基于路基基层剪切波速试验的弯曲元优化设计

为了解决高速公路路基基层剪切模量长期监测的技术难题，利用压电陶瓷材料弯曲元，设计适用于香丽高速公路路基基层水平方向上剪切波激发与接收装置。选用级配符合高速公路G-A-4级配的砂砾石土进行一系列试验，以优化弯曲元传感器的钢框架尺寸和网盖设计。研究结果表明:(1) 钢框架宽度对接收信号幅值或压力波传播无显著影响，考虑框架刚度的影响，钢框架宽度设计为0.3 m。 (2) 钢框架长度对接收信号幅值有显著影响，钢框架长度的最优设计为1.2 m。 (3) 比较六种网盖材料，因不锈钢具有良好的耐久性，并对接收信号幅值的影响相对较小，选用不锈钢网作为网盖材料。(4) 砂砾石土具有压硬性，提升土层围压，土层剪切模量随之增加，试验中弯曲元表现出剪切波速的增大, 表明弯曲元适用于砂砾石土层剪切模量的量化。研究成果为定量刻画路基基层刚度提供新的手段。

Optimal Design of Bender Element Based on Embankment Base Layer Shear Wave Velocity Test

To solve the technical problem of long-term monitoring of shear modulus of highway embankment base layer, based on the piezoceramic material bender element, design shear wave generated and received devices applied to the Shangri-La to Lijiang highway embankment base layer on the horizontal direction. A series of tests were conducted with sandy gravel soil whose gradation conforms to the highway G-A-4 gradation to optimize the design of steel frame dimensions and mesh cover of the bender element sensor. The results indicate: (1) The steel frame width does not have a significant effect on the received signal amplitude or p-wave transmission, and the final design of the steel frame width is 0.3 meter on the consideration of frame stiffness. (2) The steel frame length has a significant effect on the received signal amplitude, and the optimal design of the steel frame length is 1.2 meter. (3) By comparing six different mesh cover materials, stainless steel mesh is selected as the mesh cover material taking its excellent durability properties and relatively less influence on the received signal amplitude into consideration. (4) Because of the press-hard characteristic of the sandy gravel soil, an increase of confining pressure would increase the shear modulus of the soil. In the experiment, the bender element shows an increase in the shear wave velocity, which indicates that bender element is suitable for quantification of aggregate base layer stiffness. The research results provide a new method for quantitatively describing the stiffness of embankment base layer.