加载速率影响抗拉强度的机理及其数值验证

井下工作面由于推进速度的不同导致覆岩对顶板的加载速率不同，使得顶板岩层表现出不同的抗拉强度，因此加载速率影响岩石抗拉强度的机理对于掌握不同推进速度下的采场矿压显现规律至关重要。通过对覆岩运移规律的分析首先定义了2种加载速率，即外力加载速率和位移加载速率；然后通过室内岩石力学实验掌握了加载速率越大岩石抗拉强度越大的规律；接着使用弹性动力学方法和分子尺度的功能原理分别解释了外力加载速率和位移加载速率影响抗拉强度的作用机理；最后，通过ANSYS/LS-DYNA对不同加载速率下的巴西劈裂实验进行了瞬态动力学分析，进一步验证了加载速率对抗拉强度的作用效果。结果表明，外力加载速率不同时系统产生的惯性力不同，位移加载速率不同时，破坏时物体的动能也不同，最终使得不同加载速率下物体表现出不同的抗拉强度。

Mechanical explanation of loading rate impact on tensile strength and its numerical simulation analysis

Different working face advancing speeds cause different loading rates on overlying strata,which makes the roofs showing different tensile strengths,so it’s very important for investigating the strata-pressure behavior how loading rate impacts on the tensile strength of rock.In this paper,two kinds of loading rates were defined after analyzing overburden migration laws,including external force loading rate and displacement loading rate.Then the law that tensile strength is bigger under the higher loading rate was obtained in Brazilian split test.And then the mechanism of external force loading rate and displacement loading rate impact on tensile strength was analyzed by using the elastic dynamics method and the principle of work-power in molecular scale.At last,the impact on the tensile strength of loading rate was verified after the transient dynamic analysis on Brazilian split test by using ANSYS/LS-DYNA.It was found that inertia force varies with external force loading rate and the kinetic energy of rock while breaking varies with displacement loading rate,so there will be different tensile strengths under different loading rates