含水率对红砂岩抗拉强度及形貌特征的双线性曲线影响研究

为探究含水率对红砂岩抗拉强度及断面形貌的影响,对不同含水率的红砂岩试样进行巴西劈裂试验,并利用Talysurf CLI2000三维表面激光形貌仪对劈裂后试样断面进行扫描,分析并定量描述形貌参数的变化趋势。结果表明,含水率低于临界含水率时,抗拉强度受含水率影响微弱,含水率超过临界含水率时,抗拉强度受含水率影响强烈。当含水率趋于饱和(约4.67%)时,红砂岩抗拉强度降低20%左右;随着含水率的增加,形貌特征参数变化反映断面总体呈现由凸凹不平到缓和平稳的趋势,断面分形维数值减少直至趋向于2(断面趋近二维平面),高度直方图和Abbott-Firestone曲线变化趋势表明断面高度分布变集中且均匀、断面起伏趋于平缓。

Influence of water content to the tensile strength of a red sandstone and bilinear curve of morphological characteristics

To explore the influence of water contents on the tensile strength and the fracture surface of red sandstone, the fracture surface of red sandstone were obtained by Brazilian disc tests. Subsequently, the fracture surface was scanned by Talysurf CLI 2000, its scanning data were analyzed quantitatively. The results indicated that when the water content was under the critical value ( the intersection of two lines), the influence was slight. On the contrary, the influence was significant. The tensile strength of the red sandstone with the saturated water content decreased to approximately 20% of the red sandstone under dry condition. With the increase of water content, the fracture surface changed from bumpy to stable, which is reflected by the variation of morphological parameters. The fractal dimension value of the fracture surfaces decreased and eventually tended to be 2. The histograms of the asperity heights and the Abbott-Firestone curves showed that the fracture surface tended to be uniformly distributed and flat with the increment of water contents.