A new method of testing pile using dynamic P-S-curve made by amplitude of wave train

A new method of detecting the vertical bearing capacity for single-pile with high strain is discussed in this paper. A heavy hammer or a small type of rocket is used to strike the pile top and the detectors are used to record vibration graphs. An expression of higher degree of strain (deformation force) is introduced. It is testified theoretically that the displacement, velocity and acceleration cannot be obtained by simple integral acceleration and differential velocity when long displacement and high strain exist, namely when the pile phase generates a whole slip relative to the soil body. That is to say that there are non-linear relations between them. It is educed accordingly that the force P and displacement S are calculated from the amplitude of wave train and (dynamic) P-S curve is drew so as to determine the yield points. Further, a method of determining the vertical bearing capacity for single-pile is discussed. A static load test is utilized to check the result of dynamic test and determine the correlative constants of dynamic-static P(Q)-S curve. Foundation item: Key projects of the tenth Five-year Plan of Yunnan Province (documented Yunnan district [2002]54-02-02) and Geophysical Society of Yunnan Province.     

波列振幅P em>-Sem>曲线测桩法

叙述一种新的大应变检测单桩竖向承载力的方法. 用重锤或小型火箭筒冲击桩顶，用检波器记录振波图. 引入应变（变形力）的高次项，从理论上证明当为大位移大应变， 即桩相对于土体产生整体滑动时，位移、速度和加速度则不能经过简单积分加速度和微分速度得到，即它们为非线性关系. 由此导出:通过波列振幅计算力（P）和位移（S）,并作（动态）P-S曲线、确定屈服点，进而阐述确定单桩竖向承载力的方法，并利用静载荷试验检验动测结果和确定动静P（Q）S曲线的相关常数.      

A new method for testing pile by sin- gle-impact energy and P-S curve

Introduction Through many year's practices by vast numbers of scientific and technological workers andefforts from all aspects, the dynamic testing method of high-low strain has formally entered intothe technical code of foundation pile test of construction at last (The Industry Standards of thePeople's Republic of China, 2003). The striking mode of the dynamic testing method of high strainis stipulated as hammer in the code, the striking of rocket can also be used. The latter is widely…     

波列振幅衰减测桩法的研究与应用(Ⅱ)——桩身成型质量的检测

通过对波动、振动和尾波的特征分析，提出以足够大的力冲击桩顶，在桩顶附近记录综合波列图，利用其振幅衰减、周期变化和反射波震相等判断桩身成型质量：波列周期均匀且较小，同时波列振幅衰减较快，而又未见明显反射波震相者桩身成型良好；而有缺陷如断裂、缩径等时波列振幅衰减变慢，反射波震相明显，且有大周期出现.它对桩的浅部（特别是桩顶下5米以内的）缺陷检测特别有效.另外利用动态PS曲线也可判断桩身成型质量：曲线较平滑者，桩身成型良好；曲线出现弯折者桩身存在缺陷，缺陷程度可参照承载力受影响大小确定.     

A new method for testing pile by single-impact energy and P-S curve

By studying the pile-formula and stress-wave methods (e.g., CASE method), the authors propose a new method for testing piles using the single-impact energy and P-S curves. The vibration and wave figures are recorded, and the dynamic and static displacements are measured by different transducers near the top of piles when the pile is impacted by a heavy hammer or micro-rocket. By observing the transformation coefficient of driving energy (total energy), the consumed energy of wave motion and vibration and so on, the vertical bearing capacity for single pile is measured and calculated. Then, using the vibration wave diagram, the dynamic relation curves between the force (P) and the displacement (S) is calculated and the yield points are determined. Using the static-loading test, the dynamic results are checked and the relative constants of dynamic-static P-S curves are determined. Then the subsidence quantity corresponding to the bearing capacity is determined. Moreover, the shaped quality of the pile body can be judged from the formation of P-S curves. Foundation item: Key Projects of Tenth Five-year Plan of Yunnan Province (54-02-02).     

