Behaviour of Geogrid Reinforced Abutments on Soft Soil

Abstract

The behaviour of embankments on soft soils is a complex problem, particularly when the substitution of the soft material is not cost effective. In this case, the use of geosynthetics may be a feasible and economical solution for the stabilization of the embankment and reduction of the effects of differential settlements. This paper shows an investigation on the use of geogrid reinforcement in combination with pre-fabricated vertical drains (PVD) to accelerate soft soil consolidation in abutments for the duplication of the BR-101 highway, in Brazil. The instrumentation of bridge abutments included inclinometers, settlement and horizontal displacement plates, full-profile settlement gauges and piezometers, as well as strain gauges in the reinforcement layer. The results obtained showed that one of the abutments almost collapsed due to wrong construction practice and reinforcement specification. Insufficient reinforcement tensile force mobilization along the embankment transverse direction combined with wrong reinforcement orientation yielded to large embankment displacements and the initiation of failure. This failure mechanism could have been predicted with the use of current slope stability analysis for this type of problem. The results also showed the beneficial effect of the reinforcement for the stability of the embankment and reduction of lateral displacements of the abutments.