级配碎石填料大三轴试验及累积塑性应变预测模型

级配碎石作为重载铁路基床表层的主要填料,其受列车荷载的影响最大。因此,研究级配碎石在循环荷载作用下的动力行为及累积塑性应变演化特征变得尤为重要。首先,通过制备不同细粒含量的级配碎石填料,开展一系列大型动三轴试验,探究细粒含量、围压及动应力幅值对循环荷载作用下试样累积塑性应变的耦合影响机制。其次,基于塑性安定理论,确定不同应力水平下试样的动力行为,得到考虑围压及细粒含量参数的塑性蠕变状态临界动应力计算模型。最后,结合试验数据,建立考虑应力水平及细粒含量参数的塑性蠕变动力行为累积塑性应变预测模型,并明确各参数的物理意义。其研究成果可为既有重载铁路路基健康状态评估及考虑强度、变形综合控制的路基结构设计提供参考。     

淮南顾北矿F104断层两侧岩溶水化学形成机制及导隔水性评价

利用断层两盘岩溶水化学特征判断其导隔水性对于我国华北型煤田水害防治具有十分重要的实践意义。以顾北矿F₁₀₄断层两侧太原组岩溶地下水为研究对象,在分析断层两盘水文地质条件基础上,采用Piper三线图、离子组合比和主成分法,分析了主要组分来源及水-岩作用差异性,并采用PHREEQC软件对岩溶地下水进行反向水化学模拟。结果表明:南北区岩溶水均存在方解石和白云石的溶解和沉淀现象,南区阳离子交换吸附和脱硫酸作用程度强于北区,而北区黄铁矿氧化和岩盐溶解作用较南区明显,南北两区水化学环境及水-岩作用存在显著差异,进而推断F₁₀₄断层具有较好的阻水性,且影响了其两侧的氧化-还原环境及温度差异,控制着地下水径流方向和水-岩作用程度。      

Poynting and polarization vectors based wavefield decomposition and their application on elastic reverse time migration in 2D transversely isotropic media

With the progress in computational power and seismic acquisition, elastic reverse time migration is becoming increasingly feasible and helpful in characterizing the physical properties of subsurface structures. To achieve high-resolution seismic imaging using elastic reverse time migration, it is necessary to separate the compressional (P-wave) and shear (S-wave) waves for both isotropic and anisotropic media. In elastic isotropic media, the conventional method for wave-mode separation is to use the divergence and curl operators. However, in anisotropic media, the polarization direction of P waves is not exactly parallel to the direction of wave propagation. Also, the polarization direction of S-waves is not totally perpendicular to the direction of wave propagation. For this reason, the conventional divergence and curl operators show poor performance in anisotropic media. Moreover, conventional methods only perform well in the space domain of regular grids, and they are not suitable for elastic numerical simulation algorithms based on non-regular grids. Besides, these methods distort the original wavefield by taking spatial derivatives. In this case, a new anisotropic wave-mode separation scheme is developed using Poynting vectors. This scheme can be performed in the angle domain by constructing the relationship between group and polarization angles of different wave modes. Also, it is performed pointwise, independent of adjacent space points, suitable for parallel computing. Moreover, there is no need to correct the changes in phase and amplitude caused by the derivative operators. By using this scheme, the anisotropic elastic reverse time migration is more efficiently performed on the unstructured mesh. The effectiveness of our scheme is verified by several numerical examples.     

基于解耦传播的波场分解方法在VTI介质弹性波逆时偏移中的应用

由于弹性波逆时偏移更符合实际情况,而且转换波的成像结果有更高的分辨率,因此弹性波逆时偏移越来越受到重视。然而,弹性波逆时偏移需要多波多分量数据,为了减少成像结果中的串扰假象,在逆时偏移过程中进行P波和S波分解就变得非常必要。结合基于向量的激发振幅成像条件,我们把基于解耦传播的波场分解方法应用到弹性波逆时偏移中,并对比了其在各向同性介质和横向各向同性（VTI）介质中的应用效果。结果说明,该方法可以在各向同性介质中完全分解P波和S波,并保留波场的向量信息。虽然在VTI介质中有较小的分解残余,但是该分解残余不会在逆时偏移结果中产生明显的串扰;因此,这种波场分解方法可以应用于各向同性介质和VTI介质弹性波逆时偏移。该方法是在时间空间域实现的,可以在波场传播过程中直接对P波和S波进行分离,应用方便,计算效率高。与利用Helmholtz分解的弹性波逆时偏移相比,该方法避免了在PS波成像结果中的极性反转问题。在复杂Hess VTI模型的逆时偏移结果中,高速岩体和断层的成像清晰,甚至是两个低速薄夹层也能较好成像;这说明该方法对复杂介质具有较好的适应性。PS波成像结果中的各向异性体成像清晰,说明各向异性介质弹性波逆时偏移可以对传统逆时偏移不能很好成像的构造进行成像。     

