Abstract:
A Pressure Grouted Displacement Helical Pile (PGDHP) combines the advantages of non-displacement helical piles with increased bearing capacities of displacement piles, through forced ground improvement as part of the installation process. Ground improvement from deep foundations is mainly the product of lateral soil displacement or cohesion around an expansive cavity (grout cavity radius) or displacement zone. In both cases, the induced radial stresses can yield measurable soil densification and post-installation strength. Non-displacement piles, such as helical piles, do not yield the same degree of ground improvements to improve capacity, while displacement piles, such as precast concrete, or friction piles, such as Auger-Cast-In-Place piles do not generate the maximum soil-structure bonding capacity; thus the true soil capacity is not actualized resulting in increased pile characteristics (length, diameter, shape, etc.) to improve the overall bearing capacity.  In this paper, we investigate the effects of the induced lateral grout pressures during PGDHP installation, using cone penetrometer tests (CPT), on nearby soil fabric and induced excess pore pressures, ru, to quantify the ground improvement potential, both positive and negative. We also discuss the design and bearing capacity of these piles through comparative load test results in soft clays and highly expansive Yazoo Clay. In addition to the design and performance characteristics, this paper discusses the potential for improved QC, installation reliability, schedule reductions, and the ability to rapidly transition this technology to the wider industrial market. A Pressure Grouted Displacement Helical Pile (PGDHP) combines the advantages of non-displacement helical anchors with increased bearing capacities of displacement piles, through forced ground improvement as part of the installation process. Ground improvement from deep foundations is mainly the product of lateral soil displacement or cohesion around an expansive cavity (grout cavity radius) or displacement zone. In both cases, the induced radial stresses can yield measurable soil densification and post-installation strength. Non-displacement piles, such as helical anchor piles, do not yield the same degree of ground improvements to improve capacity, while displacement piles, such as precast concrete, or friction piles, such as Auger-Cast-In-Place piles do not generate the maximum soil-structure bonding capacity; thus the true soil capacity is not actualized resulting in increased pile characteristics (length, diameter, shape, etc.) to improve the overall bearing capacity.  In this paper, we investigate the effects of the induced lateral grout pressures during PGDHP installation, using cone penetrometer tests (CPT), on nearby soil fabric and induced excess pore pressures, ru, to quantify the ground improvement potential, both positive and negative. We also discuss the design and bearing capacity of these piles through comparative load test results in soft clays and highly expansive Yazoo Clay. In addition to the design and performance characteristics, this paper discusses the potential for improved QC, installation reliability, schedule reductions, and the ability to rapidly transition this technology to the wider industrial market.