Numerical Simulations of Soil Nailing Applied to Urban Excavations Considering the Effect of Post Grouting-Paper

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The paper presents a finite-element method for modeling soil-nailed retaining walls that accounts for sectorized post grouting, which strengthens the interaction between nails and surrounding soil. Conventional two-dimensional analyses typically assume uniform nail anchorage and may therefore fail to represent this effect. The proposed method follows established simulation procedures but treats each nail’s far end as immovable to represent its enhanced anchorage.<br /><br />The method was applied in PLAXIS 2D to an approximately 17.7 m-high retaining wall at Avenida Pujol in São Paulo. The wall was monitored using strain gauges. Simulations of conventional soil nailing predicted a maximum horizontal displacement of 43 mm (0.25% of wall height). When the enhanced soil–nail interaction associated with sectorized post grouting was included, the predicted maximum displacement fell to 2.1 mm (0.012% of wall height), closely matching the measured maximum of 1.1 mm (0.0063%).<br /><br />The results indicate that modeling enhanced anchorage is important for predicting the behavior of sectorized post-grouted soil-nailed walls. In this case, conventional modeling substantially overestimated movement, while the proposed approach produced predictions consistent with field measurements. The authors conclude that sectorized post grouting can enable stable urban excavations with very small wall displacements, although its effects remain difficult to quantify during preliminary design and require further validation across additional projects.

Keywords

soil-nailed retaining walls

finite-element method

sectorized post grouting

PLAXIS 2D

soil–nail interaction

retaining wall displacement

enhanced anchorage

urban excavation

Avenida Pujol

strain gauges