饱和土中单桩水平瞬态响应研究

基于Biot动力固结方程,应用Novak薄层方法研究了饱和土中单桩在水平冲击荷载作用下的动力响应问题。首先引入势函数对方程解耦,再通过算子分解和分离变量法,结合初始边界条件,并联立桩基振动微分方程,推导了Laplace变换域内桩身位移函数及内力表达式。采用Laplace逆变换的优化模型求得了时域内瞬态响应的封闭解。将该解退化到单相介质条件下的桩顶位移-时间曲线与已有的边界元方法的结果基本吻合,验证了解答的正确性。参数分析结果表明：桩-土模量比、长径比、渗透系数对桩身位移均影响显著,而同条件下长径比超过一特定值后则影响较小,且桩土模量比是影响桩身弯矩大小及其分布的重要参数。     

饱和土表面在水平集中荷载作用下的瞬态反应

分析了水平集中荷载作用在半空间饱和土表面时的瞬态问题。利用Laplace-Hankel变换对非轴对称Biot固结方程进行解耦，利用Laplace-Hankel数值逆变换得到半空间饱和土在时域内的数值解。退化到线弹性中的解与文献中的结果进行比较，验证了文中结果的正确性和数值逆变换的可靠性.可以用于研究地震工程中地震波的传播以及饱和土与结构之间相互作用等问题。     

电离层影响下均匀半空间水平谐变电偶极子的电磁响应计算

空气介质和电离层是电导率不同的分层媒质,当研究由空气层中电流或磁矩激发的电磁场时,地面接收到的电磁波不仅受到空气介质、地下介质的影响,而且还受到电离层的影响。首先,推导出了电磁场一般边值问题,然后,将电离层、空气及地壳视为均匀、线性、各向同性的三层媒质,考虑地壳、空气、电离层的相互耦合,利用分离变量法推导求得了位于地壳表面水平谐变电偶极子的电磁响应表达式,通过这些表达式能够方便地求出电离层影响下均匀半空间空气层中的电磁场场值,同时,为后续的数值计算奠定了理论基础。     

高阻空洞的瞬变电磁响应特征及其探测效果

通过球体电磁响应的计算,对低阻围岩中高阻球体模型电磁响应测量结果进行了分析,获得了高阻球体的异常特征。对干旱地区深埋土洞的工程探测结果表明:高阻土洞的瞬变电磁响应特征与模拟实验结果类似,对高阻目标体具有较好的探测效果;高阻体引起的瞬变电磁场异常范围大于目标体实际规模。     

低频谐变电偶极源激发的地下电磁场的闭式解

研究偶极子源产生的电磁场在地下或水下无线电通信和地球物理勘探领域有着重要的应用价值。偶极子和介质的作用往往导致Sommerfeld型积分的解。为了深入揭示电磁波在地下的分布与传播规律,本文针对有耗媒质中为获得大探测深度和长距离通信使用的低频发射天线,在准静态近似条件下导出了水平电偶极子产生的下电磁场Sommerfeld型积分解的闭式表达式。这些公式适用于任意场区和除奇异点以外的任何场点,与数值积分相比,可显著提高计算速度。利用闭合表达式,本文还提出了一种新的场区划分方法。     

大定源瞬变电磁均匀层状介质正演计算

大定源回线瞬变电磁法以其高效的工作方式,一直备受野外工作者青睐。这里从基本理论出发,给出了大定源回线发射源在均匀层状介质的电磁响应计算公式,利用Quadrature With Extrapolation(QWE)算法计算了线框内、外的垂向磁场响应,并将其与传统的Fast Hankel Transform(FHT)算法进行了对比分析,两者对于虚部的计算都比较准确。当发射线框位于地表以上一定高度时,两者的计算结果吻合的较好。在发射线圈位于地表的时候,QWE算法的计算结果比较稳定,适用性优于FHT。     

移动环形荷载作用下饱和土中圆形衬砌隧洞动力响应研究

基于Biot理论,研究了饱和土中带有衬砌的圆形隧洞在移动环形荷载作用下的动力响应。假定衬砌为弹性体,土体为饱和多孔介质,引入两类势函数来表示土体、孔隙水和衬砌的位移,使隧洞的控制方程解耦。结合边界条件及连续条件,通过傅立叶变换得到频率-波数域中衬砌和土体的应力、位移和孔隙水压力解答,最后用傅立叶积分逆变换得到时-空域中的数值解。计算并比较了3种隧洞模型（弹性土体隧洞、饱和土体隧洞和饱和土衬砌隧洞）的动力响应分析。数值分析结果说明：（1）移动荷载速度对3种隧洞动力响应均具有较大影响;（2）弹性土体隧洞和饱和土体隧洞的动力响应具有明显区别,所以在富水地区的隧洞动力响应中土体应该视为饱和土体;（3）衬砌对隧洞动力响应有较大影响,故隧洞的动力分析中不能忽略衬砌作用。     

