Post-grouting is typically conducted shortly after the initial grout has set, often within 24 hours. This secondary grouting process serves to increase the effective pile diameter, leading to a substantial enhancement in the bearing capacity of minipiles. Furthermore, it improves the behavior of the surrounding soil by minimizing the disturbance caused during the initial installation. In essence, post-grouting strengthens the bond between soil and grout, optimizing skin friction and overall pile performance.
The post-grouting process involves inserting a tube with a bottom hole into the pile and injecting pressurized grout. Initially, the hardened grout confines the injected grout, preventing it from easily flowing away. However, the pressure eventually overcomes this resistance, rupturing the initial grout cover. The grout then penetrates the surrounding soil, seeking out softer regions and establishing an interlock with harder zones, thereby enhancing the pile’s stability.
To facilitate this rupture and ensure effective penetration, a maximum time limit is often imposed between the initial and post-grouting stages. This prevents the initial grout from gaining excessive strength, which could hinder the flow of the pressurized grout. By carefully controlling the timing, the detrimental effects of soil disturbance caused by casing installation and removal are significantly mitigated.
In summary, post-grouting is a strategic technique employed to optimize the performance of minipiles. By increasing the effective pile diameter, improving soil-grout interaction, and minimizing construction-induced disturbance, post-grouting ensures a robust and reliable foundation system.