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131.
良好植被区泥石流防治初探 总被引:10,自引:0,他引:10
通过对近年来发生在良好植被区的几次重大泥石流、滑坡灾害的考察,发现植被在泥石流、滑坡形成中的作用有待于进一步认识。通过分析,当中小强度降雨激发下,植被能够削减泥石流、滑坡灾害的规模,甚至抑制泥石流、滑坡灾害的发生;当降雨超过一定阀值后,在水作用下,植被不但不能削减灾害规模,反而增大灾害的规模。在这类地区,简单地使用一般的防治措施,已经不能满足防灾、减灾的需要,客观要求针对这些地区泥石流灾害的形成原因、危害特征,研究防治对策。经初步研究提出3点防治措施:1)加强泥石流滑坡灾害的预测预报工作;2)在重点区域设置自动雨量记录报警装置;3)特别针对漂木拦挡,采取新型结构减轻泥石流的危害。 相似文献
132.
山地灾害研究的发展态势与任务 总被引:3,自引:0,他引:3
泥石流、滑坡等山地灾害已成为世界各国十分关注的自然灾害问题。据最近几年的国际学术会议,泥石流、滑坡研究的前沿领域是:泥石流、滑坡活动的地带性与全球气候变化的规律;泥石流、滑坡起动机理、动力学模型;泥石流、滑坡等山地灾害风险分析、发生时间预报;成灾机理与减灾防灾关键技术。国内研究较晚,但发展很快。经过近50 a的研究,涉及上述诸多研究颁域。但研究不深,还存在不少差距。据国内外研究态势,针对山地所实际,提出了在泥石流、滑坡理论创新和防治关键技术等研究方面12条任务。 相似文献
133.
G. Colangelo V. Lapenna A. Perrone S. Piscitelli L. Telesca 《Engineering Geology》2006,88(3-4):274-286
A geoelectrical monitoring activity has been carried out to improve the geological and hydrogeological knowledge about the Varco d'Izzo landslide (Potenza, Basilicata, Southern Apennine, Italy), an active rotational–translational slide evolved in earth-flow. In this work we have focused on the Self-Potential (SP) method by applying three different SP measuring techniques and combining modern technologies for data acquisition and new methods for tomographic inversion. A SP map and three static SP tomographies have been carried out to better analyse the groundwater circulation system and to better reconstruct the geometry of the landslide body. In the accumulation zone, which is the area more exposed to the geomorphological activity, a new SP measuring strategy has been applied. This strategy, based on time-continuous 2D SP tomographies, helps identify water flow changes in subsurface by studying the time series of SP tomographic images. The analysis of time-dependent changes of water infiltration in near surface is the key to better understand the hydrogeological processes underlying the ground instability phenomena. The time-lapse analysis of tomographic images has allowed us not only to investigate the correlation between the temporal changes of SP signals and rainfall events, but also to quantify the range of these changes. The modification of the distribution of the SP source accumulation zones is associated with the dynamics of the groundwater flows. These preliminary results allow us to consider the SP tomographic method as a tool for geophysical monitoring of landslide areas and encourage to develop new measuring systems for near-real time applications. 相似文献
134.
The distribution of radiogenic heat production as a function of depth in the Sierra Nevada Batholith, California 总被引:4,自引:0,他引:4
Geochemical analyses and geobarometric determinations have been combined to create a depth vs. radiogenic heat production database for the Sierra Nevada batholith, California. This database shows that mean heat production values first increase, then decrease, with increasing depth. Heat production is 2 μW/m3 within the 3-km-thick volcanic pile at the top of the batholith, below which it increases to an average value of 3.5 μW/m3 at 5.5 km depth, then decreases to 0.5–1 μW/m3 at 15 km depth and remains at these values through the entire crust below 15 km. Below the crust, from depths of 40–125 km, the batholith's root and mantle wedge that coevolved beneath the batholith appears to have an average radiogenic heat production rate of 0.14 μW/m3. This is higher than the rates from most published xenolith studies, but reasonable given the presence of crustal components in the arc root assemblages. The pattern of radiogenic heat production interpreted from the depth vs. heat production database is not consistent with the downward-decreasing exponential distribution predicted from modeling of surface heat flow data. The interpreted distribution predicts a reasonable range of geothermal gradients and shows that essentially all of the present day surface heat flow from the Sierra Nevada could be generated within the 35 km thick crust. This requires a very low heat flux from the mantle, which is consistent with a model of cessation of Sierran magmatism during Laramide flat-slab subduction, followed by conductive cooling of the upper mantle for 70 m.y. The heat production variation with depth is principally due to large variations in uranium and thorium concentration; potassium is less variable in concentration within the Sierran crust, and produces relatively little of the heat in high heat production rocks. Because silica content is relatively constant through the upper 30 km of the Sierran batholith, while U, Th, and K concentrations are highly variable, radiogenic heat production does not vary directly with silica content. 相似文献
135.
