桩基缺陷偏心的二维效应分析

桩基低应变动测中经常会遇到桩身缺陷偏于一边的情况。对此，不同的检测人员可能会给出一定差异的检测结果，这给有关部门对缺陷桩的定性以及决策带来不便。本文针对桩基低应变动测中可能遇到的桩身缺陷偏心问题，采用二维波动有限方法进行数值模拟分析，研究桩身缺陷偏心的二维效应，分析缺陷偏心时桩顶各部位振动信号的差异，探讨对缺陷偏心桩在现场检测中应注意的问题。     

稳态机械阻抗法动测规律的应用研究

利用改进的复合平面应变轴对称的Ｂ－Ｎ法，计算得到了桩顶动力复刚度公式，并通过计算机分析得到完整桩、缩颈桩、断桩、离析桩、扩颈桩的速度导纳曲线规律及动刚度的变化规律，并结合实例对其应用作了说明．     

钻孔灌注桩的超声波透射法检测

大直径超长桩的桩身混凝土质量检测一直是困扰工程界的一个难题。本文提出和探讨了大直径超长桩桩身混凝土质量的超声波透射检测方法、技术及可靠程度。工程实践证明采用超声波透射法对大直径超长桩检测，其检测精度高，结果直观可靠，可以较详细查明桩身内部缺陷的性质、深度位置、范围大小及严重程度，为控制大直径超长桩桩身混凝土质量提供了一种有效的检测方法。     

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.     

旁孔法探测桩基完整性的数值模拟分析

为评价旁孔法在既有桩基长度和完整性检测方面的适用性,采用数值分析方法对桩顶自由桩基和带承台桩基开展动力分析,研究桩身缺陷、桩-孔间距、承台结构等因素对旁孔法测试结果的影响。分析结果表明：旁孔法用于检测桩基长度时,桩-孔测试间距不应超过1 m;对于桩身存在局部缺陷的情况,当测试孔靠近缺陷侧时,首波时深直线斜率有较明显的变化;对与承台连接的既有桩基,桩-孔测试距离越小,桩身浅部断桩、夹泥类缺陷的波形异常特征越明显,但旁孔法难以判别桩-承台连接部位是否存在缺陷。     

钻孔灌注桩的超声波检测

结合焦郑高速公路钻孔灌注桩的超声波检测,对超声波检测的原理、方法以及桩身缺陷的判定进行了介绍和分析,通过实例证明超声波检测法能准确判断出桩身缺陷的位置和范围,并能对缺陷严重程度做出评价,是检测灌注桩桩身质量的一种较好方法.     

高应变法检测预应力管桩接口探讨

由于施工人员没有按有关规范要求施工,预应力管桩锤击法沉桩过程中接口经常出现质量问题,导致接口处出现断桩情况,高应变法检测此类缺陷有明显优势。预应力管桩接口处断桩虽然不影响竖向承载力,但能否继续使用则要看它的用途。以一些工程检测实例,分析预应力管桩桩身与接口处断桩问题在高应变法检测中的表现。     

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。     

均匀黏弹性地基中现浇X形桩低应变动测响应数值模拟

建立现浇X形桩(XCC桩)桩-土体系三维有限元模型,对XCC桩低应变检测动力响应进行数值模拟,得到完整桩和缺陷桩的桩顶速度响应结果,并分析完整桩及缺陷XCC桩桩顶速度响应特性及规律。计算结果表明:XCC桩低应变瞬态动测时桩顶速度响应存在明显的三维效应,桩心(激振点)附近点的入射波峰值较大,且到达时间较早;距离桩心越远点的入射波峰到达时间越滞后,入射波峰值从桩心到尖角边界先减小后增大。桩顶距桩心距离相同的环向上各点的入射波和反射波区别不大,而各点所受的高频干扰情况并不相同。变模量桩的入射波和完整桩相同,反射波峰值较完整桩小,反射波峰对应时间较完整桩滞后。局部缺陷桩桩顶距桩心距离相同环向各点的第一个缺陷反射波有微小差别,而第二个缺陷反射波有较大差别。     

地基土—桩基础—核电站辅助厂房结构相互作用体系的地震响…

本文研究了地基土－桩－核岛辅助厂房结构相互作用体系在地震激励时的“平－扭”耦联动力响应，在分析中分别采用Ｍ．Ｎｏｖａｋ的近似理论，Ｍ．Ｎｏｖａｋ常数法，Ｍ法，常数法计算了桩基础的阻抗函数，并考虑了在同一基础上的安全壳和另一辅助厂房对所研究的辅助厂房动力响应的影响。     

