导波在锚固金属杆中传播机理的研究

运用波动的经典理论,提出了导波在金属杆嵌入层“变截面”传播时波速改变的“等效弹性模量”的概念。对导波在锚固金属杆中的传播,尤其是在金属杆与锚固交界面处的传播机理进行理论分析,并提出了在锚固交界面处导波以耦合“低频脉冲”传播的思想。这一概念,可以解释运用导波进行无损检测得到的时域分析图中信号发生的“时滞”与波形拉平现象。     

动剪切模量比与剪切波速对地震动影响及等量关系研究

采用数值模拟方法,研究动剪切模量比和剪切波速对地震动的影响问题,并以对地表加速度反应谱影响为标准研究动剪切模量比变化与剪切波速变化间的对等关系,同时建立了等价关系式,分析中考虑了场地类别、场地遭遇地震强度和地震输入波型的影响。结果表明:①动剪切模量比误差和剪切波速误差对地震动都有着重要影响,在土体强非线性和软弱场地中影响更为强烈,实测的动剪切模量比和剪切波速比真实值低时较比真实值高时对地表反应谱影响更大,三类场地0.1g地震输入时动剪切模量比6%误差或剪切波速25%误差的影响已经不可忽视;②对不同的场地类别、场地地震烈度和地震输入波情况,动剪切模量比单独变化与剪切波速单独变化对反应谱的影响都具有对等关系;③动剪切模量比误差对地震动的影响程度要大于剪切波速误差,二者对地表反应谱的敏感性相差3～5倍,绝对误差相同时动剪切模量比降低情况下与剪切波速的敏感程度相差更大。     

地震动空间效应与土-基础相互作用效应对隔震桥梁临界碰撞间隙的影响

基于随机振动理论和虚拟激励法,研究了地震动空间效应与土-基础相互作用效应对隔震梁桥临界碰撞间隙的影响。建立了临界碰撞间隙计算方法,分别研究了仅考虑地震动空间效应、仅考虑土-基础相互作用和同时考虑地震动空间效应与土-基础相互作用三种情况下各参数对临界碰撞间隙的影响。研究表明:当地基土剪切波速较小且部分相干效应不显著时,临界碰撞间隙随地基土剪切波速减小而减小;当地基土剪切波速较大时,不论是否考虑地震动空间效应,地基土剪切波速对临界碰撞间隙的影响很小;行波效应与部分相干效应对临界碰撞间隙的影响不能忽视,且部分相干效应的影响更突出,部分相干效应越显著,临界碰撞间隙越大;临界碰撞间隙随隔震支座阻尼比的增大而减小,且当部分相干效应显著时,随隔震支座周期的增大而增大。     

饱和砂土的原位动强度确定方法探讨

基于原状样、重塑样的室内剪切波速和动三轴试验,本文首先探讨了剪切波速和动强度的相关性,然后对实际地震半经验动强度确定方法进行考察.     

二郎山公路隧道岩爆发生规律与岩爆预测研究

岩爆是地下工程中经常遇到的一种地质灾害,根据二郎山公路隧道在施工中记录的２００ 多次岩爆资料,总结了该隧道岩爆发生的基本规律;并采用“地质超前预报法”、“σθ／ Ｒｂ 判据法”和“岩爆临界深度预测法”三种方法,对其岩爆预测问题作了有益的探讨。     

不同波形下饱和黏土耦合循环剪切特性的对比研究

海洋波浪荷载在海床内土体中引起的动应力的特点是动应力幅恒定,动主应力方向连续旋转。利用土工静力–动力液压三轴–扭剪多功能扭剪仪模拟海洋波浪的加载形式,针对饱和黏土进行了竖向和扭转耦合循环剪切试验,着重对比研究了在正弦波和三角波两种不同波形条件下饱和黏土的动强度、变形特性、广义临界循环应力比与应力洛德参数。研究表明:在相同破坏振次条件下,正弦波耦合试验比三角波的动强度小,且动剪应力越小,两者动强度的相对降低也越少;在相同动剪应力幅值下正弦波耦合循环剪切的变形大于三角波的变形;耦合循环剪切试验中的广义临界循环应力比受波形的影响,正弦波的广义临界循环应力比小于三角波的;应力洛德参数的变化曲线在不同波形下也有所不同。     

