Behavior of Nonwoven Geotextiles under Pumping Loads

Dynamic consolidation tests were carried out to simulate the pumping loads acting on road foundations where coarse aggregates are separated from fine subgrade soils by nonwoven geotextiles. The tests were performed in a cylindrical 108 mm diameter consolidation cell loaded at a frequency of 1 Hz, with vertical stresses oscillating between 12 and 48 kPa. Combinations involved two aggregates, two subgrade soils and five nonwoven needle-punched geotextiles. The pore pressure dissipation and the settlements of the soil/geotextile systems were recorded as a function of the number of cycles to evaluate the time for stabilization, t S . The amounts of subgrade particles trapped into the geotextiles and migrating into the aggregates were evaluated at the end of each test. The results disclosed that the systems were sensitive to the filtration opening size O 9 5 of the geotextiles and to the size of the aggregates. Although products with smaller O 9 5 adequately prevented piping into the subbase, entrapment of particles into the geotextile contributed to a 12 to 17% increase in their mass per unit area. The resulting reduction in porosity however, is not believed to reduce substantially the filter permeability. Finally, the larger aggregates were also associated with an increase in subgrade particle entrapment within the geotextile structure.