Numerical modeling of gravitational erosion in rill systems

A self-organizing model was developed for simulating rill erosion process on slopes with particular attention to the role of gravitational erosion.For a complete simulation circle,processes such as precipitation,infiltration,runoff,scouring,gravitational erosion and elevation variation were fully considered.Precipitation time(or runoff time) was regarded as iteration benchmark in the model.To specify the contribution of gravitational erosion to the process of rill formation and development,a gravitational erosion module was inserted into the model.Gravitational erosion in rill development was regarded as a Gaussian random process.A model was calibrated by our experimental data,and further validated satisfactorily with 22 runs of experimental results from different investigators. Systematic comparison was made between sediment yields with and without consideration of gravitational erosion module.It was demonstrated that the model could reasonably simulate the rill erosion process under a variety of slope gradients,rainfall intensities and soil conditions upon the gravitational erosion being considered.However,the role of gravitational erosion on sediment yields in rill systems varies significantly under different conditions,although it is of the utmost importance in steeper slopes.The process of gravitational erosion in rill development was studied by a newly-defined parameter a>,which is defined as the volume ratio of gravitational erosion over hydraulic-related erosion.The gravitational contribution to the total erosion could be over 50%for the rill systems with higher rainfall intensity and steeper slopes.     

天津地区上地壳构造及沧东断裂折射地震走时成像

采用初至波成像方法,对天津地区上地壳进行成像,获得了塘沽-武清地区上地壳P波速度精细结构,成像结果反映了沧县隆起两侧凹陷盆地不断拉张下沉的特征.基于Colin Zelt 提出的初至波成像方法,给出了一种判断隐伏断裂的成像方法,数值模拟和对沧东断裂的成像结果显示出该方法的有效性,同时也对沧东断裂进行了空间判断和分析.     

安徽地区尾波Qc值特征研究

基于Sato单次散射模型,利用安徽省数字化测震台网2001年以来记录到的ML≥2.3级地震的波形资料,计算得到了安徽地区不同台站周围地壳介质的尾波Qc值,发现省内不同地区尾波Qc值存在着明显的差异,霍山地区尾波Qc值相对省内其余地区较低,拟合得到了安徽地区尾波Qc值与频率之间的依赖关系,为Qc=(104.9±36.4)...     

张家界砂岩地貌形成时代:来自阶地与溶洞对比的证据

张家界以其独特罕见的石英砂岩峰林地貌闻名于世,一直是地貌学家、地质学家们关注的焦点,但关于其形成年代问题尚显薄弱,一直缺乏系统深入的研究.本文对索溪流域不同层状地貌进行了地貌学、沉积学和年代学综合研究.研究结果表明,索溪河谷普遍发育三级阶地,T;很少发育,主要表现为河流两侧化置较高的古宽谷或剥蚀面.岩溶洞穴黄龙洞从上往...     

不同大地坐标系间相互转换的病态解决及抗差算法

不同大地坐标系间进行坐标转换是利用具有两个坐标系下坐标的公共点,求取转换参数 经常会遇到系数矩阵病态导致转换精度差的问题,且公共点的坐标精度直接影响转换参数的求解精度,也就是影响坐标转换的精度.本文探讨利用LC曲线法、截断奇异值法及广义交叉检验准则法解决病态问题,同时采用抗差估计理论进行不同大地坐标间的转换.当公共点...     

高速铁路CPⅢ高程控制网测量方法研究

本文分析高速铁路CPⅢ高程控制网建网时普遍采用的德国测量方法,指出其存在的不足,在此基础上提出了技术上更为合理又适合我国国情的矩形法测量方法。通过对矩形法相邻点高差相对中误差和最弱点高程中误差的估算以及实验验证,认为矩形法可以用于CPⅢ高程网的建网测量。研究结果对于目前高速铁路工程测量相关规范的制订和在建高速铁路CPⅢ高程网的测量具有重要的参照价值。     

影响热带气旋路径的敏感性试验与研究

针对热带气旋观测中的敏感区域问题,用数值模拟的方法,以GRAPES-TCM为试验模式,对登陆中国的2个热带气旋“派比安”与“圣帕”进行了敏感性试验,并通过模拟其他4个热带气旋路径对试验结果进行了验证.结果显示,初始场的不确定性导致了热带气旋路径的不确定性,但初始场中涡旋场的变化对路径几乎没有影响,环境场中位于涡旋外、距...     

Water Cycle and Microphysical Processes Associated with a Mesoscale Convective Vortex System in the Dabie Mountain Area

The water vapor budget and the cloud microphysical processes associated with a heavy rainfall system in the Dabie Mountain area in June 2008 were analyzed using mesoscale reanalysis data(grid resolution 0.03 × 0.03,22 vertical layers,1-h intervals),generated by amalgamating the local analysis and prediction system(LAPS).The contribution of each term in the water vapor budget formula to precipitation was evaluated.The characteristics of water vapor budget and water substances in various phase states were evaluated and their differences in heavy and weak rainfall areas were compared.The precipitation calculated from the total water vapor budget accounted for 77% of actual precipitation;surface evaporation is another important source of water vapor.Water vapor within the domain of interest mainly came from the lower level along the southern boundary and the lower-middle level along the western boundary.This altitude difference for water vapor flux was caused by different weather systems.The decrease of local water vapor in the middle-lower layer in the troposphere during the system development stage also contributed to precipitation.The strength and the layer thickness of water vapor convergence and the content of various water substances in the heavy rainfall areas were obviously larger than in the weak rainfall areas.The peak values of lower-level water vapor convergence,local water vapor income,and the concentration of cloud ice all preceded the heaviest surface rainfall by a few hours.     

汶川震区文家沟泥石流成灾机理与特征

文家沟位于绵竹市清平乡,属于5·12汶川Ms8.0级地震极重灾区.地震发生后的3个汛期内,文家沟曾先后发生5次典型泥石流灾害,其中以2010年8月13日泥石流灾害最为严重,规模与灾情巨大,社会影响深远.在对文家沟泥石流跟踪调查的基础上,探讨了泥石流的成灾机理和特征.研究表明:(1)文家沟泥石流是地震和强降雨共同作用的结...     

绿化屋顶的产流规律及雨水滞蓄效果模拟研究

建筑物屋顶作为城市的"第五面",是城市立体化绿化的重要方面。通过屋顶绿化植被和土壤层的蓄滞作用,可在一定程度上延缓产流时间,减少城市径流,并改善局地微气候条件。开展了绿化屋顶的人工降雨径流观测实验,通过对降雨、径流的观测分析了绿化屋顶的雨水滞蓄效果。建立了描述绿化屋顶降雨产流过程的一维入渗模型HYDRUS-1D,利用实验数据进行了模型的率定和验证;并应用模型模拟分析了降雨频率、土层厚度和土壤类型等因素对绿化屋顶雨水滞蓄效果的影响。实验和模拟结果表明,绿化屋顶具有较好的雨水滞蓄效果,10cm土层厚度的绿化屋顶在不同降雨条件下的蓄滞量可达到16.1～21.6mm;随着土层厚度的增加,蓄滞效果更明显;就雨水蓄滞效果而言,壤土比砂土和粉粘土更适合于绿化屋顶。本研究成果可为城市屋顶绿化的推广应用提供参考。