RB模式下砂土非极限主动土压力的离散元模拟与理论研究     

孙佳政  傅翼  仇雅诗  徐长节  张恒志  冯国辉 《岩土力学》2023,(2):603-614

针对刚性挡土墙绕墙底向外位移(RB)模式下砂土非极限主动土压力分布问题,采用离散元数值模拟对砂土的主动破坏过程进行分析。研究结果表明,非极限主动状态下,不同深度处土体内摩擦角变成极限值时,该点所需的水平位移近似相同,约为0.03%H,墙-土摩擦角至极限值时该点所需的水平位移S_δ近似与深度z呈线性关系,即S_δ=0.12%z;挡墙位移过程中,墙后土体中存在多个相互平行的“准滑动面”。根据模拟结果,在Liu提出的摩擦角调动值计算公式基础上进行了修正,并利用斜微分单元法,取墙后土楔体中平行于滑动面的薄层作为斜微分单元,建立了非极限主动状态下单元体静力平衡方程,得到了RB模式下挡墙不同位移量时非极限主动土压力计算公式。将计算结果与模拟结果和模型试验实测数据进行对比,验证了理论公式的合理性。  相似文献   

多源数据融合实景三维建模关键技术研究          下载免费PDF全文

王峰  滕俊利  王希秀 《山东国土资源》2022,38(1):70-73

本文以某市政府大楼为研究对象,获取车载移动测量及倾斜摄影测量数据,进行了精度分析、多源数据融合,基于融合成果进行实景三维模型重建.通过比对单独基于倾斜摄影的实景三维模型效果,分析了多源数据的融合精度及模型的改善效果.创新性地采用了基于车载移动测量成果的特征矢量要素自动提取技术,结合国产北斗基站数据进行倾斜航摄差分解算,...  相似文献   

利用无人飞艇获取影像资料制作DOM实践——以山东省博兴县城区为例          下载免费PDF全文

谢建春 《山东国土资源》2012,28(7):40-43

利用低空无人驾驶飞艇获取1：1．25万比例尺数字影像资料,制作1：1000比例尺的正射影像,并对正射影像精度进行检查、统计、分析,总结出影响正射影像精度的主要原因,并提出有益于提高正射影像精度的建议。  相似文献   

斜椭圆应力路径下饱和松砂动力特性试验研究     

李男  黄博  凌道盛  汪清静 《岩土力学》2015,36(1):156-162

利用空心圆柱扭剪仪模拟斜入射地震波作用形成的斜椭圆应力路径,对比研究了等向固结条件下饱和福建标准松砂在循环斜椭圆、圆形、扭剪、三轴路径下的动力特性。试验研究表明：土体循环孔压发展存在陡升型和陡降型两种模式;圆形路径下累积孔压增长速率最快,循环扭剪最小;归一化孔压与斜椭圆的倾角无关,但受斜椭圆长短轴比及动应力比影响。砂土的不排水动强度与动应力路径密切相关,循环扭剪和循环三轴最大,循环斜椭圆次之,圆形路径最小。地震波从特定角度入射时,形成近似圆形路径,若只将地震波视为垂直入射的S波,将高估地基土体抗液化强度。  相似文献   

Dalrymple Trough: An active oblique-slip ocean–continent boundary in the northwest Indian Ocean     

R.A. Edwards  T.A. Minshull  E.R. Flueh  C. Kopp 《Earth and Planetary Science Letters》2008,272(1-2):437-445

The Dalrymple Trough marks part of the transform plate boundary between India and Arabia in the northern Arabian Sea. Oblique extension is presently active across this portion of the boundary at a rate of a few millimetres per year, and seismic reflection profiles across the trough confirm that it is an extensional structure. We present new swath bathymetric and wide-angle seismic data from the trough. The bathymetric data show that the trough is bounded by a single, steep, 3-km-high scarp to the southeast and a series of smaller, en-echelon scarps to the northwest. Wide-angle seismic data show that a typical oceanic crustal velocity structure is present to the northwest, with a crustal thickness of ~ 6 km. There is an abrupt change in crustal thickness and velocity structure at the northwestern edge of the trough, and the trough itself is underlain by 12-km-thick crust interpreted as thinned continental crust. Therefore we infer that Dalrymple Trough is an unusual obliquely extending plate boundary at which continental crust and oceanic crust are juxtaposed. The extensional deformation is focused on a single major fault in the continental lithosphere, but distributed over a region ~ 60 km wide in the oceanic lithosphere.  相似文献   

倾斜摄影与近景摄影相结合的山地城市实景三维精细化重建与单体化研究     

连蓉  丁忆  罗鼎  魏文杰  李朋龙  林熙 《测绘通报》2017,(11):128-132

无人机倾斜摄影实景三维模型是一种能够对复杂山地环境较好感知和表达的有效手段之一。本文针对复杂山地城市开展倾斜摄影实景三维存在的问题,提出了适应于山地区域的多尺度的影像获取策略,并通过与近景摄影测量融合建模的方法,实现了对山地城市倾斜摄影实景三维模型精细化建模的目的;同时,对实景三维模型的单体化方法进行了介绍及对比分析,对后期山地城市开展倾斜摄影提供了一定的技术参考。  相似文献   

