# Predicting Swell in Clay-Sand Mixtures Used in Liners
## 2 Materials and Methods
### Testing Methods
#### 2.2.2 The Oedometer Testing Method  
Using traditional oedometer techniques, tests for one-dimensional swelling were conducted. The sample was immersed in a container that enclosed a ring (the oedometer cell). Each sample had two porous disks at the bottom and top attached to Whatman filter sheets. This oedometer cell was housed inside a loading frame that transferred vertical loads via a uniquely crafted lever arm. Either a dial gauge with a precision of 0.01 mm or calibrated sensors that sense vertical movement were used to track changes in the sample height.  
The utilized ring had a 50 mm diameter. A variable sample height was employed. The samples ranged in thickness from 3 to 8 mm. It was discovered that the initial swelling takes place more quickly in thin samples.  
To estimate the swell parameters, one-dimensional swell testing was performed in accordance with ASTM D4546-96 method A [16]. The approach that deviates from this one uses a seating pressure of 7 kN/m\({}^{2}\). This technique involved submerging the sample and letting it swell vertically at the seating pressure for the duration of the principal swell. Similar procedures were used in the tests with various vertical effective stresses.  
The ring's weight as well as the sample's weight were calculated. The sample's original height was noted. The initial moisture content and specific gravity were computed. These made it possible to calculate the height of the solids, Hs:  
\[\mathrm{Hs}=\frac{\mathrm{Ws}}{\mathrm{A\cdot Gs\cdot\gamma_{\mathrm{w}}}} \tag{6}\]The initial void ratio \(e_{0}\) was computed using the following formula:  
\[e_{0}=\frac{\mathrm{H-Hs}}{\mathrm{Hs}} \tag{7}\]  
The change in the void ratio can be measured at any stage of the test in a similar fashion. Thus, the final void ratios at the end of the test are given as  
\[e_{f}=\frac{\mathrm{H-Hs}}{\mathrm{Hs}} \tag{8}\]  
where \(\mathrm{Gs}\) is the specific gravity, \(\mathrm{Ws}\) is the dry weight of the sample, and \(\gamma_{\mathrm{w}}\) is the density of water. The degree of saturation is given as  
\[\mathrm{Sr}\cdot e\ =\mathrm{wGs} \tag{9}\]  
where \(\mathrm{w}\) is the moisture content.  
Similar procedures were used for the oedometer tests conducted on remolded samples, bentonite powder, and mixes.  
The samples were given time to air dry. In order to create a paste with a known moisture level, distilled water was added. If the dry density is known, the amount of soil required to fill the consolidation ring can be calculated. The calculated amount was tamped into the ring in two or three lifts.  
The final clay void ratio was obtained from the pretest conditions as above, \(e_{1}\), and the post-test parameters, \(e_{2}\), using the following equation:  
\[1+e_{2}\ =\frac{\mathrm{Gsy_{w}}}{\gamma_{\mathrm{d}}} \tag{10}\]  
where \(\gamma_{\mathrm{d}}\) is the dry unit weight.  
This confirmed the accuracy of the data observed and recorded.  
The final void ratio was taken as the average of \(e_{1}\) and \(e_{2}\). The surcharge or vertical effective stresses used varied from 1.96 to 400 kPa. This range covered the needs of geotechnical practice.