微膨胀泥岩地基原位水分入渗响应特征试验研究

Experimental study on in-situ water infiltration response characteristics of slightly-expansive mudstone foundation

红层泥岩的膨胀性和水敏性对地区公路、高铁的建设和工后变形控制构成了长期潜在威胁。为此,依托甘肃兰州一红层泥岩路堑段,开展了微膨胀泥岩地基原位水分入渗响应特征试验,分析泥岩地基膨胀变形量、膨胀力和体积含水率时空演化规律,并讨论了室内试验和原位试验的差异性。研究结果表明:红层泥岩地基水分入渗形式包括裂隙流和孔隙流,水分场具有明显的时空分布不均匀性,岩体裂隙对渗流、膨胀具有促进作用。入渗过程中泥岩吸水膨胀具有显著的时效性,原位地基膨胀量和膨胀力均经历骤增、减速增长和缓慢增长阶段,并未能达到收敛,浸润峰后泥岩表面逐渐软化甚至泥化,会导致地基承载力下降。室内试验对原位泥岩的水分入渗响应特征反映有限。

The red bedded mudstone,known for its expansive and water-sensitive nature,poses a long-term potential threat to the construction and post-construction deformation control of regional highways and high-speed railroads.In this study,an in-situ water infiltration response characteristics test was conducted on slightly-expansive mudstone foundations using a red mudstone road cut in Lanzhou,Gansu Province.The test aimed to analyze the spatial and temporal evolution of swelling deformation volume,swelling force,and volumetric water content of the mudstone foundations,as well as to compare the differences between laboratory tests and in-situ tests.The results reveal that the water infiltration forms in the red mudstone foundation include fissure flow and pore flow.The distribution of water in the rock mass exhibits significant spatial and temporal heterogeneity,with rock mass fissures promoting seepage and expansion.During the infiltration process,the water absorption and expansion of the mudstone exhibit significant time dependence.The expansion amount and expansion force of the in-situ foundation experience stages of rapid increase,slow growth,and eventually fail to converge.After reaching the infiltration peak,the surface of the mudstone gradually softens or even turns into mud,leading to a decrease in the bearing capacity of foundation.Additionally,through the analysis of macroscopic expansion time history variation characteristics and microscopic pore structure distribution laws of indoor and in-situ mudstone,it is found that laboratory tests provide limited characterization of the water infiltration response characteristics of in-situ soil.