The mere mention of "Mount Uhud" brings to mind the historical and religious significance of this spot in Medina, Saudi Arabia, which was an important motivation for a joint Saudi-Egyptian research team to test the solidity of the mountain that bears traces from the time of the birth of the earth.
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The study, published in the journal "Geoscience," which included a research team from Taibah University in Saudi Arabia and Al-Azhar and Assiut Universities in Egypt, has a geological and engineering character. However, the religious and historical background of the mountain, which the research team described in the introduction to their study as "exceptional," was present as one of the main motives for this study, which assesses the stability of the rocky slopes in the mountain, with a particular focus on a slope in the southern part, close to population centers.
The mountain extends for a distance of approximately 5 to 6 kilometers from the Prophet’s Mosque. In addition to its value in Islamic history, it represents an ancient geological record dating back to the beginnings of the formation of the Earth’s crust in the Arabian Peninsula, as it is located within the Arabian Shield. It is one of the oldest rock formations in the region, and consists of igneous and volcanic rocks dating back to the Precambrian era, that is, more than 550 million years ago, before the appearance of complex life on Earth.
The researchers say in their study that the mountain formed a natural geomorphological barrier that limited urban expansion to the north, while urban development was mostly concentrated in the southern, eastern and western directions of it. However, in recent decades, accelerated urban expansion has increased on the southern slopes of the mountain, which has intensified the interaction between engineering infrastructure and the steep natural slopes.
Fearing that this expansion would increase exposure to risks associated with slopes, particularly rockfalls, the researchers conducted a geotechnical assessment of the mountain's rocky slopes, and their concluding recommendation was that caution and monitoring should continue.
The idea of the traditional test is based on entering one value for each factor affecting stability, such as the cohesion of the rocks, the angle of internal friction between them, and the degree of slope. Then a series of calculations are carried out to compare two opposing forces. The first is the force that pushes the rocks to slide or collapse due to gravity, and the second is the force that resists this slide and maintains the cohesion of the slope. Through this comparison, what is known as the “safety factor” is calculated.
The "safety factor" is a measure of slope stability. A value greater than one indicates that the resisting forces are stronger than the forces causing collapse, and the slope is stable. A value less than one indicates that the forces driving collapse are stronger than the resisting forces, meaning there is a theoretical risk of failure or collapse.
In the case of the studied slope of Mount Uhud, the safety factor reached “0.813”, a value less than the safe limit of “1.0”, which prompted the researchers to initially classify it as unstable.
This type of analysis represents a "one-shot" of reality, because it assumes that the properties of the rock are constant in all parts of the slope.
The second test, conducted by the researchers, takes into account the natural variation in characteristics from place to place.
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