Study On Deep Artificial Vibration In Elastic Ground And Its Influence On Ground Vibration

In last years,due to rapid industrial development,urban construction scalewas expanding and deep foundation projects was increasing.At the same time,deep artificial vibration has become increasingly prominent,which gave detrimental effects on human's production and life.This paper based on the numerical simulation model by using FLAC3 D software,relying on The National Natural Science Foundation Project "Study on deep artificial vibration in saturated ground and vibration isolation measures ",research the vibration on the surface in elastic ground due to deep artificial vibrations.The relationships between the vibration and properties of ground soil,such as layer distribution,shear modulus,and Poisson's ratio etc.,and vibration source have been explored.Furthermore,the influence originated from the overlaying bedrock and the key factors that have significant impact on the vibration have been analyzed.(1)An elastic foundation model is established by using FLAC3 D software and a classic Lamb problem is calculated,which can verify the correctness of FLAC3 D dynamic analysis and viscous artificial boundaries.A model is established for a field vibration test,and the vibration condition of the ground surface is calculated by comparison with field test data,which verify the validity of the model once again.(2)A detail parametric study on the problem of deep artificial vibration was carried out based on a numerical model with cylindrical hole.The results showed that the vibration level of surface is reduced with the frequency increases.With the Poisson's ratio increases,vibration quantity increases first and then decreases,and this influence has the close relationship with the wavelength of P-wave and R-wave.When the shear modulus becomes larger,the vibration level rapid declines.The vibration level will become smaller with a larger hole depth.Hole diameter has less impact on surface vibration.Typically,the vertical vibrations is much violent than the horizontal one.Vertical vibration level gradually decays with the increasing of radial distance.Horizontal vibration is attenuation along the direction of away from the vibration source,and the maximum vibration quantity occurs in the vicinity of the x-axis near the origin,and the position gradually transfers to distance with the increase of frequency and diameter of cylindrical hole.Instead,the position gradually moves closer to the vibration source with the shear modulus and Poisson's ratio increases.Based on the foregoing calculation,the safety threshold of the vertical vibration is put forward.(3)Similar to the homogeneous foundation,the effect of ground vibration due to deep artificial vibrations in layered foundation is analyzed.The results indicated that ground vibration increase first,then decreases and increase afterwards with frequency increasing in the soft under the hard ground,and the position of the maximum vibration quantity appears more substantial shift to the distance,but on the hard ground under the soft,surface vibration level increases linearly with increasing frequency.Hole depth has a greater impact on surface vibrations,surface vibration significantly reduces with the hole depth increasing and has a brief increase when the bottom of hole near the interface between the hard and soft soil.When the diameter of the hole increases,ground vibration first increased and then decreased sharply,and the position which maximum vibration quantity occurs gradually transfer to distance.(4)The effect of ground vibration due to deep artificial vibrations in the foundationswith overlaying bedrock is analyzed.The results indicated that both vertical and horizontal increases with frequency increasing due to the rock surface reflection.Ground vibration has a larger fluctuation with Poisson's ratio increasing.With the hole depth increasing,the reflection of the underlying layer is also enhanced,thus causing the ground vibration decelerate attenuation then reverse to accelerate the increase.When the hole diameter increasing,surface vertical and horizontal vibration is greatly reduced.