桩的无损检测方法

一、前言随着国民经济的迅速发展,大量的基本建设工程在全国各地普遍兴起,在建设过程中不断提出很多岩土力学问题,其中最突出的问题之一就是桩基基础问题。目前各种类型的桩包括打入桩及钻孔灌注桩正在城市高层建筑及其他工程建设中大量被采用,随之而来的桩的质量检测及桩的承载力问题已引起广泛重视,特别是桩的质量检测问题更为引人注意。目前所采用的检测方法其精度及可靠性究竟如何,是人们非常关心的问题。     

桩基静载试验之钢铰线锚杆横梁反力装置测试技术的研究与应用

依据《建筑桩基技术规范》[1](JGJ94-94)和美国《桩基轴向抗压静载标准试验方法》[2](ASTMD1143),探讨了桩基静载试验之钢铰线锚杆横梁反力装置的测试技术,并成功的解决了某外资工地桩基静载试验的技术难题。     

不同流场情况下地下水弥散试验方法分析

针对不同地下水水力梯度进行地下水弥散试验采用不同的方法,直接影响到弥散试验的成功及获取参数的准确性及真实性。其中在不同的水力梯度下采用不同的监测时间间隔监测示踪剂浓度,决定了弥散试验捕捉到示踪剂的初至及峰值的成功机率。同时本项目详细地进行了地下水弥散试验求参过程完整性分析,可做为弥散试验参考实例。     

废旧放射源的检测方法及其应用

根据地勘行业所用放射源的特点，确定了废旧放射源的种类、活度、表面剂量率和表面污染率等参数的检测方法，并将方法应用于对上百个未知放射源进行检测和档案整理，效果较好。     

大直径深长桩泥岩侧摩阻力试验研究——以吉林省龙华松花江特大桥工程试桩为例

泥岩地基中泥岩的桩侧摩阻力设计参数比较缺乏。通过对吉林省龙华松花江特大桥工程试桩的自平衡静载试验分析,并结合室内桩和泥岩接触中型剪切摩擦试验,揭示了该地区泥岩地基中大直径深长灌注桩泥岩侧摩阻力作用机制及承载特征,得出了一些对泥岩地基中钻孔灌注桩的设计和深入研究具有指导意义的结论。结果表明：大直径深长桩桩端阻力分担的荷载只占总承载力的一小部分,属摩擦型桩。自平衡测试中,全风化泥岩侧摩阻力达到173 kPa,强风化泥岩侧摩阻力达到279 kPa,中等风化泥岩侧摩阻力达到336 kPa,实测值较规范参考值大很多。建议在桩基设计时通过室内桩和泥岩接触中型剪切摩擦试验,基于莫尔库伦理论预估泥岩侧摩阻力,为桩基承载力的确定提供参考。     

徐州客运站综合楼主楼嵌岩灌注桩试桩结果分析

当基岩抗压强度较高时,嵌岩灌注桩的承载力往往由桩身材料强度控制。本文通过对徐州客运站综合楼主楼嵌岩灌注桩试桩结果的分析,提出了正确运用《建筑桩基技术规范》（ＪＧＪ９４－９４）和桩身材料力学性质指标确定由桩身材料强度所决定的单桩竖向抗压极限承载力的方法。     

Testing and modeling the behavior of pre-bored grouting planted piles under compression and tension

A group of field tests and three-dimensional finite element simulation were used to investigate the behavior of the pre-bored grouting planted pile under compression and tension; moreover, a group of shear tests of the concrete–cemented soil interface was carried out to study the frictional capacity of the pile–cemented soil interface. The load–displacement response, shaft resistance and mobilized base load were discussed based on the measured and computed results. The measured and computed results show that the frictional capacity of the cemented soil–soil interface is better than the frictional capacity of the concrete–soil interface. The frictional capacity of the concrete–cemented soil interface is mainly controlled by the properties of the cemented soil, and the ultimate skin friction of the concrete–cemented soil interface is much larger than that of the cemented soil–soil interface. The frictional capacity of the soil layer close to the enlarged base is also promoted because of the compaction of the enlarged base. The enlarged cemented soil base can promote the behavior of the pile foundation under tension, and the enlarged cemented soil base undertakes approximately 26.3% of the total uplift load under the ultimate bearing capacity in this research.     

