Study of Static and Dynamic Properties of Sand under Low Stress Compression

Abstract

The aim of this work was to investigate a wide range of grain sizes of sand in the pre-yield regime during compression through the combined study of ultrasound (US) wave speed and acoustic emission (AE). The specific study was performed using modified oedometer and uniaxial compression experimental set-ups. The studied samples were natural dune sand (poorly graded on the poorly graded sand (SP) index) as well as its three extracted fractions as follows: 2.36–0.6 mm, 0.6–0.3 mm and 0.3–0.075 mm. The maximum compression stress during the modified oedometer experiments was <150 kPa, while during the modified uniaxial compression experiments, it was <400 kPa. Each sample was loaded while measuring the US pressure (P) wave speed and AE at each loading stage. The results show that the stiffer the soil is, the higher the value of the P wave speed measured, resulting in similar P wave velocity values achieved at a much lower applied stress during the oedometer experiments in comparison with the uniaxial compression tests. Regarding the AE results, it is seen that the higher the stress level is, causing more friction between the sand particles, the more AE events there are during their movement. The following parameters of AE were shown to be the most sensitive to the stress increase: the number of AE hits and the signals’ energy.

Acoustic emission induced by sand liquefaction during vibration loading

“…10 f). Note that this observation is consistent with the results of our earlier studies 37 , 38 (see Sect. “Discussion and conclusion”) as well as with the results presented by Hu et al 43 and Tanaka and Shirakawa 44 , 45 .…”

“…The materials and methods used in the study are described in detail in our previous articles 37 , 38 , below we will only briefly consider these issues. The dune sand material for the study was collected in the coastal area of ​​Ashdod (about 30 km south of Tel Aviv city, Israel).…”

“…The value of 5% of the water content is the experimentally found largest amount of water that can be absorbed by a sand sample without squeezing out the water during sample compaction 37 , 38 , (c) each cylindrical sand sample was prepared inside an elastic jacket/membrane and into a mold on the pedestal (Fig. 2 b) using a wet-tamping method 52 – 54 by using a hand-held tamper.…”

“…A close correspondence was found between the number of AE pulses, their energy, and the stress–strain state of the soil 31 . A concise review of AE caused by failure of soil samples was presented in 37 , 38 where the AE phenomenon was investigated using dry and wet sands of different grain content. It was shown that failure of granular materials associated with the AE in the frequency range of tens kHz while low-frequency diapason (< 20 kHz) provides information on the features of the shear zone while the higher range (> 30 kHz)—on stress release events 39 , 40 .…”

An Overview of the Study of Acoustic Emissions in Soil Mechanics

“…The challenge is complex, since the mechanisms that generate acoustic emissions in soils subjected to load or displacement processes are varied, the main ones being [1]: i) reorganization of grains contact points, ii) movement of the liquid or the liquid-gas interface, iii) intergranular friction and iv) crack formation. In principle, the characteristics of the acoustic emissions will differ [2] from one mechanism to another, so that the detailed study of these can provide information, complementary to that obtained by the classical methodologies in soil mechanics, which is very valuable.…”