The analysis of the effect of reinforcement on the performance of fills spanning potential voids constitutes a complex interaction problem. Previously, various simplified analysis techniques have been developed -tension membrane, tension membrane with no arching, tension membrane with arching -all of which have limitations oncerning accuracy and validity. The paper presents a more sophisticated model using continuum methods. Results obtained from the various models are compared. It is concluded that for this type of problem the continuum method provides the most accurate solutions. The paper also presents a case study where this advanced analysis technique was used to model the effect of reinforcement on embankment performance for a highway constructed over karstic terrain in the North of England. Geosynthetic reinforcement was incorporated into the base of the embankment to prevent a atastrophic collapse should subsidence occur.