Abstract: In order to get more traffic clearance under bridge during the road upgrading transformation, an internal and external reinforcement program was proposed to the underpass grade separation. The internal program was the soil reinforcement by the Soletanche method to active pressure soil and passive pressure soil of the abutment, and the external program was the anchored retaining wall by tie rods. Based on Abaqus6.10, the nonlinear FEM software, a 3D elastic-plastic numeric model was built to simulate the transformation process from buried abutment slope to anchored retaining wall. Two kinds of the construction processes were simulated, one was the slope soil excavation in layer vertically only and the other was in section horizontally and in layer vertically, and the soil reinforcement area was determined. Based on site detections to the top displacement and the bolt tension force of the retaining wall, stability analysis during the soil excavation and the wall construction were done, and the anchor pull test was carried out. The results indicated that the stability factor of the slope soil excavation program in layer vertically was 1.61, while the program in layer vertically and in section horizontally was 1.84, and the latter program was better. The top displacement of the wall increased mainly during the construction process, and the tension forces of the bolt did not change suddenly, and the wall and the soil behind the wall were stable. The soil reinforcement by the Soletanche method could enhance the soil shear strength and the resistance to deformation, and there was no collapse, fall, and slip during the construction process.

Key words: buried abutment, anchored retaining wall by tie rods, the Soletanche method, strength reduce method