Effect of Extending Loading Time Application on Pressuremeter Test Results

To assess the geotechnical properties of soil, the pressuremeter test has been widely employed since its introduction in 1955. This test is instrumental in determining key parameters such as the limit pressure (Pl), creep pressure (Pf), and modulus of deformation (EM). The fundamental principle of the test involves inserting a radially expandable probe into a borehole, which is subsequently expanded through incremental loading steps, with the resulting volume variation being measured. Traditionally, each loading step is maintained for a duration of 60 s according to European and American standards. In the scope of this study, an investigation was conducted to evaluate the impact of varying the loading time, specifically extending it from 60 to 120 s. These tests were carried out across diverse soil types at four sites in Tunisia. The findings revealed that beyond the 60-s loading period, the soils exhibited continued deformation. Notably, the limit pressure demonstrated a decrease with the prolonged loading time for most of the tested soils. This reduction, ranging from 2% to 30%, was particularly pronounced in soft and sandy clays. Furthermore, the creep pressure, representing the threshold of the soil’s pseudoelastic behavior, also experienced a decline with the increased loading time. The pressuremeter modulus EM2, which is obtained for a loading step of Δt = 120 s, exhibited a reduction across all soil types, with this reduction being more prominent in fine soils characterized by low consistency.