Fracture Development And Disintegration Characteristics Of Paleogene Mudstone In Ningming Basin

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.