This ground improvement project required the installation of 2,540 stone columns, 25-feet deep and approximately 3.3 feet in diameter. Stone columns are a ground improvement method that involves replacing in-situ material with an aggregate such as ¾-inch crushed rock. This replacement process not only densifies the surrounding material through displacement, but also through settlement due to vibration. During an earthquake, seismic loading is resisted by the combination of stone and densified earth. Additionally, the increase in pore water pressure dissipates through the permeable stone columns, preventing liquefaction.
Six locations on this project had access challenges with existing roadways and rail lines, including one area directly between the North and Southbound traffic of Interstate 15. In some areas, stone columns were safely installed within 10 feet of active UTA and UP rail lines, as well as within 10 feet of Interstate 15 lanes. Increasing the difficulty of the project was a cold and snowy Utah winter. Despite these factors Malcolm Drilling was able to complete their work in all areas on or ahead of schedule.