Kinetic energy–rainfall intensity relationship for Central Cebu, Philippines for soil erosion studies     

Ricardo L. Fornis  Hans R. Vermeulen  Jan D. Nieuwenhuis 《Journal of Hydrology》2005,300(1-4):20-32

In the study of soil erosion, specifically on detachment of soil particles by raindrop impact, kinetic energy is a commonly suggested indicator of the raindrop's ability to detach soil particles from the soil mass. Since direct measurement of kinetic energy requires sophisticated and costly instruments, the alternative approach is to estimate it from rainfall intensity. The present study aims at establishing a relationship between rainfall intensity and kinetic energy for rainfalls in Central Cebu, Philippines as a preface of a wider regional investigation.

Drop size distributions of rainfalls were measured using the disdrometer RD-80. There are two forms of kinetic energy considered here. One is kinetic energy per unit area per unit time (KE_R, J m⁻² h⁻¹) and the other is kinetic energy per unit area per unit depth (KE, J m⁻² mm⁻¹). Relationships between kinetic energy per unit area per unit time (KE_R) and rainfall intensity (I) were obtained using linear and power relations. The exponential model and the logarithmic model were fitted to the KE–I data to obtain corresponding relationships between kinetic energy per unit area per unit depth of rainfall (KE) and rainfall intensity (I). The equation obtained from the exponential model produced smaller standard error of estimates than the logarithmic model.  相似文献   

Macroseismic Intensity Modelling of Earthquakes in Southern Spain: Attenuation and Tectonic Implications     

Tiziana Tuvè  Antonio Teramo  Jesus Ibañez  Carla Bottari  Domenica Termini 《Pure and Applied Geophysics》2005,162(4):747-760

A modelling of the observed macroseismic intensity of historical and instrumental earthquakes in southern Spain is proposed, with the aim of determining the macroseismic parameters for seismic hazard evaluation in a region in which the characterization of intensity distribution of seismic events shows different levels of difficulty referable to the complex faults system of the area in study. The adopted procedure allows an analytical determination of epicenters and principal attenuation directions of earthquakes with a double level of verification with reference to the maximum shaking area and structural lineaments of the region, respectively. The analyses, carried out on a suitable number of events, highlight, therefore, some elements for a preliminary characterization of a seismic zonation on the basis of the consistency between seismic intensity distribution of earthquakes and corresponding structural framework.  相似文献   

Developing efficient scalar and vector intensity measures for IDA capacity estimation by incorporating elastic spectral shape information     

Dimitrios Vamvatsikos  C. Allin Cornell 《地震工程与结构动力学》2005,34(13):1573-1600

Scalar and vector intensity measures are developed for the efficient estimation of limit‐state capacities through incremental dynamic analysis (IDA) by exploiting the elastic spectral shape of individual records. IDA is a powerful analysis method that involves subjecting a structural model to several ground motion records, each scaled to multiple levels of intensity (measured by the intensity measure or IM), thus producing curves of structural response parameterized by the IM on top of which limit‐states can be defined and corresponding capacities can be calculated. When traditional IMs are used, such as the peak ground acceleration or the first‐mode spectral acceleration, the IM‐values of the capacities can display large record‐to‐record variability, forcing the use of many records to achieve reliable results. By using single optimal spectral values as well as vectors and scalar combinations of them on three multistorey buildings significant dispersion reductions are realized. Furthermore, IDA is extended to vector IMs, resulting in intricate fractile IDA surfaces. The results reveal the most influential spectral regions/periods for each limit‐state and building, illustrating the evolution of such periods as the seismic intensity and the structural response increase towards global collapse. The ordinates of the elastic spectrum and the spectral shape of each individual record are found to significantly influence the seismic performance and they are shown to provide promising candidates for highly efficient IMs. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

华蓥山隧道岩溶发育强度垂直分带     

熊道锟  傅荣华 《岩土工程技术》2005,19(4):186-190

论述了华蓥山隧道的岩溶发育特征,根据岩溶发育强度的划分依据和划分标准,结合岩溶发育的历史,采用类比判别法、主因素判别法和综合判别法对岩溶发育强度作了垂直分带,据此预测的溶洞规模与实际情况吻合。  相似文献   

Fracture mechanics analysis of multiple cracks in anisotropic media     

Chia‐Huei Tu  C.‐S. Chen  T.‐T. Yu 《国际地质力学数值与分析法杂志》2011,35(11):1226-1242

This paper presents a single‐domain boundary element method (BEM) for linear elastic fracture mechanics analysis in the two‐dimensional anisotropic material. In this formulation, the displacement integral equation is collocated on the un‐cracked boundary only, and the traction integral equation is collocated on one side of the crack surface only. A special crack‐tip element was introduced to capture exactly the crack‐tip behavior. A computer program with the FORTRAN language has been developed to effectively calculate the stress intensity factors of an anisotropic material. This BEM program has been verified having a good accuracy with the previous researches. Furthermore, by analyzing the different anisotropic degree cracks in a finite plate, we found that the stress intensity factors of crack tips had apparent influence by the geometry forms of cracks and media with different anisotropic degrees. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Hydrologic response of engineered media in living roofs and bioretention to large rainfalls: experiments and modeling          下载免费PDF全文

