## 2 Materials and Methods
### Specim Preparation and Testing  
To mitigate the variability usually observed in natural soils, the present work uses remolded samples which maintain the organic matter content, mineralogical composition and grain size distribution composition of the natural soil; but the intrinsic structure of the natural soil is totally destroyed during the remolding process. The preparation of the soil used for testing started by sifting the natural soil through a 2.36 mm mesh sieve to remove the larger particles and some shell residues. The OM content of a certain amount of \"natural\" soil (OM = 7.7%) was destroyed by loss-on-ignition at 400 \({}^{\circ}\)C, which was then used to prepare the specimens with different OM contents (1.5-5.5%). The specimens of the soils with the different OM contents were prepared in accordance with the following actions (Figure 2):  
1. This soil subjected to loss-on-ignition at 400 \({}^{\circ}\)C (with an OM content of 1.5%) was mixed with the \"natural\" soil (OM = 7.7%) in different amounts to obtain the samples of artificial soil with the desired OM content, between 1.5% (lower OM) and 7.7% (natural OM). Naturally, the process of adjustment of the OM content had some iterations, with the re-evaluation and eventual re-adjustment of the OM content;
2. In the case of the stabilized samples, an XG content of 1% (ratio of the dry weight of XG to the dry weight of the soil) in powder form was added to the dry artificial soil and mixed well;
3. The artificial soil (with the required OM content), with or without XG, was mixed with the distilled water, to obtain a liquidity index of 1.1, during the time necessary to obtain a homogeneous soil-water-XG paste;
4. The mixture was introduced into the UCS moduls (38 mm in diameter, 76 mm height) and oedometer moduls (70 mm in diameter, 19 mm height) in 3 layers and 1 layer, respectively;
5. Each layer was subjected to tapping (10 times) to remove air bubbles and compacted with 100 kPa for 10 s;  
Figure 2: Flow chart of the specimen preparation. * A superficial scarification of the previous layer was performed to improve the connection between two successive layers in the molds;
* Based on the results of [PERSON] and [PERSON] [29], the stabilized specimens were stored in a plastic bag during 14 days of curing time (only stabilized specimens) inside a room with controlled temperature (20 \(\pm\) 2 \({}^{\circ}\)C) and humidity (95 \(\pm\) 5%), in order to reduce the suction phenomenon. The unstabilized specimens were not submitted to a curing time;
* After that, the specimens were removed from the molds, both surfaces were trimmed and the quality of the samples was analyzed visually;
* The specimens with the required quality were accepted for testing (UCS and oedometer tests);
* The oedometer ring (polished stainless steel) was coated with a thin film of grease prior to the oedometer tests to minimize the friction between it and the soil;
* The oedometer ring was assembled with the specimen, and they were saturated by immersion;
* The displacement transducers (both tests) and the load cell (UCS tests) were set up and adjusted;
* The UCS and oedometer tests were carried out. The vertical displacement (both tests) and the vertical pressure (UCS test) were recorded by an automatic data acquisition system;
* A strain controlled test was used in the UCS tests under a strain rate of 1%/min (ASTM2166-05);
* In accordance with ASTM D2435-04, stress increments with a load ratio of 2 were applied in the loading path of the oedometer tests, while in the unloading path a load ratio of 4 was used during the time required to the end of the primary consolidation. The coefficient of consolidation (Cv) was evaluated using [PERSON]'s methodology. For each condition tested, the UCS tests were repeated three times and the oedometer tests were duplicated, which ensured the quality and reproducibility of the tests carried out (Table 1).