三峡库区巴东组（T2b）紫红色泥岩工程地质特征研究

在三峡工程库区广泛分布一种三叠系中统巴东组的紫红色泥岩 ,在库区常被称为“易滑地层”。这种岩土体还具有一定膨胀性 ,致使一些边坡防护工程发生变形破坏。三峡工程库区移民区巴东、巫山、奉节等新城址出现的许多工程地质问题往往与此有关。本文在对巴东、巫山、奉节等地紫红色泥岩的基本地质特征研究基础上 ,对该地层的膨胀性、风化规律、水-岩相互作用等进行系统试验研究 ,为三峡工程库区滑坡防治和移民迁建工程提供科学依据。研究表明 :该地层粘土矿物含量一般为 1 7.9%左右 ,其中 ,有效蒙脱石含量一般在 1 .2 7～ 6 .0 1 %之间 ,混层矿物占粘土矿物的一半以上 ,具中 -强胶结 ,有弱膨胀性。岩石的风化以机械风化为主 ,沿剖面化学成分变化不大。沿剖面物理力学性质的变化除受风化作用制约外 ,受岩石颗粒组成的影响更为明显 ,因此可能出现深度异常现象。水对该地层岩石力学性质影响比较显著 ,应当特别关注水库蓄水初期库水位显著变化对边坡和地基土稳定性的影响

ENGINEERING GEOLOGICAL CHARACTERISTICS OF PURPLISH-RED MUDSTONE OF MIDDLE TERTIARY FORMATION AT THE THREE GORGES RESERVOIR

The purplish-red mudstone of the Badong group of Middle Tertiary, which is widely distributed in the Badong, Wushan and Fengjie County of the Three Gorges reservoir, is often called as ”sliding-proned formation” since most landslides occur in this formation. This paper assesses the expansive potential of the mudstone, weathering conditions, water-rock interaction and other behavior. The results show that the mineral content is approximately 17.9%, of which the montolian constitutes 1.27～6.01%, and the mix layer mineral is over 50%, and it is of a medium to strong gluing capacity and a weak expansive potential. The physical or mechanical weathering is dominant with limited changes in chemical components along the cross-section observed. The water is a dominant factor in controlling the mechnical weathering of mudstone. Therefore, the impacts of water level changes with the reservoir storage and discharge are assessed by field investigation and laboratory tests to assure the stability of the bank slope in the Three Gorges Reservoir.