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剪胀性是岩土材料的重要特性之一,为研究不同工况条件下粗粒料室内大型直剪试验中的剪胀特性,采用新型室内大型直剪仪对3组不同含水率、4组不同剪切速率、5组不同含砾率等3种不同影响因素的试样进行了室内大型直剪试验,分析了剪切时试样的垂直位移与水平剪切位移及垂直应力的关系。试验结果表明:在保持其他影响因素相同条件下,垂直应力的增加导致相同水平剪切位移对应的剪缩量增加;试样的最大剪缩量随着含水率的增加有一定程度的增大,而随着剪切速率的增加而减小;含砾率低于30%试样的最大剪缩量较含砾超过于30%试样的剪缩量大很多,最大剪缩量差别为3倍。当试样含砾率小于50%时,由于试样中富含细颗粒的影响,使得应力-应变曲线具有应变软化属性以及剪胀性趋于一固定值。峰值强度前的应力比-位移增量关系采用非线性的二次项拟合比线性关系的拟合度更好,认为Matsuoka提出的二维剪胀公式不适用于粗粒料,将其修正成二次多项式并给出试验中的经验参数μ的取值区间。
Dilatancy is one of the most important characteristics of geomaterials. In order to study the dilatancy characteristics of large-scale direct shear tests of coarse aggregates under different working conditions, Different shear rates and five different gravel ratios were used for large-scale indoor direct shear tests. The relationship between vertical displacement and horizontal shear displacement and vertical stress was also analyzed. The experimental results show that under the same conditions of other factors, the increase of the vertical stress leads to the increase of the shear-shrinkage corresponding to the same horizontal shear displacement. The maximum shear-shrinkage of the sample increases with the increase of the moisture content to a certain extent, But decreases with the increase of the shear rate. The maximum shear shrinkage of samples containing less than 30% gravel is much larger than the shear shrinkage of samples containing more than 30% gravel, with a maximum difference of 3 times . When the gravel ratio of the sample is less than 50%, the stress-strain curve has the properties of strain softening and dilatancy tends to a fixed value because of the influence of the fine particles in the sample. The fitting of the nonlinear quadratic term to the linear relationship of stress-displacement increments before peak strength is better than that of the linear relation. It is considered that the two-dimensional dilatancy formula proposed by Matsuoka is not suitable for coarse aggregates and is amended to Quadratic polynomial and gives the experimental value of the experimental parameters μ interval.