A 93m long concrete box tunnel was jacked underneath a tollway to provide an additional roadway for the crossing traffic. The geotechnical conditions were predominantly residual soils, with stiffer soils found in the tunnel exit area. During half-way of the jacking process, the pavement above the tunnel showed some signs of heave, causing disruptions to the traffic. This paper reports the results of numerical analyses performed to examine the probable cause of the observed heave in order to avoid similar problems to occur in the future. Plane strain finite element models were developed to simulate the tunnel jacking process. Three aspects were evaluated, namely the effect of different excavated soil conditions inside the box tunnel, the effect of jacking displacement, and the effect of inclined stiffer soil. It was found that the ground surface heave is dependent on the amount of soils excavated inside the box tunnel, which is in turn related to the required jacking force. All these observations would suggest that, to minimize ground surface deformation, it is important to maintain a relatively low jacking force.