原位岩土CT及其关键技术探讨

当前应用工业X射线CT技术观测岩土内部微观结构和力学特性成为研究工程地质的热点课题。然而,现有CT技术的“笨、大、重、险、贵”限制了现场应用能力,且常规岩土工程勘察方法存在丢失或破坏原有地质信息的问题。本文提出原位CT技术的概念,并指出其在岩土工程勘察领域应用中的关键技术。基于超小型冷阴极脉冲式X射线管及成像设备搭建随钻原位CT实验平台,实验结果表明该方法能够实现原位岩心数字采样与CT快速重构。在此基础上明确后续研究重点和关键技术,主要包括2D/3D CT快速重构新理论和新方法,解析CT重构图像与岩土颗粒特性之间的关系以及局部精细结构重建算法,构建精确的原位岩心3D微观结构模型;结合3D打印技术制备原位置岩土准样本,研究等效准样本的力学特性;建立时-空四维岩土工程勘察数据库,引入人工智能算法形成具有学习和预测的反馈评价体系,对丰富当前岩土工程勘察方法和完善原位CT技术具有重要的科学意义。      

基于椭圆拟合和Hausdorff距离的图像匹配算法

图像匹配是逆向工程CAD建模领域的重要内容之一。针对CT图像包含多分叉轮廓的匹配问题,利用椭圆拟合来定量表达平面轮廓散乱点的整体形位信息,建立初步的轮廓森林;提出采用快速Hausdroff距离法来处理分枝问题从而形成完整的轮廓森林。实验结果表明,该算法对具有分叉现象的图像匹配具有良好的准确度和实时处理能力,对于岩芯CT、工业CT、医学CT等图像的三维重构都能有较好的适用性。     

基于CT数据的二次曲面拟合算法研究

二次曲面工件在工业中比较常见,为测量物体内部的二次曲面,本文采用工业计算机断层成像（CT）技术获取物体的断层图像序列,利用U-net图像分割网络获得断层图像上的目标区域,对分割结果的边缘进行检测和曲线拟合并堆叠成三维点集,通过曲面拟合获取物体曲面的三维空间坐标信息。研究结果表明,本文的方法能够有效地实现边界提取和界面参数的拟合工作,拟合误差在1%以内,相比传统方法有较大改进。     

基于递归的工业CT断层图像的层间处理算法

本文主要针对工业CT不同断层之间的同种材料,由于层间工件厚度差异,导致同种材料在CT重建后存在较大灰度差异的问题,提出基于递归的工业CT断层图像的层间处理算法。该算法首先根据先验信息:工件内部材料组成成分,建立内部结构一致性的判断模型,然后通过迭代求解,实现工件内部同种材料的一致性判断,最后通过VTK可视化平台进行验证。结果表明该层间处理算法是可行的,可以有效地提高三维可视化图像质量。     

基于微焦点CT与数据约束模型的古代家猪牙齿显微结构研究

本文对一例考古发掘出土的古代家猪下颌骨及牙齿进行了微焦点CT成像,通过加置滤波片有效减弱了线束硬化对CT图像的影响。基于数据约束模型（DCM）对样品三维结构进行了定量计算,获取了包含小于CT图像体元尺寸在内的样品跨尺度结构信息。对样品中孔隙及高吸收组分的联通特性进行了跨尺度计算,得到这两种组分的三维团簇分布。与常见的图像阈值分割法相比,DCM模型有效减弱了部分体积效应对图像分析的影响。本文研究结果为考古样品的内部形态测量、结构分析提供了数据基础,为考古样品的数字建模存档提供一种新的方法。      

利用混合法构建三维数字岩心(英文)

在弹性波有三维数字岩心描述了岩石的微观孔隙结构。X射线CT扫描是获取三维数字岩心最准确和直接的方法,但实验成本高。本文结合沉积过程模拟和模拟退火算法,提出了重建三维数字岩心的混合法,基于岩石二维图像重建三维数字岩心。利用岩石颗粒沉积算法构建初始数字岩心,作为模拟退火算法的初始状态。运用模拟退火算法调整岩石颗粒和孔隙的相对位置,使三维数字岩心与岩心二维图像具有相似的自相关函数,从而建立三维数字岩心。与传统模拟退火算法相比,该方法计算时间明显减小。运用局部孔隙度理论定量比较了重建数字岩心和岩心X射线微CT图像,两种数字岩心具有相似的均质性和孔隙连通性。利用有限元方法和格子玻尔兹曼方法分别模拟了重建三维数字岩心的地层因素和渗透率,数值模拟结果与实验结果相符。相比传统模拟退火算法,混合法重建数字岩心的传导特性更接近真实岩心的传导特性。     

