microstructure and strength effect on bearing capacity of helical piles installed in golestan loess

Loess soils cover approximately 10% of the earth’s land surface. due to its honeycomb structure, this soil collapses under pressure and immediately settles when exposed to moisture. using moisture and loading conditions prior to construction can have positive effects on the geotechnical properties of the soil and help to reduce its settlement. this study aims to investigate the effect of different installation methods of helical piles on microstructure of loess soils. a total number of 16 full-scale helical piles including single helix and double helix piles with spacing to diameter ratios of 1.5 and 3 were installed via wet and dry installation methods. these 3-m-long piles were installed at the site of inche borun, golestan province, northeastern iran. pile static load tests were performed on a set of these piles to compare the effect of different installation methods. furthermore, the behavior of golestan loess was investigated by removing the soil in front of the other set of helical piles for element testing and sem imaging. the results suggested that the combination of compressive installation load and water pressure increases the shear strength parameters of golestan loess and accordingly, the bearing capacity of the installed helical piles.