Effects of hedgerows on sediment erosion in Three Gorges Dam Area, China   总被引：9，自引：2，他引：7  

Chong-Feng BU  Qiang-Guo GAI  Sai-Leung NG  Kwai-Cheong CHAU  Shu-Wen DING 《国际泥沙研究》2008,23(2):119-129

The Three Gorges Dam Area refers to the river section from Chongqing to Yichang on the Yangtze River, which has a drainage area of 75,098 km^2, and involves 19 cities and counties. Contour hedgerows have been used in this area to control soil erosion and to improve hillslope stability in the catchment of this river section. Five experimental hedgerow plots were established in 1994 in order to study the effects of hedgerows on erosion control. During the period of 1994-1997, runoff and soil loss data were collected on these test plots, including the chemical and physical properties of soil and related topographical data. The results indicate that： （1） after 4 years of cultivation and crop planting, soil fertility increased dramatically in the hedgerow plots. Soil organic matter, total nitrogen, and total phosphorus contents in the hedgerow plots were 5-9 times higher than that in the control plot. In each of the hedgerow plots, soil structure became more stable, the quantity of granules larger than 0.02 mm increased and those finer than 0.02 mm decreased; （2） All hedgerow plots showed a major effect on reducing soil loss and surface runoff; （3） Overland flow velocity along the upper portion of the hedgerow plots was greatly reduced due to hedgerow resistance, which explains the significant decrease in soil losses in hedgerow plots, despite the fact that the hedgerow plots and the control plots had the same total runoff.  相似文献   

泄滩滑坡碎块石土饱和与非饱和水力学参数的现场试验研究   总被引：7，自引：1，他引：6  

魏进兵  邓建辉  谭国焕  李焯芬 《岩土力学》2007,28(2):327-330

碎块石土由于块石含量较高,块石粒径较大,其水力学参数的确定具有一定困难。首先,采用双套环法对三峡库区泄滩滑坡的滑体碎块石土饱和渗透系数进行了原位试验,并根据土层孔隙率、颗粒级配等因素采用相关经验公式对试验结果进行了分析。其次,结合使用张力计和体积含水率仪对其土水特征曲线进行了现场模拟试验,并采用Fredlund模型对试验结果进行了拟合分析。最后,根据土水特征曲线和饱和渗透系数,采用经验公式估算了其非饱和渗透系数。试验及分析表明,该滑坡的碎块石土层的饱和渗透系数为(1.78～3.2)×10-2 cm/s,为强渗透性;材料的细颗粒含量越少,有效粒径及控制粒径越大,不均匀系数越小,相应的渗透系数越大。相关研究成果可以为泄滩滑坡非饱和非稳定渗透计算提供参数依据,并对同类型土体非饱和水力学参数的确定具有一定的借鉴意义。  相似文献   

沟道流域坡面与沟谷侵蚀演化关系——以晋西王家沟小流域为例   总被引：9，自引：3，他引：6  

陈浩  Y.Tsui  蔡强国  L.G.Tham  胡文生  Z.Q.Yue  黄建国 《地理研究》2004,23(3):329-338

以往坡、沟侵蚀关系研究主要限于水沙关系的探讨 ,有关原型尺度小流域坡、沟地貌侵蚀演化关系的定量研究甚少 ,尤其是坡、沟地貌特征对流域切割程度的综合影响与交互作用的定量研究尚属空白。本文在 3S技术支持下 ,根据晋西王家沟小流域 196 7年 1∶5 0 0 0正摄影像图 (DOM )、高程数字化模型 (DEM )和同期、同比例尺地形图 ,利用正交多项式回归分析方法 ,定量分析了坡、沟地貌特征对流域切割程度的影响与交互作用。研究表明 ,沟谷地在流域地貌演化及地表切割程度中起主导作用 ,在沟间地面积相同时 ,沟谷地面积约为0 1km2 是影响流域切割裂度侵蚀演化强度最大的区域 ,流域面积愈小影响流域地表破碎的程度最大。其沟道流域坡、沟地貌演化机制可用坡、沟水流动能的地貌指标的综合影响与交互作用来解释  相似文献   

A three-dimensional multi-level turbulence model for tidal motion     

Xiaobo Chao  N. J. Shankar  Cheong Hin Fatt 《Ocean Engineering》1999,26(11):338

A three-dimensional multi-level turbulence model is developed to simulate tide induced circulation in coastal waters. Based on the bathymetry data, the coastal waters are divided into a number of layers. In every layer, the velocities are integrated along the layer depth. The eddy viscosity and diffusivity are computed from the Prandtl mixing length turbulence model. This multi-level model solves for the water surface elevations and currents in different water depths. Comparison of numerical results with the measured data shows good conformity.  相似文献   

A Numerical Study on Wave-Mud Interaction     

张道华  吴朝安 《中国海洋工程》2006,20(3):383-394

1 .Introduction The dynamics of soft mud under surface water waves is of great importance to the sedimentationprocesses in approach channels and harbors ,and has long been drawing attention. Advancements innumerous engineering applications inthe shallowco…  相似文献   

