巴东组紫红色泥岩干湿循环崩解特征试验研究

Disintegration characteristics of red-bed mudstone of Badong Formation under wet-dry cycles

红层泥岩受水的影响易诱发多种工程地质灾害,开展红层泥岩干湿循环崩解性质的研究具有重要意义。选取三叠系巴东组(T2b4)紫红色泥岩开展室内干湿循环崩解试验,每次干湿循环后筛分试样,通过称量获得各组分质量,并用图像处理技术提取每次筛分后岩石块体的形态特征参数。以此为基础用分形几何、灰色关联理论研究红层泥岩崩解过程中颗粒的分形与形态特征,从而建立评价红层泥岩稳定程度的模型。研究结果表明:巴东组紫红色泥岩室内干湿循环崩解试验中,粒径大于10 mm的块体崩解剧烈,且崩解过程主要集中在前8次循环,经历12次循环后停止;崩解过程中红层泥岩的分布分形维数在前8次循环中增加迅速,与红层泥岩崩解程度的变化规律相对应,随红层泥岩停止崩解而稳定在2.20;各粒组颗粒圆形度与覆盖盒维数的变化特征与红层泥岩崩解程度的变化规律也具有对应关系,随其崩解的停止而逐渐趋于稳定;灰色关联结果表明:崩解过程中红层泥岩圆形度的变化特征能更好地反映其崩解的状态,对工程建设中红层泥岩稳定程度的评价具有一定的指导意义。

Since various water-induced geological disasters occur in the red-bed mudstone, it is important to study disintegrating states of red-bed mudstone under dry and wet cycles. A series of wet and dry cycle tests was conducted on mudstone samples from Triassic Badong Formation. After each cycle, every group of screened particles was weighed, and morphological parameters of rock sample were also obtained using an image processing technique. With the combination of the fractal geometry theory and the gray relational analysis, the fractal characteristics of size distribution and the morphological characteristics of rock particles were gained. Thus, a new model was established to evaluate the stability of the red-bed mudstone. The results show that rock particles with a size larger than 10 mm disintegrated dramatically, which mainly occurred in former eight times cycles and tended to stop after 12 times cycles. Corresponding to the evolution of disintegration process, the fractal dimension of size distribution rapidly increased and stabilized at around 2.20 by the end of disintegration. Meanwhile, both the circularity of rock particles and the dimension of covering boxes showed correlations with disintegrating degree and eventually stabilized when the disintegration ended. From the gray relational analysis, the variation characteristics of circularity of the red-bed mudstone well reflect its disintegrating state. Therefore, the stability evaluation of the red-bed mudstone has a significant guidance in engineering construction.