.0建立桩—土体系的结构模型，模拟静载荷试验过程，从而确定注浆前和注浆后对于不同地层，不同桩长的大直径灌注桩的承载力提高以及位移沉降。最终以第1○12层中砂和卵石层作为本工程桩端持力层，采用该方案时应根据该地区建筑工程水下钻孔桩的设计与施工经验，采取可靠的桩端、桩侧后压浆工艺（压浆工艺是指在灌注桩成桩后，采用高压注浆泵通过预埋于桩底或桩侧的压浆导管向桩底或桩侧高压注入水泥浆液，通过浆液的劈裂、填充、压密、固结等作用，塞实桩底的松软土质，达到固结底泥和挤压土层的目的；同时浆液沿桩侧向上返浆扩散，加强土层与桩体的侧摩阻力，在软土地基条件下，可改善钻孔灌注桩成桩工艺，提高单桩承载力、抗摩擦力、减少工程沉降量），并须满足设计要求。不但能够提高成孔、成桩质量，而且可消除孔底沉渣、孔壁泥皮影响，维持孔壁稳定，从而提高基桩承载能力并减少桩基沉降。工程结束后通过单桩承载力静压试验、声波透射实验和抗压桩低应变检测试验，都充分证明了在相同条件下，采用桩底桩侧后压浆的灌注桩，无论从单桩承载力、或是桩身完整性及桩身应变降低都有极大的提高。并且在一定程度上，桩底桩侧后压浆方法降低了大直径灌注桩原有的某些施工缺陷，确保了桩身的完整性。超高层建筑大直径灌注桩后压浆技术涉及的因数较多，实际工程中各种因数往往是综合存在和相互作用的，本文仅仅针对某一固定地区超高层建筑大直径灌注桩后压浆效果和计算方法做了初步研究。广泛收集工程资料，总结实际工程应用中的成果，将实践经验上升为系统的理论，来更有效地指导工程实践，仍是今后主要的研究方向。
[Abstract]:Our country since the second half of the twentieth Century, especially from twentieth Century to twenty-first Century before the last 20 years since ten years, the national economy has maintained rapid growth, the scale of investment in infrastructure upgrades, and construction of geological and environmental conditions are becoming increasingly complex, so that the deep foundation especially the application of pile foundation, research and development to achieve a hitherto unknown degree.
After pouring pile pressure grouting is in drilling, after digging holes and punching various forms of pouring pile by grouting, buried in the pile or pile pipe, will be able to slurry (such as pure cement slurry, cement mortar, cement, admixture of chemical grout etc.) evenly into the soil around the end of pile bottom or pile. After slurry infiltration, filling, replacement, splitting, alone or in interaction of compaction and consolidation in physical or chemical form, change the physical and mechanical properties of the soil around the pile and pile, the pile tip resistance and lateral resistance of the pile are improved to varying degrees, the settlement of pile can be reduced, the bearing capacity of pile can be improved. The reasonable process of post grouting can improve pile bearing capacity and reduce the settlement of pile and pile group settlement, has significant economic benefits.
In recent years, high-rise buildings and high-rise buildings in the rising of our country, the large diameter bored pile has been widely used, especially in the coastal areas, to the bearing capacity of pile foundation bearing capacity and high stability, and to meet the settlement requirements for pile foundation design of pile raised new issues. End (side) of post grouting bored pile can meet the requirements of bearing capacity of large buildings, at the same time satisfy the engineering conditions, the pile end (side) characteristics of post grouting pile with high bearing capacity, can consider reducing the number of piles, then the position in the plane layout of the pile pile can be increased distance, so as to reduce the effect of pile group. The pile end (side) of post grouting bored pile under working load deformation is small, so it can reduce the difference between the main building and the podium in the high-rise building settlement. The bearing layer in the construction site has good pile end Under the premise of the use of pile end (side) post grouting technology will bring new vitality to the development of high-rise buildings.
