Abstract: The deep excavation activities will induce the change of pore water pressure and earth pressure fields in the surrounding soils, which might lead to the deformation of the surrounding soil. Therefore, the excavation has a significant impact on the surrounding environment, which will induce the excessive tilting, cracking and even structural damage of the pile supported bridge foundations. Currently, the analytical method for the effect of trench excavation on the adjacent pile supported bridge foundations is not clearly defined so that data collection of the construction monitoring becomes important. This paper presents a case history of a trench excavation near the pile supported bridge foundations in Yincheng of Ningbo soft soils. The effect of the trench excavation on the adjacent bridge foundations was simulated by the three dimensional finite element method using MIDAS GTS NX software and the numerical results were compared with the construction monitoring data. The results indicated that, inserting a hot rolled steel H beams into the soil-cement mixed columns formed by the Metro Jetting System (MJS) plus one row of reinforced concrete waler beam has a good performance in controlling the lateral deflection of the supporting structure and minimizing deformation of the adjacent soils. With the appropriate soil constitutive model and other numerical parameters, using the three-dimensional finite element method for simulating the effect of trench excavation on the adjacent bride structure is effective.

Key words: Under the Bridge, Trench Excavation, Deformation, Pile Supported Bridge Foundation, Numerical Simulation, Construction Monitoring