【摘要】：紅層與黃土在中國(guó)西部地區(qū)廣泛分布。黃土下伏的古風(fēng)化紅層基巖往往構(gòu)成黃土滑坡的底界,是黃土滑坡形成的控制性邊界條件。與古風(fēng)化泥巖相關(guān)的滑坡在區(qū)內(nèi)頻頻發(fā)生,造成了嚴(yán)重的人員傷亡和經(jīng)濟(jì)損失,極大地制約了當(dāng)?shù)亟?jīng)濟(jì)的正常發(fā)展。因此,認(rèn)清泥巖的風(fēng)化特點(diǎn)和工程屬性,對(duì)區(qū)內(nèi)滑坡的研究和防治都具有重要意義。本文以蘭州及其周邊地區(qū)白堊系古風(fēng)化紅層泥巖為對(duì)象,在詳細(xì)的野外地質(zhì)調(diào)查基礎(chǔ)上,選擇了9個(gè)階地卵石層下伏的古風(fēng)化紅層剖面進(jìn)行了硬度試驗(yàn)、回彈試驗(yàn)和磁化率試驗(yàn),同時(shí)在剖面上取樣并進(jìn)行了室內(nèi)崩解試驗(yàn),根據(jù)試驗(yàn)結(jié)果對(duì)卵石層下lm范圍內(nèi)的紅層泥巖進(jìn)行了風(fēng)化帶劃分,綜合研究了古風(fēng)化泥巖的崩解性和水巖相互作用,討論了古風(fēng)化泥巖對(duì)黃土滑坡的控制作用。主要結(jié)論如下：(1)硬度試驗(yàn)、回彈試驗(yàn)和磁化率試驗(yàn)結(jié)果均顯示出相同的規(guī)律,即在剖面表層其值較小,隨著深度的增加其值增大。變異系數(shù)也呈現(xiàn)出明顯的變化規(guī)律,泥質(zhì)砂巖剖面上在卵石層下10-30cm處發(fā)生突變,泥巖剖面上在卵石層下50cm處發(fā)生突變,且均從0.6左右突變至0.7左右。(2)對(duì)9個(gè)巖石剖面進(jìn)行磁化率試驗(yàn),發(fā)現(xiàn)各剖面均呈現(xiàn)出表層磁化率較大,隨著深度的增加磁化率值有所減小的趨勢(shì)。其中4個(gè)砂巖剖面表層10cm到20cm磁化率值較大,20cm以下磁化率較�。黄渌�5個(gè)泥巖剖面為表層10cm到30cm磁化率值較大,其下磁化率值較小,且有上下波動(dòng)現(xiàn)象。表層磁化率升高的原因主要為風(fēng)化作用和成壤作用。(3)崩解試驗(yàn)獲取的巖石崩解性變化特征為：卵石層以下0-30cm的巖石崩解性很強(qiáng),崩解度幾乎接近100%；30-50cm的巖石崩解性較強(qiáng)；50-100cm崩解性較弱,其中90-100cm崩解性最弱,崩解度還不到50%。(4)對(duì)試驗(yàn)結(jié)果進(jìn)行綜合分析得到黃土層底部白堊系紅層泥巖古風(fēng)化殼表面強(qiáng)風(fēng)化層深度較大,達(dá)到卵石層下30-50cm范圍,相對(duì)來說泥質(zhì)砂巖剖面強(qiáng)風(fēng)化層深度較小,處于卵石層下20-30cm的范圍內(nèi)。結(jié)合泥巖崩解過程中水溶液EC、TDS和pH值的變化規(guī)律,認(rèn)為在地下水作用下強(qiáng)風(fēng)化巖石中的可溶鹽損失嚴(yán)重,其溶解到地下水中后使地下水堿性增強(qiáng),加快了地下水對(duì)巖石膠結(jié)物的破壞,導(dǎo)致巖石抗剪強(qiáng)度持續(xù)降低,使得黃土底部強(qiáng)風(fēng)化泥巖容易發(fā)育成黃土滑坡滑動(dòng)面。
[Abstract]:Red beds and loess are widely distributed in western China. The paleo-weathered red bed bedrock under loess often forms the bottom boundary of loess landslide and is the controlling boundary condition for the formation of loess landslide. Landslides associated with paleo-weathered mudstone occur frequently in the area, resulting in serious casualties and economic losses, which greatly restrict the normal development of local economy. Therefore, it is of great significance to recognize the weathering characteristics and engineering properties of mudstone for the study and prevention of landslide in this area. Taking the Cretaceous paleo-weathered red layer mudstone in Lanzhou and its surrounding area as the object, on the basis of detailed field geological investigation, the hardness tests of the paleo-weathered red bed section of 9 terrace pebbles are carried out. The springback test and magnetic susceptibility test were carried out. At the same time, samples were taken from the section and the indoor disintegration test was carried out. According to the test results, the weathering zones of red mudstone in the range of lm under the pebble layer were divided into weathering zones. The disintegration of paleo-weathered mudstone and the interaction of water and rock are studied synthetically, and the control effect of paleo-weathered mudstone on loess landslide is discussed. The main conclusions are as follows: (1) the results of hardness test, springback test and magnetic susceptibility test all show the same rule, that is, the value of the surface layer of the section is smaller, and the value increases with the increase of depth. The coefficient of variation also showed an obvious variation law. In the shaly sandstone section there was a mutation at 10-30cm under the pebble layer, and in the mudstone section there was a mutation at the 50cm under the pebble layer. All of them have mutated from 0.6 to 0.7. (2) the susceptibility tests of 9 rock sections show that the surface susceptibility of each profile is larger, and the value of susceptibility decreases with the increase of depth. The surface 10cm to 20cm susceptibility of four sandstone sections is larger than that below 20cm, while the other five mudstone sections are the surface layer 10cm to 30cm magnetic susceptibility value is larger, its lower magnetic susceptibility value is smaller, and has the phenomenon of fluctuating up and down. The main reasons for the increase of surface magnetic susceptibility are weathering and soil formation. (3) the characteristics of rock disintegration obtained by disintegration test are as follows: the rock disintegrating property of 0-30cm below the pebble layer is very strong, and the disintegration degree is almost close to 100g; The rock disintegration of 30-50cm is strong; 50-100cm disintegration is weak, among which 90-100cm disintegration is the weakest, and the disintegration degree is less than 50%. (4) it is found that the strong weathering layer on the surface of the Cretaceous red mudstone paleo-weathering crust at the bottom of the loess soil layer is deep, and the disintegration degree is less than 50%. To reach the 30-50cm range under pebble, the depth of strongly weathered layer in shaly sandstone profile is relatively small, which is within the range of 20-30cm under pebbles. Combined with the variation of EC,TDS and pH values in aqueous solution during mudstone disintegration, it is considered that the loss of soluble salt in strongly weathered rock under the action of groundwater is serious, and the alkali of groundwater is enhanced when dissolved into groundwater. It accelerates the destruction of rock cement by underground water, which leads to the continuous decrease of shear strength of rock, which makes the strongly weathered mudstone at the bottom of loess easily develop into the sliding surface of loess landslide.
【學(xué)位授予單位】：蘭州大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P534.53;P512.13

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