溶蚀白云岩含水层注浆浆水两相运移特征LBM模拟研究

LBM Simulation on the Characteristics of Grout Water Two-phase Migration for Grouting in Dissolved Dolomite Aquifer

为了研究溶蚀白云岩含水层注浆过程中浆液驱替地下水效应,采用格子玻尔兹曼方法(LBM)研究了浆水两相运移规律。利用溶蚀白云岩岩样微纳米CT扫描图像,采用图像处理和阈值分割法识别其中的导水孔隙,运用三维重构技术获得溶蚀白云岩导水通道三维数字模型,为浆水两相流模拟提供复杂的几何文件。采用Shan-Chen模型描述浆水相互作用,基于溶蚀白云岩导水通道三维数字模型,采用LBM模拟了导水通道中浆水两相运移扩散特征,获得浆水两相饱和度演化规律。结果表明浆液扩散具有明显的选择性,连通性较好的孔隙为浆相主要运移通道,浆相最先达到出口。孔隙中部流速明显大于孔隙壁面附近流速,孔隙壁面摩擦对流体流动产生明显的抑制。被束缚的地下水降低了试样整体渗透性,后续浆液沿着已经驱替形成的优势通道运移扩散,降低了注浆驱水效率。孔隙壁面附近残余地下水将造成浆液固结体与孔隙壁面之间难以有效接触,是注浆堵水的薄弱部位。研究成果可为溶蚀白云岩注浆堵水提供技术参考。

To understand the effect of grout displacing water during rock grouting,the lattice Boltzmann method(LBM)was used to study the two-phase migration of grout and water.The image processing and threshold segmentation methods were utilized to identify the water conducting pores in the micro CT scanning images of dissolved dolomite rock sample.In addition,the three-dimensional digital model of the water conducting channel(WCC)for dissolved dolomite,which provides a geometry domain for grout water two-phase flow simulation,was obtained by three-dimensional reconstruction technology.Furtherly,the Shan-Chen model was used to describe the grout water interaction.Finally,based on the three-dimensional digital model of the WCC for dissolved dolomite,LBM was used to simulate grout water two phase migration and diffusion characteristics in WCC,and the evolution law of the grout water two phase saturation was obtained.Results show that the grout diffusion has obvious selectivity,and the pores with good connectivity are the main migration channels of the slurry phase,which first reaches the outlet.The flow velocity in the middle of the pore is significantly greater than that near the pore wall,and the pore wall friction has a significant inhibition on fluid flow.The bound groundwater reduces the overall permeability of the sample,and subsequent slurry migrates and diffuses along the dominant channel formed by displacement,reducing the efficiency of grouting for water displacement.Residual groundwater near the pore wall will cause grout stone and the pore wall can′t be consolidated effectively,which makes it a weak point for water sealing.The research results can provide technical reference for grouting to sealing the underground water in dissolved dolomite.