【摘要】：我國(guó)西南地區(qū)廣泛分布著峨眉山玄武巖,該區(qū)域炎熱多雨的氣候,特別有利于巖石的化學(xué)風(fēng)化,風(fēng)化的巖石與新鮮巖石在完整性、礦物組成、力學(xué)特性等差異特別顯著。風(fēng)化的巖石是滑坡、泥石流、石漠化等地質(zhì)災(zāi)害最重要的物質(zhì)來(lái)源之一,同時(shí)風(fēng)化巖體的建基面及其所取的最優(yōu)值是巖土工程師們、設(shè)計(jì)者們長(zhǎng)期關(guān)注的問(wèn)題。本文以峨眉山玄武巖斜坡非飽和帶低滲透性的結(jié)構(gòu)體作為研究對(duì)象,通過(guò)野外調(diào)查以及室內(nèi)試驗(yàn)例如：SEM、薄片鑒定、巖石全化學(xué)分析等,系統(tǒng)、深入的分析了風(fēng)化過(guò)程中巖石的宏微觀特征、礦物組成、化學(xué)元素移動(dòng)性等的變化規(guī)律。風(fēng)化結(jié)構(gòu)體呈現(xiàn)明顯的圈層結(jié)構(gòu),外層為腐巖,內(nèi)部為核心石,風(fēng)化程度由內(nèi)向外明顯增大,核心石與腐巖殼三維界線區(qū)域突變特別顯著,核心石表面溶蝕不明顯,孔隙、裂隙不發(fā)育。然而,腐巖表面溶蝕嚴(yán)重,造巖礦物如斜長(zhǎng)石等粘土化現(xiàn)象明顯,可觀察到礦物呈不規(guī)則的鱗片狀,孔隙極其發(fā)育。在風(fēng)化程度較低的風(fēng)化前期,Fe2O3的含量增加明顯而FeO的含量虧損顯著,其他元素的遷移性行為并不明顯或者說(shuō)對(duì)于風(fēng)化程度的變化敏感性并不顯著。風(fēng)化程度較高的風(fēng)化中、后期,巖石的主量元素如活動(dòng)性相對(duì)較弱的如Al等、遷移性較強(qiáng)的Na、Ca等以及不同價(jià)態(tài)的Fe其行為與風(fēng)化程度的變化敏感性顯著,兩者之間關(guān)系明確簡(jiǎn)單,同時(shí)表征巖石物理力學(xué)參數(shù)如密度、孔隙度、抗壓強(qiáng)度等隨著風(fēng)化的進(jìn)行也在顯著變化,即使是微風(fēng)化的玄武巖,相對(duì)于母巖而言,完整性、宏觀特征無(wú)明顯差異,但是,力學(xué)強(qiáng)度卻發(fā)生了急劇的減少,這可從微觀觀察到的微裂隙發(fā)育以及結(jié)構(gòu)面出現(xiàn)的鐵質(zhì)渲染物質(zhì)解釋強(qiáng)度減小的原因。在上述研究的基礎(chǔ)上,根據(jù)結(jié)構(gòu)體風(fēng)化過(guò)程中主量元素的遷移特征,提出了新的風(fēng)化指數(shù)：A-FM風(fēng)化指數(shù),對(duì)比既有的風(fēng)化指數(shù)如CIW、CIA、R等,無(wú)論是風(fēng)化程度較低的前期還是風(fēng)化程度較高的中、后期,A-FM指數(shù)與巖石的風(fēng)化程度關(guān)系簡(jiǎn)單明確,敏感性顯著,因此,A-FM指數(shù)可作為玄武巖風(fēng)化程度評(píng)價(jià)的重要依據(jù)。
[Abstract]:Emeishan basalts are widely distributed in southwest China. The hot and rainy climate in this area is especially conducive to the chemical weathering of rocks, and the differences between weathered rocks and fresh rocks in integrity, mineral composition and mechanical properties are particularly significant. Weathered rock is one of the most important sources of geological hazards, such as landslide, debris flow, rocky desertification, etc. At the same time, the foundation surface of weathered rock body and its optimum value are the problems that geotechnical engineers and designers pay close attention to for a long time. In this paper, the low permeability structure in the unsaturated zone of the Emeishan basalt slope is taken as the research object. Through field investigation and laboratory tests, such as SEM, sheet identification, rock total chemical analysis, etc. The changes of macro and micro characteristics, mineral composition and mobility of chemical elements during weathering are analyzed. The weathering structure shows obvious circle structure, the outer layer is saprophyte, the inner part is the core stone, the weathering degree increases obviously from inside to outside, the abrupt change of three-dimensional boundary area between core stone and saprophyte crust is especially remarkable, the surface dissolution of core stone is not obvious, and the pore is not obvious. The fissures are not developed. However, the surface of the saprophyte is seriously corroded, and the clay-forming phenomena of rock-forming minerals such as plagioclase are obvious. The minerals can be observed to be irregular scales, and the pores are extremely developed. In the early stage of weathering with low weathering degree, the content of Fe2O3 increased obviously, the content of FeO decreased significantly, and the migration behavior of other elements was not obvious or sensitive to the change of weathering degree. In the weathering with higher weathering degree, in the late stage, the main elements of rock such as relatively weak activity such as Al, Na,Ca with strong migration, and Fe with different valence states are sensitive to the change of behavior and weathering degree. The relationship between the two is clear and simple, and the physical and mechanical parameters such as density, porosity and compressive strength of rock are also changed with weathering. There is no obvious difference in macroscopic characteristics, but the mechanical strength has been sharply reduced, which can be seen from the microscopic development of microcracks and the explanation of the intensity of the iron rendering material on the structure surface. On the basis of the above research, a new weathering index, A-FM weathering index, is proposed according to the migration characteristics of principal elements in the weathering process of structural bodies, and the existing weathering indices such as CIW,CIA,R, etc., are compared. The relationship between the A-FM index and the weathering degree of rock is simple and clear, and the sensitivity is significant, whether it is in the early stage of low weathering degree or in the middle weathering stage with high weathering degree, therefore, the relationship between the A-FM index and the weathering degree of rock is obvious. A-FM index can be used as an important basis for evaluating the weathering degree of basalt.
【學(xué)位授予單位】：昆明理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P588.145

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