干湿循环机制下风化砂改良膨胀土的收缩特性

Shrinkage characteristics of expansive soil improved with weathered sand through wet-dry cycles

为研究风化砂改良膨胀土的收缩指标在干湿循环作用下的变化规律,采用收缩仪对经历不同干湿循环次数的掺砂改良膨胀土试样进行收缩试验,探究试样的线缩率、体缩率、收缩系数、缩限及胀缩总率在干湿循环作用下的变化特征及机理,建立不同干湿循环次数下掺砂改良膨胀土的缩限计算公式。试验结果表明：线缩率及体缩率随干湿循环次数的增加而逐渐减小,经过4次干湿循环作用后二者基本趋于稳定,且风化砂掺量由0增至20%时,线缩率及体缩率的降低幅度最大;随着干湿循环次数的增加,收缩指数呈指数函数降低,在4～5次干湿循环后,收缩系数基本趋于稳定,缩限随干湿循环次数的增加呈二次函数形式增加,且随着风化砂掺量的增加,干湿循环作用下缩限的增加幅度逐渐减小;胀缩总率随着干湿循环次数的增加先逐渐降低后趋于稳定,在干湿循环作用下通过掺入风化砂,可以有效降低土体的胀缩总率,并使之达到路基填土的标准。

Using the contractometer,shrinkage experiments were performed on expansive soil improved with weathered sand through wet-dry cycles to study the variation law of the shrinkage indexes of the improved expansive soil. Based on investigation of the changing characteristics and mechanism of the linear shrinkage rate,volumetric shrinkage rate,shrinkage coefficient,shrinkage limit,and expansion-shrinkage ratio of experimental specimens through wet-dry cycles,a formula for calculation of the shrinkage limit of the improved expansive soil with different numbers of wet-dry cycles was established. Some conclusions are drawn from the test results： the linear shrinkage rate and volumetric shrinkage rate gradually decreased with the increase of the number of wet-dry cycles,and tended to be stable after four wet-dry cycles,with maximal reductions occurring when the mixed amount of weathered sand increased from 0 to 20%; the shrinkage coefficient decreased exponentially with the increase of the number of wet-dry cycles,and tended to be constant after four or five wet-dry cycles; the shrinkage limit increased by a quadratic function with the numbers of wet-dry cycles,and the increment of the shrinkage limit gradually decreased with the increase of the mixed amount of weathered sand through wet-dry cycles; the expansion-shrinkageratio gradually decreased and tended to be stable with the increase of the number of wet-day cycles,and the value of the expansive soil decreased significantly by mixing with weathered sand,which allowed the expansive soil to meet the standard of embankment filling.