土剪破坏次声监测试验研究

EXPERIMENTAL STUDY ON INFRASOUND MONITORING DURING SOIL SHEAR FAILURE

土质滑坡临滑会产生次声波,次声监测可以作为判断土质滑坡临滑的一种技术手段.在考虑到滑坡的力学方式是以剪切破坏为主的前提下,为了探明土质滑坡过程中的次声信号响应特征,设计了土体直剪实验次声-力-位移联合监测系统,开展了土体剪破坏次声监测试验,在次声事件自动拾取的基础上,结合黏性土渐进性破坏理论,分析了剪切过程中的微观声学机理,结果表明:(1)黏性土剪切破坏时发出的次声信号主要来源于弹性阶段中黏土颗粒的相互挤压、弹塑性阶段中以黏土胶体团粒本身的拉张破裂和应变软化阶段中土颗粒间的摩擦;(2)在土体剪切载荷的不同阶段,次声信号的幅值大小呈现出应变软化阶段<弹性阶段<弹塑性阶段的规律;(3)剪切力与次声信号之间存在较强的相关性,次声事件的峰值包络线与剪切力趋势线相当吻合,并且次声信号的均方功率峰值都在推力峰值之前,平均提前为22.95s.研究对进一步利用次声开展土质滑坡的监测和稳定性评价具有重要的理论参考价值.

When a soil landslide is near the landslide stage,infrasound waves are generated.Infrasound monitoring can beused as a technical means to determine whether a soil landslide is in the approaching stage Considering that the landslide’s mechanical method is mainly shear failure,in order to ascertain the response characteristics of infrasound signals during the process of soil landslides,a combined infrasound-force-displacement monitoring system for soil shear experiments was designed and an infrasound monitoring test for soil failure was carried out.Based on the automatic picking up of infrasound events,combined with the theory of progressive failure of cohesive soil,the micro-acoustic mechanism during the shearing process is analyzed.The results show that:(1)The infrasound signals emitted during shear failure of cohesive soil are mainly derived from three aspects:first,from the mutual compression of clay particles in the elastic phase,and then from the tensile fracture of clay colloidal particles in the elastic-plastic phase,finally,it comes from the friction between soil particles during strain softening.(2)The amplitude of the infrasound signal shows a certain regularity at different stages of soil shear loading.The amplitude of the infrasound signal during the elastoplastic phase is the largest.The amplitude of the infrasound signal during the strain softening phase is minimal.The amplitude of the infrasound signal corresponding to the elastic phase is between the elastoplastic phase and the strain softening phase(3)There is a strong correlation between the shear force and the infrasound signal.The peak envelope of the infrasound event matches the shear force trend line.At the same time,the mean square power peak of the infrasound signal is ahead of the thrust peak.The average time is 22.95 s.The research has important theoretical reference value for further using infrasound to carry out monitoring and stability evaluation of soil landslides.