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三峡工程库首区及狮子口重力滑动构造系统的构造应力场研究

宋利好 杨森楠 吴树仁 任建业   

  1. 中国地质大学
  • 收稿日期:1995-06-20 修回日期:1995-06-20 出版日期:1995-12-20 发布日期:1995-12-20

STRESS FIELD OF THE EASTERN AREA OF THE YANGTZE GORGE RESERVOIR AND THE SHIZIKOU GRAVITATIONAL GLIDING SYSTEM

Song Lihao, Yang Sennan, Wu shuren, Ren Jianye   

  1. China University of Geosciences, Wuhan 430074
  • Received:1995-06-20 Revised:1995-06-20 Online:1995-12-20 Published:1995-12-20

摘要: 基于野外实测和室内测试,计算分析及有限元模拟,对三峡工程库首区燕山期和喜山期的区域构造应力场以及狮子口重力滑动构造应力场进行研究。区域构造应力场的主要特征是:燕山主期σ1和σ1近水平,分别近S-N向和E-W向,σ2近直立,差异应力200MPa、变化范围150-250MPa;喜山主期σ1近水平,总体方向NNE70-SW250°,差异应力100MPa,变化范围80-120MPa,在空间变化上,前者表现为南部差异应力高于北部差异应力,后者的变化规律不太明显。狮子口重力滑动构造系统的应力场比较复杂,总体呈近E-W向的前缘挤压、后缘拉伸,而滑动系统内部叠置产出的三个滑块也分别表现出后缘拉伸、前缘挤压并交替出现的特点,反映了区域应力场背景下的局部构造应力场特征。

Abstract: Systematic Study on the regional Stress field in the eastern area of the Yangtze Gorge Reservoir and the local stress for the Shizikou gravitational gliding system has been carried out by stereographic and statistical analyses on numerous conjugate joints, slickensides, styolites and micostructures including fractures with their veinlets, pressure solution seams and tectonic lenses. The regional principal compressive stress (σ1 )is determined to be horizontal with two stress groups directed S-N and NEE75°-SWW250°respectively. Based upon quantitative analysis on regional paleostress field by rock rupture criterion combined with e-twin ratio and dislocation density methods, the differential stress during S-N compressive deformation is estimated at 200Mpa, whereas that during NEE75°-SWW250°compression at 80-120MPa. The cross-cutting relationships between conjugate joints, fault striae, microstructures and regional faults and folds indicate that the S-N-and NEE75°-SWW250°oriented compressions were active during the main stages of the Yanshanian and the Himalayan movements respectively. It is shown by finite-element simulation that the Yanshanian differential stress in the southern area has higher strength than that in the northern section In contrast, no significant spacial variations in differential stress have been found for the Himalayan compression. Stereographic and statistical analyses on minor structures inside the Shizikou gravitational gliding system reveal that the stress field of that system is generally characterized by front-edge compression and hack-edge extension with gently dipping σ3 towards NE SW and moderately dipping to nearly vertical σ1 at the back edge, and gently dipping σ1 towards NE-SW and moderately dipping to nearly verticalσ3 at the front edge. The strss field of the Shizikou gravitational gliding system is defined to be the local one superimposed on the regional field yielded by the main stage of the Yanshanian movement.