Rheology properties of rock beams

The bending deformation was a kind of important deformation mode in the tunnels and roofs of coal mines because direct tensile failure of rock seldom happened.The bending tests on rock beams were usually achieved by the way of three-point or four-point bending.The rheological bending failure of rock beams under of single loading and stepwise loading was studied,then the characteristics of the rheological bending of rock beams were analyzed,and the variation of neutral surface of rock beams under the rheological conditions as analyzed.It was shown that there were significantly different rheological deformations on top and bottom of rock beams with broadly similar regulation.The bottoms of rock beams were in the high-stress tensile rheological zone,but the tops of rock beams were in the low-stress compressive rheological zone.The position of neutral surface of rock beam varied with time in the course of rheological deformation,and the variation was stabilized at last,but the stable location of neutral surface was different greatly in different loading ways.With the comparison of rheological bending and uniaxial compression,the horizontal limit tensile strain of rock under uniaxial compression was basically the same as the limit tensile strain of rheological bending.