Measured and Predicted Response of a New Jetted and Grouted Precast Pile with Membranes in Cohesionless Soils

With increased urbanization, deep foundation (bridges, signage, walls, etc.) selection is moving toward the minimization of disturbance and installation time, as well as addressing quality control and assurance issues. Unfortunately, many types of deep foundations involve noise and vibration during installation (e.g., driven piles) or integrity and reduced resistance issues (e.g., drilled shafts, both conventional and post grouted tip, continuous flight auger piles). This paper presents a new foundation type, a jetted and grouted precast pile, which uses the advantages of several proven deep foundation installation techniques. The installation of the new pile is comprised of three distinct phases: (1) pressurized water-jetting of a precast pile into the ground; (2) side grouting of the pile; and (3) tip grouting. The pile has two separate side grouting zones, each with its own grout delivery system. Each grout zone is covered with a semirigid membrane, which results in radial expansion of the soil during side grouting and horizontal orientation of the major principal stress. Small-scale testing revealed excellent bonding between the pile and the grout, as well as improved mobilized pile-soil skin and tip resistance. Both experimental and FEM modeling of the grouting and axial loading were performed on various sized jetted and grouted precast piles in cohesionless soil. On the basis of this study, a methodology that predicts expected grout pressures during grouting, unit side and tip resistance, and the load-displacement response of a pile in cohesionless soil is proposed. Further testing and research is required to validate the proposed methodology before it can be implemented in practical situations.