原状花岗岩残积土大孔隙细观渗流场的格子Boltzmann模拟

选取福州某地原状花岗岩残积土作为研究对象,基于计算机断层扫描(CT)图像与格子Boltzmann方法,通过自编程序研究原状土样在大孔隙域中的细观渗流规律.结果表明:孔隙连通性好、孔径大的区域流体流速较大,且呈闪电状分布,而在孤立孔隙中流体无法流通;大孔隙渗流过程中存在明显的"指进效应",孔道中间流速最大,可达格子速度0.093 2,越靠近孔壁渗流速度越小,接近于0;大孔隙存在区域,格点流速分布呈单峰状或多峰状,而多个孔隙交汇区域内格点流速分布呈散点状,且无规律可寻.

CAI Peichen,QUE Yun,YANG Pengfei

In order to reveal the macropore meso-seepage mechanism of the undisturbed granite residual soil, the undisturbed granite residual soil in Fuzhou was selected as the research object. Based on the industrial CT scan image and the lattice Boltzmann method, the meso-seepage law of the undisturbed soil sample in the macroporous domain was studied by self-programming. The results showed that the LBM numerical method can effectively calculate and study the macroporous meso-seepage of the undisturbed soil, with an error of only 0.69%. Fluid particles flowed quickly in areas with good pore connectivity and large pore diameters, and the flow velocity was large, and they were distributed like lightning, but fluid cannot be circulated in some isolated large pores. The more the seepage velocity increased with time, the wider the distribution ranged, and all were lower than the initial flow velocity. In the process of macroporous seepage, there was a relatively obvious "finger-feeding effect". The flow velocity in the middle of the pore channel was the largest, which can reach a grid velocity of 0.0932. The closer to the pore wall, the smaller the seepage velocity was, which was close to 0. The result was consistent with the Poiseuille circular pipe flow theory. In the area where there were macropores, the grid point velocity distribution was single-peak or multi-peak. In the area where there were multiple macropores, the grid point velocity distribution was scattered and irregular.