基桩动力检测的问题及改进方向

有关桩质量及承载能力的动力检测方法很多,各有特色,很多文献有详细介绍,一些方法还列入有关规程或规范中。实际上,桩基是隐蔽工程,桩质量受施工技术的影响可能出现多样性的缺陷;桩承载能力的动力分析又必须依据规范规定的静载试验结果来校核、修正。因此,动力试验方法的准确性受多种因素的影响。本文依据实践工作中的体会和认识,明确指出现有的主要动力检测方法在判别桩可能存在的缺陷性质、位置、程度方面各自存在的局限性,以及在判断桩承载力的试测方式和分析方法上存在的问题,并就噪声干扰及桩动静试验可比性等问题提出一些改进的思路及设想。     

A new method of testing pile using dynamic <Emphasis Type="Italic">P-S</Emphasis>-curve made by amplitude of wave train

A new method of detecting the vertical bearing capacity for single-pile with high strain is discussed in this paper. A heavy hammer or a small type of rocket is used to strike the pile top and the detectors are used to record vibration graphs. An expression of higher degree of strain (deformation force) is introduced. It is testified theoretically that the displacement, velocity and acceleration cannot be obtained by simple integral acceleration and differential velocity when long displacement and high strain exist, namely when the pile phase generates a whole slip relative to the soil body. That is to say that there are non-linear relations between them. It is educed accordingly that the force P and displacement S are calculated from the amplitude of wave train and (dynamic) P-S curve is drew so as to determine the yield points. Further, a method of determining the vertical bearing capacity for single-pile is discussed. A static load test is utilized to check the result of dynamic test and determine the correlative constants of dynamic-static P(Q)-S curve.     

自平衡法桩基承载力测试中一些问题的探讨

自平衡法作为一种新型的桩基承载力测试方法,具有测试荷载大、测试简便、结果可靠等多方面的突出优点。本文通过东北地区两个具体工程实例的介绍,阐述了其在大型桩基承载力测试中的应用,并对测试过程中存在的问题进行了分析。结合工程实际,对自平衡法桩身受力变形特征和极限承载力差异进行了对比分析,提出确定荷载箱平衡位置的合理方法。指出进一步加强对其作用机制、平衡点位置、试验结果转换等方面的研究是自平衡法不断完善的关键。     

用机械阻抗法确定作业井架地锚桩的极限承载力

由于油田井下作业井架为一两腿落地的空间钢架结构,需要用绷绳作支撑,所以用于固定油田井下作业井架绷绳的地锚桩,其抗拔极限承载力的研究与确定对保证井下作业安全至关重要。本文用机械阻抗法对井下作业系统中地锚桩的极限抗拔载荷进行了测试与研究。采用瞬态激励法,用变时基技术分别测试了4种规格尺寸的油管桩和一种规格尺寸的水泥桩在瞬态激励下的速度信号,进行变时基传函分析得出动刚度,确定了极限承载力。结果分析表明,在大庆油田粘性土使用条件下,水泥桩的极限抗拔拉力很大,完全可以满足井下作业需要;不同尺寸油管桩的极限抗拔拉力差异较大,井下作业时应使用2．5m以上长度的油管桩。     

确定桩承载力的脉冲位移法

本文拟在微幅振动试验中进行桩承载力的理论分析并在实用条件的基础上，介绍一种简易试验分析方法即脉冲位移法，为工程建设服务。     

波列振幅衰减测桩法的研究与应用(Ⅰ)--单桩竖向承载力的测定

通过研究打桩公式法和应力波动法(如CASE法),作者提出：用重锤或小型火箭筒一次冲击桩顶,用桩顶附近的检波器记录振波图和检测静、动位移,通过实测冲击能(总能量)转换系数、波动和振动各自消耗的能量等各物理量,测定计算单桩竖向承载力．利用振波图计算力(P)和位移(S)动态关系曲线、确定屈服点。并利用静载荷试验检验动测结果和确定动静PS曲线的相关常数,进而确定与承载力相应的沉降量。     

爆炸荷载下桩基竖向动承载力研究

针对地面抗爆工程建设中桩基设计问题,采用动三轴试验、动力有限元方法等手段,开展了爆炸作用下地基土的动力特性及桩基抗爆承载力研究,结果表明桩基竖向极限抗爆承载力为其竖向极限静承载力2倍以上,高于按照现行桩基规范得到的1.25 ～1.5倍范围值,表明将常规抗震设计的办法直接用于抗爆炸冲击荷载的桩基设计时偏保守.     

