Experimental Study On Formation Mechanism And Impermeability Of Thermal Cracking Of Deep Frozen Shaft Lining Concrete

In recent years,with the shallow resources of coal production mines gradually dried up,in order to ensure the sustainable development of the mine,most of the mines in the two Huai mining area need to implement the safety expansion project and build a new deep shaft.These new shafts have deep bore and large diameter and are rich in water through the deep alluvium.When the freezing sinking,the wall thickness design,high strength concrete,concrete hydration heat,the inner and outer high temperature difference and constraint,concrete is extremely easy to produce temperature crack,which pose a threat to the safe use of the wellbore.Accordingly,in order to solve the problem of water leakage in deep frozen shaft,this paper adopts the method of measurement,theoretical analysis and simulation experiments combined with the site,and to study the impermeability mechanism of temperature crack of concrete wall in deep freeze,provide the basis for the prevention and treatment of water wells.First of all,to the East return shaft of Guqiao Coal Mine as the engineering background,selected monitoring level,on the freezing section of outer lining stress,deformation and temperature is measured,the results show that the vertical stress of reinforcement and concrete vertical tensile strain,wall temperature crack to easily generate ring.Then,according to the principle of elastic mechanics and thermodynamics,the stress analysis of freezing wall under the constraint conditions of temperature,temperature stress formula is derived,analyzed in the freezing sinking process of concrete wall temperature crack mechanism,and pointed out that the crack is very unfavorable to the prevention and control of water freezing wall.Finally,through simulation experiment,the characteristics of temperature crack and impermeability of frozen concrete lining are studied.The experiment is divided into two parts:(1)To simulate the temperature cracks produced with standard anti permeability specimens were studied.The results show that the impermeability and anti permeability properties mainly depend on the nature of the crack,and the strength of concrete has little relationship,through the crack on the wall impermeability effect greatly;(2)Making the cylinder containing simulated temperature crack the specimen through three axis permeability test analysis of water pressure and the effect of confining pressure on crack permeability.The results show that when the control axial pressure and confining pressure are constant,the seepage velocity of concrete cracks increases with the increase of water pressure.While the control of water pressure and axial pressure are constant,the seepage velocity of concrete cracks decreases with the increase of confining pressure.