深基坑爆破减振孔作用下围护桩结构减振效应研究

Effect of vibration damping of retaining pile structure under the action of damping holes of deep foundation blasting

基坑开挖爆破过程中振动荷载易对围护桩结构造成影响,临近围护桩结构预设爆破减振孔是重要控制手段。为评价爆破减振孔作用下围护桩结构的减振效应,以武汉地铁7号线巨龙大道站基坑爆破工程为背景,通过现场振动监测分析获得围护桩结构顶部振动速度;利用LS-DYNA软件建立基坑爆破数值计算模型,在结合现场监测数据验证计算模型及参数可靠性的基础上,采用控制变量法设计减振孔参数组合计算方案,计算分析各参数对减振效应的影响规律;提出围护桩结构稳定性的安全判据,在最优减振孔减振方案下,分析围护桩结构动力响应特征,并实现其现场工程应用检验。研究结果表明:减振孔的减振效应与减振孔的孔径、孔深、孔距和排数都存在相关性,其中减振孔的孔深、孔距和排数对减振效应的影响较大,而减振孔孔径对减振效应的影响较小;围护桩结构爆破振动速度安全判据为26.10 cm/s;以孔径为100 mm、间距为0.2 m、孔深为0.7 m的双排梅花型减振孔为优化设计方案,在此方案下,围护桩上最大振速为25.57 cm/s,小于爆破振速安全判据。

Vibration load in foundation excavation blasting process is easy to affect the retaining pile structure.Pre-set damping holes close to the surrounding pile structure is an important control measure.In order to evaluate the vibration damping effect of the retaining pile structure under the action of blasting damping holes,the vibration velocity of the top part of the retaining pile structure was obtained by on-site vibration monitoring analysis based on the Wuhan Metro Line 7 Julong Avenue Station pit blasting project.LS-DYNA software was used to establish the numerical calculation model of foundation pit blasting.On the basis of verifying the reliability of the calculation model and parameters by combining the field monitoring data,the calculation scheme of the combination of vibration damping hole parameters was designed by using the control variable method,and the influence law of each parameter on the vibration damping effect was calculated and analyzed.The safety criterion for the stability of the retaining pile structure was proposed.The dynamic response characteristics of the retaining pile structure was analyzed in the optimal damping hole damping scheme,and its on-site engineering application inspection was realized.The optimal damping hole damping scheme for the retaining pile structure was proposed,the dynamic response characteristics of the retaining pile structure under its action were analyzed,and its field engineering application test was realized.The results show that the vibration damping effect of vibration damping hole is related to the hole diameter,hole depth,hole spacing and number of rows of vibration damping hole,among which the hole depth,hole spacing and number of rows of vibration damping hole have greater effects on the vibration damping effect,while the vibration damping hole diameter has a smaller effect on the vibration damping effect.The safety criterion for blasting vibration velocity of the retaining pile structure is 26.10 cm/s.A double-row plum-shaped damping hole with a hole diameter of 100 mm,a spacing of 0.2 m and a hole depth of 0.7 m is used as the optimized design scheme.In this scheme,the maximum vibration velocity of the retaining pile is 25.57 cm/s,which is less than the safety criterion of blasting vibration velocity.