综采一次采全高顶板导水裂缝带发育高度的计算公式及适用性分析

确定煤层顶板导水裂缝带高度可为顶板防治水、采掘工程布置、防水煤柱留设以及瓦斯抽采设计提供依据。采用井下仰孔注水测渗漏法,实测山西西山煤田镇城底矿8煤导水裂缝带高度为57.98 m,其中冒落带高度16.72 m,裂隙带高度41.26 m。依据实测结果并收集了8个矿综采一次采全高中硬覆岩下导水裂缝带高度数据,利用数理统计回归分析的方法,得出了适用于综采一次采全高中硬覆岩下导水裂缝带高度计算的经验公式,并与《煤矿安全规程》中相应经验公式进行对比分析,结果表明,该公式适用性好,而《煤矿安全规程》中有关公式应用于中厚煤层综采一次采全高开采条件预测,其误差较大。     

混凝土面板堆石坝中过渡区的渗流控制作用研究

在面板完好的条件下,面板堆石坝坝体的渗透稳定性很容易满足要求;在面板止水破损和面板失效的不利条件下,过渡区的渗流控制作用对于大坝的渗透稳定性具有关键意义。结合水布垭大坝实例,通过层间系数的分析,认为必须通过试验研究过渡料对垫层料的反滤保护作用。通过反滤试验研究了水布垭全级配过渡料对垫层料的反滤效果和渗透变形规律,结合已发表的研究成果进行综合分析,探讨了过渡区的渗流控制作用机制：过渡料与主堆石区一起,可对坝体起到很好的排水作用;在面板止水破损和面板失效的不利条件下,垫层料内部可能会发生颗粒迁移和内部结构调整,但在过渡料的反滤保护作用下可维持渗透稳定;初次遇到这种工况时,过渡区自身会有少量细粒流失,但其骨架将维持稳定,借助于主堆石区的支撑作用,过渡区将继续发挥其反滤和排水的双重作用。     

隧道开挖引起邻近单桩水平反应分析

隧道开挖会降低邻近桩基承载力,如何更为合理评价桩基水平附加响应是需要解决的问题。基于Pasternak双参数地基模型和三折线弹塑性荷载传递模型,采用两阶段分析法,并考虑侧向土体作用及地基土层的非均质特性,提出了更符合实际的单桩水平反应简化分析方法。通过与Winkler地基梁法及边界元法的对比分析,验证了方法的合理性。结合对单桩水平反应的多种影响因素进行参数分析,通过各因素相应的修正系数来对基准工况中单桩最大水平反应进行修正,得到计算工况中单桩的最大水平位移和最大弯矩。分析结果表明,桩基水平位移计算时可忽略侧向土体作用,而弯矩计算时应予以考虑;桩基计算工况的最大水平位移 最大弯矩 与平均地层损失比 呈现线性关系,而与隧道半径R、隧道轴线深度H、桩距隧道中心线距离x及桩身柔度系数 均呈现非线性关系。     

Transient dynamic response of multilayered saturated media subjected to impulsive loadings

This paper presents a stable and efficient method for calculating the transient solution of layered saturated media subjected to impulsive loadings by means of the analytical layer element method. Starting with the field equations based on Biot's linear theory for porous, fluid‐saturated media, and the seepage continuity equation, an analytical layer element for a single layer is established by applying Laplace‐Hankel integral transform. The global stiffness matrix in the transform domain for a layered saturated half‐space subjected to a transient circular patch loading is obtained by assembling the layer elements of each layer. The displacements in the time domain are derived by Laplace‐Hankel inverse transform of the global stiffness matrix. Numerical examples are conducted to verify the accuracy of the method and to demonstrate the influences of type of transient loading, buried depth of loading, permeability, and stratification of materials on the transient response of the multilayered saturated poroelastic media.     