低应变反射波法在基桩检测中的应用实例及一些问题的探讨

根据应力波理论，介绍了用低应变反射波法在桩身完整性检测中的几个应用实例，并对检测中的一些问题作了探讨。     

浅析瑞雷波法检测复合地基承载力

复合地基检测手段中以传统的静载荷试验为主,瑞雷波法是一种利用瑞雷波的运动学特征和动力学特征来进行工程质量检测及工程地质勘察的物探方法,可以大范围检测地基加固效果,问接提供地基的承载力。     

模型桩低应变反射波法曲线研究

根据基桩低应变检测的基本原理,对于大型模拟缺陷桩低应变反射波法曲线进行了分析,以便在解释反射波法曲线时作为借鉴,提高基桩质量检测的可靠度。     

结构抗震试验方法的发展

地震荷载极大的破坏性,使得结构抗震性能的研究成为一个被广泛关注的热点问题.为了提高结构抗震研究的试验能力和试验水平,近年来在传统结构抗震试验方法的基础上,出现了一些新的试验方式和方法.本文总结介绍了目前结构抗震试验方法的一些发展趋势,包括：（1）地震模拟振动台的大型化和多台化,以进行大比例模型甚至足尺模型试验或考虑大跨度结构地震动的非均匀性;（2）进行子结构试验的实时化,以实现数值子结构模型和试验子结构模型的实时结合;（3）进行试验设备的网络化,以提高试验设备的利用率,实现资源共享等,供有关研究者参考.     

Inversion of focal mechanism and events identification using an improved relative amplitude method

The relative amplitude method(RAM) is more suitable for source inversion of low magnitude earthquakes because it avoids the modeling of short-period waveforms.We introduced an improved relative amplitude method(IRAM) which is more robust in practical cases.The IRAM uses a certain function to quantify the fitness between the observed and the predicted relative amplitudes among direct P wave,surface reflected pP and sP waves for a given focal mechanism.Using the IRAM,we got the fault-plane solutions of two ea...     

Discussion of: A study on the application of the parallel seismic method in pile testing

This discussion is based on the paper by Lu et al. (2013) [1]. In this paper, the authors have presented a theoretical study on the PS testing based on the ray path theory and the elastodynamic finite integration technique. This discussion offers some comments on the proposed method for determining the pile length, the ray path of the first P wave arrival for PS testing and analysis results of that paper under discussion.     

Influences of type of wave and angle of incidence on seismic bending moments in pile foundations

When analysing the seismic response of pile groups, a vertically‐incident wavefield is usually employed even though it does not necessarily correspond to the worst case scenario. This work aims to study the influences of both the type of seismic body wave and its angle of incidence on the dynamic response of pile foundations. To this end, the formulation of SV, SH and P obliquely‐incident waves is presented and implemented in a frequency‐domain boundary element‐finite element code for the dynamic analysis of pile foundations and piled structures. Results are presented in terms of bending moments at cap level of single piles and 3 × 3 pile groups, both in frequency and in time domains. It is found that, in general, the vertical incidence is not the most unfavourable situation. In particular, obliquely‐incident SV waves with angles of incidence smaller than the critical one, a situation in which the mechanism of propagation of the waves in the soil changes and surface waves appear, yield bending moments much larger than those obtained for vertically‐incident wavefields. It is also shown that the influence of pile‐to‐pile interaction on the kinematic bending moments becomes significant for non‐vertical incidence, especially for P and SV waves. Copyright © 2013 John Wiley & Sons, Ltd.     

体外预应力梁动力特性分析的一种新方法

提出了两个假设:在第1自振频率计算中,体外筋预拉力增量产生的弯矩图等效为梁第1振型的比例图,忽略了体外筋对其他自振频率的效应。这两个假设改进了文献[5]中的体外筋预拉力增量与梁跨中位移成正比的假设。建立了体外预应力梁的动力平衡方程,解得梁的振型和自振频率。与文献[5]中的分析方法相比,由于假设更为合理,计算结果也更准确,与数值解吻合良好。计算结果表明:文献[5]方法低估了体外筋对第1自振频率的效应;随着体外筋面积和偏心距的增加,梁的自振频率也随之增加。