高速摄影技术在风沙颗粒测速中的应用研究     

蒋缠文  王晓艳  董治宝 《干旱区地理》2017,40(4):746-753

通过相邻图像减法获得了清晰的沙粒运动图像。在此基础上,分别提出了通过人工目视解译与计算机追踪相结合进行跃移颗粒数字轨迹追踪的多帧图像匹配算法以及更适用于计算跃移沙粒群运动瞬时速度场的两帧图像匹配算法。结果表明：与前人研究采用的单纯的人工匹配计算相比,多帧图像匹配算法在保证数据准确性的同时,极大的提高了工作效率。两帧图像匹配算法克服了传统的PTV匹配算法对流场内粒子群运动特征的要求,更加适宜于跃移沙粒群的速度测量,不仅拥有较高的匹配率,而且全过程实现全自动计算,具有较高的计算速度,能够为跃移相整体运动特性研究提供具有代表性的数据。因此,此方法有助于高速摄影技术在研究跃移沙粒运动中的优势更加明显。  相似文献   

The constraints of strain partitioning and geochronology in Luonan-Luanchuan tectonic belts on Qinling orogenic belt   总被引：1，自引：0，他引：1  

SONG ChuanZhong  ZHANG GuoWei  WANG YongSheng  LI JiaHao  CHEN ZeChao & CAI ZhiChuan School of Resources  Environment  Hefei University of Technology  Hefei  China  Department of Geology  Northwest University  Xi’an 《中国科学D辑(英文版)》2009,52(3):300-312

The Luonan-Luanchuan tectonic belt lies between the North China Block and Qinling Mountains, including the Luonan-Luanchuan fault zone and the strong deformation zone to the north of the fault. The ductile shear zone, imbricate brittle fault and duplex structure in the fault zone now are the expression of the same tectonic event in different depth. Such lineation structure exists in the tectonic belts as mineral lineation, elongation lineation, crenulation lineation, sheath folds and so on, indicating NE-directed plate motion. Fold axes and thrusts in the strong deformation zone are inclined to the Luonan-Luanchuan fault zone at small angles. The structures with different natures show a regular pattern, produced during oblique convergence of plates. The convergence factors are as follows: The direction of plate convergence is 22°, 31° and the angle between the plate convergence direction and plate boundary is 73°, 82° respectively in the west and east segment. The Luonan-Luanchuan tectonic belt was deformed strongly in 372 Ma, resulted from Erlangping back-arc ocean basin subduction sinistrally and obliquely to North China Block during the collision of North China Block and South China Block. Supported by National Natural Science Foundation of China (Grant Nos. 40372097 and 40772131)  相似文献   

斜插板挡沙墙设计参数优化数值模拟   总被引：10，自引：2，他引：8  

石龙  蒋富强 《中国沙漠》2014,34(3):666-673

本文基于FLUENT欧拉双流体非定常模型,对不同设计参数的斜插板挡沙墙周围风沙两相流运动特性进行了数值模拟。结果表明：挡沙墙透风率越小,积沙量越大,但沉积的沙堆越靠近挡沙墙,越容易被埋,透风率宜设计为25%～40%;插板倾角小于90°,背风侧沉沙区紧靠挡沙墙,大于90°,背风侧沉沙区与挡沙墙存在一定的距离;插板倾角在90°～135°时,大部分沙粒沉积在挡沙墙周围,防沙效果最佳,结合工程造价,倾角宜取110°～135°;背风侧有效影响范围区内,风速在水平方向与垂直方向风速轮廓线分别呈左“V”形分布与倒“S”形分布;风速一定时,背风侧空气动力有效阴影区范围随挡沙墙高度的增加而逐渐增大;挡沙墙高度一定时,背风侧沉沙区随风速的增大向下风向移动;挡沙墙高度越大,承受的风压越大,工程造价越高,综合考虑工程造价及防沙效果的基础上,挡沙墙高度建议采用1.5～2.0 m。  相似文献   

Photogrammetric monitoring of small streams under a riparian forest canopy   总被引：2，自引：0，他引：2  

Stephen Bird  Dan Hogan  James Schwab 《地球表面变化过程与地形》2010,35(8):952-970

The recent advent of digital photogrammetry has enabled the modeling and monitoring of river beds at relatively high spatial resolution (0·01 to 1 m) through the extraction of digital elevation models (DEMs). The traditional approach to image capture has been to mount a metric camera to an aircraft, although non‐metric cameras have been mounted to a variety of novel aerial platforms to acquire river‐based imagery (e.g. helicopters, radio‐controlled motorized vehicles, tethered blimps and balloons). However, most of these techniques are designed to acquire imagery at flying heights above the riparian tree canopy. In relatively narrow channels (e.g. <20 m bankfull width), streamside trees can obscure the channel and limit continuous photogrammetric data acquisition of both the channel bed and banks, while still providing useful information regarding the riparian canopy and even spot elevations of the channel. This paper presents a technique for the capture and analysis of close‐range photogrammetric data acquired from a vertically mounted non‐metric camera suspended 10 m above the channel bed by a unipod. The camera is positioned under the riparian forest canopy so that the channel bed can be imaged without obstruction. The system is portable and permits relatively rapid image acquisition over rough terrain and in dense forest. The platform was used to generate DEMs with a nominal ground resolution of 0·03 m. DEMs generated from this platform required post‐possessing to either adjust or eliminate erroneous cells introduced by the extraction process, overhanging branches, and by the effects of refraction at the air–water interface for submerged portions of the channel bed. The vertical precision in the post‐processed surface generally ranged from ± 0·01 to 0·1 m depending on the quality of triangulation and the characteristics of the surface being imaged. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献