钻孔灌注桩在施工过程中防止泥浆护壁浆液的过度渗透扩散对维持桩孔稳定具有重要的意义。通过考虑非饱和土体渗透系数与浆体黏性的变化规律，假设桩孔底部渗透形状为碗状渗透，建立了浆体渗透扩散模型，同时基于多孔介质流体力学原理，得到了浆体渗透扩散距离的解析公式。然后对浆体渗透扩散模型进行对比验证。最后根据工程实际分析浆体渗透扩散模型的变化规律。研究表明，球状假设的扩散距离是碗状假设的2.7倍。桩孔半径由0.1 m变化到1.0 m，其渗透范围增大了2.2 ~ 2.6倍。中粗砂的含水率大于24%或基质吸力小于6 kPa时，非饱和性对渗透范围的影响在10%以下。当浆体初始黏度n_p0 ≤25 mPa·s时，可增加浆体初始黏度n_p0以控制浆体在土层中的扩散范围。此外根据不同地层的类型提出了其适用的浆体参数与浆体种类。研究结果可为控制泥浆渗透范围提供理论依据，对工程实际有指导意义。

During the construction process of bored pile, it is significant to prevent excessive infiltration and diffusion of slurry against the wall protection to maintain the stability of the pile hole. First, by considering the variation of permeability coefficient of unsaturated soil and the viscosity of slurry, the infiltration shape at the bottom of the pile hole was assumed to be bowl-shaped and a model for slurry infiltration and diffusion was established. Based on the principles of fluid mechanics in porous media, an analytical formula for the diffusion distance of the slurry was obtained. The slurry infiltration and diffusion model was then compared and validated. The results shows that the diffusion distance assumed to be spherical is 2.7 times that assumed to be bowl-shaped. As the pile hole radius varies from 0.1 m to 1.0 m, the infiltration range increases by 2.2 to 2.6 times. When the moisture content of medium-coarse sand is greater than 24% or the matrix suction is less than 6 kPa, the effect of unsaturation on the infiltration range is less than 10%. For slurry initial viscosity n_p0 ≤25 mPa·s, increasing the initial viscosity n_p0 can control the diffusion range of the slurry in the soil layers. Furthermore, suitable slurry parameters and types are proposed based on different types of strata. The findings of this study can provide a theoretical basis for controlling the infiltration range of slurry and have practical implications for engineering projects.