圆弧形沉积场地对平面瑞利波散射的解析分析

分别采用Biot饱和多孔介质动力学理论和单相介质弹性动力学理论模拟层状沉积谷场地和 周围场地,利用波函数展开法,得出了层状饱和沉积场地对Rayleigh波散射的解析解．进 行参量分析,研究了无量纲入射波频率、层状沉积层排列顺序及相对刚度和厚度等因素对 Rayleigh波散射效应的影响.     

层状盐岩力学特性研究进展

盐岩具有孔隙度低,渗透率小,损伤自恢复和塑性变形能力大等特性.本文着眼于深部盐岩能源地下储备,在简要介绍国内外盐岩力学特性研究现状基础上,着重综述了近期关于层状沉积型盐岩工程力学特性研究的进展.层状盐岩压缩试验表明泥质硬石膏夹层对盐岩体的变形和破坏特性有明显的影响,揭示了复合岩体的变形和破坏机制;层状盐岩流变试验表明层状盐岩的蠕变主要由盐岩层控制,硬夹层的存在对溶腔围岩的长期蠕变起到抑制作用;为了深入了解界面的力学特性,开展了层状盐岩直接剪切试验、间接拉伸试验和界面微观分析试验,试验表明层状盐岩体中盐岩夹层界面具有较强的黏结力,这十分有利于盐岩溶腔的密闭性和稳定性;针对特殊的层状岩体提出了复合岩体Cosserat介质扩展本构模型,并应用于层状盐岩构造中能源储库稳定性分析中.最后指出了层状盐岩工程力学特性研究中值得关注的几个重点研究方向.      

二维地表局部不规则区域对P,SV波传播的影响

本文将转换矩阵法加以推广,用来求解半空间表面局部不规则区域所引起的P、SV波的散射透射问题。计算讨论了孤突山丘和沉积谷地对地震波的放大作用,结果与实际震害调查中观测到的现象基本一致。     

界面圆孔对SH波散射的远场解

采用格林函数方法研究界面圆孔为ＳＨ波散射的远场解答,在构造格林函数并求解界面圆孔对ＳＨ波散射及其近场解答的基础上,继续研究该问题的散射远场,给出了散射波远场位移模式和散射截面的解答,通过具体算例,分析了不同材料组合而成的界面圆孔对ＳＨ波散射的远场特性。     

横观各向同性层状场地对入射SH波的响应分析

本文采用横观各向同性层状弹性模型模拟半空间之上的层状了，推导了在ＳＨ波入射时这种场地土的动力刚度矩阵及基岩输入运动时场地呼应的计算公式，算例表明，横观各向同性层状场地与各向同性层状了频谱特性有明显的区别，应当引起重视。     

地下结构地震响应的计算模型

地震时地下结构在围岩的约束作用下发生变形,其动态特性与地面结构有很大不同.自二十世纪七八十年代以来,地下结构抗震设计与研究取得了很大进展.总的看来,工程设计中普遍采用的计算方法与设计导则大都建立在比较简单假定的基础上,实际的岩土介质条件都是十分复杂的.地下结构抗震研究的近期成果则表现在对地下结构动力分析中的波动散射问题提出了波函数展开法以及边界积分方程方法等多种计算方法.但计算相对复杂,在工程设计中的推广应用有一定困难.此文致力于地下结构计算模型的改进,使之具有良好的计算精度与效率,又便于工程应用.为此,提出了一种地下结构抗震响应分析的新的计算模型.模型具有较广泛的适应性,可以进行河谷、孔洞、地下铁道、隧洞等地下结构的散射与绕射分析.对于复杂层状的地质条件,提出了格林函数求解简便而有效的方法.数值算例论证了方法的精度和效率.     

辛烷基苯酚聚氧乙烯醚与正癸醇层状液晶的结构及润滑性能研究

用小角Ｘ射线衍射和自旋标记电子自旋共振（ＥＳＲ）方法测定辛烷基苯酚聚氧乙烯醚与正癸醇体系层状液晶的结构。用高速环－块摩擦磨损试验机考察了不同组分含量的层状液晶对铝合金－钢摩擦副的润滑作用。结果表明：随着水含量的增加,层状液晶稳定性降低,润滑效果变差;随着辛烷基苯酚聚氧乙烯醚含量的增加,层状液晶的稳定性增加,润滑性能提高。     

大延伸非均匀介质中地震波全弹性散射理论Ⅱ——弹性波多次散射理论

推出大延伸非均匀连续介质的弹性波能量传输表达式,并以此为基础建立并发展了相应的弹性动力学能量传递理论.构造了一个基于非均匀薄层或非均匀相屏单次散射迭代法的多次散射模型.该模型既适用于弱散射,也适用于强散射;既适用于普通散射,也适用于转换散射;尽管高频情况下只考虑普通散射及前向散射.应用该模型计算了弹性多次散射的能通量,处理了散射衰减问题.数值实验的结果表明,短周期地震图上的尾波主要来源于S波散射.     

