土样剪切波速超声测试装置与方法研究

本文介绍了自行设计的土样剪切波速超声测试装置与测试方法，与扭剪三轴仪相结合，测试了多组干砂试样的剪切波速，检验了量测系统的可靠性，探讨了试件的边界条件及震相识别等问题，试验测得的干砂在不同固结压力下的剪切波速，与Hardin公式吻合良好，表明所研制的测试装置及测试方法是可行的。     

粘性土剪切波速不确定性的统计分析

土体剪切波速具有显著的不确定性。基于全国地震安全性评价工作实测的粘性土的大量剪切波速数据,采用2χ检验方法研究了粘性土不同埋深的剪切波速的概率分布。依据所获得的概率分布,采用相应的统计方法给出了粘性土不同埋深的剪切波速的平均值、最大值、最小值、标准差和变异系数,并给出了95%参考值下限和上限,所获得的结果可用于检验场地剪切波速测试结果的可靠性和粗略估计无实测资料场地土的剪切波速。     

剪切波速在判定石河子市某建设场地类别中的应用

场地类别是结构抗震设计中确定地震动参数的重要依据.相关规范允许在土类原位测试的基础上结合经验判定场地类别.但在工程地质条件复杂的场地中,这种方法存在很大的偏差.通过对比分析石河子某建筑场地根据地基土的工程地质特性、地基承载力等条件确定的场地类别与使用剪切波速判定的场地类别,说明经验方法存在的局限性,实测剪切波速依然是判定场地类别的可靠方法.     

土层剪切波速在泉州市区场地评价中的应用研究

简述了剪切波速的测试技术,并分析了剪切波速在泉州市区各类土层和各种典型地层结构中的统计规律与基本特征,研究了剪切波速在场地分类中的应用,及其与脉动卓越周期在场地评价中的关系.     

剪切波速和含水率双指标评价黄土震陷

为了研究地震荷载作用下黄土场地的震陷预测问题,以兰州黄土为研究对象来分析剪切波速和含水率与震陷系数的关系,并分别得出拟合函数关系。通过分析剪切波速和含水率在震陷过程中的内在联系,建立剪切波速和含水率双指标预测黄土震陷系数的方法,并依据该方法预测永登地震区黄土场地震陷量。研究结果表明:在一定的剪切波速区间内,震陷系数随着含水率的增加而增大;在一定的含水率区间内,震陷系数随着剪切波速的增加而减小。同时提出剪切波速可以反映黄土不因外部条件而变化的潜在震陷能力为绝对震陷能力的概念,相应的震陷系数称为绝对震陷系数,含水率影响潜在震陷能力的释放。通过震害实例计算验证剪切波速和含水率双指标预测方法的可行性。     

钻孔剪切波速测试两种方法的对比

总结了目前常用的剪切波速测试方法及原理,分析了各测试方法存在的问题及需要注意的事项,选用合理的波速数据并进行统计分析,明确了不同方法之间存在的差异,对正确、科学、严谨的进行剪切波速测试有一定的参考意义。     

应用剪切波速判别砂土液化的研究综述

首先介绍了应用剪切波速判别饱和砂土振动液化的原理；然后从临界剪应变取值、砂土的抗液化能力与剪切波速相关关系的研究方法与设备、用剪切波速进行扰动评价、建立适用于不同土类的统一判别式四方面总结了国内外学者在该领域的一些研究成果及存在问题；最后针对以上问题提出作者的一些看法。     

瑞利波测试技术用于剪切波速勘探之研究

本文根据瑞利波测量所得波形的变化特征，分析研究了地基参数对瑞利波弥散曲线的影响规律，提出了利用瑞利波测试剪切波速的方法。在研究过程中，对瑞利波测试技术进行了探讨，并引入了相关分析原理，以消除噪声、系统的非线性以及其它一些人为因素的干扰。最后结合实例，论证该技术用于实际勘探的可行性并指出其存在的问题和有待进一步完善的工作。     

互相关函数在单孔法剪切波速测量中的应用

本文系统论述了单孔法剪切波速测量信号处理中的一种到时差识别方法。对带通滤波后的触发传感器信号和探头信号进行互相关分析,可以准确地识别S波的到时。针对实际波速测试工作中两道水平信号到时差相差比较大、测点的波速计算值为负数或者计算波速数值远大于或小于现场岩样的经验实际数据等不合理因素,编制了相应的计算程序．提高了波速分析的效率和精度。     

