Gap-graded cohesionless soils are extensively utilized in numerous man-made geotechnical structures such as earthen embankments, man-made fills and used for the prevention of seepage in dams and tailings of mines. However, there is a lack of research available on investigating the transitional behaviour of frequency responses of gap-graded cohesionless soils. Therefore, the present research explores the stress wave transmission in gap-graded silica sand mixtures (having median particle size ratio of 6.4) using disk-shaped piezoelectric transducers (DTs). By employing DTs, shear (V_s) and compression (V_p) wave velocities are measured using more planar waves and eliminate the possibility of fine particle segregation commonly encountered during insertion of bender elements. The experimental results indicate that at an equivalent void ratio, V_s and V_p decrease initially with the increase in fine silica sand content (F_s); however, once a transitional value (F_s,thr) is attained, V_s and V_p start to rise and move towards the values for fine silica sand. Such transitional behaviours of elastic wave velocities and frequency-domain responses are dependent on the state of packing, i.e. denser specimens achieve this at a lower F_s than the looser equivalents. It is observed that for a given F_s, there exists a linear relationship between the maximum transmitted frequency in the packing, i.e. low-pass frequency (f_lp) and the V_s. Furthermore, a novel approach has been described by which the type of gap-graded mixture, i.e. underfilled (internally unstable) or overfilled (stable), can be assessed by experimentalists from the slope of f_lp–V_sresponses. The advantage of adopting f_lp to categorize the gap-graded mixtures is that the same is more sensitive to F_s in comparison to V_s or V_p, and thus a more robust analysis can be achieved.

缝隙级配无粘性土广泛用于许多人造岩土结构，如土堤、人造填充物，并用于防止大坝和矿山尾矿渗漏。然而，缺乏研究间隙级配无粘性土的频率响应的过渡行为。因此，本研究使用盘形压电换能器 (DT) 探索了间隙级配硅砂混合物（中值粒度比为 6.4）中的应力波传输。通过使用 DT，剪切 ( V _s ) 和压缩 ( V _p) 波速度是使用更多的平面波测量的，并消除了在插入弯曲元件期间常见的细颗粒分离的可能性。实验结果表明，在等效孔隙比下，V _s和V _p最初随着细硅砂含量( F _s )的增加而减小；然而，一旦达到过渡值 ( F _{s , thr} )，V _s和V _p开始上升并接近细硅砂的值。弹性波速度和频域响应的这种过渡行为取决于堆积状态，即，与较松散的等效物相比，更密集的样本在更低的F _s下实现了这一点。可以看出，对于给定的F _s，在封装中的最大传输频率，即低通频率 ( f _lp ) 和V _s之间存在线性关系。此外，已经描述了一种新颖的方法，通过该间断级配混合物的类型，即，未充满的（内部不稳定）或过度填充（稳定），可以通过从实验家的斜率评估˚F _LP -V_的反应。采用f _lp对间隙分级混合物进行分类的优点是，与V _s或V _p相比，f _lp对F _s更敏感，因此可以实现更稳健的分析。