The effect of Quaternary natural hazards on potential rock fall hazard using the rock engineering system method (case study of Tehran province)

Tehran is known as the most important political-economic and demographic center of Iran. The rock fall as a natural hazard has always caused a lot of damage in this City. Therfore, identifying the factors that are effective in the occurrence of this phenomenon is very important. In most cases, the danger caused by falling rocks cannot be avoided. Because the spatial and temporal variation of this phenomenon is very high. The main goal of the current research is to investigate the parameters involved in the rock fall in Tehran province.

The rock engineering system is an analytical method that prepares a model to studying the problem and analyzing its variables. The main tool of this method is the interaction matrix. This matrix makes the effect of all parameters on the system and the effect of the system on the parameters to be studied. Numerical and analytical models are only able to model a part of the interaction between different parameters, but this method is able to model a complete system. Due to the cause and effect nature of these interactions, the system has a dynamic state, which means that a change in a parameter can decrease the value of that parameter in a chain process. These changes occur until the system reaches equilibrium. In order to prepare a rock fall potential map, it is necessary to take help from 7 different layers, including the slope, relative relief, rainfall distribution, vegetation, seismicity, weathering and rock blocking. Therefore, first of all, the mentioned maps are classified separately. Then, it is necessary to prepare a map of rock fall potential by giving weight to each of the layers. In this research, the rock engineering system method was used to weight the above parameters.

In this study, the rock fall potential map was prepared by using 7 layers of information and weighting each one according to the rock engineering system. This map shows a well-defined relationship between mountainous areas and increased risk of rock falls. Also, in the location of the main faults, a significant increase in the hazard of rock fall can be seen. The increase in topographic slope can be considered effective in the changes in the hazard of rock falls. In general, since rock fall potential is prepared based on 7 data layers, each of these layers is effective in changing the hazard level. It should be noted that the role of faults has been properly considered in two ways, one in the amount of rock crushing or blocking and the other in earthquake acceleration. The location of landslides and slope instabilities was also compared with the hazard map of rock fall. Based on this, it was found that all these positions are located in areas with very high to high risk. This case confirms the accuracy of the present analysis to some extent. The results of this research are used to indicate areas at risk.

 Conclusion:

In most of the studies related to rock falls, the main goal is to reduce the risk of this phenomenon. To reduce the risk of rock fall, the dominant mechanism should be identified and then the risk of this phenomenon should be reduced by explaining the important factor with corrective measures. One of the methods used to reduce the rock fall hazard is to reduce the hazard elements in the rock fall area. Also, in many cases, it is not possible to reduce the risk elements and some protective structures, and corrective measures must be taken to protect the risk elements from falling blocks. For efficient facility design, some characteristics of the fallen blocks should be available to help designers make decisions about facility location and capacity.