煤岩CT图像二值化阀值选取及三维重构技术研究

运用工业cT实验系统（简称为DT-3）对煤样完成单轴加载实验,并对煤样进行一系列断层扫描,获取到不同截面处的破坏cT图像。基于图像分割技术,对图像的灰度级别设定不同的二值化阀值,得出不同阀值下的孔隙面积变化曲线图;并提出以拐点处对应的阀值作为裂隙图像二值化阀值时效果最佳。由上述研究结果结合灰度线性加权平均插值方法,编程实现了煤岩CT图像的三维重构,为后续研究煤岩裂隙三维表征提供了科学依据。     

X射线CT研究混凝土的试验设备问题

X射线CT研究混凝土的目的是通过CT扫描获得的CT图像,分析混凝土在不同荷载作用下细观裂纹的演化过程,解释混凝土宏观强度和变形特性.试验设备存在的问题是加载设备和CT机的功能难以同时充分发挥.采用现有的医用CT机和专用加载设备,可以初步实现对一、二级配混凝土动力加载过程中混凝土内部细观裂纹的实时观测.进一步的要求是需要研制专门的CT机,提高扫描速度;研制与其配套的加载设备,实现对二级配混凝土试件的动力压缩破坏的混凝土CT试验.     

工业计算机断层扫描仪(工业CT)研制报告

工业CT(ICT)是用于工业产品进行无损检测和探伤的先进仪器。ICT技术能紧密、准确地再现物体内部的三维立体结构,能够定量地提供物体内部的物理、力学等特性,如缺陷的位置及尺寸、密度的变化及水平,异型结构的形状及精确尺寸,物体内部的杂质及分布等。ICT的功能和特性在许多方面越过X光和超声检测,为航空、航天、兵器等工业领域的精密零部件的无损检测提供了新的手段。该技术研制成功并荣获1994年度亚洲CT技术十大科技进展成果奖。有关专家认为该技术居国内先进水平,与国际水平相当。我们研制开发的工业CT机已经为中国航空材料研究所、中国运载火箭技术研究院、兵器工业总公司等多家科研、生产单位进行了各种零件的测试。     

一种用于标定工业CT设备点云提取精度的配准及评价算法

基于工业CT测量数据的逆向建模技术广泛应用于军事、汽车制造、航空、航天等领域。目前,在基于工业CT点云数据的逆向重构精度验证和标定上,国内外缺少相关研究。本文提出了一种用于标定工业CT设备点云提取精度的配准及评价算法。基于CT扫描和三维光学扫描点云数据,在研究多种配准算法的基础上,总结手动选点粗配准和自动全局精配准相结合的配准算法:手动选择三个匹配点,利用坐标变换完成粗配准;用ICP算法完成自动精配准,并利用修正的Hausdorff距离为目标函数来评价配准结果。对基于七参数法和ICP算法的计算步骤做了详细说明,并赋以实例。最后,以自行设计的标准件为例,获得CT测量设备点云提取精度标定值,验证配准流程的适用性。      

Experimental investigation of three-dimensional propagation process from surface fault

Experimental study of the formation and propagation of three-dimensional (3D) faults is of great sig- nificance in the understanding of the propagation process developing from initial natural faults. In the study described in this paper, experimental investigations of 3D propagation processes of a type of surface fault are carried out under biaxial compression. The strain field near the surface fault is dy- namically measured and fully analyzed with a high-density Multi-Channel Digital Strain Gauge (MCDSG) and Digital Speckle Correlation Method (DSCM) based on the white-light image analysis. Simultane- ously the micro-fracture process involved in fault formation is observed by a 3D acoustic emission (AE) location system with a set of multi-channel whole-wave record equipment. The experimental results show that the 3D propagation process of surface fault differs greatly from that of the two-dimensional (2D) state and that a new more complicated type of 3D morphological characters and deformation mechanisms are produced. The 3D propagation process of surface faults may be divided into three stages: 1) the first stage of crack propagation initiated by wing cracks; 2) the conversion stage propa- gated by petal cracks; and 3) the second stage of crack propagation formed by shell-shaped fracture surface. The primary propagation patterns of the three stages are different. The corresponding defor- mation fields and micro-fracture distributions are likewise different. The fracture activities from petal cracks especially are of vital importance during surface fault propagation. This is also a key conversion state and marks an intrinsic difference between 2D-like and the 3D state in fault development.     

