Surface morphology of soil cracks in Yuanmou Dry-hot Valley Region, Southwest China   总被引：3，自引：0，他引：3  

Donghong Xiong  Yi Long  Dongchun Yan  Xiaoning Lu  Zhonghua Ji  Haidong Fang 《山地科学学报》2009,6(4):373-379

Surface morphology of soil cracks is one of the important factors influencing the water evaporation rate in cracked soil in Yuanmou Dry-hot Valley Region, Southwest China. Quantitative study of the complicated surface morphology of soil cracks is a prerequisite for further studies of soil-cracking mechanisms. The present paper establishes a quantitative indicator system by application of concepts and methods originating from Fractal Geometry and Network Analysis. These indicators can effectively express the complicated features of soilcrack network structure. Furthermore, a series of values related to soil-crack morphology was obtained by image processing on field photos of soil-crack quads, and gradation criteria for the degree of development of soil cracks were determined. Finally, the changes in values of the morphological indicators under different degrees of development were analyzed in detail. Our results indicate that （1） the degree of development of soil cracks can be divided into five grades, i.e., feeble development, slight development, medium development, intensive development and extremely intensive development; （2） the values of the indicators change predictably with increasing degree of development of soil cracks. The area density （Dc） increases, and both the area-weighted mean ratio of crack area to perimeter （AWMARP）, which reflects the intensity of cracking, and the index r, which is related to the connectivity of a soil crack, grow uniformly （albeit with different forms）. AWMRAP increases at a geometric rate while r shows logarithmmic growth, indicating a gradual increase in the connectivity of a soil crack. Nevertheless, the areaweighted mean of soil-crack fractal dimension （AWMFRAC） shows a decreasing trend, indicating a gradual decline in the complexity of cracks as area density increases.  相似文献   

华北东部上地幔破裂带   总被引：5，自引：0，他引：5  

杨文采张学民  于常青 《地质学报》2007,81(10):1305-1313

利用天然地震的走时和S波震相的层析成像方法可以提供上地幔S波速度扰动精细图像。我们对华北东部(32°～44°N,114°～126°E)进行了高分辨率S波地震层析成像研究,揭示了苏鲁及环渤海地区上地幔速度结构的差异,为研究该区域深部构造演化提供新的地球物理证据和制约。本次成像取得的最醒目的成果是揭示了由波速剧烈变化指示的两条上地幔破碎带,它们分别出现在渤海湾裂谷区与苏鲁超高压变质带下方。苏鲁超高压变质带下方上地幔破碎带包含多个有序排列的高速团块,推测与扬子走滑并向前俯冲、以及前锋超高压变质块体拆沉及折返作用有关。地幔地震S波速的成像结果支持华北东部渤海湾地区发育地幔热羽柱体系的观点,并对地幔热羽柱的鉴识提供了新的标识。  相似文献   

Study on collapse settlement and cracks of core wall rockfill dams under wetting deformation     

Xiongxiong Zhou  Jichun He  Shichun Chi  Jinwei Wang 《国际地质力学数值与分析法杂志》2023,47(1):106-128

The safety and stability of core wall rockfill dams during impoundment are threatened by the wetting deformation of up-stream shell materials. The serious wetting deformation not only aggravates the collapse settlement of upstream rockfill but also intensifies differential settlement of the dam crest during impoundment, and then causes cracks on the dam crest. On the basis of the proposed wetting deformation model and its simulation method of wetting deformation, this paper simulated the impoundment process of Guanyinyan core wall rockfill dam and studied the deformation characteristic of the dam during impoundment. In addition, the smeared cracking model was used to simulate the crack propagation on the dam crest, and the crack develop and spread mechanism was analysed. The results show that the simulated deformation can fit the in-situ data well, and the simulated crack propagation is in good agreement with the actual situation. Once watered, the upstream rockfill and core wall have significant settlement, and the whole dam crest has obvious horizontal displacement towards the upstream. It is on the same order of magnitude that the increment of horizontal displacement and settlement at the top of the dam during impoundment. In the process of impoundment, the upper part of the dam tends to deform towards the reservoir area, which will lead to tensile cracks appearing in the rockfill areas on both upstream and downstream sides of the core wall of the dam crest, and the propagation direction of the cracks is basically parallel to the adjacent core wall surface. With the water level rising, the cracks on the downstream side of the dam crest mainly extend vertically, and the cracks on the upstream side of the dam crest not only extend vertically, but also extend horizontally.  相似文献   

大规模多岛屿海域潮流场的数值模拟   总被引：6，自引：0，他引：6  

周发毅  郭勇  虞和莹 《海洋工程》1995,(4)

本文提出了一种系统地分析大规模多岛屿海域潮流场的数值模拟方法,以及只有有限代表点位的计算区域内的潮汐和潮流资料的分析方法。建立了适用于复杂的多岛屿海域上平面二维潮波数值计算模型的选择及网格自动剖分方法。通过对长海县长山群岛海域潮流场的模拟,验证了此方法在计算规模大而又要求局部分辨率高的潮流场时,该方法效率高,经济合理,灵活方便。  相似文献   

The Continuum Voronoi Block Model for simulation of fracture process in hard rocks     

Erick Rgenes  Mrcio Muniz de Farias  Leandro Lima Rasmussen 《国际地质力学数值与分析法杂志》2022,46(1):89-112

In this paper, a numerical model is presented to represent the fracture process in hard rocks based on a pseudo-discontinuum method called the Continuum Voronoi Block Model (CVBM). To validate this tool, numerical models for one Brazilian test, one unconfined compression test, and multiple triaxial compression tests with different confining stress were calibrated to match laboratory test results for Creighton granite. The model proved robust and matched the following macro-properties: crack initiation (CI) stress, (CD) stress, peak strength, tensile strength, Young's Modulus, and Poisson's ratio. The calibrated model served as a basis for a sensitivity study to analyze how micro-properties influence the rock's macroscopic responses. From the sensitivity study, a calibration methodology was proposed, which shall facilitate the use of the CVBM in future works.  相似文献   

地震作用下双层土裂缝边坡稳定性分析          下载免费PDF全文

梁承龙  刘芳 《地震工程学报》2022,44(5):1050-1058

裂缝常存在于边坡表面，地震作用会大幅降低裂缝边坡稳定性。针对双层土裂缝边坡稳定性问题，定义上下土层分界处高度与边坡高度之比为深度系数以描述双层土的分布，基于极限分析上限定理，构建“点到点”离散运动学机构，并在此机构中引入一条垂直张拉裂缝，结合拟静力法和强度折减法建立能量平衡方程求解裂缝边坡临界高度和安全系数上限解。计算结果与传统上限法进行对比，验证离散运动学机构的有效性及其解的优越性，同时探究土体非均质性及深度系数对裂缝边坡稳定性以及裂缝深度和位置的影响规律。结果表明，地震作用会降低边坡稳定性；随着地震力增大，边坡临界滑动面逐渐加深，裂缝深度略微增大，裂缝位置逐渐远离坡面；对于具体的双层土边坡会存在一个特定的深度系数使边坡安全系数达到最值，同时裂缝会穿越至下层土且深度发生突增。  相似文献