Numerical analysis of geosynthetic-bridged and drilled shafts-supported embankments over large sinkholes

ABSTRACT: This paper proposes a method to remedy sinkhole problems in highway projects by placing a geosynthetic layer over the drilled shaft walls to support the embankments. Two calibrations were first conducted to verify the numerical model using FLAC^2D for this kind of problem. One calibration was based on a field study of a gesosynthetic-reinforced, column-supported embankment. The second calibration was based on a full-scale geosynthetic-bridging over void test. A baseline case representing typical material properties and model geometry in real projects was selected and analyzed, which included a 5-m high embankment over a 20-m wide void supported by a geosynthetic layer over drilled shafts at 3-m spacing. The analysis included the settlement, the tension in the geosynthetic layer, and the total axial force in the shafts. Settlements at the crest and base of the embankment were calculated to evaluate the performance of this embankment system. The numerical results indicate that higher tension in the geosynthetic layer was located at the edges of the shafts. Total axial force in the shafts was used to compute a soil arching ratio. Three key parameters were investigated in a parametric study including the spacing of the shaft walls, the void width, and tensile stiffness of the geosynthetic layer. The parametric study shows that the spacing of the shaft walls greatly influences the performance of the embankment. The void width has limited influence if the drilled shafts are uniformly distributed in the void. The tensile stiffness of the geosynthetic has a more significant influence on the settlement at the base of the embankment than that on the crest.