With the gradual development of the domestic construction of the country and people gradually support for the construction of large construction projects are obtained. The construction foundation construction of bored pile post grouting method can be applied to various complex geological conditions, the application market is huge. The systematic study on the application of the post grouting method in pile foundation in the construction, safety and economy of pile foundation construction has very important social and economic benefits, to promote the development of technology of grouting and pile foundation reinforcement technology also plays a very important role, its value is reflected in the following aspects.
It inherits all the advantages of ordinary pile, the applicable conditions of various geological, no damage, no noise and so on.
The proposed construction technology of pile pressure grouting pile bottom, the pile bearing capacity of single pile with the same diameter and length, improves greatly. It can greatly shorten the design length of pile, reduce the construction cost, obvious economic benefit ten.
The settlement is greatly reduced, is suitable for the superstructure to the settlement of sensitive industrial buildings and machinery and equipment base.
The pile pressure grouting pile side mud and even were mixed with soil compaction, the soil and the pile concrete connection as a whole, but also the formation of hardened slurry stone wedge on the pile. All of these will make the friction area between the pile and soil increases, improve this side friction. One advantage can be widely used in the design of uplift piles.
The theoretical analysis of the post grouting method in improving the bearing capacity of pile foundation has three points: infiltration, compaction and splitting.
The increase of post grouting to the bearing capacity of a single pile depends on the selection of technological parameters of post grouting technology. After that, the most important parameters are the selection of grouting material, allowable value of post grouting pressure, post grouting pressure and the time interval of post grouting.
In this paper, through the geological earthquake in Beijing City, the center of wealth II high-rise building construction engineering field surrounding terrain, hydrogeological conditions, ground and foundation earthquake effect and the foundation of the comprehensive analysis and evaluation of bearing full strength standard value and other factors, analysis of issues related to the engineering construction area in geotechnical engineering in the survey, put forward corresponding scheme and construction measures to resolve the differences between the main tower and pure basement settlement, the large diameter bored pile scheme and the use of reliable pile, pile lateral grouting technology, improve pile bearing capacity, to meet the requirements of the engineering foundation and overall stability.
This paper uses the structural model of general finite element software ANSYS12.0 to establish the pile-soil system, simulate the static load test process, so as to determine the grouting before and after grouting for different strata, different pile length of large diameter pile bearing capacity and settlement displacement. At the end of first, the 12 layer of sand and gravel as the pile at the end of the bearing layer, the use of the program should be based on the experience of design and construction of bored pile construction in the area of water, adopt reliable pile, pile lateral Grouting Technology (grouting technology refers to grouting conduit by high-pressure grouting pump in bored pile after pile, through pre buried in the pile bottom or pile the side to the bottom of the pile or pile of high pressure injection of cement slurry, the crack, split slurry filling, compaction, consolidation, plug solid pile bottom spongy soil, sediment and soil consolidation to squeeze the purpose; at the same time slurry along the pile lateral slurry return and diffusion. The side friction resistance strong soil and pile, under the condition of soft soil subgrade, can improve the cast-in-place pile technology, improve the bearing capacity of single pile, anti friction, reduce the engineering settlement), and shall meet the design requirements. Not only can improve the quality of pile hole, it can eliminate the hole bottom sediment. The hole wall of mud, to maintain the stability of hole wall, so as to improve the pile bearing capacity and reduce the settlement of pile foundation.
After the end of the project through the static test of single pile bearing capacity, acoustic transmission experiment and compressive pile low strain testing, have fully proved that under the same conditions, the pile pile bottom post pressure grouting pile, both from the bearing capacity of single pile, or the integrity of pile and pile strain decrease are greatly improve. And to a certain extent, the bottom of the pile and pile lateral grouting method reduces the large diameter bored pile construction of some of the original defects, ensure the integrity of the pile body.
There are many factors involved in the pressure grouting technology in high-rise building large diameter bored pile in practical engineering, various factors are often integrated with the presence and interaction, this is only for the high-rise building large diameter bored pile in a fixed area after the grouting effect and calculation method to do a preliminary research. The extensive collection of engineering data, summarizes the practical engineering application the results will experience up to the theoretical system, to more effectively guide the engineering practice, the main research direction in the future is still.

【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TU753.3

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