The Study On The Vibration Characteristics Of The Ground Surface In Improving Collapsible Loess Foundation With Dynamic Consolidation

The study at present on the vibration effect of Dynamic Consolidation(DC) mainly concentrates in analyzing the attenuation rule of the maximum vibration velocity, maximum vibration acceleration, maximum vibration displacement and vibration frequency, those are based on the vibration parameters of different radius. However, to the same tamping point, the vibration parameters are changing while the foundation is been consolidating, therefore it's necessary to study the vibration rule of the same tamping point in the tamping process. This paper analyzes the vibration rule of the same tamping point according to the local testing data of improving the collapsible loess foundation at Zhengzhou-Xian special passenger transport railway in Huayin City.Analyze the characteristics of the impact stress wave by impact theory, which presents index attenuation. According to the impact theory, educe the expression of the losing energy in the impacting process between tamper and soil mass. The losing energy is also used to consolidate the soil, the rest spreads abroad by wave.Based on the measured data, indicate that the vibration velocity and vibration acceleration attenuate with index grade, for the beginning, the value of the velocity is about 1/3 of the peak value, the attenuation range is 30%～60% ,the attenuation coefficient K=0.17,α=0.98. While the tamping number is up to some value, the vibration parameters become stable, which indicates the state of the soil is also stable, analyze the process by the rule of energy distribution in DC process. The frequency decreases when the distance increases, between 18Hz and 25Hz, but there is no difference at the same point, because frequency only indicates the characteristics of the soil mass at this point. According to the relation between vibration velocity and soil, present that inspecting the vibration velocity to identify the tamping number.The estimate of DC vibration influence on environment is by the nation demolition safety criterion and the earthquake intensity stable. The shock wave of the 2000kN·m energy level experimentation is safe to the general building beyond 50m. It is general to set up the vibration separation ditch to minish the influence of the DC vibration. The depth of the ditch can affect the vibration separation when the width can not.