Quality Control Measures of Bored Pile in Bridge Construction

In order to improve the quality of bored piles in bridge construction and ensure the overall quality of the bridge,we analyzed a series of problems in the construction process of bored piles,then propose corresponding quality control measures,in hopes of improving quality control of bored piles in bridge construction in our country.

Regressive approach for predicting bearing capacity of bored piles from cone penetration test data

In this study, th e least sq u are su p p o rt v ecto r m achine （LSSVM） alg o rith m w as applied to predicting th ebearing capacity o f b ored piles e m b ed d ed in sand an d m ixed soils. Pile g eo m etry an d cone p e n e tra tio nte s t （CPT） resu lts w ere used as in p u t variables for pred ictio n o f pile bearin g capacity. The d ata u se d w erecollected from th e existing litera tu re an d consisted o f 50 case records. The application o f LSSVM w ascarried o u t by dividing th e d ata into th re e se ts： a train in g se t for learning th e pro b lem an d obtain in g arelationship b e tw e e n in p u t variables an d pile bearin g capacity, and testin g an d validation sets forevaluation o f th e predictive an d g en eralization ability o f th e o b tain ed relationship. The predictions o f pilebearing capacity by LSSVM w ere evaluated by com paring w ith ex p erim en tal d ata an d w ith th o se bytrad itio n al CPT-based m eth o d s and th e gene ex pression pro g ram m in g （GEP） m odel. It w as found th a t th eLSSVM perform s w ell w ith coefficient o f d eterm in atio n , m ean, an d sta n d ard dev iatio n equivalent to 0.99,1.03, an d 0.08, respectively, for th e testin g set, an d 1, 1.04, an d 0.11, respectively, for th e v alidation set. Thelow values o f th e calculated m ean squared e rro r an d m ean ab so lu te e rro r indicated th a t th e LSSVM w asaccurate in p redicting th e pile bearing capacity. The results o f com parison also show ed th a t th e p roposedalg o rith m p red icted th e pile bearin g capacity m ore accurately th a n th e trad itio n al m eth o d s including th eGEP m odel.

A case study on behaviors of composite soil nailed wall with bored piles in a deep excavation

深挖掘的一个完全的盒子被探索。根据实际工作条件， 3D 非线性的有限元素过程被用来模仿合成土壤支持的深挖掘有在软土壤的无聊的堆积的钉的墙。修改凸轮泥土模特儿在数字模拟作为土壤的组成的关系被雇用。从数字分析的结果与领域数据被适合很好，它显示使用的研究途径是可靠的。基于数据和钉的合成土壤的四个不同模式支持的深挖掘的数字结果围的地，重要角落效果深在 3D 被成立挖掘。如果无聊的堆积或土壤锚在钉的合成土壤被认为墙，他们对减少的变丑和在深挖掘附近的无聊的堆积，混合堆积的水泥，土壤锚，土壤钉和土壤的内部力量有益。而且，效果由于无聊的堆积比从土壤锚推出的那些更重要。上面提及的所有证明合成土壤与无聊的堆积钉了墙在深挖掘是可行的。

Comparative Examinations of Single Bored Piles Using International Codes

This paper presents some aspects of the load-settlement behavior for large diameter bored piles using four different international codes, namely: ECP 202 [1], DIN 4014 [2], AASHTO [3] and French Code [4]. Ultimate capacities for 38 pile load tests founded in realistic multi-layered soils in Delta and Port Saidareas atEgyptare evaluated using modified Chin (1970) method and compared to ultimate load predictions obtained by the aforementioned codes. Many statistical analyses were conducted on the total pile loads and individual contributions of tip and skin resistances. Based on code predictions of ultimate pile loads, an empirical modified load-settlement model is proposed. This model will simplify to a great extent the analysis of piled-raft systems as it can effortlessly predict pile settlement due to the load on pile itself. Comparisons showed that the pile load test is an irreplaceable process for determining the ultimate capacity of piles.

Dynamic estimation and reliability control of quality assurance for bored piles

A systematic method was proposed to estimate the occurrence probability of defective piles(OPDP) from a site according to quality assurance inspection. The OPDP was firstly suggested as the criterion to weight the performance of a pile foundation. Its prior distribution and updating distribution were deduced to follow Beta distributions. To calibrate the OPDP, a dynamic estimation model was established according to the relationships between prior mean and variance and updating mean and variance. Finally, a reliability-control method dealing with uncertainties arising from quality assurance inspection was formalized to judge whether all the bored piles from a site can be accepted. It is exemplified that the OPDP can be substantially improved when more definite prior information and sampling formation become available. For the example studied herein, the Bayesian estimator of updating variance for OPDP is reduced from 0.0037 to 0.0014 for the first inspection, from 0.0014 to 0.0009 for the second inspection, and with less uncertainty by incorporating experience information.

