公路工程

大型直剪试验获取粗粒土抗剪强度参数成本高、制样难度大，缩尺级配法是工程中常用的间接测试手段，但现有方法在大缩放比条件下易引起强度参数估测偏差。为此，本文提出一种基于分形维数相似准则的粗粒土缩尺级配方法，以湖南两处高速公路弃土场粗粒土为对象，控制缩尺前后级配分形维数基本一致，制备不同缩放比重制试样，并开展室内直剪试验，分析缩尺后抗剪强度参数的变化规律。在此基础上，讨论缩尺估测误差的形成机理，并建立黏聚力校正系数与最大粒径缩放比之间的经验关系。结果表明：基于分形维数相似准则的缩尺级配方法能够较好保持颗粒骨架结构，缩尺重制土内摩擦角与原始级配土接近，估测误差基本控制在5%以内；黏聚力受细粒含量相对增加等因素影响偏差较大，但通过校正系数可将误差降低至约10%；与常用平行级配法相比，本文方法在内摩擦角和黏聚力的估测精度方面均有明显改善，且对较大缩放比具有更好的适应性。研究结果可为粗粒土及工程弃渣抗剪强度参数的经济测试与工程应用提供参考。

Obtaining the shear strength parameters of coarse-grained soils through large-scale direct shear tests is costly and labor-intensive. Although the scaled gradation method is widely used as an indirect testing approach， significant estimation errors may occur under large scaling ratios. To address this issue， a scaled gradation method based on the similarity criterion of fractal dimension is proposed in this study. Two coarse-grained soils collected from highway waste disposal sites in Hunan Province were selected. Remolded samples with different scaling ratios were prepared by maintaining the fractal dimension of the gradation before and after scaling， and a series of laboratory direct shear tests were conducted to investigate the variation of shear strength parameters. On this basis， the mechanism of estimation error was discussed， and an empirical relationship between the cohesion correction coefficient and the maximum particle-size scaling ratio was established. The results show that the proposed method can effectively preserve the particle skeleton structure， and the internal friction angle of the remolded samples remains close to that of the original soil， with an estimation error generally within 5%. The cohesion shows relatively larger deviation due to the apparent increase in fine content after scaling， but the error can be reduced to about 10% using the proposed correction coefficient. Compared with the conventional parallel gradation method， the present method provides higher estimation accuracy for both friction angle and cohesion， and performs better under large scaling ratios. The proposed method offers a practical and economical approach for evaluating the shear strength parameters of coarse-grained soils and engineering waste materials.