## 3 Testing Results and Analysis
### Triaxial CU Test  
In 2017, [PERSON] and [PERSON] [34] proposed the use of triaxial CU test parameters to simulate load bearing-related engineering problems that are encountered shortly after completing the initial compaction of soil. The present study used ELE International's Digitest 50 system to conduct tests. The strain was controlled at 1.06 mm/min. The pneumatic loading system was connected to a measuring system, which considered load cells, LVDT, volume changes, and pore water pressure sensors. A set of data loggers was used to establish a connection with a computer for data storage and analysis. As per ASTM D2850, triaxial CU tests were conducted. The testing stages included specimen preparation, saturation, confining pressure, consolidation, and application of deviator stress. Specimen saturation requires the Skempton pore water pressure parameter B value to be at least 0.95. After the saturation stage, we can measure the B value by applying incremental confining pressure. The consolidation stage involved the complete exclusion of excess pore water pressure inside specimens. The present study used three grain sizes (grains that passed through #4, #4-3/4\", or >3/4\" sieves) to prepare mudstone specimens. The remolded specimens with added cement paste were prepared using static methods. The confining pressures of the specimens were 50, 100, and 200 kPa. Figure 11 presents the triaxial CU test results of original mudstone soil and treated soil samples. Figure 11 presents the original soil stress-strain curves. When the strain was between 10% and 15%, the deviator stress peaked and then gradually decreased. The pore water pressure peaked when the strain was between 0% and 5%, which dropped sharply afterward. When the deviator stress was at its peak, the pore water pressure was between \(-\)20 and \(-\)60 kPa. Figure 11 presents the triaxial CU test results of specimens with added cement. The results revealed that when the strain was between 1.5% and 2.0%, deviator stress peaked and then gradually decreased. Figure 10: The relationships between \(\mathrm{q_{u}}\) and \(\mathrm{E_{50}}\) values based on mudstone and mudstone-cement samples. Figure 9: Elastic modulus \(\mathrm{E_{50}}\) with respect to dry density for untreated and treated samples: (**a**) mudstone; (**b**) mudstone–cement. The pore water pressure peaked at a strain of 0.5% and decreased sharply afterward. When stress peaked, the pore water pressure was between \(-20\) and \(-80\) kPa. In all tests, shear strength increased with an increase in cement content and dry density. Figure 12 uses various confined compression Mohr circles and failure envelope curves to present the triaxial CU test results of the original mudstone soil and mudstone-cement soil samples. Because the specimens were compacted and contained cement paste, the pore water pressure was negative when the deviator stress was at its peak. At that point, effective stress and soil shear strength should increase. [PERSON] et al. [16] conducted saturated soil triaxial UU tests and reported negative pore water pressure. Figure 12 indicates that when the specimen \(\gamma_{\text{d}}\) was 19.5 kN/m\({}^{3}\) and cured for 28 days with C = 0%, 4%, or 8%, the c values were 85 kPa, 147 kPa, and 167 kPa, respectively, and the \(\phi\) angles were 25.79\({}^{\circ}\), 44.37\({}^{\circ}\), and 44.35\({}^{\circ}\), respectively. The cohesion force and internal friction angle increased when the amount of paste added was increased. Figure 13 presents the CU test results for mudstone and mudstone-cement specimens, including the total stress c values and \(\phi\) angles. Figure 13a indicates that among the various clods, when \(\gamma_{\text{d}}\) increased, the \(\phi\) angle increased notably to between 23.5\({}^{\circ}\) and 27.6\({}^{\circ}\). However, the increase in the c value was not substantial, which could be related to the pore water pressure at specimen failure. The results of the mudstone-cement samples are presented in Figure 13b.