瞬变电磁法在福建某铅锌矿井下勘查中的应用

老矿山深部、外围找矿是当前"以矿找矿"为重要方式。文章以福建某铅锌矿为例,通过坑道内开展小线框、大电流的瞬变电磁法获取电阻率异常,利用坑内钻进行验证,取得了良好的找矿效果,为老矿山勘探提供了新的有效的物探方法。     

Time-domain analysis of velocity waves in a pipe pile due to a transient point load

The propagation of stress waves in a pipe pile subjected to a transient point load cannot be expressed using traditional one-dimensional (1D) wave theory. This paper presents an analytical solution used to investigate the wave propagation in a pipe pile under an axial point load. The soil resistance is simulated using the Winkler model, and the excitation force is simulated with a semi-sinusoidal impulse. A time-domain analytical solution for the three-dimensional wave equation is derived using the separation of variables and variation of constants methods. The solution is verified with a frequency domain analytical solution in which the time-domain response is calculated by numerical Fourier inverse transformation. Furthermore, the solution proposed in this paper is compared with the results of model testing and 3D FEM analysis. The comparisons show that the analytical solution proposed in this study agrees well with the results of previous studies. The proposed solution is subsequently applied in case studies. The vertical velocity responses in the circumferential and axial directions are analyzed to reveal the propagation characteristics of transient waves in the pipe pile. Moreover, the effects of the location and period of the excitation force, the side and tip resistances and high-order modes are studied in detail.     

非饱和土中圆柱形衬砌隧道的瞬态动力响应

在以往关于圆柱形衬砌隧道的瞬态动力响应中,衬砌周围土体大多假定为弹性介质或饱和介质。然而,自然界中的土体大多为非饱和介质。考虑土体与衬砌结构的动力相互作用及动荷载引起的附加质量密度的影响,研究了瞬态荷载作用下非饱和土中无限长深埋圆柱形衬砌隧道的动力响应。基于多孔介质混合物理论和连续介质力学理论,建立了非饱和土中圆柱形衬砌隧道受到瞬态荷载作用时衬砌及周围土体的控制方程,利用Durbin数值反演法得到了衬砌及土体在时间域的动力响应。数值分析了饱和度对瞬态荷载下径向位移、径向应力、环向应力和孔隙水压力的影响。结果表明：饱和度对衬砌及周围土体的瞬态响应影响显著;饱和度对径向位移沿径向的衰减影响较小,对环向应力和孔隙压力沿径向的衰减影响较大。     

冀东沉积变质型铁矿床瞬变电磁响应研究

本文介绍瞬变电磁方法在冀东沉积变质型铁矿勘查中的应用。根据冀东地区成矿地质背景,以及BIF型铁矿的矿体形态、产状、赋存部位、规模大小及含矿岩层特征,建立了层状模型、透镜体模型与向形模型三种地质模型。将地质模型转化为可处理的地球物理模型,按实际地质情况改变模型参数,完成了瞬变电磁的时域二维正演计算。分析了三种模型在多种情况下（低阻覆盖层、不同倾角、不同深度、发射源特征和不同电阻率）的瞬变电磁响应特征。结果表明,低阻覆盖层对于瞬变电磁场的扩散有一定的屏蔽作用,因而减小探测深度;随着矿体倾角的逐渐增大,瞬变电磁响应强度逐渐减弱,水平板状矿体比垂直板状矿体的响应要更为明显;勘探效果随着地质体埋深的增加而逐渐减弱;发射磁矩的大小对于瞬变电磁场的强弱产生直接影响,在实际应用中需要结合多方面因素,选择最佳的发射边长来达到最佳的勘查效果。利用冀东司家营地区进行的瞬变电磁勘察数据,研究了该地区铁矿床瞬变电磁响应特征,验证了上述模型的结论。     

地幔转换带:地球深部研究的重要方向

地幔转换带是联系上下地幔的纽带,对于认识整个地幔的组成和演化、地幔对流、岩石圈深俯冲及深源地震等地球深部动力学问题具有重要意义。一般认为,转换带地震不连续面主要与橄榄石的高压相变密切相关。最新的高温高压实验研究表明,地幔中非橄榄石组分的相变,如辉石和石榴子石的相变,对不连续面的深度和宽度以及转换带内的波速和密度梯度也起到很大的影响。另外地幔全岩成分、端员组分、温度和水也对相变和不连续面具有重要影响,这些精细的实验研究成果更好地解释了转换带地震不连续面一些相对局部的性质和变化,促进了我们对地球深部性质和动力学过程的了解。因为缺少直接来自地球深部的样品,而地球物理和地球化学研究也有它们的相对局限性,所以高温高压实验仍然是我们了解地球深部成分和性质的重要手段之一。     

列车动载作用下交叠隧道动力响应数值模拟

采用上海地铁某区间隧道现场实测振动加速度数据，对南浦大桥近距离交叠隧道在列车振动荷载作用下的动力响应进行了有限元数值模拟。模拟结果表明：上下重叠隧道在动载作用下相互影响显著；随着隧道间净距的增加，相互影响逐渐减弱；对隧道结构而言，土压静载是结构设计的控制荷载，列车振动引起的附加内力增幅较小。     