土壤剪切波速与埋深关系的统计分析

为解决工程中剪切波速测试不能达到工作要求深度的问题,文中根据大量黑龙江地区的地震安全性评价资料,运用主要的经验公式:线性拟合Y=a+bX;多项式拟合Y=a+bX+cX2;指数拟合Y=aXb,分别统计了土壤剪切波速与埋深之间的关系,给出回归参数及适用深度。结果表明:(1)剪切波速与杂填土土层深度无论采用何种方式回归,都得不到令人满意的结果;(2)除粗砂多项式拟合方式略好于线性拟合方式外,各土类剪切波速与土层深度的关系采用线性拟合方式要优于多项式和指数拟合方式;(3)采用多项式和指数拟合方式也可以得到比较令人满意的结果;(4)除粘土(可塑、软塑)外,采用多项式拟合方式要略优于指数拟合方式。结果可为今后黑龙江地区工程场地分类,抗震设防小区化提供参考依据。     

Requirements for soil-specific correlation between shear wave velocity and liquefaction resistance of sands

The application of the simplified method for evaluating the liquefaction potential based on shear wave velocity measurements has increased substantially due to its advantages, especially for microzonation of liquefaction potential. In the simplified method, a curve is proposed to correlate the cyclic resistance ratio (CRR) with overburden stress-corrected shear wave velocity (V_s1). However, the uniqueness of this curve for all types of soils is questionable. The objective of this research is to study whether the correlation between CRR and V_s1 is unique or not. Besides, the necessity of developing the soil-specific correlations is also investigated. Based on laboratory test data, a new semi-empirical method is proposed to establish the soil-specific CRR–V_s1 correlation. To validate the proposed method, a number of undrained cyclic triaxial tests along with bender element tests were performed on two types of sands. Similar experimental data for six other types of sands reported in the literature was also compiled. Applying the proposed method, soil-specific CRR–V_s1 correlation curves were developed for these eight types of sands. It is shown that the correlation is not unique for different types of sands and the boundary curve proposed in the available simplified method can only be used as an initial estimation of liquefaction resistance. Finally, using the results of this study as well as previous ones, a chart is suggested to be used in engineering practice showing the conditions for which a detailed soil-specific CRR–V_s1 correlation study needs to be performed.     

地震横波勘探及其在浅层岩土分层中的应用

简单论述了横波的基本特点,指出在松散层勘探中,横波勘探的优势主要在于探测精度高且不受饱水度的影响.因此,可以选择地震横波勘探进行第四纪松散层层序划分及厚度探测.并以广州市城市地质调查项目为例,介绍了地震横波勘探在浅层地层勘测中的数据采集方法,分析了地质解释依据,并结合波速测井方法对地层层面进行了划分.分析结果表明了多数岩土层与反射界面有较好的对应关系,用地震横波勘探结合波速测井进行第四纪松散层层序划分及厚度探测是可行的.     

Signal processing method for shear wave velocity measurement

Soil shear wave velocity (SWV) is an important parameter in geotechnical engineering. To measure the soil SWV, three methods are generally used in China, including the single-hole method, cross-hole method and the surface-wave technique. An optimized approach based on a correlation function for single-hole SWV measurement is presented in this paper. In this approach, inherent inconsistencies of the artificial methods such as negative velocities, and too-large and too- small velocities, are eliminated from the single-hole method, and the efficiency of data processing is improved. In addition, verification using the cross-hole method of upper measuring points shows that the proposed optimized approach yields high precision in signal processing.     

鲁西平原地区土体剪切波速与埋深关系研究

鲁西平原地区属黄河冲积平原,地势平坦,工程地质情况较单一,场地类别以Ⅲ类场地为主。利用鲁西平原地区常见土类的剪切波速与埋深的数据,使用4种回归模型建立了它们之间的经验关系式,并对这些经验式的合理性进行了讨论。结果表明:鲁西平原地区常见土类的剪切波速与埋深之间有明显的相关性,基于幂函数的回归模型（v_si=ah_i^b+c）得到的经验关系式拟合效果最佳,具有较好的应用价值。     

Estimation of residual shear strength ratios of liquefied soil deposits from shear wave velocity

For sites susceptible to liquefaction induced lateral spreading during a probable earthquake, geotechnical engineers often need to know the undrained residual shear strength of the liquefied soil deposit to estimate lateral spreading displacements, and the forces acting on the piles from the liquefied soils in order to perform post liquefaction stability analyses. The most commonly used methods to estimate the undrained residual shear strength (Sur) of liquefied sand deposits are based on the correlations determined from liquefaction induced flow failures with SPT and CPT data. In this study, 44 lateral spread case histories are analyzed and a new relationship based on only lateral spread case histories is recommended, which estimates the residual shear strength ratio of the liquefiable soil layer from normalized shear wave velocity. The new proposed method is also utilized to estimate the residual lateral displacement of an example bridge problem in an area susceptible to lateral spreading in order to provide insight into how the proposed relationship can be used in geotechnical engineering practice.     

