Experimental study on the law of water-heat movement of remolded unsaturated loess humidified by steam
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摘要: 为研究非饱和黄土中水蒸气的吸附与运移规律,采用水蒸气对非饱和黄土进行增湿,分析蒸汽压梯度、温度梯度和含水率梯度共同作用下非饱和黄土中水-热运移规律。研究结果表明:在非饱和黄土中,水蒸气和温度的扩散范围近似于一个椭球体。水蒸气在土体中运移时,蒸汽压力沿径向逐渐消散,蒸汽运移速率减缓,土体含水率和温度也逐步降低;当蒸汽气压为0.1 MPa,温度为145 ℃,通气6.5 h后,水蒸气最大增湿半径为80 cm,横向、纵向有效增湿半径分别为60和70 cm;在以通气点为圆心,横向40 cm,纵向50 cm的椭球体内,含水率在12%~17%间变化,接近土体的最优含水率17.08%,增湿效果较好;延长通气时间,增湿范围和增湿程度均将增大;水蒸气增湿时,液态水和气态水迁移共存,但在有效增湿范围内以气态水迁移为主。受到土颗粒的阻碍,沿径向水分运移速率逐渐减小,但温度传导系数在两阶段内接近一个定值。水蒸气增湿法作为土体增湿的新技术与新方法,具有诸多优点,在对土体增湿的工程实践和试验中有着广泛的应用前景。Abstract: In order to study the adsorption and migration of water vapor in remolded unsaturated loess, water vapor was used to humidify unsaturated loess, and the law of water-heat movement in remolded unsaturated loess
under vapor pressure gradient, temperature gradient and water content gradient was analyzed. The results show that the diffusion range of water vapor and temperature is similar to an ellipsoid in unsaturated loess. During the migration of water vapor, the water vapor pressure disappears along the radial direction, the vapor transport rate decreases, and the soil moisture content and temperature also reduce; when the vapor pressure is 0.1 MPa and the temperature is 145 ℃, the maximum humidification radius of water vapor is 80 cm, and the effective humidification radius in horizontal direction is 60 cm and that in vertical directions is 70 cm after 6.5 hours. In the ellipsoid with the point of ventilation as the center, with 40 cm in the horizontal direction and 50 cm in the longitudinal direction, the water content varies between 12% and 17%. The humidification effect is better, the moisture content close to the soil is 17.08% which is the optimum moisture content, the ventilation time is extended, and the humidification range and the humidification degree are increased; when the steam is humidifying, the migration of liquid water and the gaseous water coexist, but the migration of gaseous water is dominant within the effective humidification range. Obstructed by soil particles, the water transport rate decreases gradually along the radial direction, but the temperature conductivity is close to a fixed value in two stages; the steam humidification method is a new technology and a new method for soil humidification. The advantages have broad application prospects in the engineering practice and experiment of soil humidification. -
表 1 基本物理指标
Table 1. Indexes of loess properties
含水率/% 密度/(g·cm-3) 最优含水率/% 最大干密度/(g·cm-3) 液限/% 塑限/% 塑性指数 颗粒组成/% ≥0.075 mm 0.005~0.075 mm ≤0.005 mm 7.04 1.53 17.8 1.74 27.1 17.4 9.7 13 65 22 -
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