由于济南市泉域地层的特殊性和复杂性,第四纪沉积层虽然以黏土、粉质黏土为主,却表现出强富水、强透水的特征,在基坑工程施工中出现降水异常困难、结构渗漏水严重等一系列难题.为了明确济南红黏土层强透水的成因,从济南红黏土微观孔隙结构角度开展研究,首先对现场取样的原状红黏土开展基本物理特性试验,利用扫描电子显微镜 (SEM)获取红黏土的微观粒子排列方式.然后研发了基于计算机断层 (CT) 扫描的土体渗流装置,通过不同渗流阶段的CT扫描获取了红黏土内部孔隙三维结构并实现了孔隙水的流动可视化.最后建立孔隙网络模型(PNM)对渗流过程中土体内部孔隙和喉道的数量及体积占比进行了量化分析.结果表明:济南红黏土水平截面的颗粒搭接更为松散,孔隙结构以竖向发展为主,并存在孔径较大的联通通道;水在红黏土中优先沿着既有的大孔隙通道流动,并导致渗流通道扩张,土体内部孔径较大的联通孔道是导致土体强竖向渗透的主要原因.

Because of the particularity and complexity of Jinan spring area, the quaternary sedimentary layer is mainly composed of clay and silty clay, which has the characteristics of a strong permeability. In the construction of excavation, a series of problems such as the precipitation abnormal difficulties and the serious structural water seepage would occur. In order to reveal the causes of the strong permeability of Jinan red clay, a study from the perspective of micropore structure of Jinan red clay was conducted. First, the basic physical properties of the undisturbed red clay were tested, and the micro particle arrangement of the red clay was obtained by the scanning electron microscope (SEM). Then, a soil seepage device based on computed tomography (CT) was developed. The three-dimensional pore structure and the water flow visualization of the red clay in different seepage stages were obtained through CT scanning. Finally, a pore network model (PNM) was established to quantitatively analyze the number and the volume proportion of the pores and throats in the soil during the seepage process. The results show that the overlapping of particles in the horizontal section of Jinan red clay is more loose, and the pore structure is mainly developed vertically, with the existence of large connected channels. Water flows preferentially along the existing connected pore channel of the red clay, which leads to the expansion of the seepage channel. The connected channel with a large pore diameter is the main factor affecting the permeability of the soil.