大延伸非均匀介质中地震波全弹性散射理论II-弹性波多次散射理论

推出大延伸非均匀连续介质的弹性波能量传输表达式,并以此为基础建立并发展了相应的弹性动力学能量传递理论.构造了一个基于非均匀薄层或非均匀相屏单次散射迭代法的多次散射模型.该模型既适用于弱散射,也适用于强散驰 既适用于普通散射,也适用于转换散射;尽管高频情况下只考虑普通散射及前向散射.应用该模型计算了弹性多次散射的能通量,处理了散射衰减问题。数值实验的结果表明,短周期地震图上的尾波主要来源于S波散射。     

多个椭圆柱波浪力的一种解析解

波浪在大尺寸结构表面产生不可忽略的散射波, 该散射波在多柱体体系中继续传播, 并在同体系中的其他柱体上产生高次散射波. 本文基于椭圆坐标系和绕射波理论首先推导了波浪作用下椭圆单柱体产生的散射波压力公式, 随后考虑该散射波在多柱体系中的传播, 将其视为第二次入射波, 推导出柱体上第二次散射波压力公式, 同理可以推导出高次散射波压力公式, 最后得到椭圆多柱体波浪力解析解, 并用数值解验证了本文解析方法的正确性. 本文以双柱体和四柱体体系为例, 分析了不同参数(波数、净距、波浪入射角度等)下, 高次散射波对柱体上波浪作用的影响. 结果表明: 波数较大的情况下, 高次散射波引起柱体上的波浪力不能忽略; 结构间距较大的情况下, 虽然高次波的作用有减小的趋势但仍然明显; 高次散射波来自多个柱体对入射波的散射, 柱体数目的增加后, 高次波的影响会增加, 结构所受的高次波作用因参数变化而起的波动会变剧烈; 高次波对上游柱体波浪力的贡献较对下游柱体的贡献大.      

AN ANALYTICAL SOLUTION FOR THREE-DIMENSIONAL DIFFRACTION OF PLANE P-WAVES BY A HEMISPHERICAL ALLUVIAL VALLEY WITH SATURATED SOIL DEPOSITS

An analytical solution for the three-dimensional scattering and diffraction of plane P-waves by a hemispherical alluvial valley with saturated soil deposits is developed by employing Fourier-Bessel series expansion technique. Unlike previous studies, in which the saturated soil deposits were simulated with the single-phase elastic theory, in this paper, they are simulated with Biot's dynamic theory for saturated porous media, and the half space is assumed as a single-phase elastic medium. The effects of the dimensionless frequency, the incidence angle of P-wave and the porosity of soil deposits on the surface displacement magnifications of the hemispherical alluvial valley are investigated. Numerical results show that the existence of a saturated hemispherical alluvial valley has much influence on the surface displacement magnifications. It is more reasonable to simulate soil deposits with Biot's dynamic theory when evaluating the displacement responses of a hemispherical alluvial valley with an incidence of P-waves.     

Seismic responses of a hemispherical alluvial valley to SV waves： a three-dimensional analytical approximation

An analytical solution to the three-dimensional scattering and diffraction of plane SV-waves by a saturated hemispherical alluvial valley in elastic half-space is obtained by using Fourier–Bessel series expansion technique. The hemispherical alluvial valley with saturated soil deposits is simulated with Biot’s dynamic theory for saturated porous media. The following conclusions based on numerical results can be drawn: (1) there are a significant differences in the seismic response simulation between the previous single-phase models and the present two-phase model; (2) the normalized displacements on the free surface of the alluvial valley depend mainly on the incident wave angles, the dimensionless frequency of the incident SV waves and the porosity of sediments; (3) with the increase of the incident angle, the displacement distributions become more complicated; and the displacements on the free surface of the alluvial valley increase as the porosity of sediments increases.The project was supported by the National Natural Science Foundation of China (50478062 and 10532070) and Open Fund at the Key Laboratory of Urban Security and Disaster Engineering (Beijing University of Technology), Chinese Ministry of Education. The English text was polished by Keren Wang.     

