丹江口水库续建工程

水库诱发地震指在水库蓄水后,由于库水作用,改变了库区原有地震活动的频度和强度,而形成的地震。经过60多年的研究,取得了一些进展,但仍有许多问题有待于进一步解决。例如,至今还没有一个成熟的理论来解释水库诱发地震机制,并且研究大多还处于定性阶段。丹江口水库是我国已建成的最大水库之一,其续建工程是我国跨世纪宏伟工程-南水北调的源头。水库自1967年下闸蓄水后,库区地震活动加强,并于1973年在宋湾爆发了4.7级地震,震中烈度达7度,这对于大坝和库区人民生命财产的安全无疑是一种威胁。续建工程中,水位提高后是否会诱发更强的地震,是人们普遍关注的问题。因此,研究丹江口水库诱发地震具有十分重要的社会意义和理论意义。本文以丹江口水库为对象,研究大型水库的诱发地震机制,并针对丹江口水库续建工程的地震活动做出评价,主要进行了以下几个方面的深入研究: 1、通过分析丹江口水库区的地震地质条件和水文地质条件,研究其对水库诱发地震的影响。分析结果表明,丹库区水文地质条件复杂,有利于库水向深部渗透,诱发地震。而汉库区水文地质条件简单,库区多由透水性微弱的岩石组成。库水向深部渗透困难,难以诱发地震。 2、分析丹江口水库初期蓄水前后地震活动特点,发现丹库在蓄水后地震活动加强,但汉库的地震活动在蓄水前后变化不大。蓄水位和地震有着明显的正相关性,震区由库尾移向库首,并在丹库的林茂山和宋湾形成了两个地震密集区。但是,当水位达到初期工程最高水位,并诱发了4.7级地震后,蓄水位和地震的相关性逐渐消失,地震的活动性明显降低。 3、首次运用地理信息系统软件Mapinfo构建了可视化的丹江口水库诱发地震基础数据库,它为丹江口水库续建工程的地震预测、库区的防灾减灾提供重要的依据。该数据库系统可以安装在任何一台以Windows95/98/2000为操作平台的计算机上,通用性较好,并具有良好的可扩充性。数据库中各种基础数据可随时进行追加和调整,系统人机交互性好,操作方便。 4、首次根据丹江口库区的地质构造建立三维有限元模型,结合实测资料反演库区的构造应力场、地应力场和水压应力场,探讨水库诱发地震机制。计算结果表明,在水库诱发地震中,水体只起到触发作用,其诱发作用体现在几个方面:改变库区断层的稳定性;在库岸形成拉应力区,使地壳浅层的原有节理、
工业羊毛毡
The reservoir-induced seismicity (RIS) is formed due to impoundment, which changes the frequency and intensity of earthquakes at the reservoir area. Though the research of RIS has achieved a lot by the efforts of more than sixty years, there are problems to resolve. For example, now there is not a mature theory to explain the mechanism of RIS, and many researches belong to the qualitative analysis. The Danjiangkou reservoir is one of the built large-scale reservoirs at home, its subsequent project is the headstream for south-to-north water diversion project. The seismic activity in the reservoir area enhanced and the largest event with magnitude 4.7 occurred in Songwan Gorge on November 29, 1973. The intensity of the earthquake is 7, which heavily threatened the safeties of dam and inhabitant. Whether the new seimicity will occur is regarded after the water level rises in the subsequent project. So the research of Danjiangkou Reservoir induced seismicity is profound. The Paper aims at exploring the mechanism of RIS basd on Danjiankou reservoir, and evaluates the seismic activity of its subsequent project. Therefore, the researches include several factors as follows:1. Collect and analyze some materials on geology, and hydrology, and research the influences of geological and hydrological conditions on RIS. The study shows that the hydrological condition of Danjiang reservoir is very complex, which is helpful for water to percolate deeply and trigger earthquake. However, Hanjiang reservoir consists of watertight rock and has simple geological condition, so it is difficult for water to percolate deeply and to induce reservoir seicmicity.2. Analyze and compare the seismic characteristic after impoundment in the initial project of Danjiangkou reservoir. The data shows that the seismic activity in Danjiang reservoir became strong, while that in Hanjiang reservoir remained unchangeable. The water levels are correlated to seismicity. Hypocentrum move to the bank of reservoir, and form two seismic concentrated place-Linmaoshan and Songwan. However, the correlated property gradually disappear and seismic activity decrease when water levels come to the highest levels of the fist stage project and correspondingly trigger earthquake with 4.7 magnitude.3. The visual database of Danjiankou reservoir induced seismicity is developed based on the Geography information system-Mapinfo. It is an important reference to the evaluation of earthquake, quakeproof and reducing disaster of reservoir area. The system can be installed in any computer whose operational system is windowa95/98/200, which can be expediently expanded by adding and modifying basic data. It has simple interactive interface that is help to operate.4. The study firstly sets up 3-D definite element models in terms of the seismotectonics of Danjiangkou reservoir area to calculate tectonic stress field, earth stress field and stress field of water pressure basing on the real imformation. In lights of the calculation of stress field of water pressure, water acts as triggering roles in RIS, and the roles include several respects as follows: change the stability of faults; form main tense stress regime in the bank of reservoir, which leads to the open of original cracks and makes it easy for water to permeate deeper places; decrease the strength of rock; Pore pressure decreases effective stress of fault panels, which correspondingly decreases the strength of fault.5. The tectonic stress field is researched in detail, the data shows that faults have important influence on distribute and direction of stress field. The stress of faults is lower than that of adjacent area. Stress in those places which are the ends of faults and where faults are about to intersect is concentrated. While it is lower in the point of intersection of faults.6. Completely analyze the stress field, strain field and strain energy at Danjiangkou reservoir area before and after impound. On the same time consider the stress field of water pressure to come up with dangerous places in the in subsequent project in terms of intensity. The results are valuable to the quakeproof in reservoir area.7. The geodynamic method is firstly used to evaluate the seismicity in the subsequent project of Danjiangkou reservoir. The results show that the possibility of RIS is very great after the water levels of reservoir rise. The biggest earthquake magnitude is 4.5.On the basis of the summary of the whole article, the study comes up with some problems to resolve and suggestions.