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使用不同初始状态的压实膨胀土,笔者在单轴固结仪上开展了不同加载路径下的吸湿变形试验。初始状态由含水率和孔隙比控制;加载路径分为两种:1无荷状态下浸水吸湿→加载压缩→卸载回弹;2加载压缩→浸水吸湿→卸载回弹。结合膨胀土双孔隙结构模型分析,得到以下结论:(1)压实膨胀土的自由膨胀变形会明显地随着初始含水率、孔隙比的降低而增大;(2)应力状态对压实膨胀土浸水吸湿变形特征有很大影响:无荷状态下浸水吸湿表现出明显的膨胀,而当上覆荷载较大时(本文为200 k Pa),则表现出明显的湿陷(压缩)变形;(3)两种加载路径下,初始含水率对膨胀土的吸湿变形都有显著的影响,初始含水率越小,浸水后变形(膨胀或压缩)量都越大;初始孔隙比对无荷状态下吸湿后膨胀土的压缩指数和回弹指数影响很小;(4)膨胀土双孔结构中,“团粒结构”的吸力(含水率)状态会对“宏观孔隙”的变形产生较大影响,吸湿过程中吸力增量越大,宏观孔隙的变形越大。
Using different initial state of compacted expansive soil, the author carried out the hygroscopic deformation test under different loading paths on a single shaft consolidation instrument. The initial state is controlled by the water content and the void ratio. The loading path is divided into two types: 1, moisture absorption under no load → loading compression → unloading rebound; 2 loading compression → water absorption → unloading rebound. Combined with the analysis of the double-porosity structure model of expansive soil, the following conclusions are obtained: (1) The free-swelling deformation of compacted expansive soil obviously increases with the decrease of initial water content and void ratio; (2) The hygroscopic deformation characteristics of soil immersion water have a great influence. Under the condition of no load, the hygroscopicity of the immersion water shows obvious expansion, while when the overburden load is large (200 kPa in this paper), it shows obvious collapse (compression) deformation; (3) Under the two loading paths, the initial water content has a significant effect on the hygroscopic deformation of the expansive soil. The smaller the initial water content, the greater the amount of deformation (expansion or compression) The compressive index and the rebound index of the expansive soil under hygroscopicity are small; (4) In the double-hole structure of expansive soil, the state of suction (water content) of the “aggregate structure” will produce the deformation of the “macropore” Greater impact, the greater the suction increase during the moisture absorption, the greater the deformation of the macro-pore.