X射线岩石CT的历史与现状

采用X射线CT技术无损探测岩石内部结构和裂纹演化过程 ,起源于 2 0世纪 80年代后期 ,由最初对CT图像的认识逐步深化为对岩石裂纹演化规律的分析和应用研究。基于室内岩石试件扫描断面的CT图像 ,目前在岩石变形破坏过程的实时监测、加荷条件多样化、裂纹演化规律性、裂纹宽度的定量测量、岩石裂纹三维图像重建、损伤演化与损伤变量分析、CT成果应用研究等方面取得了一系列进展。岩石CT面临的主要问题是如何获得各种试验条件下精确的CT图像及其成果的应用研究。岩石CT的生命力在于自身理论、技术发展和在相关领域的应用程度     

A comparative study of buried structure in soil subjected to blast load using 2D and 3D numerical simulations

The response of underground structures subjected to subsurface blast is an important topic in protective engineering. Due to various constraints, pertinent experimental data are extremely scarce. Adequately detailed numerical simulation thus becomes a desirable alternative. However, the physical processes involved in the explosion and blast wave propagation are very complex, hence a realistic and detailed reproduction of the phenomena would require sophisticated numerical models for the loading and material responses. In this paper, a fully coupled numerical model is used to simulate the response of a buried concrete structure under subsurface blast, with emphasis on the comparative performance of 2D and 3D modeling schemes. The explosive charge, soil medium and the RC structure are all incorporated in a single model system. The SPH (smooth particle hydrodynamics) technique is employed to model the explosive charge and the close-in zones where large deformation takes place, while the normal FEM is used to model the remaining soil region and the buried structure. Results show that the 2D model can provide reasonably accurate results concerning the crater size, blast loading on the structure, and the critical response in the front wall. The response in the remaining part of the structure shows noticeable differences between the 2D and 3D models. Based on the simulation results, the characteristics of the in-structure shock environment are also discussed in terms of the shock response spectra.     

基于多卫星平台永久散射体雷达干涉提取三维地表形变速度场

永久散射体雷达干涉(PSI)技术及其应用于区域地表形变监测已成为雷达遥感领域的研究热点之一.使用单一卫星平台所获取的单侧视SAR影像时间序列进行PSI分析,仅能获取沿雷达视线(LOS)方向的一维地表位移信息.本文提出了基于多平台永久散射体雷达干涉提取三维地表形变速度场的模型与算法,其基本策略是:首先针对每一卫星平台的SAR影像时间序列进行PSI分析,并计算各地面目标沿LOS向的位移速度值,然后联合各平台所对应的LOS向位移速度值进行建模,并基于最小二乘方法解算各地面目标的三维位移速度分量.实验选取天津市西北部作为测试区,使用2007—2010年所获取的39幅TerraSAR-X影像、23幅ENVISAT ASAR影像和16幅ALOS PALSAR影像进行分析,经联合解算得到了该测试区域的垂直位移速度场以及南北向和东西向水平位移速度分量.与地面水准和已有GPS观测结果对比分析表明:多平台PSI的垂直位移速度场精度可达毫米级,而其水平位移速度分量与已有GPS结果基本一致.多平台PSI分析无需引入任何外部形变参考信息,便可以实现形变场的偏差校准和三维形变场的恢复.     

实验室声发射实验数据服务系统的构建

在岩石变形声发射研究中,为了更好地探究声发射的物理特征,需要不断发展声发射数据的采集和处理技术。地震动力学国家重点实验室的声发射观测系统的记录能力在成倍提升,实验中产生的数据量也大幅增加,这对声发射数据存储、处理和系统地开展岩石变形声发射实验提出了挑战。针对用户的不同需求,文中构建的基于网络的实验室声发射实验数据服务系统不仅实现了数据积累,还实现了数据处理方法的积累和共享。加之与设备无关的声发射数据访问接口的实现,降低了数据访问与处理的门槛,提高了数据的使用率和处理效率。该系统能够满足科研和程序开发用户的需要,能够减少现有工作模式中存在的弊端,可以将其解决方案推广,应用于其它实验数据,提高科研工作效率     

Cost-effective analysis technique for the design of bridges against strike-slip faulting

