铁路路基火山渣填料工程特性试验

Engineering properties testing of scoria as railway subgrade fill

为了解决天然火山渣难压实、检测指标低问题,采集现场火山渣试样,开展室内土工试验,分析天然火山渣多孔隙特征、矿物成分与物理力学性质;掺配粉土质砂后进行混合土现场填筑试验,讨论不同掺配比对改良火山渣填料工程特性影响规律.研究表明:火山渣颗粒表面粗糙且内部多孔隙,其开口孔隙率与压碎率呈正相关,洛杉矶磨耗率<50.0%;细集料可以抑制改良土骨架颗粒破碎;改良火山渣材料K30指标随细集料体积分数升高先增加后降低,契合骨架空隙、骨架密实及悬浮密实3种粗颗粒土体结构过渡形式,体积掺配比为4∶1~2∶1的改良土属泛骨架密实结构,在掺配比为2∶1时达到最优工程特性.火山渣颗粒块体性好,硬度较高,掺配粉土质砂改良火山渣能显著提升其力学性能,建议采用颗粒间间隙率作为改良火山渣填料的现场压实控制指标.

Natural scoria has issues regarding field compaction and testing indices,which needs to be resolved.Laboratory soil testing was conducted on natural scoria samples collected in field to reveal its vesicular structure,mineral phase,mechanical and physical properties.The impact of silty sand addition and mixing ratio on the engineering properties of mixed soils was explored by field compaction tests.Results indicate that the particles of scoria have rough surface and extensive inner voids,the crushing ratio is positively related to the open void ratio,and their L.A.abrasion loss value was less than 50.0%;the presence of fine aggregates can mitigate grain crushing.The modulus of subgrade reaction(K30)for stabilized fill first increases then decreases with the rising of mixing ratio,which coincides with the transition mode of three soil structures,namely,fine-graded,stone matrix,and open-graded types.The stabilized soils with volumetric mixing ratio of 4∶1~2∶1 can be classified as a stone matrix type,with specimen at mixing ratio of 2∶1 achieving the best performance in practice.In summary,the particles of scoria are found to have desirable strength against grain crushing,and the performance of scoria–silty sand mixtures are much better than natural scoria;inter-particle void ratio is suggested to be taken as an indicator of quality assessment for subgrade compaction.