Evaluation of the Ultimate Capacity of Friction Piles

The precise prediction of maximum load carrying capacity of bored piles is a complex problem because the load is a function of a large number of factors. These factors include method of boring, method of concreting, quality of concrete, expertise of the construction staff, the ground conditions and the pile geometry. To ascertain the field performance and estimate load carrying capacities of piles, in-situ pile load tests are conducted. Due to practical and time constraints, it is not possible to load the pile up-to failure. In this study, field pile load test data is analyzed to estimate the ultimate load for friction piles. The analysis is based on three pile load test results. The tests are conducted at the site of The Cultural and Recreational Complex project in Port Said, Egypt. Three pile load tests are performed on bored piles of 900 mm diameter and 50 m length. Geotechnical investigations at the site are carried out to a maximum depth of 60 m. Ultimate capacities of piles are determined according to different methods including Egyptian Code of practice (2005), Tan-gent-tangent, Hansen (1963), Chin (1970), Ahmed and Pise (1997) and Decourt (1999). It was concluded that approxi- mately 8% of the ultimate load is resisted by bearing at the base of the pile, and that up to 92% of the load is resisted by friction along the shaft. Based on a comparison of pile capacity predictions using different method, recommendations are made. A new method is proposed to calculate the ultimate capacity of the pile from pile load test data. The ultimate capacity of the bored piles predicted using the proposed method appears to be reliable and compares well to different available methods.

静钻根植桩竖向承载性能现场试验研究

通过一组现场试验对同一场地内静钻根植桩的抗压和抗拔承载性能进行研究,试桩均加载至极限状态。通过抗压和抗拔静载试验对静钻根植桩的抗压和抗拔承载性能进行对比分析。试验结果表明:静钻根植桩的抗压承载性能相比传统钻孔灌注桩有显著提高,本次试验场地各土层中静钻根植桩的桩侧摩阻力是规范建议的钻孔灌注桩极限侧摩阻力的1.49~3.21倍;静钻根植桩抗拔承载性能也明显优于钻孔灌注桩,抗拔试桩的极限承载力是根据规范计算的钻孔灌注桩极限抗拔承载力的1.52~1.55倍;静钻根植桩抗拔状态下桩侧摩阻力明显小于抗压状态下的桩侧摩擦力,即静钻根植桩也存在侧阻抗拔系数。

静钻根植桩施工环境效应现场试验研究

静钻根植桩采用先钻孔注浆后植桩的施工技术,可以解决传统预制桩施工过程引起的挤土效应问题。然而,静钻根植桩施工过程中钻孔和注浆过程会对周围土体产生一定扰动,目前没有相关研究。文章通过一组现场试验对静钻根植桩施工过程中的钻孔、注浆搅拌和植桩阶段对周围土体的扰动规律进行研究。静钻根植桩施工前在钻孔周围土体中埋设土压力传感器,孔隙水压力传感器和测斜管,分别测试静钻根植桩施工过程中周围土体中水平土压力,超静孔隙水压力和深层土体水平位移的变化规律。研究结果表明:静钻根植桩施工过程会对周围土体造成一定扰动,而施工完成后周围土体中的水平土压力、超静孔隙水压力和深层土体水平位移迅速恢复;当水平距离达到4D(D为钻孔直径)时,静钻根植桩施工过程基本不会对土体产生影响;试验结果可以为静钻根植桩在地铁周围等施工位移控制敏感区域的应用提供理论依据。

钻孔灌注桩数字化施工技术及应用

随着钻孔灌注桩向超孔深、超大直径方向发展,其施工控制难度也显著增加。传统施工工艺高度依赖人工对施工参数进行采集和记录,难以满足精细化施工管控的要求。为了保证超长大直径桩施工质量,以双柳长江大桥北主塔桩基施工为依托工程,对钻孔灌注成孔、成桩关键施工参数及采集方式进行分析,并针对成孔、成桩过程的关键参数进行自动化监测装置的开发与应用。研究结果表明采用数字化技术手段,能有效减少施工过程中人工采集工作量,提升钻孔灌注桩施工精细化管控水平,可供类似工程借鉴。

钻孔灌注桩技术在房建工程施工中的应用

为深入探究钻孔灌注桩技术在房建工程施工中的应用,结合某房屋建筑工程对钻孔灌注桩技术的实际应用进行深入探究,经过研究表明钻孔灌注桩技术在房屋建筑工程中应用能够显著提升房建工程施工质量和效率,保证了工程施工阶段的安全性与规范性,对建筑工程具有显著的积极作用。

市政路桥工程的钻孔灌注桩施工技术分析

对市政路桥工程的钻孔灌注桩施工工艺进行分析,探讨市政路桥工程的钻孔灌注桩施工应注意的问题,如护筒下沉、钻孔倾斜、坍孔缩孔、断桩,结合工程案例对市政路桥施工中钻孔灌注桩施工技术的应用进行详细介绍。

岩溶强发育及超厚回填土地层钻孔灌注桩施工技术

针对复杂地层中钻孔灌注桩常见的施工问题,以某工程项目为例,基于岩溶强发育及超厚回填土地层钻孔灌注桩施工技术,对超厚回填土地层、岩溶强发育地层以及上覆超厚回填土与下伏岩溶强发育叠加地层3种不同工况进行了应用分析,结果表明:该技术有效解决了复杂地层中成孔难、易扩缩径、灌注难等诸多工程难题,相较于传统工艺,可大大节省施工材料、降低施工成本,为项目缩短工期15天,累计节约旋挖钻机30台班,将灌注桩充盈系数从1.5降至1.05~1.1,为项目桩基施工节约综合成本35%以上。根据低应变检测结果可知,灌注桩均为Ⅰ,Ⅱ类桩,其中Ⅰ类桩占所测桩数的96.5%,Ⅱ类桩仅占所测桩数的3.5%,充分证明了该技术的可靠性。

