Experimental Research on Macro and Micro Mechanical Characteristics of Photovoltaic Support Steel Piles

Solar photovoltaic power generation is one of the main development directions of clean energy， so the selection of photovoltaic support foundation is particularly important. Sectional steel piles have been widely used in photovoltaic power generation projects in desert areas because of their strong penetration capacity， light weight and convenient transportation. Considering the stress characteristics of photovoltaic supports， the frictional characteristics of pile-soil interface under different compactness and confining pressures were revealed through large-scale direct shear tests. Based on the results of large-scale direct shear tests， the pull-out tests of sectional steel piles were carried out to explore the bearing characteristics and internal force distribution of piles under different pile types and confining pressures. The research results showed that the shear process of the contact surface between the steel pile and sandy soil presented softening characteristics， and the friction angle between the steel pile and its surrounding soil was greater than the soil’s internal friction angle， and became more obvious with the increase of the compactness of the soil； there was a good correlation between the ultimate lateral friction of sectional steel piles and the relative displacement of soil around the piles， and the peak strength occurred at 8 to 11 mm relative displacement in sandy soil. The results of pull-out tests presented that the section shape of sectional steel piles had significant influence on its bearing characteristics， the bearing capacity of H-shaped piles was higher than those of C-shaped piles and channel shaped piles， and the friction resistance at the inside web of H-shaped piles was greater than the outside flange.