青藏高原递进式隆升的力学模式   总被引：8，自引：6，他引：2  

马润勇  席先武  彭建兵  赵法锁  李喜安 《大地构造与成矿学》2005,29(4):451-458

根据青藏高原现代构造变形的GPS速度场、高原区喜马拉雅山等五大山脉之间的几何关系,及其在地貌构造上的褶皱结构特点、岩石圈的分层特征,提出在印度板块的推挤作用下,青藏高原具有递进式隆升特征的观点。在此基础上,建立了地壳层递进式弯曲隆升的力学模型,并利用FLAC有限差分法数值模拟软件,近似采用平面应变条件,模拟了在水平推力作用下,地壳层递进式挤压弯曲隆升的过程。根据所建立的力学模型和数值模拟结果认为,青藏高原隆升的主要动力源是印度板块北北东方向的推挤力,地壳层依照自南而北的次序逐步产生一系列弯曲隆起,从平面、剖面上均具有密切的时序因果关系;高原隆升与活动构造的发育、分布具有密切关系,断裂活动强度自南向北递进式扩展。  相似文献   

一种面向大场景3维显示的地形建模方法   总被引：10，自引：0，他引：10  

涂震飚  刘永才  苏康  田金文 《测绘学报》2004,33(1):71-76

提出一种面向大范围3维场景显示的地形建模方法.该方法基于数字高程模型DEM(Digital Elevation Model)固有的栅格特点,将大范围场景划分成小的子块.根据应用对这些子块的精度要求,采用不同地形建模方法构建相应的细节层次LoD( Level of Detail)模型.最终,通过拼接这些子块模型完成对整个大场景的多分辨率建模,试验结果表明,该算法具有较好的实用性和有效性.  相似文献   

Atypical size selection of captive school prawns,Metapenaeus macleayi,by three recreational fishing gears in south‐eastern Australia     

Matt K. Broadhurst  Russell B. Millar  Damian J. Young  Michael E. L. Wooden  Stuart Rowland 《新西兰海洋与淡水研究杂志》2013,47(5):755-766

Three manipulative experiments were done to estimate the selectivity of conventional and new sizes and configurations of mesh for school prawns, Metapenaeus macleayi, in three south‐eastern Australian recreational fishing gears (haul, push, and scoop nets). The treatment meshes examined were: (1) conventional‐sized, diamond‐shaped mesh used in all gears (20 mm in scoop nets and 30 mm in push and haul nets); (2) 30 mm in scoop nets; and (3) 40‐mm diamond‐ and (4) 23‐mm square‐shaped mesh in all gears. In all experiments, known quantities of school prawns (6–24 mm carapace length (CL)) were placed in purpose‐built enclosures, monitored to ensure no experimental‐induced stress (as measured by changes in L‐lactate in their haemolymph) and the replicate treatments of the various gear configurations deployed. Escapees from the various treatment nets were collected from the enclosures using fine‐meshed nets. Logistic selection curves were derived for all treatment nets and specific comparisons made within and among gears. All nets had 50% retention lengths (L₅₀) comparable to other penaeid‐catching gears with similar mesh sizes, but most had selection ranges (SRs) that were atypically inflated. The large SRs were attributed to a combination of factors that included the mesh geometry and towing speed of the gears and the behaviour of school prawns. The 20‐mm scoop net had the smallest selection parameters, retaining >99% of individuals larger than 13 mm CL. Mesh size in this gear would need to be increased to at least 30 mm to allow some maturing prawns (>18 mm CL) to escape.  相似文献   

Progressive failure of sheeted rock slopes: the 2009–2010 Rhombus Wall rock falls in Yosemite Valley,California, USA     

Greg M. Stock  Stephen J. Martel  Brian D. Collins  Edwin L. Harp 《地球表面变化过程与地形》2012,37(5):546-561

Progressive rock‐fall failures in natural rock slopes are common in many environments, but often elude detailed quantitative documentation and analysis. Here we present high‐resolution photography, video, and laser scanning data that document spatial and temporal patterns of a 15‐month‐long sequence of at least 14 rock falls from the Rhombus Wall, a sheeted granitic cliff in Yosemite Valley, California. The rock‐fall sequence began on 26 August 2009 with a small failure at the tip of an overhanging rock slab. Several hours later, a series of five rock falls totaling 736 m³ progressed upward along a sheeting joint behind the overhanging slab. Over the next 3 weeks, audible cracking occurred on the Rhombus Wall, suggesting crack propagation, while visual monitoring revealed opening of a sheeting joint adjacent to the previous failure surface. On 14 September 2009 a 110 m³ slab detached along this sheeting joint. Additional rock falls between 30 August and 20 November 2010, totaling 187 m³, radiated outward from the initial failure area along cliff (sub)parallel sheeting joints. We suggest that these progressive failures might have been related to stress redistributions accompanying propagation of sheeting joints behind the cliff face. Mechanical analyses indicate that tensile stresses should occur perpendicular to the cliff face and open sheeting joints, and that sheeting joints should propagate parallel to a cliff face from areas of stress concentrations. The analyses also account for how sheeting joints can propagate to lengths many times greater than their depths behind cliff faces. We posit that as a region of failure spreads across a cliff face, stress concentrations along its margin will spread with it, promoting further crack propagation and rock falls. Published in 2012. This article is a US Government work and is in the public domain in the USA.  相似文献   

