# Study of Static and Dynamic Properties of Sand under Low Stress Compression
## 2 Materials and Methods  
### Methods  
The outline of this research, according to the reasoning already presented in the introduction (Section 1), is shown in Figure 2 in the form of a block diagram. This study consists of three types of experiments, and they are as follows: (1) a modified oedometer test using dry sand samples (OD hereafter), HtD \(<\) 1; (2) a modified uniaxial compression test with passive confinement using dry sand samples (UCD); and (3) a modified uniaxial compression test with passive confinement using wet sand samples (UCW). The HtD for UCD and UCW was \(\approx\)2 (see the following for more explanation). Figure 3a,b shows the experimental setups for these three types of tests. The oedometer loading system (Matest S.p.A, Treviolo BG, Italy) was used as the basis for the OD experiments (Figure 3a). The used load cell (blue cylindrical ring in Figure 3a) allowed vertical deformation of the soil sample, restricting its horizontal extension. The inner diameter of the load cell was 51.6 mm, while its height was 31.5 mm. The sample was incrementally loaded via its top end while its bottom end was in a fixed condition. The load increment was 5 kg. The maximum load applied to the samples was 30 kg, corresponding to an applied stress level of 143.5 kPa. At each increment of loading, the final deformation value was measured using a displacement gauge (Figure 3a). The loading system (ELE International, Leighton Buzzard, UK), modified for uniaxial compression by using a steel load cell, was used as the basis for the UCD and UCW experiments (Figure 3b). The load cell (black cylindrical ring in Figure 3b) allowed vertical deformation of the soil sample, restricting its horizontal extension. The internal diameter of the load cell was 38.6 mm, while its height was 71.1 mm. The sample was incrementally loaded via its top end while its bottom end was in a fixed position. The load increment was 10 kg (\(\sim\)100 N). The maximum applied stress level was \(\sim\)350 kPa. At each increment of loading, the final deformation value was measured using a displacement gauge (Figure 3b). During all three experiments, two US sensors for P wave speed measurement were located at both ends of the soil samples, while the AE sensor was located at the fixed bottom end of the load cell. The generating and receiving US sensors were connected to the pulse generator (TG5011A) and the digital oscilloscope (GDS1054B), respectively (Figure 3a,b). Figure 2: Block diagram presenting the research outline. The key objective of this research was the comprehensive experimental study of the mechanical and dynamical properties of sand in the pre-yield regime by means of combined acoustic emission (AE) and ultrasound (US) analysis. The resonance frequency of the US sensors was 75 kHz. The Open Wave software was used for data recording to a personal computer (PC). The US wave speed was measured using the first arrivals method. Figure 3: The experimental setup for the ultrasonic and acoustic emission study. (**a**) The oedometer with dry sand samples (OD) test. (**b**) The modified uniaxial compression test with passive confinement using dry sand samples (UCD) and modified uniaxial compression test with passive confinement using wet sand samples (UCW) tests. For the explanation of these abbreviations, see Section 2.1. The AE sensor was connected to the micro-SHM (Structural Health Monitoring) monitoring system (Mistras/Physical Acoustic Inc, Princeton Jct, NJ, USA). The AEwin for micro-SHM software was used for data recording to the PC. The measurements of AE were restricted by digital filtering in the range of 300-500 kHz to diminish acoustic noise. AE measurements were carried out continuously at each stage of loading while the pulse generator was turned off.