| A tunnel in southwestern Shanxi is located in the Luliang Mountains connected to the eastern edge of the Ordos Basin.The geological background of this area is complex and diseases occur frequently.In this case,in order to study the conditions and mechanisms of the development of the disease in the surrounding rock,the surrounding rock of the tunnel was sampled and studied Among them,the marl,breccia and gypsum exposed in the tunnel are the most typical.Studying its petrological characteristics and special engineering properties not only has a positive effect on the treatment and prevention of tunnel diseases,but also on similar surrounding rocks in the future.The construction of the section project has certain reference and guiding significance.In this paper,in addition to studying the structural characteristics of the lithological core taken,it also further studies the composition and structural characteristics of marl,breccia and gypsum from the thermal and optical aspects,using differential thermal method and thermogravimetric method,X-diffraction method,infrared spectroscopy method,thin section observation and scanning electron microscope observation and other methods to carry out multi-faceted,multi-angle,targeted research and analysis of gypsum,marl and breccia.At the same time,for its special engineering properties,the uniaxial compression test,point load test,rheological test,and expansion test are mainly used to study its mechanical properties and hydraulic properties.General overview.After analyzing and studying the lithology of the tunnel stratum,the main conclusions of this paper include the following aspects:(1)According to the lithological findings revealed by the drilling of the entire tunnel,the distribution of marl,gypsum and gypsum breccia in the tunnel is extremely uneven,indicating that the formation lithology at the tunnel is also relatively complex.(2)Scanning electron microscopy analysis of marl and gypsum breccia revealed that the mineral composition and element content of different parts of the rock sample are the same,indicating that the mineral composition in the rock body is unevenly distributed.(3)Corresponding to the distribution mileage of marl,gypsum rock and gypsum breccia in the tunnel and the distribution mileage of the disease in the past years,it is found that the surrounding rocks are the three types of lithology,and there are more diseases.It can be speculated that the occurrence of tunnel diseases is directly related to these three types of rocks.(4)Anhydrite rock can be transformed into hydrated anhydrite rock and gypsum rock through hydration,and the statistical discovery of boreholes in gypsum rock reveals that it is mostly hydrated anhydrite rock,indicating that after excavation,the tunnel is large Some anhydrites have different degrees of hydration,and there is a tendency to continue to intensify. |
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