基于全局弱式无单元法直流电阻率正演模拟

全局弱式无单元法是在有限单元法基础上发展起来的一种数值模拟方法,它采用局部支持域内的节点信息来构造形函数实现局部精确逼近,摆脱了单元,仅依赖于节点信息,具有预处理简单、模拟精度高、灵活性强的特点,适用于复杂地电条件下直流电阻率正演模拟.本文采用RPIM构造直流电阻率全局弱式无单元法形函数,利用RPIM形函数推导了直流电阻率全局弱式无单元法方程.然后,编制了直流电阻率全局弱式无单元法正演模拟Fortran程序,利用该程序对典型的地电模型进行了正演模拟,并将正演结果与基于线性插值的FEM正演结果及解析解进行对比,结果表明采用RPIM形函数的全局弱式无单元法用于直流电阻率正演模拟的正确性及有效性,且在同等条件下,全局弱式无单元法模拟精度高于矩形剖分的FEM,更有利于指导电法勘探的数据解译;利用该程序对复杂地电模型进行了正演模拟,结果表明全局弱式无单元法对复杂地电模型模拟效果良好,适应性强,灵活性高,可任意加密节点提高模拟精度.     

桅杆结构纤绳连接拉耳孔边裂纹扩展形状变化特性研究

本文采用两自由度的裂纹扩展模型,以桅杆结构纤绳拉耳孔边裂纹前缘最深点和表面点的裂纹扩展增长量来追踪裂纹扩展。基于最小二乘法原理对通过有限元法所获得的各种裂纹形状所对应的裂纹前缘最深点和表面点的无因次形状因子进行多项式曲线拟合,用拟合曲线上的值代替离散的无因次形状因子扩充插值数据库,采用拉格朗日插值法计算任意形状裂纹前缘最深点和表面点无因次形状因子,并计算得到确定裂纹扩展速率所需要的应力强度因子幅度。最后根据裂纹前缘最深点和表面点的裂纹扩展速率确定桅杆结构纤绳连接拉耳孔边裂纹的扩展特性。     

岩石标本破裂时的电磁辐射和光发射

在做闪长岩和大理岩破裂试验时,同时记录到电磁辐射和光发射,并利用记录到的磁场值计算出了电场强度。结果表明,这个电场强度比压电效应形成的电场强度大2、3个量级,算出的破裂面之间的电压大于空气的击穿电压。因此,岩石破裂时裂缝间的空气被击穿,这就是发光的原因之一。 另外,发光的形状与岩石标本破裂的形状相似。本文提供了一种研究岩石破裂的新方法。     

基于噪声谱比法的福建台网观测台站的场地响应研究

应用噪声谱比法, 收集了福建台网观测台站记录的地脉动噪声数据, 计算分析了85个观测台站的场地响应． 根据场地响应曲线形态将福建台网观测台站分为4类, 并简要分析了影响台站场地响应结果的因素． 计算结果表明, 福建台网观测台站台基情况普遍较好, 在台站观测频带内场地响应曲线平坦, 大部分台站均没有明显的频率放大点． 本文采用H/V谱比法与Moya方法所获得的37个台站的场地响应结果基本一致, 仅有少数台站存在较大差异． 应用场地响应分析结果, 结合计算震级时所量取的周期, 对福建台网观测台站的单台震级校正值进行了估计, 并与统计方法获得的单台震级校正值进行了比对． 结果表明, 两种方法获得的台站震级校正值存在一定的相关性, 但由于考虑的影响因素不同, 具体的台站震级校正值尚存在差别．      

Simulation and analysis of GPR signal based on stochastic media model with an ellipsoidal autocorrelation function

Target detection using ground penetrating radar (GPR) is based on the contrast between the electrical parameters of the target and the background medium, such as dielectric permittivity, conductivity and permeability. The application mainly concentrates on the detection of the medium interface and the target shape. In any theoretical study, a simulation model is built with a homogeneous medium. However, real detection encounters heterogeneous media which might produce scattering and diffraction at electrical interfaces and distort the radar pulse shape and affect the detection resolution. In this paper, we build multi-scale random media model with an ellipsoidal autocorrelation function and use FDTD method to simulate the GPR signal response. We then estimate and analyze the arrival time, layer thickness, permittivity and the physics relation in different scale random models according to the S transform method and the transmission wave method. The results demonstrate that we can use GPR to obtain geophysical information of multi-scale heterogeneous media, and provide a foundation for real media detection and complex media inversion.     

