Numerical simulation of backfilling behavior of boreholes

Abstract

The objective of this study is to investigate a backfilling process that can achieve uniform strength development in the depth direction of boreholes created when existing piles are removed. Failure to backfill these boreholes with a suitable filler material can lead to ground failures, such as soil settlement and the displacement or tilting of subsequent piles.Commonly used fillers include bentonite-mixed cement slurry, liquefied stabilized soil, and sandy soil. However, variations in strength development have been observed in the upper, middle, and lower sections of boreholes despite the mixing and filling of these fillers. In this study, the behavior of filler particles injected into boreholes, where mud (muddy water) due to drilling has accumulated, was visualized and quantitatively evaluated using an MPS-CAE analysis. The results revealed that higher density, viscosity, and the injection flow rate of the filler led to higher filling rates. This suggests that a complete replacement method using a filler with high density, high viscosity, and a high injection flow rate is effective for addressing the limitations of the widely used method of mixing muddy water and a filler. It is important to note that achieving uniform strength development throughout all sections of the boreholes is crucial for preventing ground failures.Based on the findings, it can be concluded that a backfilling process employing a complete replacement method with a high-density, high-viscosity filler and a high injection flow rate is effective for ensuring uniform strength development in the depth direction of boreholes.

Keywords

• Borehole
• Filler
• MPS-CAE analysis
• Muddy water
• Replacement