【作者】 张帆；

【导师】 贾鹏飞；

【作者基本信息】 西北大学 ， 工程硕士（专业学位）， 2021， 硕士

【摘要】 宁明盆地古近系泥岩埋深浅,具有遇水泥化、膨胀、崩解的特性,对基础工程的建设和运营造成了严重威胁。为了防治宁明泥岩造成工程地质灾害,对宁明盆地古近系泥岩开展试验研究。通过野外地质调查、室内基本物理特性试验对宁明泥岩进行分类;对试样进行增湿干湿循环试验、通过微米CT试验研究泥岩内部的裂隙发育特征;通过浸水干湿循环试验研究崩解物的级配的影响因素;通过X射线衍射试验、扫描电镜试验结合崩解特征探讨宁明泥岩的崩解机理,本文主要研究成果如下:(1)宁明古近系泥岩分布于整个宁明盆地,泥岩埋深为5～10m,宁明县为湿润多雨气候,泥岩受到风化淋滤作用明显;泥岩自由膨胀率为35%～42.5%,膨胀力>100k Pa,按照《铁路工程岩土分类标准》的分类判定为弱膨胀岩,宁明膨胀岩的侧限膨胀率和膨胀力与粘土矿物含量正相关,与试样初始含水率负相关;(2)对进行喷水增湿干湿循环条件下的试样进行微米CT扫描,使用Dragonfly软件对试样的图像进行三维重建,对图像进行合理分割,使用深度学习进行二值化分割提取裂隙图像,对裂隙图像的形态及裂隙研究发现:宁明泥岩受扰动后主要生成水平裂缝,试样经过1次干湿循后形成裂隙网发生崩解,经过5次干湿循环水平裂隙增大形成空腔,延生出更多大倾角裂缝使试样进一步崩解;(3)采用分形理论量化泥岩崩解物的级配特征,得到试样在不同烘干温度、初始试样质量、干湿循环次数条件下崩解物的分形维数。运用灰色关联法进行关联度分析,结果表明,干湿循环次数、烘干温度、试样初始质量等因素对膨胀岩的崩解产生了较大影响,得到各因素对宁明膨胀岩崩解分形维数的关联度为干湿循环次数>烘干温度>试样初始质量;(4)不同深度的泥岩矿物组分不同,所测试的浅层泥岩粘土矿物含量高于深层泥岩浅层泥岩粘土矿物含;宁明泥岩的矿物成分为石英、白云母、伊利石、绿泥石,粘土矿物中伊利石为主要成分,组成泥岩的基本颗粒主要以扁平状伊利石粘土颗粒和椭球形石英颗粒主,存在粘土颗粒胶结较松散的部位和胶结紧密的部位;崩解碎块表面的微裂隙及微孔隙发育,根据微观试验结果,宁明泥岩的崩解方式为“吸附—楔裂”崩解。更多还原

【Abstract】 The Paleogene mudstone in Ningming basin is shallowly buried and has the characteristics of cementation,expansion and disintegration.This characteristic of Ningming mudstone poses a serious threat to the construction and operation of basic engineering.In order to prevent engineering geological disasters caused by Ningming mudstone,experimental research on Paleogene mudstone in Ningming basin is carried out.Ningming mudstone is classified by field geological survey and indoor basic physical property test;the internal fracture development characteristics of mudstone are studied by humidifying dry wet cycle test and micro CT test;the influencing factors of disintegration grading are studied by soaking dry wet cycle test;the disintegration characteristics of Ningming mudstone are discussed by X-ray diffraction test and scanning electron microscope test combined with disintegration characteristics The main research results are as follows:(1)Ningming Paleogene mudstone is distributed in the whole Ningming basin,and the buried depth of mudstone is 5 ～ 10 m.Ningming County has a humid and rainy climate,and the mudstone is obviously weathered and leached.The free expansion rate of mudstone is 35% ～ 42.5%,and the expansion force is more than100 KPA.According to the classification of railway engineering geotechnical classification standard,it is determined as weak expansion rock,and the confined expansion rate and expansion force of Ningming expansion rock are related to the clay mineral content Positive correlation,negative correlation with water content;(2)The micro CT scan was carried out on the samples under the condition of water spray humidification and dry wet cycle,and the images were reconstructed by dragonfly software.The images were segmented reasonably.The binary segmentation was used to extract the fracture image by using depth learning.The morphology and crack gap of the fracture images were studied.It was found that the horizontal cracks were mainly generated after the mudstones were disturbed.The samples were followed by one dry and wet cycle After that,the fracture network disintegrated,and the horizontal cracks increased for 5 times of dry and wet cycles to form cavities,and more cracks with large inclination were produced to further disintegrate the specimen;(3)The fractal theory is used to quantify the gradation characteristics of mudstone disintegration,and the fractal dimension of mudstone disintegration under different drying temperature,initial sample mass and dry wet cycles is obtained.The grey correlation method is used to analyze the correlation degree.The results show that the dry wet cycles,drying temperature and initial quality of samples have great influence on the disintegration of expansive rock.The correlation degree of each factor on the fractal dimension of Ningming expansive rock disintegration is as follows: dry wet cycles > drying temperature > initial quality of samples;(4)The mineral composition of mudstone in different depth is different,and the clay mineral content of shallow mudstone is higher than that of deep mudstone;the mineral composition of Ningming mudstone is quartz,muscovite,illite and chlorite,and illite is the main component of clay mineral,and the basic particles of mudstone are mainly flat illite clay particles and ellipsoidal quartz particles According to the microscopic test results,the disintegration mode of Ningming mudstone is "adsorption wedge" disintegration.更多还原