Matrix–fracture transfer shape factor for modeling flow of a compressible fluid in dual-porosity media

The matrix–fracture transfer shape factor is one of the important parameters in the modeling of fluid flow in fractured porous media using a dual-porosity concept. Warren and Root [36] introduced the dual-porosity concept and suggested a relation for the shape factor. There is no general relationship for determining the shape factor for a single-phase flow of slightly compressible fluids. Therefore, different studies reported different values for this parameter, as an input into the flow models. Several investigations have been reported on the shape factor for slightly compressible fluids. However, the case of compressible fluids has not been investigated in the past. The focus of this study is, therefore, to find the shape factor for the single-phase flow of compressible fluids (gases) in fractured porous media. In this study, a model for the determination of the shape factor for compressible fluids is presented; and, the solution of nonlinear gas diffusivity equation is used to derive the shape factor. The integral method and the method of moments are used to solve the nonlinear governing equation by considering the pressure dependency of the viscosity and isothermal compressibility of the fluid. The approximate semi-analytical model for the shape factor presented in this study is verified using single-porosity, fine-grid, numerical simulations. The dependency of the shape factor on the gas specific gravity, pressure and temperature are also investigated. The theoretical analysis presented improves our understanding of fluid flow in fractured porous media. In addition, the developed matrix–fracture transfer shape factor can be used as an input for modeling flow of compressible fluids in dual-porosity systems, such as naturally fractured gas reservoirs, coalbed methane reservoirs and fractured tight gas reservoirs.     

A NUMERICAL METHOD OF CALCULATING THE KERNEL FUNCTION FROM SCHLUMBERGER APPARENT RESISTIVITY DATA*

A method to calculate the resistivity transform of Schlumberger VES curves has been developed. It consists in approximating the field apparent resistivity data by utilizing a linear combination of simple functions, which must satisfy the following requirements: (i) they must be suitable for fitting the resistivity data; (ii) once the fitting function has been obtained they allow the kernel to be determined in an analytic way. The fitting operation is carried out by the least mean squares method, which also accomplishes a useful smoothing of the field curve (and therefore a partial noise filtering). It gives the possibility of assigning different weights to the apparent resistivity values to be approximated according to their different reliability. For several examples (theoretical resistivity curves in order to estimate the precision of the method and with field data to verify the practicality) yield good results with short execution time independent of shape the apparent resistivity curve.     

Effect of fracture pressure depletion regimes on the dual-porosity shape factor for flow of compressible fluids in fractured porous media

A precise value of the matrix-fracture transfer shape factor is essential for modeling fluid flow in fractured porous media by a dual-porosity approach. The slightly compressible fluid shape factor has been widely investigated in the literature. In a recent study, we have developed a transfer function for flow of a compressible fluid using a constant fracture pressure boundary condition [Ranjbar E, Hassanzadeh H, Matrix-fracture transfer shape factor for modeling flow of a compressible fluid in dual-porosity media. Adv Water Res 2011;34(5):627-39. doi:10.1016/j.advwatres.2011.02.012]. However, for a compressible fluid, the consequence of a pressure depletion boundary condition on the shape factor has not been investigated in the previous studies. The main purpose of this paper is, therefore, to investigate the effect of the fracture pressure depletion regime on the shape factor for single-phase flow of a compressible fluid. In the current study, a model for evaluation of the shape factor is derived using solutions of a nonlinear diffusivity equation subject to different pressure depletion regimes. A combination of the heat integral method, the method of moments and Duhamel’s theorem is used to solve this nonlinear equation. The developed solution is validated by fine-grid numerical simulations. The presented model can recover the shape factor of slightly compressible fluids reported in the literature. This study demonstrates that in the case of a single-phase flow of compressible fluid, the shape factor is a function of the imposed boundary condition in the fracture and its variability with time. It is shown that such dependence can be described by an exponentially declining fracture pressure with different decline exponents. These findings improve our understanding of fluid flow in fractured porous media.     

基于图像分割的成像测井资料目标拾取与计算

为了从FMI资料中提取定量信息,一个很重要的步骤就是要对FMI图像数据进行分割.即从实际FMI资料中分离出反映孔洞、裂缝的子图像,然后用相应的方法对分割后的子图像进行分析处理,提取相应参数.本文通过研究大量图像分割算法,认为奇异点多阈值分割算法、基于过度区的分割算法、Hopfield网络方法、基于图像间模糊散度的阈值化算法是FMI图像分割的有效方法,实现了从FMI图像中将地层中有用目标,从背景中分离出来.同时,为了得到孔洞及裂缝的形状参数,本文还研究了轮廓跟踪标识边缘的方法以及根据标识的边缘进行填充的算法.在此基础上,也研究了根据目标边缘坐标计算目标的长度、宽度、圆度、裂缝密度、孔洞密度等参数的方法.上述所有方法在SUN工作站GeoFrame平台上开发成功,通过对LX45等八口井的处理结果与岩心分析数据对比表明,效果较好.