钻孔灌注桩竖向承载性能试验研究

为优化提升钻孔灌注桩的设计方案,文中对竖向受压载荷下钻孔灌注桩的荷载传递及受力特性进行了研究。结果表明,最大的桩身轴力均位于深度为3 m处,当加载荷载为1440 kN时,桩身的轴力最大值为1205 kN;随着桩顶荷载值的增加,桩身的最大桩侧阻力值也不断增大,最大的桩侧阻力值为140 kPa,最大负摩阻力达到-82 kPa。当桩顶荷载从160 kN增加至1600 kN时,桩端阻力增幅达到860.2%。桩端阻力占比与施加的桩顶荷载呈先负相关后正相关关系;当荷载达到1600 kN时,桩顶位移最大达到14.6 mm;卸载为0时,桩顶位移为8.8 mm。

钻孔灌注桩孔壁稳定性影响因素的研究进展

孔壁稳定性是制约钻孔灌注桩成桩质量的关键因素。将影响孔壁稳定性的因素分为桩孔设计参数、施工工艺和土体性质。在桩孔设计参数中,孔径和孔深是影响孔壁稳定的关键因素。施工工艺中,泥浆相对密度、护筒深度和成孔时间是影响孔壁稳定的关键因素。土体性质中,土体类别和土体物理力学性质是影响孔壁稳定的关键因素。针对各关键因素提出相应的管控措施。在桩孔设计参数方面,选取合适钻具,精确控制孔径和孔深。在施工工艺方面,基于孔壁稳定和经济性选择合适的泥浆相对密度和护筒深度,合理安排施工组织,缩短成孔和灌注间隔时间,严格把控钻进速度和钻具压力。在土体性质方面,重点关注软弱地层和砂土层,采用地基处理、加深护筒和增加泥浆相对密度等措施保证孔壁稳定性,为钻孔灌注桩的设计和施工提供参考。

某市市域铁路基坑支护设计案例分析

开展基坑支护既要考虑支挡岩土体,又要形成有效的止水帷幕。某地下基坑支护工程采用钻孔灌注排桩+两道钢筋砼内支撑,在被动区采用三轴水泥搅拌桩加固土体的支护体系,对该基坑计算参数和施工要点进行分析,为类似基坑工程提供参考,进一步提高基坑发展水平。

基于动态监测模型的钻孔灌注桩安全施工技术研究

为发现施工区域内可能存在的孤石障碍物,提前拟定钻孔位置和安全可行的施工方案;通过构建基于预警监测系统数据的遗传算法预测模型,实现预警以确保钻机钻进过程的顺利和周边环境的安全。结果表明:通过BP神经网络建立的预测模型成功预测了障碍物位置和性质,在地质特征和障碍物预测方面具有较高的准确性;结合不良地质预报和障碍物预测技术对于钻孔灌注桩施工具有重要影响。

钻孔灌注桩智能化施工管控技术应用研究

钻孔灌注桩具有承载力高、实用性强、强度刚度大等优点,但作为典型的隐蔽工程,存在管控内容繁多、修复难度大、质量监测难等问题。通过对钻孔灌注桩施工关键工序进行梳理分析,确定开孔孔位、桩径、垂直度、孔深、沉渣厚度、泥浆比重等作为重点管控内容,提出了适用于钻孔灌注桩施工中的智能化管控技术,以期为钻孔灌注桩施工提供新的管控方式与研究方向。

房屋建筑工程钻孔灌注桩施工技术应用研究

介绍了钻孔灌注桩施工技术的基本机理、步骤,以及其应用领域与效果,从施工准备、钻孔工艺、混凝土灌注、成桩质量控制等方面详细分析了钻孔灌注桩施工技术的要点,从而提高钻孔灌注桩的施工技术水平,保证建筑工程的施工质量。

桥梁项目中钻孔灌注桩施工技术应用

首先分析了钻孔灌注桩施工技术特点,其次结合实际工程案例,从施工准备、场地整平放样、制备泥浆、埋设护筒、钻孔等多方面分析桥梁项目中钻孔灌注桩施工技术,并同时提出该技术应用的质量控制措施,以期能够有效提高桥梁项目的整体质量。

不良地质中粗砂层钻孔灌注桩施工质量的控制研究

结合城市人行天桥工程项目实例,着重分析不良地质中粗砂层钻孔灌注桩施工质量的控制,主要包括双层钢护筒设计、特殊桩位钢护筒加长、钢护筒埋深、钢护筒拔出等质量控制措施。根据现场实际地质情况,编制合理的施工方案,结合EPC项目特点,确保施工费用有效控制,施工质量管控到位以及合同按期履约。