Bacterial response to contrasting sediment geochemistry in the Central Indian Basin

In order to investigate whether geochemical, physiographic and lithological differences in two end‐member sedimentary settings could evoke varied microbe–sediment interactions, two 25 cm long sediment cores from contrasting regions in the Central Indian Basin have been examined. Site TVBC 26 in the northern siliceous realm (10°S, 75·5°E) is organic‐C rich with 0·3 ± 0·09% total organic carbon. Site TVBC 08 in the southern pelagic red clay realm (16°S, 75·5°E), located on the flank of a seamount in a mid‐plate volcanic area with hydrothermal alterations of recent origin, is organic‐C poor (0·1 ± 0·07%). Significantly higher bacterial viability under anaerobic conditions, generally lower microbial carbon uptake and higher numbers of aerobic sulphur oxidizers at the mottled zones, characterize core TVBC 26. In the carbon‐poor environment of core TVBC 08, a doubling of the ¹⁴C uptake, a 250 times increase in the number of autotrophic nitrifiers, a four‐fold lowering in the number of aerobic sulphur oxidizers and a higher order of denitrifiers exists when compared with core TVBC 26; this suggests the prevalence of a potentially autotrophic microbial community in core TVBC 08 in response to hydrothermal activity. Microbial activity at the northern TVBC 26 is predominantly heterotrophic with enhanced chemosynthetic activity restricted to tan‐green mottled zones. The southern TVBC 08 is autotrophic with increased heterotrophic activity in the deepest layers. Notably, the bacterial activity is generally dependent on the surface productivity in TVBC 26, the carbon‐rich core, and mostly independent in TVBC 08, the carbon‐poor, hydrothermally influenced core. The northern sediment is more organic sink‐controlled and the southern sediment is more hydrothermal source‐controlled. Hydrothermal activity and associated rock alteration processes may be more relevant than organic matter delivery in these deep‐sea sediments. Thus, this study highlights the relative importance of hydrothermal activity versus organic delivery in evoking different microbial responses in the Central Indian Basin sediments.     

北京延庆新城规划区场地动力响应数值模拟

在地震多发的中国内陆环境下,场地稳定性评价越来越引起重视。为了研究北京延庆新城规划区大型场地动力响应特征,在分析延庆新城规划区第四纪覆盖层和断裂的空间分布规律基础上,基于数值模拟方法,运用有限差分数值模拟软件FLAC3D建立了规划区三维仿真模型,并对新城规划区场地动力响应进行了仿真,最后通过定义场地速度响应系数来刻画场地动力响应特征。结果表明：对于“土岩组合”的典型场地,在低频剪切波的激励下,第四纪覆盖层的厚度将引起不同程度的场地速度响应,第四纪覆盖层越厚,场地速度响应系数越大,动力放大程度越高;对于下伏断裂的复杂场地,剪切波传播路径变得极其复杂,断裂对地表速度响应系数有放大作用,放大程度与断裂分布形式和发展规模有关。     

Migration of induced-infiltration stream water into nearby aquifer due to a transverse horizontal well in loess areas

Analysis of the migration paths of stream water introduced into a transverse horizontal well is important to better understand the interactions between streams and aquifers. This paper presents a method of using particle-tracking techniques to evaluate the transport of stream water that infiltrates through a transverse horizontal well that runs transverse to a stream and extends from the stream banks. By conceptualizing the horizontal well as a discrete pipe network, MODFLOW is coupled with the pipe flow equations that govern the movement of water in the horizontal well, and this coupled seepage-pipe flow model is used to calculate the transient groundwater flow field. MODPATH is then used to record the locations of each of the water particles from the interface between the stream and the aquifer. The path lines, travel times, influence zones and the production of infiltrated stream water are determined to depict the migration process. The results suggest that the infiltrated stream water that originates from different stream transects located upstream and downstream from the horizontal well has different migration characteristics, as does the infiltrated stream water coming from different locations on the same stream transect. Eventually, the pumpage of the horizontal well consists partly of the infiltrated stream water and groundwater inflow from the upstream model boundary. The groundwater enters the horizontal well through the two end segments of the horizontal well, and the infiltrated stream water enters the middle segment of the well. The pumped water is still a mixture of infiltrated stream water and groundwater, even if the pumping lasts for a long period. The hydrochemistry of the infiltrated stream water cannot be simply used to evaluate the hydrochemistry of the water pumped from a transverse horizontal well.