自然蒸发条件下非饱和弱膨胀土裂隙演化规律试验研究

Experimental study on cracks evolution laws of non-saturated weak expansive soil under natural evaporation

本文对安徽沿江高速公路在建地区的弱膨胀土开展了干湿循环作用下的裂隙演化规律室内试验研究。采用IPP图像处理技术并结合图像矢量化技术对所获得的裂隙图像进行处理,通过提取试样面积、裂隙条数、裂隙总长度、裂隙面积等度量参数,分析了单条裂隙长度随含水率的变化关系,并以裂隙面积率及平均宽度等量化指标揭示了干湿循环过程中土体的裂隙演化规律。试验分析结果表明:试样在非饱和状态下的首次脱湿过程中,随含水率的降低只发生体积收缩,不产生裂隙,且试样的面积与含水率呈线性相关关系;随干湿循环次数的增加,裂隙条数、裂隙总长度、裂隙面积率增加,但裂隙宽度到第3次干湿循环时增幅较小;试样表面裂隙的单条裂隙长度与含水率的关系可以用Boltzmann生长曲线模型进行描述。

An experimental study on the evolution laws of cracks under the drying-wetting cycles is conducted on the weak expansive soil in the area along the Yangtze River in Anhui Province.The IPP image processing technique combined with image vectorization technique are used to process the obtained crack images,and the measurement parameters such as the specimen area,amounts of cracks,total crack length,and crack area are extracted effectively.The evolution laws of cracks in the soil during the drying-wetting cycles are analyzed by using quantification indicators such as cracks area ratio and average width,and the change law of single crack length with water content is also analyzed.The experimental study results prove that:In the first desorption process of the sample at the non-saturated state,only the volume contraction occurs with the decrease of the moisture content,no cracks are generated,and the area of the sample is linearly related to the moisture content.With the increase in the number of drying-wetting cycles,the amounts of cracks,the total length of cracks and the area ratio of cracks increase,but the width of cracks increases smaller to the third wetting-drying cycle.The crack system on the specimen surface is a typical bifurcation crack network.The relationship between the length of a single crack and the water content can be described by using the Boltzmann growth curve model.