潮间带原位剪切波速特性探讨及应用分析

探讨适用于近海及潮间带场区的剪切波速原位测试方法,针对黄海小洋口潮间带,进行剪切波速的原位测试,分析剪切波速的变化规律及其与土体参数的统计关系,并建立复合关系进行剪切波速预测分析,同时基于剪切波速测试成果进行应用分析。研究结果如下：通过经适性对比,近海及潮间带剪切波速测试采用单孔悬挂式方法较为适宜;剪切波速与测点深度呈相关性较好幂函数关系,按土层的统计关系分析,幂函数及其误差包络线基本反映了规律性;与土体物理力学参数的统计关系呈相关性较好幂函数或线性关系;基于测试资料,建立剪切波速 、孔隙比e、密度 及有效自重应力 的复合关系,通过计算对比分析,按此方法可以取得良好的剪切波速预测结果,亦可进行相关指标的预测分析;通过原位测试资料,进行场地土类划分对比、动参数规律性分析及地震液化判定分析,可为工程勘测、设计人员提供参考。     

由实测幅频曲线推求地基动力参数的新方法

<正> 为了经济合理地设计动力基础,需要确定地基动力参数。动力基础设计规范(GBJ40-79)建议采用点峰法来整理实测资料,求取地基动力参数,其缺点是只能求得反映较大频围平均效果的“区间”型动参,无法确定任一频率处的“点”型动参,而由这种“点”型动参连结而成的动参-频率关系对于寻找动参变化规律,验证半空间理论的正确性和更为精密地设计动力基础是有益的。为此,本文提出了一种新的推算地基动参的方法--“三点法”,用以推求任一频率处的地基动参,补点峰法之不足。     

对“应力波反射拍信号的检测及其工程应用”一文的讨论

对“应力波反射拍信号的检测及其工程应用”一文的讨论陈凡（中国建筑科学研究院地基所，北京，１０００１３）近读《岩土工程学报》１９９５年第３期上一文“应力波反射拍信号的检测及其工程应用”（以下简称“拍文”），颇感新颖。作者首次将“拍”的概念引入桩的动测分...     

黄土和泥岩的动力学特性及微观损伤效应

 为了系统研究天水地区黄土和泥岩的动力学特性和微细观损伤机制,采用循环荷载试验、反复剪试验和SEM电镜扫描技术,获取岩土体的动力学行为特征和微观参量。研究结果表明：黄土和泥岩的动弹性模量随围压的增加逐渐增大,呈非线性关系,而动弹性模量与阻尼比呈反比关系;动剪应力比大于某阈值时,岩土体在相应周期动应力下发生破坏;地震强度以及岩土体自身材料对其动力学强度影响较大;反复剪切次数增加,岩土体的抗剪强度降低,最终达到残余强度,但随围压的增大,岩土体咬合程度增强,抗剪强度增加;静力剪切使土颗粒变细,属颗粒剪切磨碎模式,土颗粒排列更平整,定向性好,颗粒间孔隙变密实;循环动荷载作用下,随着剪切幅值的增加,颗粒剪切磨碎,排列更平整,孔隙明显减少,剪切面表现为“板结”。泥岩微观孔隙的定量化分析与定性研究一致性较好。研究结果对黄土高原地区工程灾害的预测和控制具重要的理论意义和实用价值。     

A simple method for evaluating liquefaction potential from shear wave velocity

The simplified procedure using shear wave velocity measurements is increasingly used to evaluate the seismic liquefaction potential of soils. This procedure is based on finding the boundary separating the liquefaction and non-liquefaction cases through the analysis of liquefaction case histories, following the general format of the Seed-Idriss simplified procedure based on standard penetration test (SPT) data. It is noted that many assumptions have been made in the simplified procedure. This paper develops a simple method for evaluating the liquefaction potential of soils from shear wave velocity by using the optimum seeking method to directly analyze the liquefaction history data and quantify the influence of major factors affecting the liquefactions potential of soils. The factors considered are the earthquake magnitude, the vertical effective overburden stress, the shear wave velocity, the peak acceleration at the ground surface of the site, and the fines content of the soil. The most important factor has been identified as the shear wave velocity. The developed method uses the measured data directly and in a very simple way. Neither stress-correction of shear wave velocity nor calculation of cyclic shear stress as in the simplified procedure is required. Comparisons indicate that the developed simple method has a higher success rate for evaluating liquefaction potential of soils than the simplified procedure. A case study is presented to illustrate the application of the developed simple method and further confirms its accuracy.     

