Study on Vibration Effect of Combined Heavy Tamping on Soft Soil Foundation in City
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摘要: 为研究组合锤法强夯振动对周边场地环境的影响，对南昌市某软土地基进行现场原位试验。考虑距强夯点的距离、振动方向及锤击次数的影响，在各监测点分别布置水平东西、南北向和竖向振动传感器。结果表明：采用组合锤法进行地基强夯施工时，场地竖向振动是需重点监测的内容，振动响应随监测点与强夯点距离的增大而减小；距强夯点50 m范围处地面振动速度衰减至0.2 cm/s以下，可根据地面振动速度确定安全施工范围；地面加速度受锤击次数的影响较大，且水平向加速度对锤击次数的敏感性略高于竖向，锤击次数对地面水平向振动的影响不可忽略；基于试验数据和波源振动理论建立的振动加速度衰减模型综合考虑了距强夯点的距离、振动方向和修正系数（锤击次数的影响），经算例验证具有较强的适用性，可为同类场地采用组合锤法强夯施工提供参考。Abstract: In order to study the vibration effect of composite hammer method on the surrounding environment and its influencing factors, a soft soil foundation in Nanchang was tested. In the test, the influence of different distance, vibration direction and hammer times from the tamping point is considered, and the horizontal east-west, north-south and vertical vibration sensors are arranged at each measuring point respectively.The results show that the vertical vibration of the site is the key content to be monitored during the dynamic compaction of foundation by the combined hammer method, and the vibration response decreases with the increase of the distance between the monitoring point and the hammer point.The vibration velocity of the ground out the 50 m range attenuates to less than 0.2 cm/s, and the safe construction range can be determined according to the vibration velocity of the ground.The ground acceleration is greatly affected by the number of hammer blows (the maximum increase is 61.0%), and the sensitivity of horizontal acceleration to the number of hammer blows is slightly higher than that of vertical. The impact of the number of rammers on the horizontal vibration of the ground cannot be ignored.The attenuation model of vibration acceleration based on test data and wave source vibration theory takes into account the influence of distance, vibration direction and correction coefficient (the number of hammer strikes), which is proved to have strong applicability by calculation examples, and provides a certain reference for similar sites using combined hammer method.
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图 2 监测点水平东西向加速度时程曲线与频谱曲线
Figure 2. Time history analysis curve and spectrum curve of horizontal east-west acceleration at different distances
图 3 监测点水平南北向加速度时程曲线与频谱曲线
Figure 3. Acceleration time history analysis curves of horizontal north-south direction at different distances
图 4 监测点竖向加速度时程曲线与频谱曲线
Figure 4. Acceleration time-history analysis curves and spectrum curves of vertical direction at different distances
图 5 监测点加速度峰值随距离衰减曲线
Figure 5. Attenuation curve of peak acceleration of monitoring points with distance
图 6 监测点竖向速度峰值随距离衰减曲线
Figure 6. Attenuation curve of peak vertical velocity of monitoring points with distance
表 1 监测点加速度峰值与速度峰值
Table 1. Peak acceleration and peak velocity at monitoring points
监测点 水平东西向 水平南北向 竖向 加速度峰值/cm·s−2 速度峰值/cm·s−1 加速度峰值/cm·s−2 速度峰值/cm·s−1 加速度峰值/cm·s−2 速度峰值/cm·s−1 15 m 99.9 2.5 74.1 2.8 139.1 3.1 30 m 58.9 1.8 71.6 2.0 99.5 2.6 50 m 7.2 0.3 27.1 0.4 7.5 2.0 100 m 5.9（剔除异常点） 0.1 2.4 0.1 2.6 0.3 
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表 2 衰减曲线回归分析结果
Table 2. Results of regression analysis of attenuation curveResults of regression analysis of attenuation curve
方向 加速度衰减公式 相关系数 水平东西向 ${A_x} = - 21.325 + 225.927\;5{ {\rm{e} }^{\left({ - 0.02\;9r/{r_{_0}}{\rm{} } } \right)} }$ 0.915 水平南北向 ${A_y} = 27.256 + 138.790\;3{ {\rm{e} }^{\left({ - 0.026\;3r/{r_{_0}}{\rm{} } } \right)} }$ 0.927 竖向 ${A_z} = 37.231 + 277.478\;4{ {\rm{e} }^{\left({ - 0.038\;0r/{r_{_0}} } \right)} }$ 0.935
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