Numerical Method To Analyze The Vibration Propagation Due To Rail Transit And The Isolation Vibration Effectiveness By Using Pile Rows As Well As The Corresponding Application

According to the evaluation method of environmental vibration induced by traffic loading formulated by the state regulation of "regional environmental criteria for vibration in urban construction" (GB10070-88), and based on the dynamic soil mechanics theory as well as considering the complex nature of the environmental vibration induced by traffic loading. The environmental vibration propagation and attenuation rule is analyzed with using the model of traffic load-railway track-saturated soil. Meanwhile, special attention is also paid to the study of the isolation vibration mechanism by using pile rows in this paper. The studies of the paper consist of the following parts:1) The physical mechanism of vibration propagation and attenuation is introduced briefly. Also, the main control parameters of vibration character are presented and the formula to calculate the ground vibration induced by track traffic is given.2) Considering the railway track as the elastic foundation beam and regarded the discrete support by concrete sleeper, the simplified model of the traffic load-train-railway track-soil foundation was established. Some scholars have studied the problem of environment vibration induced by traffic loading, however, the influence of pore water pressure without taking into account in their researches. Based on Biot's theory and using the Fourier transform, The time domain solutions for the half space are obtained, Consequently, the transmission and reflection matrices (TRM) method is used in solving the problem of environment vibration induced by traffic loading in the layered water-saturated poro-elastic half space. Furthermore, the effect of soil layer parameters on the vibration response of the ground, such as the speed of the train, infiltration coefficient, the porosity, the viscosity of a fluid, shear wave velocity and the layered saturated soils, is discussed in detail.3) The effect of vibration isolation by using pile rows embedded in a poroelastic half space is investigated with the semi-analytical methods. Taken the pile as 1-D bar, using Biot theory and Muki and Sternberg's method as well as the integral equation, the effect of isolation the vibration due to the moving loads by using pile rows embedded in a poroelastic half space is investigated in this study. The influences of the soil inhomogeneity, pile length, Young's modulus of the pile, the net spacing between two neighboring piles in a row are investigated by numerical simulation. Also, the influence of the number of pile rows and spacing between pile rows are examined. Comparison of our results with an existing result shows that our results are in a good agreement with the existing one. The semi-analytical nature of the proposed method avoids the discretization of the whole calculation domain which is necessary for finite element method, and thus it reduces the CPU time for the current problem substantially. So the proposed method is useful for the design of vibration isolation barriers and can be used to evaluate the effect of pile rows as barrier system for ground vibrations. Numerical results suggest that the pile length, the number of pile rows, the spacing between neighboring piles in each pile row and the stiffness of piles have significant influence on the vibration isolation effect of pile rows. While the spacing between the neighboring pile rows may have little influence on the vibration isolation effect. Numerical results of this study also show that speed of moving loads has an important impact on the isolation vibration effect of pile rows:the same pile rows can achieve better vibration isolation effect for lower speed loads than for higher speed loads. Moreover, for the same pile rows and the vibration source, the poroelastic medium often leads to a better vibration isolation effect than the single phase elastic medium does.