超重力离心模型试验土体弹性波速监测与表征#br#

压电陶瓷传感器在岩土体弹性波速测试方面具有独特的优势，已在常重力工况下得到了较多的应用。文章针对离心机模型试验的超重力环境对弹性波速测试所提出的严苛要求，研发压电弯曲元和压电压缩元传感器及相应的弹性波速测试技术，主要包括传感器微型化和高频响性能设计，电磁屏蔽和防水接地技术，接收信号的快速叠加和带通滤波处理方法，以及时域初达波法确定接收信号到达时间等。在60g离心加速度下开展一组水平黄土场地的超重力模型试验，重现降雨入渗过程中模型场地土体的软化过程，并利用所研发的弯曲元和压缩元实时监测土体的剪切波速和压缩波速。结合TDR技术监测到的土体密实度，获得土体剪切模量、杨氏模量和泊松比等弹性参数随着土体软化的变化过程，实现超重力环境下模型土体弹性参数的实时监测与表征。

Measurement and characterization of elastic wave velocity of #br# soil in hypergravity centrifuge model test

Piezoelectric sensors used in geotechnical engineering have advantages in measuring elastic wave velocity of soil under gravity, however the measurement of elastic wave velocity of soil under hypergravity condition in centrifuge model test is still very challenging.In this study, high-performance mini-type piezoelectric bender elements and bending disks are designed.Measurement method for elastic wave velocities in centrifuge model tests is proposed, in which many methods are used, such as electro-magnetic coating, water proofing and grounding, fast staking and band-path filtering of received signal, and time-domain first-arrival method for travel time identification.A centrifuge model test of level loess ground under 60g was carried out to reproduce the soil softening process induced by rainfall infiltration, in which the shear wave velocity and compressive wave velocity were monitored simutaneously.By combing the estimation of soil density from TDR measurement, the variation of shear modulus, Young's modulus and Poisson's ratio of the soil in the model were estimated according to the elastic theory.The proposed techniques enable the real-time measurement and characterization of elastic parameters of soils in centrifuge model tests under hypergravity environment.