Gregory D. Lazear 《Hydrogeology Journal》2006,14(8):1582-1598
The Tongue Creek watershed lies on the south flank of Grand Mesa in western Colorado, USA and is a site with 1.5 km of topographic relief, heat flow of 100 mW/m2, thermal conductivity of 3.3 W m–1 °C–1, hydraulic conductivity of 10-8 m/s, a water table that closely follows surface topography, and groundwater temperatures 3–15°C above mean surface temperatures. These data suggest that convective heat transport by groundwater flow has modified the thermal regime of the site. Steady state three-dimensional numerical simulations of heat flow, groundwater flow, and convective transport were used to model these thermal and hydrological data. The simulations provided estimates for the scale of hydraulic conductivity and bedrock base flow discharge within the watershed. The numerical models show that (1) complex three-dimensional flow systems develop with a range of scales from tens of meters to tens of kilometers; (2) mapped springs are frequently found at locations where contours of hydraulic head indicate strong vertical flow at the water table, and; (3) the distribution of groundwater temperatures in water wells as a function of surface elevation is predicted by the model. 相似文献
136.
Study of geothermal water intrusion due to groundwater exploitation in the Puebla Valley aquifer system, Mexico 总被引:1,自引:1,他引:1
E. Leticia Flores-Márquez Gabriel Jiménez-Suárez Raymundo G. Martínez-Serrano René E. Chávez Daniel Silva Pérez 《Hydrogeology Journal》2006,14(7):1216-1230
Significant intrusion of geothermal water into fresh groundwater takes place in the Puebla Valley aquifer system, Mexico. The decline in the potentiometric surface due to the overexploitation of the groundwater induces this intrusion. This hydrological system comprises three aquifers located in Plio-Quaternary volcanic sediments and Mesozoic calcareous rocks. The hydraulic balance of the aquifer shows that the annual output exceeds the natural inputs by 12 million m3. Between 1973 and 2002, a drop in the potentiometric surface, with an 80 m cone of depression, was identified in a 5-km-wide area located southwest of the city of Puebla. Chemical analyses performed on water samples since 1990 have shown an increase in total dissolved solids (TDS) of more than 500 mg/L, coinciding with the region showing a cone of depression in the potentiometric surface. A three-dimensional flow and transport model, based on the hydrogeological and geophysical studies, was computed by using the MODFLOW and MT3D software. This model reproduces the evolution of the aquifer system during the last 30 years and predicts for 2010 an additional drawdown in the potentiometric surface of 15 m, and an increase in the geothermal water intrusion. 相似文献
137.
Characterization of water bursting and discharge into underground mines with multilayered groundwater flow systems in the North China coal basin 总被引:2,自引:0,他引:2
A conceptual framework for characterization of water bursting and discharge into underground mines with multilayered groundwater flow systems is presented, based on the features of the site conditions and analyses of the water bursting and mine inundation events of the North China coal basin. Comprehensive analyses of the hydrogeological conditions for establishment of the three-dimensional groundwater flow systems of the North China coal basin revealed different vertical hydraulic connection paths or channels. These connections include karst collapse columns, fault or fracture zones, buried weathering zones, and fracture networks in aquitards, within the multilayered groundwater flow systems. Also examined, was the effect of the primary features of the flow system and those different connection paths on water bursting and discharge into the underground coal mines. It was demonstrated that appropriately identifying and adequately understanding the three-dimensional multilayered groundwater flow systems and those various vertical hydraulic connection mechanisms are critical for appropriately preventing water bursting hazards and predicting water discharge into underground mines. A valuable guideline is presented on characterization of water bursting and discharge into underground mines with multilayered groundwater flow systems.
