| The sandstone belongs to the terrigenous clastic rock series.Its organic matter content is extremely low,vegetation is difficult to grow,and water and soil loss are easily caused by water erosion and wind erosion.In recent years,with the gradual advancement of engineering construction in the Pisha sandstone area and the improvement of people's awareness of environmental protection,people pay more and more attention to the engineering nature of Pisha sandstone.Using sandstone as a resource,research and develop economical and environmentally friendly building materials,so that sandstone can be more widely used in agricultural bridges and culverts,earth dam slope protection,channel anti-seepage,and foundation treatment.It can not only reduce the cost of treatment,but also realize the treatment of pimple sandstone from another angle and improve the utilization effect of pimple sandstone.In this thesis,the red sandstone in Zhungeerqi area of Ordos City is taken as the research object.Study on Mechanical Properties and Durability of Vermiculite Sand Cement Soils with Different Cement Contents.With the help of 3D imaging and X-ray diffraction,Scanning electron microscope,nuclear magnetic resonance and other technologies to conduct in-depth analysis of the evolution of microstructure of sandstone cement soil.Research indicates:1?This paper analyzes the effects of age and cement content on the sandstone cement soil from the perspective of energy.The energy dissipation is closely related to the strength attenuation of the sandstone cement soil.To some extent,the effective energy ratio increases with the increase of cement content.Under different ages,the amount of Pisha-sandstone cement soil with cement content is mainly to absorb elastic energy.With the increase of age and cement content,the total damage energy and peak energy indicators of cement soil are increasing.2?Triaxial shear tests were performed on the sandstone cement soil under different cement contents to investigate the influence of cement content and the number of freeze-thaw cycles on the cohesion and internal friction angle of the sandstone cement soil.And with the help of Leica Ultra Depth of Field microscope on the surface microstructure of the sandstone cement soil,it was found that the increase of cement content can significantly improve the frost resistance of the sandstone cement soil.3?The salt invasion test was carried out on the sandstone cement soil,and it was found that the strength of the sandstone cement soil decreased with the increase of the salt intrusion days.The more cement content,the better the resistance to erosion.4?The T2 spectrum,porosity,irreducible fluid saturation,and free fluid saturation obtained by NMR tests were used to study the pore changes of the sandstone cement soil.It was found that with the increase of salt invasion time,the porosity of the cement soil under different cement contents increased.The porosity of cement soil with an amount of 10%or less increases with the increase of free fluid saturation.Cement soil with an amount of 15%or more is increased with the increase of irreducible fluid saturation.The increase of the porosity is not conducive to the increase of the strength of the cement soil,but the increase of the small porosity causes the strength to weaken slightly.5?Combined with X-ray diffraction and scanning electron microscopy to observe the changes of material formation and micro-morphology of the sandstone cement soil after salt invasion,the mechanism of deterioration of the sandstone cement soil under sodium salt invasion was explored.With the increase of salt invasion time,the expansion force of salt invasion products such as gypsum and so on gradually accumulates and accumulates.The expansion force generated is greater than the cementation force produced by gelling substances such as C-S-H.In addition,montmorillonite in vermiculite has strong hydrophilicity.Causes gradual deterioration of the pores until the specimen fails. |
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