北京南口地区构造特征与虎峪水坝渗流稳定性分析

Characteristics of Shangkou-Nankou Fault and Its Influence on Seepage Stability of Huyu Dam,Beijing

南口地区地处军都山隆起与京西丘陵平原区的过渡部位。系统的野外调查、地形地貌解析、节理统计分析,结合基岩样品显微组构研究表明,区内上口—南口断裂总体表现为正断性质,自燕山早期形成以来,其经历了由压性转变为张性的力学过程,南口地区主应力σ1在侏罗纪为NW—SE向,早白垩世以来为NEE—SWW向。上口—南口断裂最晚活动时期为晚更新世晚期,库区构造背景较不稳定。虎峪水库现今储水不满,下游地下潜流发育,是由于基岩中密集发育的节理渗流而引起的,且主要受控于早期区域NW—SE向挤压运动产生的顺河流走向节理。为了提高水库储水能力,建议对其进行防渗加固处理。

Nankou is located in the transition region between Jundushan uplift and the hill-plain area of western Beijing.The systematic field-investigation,terrain analysis,statistical analysis of joints and microscopic structure studies of bedrock are applied in our works.It is suggested that the overall performance of Shangkou-Nankou fault is normal,it experienced mechanical process from compression into tension after it had originated in Early Yanshanian,while the corresponding principal stress σ1 in Jurassic is NW-SE and it translated into NEE-SWW from Early Cretaceous.The latest active period of Shangkou-Nankou fault is Late Pleistocene,and the modern crustal movement of the reservoir area is less stable.The intensive joints in bedrock are the dominant factors for dam seepage and the most effective joints which approximately parallel to the river toward are controlled by early NW-SE compression.A stabilization works should be carried out in order to improve storage capacity of the reservoir.