The paper studies the performance of a typical overpass bridge, with continuous deck and monolithic pier-deck connections, subjected to strike-slip faulting. A three-dimensional (3D) finite element (FE) model of the entire bridge–foundation–abutment–soil system is developed, accounting for soil, structure and geometric nonlinearities. Soil behaviour is simulated with a thoroughly validated strain softening constitutive model. The concrete damaged plasticity (CDP) model is implemented for piers, accounting for the interaction between axial force N , bending moment M , shear force Q and torsion T (NMQT ); the model is validated against experimental results from the literature. The location of the fault rupture is parametrically investigated, confirming the vulnerability of indeterminate structural systems to large tectonic deformation. The deck is shown to sustain both in-plane and out-of-plane bending moments, as well as torsion; the piers are subjected to biaxial bending, shear and torsion. The response is highly dependent on the location of the fault rupture, emphasizing the need to develop cost-effective modelling techniques. Four such techniques are developed (with and without decoupling) and comparatively assessed using the detailed 3D FE model as benchmark. The best prediction is achieved by a coupled model, which includes the bridge superstructure, detailed 3D modelling of the soil-foundation system only for the pier directly affected by the fault, and nonlinear springs representing the foundations of all other piers. The proposed technique offers a computationally efficient means to parametrically analyse long multispan bridges subjected to faulting, for which full 3D FE modelling is impractical.     

固体围压下完整花岗岩粘滑现象的实验研究

本文用完整的花岗岩样品在固体围压三轴实验装置上压缩,研究围压和应变速率对岩样变形破裂过程、粘滑应力降、粘滑复发间隔及样品主破裂几何分布的影响。结果表明,加载速率较低时,粘滑应力降较大,复发间隔较长且分布无规律。加载速率越大,粘滑应力降越小,复发间隔也近似相等,粘滑事件表现出准周期性。围压和应变率较低时,岩石的主破裂会演变成两个交叉的共轭断裂面;而围压和应变率较高时,岩石的主破裂则演变成单一断裂面或入字形断裂面。本文结果对认识中国大陆板内地震孕育、发生及重复过程;研究地震重复发生的机制及影响地震复发间隔的主要因素都有重要意义。     

井孔水位微动态形成机理的探讨

井孔地下水位微动态是地壳附加应力作用下形成的。地壳中产生附加应力的主要因素有地球固体潮、大气压力变动、降雨与地表水体的荷载及断层活动等。井孔水位微动态形成的基本过程是:产生附加应力→含水层变形与孔隙压力变化→含水层—井孔间产生水流运动→井孔水位发生升降。本文从岩土力学与地下水动力学的观点,对于上述过程中的重要环节进行了初步的探讨     

拐折断层黏滑过程的实验研究

采用位移、应变和声发射等测量手段,研究了预置5°拐折断层的房山花岗岩样品的黏滑过程,分析了不同加载速率下5°拐折断层失稳的黏滑特征及相关物理场的演化过程。实验结果表明: 1)5°拐折断层的黏滑周期与加载速率在数值上呈负对数相关关系; 2)在不同的加载速率下,大多数的5°拐折断层失稳是双震事件, 2次子事件的间隔时间大多在100～200ms之间; 3)采用不同的观测手段,即使采样速率一致,其临震响应也存在差异性,如断层失稳前沿断层的应变测量结果呈现明显的应变弱化,断层位移则未见明显的变化; 4)断层黏滑过程中的声发射事件呈现明显的沿断层迁移的特征。认识强震的发生机理和余震特征需要进一步研究断层失稳过程的动力学信息。     

Experimental remolding on the caprock''s 3D strain field of the Indosinian-Yanshanian epoch in Tongling deposit concentrating area

Based on field observations and rheology analysis, we perform one analogue experiment and remold the 3D structural frame of Tongling deposit concentrating area firstly. Then we disassemble and dialyze the 3D structures of the model using the methods of "slicing" and "stripping". A series of sliced planes vertical to the fold hinges show similar landscapes of that in the drill hole profiles. Meanwhile, layer stripping analysis indicates that the deformation features of each layer in the model are qualitatively analogical to those obtained from field observations.Through contrasting the 3D structure between the experimental model and the field phenomena,we verify the following 3D deformation features of the caprock in this area: (1) the Tongling area mainly consists of three series of NE S-typed fold groups; (2) in the uniform stress field, the incoherent folds universally develop in different positions, along different axes as well as in different strata; (3) the faults propagate upward which are mostly inter-bedded detachment faults,while the fold amplitudes decrease while going deeper; and (4) the folds and cleavages are highly developed in the Silurian System indicating that the deformation effect of the Indosinian-Yanshanian structural layer terminates at this layer, which suggests that the Silurian System is the crucial layer for the inversion between brittle and plastic deformation domains and the underlying strata are subject to the control of another deformation system with distinct properties.