中文摘要：

采用压汞法对膨胀土干湿循环过程孔隙大小分布的演化规律进行了试验研究,结果表明,随着循环次数的增加,膨胀土的总孔隙体积、孔隙率和平均孔径等微结构参数均递增;分析了试验结果产生偏差的原因,其一是干湿循环过程中膨胀土试样的体积收缩,其二是孔隙形状和测试压力有限的影响,在此基础上对试验数据进行了合理修正。结合毛细管模型,利用修正的孔径分布曲线推算了膨胀土干湿循环过程中的土-水特征曲线,并分析了干湿循环过程中基质吸力的变化规律：以含水率28%为分界点,含水率大于该值时基质吸力随循环次数N的增加而线性递增,含水率小于该值时基质吸力随循环次数N的增加而线性递减;在此基础上,建立了基质吸力与循环次数之间的关系,为解释膨胀土力学特性的干湿循环效应开辟了一条新途径。

英文摘要：

Mercury intrusion porosimetry（MIP） test is used to study the change of pore size distribution of expansive soil during wetting-drying cycle.It is found that the microstructural parameters of expansive soil are increasing with the increasing number of cycles,such as the total volume of the pores,the porosity and the average pore diameter.After theoretical analysis and contrast experiments,the cause of test result deviation mainly stemms from two respects： one is the volume shrinkage of expansive soil samples during the wetting-drying cycle;the second is the influence of pore shapes and limited test pressures.And a reasonable amendment is given to the test data.Furthermore,the soil-water characteristic curves（SWCC） of expansive soil during wetting-drying cycle are calculated through the modified pore size distribution curves which are obtained from MIP test.Finally,the change rule of matrix suction of expansive soil during wetting-drying cycle is studied to deduce the relationship between the matrix suction and number of cycles.The results show that the moisture content 28% is the critical point;when the moisture content is larger than the critical value,the matrix suction increases linearly with the increase of cycle number;when the moisture content is smaller than the critical value,those are on the contrary.The paper gives a new approach to explain the wetting-drying effect of expansive soil mechanical behaviors.