Mohammad Reza Mahini

Low bearing capacity and probable liquefaction are common soil problems in coastal areas, and diverse soil improvement methods are often considered as a remedy for such problems. Using micro pile is a popular soil improvement procedure which throughout cement grout is injected into the soil and improves its structural composition in order to tackle load bearing and liquefaction problems simultaneously. Since the soil’s mechanical and physical characteristics can considerably affect its seismic response, soil enhancement might result in positive contribution to the seismic behaviour of the structure. In this research the effect of micro pile on the shear wave velocity in the soil is investigated. To this end, the downhole test in a layered soil is simulated and verified as a 3D model in ABAQUS and the boundaries are modeled using infinite elements. Then, micro piles with different lengths, diameter and coverage areas are added to the model as beam elements, and the shear wave velocity is numerically determined. Comparing the shear wave velocities computed for the improved soil with that of the unreinforced soil reveals that micro piles can noticeably increase the shear wave velocity and alter the seismic category of soil as classified in seismic specifications. Among the studied parameters, increasing the area ratio, which is defined as the total area of micro piles divided by the improved soil area, has the most contribution to the seismic enhancement of soil and can increase the shear wave velocity up to 8.93 percent for the studied case.