【作者】 王志兵；

【导师】 徐则民；

【作者基本信息】 昆明理工大学 ， 道路与铁道工程， 2008， 硕士

【摘要】 云南昭通头寨滑坡的失稳岩体主要为二叠系峨眉山无斑玄武岩。滑坡体体积达900×10~4 m~3,其中400×10~4 m~3滑离源区;滑坡后缘到前缘最远端的斜长和水平投影长度分别为3423 m和3330 m,相对高差为763 m,平均坡降13°。滑坡堆积体主要有玄武岩碎屑和粘土矿物组成,其显著特征是:级配不连续、无分选、空间变化不显著:化学风化产生的次生粘土矿物在滑坡堆积物中的比例约为9%,并主要以蒙皂石为主。滑床基岩为无斑玄武岩,滑床纵断面从上向下由倾角分别为48°、38°和15°的三段组成;其中第一段为主滑带。借助化学全分析、薄片鉴定及扫描电镜等测试、观察手段,对头寨滑坡主滑带杏仁状玄武岩及滑坡体玄武岩及其腐岩玄武岩腐岩的岩石化学和矿物学特征进行了描述。化学全分析结果表明新鲜玄武岩与核心石在除铁元素外,其它组分无明显的改变;核心石在转变为腐岩过程中Si、Ca、Na、Mg等元素逐渐流失,Fe、Al等逐渐富集,同时烧失量和化学蚀变指数显著增加,硅铝比逐渐减少。薄片鉴定表明主要矿物化学风化作用顺序为玻璃质、辉石、斜长石,与造岩矿物风化稳定性序列一致,腐岩中主要的次生矿物为蒙皂石及绿泥石。在扫描电镜下观察到风化前锋形态曲折,风化前锋附近矿物呈现物理裂痕,沿着解理面更易出现,风化前锋两侧的岩石矿物形态差异显著。岩体的化学-物理耦合风化作用不仅表现在宏观尺度上,而且在细观-微观的尺度上更为明显。铁元素的价态变化存在于玄武岩腐岩形成的整个过程之中并导致岩石体积增大,从而产生物理裂纹。对滑坡区泉水的动态监测及室内模拟试验表明:地下水主要源于降雨,其化学成分与处于非饱和带的玄武岩化学风化作用密切相关;风化层中的易溶盐、吸附阳离子、腐殖酸会进入地下水,同时雨水中的组分也会被不同程度地吸附;饱和带岩体与地下水反应规模不显著。风化作用破坏玄武岩晶体结构、化学键、减小离子半径、破坏电荷平衡、增加结构的孔隙度,从而削弱晶体间的联结力,使得风化程度不高的玄武岩岩石块力学强度锐减。头寨滑坡是受以杏仁状玄武岩薄层为基础发育的破劈理化层间错动带的主滑带、褶皱运动对滑体产生构造裂隙与柱状节理、物理-化学耦合风化及侧向卸荷作用共同控制作用形成的。沿结构面发生的化学风化形成的腐岩壳使岩体进一步转变为“石夹土”结构,削弱甚至切断了岩块之间的直接联系,将低岩体的力学强度及稳定性,促使岩体从固相介质向松散介质演化,加剧了坡体的时效变形并导致其最终失稳。坡体滑出源区碰撞解体后,来自腐岩壳、具有润滑和密封功效的以粘土矿物为主的细粒组分弥漫于核形石之间,不仅使土石集合体呈现流体特性,而且还使其在进入地效区后能够暂时封闭其下方空气,实现其在气垫上的远程滑移,因此,风化过程及其产物对滑坡的发生及滑体的高速远程滑移均起到了关键性的控制作用。更多还原

【Abstract】 The failured rockmass of Touzhai landslide is permian system nonporphyritic basalt of emeishan basalt. Touzhai basalt landslide has a volume of 900×104 m³, in which 400×104 m³ of rock and soil slid away from the source area. The oblique length, its horizontal projection length and superelevation from crown to tip of the landslide are 3423 m, 3330 m and 763 m respectively. The landslide deposit is composed mainly of basalt debris and clay mineral minerals and its gradation is discontinuous. The space change of the deposit ingredient and structure is not conspicuous. Lay mineral in the giant basalt blocks account for 9% . The surface of rupture consists of three parts from the toe of surface of rupture whose dip is 48°, 38°and 15°respectively, in which the first part is main sliding zone, that is, main scarp.Rock chemical and mineralogical characteristics of fresh basalt and its saprolite is investigated by chemical analyses, optical observation of thin sections and SEM （scanning electron microscopic）. Chemical analysis showed that components of fresh basalts and corestones has few changes except that the changes in Fe²⁺ to Fe³⁺ are most noticeable. In the course of corestones changing to saprolite elements of Si, Ca, Na and Mg and the ratio of SiO₂/Al₂O₃ decrease gradually, while elements of Fe, Al and values of LOI and CIA has a significant increase. The weathering front under SEMs is tortuous, and physical weathering cracks which are easier emergence along the cleavage plane can be observed in the vicinity of the weathering front. Weathering order of main minerals is dissolution of the glass, pyroxene and feldspar, which are in agreement with the sequence of weathering-resistant minerals. The main secondary mineral is smectite and chlorite. Rock coupling chemical weathering with physical weathering processes not only exists in the macro-scale, but also in the meso-scale and micro-scale. Changes in the valence of iron takes place in the whole formation process of basalt saprolite, and leads to a volume increases, resulting in physical cracks.The observations of groundwater in the landslide area and the indoor simulation experiments show that: groundwater mainly originate from rainfall and its chemical composition is closely related to the chemical weathering of basalt in unsaturated zone, the soluble salts, adsorption cation, humic acid in weathered soil layer will enter the groundwater, at the same time, the components of the rain will be adsorbed by the weathered soil; The reaction scale between basalt in saturated zone and groundwater is not significant.Basalt crystal structure, chemical bonding, and charge balance will be damaged and ionic radius will be decreased and the porosity of the structure will be increased during the weathering processing, thus the link between crystals will be decreased, The loss of the mechanical strength of the slightly weathered basalt rock is significant.A interbed sliding zone with fault-slip cleavage in an amygdaloidal basalt thin layer made up the embryo of the main sliding zone and the coupling chemical weathering with physical weathering based on lateral unloading made the interbed sliding zone get a material prone to slide finally. The Columnar joints and structural fractures from fold movement made the potential landslide body appear a fragment-mosaic structure, and the saprolited crusts from chemical weathering taking place along discontinuity surfaces made the rockmass evolve into the structure of rock sandwiching soil, which accelerated the time-dependent deformation process of the rockmass.After the landslide occurred, the main body knocked against the slopes of Touzhai valley at a high speed and disintegrated and fine grains, especially clay minerals, from saprolited crusts pervaded among basalt corestones and acted as lubricant and encapsulant. They made the soil-rock aggregate present fluid characteristics. On the other hand, these fine component sealed the air under the soil-rock aggregates after the aggregates dropped into ground effect region, which made the materials from main body move on the air cushion at a long distance. So, chemical weathering process and its products are important to the occurrence of Touzhai landslide and the high speed, long-distance drift of the landslide body.更多还原