复合载体夯扩桩承载性状试验研究

复合载体夯扩桩是由干硬性混凝土及填充料等经细长锤夯扩形成的复合载体和钢筋混凝土桩身组成,具有挤密地基和扩大桩端面积等的作用。分析了复合载体夯扩桩的作用机制,并结合工程实例,采用太沙基公式和规范推荐的理论公式计算了复合载体夯扩桩的极限承载力和沉降量,并与现场静载试验结果相比较。结果表明,理论计算结果比试验结果偏于保守,并提出了相应的改进方法。     

A full-scale field study for performance evaluation of axially loaded large-diameter cylinder piles with pipe piles and PSC piles

This paper presents the results from a pile load testing program for a bridge construction project in Louisiana. The testing includes two 54-in. open-ended spun cast concrete cylinder piles, one 30-in. open-ended steel pile and two (30- and 16-in.) square prestressed concrete (PSC) piles driven at two locations with very similar soil conditions. Both cone penetration tests (CPTs) and soil borings/laboratory testing were used to characterize the subsurface soil conditions. All the test piles were instrumented with vibrating wire strain gauges to measure the load distribution along the length of the test piles and measure the skin friction and end-bearing capacity, separately. Dynamic load tests were performed on all test piles at different times after pile installations to quantify the amount of setup with time. Static load tests were also performed on the PSC and open-ended steel piles. Due to expected large pile capacities, the statnamic test method was used on the two open-ended cylinder piles. The pile capacities of these piles were evaluated using various CPT methods (such as Schmertmann, De Ruiter and Beringen, LCPC, Lehane et al. methods). The result showed that all the methods can estimate the skin friction with good accuracy, but not the end-bearing capacity. The normalized cumulative blow counts during pile installation showed that the blow count was always higher for the PSC piles compared to the large-diameter open-ended cylinder pile, regardless of pile size and hammer size. Setup was observed for all the piles, which was mainly attributed to increase in skin frictions. The setup parameters “A” were back-calculated for all the test piles and the values were between 0.31 and 0.41.     

冲击器无损测试的探讨

随着冲击回转钻进技术的迅速发展,许多大专院校、科研单位在研制冲击器的同时,对其性能参数的测试方法,进行了大量的研究。到目前为止,对压力、流量、冲击频率的测试已有一套比较有效的方法。而对冲击功的测试还存在一些问题。例如,无论是冲锤末速度计算法,还是示功图法,都要损坏冲击器,这就给测试工作带来极大的不便。我们在研究MT型冲击器的过程中,对无损测试冲击功方法进行了反复研究。在武汉地院北京研究生部1983年研究的冲击力传感器的基础上,研制成功了MZG型冲击功传感器。     

嵌岩斜桩冲击钻进成桩施工工艺研究

根据温州港状元岙港区化工码头工程的地层条件和码头的特殊要求,其桩基础设计了嵌岩斜桩,斜度1∶5～1∶6。施工中应用冲击成桩施工工艺。通过自行设计的钢护筒导向架控制桩孔斜度、筒柱式空心锤冲击成孔、橄榄球式混凝土灌注导管灌注混凝土等针对性很强的施工措施,顺利圆满地完成了施工任务。通过桩基检测,桩基质量完全满足规范和设计要求。为类似工程的施工提供了宝贵的经验。     

采用综合物探技术勘测岩溶分布的试验研究

本文介绍了采用声波测井、跨孔法、浅层地震法等综合物探勘测新技术勘测坝基岩溶分布与发育的试验结果。     

柔性群桩承台下变截面角桩与地基相互作用的线性分析

对桩侧土及桩端土均采用线性荷载传递函数,同时考虑桩周土所分担的荷载及桩型对桩基荷载传递规律的影响,利用力学理论及微分方程的近似解法—子域法,推导出了柔性群桩承台下变截面角桩与地基相互作用的近似的解析算式,并通过算例将等截面桩桩侧摩阻力和桩身轴力与变截面桩桩侧摩阻力和桩身轴力作了对比,表明改变桩型能提高桩侧摩阻力。为验证本文方法的可行性,将模型试验结果与本文计算结果进行了比较,表明本文方法有较好的精度。     

楔形桩与圆柱形桩复合地基承载性状对比研究

基于剪切位移法,引入Mylonakis & Gazetas桩-土相互作用及Winkler地基模型,导出了复合地基中桩-桩、桩-土及土-土相互作用柔度系数;在此基础上,提出了一种综合考虑桩-土-垫层共同作用的复合地基分析方法,并利用Matlab软件编制了相应的计算程序。为了验证该方法的可行性,对楔形桩和圆柱形桩复合地基进行了模型对比试验,并利用该方法对两个模型试验进行了计算分析,试验及理论结果均表明,桩顶平面处的桩间土反力保持着类似天然地基的马鞍形分布,圆柱形桩复合地基的承载力明显低于楔形桩复合地基的承载力,同时,圆柱形桩复合地基的桩土平均应力比明显高于楔形桩复合地基的桩土平均应力比,楔形桩对缓解复合地基中桩顶应力集中,充分利用天然地基的承载能力具有良好的调节作用。     

