深井大断面沿空留巷底板裂隙分形特征动态演化规律试验研究

Experimental study of dynamic evolution characteristic of floor fractal dimension of gob-side entry retaining with large section in deep mine

深井大断面沿空留巷常见严重底鼓问题,为更好揭示底鼓机理,利用自行研制的两向四面加载试验装置,结合顾桥矿1115(1)工作面轨道顺槽工程地质条件,采用相似材料模拟方法研究了深井大断面沿空留巷底板在掘进、一次采动、留巷和二次采动影响期间裂隙动态演化规律,并基于分形几何理论定量分析了分形维数变化规律及其与底鼓量的关系。研究结果表明,底板裂隙随着回采逐步发育、扩展、贯通,以剪切破坏的中高角度裂隙分布为主;底板裂隙分形维数逐渐增加,在顶板来压和留巷期间均有明显的升维现象;由于留巷上部基本顶的"回弹"现象,第二个工作面上覆岩层作用于煤体的载荷较小,导致在第二个工作面回采前期,底板裂隙分形维数增量较小;底鼓量和分形维数呈非线性正相关关系。通过对比现场实测底鼓量和试验底鼓量,发现二者能够较好吻合,验证模型试验结果的真实可靠。

It is common to see the phenomenon of serious floor heave of gob-side entry retaining with large section in deep mine. To reveal the mechanism of floor heave of gob-side entry retaining with large section in deep mine; based on the engineering geological condition of 1115(1) working face tailentry and with the self-developed physical model test equipment, a study about the dynamic evolution law of floor fracture and floor fractal dimension in excavation period, the first mining influenced period, roadway retaining period, the second mining influenced period is conducted according to fractal geometry theory. And the relation between floor fractal dimension and floor heave is obtained. The results show that: First, the floor fracture developed, expanded and penetrated gradually with mining, and the fracture distributed mainly in middle and high angles because of shear failure. Second, the fractal dimension of floor fracture increased gradually, and there is a significant rise during main roof caving and roadway retaining. Third, as the spring back of main roof; the load from overlying strata of the second working face is small; the bottom fractal dimension increases slowly. Fourth, the relation between floor heave and fractal dimension is nonlinear and positive. By comparing the field measured and tested results of floor heave, it is found that the both two can be able to fit, so as to verify the model test results is reliable.