2008—2018年河北昌黎海岸输沙势时空变化与沙丘形态演变   总被引：1，自引：1，他引：0  

李志星  李志忠  靳建辉  郑斐  张文静  白利 《中国沙漠》2020,40(3):94-105

输沙势的时空变化特征是研究风积沙丘形态类型及其时空变化规律的重要指标。以中国河北昌黎海岸沙丘分布区为研究对象,利用邻近区域3个气象站记录的2008—2018年风资料分析输沙势时空变化,借助高分辨率的Google卫星影像提取同期横向沙脊和新月形沙丘形态的变化信息,结合区域风速、降水量变化及人类活动等因素,综合分析海岸沙丘分布格局和形态变化的驱动机制。结果表明：（1）研究区输沙势（DP）以春、冬两季最高,潜在风沙作用最活跃;（2）3个气象站中,乐亭站向岸合成输沙方向（RDD）代表研究区主要输沙方向,昌黎站离岸合成输沙方向为次要输沙方向,这两个输沙过程控制了研究区海岸沙丘分布的基本格局;（3）研究区向岸的和离岸的输沙势、合成输沙势（RDP）总体呈现衰减趋势,合成输沙方向没有明显变化;（4）近10年来昌黎海岸沙丘整体呈明显的风蚀消减特征,但气候变化的影响十分有限,而人工植树造林、防风固沙活动导致上风向沙源的减少则是主要原因。  相似文献   

横向磁场中大挠度金属薄板的混沌振动     

薛春霞  张善元  树学锋 《海洋学报》2010,32(9):6599-6605

利用Karman关于板的大挠度理论,考虑涡电流在板中引起的Lorentz力,导出了在横向磁场和横向载荷共同作用下薄板的非线性运动方程.借助Bubnov-Galerkin法将非线性偏微分方程转化为含三次非线性项的常微分方程.在定性分析的基础上,利用次谐轨道的Melnikov函数给出了发生Smale马蹄型混沌运动的阈值条件,进而数值计算了系统的分岔图、相应的相图、Poincaré映射和时程曲线,给出了混沌运动的数字特征.分析结果表明:磁感应强度和外载荷都会影响系统的振动特性.  相似文献   

Evolution of anisotropy with saturation and its implications for the elastoplastic responses of clay rocks     

Sabrina C.Y. Ip  Ronaldo I. Borja 《国际地质力学数值与分析法杂志》2022,46(1):23-46

Many clay rocks have distinct bedding planes. Experimental studies have shown that their mechanical properties evolve with the degree of saturation (DOS), often with higher stiffness and strength after drying. For transversely isotropic rocks, the effects of saturation can differ between the bed-normal (BN) and bed-parallel (BP) directions, which gives rise to saturation-dependent stiffness and strength anisotropy. Accurate prediction of the mechanical behavior of clay rocks under partially saturated conditions requires numerical models that can capture the evolving elastic and plastic anisotropy with DOS. In this study, we present an anisotropy framework for coupled solid deformation-fluid flow in unsaturated elastoplastic media. We incorporate saturation-dependent strength anisotropy into an anisotropic modified Cam-Clay (MCC) model and consider the evolving anisotropy in both the elastic and plastic responses. The model was calibrated using experimental data from triaxial tests to demonstrate its capability in capturing strength anisotropy at various levels of saturation. Through numerical simulations, we demonstrate the role of evolving stiffness and strength anisotropy in the mechanical behavior of clay rocks. Plane strain simulations of triaxial compression tests were also conducted to demonstrate the impacts of material anisotropy and DOS on the mechanical and fluid flow responses.  相似文献