基于分形理论的改良膨胀土龟裂发展规律探究

Development Law of Improved Expansive Soil Cracks Based on Fractal Theory

为探究改良膨胀土龟裂发展规律,通过石灰改良膨胀土的室内龟裂试验,基于分形理论,采用Matlab编程技术对膨胀土干缩裂隙图像进行数字化,并对裂隙表面结构特征进行定量统计与分析。结果表明,膨胀土的龟裂发展规律主要由基质吸力引起的应力场控制;不同石灰掺量的改良膨胀土在脱湿过程中裂隙率均先迅速增大,在塑限含水率附近达到峰值之后开始缓慢减小,最终在缩限含水率附近趋于稳定;经过石灰改良后的膨胀土裂隙率峰值出现较早,随着石灰掺量的增加峰值对应的含水率逐步减小,同时裂隙率峰值和残余值有明显的减小,当石灰掺量超过6%时改良效果不再随石灰掺量的增多而增强;可利用膨胀土裂隙率与表面的分形维数的关系估算膨胀土的裂隙率。

In order to explore the development law of the improved expansive soil, after designing indoor cracking ex- periments on lime-treated expansive soil, fractal theory was sued to explore the development law of improved expansive soil cracks. The Matlab programming technique was applied to digitalize cracked image of dry shrinkage expansive soil. And then the structural characteristics of crack surface was quantitatively analyzed. The results show that the develop- ment law of expansive soil cracks is mainly controlled by the stress field of matric suction~ The crack ratio of lime-treated expansive soil with different lime dosage in the process of drying first increased rapidly, and reached the peak value near the plastic limit water content, then began to slowly decrease and finally stabilized near the shrinkage limit water content; The crack ratio peak of lime-treated expansive soil appeared earlier. With the increase of the amount of lime, the peak moisture decreased gradually, and the peak of crack ratio and residual values were reduced. With the increase of more than 6% lime, improved effect is no longer enhanced with the amount of lime increasing. The crack ration of expansive soil can be estimated by the relationship between expansive soil crack ratio and fractal dimension.