环境湿度可控的土体小应变刚度试验系统

Small-strain stiffness test system of soil under controllable environmental humidity

为研究脱湿过程中饱和度改变对土体小应变刚度的影响规律,自主研制了一套非饱和土小应变刚度试验装置。该装置由3部分构成:相对湿度控制系统、变形测试系统和波速测试系统。相对湿度控制系统可分级提供环境室内相对湿度,通过称重模块记录土样质量变化;变形测试系统利用图像采集结合数字图像处理技术获得土样体变;波速测试系统采用压电陶瓷元件制作的波速传感器,可同时测试土样脱湿过程中压缩波及剪切波波速。试验结果表明:该装置能够分级稳定控制相对湿度环境、间接测量土样体积变化及实时测试弹性波波速,进而研究波速表征的小应变刚度随饱和度的变化规律;土样剪切波速及小应变剪切模量随饱和度的降低逐渐增加,压缩波速及小应变体积模量随饱和度的降低先减小后增加。该装置结构简单,便于操作,为研究非饱和土小应变刚度特性提供了科学有效的测试方法与试验手段。

To investigate the influence of degree of saturation on small-strain stiffness of soil under evaporation conditions,an experimental device for measuring small-strain stiffness of unsaturated soils was developed.The device consists of three components:relative humidity controlling system,deformation monitoring system,and wave velocity measuring system.The relative humidity generator is used to modulate the relative humidity inside the environmental chamber.The weight change of soil sample is recorded through the weighing module.A digital camera is used to take photos of the upper surface and the side of the soil sample at the same time.The sensors measuring compression and shear wave velocities are designed and fabricated by using piezoelectric ceramic elements.The small-strain stiffness of soils is then determined by wave velocities.The experimental results show that the system can stably control the relative humidity of the environmental chamber,indirectly measure the volume change of soil sample,and monitor the variation of wave velocities of soil in real time.On this basis,the dependencies of wave velocity and small-strain stiffness of soils on degree of saturation can be observed.Shear wave velocity and small-strain shear modulus of soil samples gradually increase with decreasing the degree of saturation,while compression wave velocity and small-strain volume modulus first decrease and then increase with decreasing the degree of saturation.The test system is simple in structure and easy to operate,providing a powerful tool to investigate the effect of degree of saturation on the mechanical properties of soil.