波浪作用下粉土海床中的孔压响应试验研究     

李安龙  李广雪  林霖  许国辉 《海洋通报》2012,31(1):15-20

海床在波浪作用下是否稳定对海底工程的安全至关重要,海床的稳定性与土体中的孔压响应密切相关。水槽模拟试验表明:在波浪的作用下,黄河三角洲粉土海床中将产生振荡孔隙水压力和累积孔隙水压力。振荡孔隙水压力大小与土层深度、波高和粘粒含量有关,其振幅(能量)在土层中随深度的增加呈指数衰减,且粘粒含量越高衰减越快;加载波高越大,能量衰减越快。而累积孔压响应模式表现为在波浪作用最初的一段时间内,孔隙水压力快速上升,然后逐渐减小而趋于稳定,其大小和速率也与波高、粘粒含量、土层埋深有关,粘粒含量越高,孔压累积速度越低。  相似文献   

基于边坡渐进破坏特征对传统极限平衡法几点假设的合理分析     

曾锃  张泽辉  杨宏丽  尹小涛  党发宁 《岩土力学》2012,33(Z1):146-150

边坡的渐进破坏特征一直以来是边坡计算仿真中的一个难点。实际边坡的破坏很少是一个整体达到极限状态,突然滑动的过程,往往是逐步发展由局部破坏到最终整体失稳,即临界状态小扰动导致的链式多米洛骨牌式失稳。利用颗粒流软件,设计了0.1 m粒径高10 m土坡的数值模型,粒间黏聚力为36 kPa,摩擦系数为0.36。初始模型在重力作用下不会发生破坏,通过单独折减粒间黏聚力到18 kPa使得边坡破坏,监测竖向颗粒组group的变化获取每20 000个时间步的边坡破坏形态,实现200 000个时间步内边坡的渐进破坏过程。边坡总是从局部开始破坏,坡体物质的运移造成次一级破坏,形成最终的近似弧形的滑动面,说明滑体不是整体下滑,不是刚体,不是整体达到极限状态;坡体内应力的变化也不是单调的,有涨有落,均区别于当前极限平衡法中有限条块的刚体假设;滑动面上同时达到极限状态假设,问题本身是静不定的,通过给出条间力的传递方式使之静定可解;整体分析不能考虑破坏的局部化和渐进特征。这说明边坡计算方法的未来在于能反映动力问题和材料破坏特征的离散元方法。  相似文献   

渗流影响下岩石损伤和渐进破裂演化过程的数值试验研究   总被引：1，自引：1，他引：0       下载免费PDF全文

付金伟  朱维申  张敦福  贾超 《水文地质工程地质》2015,42(1):53-59

在FLAC-3D软件平台上,开发出岩石破裂过程的渗流-损伤耦合分析程序,对渗流-损伤耦合作用下岩石的裂纹萌生、扩展过程进行模拟研究。分析了在孔隙水压力作用下,含原生裂隙和弱化单元的非均质试件在单轴、三轴加载下的破坏过程,并与非渗流条件下试件在单轴、三轴压缩下的破坏过程相对比,通过动态显示损伤状态、渗流场,并分析应力应变关系、位移图等,对渗流影响下裂隙岩体的损伤和渐进破裂过程进行了研究。  相似文献   

基于GIS的二维非结构化剖分网格优化   总被引：2，自引：1，他引：1  

赵晓东  王海龙  沈永明 《地理与地理信息科学》2010,26(2)

非结构化网格剖分是数值模拟的关键技术之一,网格质量直接影响到计算的收敛性和精确度。在GIS辅助建立非结构化网格空间拓扑关系的基础上,针对GIS和实际研究问题给出Spring-Laplace方法——一种新的单元尺度函数定义,在GIS空间算法下利用该方法优化节点位置,并基于推进阵面算法的思想,结合空间邻近拓扑关系实现了三角剖分节点和网格的重新编号算法,方便了开边界条件的赋值,提高了计算效率。实例表明,该方法大大提高了网格生成质量,能适应FVCOM数值模型对非结构化网格剖分的要求,其收敛速度快,具有较高的运算效率。  相似文献   

城市供水管网健康监测与诊断(Ⅰ)——用户流量的预测     

梁建文 《地震工程与工程振动》2010,30(4)

供水管网运行状态的准确把握对供水管网的健康监测和健康诊断至关重要,而供水管网运行状态准确把握的关键则在于对用户流量的准确把握。本文提出了供水管网用户流量预测的两个方法,EMD分解与自回归模型相结合的方法和逐步回归方法与自回归模型相结合的方法,文中通过一实际供水管网中某用户流量的预测分析并与实际监测值的比较,验证了两个方法的有效性。研究使得城市供水管网健康的在线监测和在线诊断成为可能。  相似文献   

组合式面板双绞合六边形钢丝网加筋土挡墙现场试验研究     

刘泽  黄向京  杨果林 《岩土力学》2011,32(11):3295-3300

为研究双绞合六边形钢丝网加筋土挡墙的受力、变形特性,对潭衡（湘潭－衡阳）西线高速公路K124+340断面组合式面板双绞合六边形钢丝网加筋土挡墙进行了现场试验,测试了竖向土压力、水平土压力、筋材拉应变分布规律和格宾箱变形规律。结果表明：在筋材长度方向上,竖向土压力在挡墙下部呈双峰型分布,而在上部呈单峰形分布;墙背水平土压力沿墙高呈非线性分布,最大值发生在墙高约1.5 m处,实测水平土压力小于主动压力;筋材应变在筋长方向上呈非线性分布,各层筋材的应变分布模式不相同;筋材的变形主要发生在施工期,格宾箱的变形呈鼓胀式  相似文献