Mechanism Analysis Of The Methods For Treating Vehicle Bumping At Bridge Approach Built On Soft Foundation And Experimental Study

The soft soil is widely distributed in the east coastal area of Zhejiang province. The characteristic which the bearing of soft soil is weak and the settlement is obvious has the adverse influence of the normal operation on the traffic bridge structure for the area. It is theoretical value and engineering guiding significance how to process, analyze and appraise the different settlement and impact response between the road and the bridge structure built on the soft soil.The study puts forward the deep-seated concrete slab and EPS concrete replacement method on the background of the typical bridge approach with vehicle bumping problem built on soft foundation in country provincial highway. The field experimental research was carried out. The finite element numerical simulation analysis of the bridge approach with deep-seated concrete slab, the mechanism analysis of transitional slab, influencing factors and theoretical study show that there are the advantages of distributing the vehicle loads, decreasing the settlement difference and the processed structure wholeness are better for the bridge approach with deep-seated concrete slab.By virtue of test study on EPS concrete light filling materials for indoors mix proportions before the constructing, the recommended values of the normal strength is obtained. By the long-term observation of the field experiment and the finite element analysis on the soil elastic-plastic characteristics for the bridgehead settlement, gains the study on the law of the stress and deformation form of bridge approach filled with EPS concrete. Using the EPS concrete light filling materials can decrease the dead-weight obviously, reduce the soil foundation settlement and increase the stability of the roadbed; the soil lateral pressure has little broaching effect on original abutment, thus cost is reasonable, considering to recycle and use the waste for more environmental protection, this method is much economic and environmental protection.The deep-seated slab is simplified to the elastic foundation plate under bidirectional stress on the Winkler foundation. The analytical solution deflection and base reaction of the foundation plate with specific boundaries under uniform load are calculated by elastic foundation beam theory. The deep-seated slab is also simplified to the infinite Kirchhoff plate under the elastic medium of soil on the Kelvin foundation. The elastic medium of soil is simulated by Navier wave equation where the displacement field of soil is establish by Helmholtz vector decomposition.The corresponding expression of plate under moving harmonic point load is calculated by Fourier inverse transform.The structure system of superficial pavement slab at bridge approach is simplified to the model of semi-infinite thin plate on viscoelastic foundation. The sinusoidal half-wave impact load is described as the vehicle impact action on bridge approach. Combined with Fourier-Laplace transformation and inverse transformation, the superficial pavement slab's deflection of transient response under the vehicle impact load can be derived. For the further discussion, the structure system of superficial pavement slab at bridge approach is also simplified to the model of infinite thin plate on viscoelastic foundation under moving invariable load. The steady-state response of the superficial pavement slab at bridge approach under moving load, each uniformly distributed over four rectangular areas, is derived and parameter analysis is carried out.From the finite element dynamical analysis of bridge approach models with two kinds of,treatment methods, in which vehicle load is simplified to impact load, the results show that the bridge approach treated by the deep-seated concrete slab and EPS concrete exhibit good effect on vibration reduction and isolation. The analysis results of dynamic responses of the superficial pavement slab, transitional slab, subgrade and soil foundation provide evidence for the design and the maintenance of bridge approach. Therefore, the safety and comfortableness during the vehicle driving and service level of the bridge approach can improve.