Resumen Un cadre de travail conceptuel pour la caractérisation du jaillissement et de la vidange des eaux dans les mines à plusieurs niveaux d'écoulement est présenté, basé sur les conditions et l'analyse sur site du jaillissement des eaux et des inondations dans les bassins charbonneux du Nord de la Chine. L'analyse compréhensive des conditions hydrogéologiques des systèmes d'écoulement tridimensionnel de ces bassins, révèle des trajets ou des chenaux qui sont autant de connections hydrauliques verticales. Ces connections comprennent des effondrement karstiques en colonne, des zones de fractures et de failles, des zones d'altération, des réseaux de fractures dans les aquitards, dans le système hydrogéologique multicouche. L'influence des caractéristiques primaires du système d'écoulement et de ces différentes connections sur le jaillissement et la vidange dans les mines, est également examiné. Il a été démontré que l'identification appropriée et la compréhension adéquate du système d'écoulement souterrain multicouche et tridimensionnel, et des mécanismes variés de connection hydraulique verticale est critiquée pour prévenir de manière appropriée les risques de jaillissement et de vidange dans les mines. Des guidelines valorisables sont présentées, pour la caractérisation du jaillissement et de la vidange dans de tels systèmes.
Résumé Se presenta un marco conceptual para la de caracterización de la despresurización y descarga de agua a minas subterráneas con sistemas de acuíferos de múltiples niveles, el cual se basa en las condiciones del sitio, análisis de la despresurización de agua e inundaciones de minas en la cuenca de carbón del norte de la China.Un análisis comprehensivo de las condiciones hidrogeológicas para el establecimiento de los sistemas de flujo de agua de tri-dimensionales en la cuenca de carbón del norte de la China ha revelado diferentes canales hidráulicos verticales. Estas conexiones incluyen columnas de karst colapsadas, fallas o zonas de fracturas, zonas de regalita hundida y redes de fracturas en zonas de poca permeabilidad dentro de los sistemas de flujo de múltiples niveles.También se investigó el efecto de los rasgos primarios del sistema de flujo y los diferentes canales conectivos sobre la despresurización y descarga de agua a minas subterráneas. Se demostró que el entendimiento e identificación adecuada de los sistemas de acuíferos de múltiples niveles en tres dimensiones es crítico para prevenir apropiadamente la despresurización y descarga de agua a minas subterráneas. Se presentan lineamientos valiosos en relación con la despresurización y descarga de agua a minas subterráneas en sistemas de flujo de múltiple nivel.相似文献
138.
Connectivity is an important measure for assessing flow transport in rock, especially through fractures. In this paper, rock
fracture systems are modelled by a discrete fracture model simulated by a marked point process. A connectivity index is then
introduced to quantify the connectivity between any two points in space. Monte Carlo simulation is used to evaluate the connectivity
index for stationary cases and relationships between the connectivity index and the parameters of the discrete fracture model
are analysed. The average number of intersections per fracture, Xf, and the fracture intensity, P12 (P32), are calculated and the relationships between these parameters and the connectivity index are investigated, concluding that
Xf is the more suitable parameter for the classification of rock mass flow properties. The relationships between the connectivity
index and the percolation state of the fractured medium are also discussed. An edge correction is briefly discussed and a
practical example is used to demonstrate the method of computing the connectivity index. 相似文献
139.
以兰州市区96条主要的泥石流沟为例,利用分形理论的统计自相似性对泥石流沟数的累计分布随沟谷形态要素沟道比降、汇水面积和沟道长度的变化进行了分析;并与不同流域形态要素的分维进行了比较,探讨了分维不同的原因。兰州市区泥石流沟三个形态要素均具有统计意义上的自相似性,其中以汇水面积显示出分维最小(0.46),沟道长度次之(0.71),沟道比降最大(1.09)。分维的大小描述了作为系统的沟谷及其泥石流的形成的空间结构,即分形结构,同时也反映了不同形态要素对系统所起作用的差异,分维越小,所起作用越显著。其结果对西北干旱半干旱地区石流灾害的进一步研究与防治提供了新的思路。 相似文献
140.
New theories to explain how tides and river flow determine estuarine bathymetries have been developed. The range of validity of these theories has been subsequently assessed against a recently available observational data set.Success in reproducing the evolution of estuarine bathymetries that has occurred over the last 10 000 years provides the basis for the translation, here, of these theories into new typologies. These then provide reference frameworks to enhance our perspective on existing morphologies and identify ‘anomalous’ estuaries. Further refinement of these new theories requires analyses of causal factors responsible for such anomalies drawing on classical morphological experience. These frameworks can also be used for calculating likely future bathymetric adjustments for prescribed changes in mean sea level, tidal amplitudes, river flow and sediment supply. 相似文献