砂土小应变动力特性弯曲–伸缩元联合测试试验研究

近年来弯曲元在小应变动力特性测试中得到了广泛应用,但对弯曲–伸缩元的联合测试研究较少,国内对弯曲–伸缩元联合测试的研究几近空白。采用弯曲–伸缩元对福建砂进行了剪切波和压缩波联合测试,通过更宽区段激发频率和不同分析方法对剪切波速和压缩波速的确定进行了系统分析,得到了可靠的剪切波和压缩波传播时间确定方法。采用10~20 k Hz峰值法和互相关法可较方便准确地确定剪切波传播时间;压缩波初始到达较易判断,激发频率对压缩波速影响较小。利用弯曲–伸缩元联合测试得到剪切模量G_0和侧限模量M_0,试验结果表明围压和孔隙比对G_0的影响程度均较对M_0的影响程度大。通过剪切波速和压缩波速可计算得到泊松比,随密实度和围压的增大泊松比均以线性规律减小。为弯曲–伸缩元的进一步应用提供了有效的方法。

Laboratory study on small-strain dynamic properties of sand by bender-extender element

Measurements of small-strain dynamic properties by bender elements are popular in recent years. However, the study of bender-extender elements is less mentioned, and their application in China has rarely been reported. In this study, the S-wave and P-wave velocities of Fujian sand are simultaneously measured by a single pair of bender-extender elements. In order to find the travel time for S-wave and P-wave, wider excitation frequencies and different methods are used, and reliable methods for the determination of the S-wave and P-wave velocities are obtained. The test results show that the peak-peak method and the cross-correlation method using 10~20 kHz excitation frequencies are exact and convenient. The small-strain properties, including shear modulus G₀, constrained modulus M₀ and Poisson's ratio υ, are determined for specimens by measuring the S-wave and P-wave velocities. G₀ increases faster than M₀ as the soil density and confining pressure increase. The Poisson's ratio decreases linearly with the increasing soil density and confining pressure. The results of this study provide effective methods for the further application of bender-extender elements.