高能级强夯黄土地基振动衰减规律模型试验研究

Model Test Study on Vibration Attenuation Law of High Energy Dynamic Compaction Loess Foundation

为研究高能级强夯黄土地基的振动传播衰减规律,基于室内模型试验,通过布设竖直向、水平向及对角向三条测线,分别研究了夯击次数、含水率、夯击能、落距和锤径等参数变化对高能级强夯黄土地基的振动影响,并结合甘肃庆阳黄土高能级强夯加固项目现场振动测试结果,对比验证了室内模型的可靠性。研究结果表明:对于黄土地区,当达到一定夯击次数时,继续增加夯击次数无法进一步提升强夯加固效果,可根据所测得的振动加速度最大值判断最小振动安全距离,在计算振动安全距离时只需采用地表上的振动加速度;地基土含水率的改变对振动加速度的影响较小,当含水率为最佳含水率时,振动加速度峰值较其他含水率地基略高,衰减幅度略大,加固范围略广;能级的改变对振动加速度的变化影响较大,能级越大,振动越强烈,影响范围越广;“轻锤高落”与“重锤低落”产生的振动衰减速率相近,但“重锤低落”加固深度更深,影响范围更广,实际工程应优选“重锤低落”;相较于小锤径夯锤,采用大锤径夯锤的加固深度稍浅,地表振动影响范围更广,实际工程应优选小锤径夯锤;模型试验与现场监测数据拟合的振动加速度衰减曲线可较好的衔接,证明了室内试验结果的可靠性。

In order to study the vibration propagation attenuation law of high-energy dynamic compaction loess foundation,based on the laboratory model test,three measuring lines were arranged vertically,horizontally and diagonally to study the vibration impact of the changes of parameters such as compaction times,moisture content,compaction energy,falling distance and hammer diameter on the high-energy dynamic compaction loess foundation,and combined with the field vibration test results of Qingyang loess high-energy dynamic compaction reinforcement project in Gansu Province.The reliability of the indoor model was verified by comparison.The results show these as follows.For the loess area,when a certain number of tamping times are reached,increasing the tamping times can not further improve the dynamic consolidation effect.The minimum vibration safety distance can be judged according to the maximum value of the measured vibration acceleration,and only the vibration acceleration on the ground surface needs to be used to calculate the vibration safety distance.The change of moisture content of foundation soil has little effect on the vibration acceleration.When the moisture content is the best moisture content,the peak value of vibration acceleration is slightly higher than that of other moisture contents,the attenuation range is slightly larger,and the reinforcement range is slightly wider.The change of energy level has a great influence on the change of vibration acceleration.The larger the energy level is,the stronger the vibration is and the wider the influence range is.The vibration attenuation rate of“light hammer falling high”is similar to that of“heavy hammer falling low”,but the“heavy hammer falling low”has deeper reinforcement depth and wider influence range,so“heavy hammer falling low”should be preferred in actual projects.Compared with the small diameter rammer,the large diameter rammer has a shallower reinforcement depth and a wider impact range of surface vibration,so the small diameter rammer should be preferred in practical projects.The vibration acceleration attenuation curve fitted by model test and field monitoring data can be well connected,which proves the reliability of laboratory test results.