## 2 Uniaxial Compression Test on Earth Materials
### Selection and Preparation of Specimens
liquid limit clay [24]. It is characterized by high cohesiveness and low compressibility. This is consistent with the type of soil used in related studies. It suggests that the selection of the soil in this study basically meets the requirements for the construction of earth structures and is somewhat representative. Since there is no unified test standard for the forming and manufacturing method and size of the specimens in the uniaxial compression test of earth materials in various countries. Therefore, we refer to the European standard \"Design of Concrete Structures-Part 1-1: General rules and rules for buildings\" (EN1992-1-1) [31], the Chinese standard \"Standard for basic performance test methods of construction mortar\" (JGJ/T70-2009) [32], the New Zealand standard \"Engineering Design of Earth Buildings\" (NZS4297:2020) [33], and the Chinese standard \"Standard for Geotechnical Test Methods\" (GB/T 50123-2019) [22] to determine the shape dimensions of the studied test specimens as 150-mm, 70.7-mm, 100-mm-cubic test specimens and 102 mm diameter and 116 mm height cylindrical test specimens, respectively. A total of eight groups of specimens were designed and fabricated for the test (Table 3). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Specimen label** & **Specimen Type** & **Loading Rate** & **Curing Age** & \\  & **(mm)** & **(mm-min\({}^{-1}\))** & **(d)** & **Quantiity** \\ \hline Y\({}_{102}\)-14-0.2 & \(\Phi\)102 \(\times\) 116 & 0.2 & 14 & 6 \\ Y\({}_{102}\)-21-0.2 & \(\Phi\)102 \(\times\) 116 & 0.2 & 21 & 6 \\ Y\({}_{102}\)-28-0.2 & \(\Phi\)102 \(\times\) 116 & 0.2 & 28 & 6 \\ L\({}_{100}\)-28-0.2 & 100 \(\times\) 100 \(\times\) 100 & 0.2 & 28 & 6 \\ L\({}_{100}\)-28-1.0 & 100 \(\times\) 100 \(\times\) 100 & 1.0 & 28 & 6 \\ L\({}_{100}\)-28-3.0 & 100 \(\times\) 100 \(\times\) 100 & 3.0 & 28 & 6 \\ L\({}_{70.7}\)-28-0.2 & 70.7 \(\times\) 70.7 \(\times\) 70.7 & 0.2 & 28 & 6 \\ L\({}_{150}\)-28-0.2 & 150 \(\times\) 150 \(\times\) 150 & 0.2 & 28 & 6 \\ \hline \hline \end{tabular} \(Y_{102}\)-14(21 and 28)-0.2 represents the cylindrical specimens with a diameter of 102 mm and a height of 116 mm, the curing age is 14(21 and 28) d and the loading rate is 0.2 mm-min\({}^{-1}\), L\({}_{100}\)-28-0.2(1.0) represents the cube specimens with side lengths of 100 mm. The curing age is 28 days, and the loading rate is 0.2(10, 3.0) mm-min\({}^{-1}\); L\({}_{70.7}\)-28-0.2 represents the cube specimens with side lengths of 70.7 mm. The curing age is 28 days, and the loading rate is 0.2 mm-min\({}^{-1}\); L\({}_{150}\)-28-0.2 represents the cube specimens with side lengths of 150 mm. The curing age is 28 days, and the loading rate is 0.2 mm-min\({}^{-1}\); \(\Phi\): the diameter of a circle.  
\end{table} 
Table 3: Uniaxial compression test under different working conditions. Figure 4: Soil plasticity diagram. (CL = low liquid limit clay; CH = high liquid limit clay; ML = low liquid limit powder soil; and MH = high liquid limit powder soil). [1; 14; 19; 23; 26; 27; 28]. The earth specimens were fabricated by the light compaction method [22] with reference to the Chinese standard \"Standard for Geotechnical Test Methods\" (GB/T 50123-2019), and the fabrication details are as follows:  
1. The sieved soil material is dried in an oven, and the optimum water content is used as the control index to add water to mix the earth material. Then, it is sealed with a cling film and left to stand for one hour so that the moisture is evenly distributed in the earth material. 2. Filling the mold with wet soil, using manual compaction in multiple layers, the compaction height of each layer is approximately 38 mm, and the compaction work \(W\) is 592.2 kJ\(\cdot\)m\({}^{-3}\). The number of times of compaction per layer and the number of layers of compaction are calculated according to Equation (1), and the results are shown in Table 4 to ensure that the specimen is formed under a more uniform standard and achieves the maximum dry density.