Influence of displacement piles on surrounding soil and nearby piles: a case study

For a large construction project in the greater Zug area (Switzerland), four maintained load axial pile loading test were
performed on 600 und 700 mm diameter, 45 m long full displacement piles. The maximum test load was around
7800 kN. All test pile rebar cages were fitted with fiber-optic distributed sensing temperature and strain sensors,
allowing thermal integrity profiling of the test piles and the measurement of residual load. Because of the large pile
diameter and nearby sensitive infrastructure, pile installation was accompanied by a comprehensive monitoring of free
field soil displacement and heave. Pile installation monitoring comprised ten purpose built push in soil extensometers
to measure vertical soil heave at various depths, total station measurements and precision levelling for measuring
surface displacement and heave, and measurement of excess pore water pressures during installation. The results of
heave and lateral displacements are accordingly calculated by Cavity Expansion (CE) and Shallow Strain Path Method
(SSPM) and modifying factors are recommended to improve predictions with SSPM that can take into account soil
compressibility for non-homogeneous, layered soils.