Study On The Influence Of Hydro-Thermal Environment On The Mechanical Properties Of Mudstone

In order to explore the influence of low temperature and water content conditions on the mechanical properties of mudstone,the change law of mechanical properties of mudstone under different water content conditions and different low temperature environment was studied.The compressional wave velocity of dry mudstone is about 83% of that of saturated mudstone.Uniaxial compression test was carried out on the samples of mudstone under saturated,natural and dry water content conditions which were cured at-50? ? 10?.The uniaxial compressive strength of mudstone was measured and the change trend of its elastic modulus was explored.And put forward the expression of the uniaxial compressive strength of mudstone with water content and temperature.Scanning electron microscopy(SEM)tests were carried out on dry and saturated mudstones at-50? ? 10? to analyze the variation of their microstructure.And the mudstone is affected by low temperature environment is simulated.The results showed that:(1)The relationship between the uniaxial compressive strength and the moisture content of mudstone shows an exponential decline function.The elastic modulus of mudstone tend to decreases with the increase of water content,and the change rate of elastic modulus increases with the increase of water content.The elastic modulus increases with the decrease of temperature,and shows a linear relationship with the decrease of temperature in dry state.The rate of change increases with the decrease of temperature in natural and saturated state.The uniaxial compressive strength of mudstone increases exponentially with the decrease of temperature.The longitudinal wave velocity increases linearly with the decrease of temperature.Pore water can make the glue water connection between shale mineral is abate,and negative temperature would make its enhancement,resulting in its intensity change.Water-bearing sample are more likely to occur shear destruction,dry sample for more tensile damage.(2)The microstructure of mudstone will change with the change of water-thermal environment.The scanning electron microscope results show that the maximum area,total area and surface porosity of micro pores increase with the increase of water content,and decrease with the decrease of temperature.With the increase of water content and the decrease of temperature,the area-perimeter ratio of micro pores increases,the shape becomes more sharp and complex,and the fractal dimension will increase.(3)Through numerical simulation,it is found that the mudstone sample will have a certain degree of volumetric shrinkage under low temperature environment,and the strain gradually decreases from the center to the outside,and the thermal stress caused by cooling is mainly concentrated on both sides.When the tunnel model is affected by the low temperature environment,the settlement and horizontal displacement at the top arch,side wall and inverted arch will be reduced.The maximum stress is distributed at the side wall,and increases with the decrease of temperature.After excavation,the stress at the side wall of the surrounding rock mass decreases first and then increases until it stabilizes.