岩梁弯曲流变特性的试验研究

Rheology properties of rock beams

岩石较少有直接拉伸破坏,在巷道和采场顶板中,弯曲变形是重要的变形模式。采用一次加载和分级加载两种加载方式对岩梁的弯曲流变破坏进行了试验研究,对岩梁的弯曲流变特性进行了分析,重点分析了流变条件下岩梁弯曲中性面位置的变化规律。结果表明:岩梁的顶底两侧均存在流变,虽然其大致规律相似,但存在明显的差异。岩梁底面为高应力区的拉伸流变,顶面为低应力区的压密阶段的流变。岩梁的弯曲中性面位置在流变过程中随时间而变化,并最终趋于稳定,但在不同的加载方式中性面的稳定位置差别较大。对弯曲流变与单轴压缩流变进行的比较表明,岩石单轴压缩流变的横向极限拉应变和弯曲拉伸流变的极限拉应变基本一致。

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 theological bending failure of rock beams under of single loading and stepwise loading was studied, then the characteristics of the theological 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 theological 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 theological 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 theological bending and uniaxial compression, the horizontal limit tensile strain of rock under uniaxial compression was basically the same as the limit tensile strain of theological bending.