A simple method for evaluating liquefaction potential from shear wave velocity

The simplified procedure using shear wave velocity measurements is increasingly used to evaluate the seismic liquefaction potential of soils. This procedure is based on finding the boundary separating the liquefaction and non-liquefaction cases through the analysis of liquefaction case histories, following the general format of the Seed-Idriss simplified procedure based on standard penetration test (SPT) data. It is noted that many assumptions have been made in the simplified procedure. This paper develops a simple method for evaluating the liquefaction potential of soils from shear wave velocity by using the optimum seeking method to directly analyze the liquefaction history data and quantify the influence of major factors affecting the liquefactions potential of soils. The factors considered are the earthquake magnitude, the vertical effective overburden stress, the shear wave velocity, the peak acceleration at the ground surface of the site, and the fines content of the soil. The most important factor has been identified as the shear wave velocity. The developed method uses the measured data directly and in a very simple way. Neither stress-correction of shear wave velocity nor calculation of cyclic shear stress as in the simplified procedure is required. Comparisons indicate that the developed simple method has a higher success rate for evaluating liquefaction potential of soils than the simplified procedure. A case study is presented to illustrate the application of the developed simple method and further confirms its accuracy.     

相同剪切波速的原状与重塑饱和松散粉土的抗液化强度

采用剪切波速与振动三轴联合试验装置,研究了具有松散结构的原状和重塑饱和粉土抗液化强度之间的相关性。结果表明,具有松散结构的原状与重塑饱和土样的振动应变随振动次数的变化趋势是一致的。如果把重塑饱和土样的初始剪切波速恢复到原状饱和土样的初始剪切波速,重塑土样的抗液化强度也被恢复到原状土样的抗液化强度。此时,原状与重塑土样的抗液化强度与抗液化强度曲线之间的相关系数大于0.89,而且这种良好的相关性与确定破坏振次的液化判别标准无关。这里的研究结果支持饱和松散试验土样的初始剪切波速可以作为控制其抗液化强度的一个关键参数。     

徐州市棠张镇铁路路基液化性能研究

依据已有的孔压增长模型和动三轴试验参数，采用有限单元法，对徐州市棠张镇铁路路基可液化场地进行了地震反应分析。按孔压比和最大往返剪切作用面上的动翦应力比较法划分了饱和粉土层的液化区域，并结合标准贯入试验判别结果、剪切波速判别结果以及Seed-Idriss简化法判别结果，对该场地粉土层的液化性能做出了综合评价。     

Effects of induced anisotropy on multiple liquefaction properties of sand with initial static shear

The multiple liquefaction phenomenon has been attracting the attention of more and more researchers and engineers since the 2010–2011 Christchurch Earthquakes and the 2011 Great East Japan Earthquake. However, little has been known about the multiple liquefaction properties of sloped grounds. In this study, therefore, multiple liquefaction tests that consider the initial static shear stress, which have never been conducted before, were carried out with a special designed apparatus, the stacked-ring shear apparatus. A series of multiple liquefaction tests revealed that induced anisotropy, which is weak against the loading opposite to the direction of the initial static shear stress, was produced by the liquefaction of a sloped ground. As a result, a significant decrease in the liquefaction resistance during the next cyclic of shearing occurred. The indicators which influenced the magnitude of anisotropy were also discussed from the perspective of the reconsolidation procedures, the magnitude of initial static shear stress, and the type of ending of the previous liquefaction stage. In addition, it turned out that in the multiple liquefaction test with a larger initial static shear stress, the re-liquefaction resistance was higher because the shear stress opposite to the direction of the initial static shear stress, causing large negative dilatancy due to anisotropy, was smaller in that test.     