Characterization of liquefaction resistance in gravelly soil: large hammer penetration test and shear wave velocity approach

Gravelly soil is generally recognized to have no liquefaction potential. However, liquefaction cases were reported in central Taiwan in the 1999 Chi-Chi Taiwan earthquake and in the 1988 Armenia earthquake. Thus, further studies on the liquefaction potential of gravelly soil are warranted. Because large particles can impede the penetration of both standard penetration test and cone penetration test, shear wave velocity-based correlations and large hammer penetration tests (LPT) are employed to evaluate the liquefaction resistance of gravelly soils. A liquefied gravelly deposit site during the Chi-Chi earthquake was selected for this research. In situ physical properties of soil deposits were collected from exploratory trenches. Instrumented LPT and shear wave velocity (V_s) measurements were performed to evaluate the liquefaction resistance. In addition, large-scale cyclic triaxial tests on remolded gravelly soil samples (15 cm in diameter, 30 cm in height) were conducted to verify and improve LPT-based and V_s-based correlations. The results show that the LPT and shear wave velocity methods are reasonably suitable for liquefaction assessment of gravelly soils.     

Characterisation of shear wave velocity profiles of non-uniform bi-layer soil deposits: Analytical evaluation and experimental validation

A crucial aspect of physical geotechnical model tests (under both 1-g and n-g conditions) is the evaluation of the initial (low-strain) stiffness of the soil layers of the sample test deposit, especially in the case of coarse materials. While for uniform soil deposits this issue can be addressed in a straightforward manner, e.g. by determining the fundamental frequency through the transfer function of an applied white-noise excitation, the problem becomes cumbersome for multi-layered deposits. After reviewing a number of available theoretical solutions, this paper illustrates a simplified yet reliable analytical procedure for determining the shear wave velocity profile (V_s) in a single or bi-layer deposit, taking into account the inhomogeneity of the individual soil layers, under the hypothesis of vanishing shear modulus at ground surface. The fundamental natural frequency of the inhomogeneous bi-layer deposit is analysed using the Rayleigh quotient procedure. The associated shape function is evaluated by considering the equilibrium of the soil column under a pseudo-static lateral inertial excitation imposed at its base, accounting for both layering and inhomogeneity. A validation of the proposed method is provided by comparing numerical results obtained from both time- and frequency- domain analyses against experimental data on Leighton Buzzard sand, from a recently-completed research project conducted on the shaking table facility at BLADE Laboratory, University of Bristol (UK).     

剪切波速度结构研究方法综述

本文列举了目前国内外非常流行的几种剪切波速度反演的方法,介绍了各种方法的基本计算原理,并对不同方汉进行了对比,指出了各自的优缺点以及今后发展的方向.     

利用多种地震数据联合反演剪切波速度结构的可靠性检测

本文模拟使用青藏高原东南缘区域台网及国家台网的170个宽频台站基于背景噪声、天然地震面波、P波接收函数反演时的实际数据,对青藏高原东南缘假定的初始模型进行恢复,通过计算初始模型台站下方纯路径频散、提取各台站对间的瑞雷波频散曲线、计算理论接收函数以及反演剪切波速度结构来测试使用不同单项数据与联合使用多种数据反演对初始模型的恢复程度。结果表明,同时使用接收函数、基于噪声经验格林函数的群速度、相速度频散以及基于天然地震面波的相速度频散联合反演的剪切波速度结构,充分利用了几种数据的分辨率优势,清晰地分辨出中下地壳及上地幔顶部的低速层。此外,本文也分析了实际数据处理中出现的计算误差、随机噪声干扰对计算结果稳定性的影响。结果显示:对于面波频散,加入1%的误差后,联合反演的结果仍可很好地反映低速层的形态,但是当误差提升至5%后,对最终结果则产生了一定程度的影响;而在接收函数中加入4%的随机噪声时,虽然地幔低速层的上界面和下界面会略微受到随机噪声的影响,但是低速层的深度范围和速度值均得到了较好的恢复。