膨胀土裂隙演化规律及掺砂改良效果试验研究

Experimental Study on Crack Evolution Law of Expansive Soil and Improvement Effect of Sand Mixing

在荷载和气候环境作用下,不同种类的膨胀土裂隙开展程度不同.通过大尺寸泥浆试样开展一系列膨胀土干缩裂隙演化试验,并利用数字图像处理技术对裂隙演化的整个过程进行定量分析.试验对比研究了3种膨胀土的裂隙演化情况,并对其中裂隙开展程度最高的邯郸膨胀土进行风化砂改良.试验结果表明,3种地区的膨胀土裂隙演化过程可以分为4个阶段,分别是裂隙萌芽阶段、裂隙发育阶段、裂隙拓宽阶段和裂隙稳定阶段;3种不同地区膨胀土的裂隙形态有较大差异,合肥膨胀土裂隙密集且细长,邯郸膨胀土裂隙稀少且粗短,而广西膨胀土裂隙发育不良,存在未贯通裂隙;邯郸膨胀土存在“次生微裂隙”特性,会对土体造成进一步劣化;风化砂改良会加快邯郸膨胀土裂隙的发育,使其在更短的含水率区间内完成整个裂隙演化过程;风化砂改良对邯郸膨胀土的裂隙开展程度有显著的抑制作用,在掺砂率小于30%时,掺砂率越大,抑制效果越好.

Under the action of load and climate environment,different types of expansive soil cracks develop differently.Through large-size mud samples,a series of experiments on the evolution of dry shrinkage cracks in soil were carried out.The whole process of crack evolution was quantitatively analyzed by digital image processing technology.The evolution of cracks of three kinds expansive soil were studied.Improvement of expansive soil of the Handan,which has the highest degree of crack development,was performed with weathered sand.The experimental results showed that the crack evolution of expansive soil in three areas can be divided into four stages,named as crack germination stage,crack development stage,crack widening stage and crack stability stage.There were great differences in the crack morphology of expansive soils in three different areas.The cracks of Hefei expansive soil were dense and slender,the cracks of Handan expansive soil were rare and short,the cracks of Guangxi expansive soil were poorly developed with unpenetrated cracks.Handan expansive soil had the characteristic of“secondary micro-cracks”,which caused a further damage to the soil.The improvement by weathered sand accelerated the development of cracks in Handan expansive soil by completing the whole process of crack evolution in a shorter water content interval.The development of cracks in Handan expansive soil was obviously reduced by the improvement with weathered sand.When the sand mixing rate was less than 30%,the greater the sand rate,the better the inhibition effect.