| Mudstone affected by water environment.The problem of softening of mechanical properties has always been one of the important research topics in the field of water-rock interaction.In order to understand the softening mechanism of mudstone,a series of experimental studies on mudstone have been carried out in this paper.(1)Through the analysis of the physical and chemical properties of mudstone,the mudstone is composed of kaolinite,chlorite and other clay minerals and quartz and other chemical components,with a density of 2.59g/cm~3 and a natural moisture content of 0.52%.(2)The mechanical properties of mudstone in the Simian Mountain tunnel were studied experimentally,and uniaxial and triaxial tests and splitting tests were carried out.The uniaxial compressive strength of the mudstone was 61.22 MPa,the elastic modulus was 5.22 Gpa,and the average tensile strength was obtained.It is 2.30MPa(3)Through freshwater immersion test studies,the evolution law of mudstone's mechanical parameters with soaking time was revealed.The uniaxial compressive strength and elastic modulus of mudstone decrease with the negative exponent of soaking time.Based on the analysis of nuclear magnetic resonance data,it is found that the pore size of pores in mudstone increases with the soaking time;according to the results of CT non-destructive testing,It is clearly seen that the internal cracking of mudstone increases with the soaking time.(4)During the softening test,the temperature and pressure of the water were changed.It was found that the water temperature and water pressure have a greater effect on the softening of mudstone,and the compressive strength and elastic modulus of the mudstone continuously decrease with increasing temperature or water pressure.(5)On the basis of the above softening test,the softening mechanism of mudstone is analyzed.It is found that there are some tiny initial stealth cracks in the mudstone,and the water molecules are first entered into the mudstone first through the fissure,and the damage first appears in the region with large initial fissure,which leads to the emergence of the new fracture and the expansion of the initial fissure.The fissures.The water molecules are still invading some smaller cracks and pregnant with new cracks.The water molecules continue to invade and expand after the fracture occurs,thus making the original isolated fractures gradually penetrate into a larger fracture.The progressive development of mudstone fractures is the reason why rock samples are divided into fragments,thus destroying the integrity of mudstones.(6)Considering the softening characteristics of mudstone and obtaining the change law of elastic modulus with soaking time Through the conventional simulation of surrounding rock deformation and supporting forces in the mudstone section of the Simianshan tunnel and the numerical simulation of the deformation and supporting forces of the surrounding rock considering the softening effect,it is found that the mudstone is more harmful to the tunnel after being softened by the water,so it is based on four sides.The specific situation of the mountain tunnel,put forward the corresponding anti-drainage measures. |
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