红层地区软弱夹层形成演化规律及泥化特征研究

发布时间：2018-03-26 12:15

  本文选题：红层岩质滑坡　切入点：软弱夹层　出处：《成都理工大学》2017年硕士论文

【摘要】：川东北红层地区一直是四川地质灾害多发区。近年来随着极端降雨条件的频频发生,在川东北红层地区形成了大量的缓倾角顺层岩质滑坡,造成了巨大的人员伤亡和财产损失,如2004年9月5日发生的达州宣汉县,天台乡滑坡,受灾人数达2500人;2007年6月18日发生的四川盆地群发性滑坡,造成1933间房屋垮塌;2011年9月16日发生的南江县群发性滑坡,共造成2人死亡7人失踪,166户房屋垮塌,直接经济损失15.11亿;2015年6月28日特大暴雨诱发地质灾害使全县48个乡镇48.9万余人不同程度受灾,造成2人死亡1人失踪,损毁房屋18104间,直接经济损失达19.27亿元。目前研究认为极端降雨使斜坡后缘裂隙中形成静水压力和潜在滑动面扬压力使斜坡发生失稳破坏,但通过详细野外调查发现部分滑坡不具备后缘形成高水头的条件。针对这一问题对南江县红层区大量顺层岩质滑坡进行现场勘查发现滑坡的形成与先期岩层中软弱夹层有关,软弱夹层特别是发生了泥化的软弱夹层是滑坡孕育的重要地质条件,研究泥化夹层的形成及演化成为研究顺层岩质滑坡的关键,研究软弱夹层在地下水长期作用下的强度特征是预防和治理该类岩质滑坡核心。本文通过详细的现场调查及大量的室内试验,研究了泥化夹层形成的宏观和微观演化特征。通过资料查阅和收集,和现场编录分析了软弱夹层的分布特征,形成过程与沉积环境、地质构造的关系以及形成泥化夹层的地质条件和控制因素;通过XRD衍射试验、电子显微镜观察试验、颗粒级配分析试验、ICP阳离子分析试验、离子色谱仪阴离子分析试验等手段分析了泥化前后矿物成分变化、微观结构变化特征、离子成分及浓度变化等规律。讨论了内外地质作用对泥化夹层形成过程的影响,对泥化夹层的形成过程有了初步的认识。(1)南江县红层地区软弱夹层主要为剪切破碎带,泥化夹层形成于裂隙发育地下水活跃的近地表卸荷带;泥化夹层的形成主要划分三个阶段,软弱岩沉积阶段(沉积软岩)→构造剪切阶段(层间剪切破碎带)→地下水水化学作用阶段(含泥剪切破碎带)→泥化夹层形成阶段(泥化夹层);模拟实验表明静水环境下软弱夹层的泥化过程是非常缓慢的。(2)通过泥化模拟试验,结果表明,结构越破碎、粘土矿物含量越高,泥化速率越快,干湿循环作用主要使泥岩发生结构破碎,也会增加试样的比表面积加速易溶盐溶解,但不会明显加速水化学反应;剪切破碎带到泥化带的演变过程中,结构变得松散,粘土矿物特别是绿泥石、伊利石等粘土矿物增多,长石等骨架矿物变少;泥化夹层在浸水后粘土矿物会转化成更加稳定的硅的氧化物;电镜扫描图片中可见叠瓦状、玫瑰花瓣状绿泥石含量和蜂窝状蒙脱石含量明显增加。(3)对三处不同软弱夹层矿物成分的对比研究发现,粘土矿物和长石的含量越高的原岩越易发生泥化,且泥化后粘粒含量更高;在地下水长期作用下长石高岭石等矿物含量明显减小,而伊利石、绿泥石、蒙脱石明显增多,表明泥化过程就是硅铝质矿物向粘土矿物转化的过程。(4)软弱夹层浸水后主要溶蚀Na~+、Ca~(2+)、Mg~(2+)、Al~(3+)、K~+、HCO_3~-、Cl~-、SO_4~(2-)等离子,阳离子相对浓度c(Na~+)c(Ca~(2+)),阴离子相对浓度c(HCO_3~-)c(SO_4~(2-))c(Cl~-),主要溶蚀NaHCO_3、Ca(HCO_3)_2、Na_2SO_4、CaSO_4等易溶盐;模拟试验中浸水溶液PH值和导电率都出现了不同幅度是上升,浸水过程中离子浓度随浸水时间增加,长石水解生成了强碱使水溶液呈弱碱性。(5)通过岩石的直剪试验获得了不同浸水时间后泥岩的剪应力-剪位移曲线,发现未经历过失水过程的泥岩的剪应力-剪位移曲线可以表现出脆性变化特征,且抗剪强度较大,天然状态c、φ值分别为3.25MPa,39.27°;泥岩的抗剪强度参数c、φ值均随浸水时间出现不同程度衰减;通过直剪试验获得了软弱夹层原状样在不同饱水时间后的抗剪强度特征曲线及强度参数,抗剪强度参数c、φ分别从0.85MPa降低到0.22MPa,32.64°衰减到10.59°,衰减拟合曲线均呈二阶指数关系;通过泥岩、软弱夹层的浸水剪切试验发现,饱水到一定时间水对岩土体的内聚力削弱作用比内摩擦角更大,泥岩强度的衰减幅度小于软弱夹层,表明结构越松散,软化效应越明显(特别是内聚力的衰减);通过土的直接剪切试验,获得了不同饱水时间下泥化夹层的抗剪强度,当泥化夹层含水率饱和度较大时,浸水含水率变化不大,而力学强度仍有衰减,结构也发生明显的变化,表明地下水长期作用会削弱土体的结构和力学性质。
[Abstract]:Northeast Sichuan Red layer area has been the Sichuan geological disaster prone areas. In recent years, with the frequent occurrence of extreme rainfall in Northeast Sichuan area, red layer to form a large number of gently inclined bedding rock landslide, caused huge casualties and property losses, such as the September 5, 2004 Dazhou Xuanhan County Tiantaixiang landslide. The number of affected up to 2500 people; landslide of Sichuan basin group in June 18, 2007, resulting in 1933 houses collapsed; in September 16, 2011 occurred in Nanjiang County landslide group, a total of 2 people were killed 7 people missing, 166 houses collapsed, the direct economic loss of 1 billion 511 million; in June 28, 2015, torrential rain induced geological disasters make 48 county towns of more than 48.9 people affected to varying degrees, resulting in 2 deaths and 1 people missing, 18104 houses damaged, the direct economic loss of 1 billion 927 million yuan. The present study of extreme rainfall the slope after edge crack formation The potential sliding surface