Abstract: Based on unsaturated soil mechanics theory, fluid mechanics theory and thermodynamics theory, the moisture migration mechanism of unsaturated soil was analyzed and one-dimensional unsteady flux equation of vapor was deduced. Through field investigation, laboratory and field test in strong evaporation region considering pavement blanketing effect, the spatial distribution characteristic of subgrade equilibrium moisture was probed. The correction coefficient of TMI-wPI matrix suction prediction model was proposed. The parameter of Fredlund & Xing model which reflected the single-valued function relation between the water content and matrix suction was calibrated to forecast subgrade equilibrium moisture. The results show that moisture migration is mainly affected by humidity gradient and temperature gradient. Because of pavement blanketing effect, subgrade interior moisture reaches its maximum in the range of 40~80 cm under the top of subgrade, with a decreasing trend upward or downward from this range; and its average moisture is much higher than that of the bare ground. The correction coefficient of forecast model which takes TMI and wPI as parameter is put forward to modify matrix suction, and error range is controlled within 20%. Fredlund -Xing model is widely applied and can be well characterized the correlation between subgrade humidity and matrix suction in strong evaporation region, and the correlation of parameters for the model fitting results can reach 0.84. The forecast results have high consistency with the test results.

Key words: road engineering, pavement blanketing effect, equilibrium moisture, correction factor, matric suction, prediction model

摘要： 以非饱和土力学理论、流体力学理论和热力学理论为基础，分析了非饱和土路基水汽迁移机理，推导了路基的一维非稳态的蒸汽通量方程；通过在受路面覆盖效应的强蒸发地区现场调研和室内外试验，探讨了该地区路基平衡湿度的空间分布特征；提出了TMI-wPI基质吸力预估模型的修正系数；标定了反映含水量与基质吸力单值函数关系的Fredlund & Xing模型参数，并对路基平衡湿度进行预估。结果表明：水汽迁移主要受湿度梯度和温度梯度的影响，由于路面覆盖效应的影响，路基内部湿度最大的是在路基顶面以下40～80 cm范围，从该范围向上或向下呈递减的趋势，且其平均含水量远高于裸露地面；提出引入TMI和wPI为参数的基质吸力预估模型修正系数，将误差范围控制在20%以内；Fredlund-Xing模型适用范围广，在考虑路面覆盖效应的强蒸发地区可较好地表征路基土湿度和基质吸力的相关关系，模型参数拟合结果相关性可达0.84，预估值与试验测试结果具有较高的一致性。

关键词: 道路工程, 路面覆盖效应, 平衡湿度, 修正系数, 基质吸力, 预估模型