Ruifen Liu  Elizabeth Fassman‐Beck 《水文研究》2017,31(3):556-572

The hydrologic response of engineered media plays an important role in determining a stormwater control measure's ability to reduce runoff volume, flow rate, timing, and pollutant loads. Five engineered media, typical of living roof and bioretention stormwater control measures, were investigated in laboratory column experiments for their hydrologic responses to steady, large inflow rates. The inflow, medium water content response, and outflow were all measured. The water flow mechanism (uniform flow vs. preferential flow) was investigated by analyzing medium water content response in terms of timing, magnitude, and sequence with depth. Modeling the hydrologic process was conducted in the HYDRUS‐1D software, applying the Richards equation for uniform flow modeling, and a mobile–immobile model for preferential flow modeling. Uniform flow existed in most cases, including all initially dry living roof media with bimodal pore size distributions and one bioretention medium with unimodal pore size distribution. The Richards equation can predict the outflow hydrograph reasonably well for uniform flow conditions when medium hydraulic properties are adequately represented by appropriate functions. Preferential flow was found in two media with bimodal pore size distributions. The occurrence of preferential flow is more likely due to the interaction between the bimodal pore structure and the initial water content rather than the large inflow rate.  相似文献   

Revised runoff curve number for runoff prediction in the Loess Plateau of China     

Wenhai Shi  Ni Wang  Miaomiao Wang  Donghao Li 《水文研究》2021,35(10):e14390

The soil conservation service (now Natural Resources Conservation Service) Curve Number (SCS-CN), one of the most commonly used methods for surface runoff prediction. The runoff calculated by this method was very sensitive to CN values. In this study, CN values were calculated by both arithmetic mean (CN_C) and least square fit method (CN_F) using observed rainfall-runoff data from 43 sites in the Loess Plateau region, which are considerably different from the CN₂ values obtained from the USDA-SCS handbook table (CN_T). The results showed that using CN_C instead of CN_T for each watershed produce little improvement, while replacing CN_T with CN_F improves the performance of the original SCS-CN method, but still performs poorly in most study sites. This is mainly due to the SCS-CN method using a constant CN value and discounting of the temporal variation in rainfall-runoff process. Therefore, three factors—soil moisture, rainfall depth and intensity—affecting the surface runoff variability are considered to reflect the variation of CN in each watershed, and a new CN value was developed. The reliability of the proposed method was tested with data from 38 watersheds, and then applied to the remaining five typical watersheds using the optimized parameters. The results indicated that the proposed method, which boosted the model efficiencies to 81.83% and 74.23% during calibration and validation cases, respectively, performed better than the original SCS-CN and the Shi and Wang (2020b) method, a modified SCS-CN method based on tabulated CN value. Thus, the proposed method incorporating the influence of the temporal variability of soil moisture, rainfall depth, and intensity factors suggests an accurate runoff prediction for general applications under different hydrological and climatic conditions on the Loess Plateau region.  相似文献   

移动测量系统宽幅影像的几何拼接与量测     

乌萌  张晓东  段渭超 《测绘科学技术学报》2016,(4):415-420

研究了移动测量系统宽幅影像的拼接与量测算法。通过建立三幅影像柱面全景投影的几何关系,能够直接拼接完成宽幅影像。利用宽幅影像和原始影像间反投影变换关系以及三幅原始影像的同、异步立体像对,可建立宽幅影像与物方空间坐标间一一对应关系,从而实现宽幅影像目标的量测算法。宽幅影像的投影拼接和量测实验表明,利用柱面全景投影拼接得到宽幅影像的方法可应用于移动测量平台宽幅影像序列的拼接;在原始影像具备同步立体像对的条件下,宽幅影像量测的绝对精度可达1 m以内,相对精度可达0.2 m以内,满足城市环境实景目标量测的精度需求。  相似文献   

分数阶混合随机泛函微分方程的能控性     

杨加顺  胡军浩 《南京气象学院学报》2016,8(2):186-192

主要研究了分数阶混合随机泛函微分方程的能控性.在无限维空间下,假设所考虑方程线性部分生成半群不是紧的,使用非紧性测度技术和Mönch不动点定理,给出了方程能控性充分条件,并通过一个例子说明了结论的有效性.  相似文献   

强台风海鸥登陆期间近地层风特性分析   总被引：2，自引：2，他引：0  

赵小平  朱晶晶  樊晶  贵志成 《气象》2016,42(4):415-423

利用位于海南文昌市的90 m测风塔观测的强台风海鸥多层测风数据,分析了台风海鸥登陆期间近地层风场时空特征、湍流强度、垂直风切变及阵风因子等风场特性,分析结果表明:台风海鸥登陆期间,近地层各高度风速呈现"M"型双峰特征,最大风速出现在台风后风圈;台风过境前后,风向旋转了180°;近地层风速随高度升高而增大,各高度风速垂直切变符合对数和指数规律;粗糙度长度、风廓线幂指数、湍流强度、阵风系数等风场特性与风速呈负相关关系,随着风速的增加而降低;从台风外围至台风眼,粗糙度长度随风速呈现"增大-减小-增大"特征;台风眼内部风速垂直切变剧烈,前后风圈的风速垂直切变较弱;强风区湍流强度较弱,弱风区湍流强度较强;台风风圈的湍流强度随高度增加而减小,台风眼内湍流强度随高度先减小再增加;台风影响各阶段阵风系数随高度升高而减小,各高度层阵风系数遵循指数定律;阵风系数随风速的增大而减小,当风速达到一定强度时,阵风系数随风速变化不明显。  相似文献