Mechanism and Numerical Simulation of Drill Cuttings Transportation by Mud for Super-Long Bored Piles

Drilling cuttings in super-long bored pile holes tend to accumulate at the base, potentially reducing the pile’s bearing capacity if not effectively removed. This study presents a theoretical analysis of the settling velocity of drilling cuttings and the return velocity of mud in super-long pile holes. In addition, it proposes a method for determining the upward return of drilling cuttings during the positive and reverse circulation hole cleaning. The effects of various drill pipe rpm, mud inlet velocities, particle diameters, mud densities, and mud viscosities on the cuttings carrying performance of mud were investigated using the Ansys Fluent fluid simulation software. The results indicated that as the mud viscosity increased, the sedimentation rate of the drilling cuttings decreased, leading to a more effective mud carrying effect. The mud density was adjusted dynamically based on actual working site conditions. Increasing the diameter of the drilling cuttings particles did not promote effective cuttings carrying by the mud. However, increasing the drill pipe rpm, mud inlet velocity, density, and viscosity could enhance the cuttings carrying effect. These findings provide valuable theoretical guidance for mud circulation hole cleaning in the construction of super-long bored piles.