NUMERICAL SIMULATION OF TEMPORAL-SPATIAL DISTRIBUTION OF PORE-FLUID PRESSURE INDUCED BY ZIPINGPU RESERVOIR IMPOUNDMENT

doi:10.3969/j.issn.0253-4967.2015.02.013

Abstract

Abstract:

The depth dependence of permeabilities of the fault rocks collected from the ruptures of 2008 Wenchuan earthquake and their host rocks were experimentally determined. On the basis of the measurement data, the temporal-spatial distributions of pore-fluid pressure induced by Zipingpu reservoir impoundment were numerically simulated. Modeled results indicate that the pore-fluid pressure is closely related to the patterns of the permeabilities. In other words, the results with the depth dependent permeabilities are strikingly different from those with the constant permeabilities. Existence of a fault hydro-dynamically connecting to the bottom of reservoir has a significant influence on the simulation of fluid infiltration owing to higher permeability in fault zones. The wider the fault zone is, the more obvious of fluid infiltrating along the fault. If fault width ranges from 100m to 300m, the pore-fluid pressure in the hypocenter region is about 0.1~0.15MPa, which is comparable with the normal stress caused by the reservoir impoundment on fault zone near the hypocenter of 2008 Wenchuan earthquake. This simulation provides an important constraint on the studies associated with the potential relationship between Zipingpu reservoir impoundment and Wenchuan earthquake.

Key words: Zipingpu Reservoir impoundment, Wenchuan earthquake, fluid infiltration, numerical simulation, temporal-spatial distribution of pore-fluid pressure

摘要：

通过对汶川地震破裂带上的断层岩及围岩的渗透率测量, 获得了研究区岩石的渗透率随深度变化的规律。依据所得到的渗透率实验数据, 数值模拟了紫坪铺水库蓄水所产生的流体孔隙压的时空分布。模拟结果显示, 渗透率是否随深度变化, 其流体孔隙压的模拟结果也相差很大。由于断层带具有高渗的特点, 因此与水库底部存在水力联系的断层带及其宽度对流体渗透的模拟结果有明显的影响。断层带越宽, 下渗作用越明显, 流体孔隙压的分布与断层带的产状越接近。若断层带宽度为100~300m, 2008年汶川M_S8.0地震发生时, 其震源区的流体孔隙压为0.1~0.15MPa, 与库体载荷在断层面上产生的附加正应力相当。该模拟结果可以作为进一步分析汶川地震的发生是否与紫坪铺水库蓄水存在关联的重要约束。

关键词: 紫坪铺水库蓄水, 汶川地震, 流体渗透数值模拟, 流体孔隙压时空分布, 渗透率实验

CLC Number:

P315.9

YANG Yu, YANG Xiao-song, DUAN Qing-bao. NUMERICAL SIMULATION OF TEMPORAL-SPATIAL DISTRIBUTION OF PORE-FLUID PRESSURE INDUCED BY ZIPINGPU RESERVOIR IMPOUNDMENT[J]. SEISMOLOGY AND GEOLOGY, 2015, 37(2): 510-523.

杨彧, 杨晓松, 段庆宝. 水库蓄水与断层带流体孔隙压时-空分布的数值模拟——以紫坪铺水库为例[J]. 地震地质, 2015, 37(2): 510-523.

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