RELIABILITY BASED ANALYSIS ON RESERVOIR INDUCED EARTHQUAKES |
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| Authors: | WEI Hai YANG Hua-shu WANG Ming-ming WANG Lin LIAO Min |
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| Affiliation: | 1. Faculty of Electric Power Engineering, Kunming University of Science and Technology, Kunming 650500, China;
2. Faculty of Land Resources Engineering, Kunming University of Science and Technology, Kunming 650500, China |
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| Abstract: | Reservoir induced earthquakes (RIE) are caused by impoundment of reservoir,with the characteristics of small magnitude and shallow focal depth,but they can also lead to not only economic loss,but also many serious secondary disasters,such as dam destruction,landslide,producing greater damages far more than the damages directly produced by earthquakes.So study on RIE is quite significant in the field of dam construction,thus more attentions should be paid to RIE.There are many factors to induce reservoir earthquakes,such as geological condition,rock mass mechanical index,state of crustal stress,pore pressure distribution,all of which are extremely difficult to measure due to the presence of many randomness;even if applying most advanced methods to measure them,the values fluctuate in great range,without a certain value in time and space.The great variety of these parameters gives rise to troubles to analyze RIE by deterministic approaches.How to handle the randomness of these factors has become vital problem in the field of RIE research.In this study,based on probability theory,and taking the main influence factors as stochastic variables,a new method to analyze probability of RIE was proposed by applying reliability theory.Firstly,the factors inducing reservoir earthquakes were analyzed,of which pore pressure in fault caused by water impounding of reservoir plays a vital role in triggering earthquakes.Then,taking these factors,including attitude,friction coefficient,cohesion of fault plane,stress state of fault plane and pore pressure in fault,as stochastic variables,performance function of triggering earthquakes was established by applying Coulomb stress on the fault plane,and reliability theory was used to analyze probability of earthquake induced by main factors.A special case analysis showed that:(1) The probability of induced earthquakes dramatically increases as pore pressure in fault increases;under the condition of equal pore pressure at triggering earthquakes area,probability of induced earthquakes obviously rises with enlarging of variation of pore pressure;(2) those faults with strike approximately parallel to horizontal maximum principal stress direction or with steep dip angle about more than 60° are prone to inducing earthquake;(3) as horizontal minimum principal stress increases,which has greater effect on induced earthquakes than horizontal maximum principal stress,probability of induced earthquakes becomes lower and fault keeps in more stable condition;(4) probability of induced earthquakes gradually decreases with the increase of friction coefficient and cohesion of fault plane;However,the effect of friction coefficient on induced earthquakes is much greater than the cohesion of fault plane. |
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| Keywords: | reservoir induced earthquake stochastic variable Coulomb stress reliability analysis |
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