A suffusion visualization apparatus based on planar laser induced fluorescence and the preliminary application

The evolution of suffusion initiating and progressing within internally unstable soil has the characteristics of high concealment and tremendous harmfulness. Conventional laboratory tests can only observe the migration of fine particles nearby the transparent wall or the motion trail of trace particles but cannot directly monitor the migration of fine particles within the soil, which significantly hinders the understanding of suffusion mechanisms. This paper developed a new suffusion visualization apparatus based on planar laser induced fluorescence technology(PLIF), which consists of a permeameter, a PLIF system, a high speed camera and an image processing system, and produced transparent soil specimens by adopting melted quartz sand, #15 white oil and D80 Solvent oil with the same refractive index. A testing method for preparing high transparency internally unstable specimens was proposed, and a list of transparent soil suffusion tests were performed. The results indicate that the newly designed apparatus can continuously monitor the migration of fine particles within the specimens. Temperature has significant influence on the refractive index of liquid and the transparency specimens and hence, should seriously be controlled no more than 25℃. Fine particle content and minimum particle size also have significant effect on the specimen transparency, and it is suggested that the fine particle content should be less than 35% and the minimum particle size should be smaller than 0.2 mm. It is revealed that suffusion will progress along to the weak zones within the specimen, then form a concentrated leakage path and eventually result in damage of soil structure. The new apparatus based on PLIF will provide an effective tool for investigating the mesoscopic mechanisms of suffusion. © 2021, Science Press. All right reserved.