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Drilled displacement (DD) piles are cast-in-place piles that are formed with little or no soil removal, where the drilling tool displaces the soil radially outward into the formation, and can be used for ground improvement and/or for structural foundation systems. M-Piles are a type of steel DD pile that are constructed using a conventional rotary drill rig to supply downward thrust and rotation to install into the ground a permanent steel pipe connected to a sacrificial drill bit. Steel reinforcement and concrete can be placed within the open inner space of the steel shaft to provide additional rigidity and structural strength. There are many benefits to using DD piles, including minimal amount of soil removal, low ground vibrations during installation, larger unit values of side shear, and a stiffer pile response to loading. In general, the use of DD piles where the in-situ soils can be displaced and compacted. The use of M-Piles is applicable in very loose (i.e., running) -to-medium dense granular soils and in very soft-to-firm cohesive soils. The steel shaft provides support to the unstable soil so that the integrity of the supporting ground and the performance of the completed pile will not be compromised during installation. This paper will provide a general overview of steel DD piles (M-Piles), how a pile is constructed, applicability for use, and benefits afforded from using these piles. This paper will also present and discuss project conditions and test results via a mini case history where the M-Pile technique was implemented for the Bachelors Enlisted Quarters on Coronado Island in southern California, USA. |