湖相深水细粒物质的混合沉积作用探讨*

沉积物的混合是自然界的普遍现象,湖盆中广泛发育的深水细粒沉积岩本身就是一类混积岩。以东营凹陷古近系沙河街组三段下亚段—沙河街组四段上亚段细粒沉积岩为研究对象,通过厘米级岩心观察描述、小型沉积构造解剖、岩石薄片观察、X射线衍射全岩矿物分析及微量元素测试等方法,研究细粒物质的产出状态和混合方式;分析湖盆流体、气候及水体性质对细粒物质迁移、混合、沉积的控制作用,尝试探讨细粒物质的混合沉积机制。结果表明,湖相深水细粒沉积岩既有物质成分上的混合,也有结构的混合,且在宏观与微观的不同尺度均存在混合;混合沉积作用有均匀混合、纹层叠置混合、不均匀团块状混合等类型。纹层叠置混合沉积是最主要的混合沉积方式,依据纹层接触关系、所占比例及矿物产出状态可分为泥砂—灰纹层叠置混合型、泥—灰纹层叠置混合型、泥砂粒序—灰纹层叠置混合型、灰—泥—云纹层叠置混合型等。湖相深水细粒物质的混合沉积作用类型多且往往受多个因素同时控制,气候及水动力条件是控制细粒混合沉积岩发育的最主要因素,不同流体(浊流和底流)作用下的细粒沉积物混合作用存在差异。气候引起湖水性质变化及水体分层,从而控制不同类型细粒物质的絮凝沉降及化学沉积。不同构造部位、不同水体深度的混合作用不同;相同构造部位在垂向上也存在混合沉积方式的差异。     

吉林省白山市板石沟铁矿断裂构造地球化学特征

断裂构造中元素的迁移变化规律是构造地球化学研究的主要内容.白山市板石沟铁矿断裂构造发育,是开展断裂构造地球化学研究的有利地区.通过对板石沟铁矿17矿组和赵家沟矿组典型逆断层剖面测量,采集构造岩和周围岩石,分析常量元素和微量元素,利用构造地球化学剖面法、质量等比线法和特征元素比值来反映元素在逆断层中分布特征和迁移变化规律.通过分析认为在逆断层中常量元素SiO₂、Fe₂O₃、CaO、Na₂O亏损,Al₂O₃、K₂O富集,微量元素中Rb、Sr等离子半径较大元素富集,离子半径较小元素Co、Cr、Ni亏损,K₂O/Na₂O、V/Cr、Rb/（Ni+Co）在逆断层中呈现出高值,SiO₂/Al₂O₃、（Fe₂O₃+CaO+MgO）/Al₂O₃呈现出低值.依据这些构造地球化学特征可以用来判断断裂构造的存在,为断裂构造地球化学研究和板石沟铁矿勘查提供构造地球化学依据.     

基于CT三维重建与逆向工程技术的煤体数字模型的建立

为了建立能够表征煤体真实孔隙结构的数字模型,进而进行数值模拟研究,通过μCT225kVFCB高精度CT系统扫描得到了大柳塔煤矿长焰煤CT数据,可观测到的最小孔隙直径为1.94 μm。使用基于Matlab语言的三维重建程序结合逆向工程技术,提出了一种将煤体CT三维数据转换为CAD数字模型的方法。以Ansys建立的煤体有限元模型为例,对煤体瓦斯渗流进行了模拟,分析了煤体孔隙内的速度及压力分布规律,并计算了沿X、Y、Z方向的渗透系数。计算结果表明：在微观尺度下（< 100 μm）煤体渗透系数呈现各向异性,其受煤体结构的影响较明显。提出的基于CT三维重建结合逆向工程技术构建的煤体CAD数字模型不仅可进行有限元分析,同时也可以被EDEM等离散元分析软件所使用,拓宽了煤体CT三维数据的应用范围,丰富了煤体在微观尺度上的研究方法。     

Development of experimental apparatus about reverse circulation bit

A set of experimental apparatus on reverse circulation bit are developed, in order to lucubrate the mechanism of the new type reverse circulation bits, and the structure of the bits influencing the ability of taking core and carrying powder.Both the major structure of the equipment and the procession of experiment are described.     

Bifurcation modelling in a meandering gravel–sand bed river

The Rhine bifurcation at Pannerden forms the major distribution point for water supply in the Netherlands, distributing not only water and sediment but also flooding risks and navigability. Its morphological stability has been a concern for centuries. We present experiences from more than two decades of numerical morphological modelling of this bifurcation with a gravel–sand bed and a meandering planform. Successive computations have shown the importance of upstream approach conditions, the necessity to include physical mechanisms for grain sorting and alluvial roughness, and the need to assume a thicker active layer of the river bed than is suggested by laboratory flume experiments using a constant discharge. The active layer must be thicker in the model to account for river bed variations due to higher‐frequency discharge variations that are filtered out in morphological modelling. We discuss limitations in calibration and verification, but argue that, notwithstanding these limitations, 2D and 3D morphological models are valuable tools, not only for pragmatic applications to engineering problems, but also for revealing the limitations of established knowledge and understanding of the relevant physical processes. The application of numerical models to the Pannerden bifurcation appeared to reveal shortcomings in established model formulations that do not pose particular problems in other cases. This application is therefore particularly useful for setting the agenda for further research. Copyright © 2012 John Wiley & Sons, Ltd.     

基于GPU并行加速的叠前逆时偏移方法

为了提高复杂地下介质的成像精度和偏移算法的计算效率,提出可高效对地下复杂构造进行准确成像的GPU加速叠前逆时偏移方法.该方法采用双程声波方程进行波场延拓,突破倾角限制,借助于高阶有限差分方法实现叠前逆时偏移成像;利用GPU(Graphic Processing Unit)并行加速技术对波场延拓和成像进行计算,相比于传统算法,其计算效率有较大提高,可以解决叠前逆时偏移算法计算量过大问题;在获取波场信息过程中,也采用随机边界条件,实施以计算换存储策略,解决逆时偏移计算中的海量存储问题.模型测试结果表明,该方法能够高效和高精度地对地下复杂地质体成像.