本文選題：紅層巖質(zhì)滑坡　切入點：軟弱夾層　出處：《成都理工大學》2017年碩士論文

【摘要】：川東北紅層地區(qū)一直是四川地質(zhì)災(zāi)害多發(fā)區(qū)。近年來隨著極端降雨條件的頻頻發(fā)生,在川東北紅層地區(qū)形成了大量的緩傾角順層巖質(zhì)滑坡,造成了巨大的人員傷亡和財產(chǎn)損失,如2004年9月5日發(fā)生的達州宣漢縣,天臺鄉(xiāng)滑坡,受災(zāi)人數(shù)達2500人;2007年6月18日發(fā)生的四川盆地群發(fā)性滑坡,造成1933間房屋垮塌;2011年9月16日發(fā)生的南江縣群發(fā)性滑坡,共造成2人死亡7人失蹤,166戶房屋垮塌,直接經(jīng)濟損失15.11億;2015年6月28日特大暴雨誘發(fā)地質(zhì)災(zāi)害使全縣48個鄉(xiāng)鎮(zhèn)48.9萬余人不同程度受災(zāi),造成2人死亡1人失蹤,損毀房屋18104間,直接經(jīng)濟損失達19.27億元。目前研究認為極端降雨使斜坡后緣裂隙中形成靜水壓力和潛在滑動面揚壓力使斜坡發(fā)生失穩(wěn)破壞,但通過詳細野外調(diào)查發(fā)現(xiàn)部分滑坡不具備后緣形成高水頭的條件。針對這一問題對南江縣紅層區(qū)大量順層巖質(zhì)滑坡進行現(xiàn)場勘查發(fā)現(xiàn)滑坡的形成與先期巖層中軟弱夾層有關(guān),軟弱夾層特別是發(fā)生了泥化的軟弱夾層是滑坡孕育的重要地質(zhì)條件,研究泥化夾層的形成及演化成為研究順層巖質(zhì)滑坡的關(guān)鍵,研究軟弱夾層在地下水長期作用下的強度特征是預(yù)防和治理該類巖質(zhì)滑坡核心。本文通過詳細的現(xiàn)場調(diào)查及大量的室內(nèi)試驗,研究了泥化夾層形成的宏觀和微觀演化特征。通過資料查閱和收集,和現(xiàn)場編錄分析了軟弱夾層的分布特征,形成過程與沉積環(huán)境、地質(zhì)構(gòu)造的關(guān)系以及形成泥化夾層的地質(zhì)條件和控制因素;通過XRD衍射試驗、電子顯微鏡觀察試驗、顆粒級配分析試驗、ICP陽離子分析試驗、離子色譜儀陰離子分析試驗等手段分析了泥化前后礦物成分變化、微觀結(jié)構(gòu)變化特征、離子成分及濃度變化等規(guī)律。討論了內(nèi)外地質(zhì)作用對泥化夾層形成過程的影響,對泥化夾層的形成過程有了初步的認識。(1)南江縣紅層地區(qū)軟弱夾層主要為剪切破碎帶,泥化夾層形成于裂隙發(fā)育地下水活躍的近地表卸荷帶;泥化夾層的形成主要劃分三個階段,軟弱巖沉積階段(沉積軟巖)→構(gòu)造剪切階段(層間剪切破碎帶)→地下水水化學作用階段(含泥剪切破碎帶)→泥化夾層形成階段(泥化夾層);模擬實驗表明靜水環(huán)境下軟弱夾層的泥化過程是非常緩慢的。(2)通過泥化模擬試驗,結(jié)果表明,結(jié)構(gòu)越破碎、粘土礦物含量越高,泥化速率越快,干濕循環(huán)作用主要使泥巖發(fā)生結(jié)構(gòu)破碎,也會增加試樣的比表面積加速易溶鹽溶解,但不會明顯加速水化學反應(yīng);剪切破碎帶到泥化帶的演變過程中,結(jié)構(gòu)變得松散,粘土礦物特別是綠泥石、伊利石等粘土礦物增多,長石等骨架礦物變少;泥化夾層在浸水后粘土礦物會轉(zhuǎn)化成更加穩(wěn)定的硅的氧化物;電鏡掃描圖片中可見疊瓦狀、玫瑰花瓣狀綠泥石含量和蜂窩狀蒙脫石含量明顯增加。(3)對三處不同軟弱夾層礦物成分的對比研究發(fā)現(xiàn),粘土礦物和長石的含量越高的原巖越易發(fā)生泥化,且泥化后粘粒含量更高;在地下水長期作用下長石高嶺石等礦物含量明顯減小,而伊利石、綠泥石、蒙脫石明顯增多,表明泥化過程就是硅鋁質(zhì)礦物向粘土礦物轉(zhuǎn)化的過程。(4)軟弱夾層浸水后主要溶蝕Na~+、Ca~(2+)、Mg~(2+)、Al~(3+)、K~+、HCO_3~-、Cl~-、SO_4~(2-)等離子,陽離子相對濃度c(Na~+)c(Ca~(2+)),陰離子相對濃度c(HCO_3~-)c(SO_4~(2-))c(Cl~-),主要溶蝕NaHCO_3、Ca(HCO_3)_2、Na_2SO_4、CaSO_4等易溶鹽;模擬試驗中浸水溶液PH值和導電率都出現(xiàn)了不同幅度是上升,浸水過程中離子濃度隨浸水時間增加,長石水解生成了強堿使水溶液呈弱堿性。(5)通過巖石的直剪試驗獲得了不同浸水時間后泥巖的剪應(yīng)力-剪位移曲線,發(fā)現(xiàn)未經(jīng)歷過失水過程的泥巖的剪應(yīng)力-剪位移曲線可以表現(xiàn)出脆性變化特征,且抗剪強度較大,天然狀態(tài)c、φ值分別為3.25MPa,39.27°;泥巖的抗剪強度參數(shù)c、φ值均隨浸水時間出現(xiàn)不同程度衰減;通過直剪試驗獲得了軟弱夾層原狀樣在不同飽水時間后的抗剪強度特征曲線及強度參數(shù),抗剪強度參數(shù)c、φ分別從0.85MPa降低到0.22MPa,32.64°衰減到10.59°,衰減擬合曲線均呈二階指數(shù)關(guān)系;通過泥巖、軟弱夾層的浸水剪切試驗發(fā)現(xiàn),飽水到一定時間水對巖土體的內(nèi)聚力削弱作用比內(nèi)摩擦角更大,泥巖強度的衰減幅度小于軟弱夾層,表明結(jié)構(gòu)越松散,軟化效應(yīng)越明顯(特別是內(nèi)聚力的衰減);通過土的直接剪切試驗,獲得了不同飽水時間下泥化夾層的抗剪強度,當泥化夾層含水率飽和度較大時,浸水含水率變化不大,而力學強度仍有衰減,結(jié)構(gòu)也發(fā)生明顯的變化,表明地下水長期作用會削弱土體的結(jié)構(gòu)和力學性質(zhì)。
[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). 瀵逛笁澶勪笉鍚岃蔣寮卞す灞傜熆鐗╂垚鍒嗙殑瀵規(guī)瘮鐮旂┒鍙戠幇,綺樺湡鐭跨墿鍜岄暱鐭崇殑鍚噺瓚婇珮鐨勫師宀╄秺鏄撳彂鐢熸償鍖，

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