高铁地基低黏土矿物泥岩微膨胀性定量评定研究

Quantitative evaluation of micro-swelling property for mudstone with low clay minerals in foundations of high-speed railways

微膨胀性地基红层泥岩遇水引起的高速铁路无砟轨道路基上拱,已成为当前阻碍中国高速铁路发展又一关键因素,合理评定低黏土矿物泥岩微膨胀性对高速铁路设计和施工具有重要意义。以兰新高速铁路为依托选取等效蒙脱石含量、阳离子交换量、自由膨胀率和液限为微膨胀性判别指标,通过大量现场地基泥岩钻孔实测资料,提出了地基泥岩微膨胀潜势分级标准,采用改进层次分析法、基尼系数法和相对熵理论确定了判别指标组合权重,基于线性综合评定法建立了泥岩微膨胀性定量评价模型。结果表明:判别指标间有一定线性关系,其作为泥岩判别与分级指标具有较好分类特性;泥岩微膨胀潜势分级标准可实现94%样本的3项指标一致性;线性综合评价法克服了同一试样不同指标属于不同等级判别缺陷,可使泥岩微膨胀性进行量化,并得出了泥岩微膨胀潜势定量分级标准;通过室内膨胀力试验验证了泥岩微膨胀性定量评定及分级方法对兰新高铁适用性。研究成果对类似地质条件高速铁路路基长期持续上拱变形的工程控制措施提供理论依据。

The upheaval damage of subgrades of high-speed railways caused by muddy water on weakly expansive foundations has become another key factor hindering the development of China’s high-speed railways.It is of great significance for the design and construction of high-speed railways to evaluate the swelling property of mudstone correctly.The equivalent montmorillonite content,cation exchange capacity,free expansion rate and liquid limit are selected as the indexes of swelling property of mudstone based on the Lanzhou-Urumqi High-Speed Railway.The grading standard for swelling expansion potential of mudstone is proposed based on a large number of field measured data of mudstone borehole.The combined weights of discriminant indexes are determined by the improved analytic hierarchy process,Gini coefficient method and relative entropy theory.A quantitative evaluation model for the swelling property of mudstone is established based on the linear comprehensive evaluation method.The results show that there is a certain linear relationship between the discriminative indexes,and it has good classification characteristics as a discriminant and classification index of mudstone.The classification standard for swelling potential of mudstone can realize the consistency of three indexes for samples of 94%.The linear comprehensive evaluation method overcomes the shortcomings of different indexes of the same sample belonging to different levels.It can quantify the swelling property of mudstone and obtains quantitative classification standard for swelling potential of mudstone.The applicability and accuracy of the quantitative evaluation and grading method for swelling property of mudstone of the Lanzhou-Urumqi High-Speed Rail way are verified by laboratory swelling force tests.The research results may provide a theoretical basis for engineering control measures of long-term continuous arch deformation in subgrades of high-speed railways with similar geological conditions.