of hydrostatic pressure and uplift pressure make slope destabilization, but through the detailed field investigation found that some do not have the form of high head landslide trailing edge conditions. In order to solve the problem of Nanjiang County Red layer large bedding rock landslide were found landslide formation and early rock in weak interlayer on the scene, especially the soft sandwich sandwich argillization is an important geological condition of landslide research, argillation formation and evolution has become a key research layer of rock landslide, strength characteristics in groundwater under long-term effects of weak interlayer on prevention and treatment of this kind of rock slope through detailed field core. Investigation and experiments on the macroscopic and microscopic characteristics of the evolution of clay interlayer formation. Through data collected and analyzed, and the distribution of soft interlayer catalog The characteristics, formation process and sedimentary environment, the relationship between geological structure and geological conditions of the formation of clay interlayer and control factors; through XRD diffraction experiment, experimental observation on electron microscopy, particle size analysis test, ICP cation analysis test, ion chromatography anion analysis test means the change of mineral mud before and after analysis, microstructure characteristics the law, ion composition and concentration changes. Discuss the geological action of clay interlayer formation, with a preliminary understanding of the forming process of argillation. (1) County Red Layer in Nanjiang area mainly for the weak interlayer shear fracture zone, mud layers formed in the active fissure groundwater near surface discharge take charge of development; formation is mainly divided into three stages of siltized mud, soft rock sedimentary stage (sedimentary soft rock, tectonic stage (broken) shear layer shear zone), groundwater water Effects of phase (mud shear zone) and argillation formation stage (argillation); simulation results show that the process of mud hydrostatic environment of weak interbed is very slow. (2) through the mud simulation test results show that the structure is broken, the higher the content of clay mineral, clay rate the faster, wet and dry cycle mainly cause the mudstone structure broken, will also increase the specific surface area to accelerate the dissolution of soluble salts, but not significantly accelerated water chemical reaction; shear fracture zone to the evolution of the mud, the structure became loose, clay minerals such as chlorite, illite clay minerals increased. Feldspar mineral skeleton less; clay interlayer clay minerals after immersion in water will be converted into more stable silicon oxide; scanning electron microscopy images in visible imbricate, rosette and honeycomb chlorite smectite content increased significantly (3). 瀵逛笁澶勪笉鍚岃蒋寮卞す灞傜熆鐗╂垚鍒嗙殑瀵规瘮鐮旂┒鍙戠幇,绮樺湡鐭跨墿鍜岄暱鐭崇殑鍚�閲忚秺楂樼殑鍘熷博瓒婃槗鍙戠敓娉ュ專�

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