基于数字图像分析及大型直剪试验的土石混合体块石含量与抗剪强度关系研究

RESEARCH ON RELATIONSHIP BETWEEN ROCK BLOCK PROPORTION AND SHEAR STRENGTH OF SOIL-ROCK MIXTURES BASED ON DIGITAL IMAGE ANALYSIS AND LARGE DIRECT SHEAR TEST

随着现代岩土力学的发展及各类大规模工程建设的需要,土石混合体已经逐渐被作为一种有别于常规的土体及岩石的特殊岩土材料受到国内外研究者的高度关注。土石混合体内部的块石含量及粒度组成很大程度上控制了其相应的物理力学性质。基于现代数字图像处理技术,通过对土石混合体内部块石的形态分析,获取其相应的粒度组成及块石含量,并将其作为土石混合体大尺度直剪试验的制备试样的基础,为这类岩土体的试验研究开辟了新的思路。通过大尺度直剪试验的研究结果表明,土石混合体的内部块石含量特征在很大程度上控制了其变形破坏机制,其剪应力–水平位移曲线及垂直位移–水平位移曲线均较常规的土体及岩石有很大的差别。土石混合体的剪切带将随着块石含量的增加而变宽,其内摩擦角增量与块石含量(25%～70%)近似成线性增长的关系,黏聚力较相应土体有很大程度的降低,但当块石含量大于30%时,其黏聚力随着块石含量的增加而缓慢降低。

With the development of geomechanics and the requirements of many large-scale engineering projects, soil-rock mixtures（SRM） have been regarded as a special type of soil and rock materials which are substantially different with the general soils and rocks in geotechnical engineering. In a large extent, the proportion and distribution of the rock block sizes control the physico-mechanical properties of SRM. Using digital image processing, rock block sizes in SRM samples are identified from the soil matrix. The proportion and distribution of the rock block sizes are then obtained quantitatively. Then the results are used for the sample preparation of the large scale direct shear tests, which cuts a new method for the test study of SRM. According to the results of the large scale direct shear tests, as a whole, the rock block size proportion controls the deformation and fracture mechanism of SRM. The shape of the shear stress versus the horizontal displacement curve and the vertical displacement versus the horizontal displacement curve of the remolded SRM samples are different from the general soils and rocks. With the increase of the rock block proportion, the shear band of SRM increased. When the rock block proportion lied in the range of 25% to 70%, the increment of the internal frication angle increased linearly with the increase of the rock block proportion. And the cohesion of the SRM decreased largely from the soil matrix. When the rock block proportion is large than 30%, however, there is only a little decrease in the cohesion with the increase of the rock block proportion.