Influence of Heterogeneity of Mechanical Properties on Hydraulic Fracturing in Permeable Rocks   总被引：11，自引：4，他引：7  

T. H. Yang  L. G. Tham  C. A. Tang  Z. Z. Liang  Y. Tsui 《Rock Mechanics and Rock Engineering》2004,37(4):251-275

Summary Numerical simulations of circular holes under internal hydraulic pressure are carried out to investigate the hydraulic fracture initiation, propagation and breakdown behavior in rocks. The hydraulic pressure increases at a constant rate. The heterogeneity of the rocks is taken into account in the study by varying the homogeneity index. In addition, the permeability is varied with the states of stress and fracture. The simulations are conducted by using a finite element code, F-RFPA^2D, which couples the flow, stress and damage analyses. The simulation results suggest that the fracture initiation and propagation, the roughness of the fracture path and the breakdown pressure are influenced considerably by the heterogeneity of rocks. The hole diameter elongation and the stress field evolution around the fracture tip during the fracture propagation can also provide useful information for the interpretation of the hydraulic fracturing behaviour.  相似文献   

The 1786 earthquake-triggered landslide dam and subsequent dam-break flood on the Dadu River, southwestern China   总被引：17，自引：1，他引：17  

F.C. Dai  C.F. Lee  J.H. Deng  L.G. Tham 《Geomorphology》2005,65(3-4):205-221

Chinese historic documents recorded that on June 1, 1786, a strong M=7.75 earthquake occurred in the Kangding-Luding area, Sichuan, southwestern China, resulting in a large landslide that fell into the Dadu River. As a result, a landslide dam blocked the river. Ten days later, the sudden breaching of the dam resulted in catastrophic downstream flooding. Historic records document over 100,000 deaths by the flood. This may be the most disastrous event ever caused by landslide dam failures in the world. Although a lot of work has been carried out to determine the location, magnitude and intensity of the 1786 earthquake, relatively little is known about the occurrence and nature of the landslide dam. In this paper, the dam was reconstructed using historic documents and geomorphic evidence. It was found that the landslide dam was about 70 m high, and it created a lake with a water volume of about 50×10⁶ m³ and an area of about 1.7 km². The landslide dam breached suddenly due to a major aftershock on June 10, 1786. The peak discharge at the dam breach was estimated using regression equations and a physically based predictive equation. The possibility of a future failure of the landslide seems high, particularly due to inherent seismic risk, and detailed geotechnical investigations are strongly recommended for evaluating the current stability of the landslide.  相似文献   

现场室内两用大型直剪仪研制(I)：结构设计   总被引：9，自引：2，他引：9  

闵弘  刘小丽  魏进兵  邓建辉  谭国焕  李焯芬 《岩土力学》2006,27(1):168-172

直剪仪是测定岩土体抗剪强度参数应用最为普遍的一种试验仪器。从直剪仪的结构和大型直剪仪的研制两个方面对直剪仪的研究现状做了介绍，在此基础上，对新近研制的现场室内两用大型直剪仪的结构组成、工作机理及其特点进行了详细分析。该大型直剪仪与常规直剪仪相比，具有较大的优越性，其测试结果更加准确。适用范围广，测试精度高，可应用于现场和室内试验。  相似文献   

孔隙水压力对岩石裂纹扩展影响的数值模拟   总被引：1，自引：0，他引：1  

唐春安  杨天鸿  李连崇  梁正召  ThamL.G.  LeeK.K.  TsuiY. 《岩土力学》2003,(Z2)

应用岩石破坏过程渗流-应力-损伤(FSD)耦合分析软件F-RFPA2D,通过对孔隙水压作用下岩石试件加载破坏过程的数值模拟,对孔隙水压力大小和梯度对岩石试样中裂纹的萌生和扩展进行了数值模拟研究。模拟结果再现了孔隙水压力作用下裂纹萌生扩展的全过程,表明孔隙水压力大小和梯度对岩石中裂纹的萌生和扩展模式都有很大的影响。  相似文献   

香港花岗岩地貌地质旅游的开发          下载免费PDF全文

吴振扬 《地质论评》2007,53(B08):104-110

地质旅游利用现有的地质资源，以一种崭新的角度去发展可持续性的旅游景点。香港地少人多，发展旅游吸引点是极度困难的。香港陆地约有30％为花岗岩覆盖，其中的一半已在城市之下，其余的则拥有相当吸引人的地质景象，有极大潜力发展地质旅游。除吸引地质生态有关游客外，在花岗岩地区开发地质旅游，更容易普及地球科学，同时增强公众对地质地貌之欣赏能力，提高环保及地质保护意识。不过，于香港花岗岩区发展地质旅游所遇到的困难亦不少，主要来自规划、行政及安全的问题，当中需要政府、地区民众及地质旅游工作者并肩合作，寻求最佳解决方法。  相似文献