# Stress-Dilatancy Behavior of Alluvial Sands
## 3 Material and Tests  
The samples utilized in this study were obtained as part of a broader investigation, during which approximately 20 samples were collected for analysis. The majority of the samples were cohesive soil samples, and only non-cohesive soil samples were selected for testing in this study. The samples were collected using Class 1 samplers. The names of the sand samples shown in Table 1 (the number before the slash) refer to the order in which all samples were taken, and the value after the slash refers to the sampling depth. The insitu density value of the samples was determined by field tests (CPT) and then used to reproduce this state in the laboratory. The samples were taken from the lower section of the Oder River valley; therefore, the soil can be described as alluvial soil-river sand. Particle size distribution curves for the sands are shown in Figure 1, and the physical characteristics of the sands are summarized in Table 1. The coefficient of uniformity (\(C_{u}\)) ranges from 2.76 to 5.03, the coefficient of curvature (\(C_{c}\)) ranges from 0.94 to 1.39, and the median particle size (\(D_{50}\)) ranges from 0.32 to 0.50 mm. The sands also differ in terms of the maximum void ratio (0.70 to 0.75) and minimum void ratio (0.36 to 0.40). All sands are characterized by the same specific gravity value (2.66). The triaxial compression tests were conducted using the drainage method. The tests were performed on dry pluviated samples, which were compacted to a relative density of the soil corresponding to the degree of compaction determined by the in situ tests. This method was chosen because it is commonly used in geotechnical engineering to produce uniform sand samples for laboratory testing. The method involves allowing dry sand to pluviate through the air into a container, producing a sample with a controlled density and structure. Dry pluviation is favored for its simplicity and ability to produce samples with uniform density and structure, making it ideal for various geotechnical tests such as triaxial compression tests, direct shear tests, and permeability tests. The relative density was different for each sample, as shown in Table 1. The soils tested can be classified as medium and very dense [12]. The samples were saturated using the back-pressure method until the value of the Skempton parameter was greater than or equal to 0.95 or until the maximum value was obtained [13]. The specimens were then isotropically consolidated to a pre-selected effective stress value. The measurement of changes in the volume of samples during the test was carried out using state-of-the-art pressure and volume controllers from GDS Instruments. The volumetric strain was determined by measuring the volume of water flowing out of the soil sample and was carried out using a volume controller. \begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \(D_{50}\) & \(C_{u}\) & \(C_{c}\) & \(G_{s}\) & \(e_{\max}\) & \(e_{\min}\) & \(D_{r}\) \\  & **mm** & **-** & **-** & **-** & **-** & **-** & **\%** \\ \hline TXCD 2/17.5 & 0.32 & 5.03 & 1.39 & 2.66 & 0.75 & 0.36 & 0.93 \\ TXCD 5/22.5 & 0.50 & 3.39 & 0.94 & 2.66 & 0.70 & 0.38 & 0.95 \\ TXCD 7/14.5 & 0.43 & 4.05 & 1.13 & 2.66 & 0.73 & 0.41 & 0.82 \\ TXCD 20/7 & 0.42 & 2.76 & 1.18 & 2.66 & 0.71 & 0.40 & 0.60 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Physical characteristics of sand samples. Figure 1: Particle size distribution curves of the soils used in this study. The controller has a volume of 200 mL with a resolution of 1 mm\({}^{3}\) and can maintain pressure up to a value of 2 MPa. Volume measurements were carried out with an accuracy of 0.05% over the full measurement range. The axial load was measured using an internal submersible load cell with a range of 10 kN and a resolution of 0.001 kN. The specimen's axial strain was measured using a displacement sensor located outside the triaxial chamber, with a resolution of 0.001 mm. Cell and pore pressure was measured using external pressure transducers.