初始剪应力对饱和粉土液化特性影响试验研究

为探寻饱和粉土的液化特性,利用GDS空心圆柱仪进行了一系列循环扭剪试验。在初始剪应力τs和循环剪应力τcy共同作用下,试样的最小剪应力τmin=τs-τcy存在3种类型:τmin0,τmin=0和τmin0。试验结果表明:当τmin≤0时,试样的孔压可以达到有效围压,其破坏模式为循环液化;当τmin0时,试样的孔压始终达不到有效围压,其破坏模式为过大的累计应变。饱和粉土的循环强度随着初始剪应力τs与初始有效平均主应力0p′之比值SSR(初始剪应力比)的增加呈现出先减小后增大变化趋势,且SSR=0.1~0.15时的循环强度最低。当SSR≤0.1时,孔压比的发展模式随着循环剪应力比的增加由"快—平稳—急剧"的增长模式向"快—平稳"的增长模式转变;当SSR0.1时,孔压比的发展呈现"快—平稳"的增长模式。     

双向耦合剪切条件下饱和松砂的液化特性试验研究

为了模拟海床及海洋建筑物遭受波浪荷载时所引起的循环应力,进行了一系列均等固结条件下的应力控制式轴向–扭转双向耦合循环剪切试验。加载路径在σd/2-τ应力空间内为椭圆。试验在保证椭圆面积不变的情况下,分别变化竖向和扭转向的荷载分量幅值,以此来探讨双向耦合剪切试验中各个分量的变化对饱和松砂的循环强度特性的影响。试验结果表明砂土在双向耦合荷载作用下,其液化强度与加载椭圆路径的面积和两个荷载分量比值密切相关。当轴向应力与剪应力幅值的比值保持不变时,砂土液化强度随着椭圆面积的增大而降低。而在椭圆面积保持不变时,当竖向与扭转向荷载分量的比值小于某一临界值0.6～0.75时,砂土液化强度随着比值的增加而增大,当竖向与扭转向荷载分量的比值大于某一临界值0.6～0.75时,砂土的液化强度随着比值的增加而减小,在临界值0.6～0.75之间表现出最高的强度。另外,在一个周期内孔隙水压力的循环变化与轴向应力相位一致,与循环剪应力相位相差90。     

剪切波速-相对密度联合试验与经验公式验证

汶川Ms8.0地震发生的数百公里大规模砾性土液化震害,引起了国内外学者对剪切波速液化判别技术适用性的高度重视。为合理评价波速测试手段应用于高含砾量、宽级配粗粒土液化判别的可靠性,发挥该技术在室内外土动力参数关联方面的独有优势,以相对密度与抗液化强度相关性为基础,通过自主研制大型波速量测系统,开展饱和砂土与砾性土剪切波速-相对密度联合室内试验,分析砾性土相对密度与波速指标内在关联性,对已有经验公式进行验证。研究结果表明:砾性土波速与相对密度呈良好线性关系,颗粒组排结构的不同是导致砾性土与砂土整体波速差异及数据离散度差别的主要原因;砾性土剪切波速对孔隙比变化灵敏度高于角砾砂,所提修正经验公式更适于描述砾性土波速随相对密度变化关系。     

动单剪分析饱和粉土的液化性

利用Shear Trac-II-DSS动单剪测试系统,研究了邯郸地区饱和粉土的液化性。结合Seed简化理论中等效的原则,将地震剪应力时程等效成周期剪应力和周期次数,得到了地震剪应力与抗液化剪应力关系曲线;初步确定了该地区粉土液化深度为2m左右,初始液化区域为2～6m;当埋深较浅时,抗液化强度比等效地震剪应力要大;随着埋深增加抗液化强度和等效地震剪应力均增大,且抗液化强度增加的幅度比等效地震剪应力增幅要小;当达到一定深度时,抗液化强度等于等效地震剪应力,出现初始液化现象;随着埋深进一步增加,抗液化强度增加的幅度比等效地震剪应力增幅要大,最终导致粉土不液化。该结论可为今后的工程设计提供参考。