Field Lateral Load Tests on Slope-Stabilization Grouted Pipe Pile Groups

A new type of slope-stabilization structure has been developed in recent years, which uses a grouted pipe pile group and pile-head connection beams to form a pile-soil frame structure. In this research, field lateral loading tests on one $2\times 5$ and two $3\times 5$ grouted steel-pipe pile groups were carried out at a highway slope-stabilization site. The tests simulated the performance of slope-stabilization pile groups subject to lateral soil movements caused by surcharge fill loading behind the pile groups. Through the measurements of pile and soil displacements, pile strains, and earth pressures, the loading behavior of these grouted steel-pipe pile groups was studied, taking the number of pile rows, row spacing, and pile spacing as variables. At the same pile spacing and row spacing, the maximum displacement of a $3\times 5$ pile group was only 35–55% of that of the $2\times 5$ pile group. The deformations of the soil between the piles were approximately the same as those of the piles. The earth pressure was the largest on the rear piles and smallest on the front piles. The maximum bending moment of the rear piles occurred near the pile head, while the maximum bending moments of the middle and front piles were near the sliding surface of the test slope.