4. Discussion💬🤨

4. Discussion

4.1 Key Findings, Comparison and explanations

From Figure 5, we can conclude that the shear strength of soil decreased as the moisture level of the soil increased, resulting in a downward trend. However, for Figure 6, we can see that the tensile strength of soil increased as the moisture level increased. As seen in Figure 5, there was anomaly data for shear strength, which had an average shear strength of 2696.82 kPa while the shear strength of other soils was around 1000 kPa. As such, we repeated the experiment under the same conditions as the original soil samples. However, there was still an anomaly, and due to the lack of resources and time, we were unable to repeat the whole experiment for all of the soil samples.

For shear strength, the highest value was 2696.82 kPa with a moisture level of 2.7, while our lowest value was 833.56 kPa with a moisture level of 3.4. For tensile strength, the highest value was 2.60 psi with a moisture level of 3.8, while the lowest value was 1.83 psi with a moisture level of 2.5.

In another journal, Liu et al. (2021) conducted an experiment investigating the effect of moisture content on the shear behaviour of a completely decomposed granite, and they reached the conclusion that the increased moisture content could obviously weaken the shear strength, cohesion, and frictional angle. Therefore, we can conclude that even though we had an anomaly for shear strength, our line of best fit still showed a downward trend, which are the same results that Liu et al. (2021) obtained.

4.2 Limitations and Recommendations

We were unable to find the unit for the Moisture Level of the device that we used, which is the Rapitest 4-in-1 Meter. Not having units may make it harder for experiments like ours to be repeated if they do not have the same device. We could have used another device that did have units or one that is universally accurate for everyone to use as a standard.

For our shear and tensile strength experiments, we were unable to cut the soil samples accurately to the point where both soil portions are equal. This would mean there are some differences in the height and masses of the soils, making them not exactly the same. However, they were still similar enough to avoid complications. We could have tried to be more accurate by choosing the smallest mass as our default, and then cut off more portions of each soil sample until it was close to the smallest mass.

We also did not have much resources or time to redo any of our experiments to figure out why there was an anomaly or why there were no distinct trends. We could have planned better for a scenario like this by having some soil as backups or by starting our experiment earlier to make sure we had some time and resources left to redo our experiment if needed.

Due to human error, the results for the tensile strength was also spaced out, as seen in Fig. 6. There was no gradual increase, but instead, the values are fluctuating. For example, the soil sample with a moisture level of 3.5 had a tensile of 2.35 psi, the soil sample with a moisture level of 3.6 had a tensile strength of 1.91 psi, and the soil sample with a moisture level of 3.8 had a tensile strength of 2.60 psi. This shows that our results can be fluctuating at times and is not a gradual increase or decrease, and this is most likely due to human error. However, this error was resolved by the line of best fit.

4.3 Evaluation of Hypothesis

From the results obtained above, we can generally conclude that our hypothesis 1 (H1), which states that “ soils with a higher moisture level will have greater shear strength. ” is incorrect. If H1 is true, then the graph for shear strength should have an upward trend, as seen in Fig. 3, which is our experimental graph for shear strength. However, the trend for shear strength data turned out to be downward, as seen in Fig. 5. As for our hypothesis 2 (H2), which states that “soils with a higher moisture level will have greater tensile strength.”, is proven to be correct by our data. As seen in Fig. 6, which was the graph for the tensile strength recorded for our soil samples, had an upward trend, just like our experimental graph. To conclude, H1 is incorrect but H2 is correct.