Abstract: Based on a highway widening project, using a “coordination and control of distortion” treatment thinking, the mechanism of composite foundation to prevent differential settlement are analyzed and a combined subgrade treatment Program of powder injection pile and geo-grid was proposed. Then its treatment results were evaluated. Dynamic monitoring results show that the differential settlement of cross section is 0.2 mm, and lateral displacement is 2 cm, which is in line with regulatory requirements. The results show that the widened roadbed deformation after treatment of composite foundation and the deformation difference between the new and old can reach a desired effect.

Key words: Subgrade widening, Composite foundation, Deformation, Treatment, Monitoring