混凝土预制桩出厂前的无损检测

本文根据弹性波理论,采用数理统计的方法,简要介绍了弹性波法在混凝土预制桩出厂前无损检测中的应用方法,同时对桩身混凝土纵波速度与混凝土强度的关系进行了实验分析,并对桩身缺陷位置及性质的判定方法进行了简要介绍。     

煤中碳酸盐矿物的测试技术和方法及测试数据的应用

我国西北及华北侏罗纪煤系地层中含有较高的碳酸盐矿物,其形成与成煤地质时代、沉积环境密切相关.根据化学组成、性质以及成因等相关因素,可将分为碱土金属碳酸盐与过渡金属碳酸盐二类.目前测试煤中碳酸盐矿物的指标有4个,即:ICC指数、碳酸盐CO2总量、NP值、矿物相分析.结合煤田地质勘探工作中测试煤中碳酸盐矿物的需要,提出了定性分级、定量测试、和矿物相分析等3个级别的测试方案,并根据每个级别测试的目的、测试的样品种类,设计了相关指标的测试方案与测定方法.煤中碳酸盐矿物的相关指标数据可广泛应用于煤质评价、煤矿废水酸碱性预测、煤加工利用、煤岩层对比与成煤地质环境等地质研究工作.     

A simplified design method for energy piles

This paper introduces a simplified method to investigate the influence of thermal loads on the shaft friction and tip resistance of energy piles. The method is based on the influence factors (λ and η) which are back-calculated drawing on a large number of field and model tests. Values for λ and η during heating and cooling are suggested. Moreover, a new equation is proposed to calculate total shaft friction. The equations concerning the relationship between η and temperature difference are recommended to investigate the impacts of the thermal load on the pile tip resistance. The slope of the linear equation of an end-bearing pile is 2.14 times that of a floating pile indicating that the pile tip resistance of an end-bearing pile is much more affected by the same thermal load.

     

考虑桩间土体抗滑作用的单排抗滑桩受力计算方法

为了充分考虑桩间距范围内滑体对抗滑桩受力的影响,从单排抗滑桩加固边坡的整体稳定角度出发,在采用传递系数法分析指定设计安全系数情况下抗滑桩的内力时,提出对一个桩间距范围内的加固坡体进行整体分析,将抗滑桩所在部位单独划分条块,该条块包括桩体受荷段及其两侧桩间距范围内的滑体。推导了与此分析模型相应的桩体受荷段底端内力计算公式,并给出了在滑坡推力线性分布条件下作用于受荷段的净滑坡推力计算表达式。分析结果显示,在不考虑与完全考虑受荷段两侧桩间距范围内滑体抗力作用时,得到是桩体内力及位移的上、下边界值。实例分析进一步表明,理论分析与数值模拟结果具有良好的一致性。所提出的方法比传统方法更有利于抗滑桩设计的经济性。     

Heat-exchanger piles for the de-icing of bridges

Of the various types of road structures, bridges are the most exposed to icing; the problem of icing is widely addressed through salting, which reduces the lifespan of the bridge. One promising solution to avoid the use of salt is the seasonal storage of solar heat energy captured directly through the asphalt layer; however, this solution can only be achieved cost effectively if a necessary geostructure is used as a heat exchanger. In this study, such an approach is studied for a bridge crossing a canal, and the geotechnical and energy-related challenges of such a solution are discussed. Bridge piers and abutments are located on piles, which are used as heat exchangers. Depending on local conditions, seasonal storage and natural thermal reload are two possible solutions for the operation of such a system. In particular, the presence of underground water flow is thought to be a significant factor in such a design and is considered here. This study aims to determine the geotechnical and energy design parameters through thermo-hydro-mechanical simulations. A three-dimensional finite-element model analysis is necessary given the distance between bridge piles. Various underground water flow scenarios are studied. The capture of energy and de-icing requirements is based on the few existing structures that use other means of energy exchange with the ground. The results indicate that the use of heat-exchanger piles for de-icing bridges can only be considered at specific sites; however, the efficiency of the solution at those sites is high. Possible foundation and structure stability problems are also considered, such as vertical displacements due to the dual use of the foundation piles.     

A numerical method for laterally loaded piles

A numerical model for a laterally loaded pile in an elastic continuum is presented. The governing differential equations for vertical piles in a homogeneous and a layered soil are obtained by using variational calculus. Two parameters, k and t, are used in this approach to represent the elastic foundation, and an iterative technique is adopted to obtain a consistent energy solution. Both free and fixed headed piles have been considered. Two kinds of boundary conditions of practical interest at the pile tip, floating tip and clamped tip, are also considered. The proposed method has been validated by comparison of the results with those obtained by other available methods. Typical solutions are presented and recommendations are given for their use in design problems.