三峡库区奉节新县城库岸边坡类型及岩体结构特征

奉节新县城库岸边坡自三峡水库蓄水至139 m水位以来多处出现变形破坏,库岸段岸坡变形破坏模式的复杂多样给相应的工程治理带来了较大的困难。通过研究奉节新城区库岸段岩土体类型和岩体结构特征,将新县城江北片区21.7 km的库岸划分成21个库岸段,明确了基岩岸坡和土石岸坡的分布范围,确定了库岸边坡的结构类型。针对不同的岸坡结构类型,分析了岸坡可能出现的6种变形破坏模式。岩质边坡可能出现弯曲–拉裂–倾倒型、剪切–滑移型、楔形体崩塌–滑动型和风化–剥落型变形破坏;土石岸坡可能出现弧形整体滑动型、局部剪切破坏或崩塌型变形破坏。以库岸段的可能变形破坏模式为基础,有针对性地分段采取相应工程治理措施,有利于保证库岸防治达到预期效果。

BANK SLOPE TYPES AND ROCK MASS STRUCTURAL FEATURES IN NEW FENGJIE COUNTY, THREE GORGES RESERVOIR REGION

After impoundment up to 139 m elevation in the Three Gorges Reservoir in June 2003,many geological hazards were triggered inevitably.Lots of deformation and failure phenomenon on the bank slope are dooming in new Fengjie,a county located on the Yangtze River.The complexity and diversity of deformation and failure modes of the bank slope bring many difficulties to effectively prevent instability of the bank slope and to release the threat to lives.Based on the research on rock and soil sort of the bank slope and its structural characteristics,the bank slope,which is 21.7 km long totally in 175 m elevation,is divided into 21 sections.The sections are researched respectively on the lithology,obliquity,direct relationship between slope and terrain,interrelation of different rocks and soils,and then,they are reduced to 13 structural types.Through detailed field investigation on the characteristics of the 13 structural types of the bank slopes,6 potential deformation and failure patterns are presented,such as bending-cracking-toppling,shearing-sliding,sphenoid falling-sliding and weathering-flake for rock bank slope,cambered sliding and part sliding-falling for gravel-clay bank slope.These 6 possible patterns will provide guidance for choosing proper protection measures so as to maintain stability of the bank slope.