Cast-in-Place Piles Using Toe-Grouting Cell: Application in Bolivian Rivers-Paper

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The paper describes the design and construction of post-grouted, cast-in-place piles for three railway bridges over the Piraí, Yapacaní, and Ichilo rivers in Bolivia. The foundations were built in predominantly clean alluvial sands, where conventional drilled-pile toe resistance is limited by uncertainty, soil disturbance, and debris at the base.<br /><br />The piles, 1,200 or 1,500 mm in diameter, were equipped with a steel grouting cell at the toe. As grout pressure rises, the cell pushes downward against the ground and upward against the pile, then allows grout to enter the soil below the pile base. Because the cell’s area is known, pressure provides an estimate of the applied toe force. The reaction mobilized along the shaft also gives a lower-bound estimate of shaft resistance. Monitoring pile-head and cell movements can make the process resemble a bi-directional loading test.<br /><br />Design calculations used established grouted-pile methods to estimate the required grouting pressures and check that shaft resistance would prevent excessive uplift. In an example, toe grouting allowed a 22 m pile to meet capacity requirements; a comparable ungrouted pile would have needed to be about 10 m longer. Across the project, grouted piles achieved toe resistances substantially above conventional AASHTO estimates, reducing pile lengths and, in some cases, avoiding the need for additional piles.<br /><br />Grouting pressure, volume, and flow were monitored, while pile movements were measured. Mobilized shaft resistance exceeded the design estimate for most piles, though uplift was generally limited. The authors note that the movement data were not sufficient to qualify as formal load tests and recommend real-time displacement sensors for future work. Overall, toe-grouting improved toe performance and construction confidence while delivering savings in foundation time and cost.

Keywords

post-grouted piles

cast-in-place piles

railway bridges

toe grouting

alluvial sands

pile foundation design

shaft resistance

grouting pressure

Bolivia

bi-directional load test