Single- and Dual-domain Models of Solute Transport in Alluvial Sediments: the Effects of Heterogeneity Structure and Spatial Scale

Fine-scale heterogeneity of alluvial aquifers controls solute transport in groundwater at the scales relevant for practical applications: the architecture of sedimentary structures might create preferential flow paths (PFPs) or hydraulic barriers, which affect the breakthrough curves (BTCs). Objective of this paper was the assessment of the relevance of single- and dual-domain models for different heterogeneity patterns and scale lengths in alluvial sediments. Three case studies have been analysed with a classical single-domain model (SDM) and with three dual-domain models (DDMs): a dual-porosity model (DPorM) and two dual-permeability models (DPerM), which differ for the presence or the absence of solute exchange between the two domains. The first case study includes numerical tracer tests in metre-scale blocks of alluvial sediments; the second is a laboratory experiment of tracer injection in a decimetre-scale column of homogeneous sand; the third is a field tracer test performed at hectometre scale at the Cape Cod site. The relevance of the solute exchange in the DDMs is analysed with the characteristic advection and exchange times and with the Péclet and Damköhler numbers. The SDM is satisfactory for alluvial sediments with unstructured heterogeneity. The uncoupled DPerM is shown to be a better approach than the DPorM in sediments with PFPs; in this case, the coupled DPerM does not improve significantly the results of the uncoupled DPerM. A minor difference between the results of the three DDMs is observed for sediments in which the non-Fickian behaviour is not clearly determined by the presence of PFPs.     

南阳膨胀土的宏观结构与路堑边坡病害治理

南阳盆地是我国膨胀土主要分布地区之一,在宁(南京)—西(西安)铁路施工工程地质调查中,发现南阳地区上第三系中新统湖相沉积膨胀土中发育的构造裂隙、中更新统冲洪积膨胀土中发育的卸荷裂隙和全新统湖沼相膨胀土中发育的收缩裂隙控制了路堑边坡病害的形式、规模和破坏特征。施工过程中采取了针对性措施治理边坡病害,取得了明显的工程效果。     

Role of Molecular Diffusion in Contaminant Migration and Recovery in an Alluvial Aquifer System

Highly-resolved simulations and flow and transport in an alluvial system at the Lawrence Livermore National Laboratory (LLNL) site explore the role of diffusion in the migration and recovery of a conservative solute. Heterogeneity is resolved to the hydrofacies scale with a discretization of 10.0, 5.0 and 0.5m in the strike, dip and vertical directions of the alluvial-fan system. Transport simulations rely on recently developed random-walk techniques that accurately account for local dispersion processes at interfaces between materials with contrasting hydraulic and transport properties. Solute migration and recovery by pump and treat are shown to be highly sensitive to magnitude of effective diffusion coefficient. Further, transport appears significantly more sensitive to the diffusion coefficient than to local-scale dispersion processes represented by a dispersivity coefficient. Predicted hold back of solute mass near source locations during ambient migration and pump-and-treat remediation is consistent with observations at LLNL, and reminiscent of observations at the MADE site of Columbus Air Force Base, Mississippi. Results confirm the important role of diffusion in low-conductivity materials and, consequently, its impact on efficacy of pump-and-treat and other remedial technologies. In a typical alluvial system on a decadal time scale this process is, in part, fundamentally nonreversible because the average thickness of low-K hydrofacies is considerably greater than the mean-square length of penetration of the solute plume.     

一维河网泥沙输移模式研究

推导了一种显式的河网 泥沙输移递推计算方法, 该方法在水动力学计算结果所确定的汊点类型基础上, 直接计算每 个河段中逐个节点的不平衡泥沙输沙过程以及悬沙和床沙的级配调整, 克服了传统方法中必 须通过首末断面含沙量关系确定河网悬沙矩阵求解的困难. 将该泥沙输移模式的一维河网水 沙数学模型, 应用于长江三峡下游荆江-洞庭湖河网区域, 并取得了较好的计算结果.在模型 验证之后, 进一步讨论了采用新的泥沙输移计算模式和原有泥沙输移计算模式在计算 时间上和计算内容方面的差别.     

Effect of local surface and subsurface Irregularities on the propagation of P, SV waves

The transition matrix method is extended to study the scattering problem of P, SV waves in half-space with two-dimensional local surface or subsurface irregularity. The method presented here possesses the advantage of high accuracy with low computational cost as compared with the boundary element method. The amplification effect of hills and alluvial valleys on seismic waves is discussed. The results are in agreement with those observed in earthquakes in China.     

川藏公路培龙沟路段堆积物的分形特征及其地质意义

川藏公路培龙沟路段有多种不同类型的堆积物。本文应用分形理论,探讨了培龙沟路段泥石流堆积物、冰碛堆积物、冲洪积堆积物以及坡积或者残坡积物的分形特征。通过粒度分析法计算出不同类型堆积物的粒度分维,得到泥石流堆积物分维最大,冰碛堆积物分维较大,坡积或者残坡积堆积物较小,冲积物或者洪积物分维最小的规律。最后系统论述了堆积物粒度分维的地质意义,认为堆积物粒度分维是对堆积物物质组成的复杂性和自组织性、堆积物形成过程和形成时间以及泥石流、冰川、河流和洪水等搬运能力和运动过程的反映和度量。该研究为野外不同类型堆积物的区分、成因、形成过程等研究提供了一种新的方法,具有一定参考价值。