Experimental And Theoretical Research On Sand Particle Under Cyclic Unloading And Loading

In life we often see temporary support device, are widely used in building, bridge, tunnel and coal mines, the most common life is a sandbox style of temporary supports, it uses closed dry sand in the container, the opening is easy to flow out so as to reduce the design principle of the sand volume of container at the bottom of the container or the side. Different coping can use many sandbox sand to adjust height. After the other processes to complete, need to be placed temporary support girders to permanent support is only need to unscrew the screw switch, Sandbox side tapping, the sand will flow out, beam will decrease with the sandbox sand under the action of self weight falls to the permanent support, which is convenient and simple. But still has its shortcomings and deficiencies, the basis for the selection of sand, when the stress is not stable sand can withstand the maximum displacement problem. Has important theoretical reference value and engineering significance to solve the problem.Study on sand as filling material and its mechanical properties, using the same method of controlling variables commonly used in the experiment, the study of these3variables are:size, thickness, loading mode, the study of its mechanical properties, comprehensive strength, the extent of damage, to find out the stress and the relationship between unconfined and research variables, experimental use RMT-150B test machine, do uni-axial compression, using the cyclic loading experiment; mechanical properties of sand under cyclic loading conditions, the experiment used again to other parameters, such as the apparent density, bulk density, loading rate of these parameters throughout the beginning; the thickness of sand with different particle diameter, cyclic loading and unloading experimental study of sand, the cyclic loading and unloading maximum can withstand the stress strength of sand, and the relationship between stress and strain, the statistics of the rule of the strength of different size, and draw the stress-strain curves and elastic modulus, Poisson’s ratio and so on a series of parameters; hope to further improve; to provide reference and basis for the temporary support device. And the establishment of three models:1) the same amount of cyclic loading and unloading stress-strain curve equation.2) cyclic constitutive relationship between frequency and axial deformation of different thickness under the condition of same diameter. 3) cyclic constitutive relationship between frequency and axial deformation under the condition of same thickness with different particle size.