A Preliminary Study For Some Landslides And Rockfalls In Yemen

Studying the landslides and rockfalls in Yemen still in its preliminary stage, and study area landslides and rockfalls site is a chronic problem as many other areas in the Republic of Yemen, as a developing country, such kinds of problem can cause strong impact on its economy. The present authors have tried to highlight, to study and to find best solution for this problem for the first time. Field work, collecting data and laboratory test for many rock samples such physical properties, chemical for major elements, the result was as following D1, D4, C1, M1, M2, and H3 plot in the quartzose sedimentary provenance field are generally thought to have been derived form a recycled passive margin setting, while D2 plot in the mafic igneous provenance in the provenance discrimination, volcanic rocks classification of rocks and thin section have been carried out. The physical properties performed according to ASTM, and then the results have been gotten and discussed. Finally the conclusions have been drawn out and recommendation also suggested.According to topography of Yemen, most areas and villages are located at obligated crest, foot mountain and under cliffs. The human loss and property loss are high due to slope of rocks. Therefore Al-Gayah area, Al-Huwayshah and Jabal Munif which consists of Tawilah sandstone group are characterized by steep slope reach to 90° in some areas. While the Jabal Al-Fala'a (Qadas), Jabal Al-Barhah (Al-Kebah) and Dahboah are consist of Tertiary volcanic rocks which are characterized by steep slope reach to more than 70° in some places. All these areas affected by strong tectonic movements and faults trending that occurred during the geological epochs form this steep slope there are main causes of rockfalls, landslides and steep slope of rocky masses. This situation causes unstable geologically of this areas. This indicates the existence of old primary faults in areas that leads to descend the rocky masses which play an important rolein instability and deformation of rocks. This effect enhances to find out fractures and joint as well as the rocks become brittle and ready to slide depending on the position of area. These fractures and joints were directed perpendicularly and their height more than 30m were penetrated the sandstone rocks. And there are some fractures and joints on the surface of the areas due to tectonic movement associated with opening the Red Sea and Gulf of Aden.Rain water plays a big role in the processes of landslides and rockfalls in these areas are considered from the basic causes of landslides and rockfalls processes, where the rocks, soil and sediment are saturated with abundant water, which fall down in the process of absorption through the proprieties of permeation and separation of soil molecules and sediment, subsequently the over all block becomes saturated block with water. There are mudstone layers between the sandstone rocks which affected directly by water of rainfalls lead to expand and decomposed. Due to weight of such beds the mudstone layers break, decomposed, cavernous. So the areas are becoming unstable. In these slopes include a lot of watercourses which pass the study areas and throw reach to the lower beds during the fractures and joints that result to form of lubricant material in order to enhance the slide process of that overly rocks.Since long period Yemen has been subjected to many earthquakes. The records of earthquake in Yemen indicate that the activity is frequently and with high magnitude in littoral, western and north zones and in mid highlands as well as the complete or partial destructions were of followed at these zone. The most important factors are the geographic position of Yemen and the properties of geological structures. Further, the faults center of Red Sea and Gulf of Aden that extend to other areas leads to natural disasters rock hazards are one of the earthquake effects. The masses are triggered from mountain highlands and foot due to horizontal and perpendicular forces of earthquake waves at seismic focus zones where the surface waves are distributed. The earthquake is considered as catalyzed factor for occurrence of landslides and rockfalls in Yemen, plotting of...