边界约束对弯曲-伸展元三轴波速试验的影响

利用弯曲-伸展元开展干砂小应变剪切波试验和除气水压缩波试验,研究了三轴试样的不同约束边界对弯曲-伸展元量测剪切波速和压缩波速的影响,并对波速试验结果进行分析。研究结果表明:以干砂为试验对象的剪切波速试验结果介于砂土中剪切波速与边界材料的剪切波速之间,受到约束边界的材质、长度和壁厚的显著影响;而以除气水为试验对象的压缩波速试验结果受样品约束边界的影响较小。在不同约束材质下,剪切波在干砂中的传播速度与约束材料的刚度有关,材料的刚度越小对干砂剪切波速测试结果影响越小。弯曲-伸展元激发频率的相关性与边界约束无关,只与测试材料有关。研究成果有助于获取准确的弯曲-伸展元波速试验结果。

Effect of Boundary Constraints on Measurement of Wave Velocities of Triaxial Specimens Using Bender-extender Element

Bender-extender element test is performed to measure shear wave velocity of dry sand and compression wave velocity of deaerated water. Effects of different boundary constraints on the measurement result of shear wave velocity and compression wave velocity by bender-extender element test are investigated, and the causes of the results are explained. Test results of shear wave velocity are between the shear wave velocity of dry sand and the shear wave velocity of material of boundary constraints. The results of shear wave velocity are indeed affected by the material of constraints, length of constraints and thickness of constraints; but the results of compression wave velocity are less affected by boundary constraints. In tests with different materials of constraints, the results of shear wave velocity are related to the stiffness of the material of constraints. The smaller stiffness of the material, the smaller impact on the test results of shear wave velocity. The correlation of excitation frequency is independent of the boundary constraints and is only relevant to the soil. This study is conducive to obtain accurate test results of bender-extender element.