温度循环下压实粗粒盐渍土水盐迁移与变形响应

“一带一路”规划的高速铁路频繁穿梭于盐质荒漠区，沿线优质不含盐路基填料极其匮乏。为解决粗粒盐渍土填筑高速铁路路基面临的技术难题，结合伊朗德伊高铁建设，以现场粗粒盐渍土路基填料为对象，开展了温度循环下压实粗粒盐渍土水盐迁移与变形响应试验研究。结果表明，每次温度循环后温度波幅值由土层浅表向深层土体衰减传递，土体埋深越浅、恒温时间越长，温度波幅值越大；水盐均匀分布的压实粗粒盐渍土经历多次温度循环后逐渐演化成非均匀分布，水盐向土体表面迁移聚集，越靠近土体表面水盐增量越大；前5次温度循环中压实粗粒盐渍土产生了塑性盐胀或塑性融沉，随着温度循环次数增加，盐渍土塑性盐胀或塑性融沉显著减小甚至消失；盐渍土层上设置非盐渍土层具有迟滞盐分向上迁移和消能减胀作用，粗粒盐渍土构筑高速铁路路基宜采用结构分层技术，非盐渍土层设置厚度一般不宜小于当地温度辐射影响显著深度；粗粒盐渍土路基设计宜考虑多次温度循环后形成的水盐非均质分布及其可能诱发的盐胀与融沉增大效应，路基压实度不宜过高。研究成果将为盐渍土地区高速铁路路基工程建造起到示范参考作用。

Water and salt migration and deformation response of compacted coarse-grained saline soil under temperature cycle

The planned high-speed railway in the Belt and Road area will frequently shuttle through salt desert areas, and it is difficult to find high-quality subgrade filler without salt along high-speed railway. To solve the technical problems faced by filling high-speed railway subgrade with coarse-grained saline soil, combined with the construction of Tehran-Isfahan high-speed railway in Iran, taking the coarse-grained saline soil subgrade filler obtained from on-site as the object, the test on water and salt migration and deformation response of compacted coarse-grained saline soil under temperature cycle was carried out. The results show that after each temperature cycle, the temperature wave amplitude is attenuated from superficial soil layer to deep soil layer. The temperature wave amplitude on closer to the surface of soil layers increases with the longer constant temperature time. The compacted coarse-grained saline soil with uniform distribution of water and salt gradually evolves into a non-uniform distribution after repeated temperature cycles. Water and salt migrate to the surface of soil layers, and the closer the position to the soil surface, the greater the increment of water and salt. In the first five temperature cycles, the plastic salt swelling or plastic thawing subsidence appears on the compacted coarse-grained saline soil. With the increase in number of temperature cycles, the plastic salt swelling or plastic thawing subsidence of saline soil decreases significantly or even disappears. The non-salted soil layer resting on coarse-grained saline soil layer has the functions of delaying salt migration up to the surface of soil layers, energy dissipation and expansion reduction. The structural layering technology should be adopted for the construction of high-speed railway subgrade with coarse-grained saline soil. The thickness of non-salted soil layer should not be less than the depth that significantly affected by the local temperature radiation. In the design of coarse-grained saline soil subgrade, the heterogeneous distribution of water and salt formed after repeated temperature cycles and the possible increase effect of salt swelling and thawing subsidence should be considered, and the degree of compaction of coarse-grained saline soil subgrade should not be too large. The research results will play a demonstration and reference role for the construction of high-speed railway subgrade engineering in saline soil areas.