Study On Deterioration Mechanism Of Weakly Cemented Siltstone Under Alkaline Water Environment In Dananhu NO.7 Mine

In this paper,we take the weakly cemented siltstones of the Dananhu No.7Mine as the main research object,and comprehensively use theoretical analysis,laboratory tests and other research methods to change the microstructure,mineral composition and macromechanical properties of weakly cemented siltstones in different alkaline water environments.And macro damage characteristics,revealing the deterioration mechanism of weakly cemented siltstones in alkaline water environment.The main research results are as follows:?1?It is determined that the weakly cemented siltstone sandstone of the Dananhu No.7 Mine has a cementation form of pore cementation,with less cementite content,most of the debris components are quartz and feldspar,and the cementitious clay is kaolinite.,There are obvious loose particle accumulation on the surface,a small number of secondary pores and pores develop,it is a typical weakly cemented soft rock;?2?The weak cemented silt sandstone alkali water immersion test and X-ray diffraction and electron microscope scanning results show that as the pH increases,the particle size of the mineral particles becomes smaller or even disappears,the mineral particles change from round to sharp,and dissolution holes and cracks appear on the rock surface;quartz,long The total stone content decreases,the kaolinite content greatly increases,the concentrations of Al³⁺,Fe³⁺,and SiO₃^2-in the solution increase,and the K⁺concentration stabilizes at the initial concentration after a certain period of time,and the Mg²⁺and Ca²⁺concentrations decrease;?3?Mechanical tests on weakly cemented silt sandstones eroded by alkaline solutions show that:the degradation of mechanical parameters has a significant time effect.The longer the immersion time,the lower the compressive,tensile,and shear strengths;as the pH increases,various mechanical parameter indicators decrease.The sensitivity to degradation of elastic modulus and cohesion is low,and the sensitivity to degradation of compressive and tensile strength is high;the length of the stress-strain curve in the compaction phase increases,the strain increases,the peak stress in the yield phase decreases,and the residual stress in the residual phase decreases.Residual stress decreased significantly;the form of shear failure is always shear failure,and the vertical fracture surface increases and the roughness of the tensile fracture surface increased;?4?It is revealed that the degradation of weakly cemented silt sandstone in alkaline water environment is mainly affected by three types of water-rock chemistry:swelling hydration,dissolution-dissolution,and ion exchange.When pH is low,it is dominated by swelling hydration and hydrolysis;when pH is around 10,it is dominated by hydrolysis and alkaline corrosion,supplemented by swelling hydration,accompanied by partial ion exchange;medium strong alkali Under normal conditions,alkaline corrosion is the main factor,supplemented by expansion and hydration,accompanied by a small amount of ion exchange,and the hydrolysis basically stops.The paper has 31 figures,10 tables and 78 references.