Document Type : Full length article
Authors
1
Department of Natural Geography, Kish International Campus, University of Tehran, Tehran, Iran
2
Department of Natural Geography, Faculty of Geography, University of Tehran, Tehran, Iran
Abstract
A B S T R A C T
The studied road starts from Lashkarak in the northeast of Tehran and at the entrance of Lavasan, changing its direction to the northwest, passing through the areas of Zardband, Rudak, Haji Abad, Fasham, Migun, Jiroud, Durud, Darbandsar and Shamshak to Dizin in the province. Alborz extends. This road does not have a good level of safety in the current conditions despite having a relatively high traffic load, so increasing the safety of the road to facilitate the connection of the east of the city and the province of Tehran to the Tehran-North Freeway by developing this road is one of the main goals of the present study. . In this research, geological maps, topography and satellite images were used to identify the condition of the slopes around the road and prepare information layers and route zoning in the GIS environment. and the results of geomechanical evaluations were compared with the areas obtained from geomorphological data and the length of the route was divided into six categories in terms of geomorphic stability and road safety. The results showed that the alignment of the slope of the slopes with the direction of the stone layers and the soil cover of the roadside slopes is one of the most important factors of slope instability and determines the type of activity of the processes in this direction. This research, which was conducted by combining the information obtained from geomorphological and geomechanical results, has the ability to be used in the evaluation of other transportation routes in the country and can be used for road safety management and development
Extended Abstract
Introduction
Lashkark road starts from Lashkark in the northeast of Tehran city and extends towards Shamshak and Dizin. This route runs along the length of the Alborz mountain range, after Lashkarak, passing through the Quchak Stem at the entrance of Lavasan city, with a northwesterly direction from the residential areas of Zardband, Roodak, Hajiabad, Fashm, Meigun, Jiroud, Durood, Darbandsar and Shemshak at the end of the range. It crosses Tehran province and then extends towards Dizin in Alborz province and finally connects to Kandovan road in Shahrestanak region. The need to increase traffic safety in this route due to the increase in traffic and at the same time the possibility of connecting the east of the city and Tehran province to Tehran-North Freeway is the focus of this study. In addition, by establishing this communication, especially during peak traffic times, which usually occur during official holidays, or when there is a traffic problem in a part of the Tehran-North Freeway, It can help to traffic on Tehran - North Freeway.
Methodology
In this research, using geological maps, topography and satellite images, the initial identification of the active points of the field and the existing conditions of the route was done. Then, by determining the factors affecting the instability of the track domain, the information layers related to them were prepared in the GIS environment. Since the physical properties of sediments and rocks are considered to be the most important foundations of engineering calculations, along with field surveys and route zoning, sampling of soil and rock domains in order to know more precisely the effective Sedimentological and lithological characteristics. It was done on the slopes overlooking the road. In this regard, the important physical characteristics including internal friction angle and adhesion, grain measurement and determination of Atterberg limits in soil domains, compressive strength in rocky slopes, texture , sorting of sediments and slope rocks were investigated and compared.
Results and Discussion
According to the results of the tests, Physical properties including angle of internal friction, cohesion and texture are similar in a large number of harvested samples. This is consistent with the stratigraphy of the studied area. The results of the internal friction angle are in the range of 32 to 40 degrees and the soil cohesion is in the range of 0 to 0.02 kg/cm2, which indicates that the grain is separated and with low cohesion of the slopes and indicates the high ability of slope sediments to fall and slide. The grains sorting the sediments are also generally in a very poor range. But in the end ranges of the studied route, especially in the Shemshak area, they have a medium rating. The results of Atterberg tests also confirm the non-cohesion of the range sediments, and according to the results of the same test, it can be said that the possibility of range movements in the form of creep or solifluction is very limited. The results of the compressive strength of the rock slopes show that the uniaxial compressive strength of the rock slopes of the path, except for one case with a resistance of 23 kg/cm2, is generally in the range of 80 to 110 kg/cm2, which indicates the uniform characteristics of the rocks. The texture of these rocks varies depending on the type, but they are mainly includ limestones from Karaj, Shemshak, Route and Doroud, as well as pyroclastic rocks. Considering the texture, low compressive strength and layered nature of the rocks in the majority of the path, it can be predicted that the erosion potential as well as the power of falling of these slopes is high and its effects can be seen in different parts of the path. In the rocky slopes of the path to Fasham, the type of rock formations includes pyroclastic and limestone layers, and depending on the direction of the layering and the slope of the slope, the erosion performance varies from lahar erosion to the fall of stone fragments. The most prominent example of this function can be seen in the Haji Abad area after the Galukan bridge, where weathered sediments in the form of Lahars are seen on the slopes of the road, and later, By changing the direction of the rock layers in relation to the road, rockfalls prevail. By passing Meigun, changing the geological formations and the type of rocks, their compressive strength and texture also changed, subsequently the type of activity of the rocky slopes was also different. Rockfalls of the slopes were less seen and the stability of the slopes increased significantly.
Conclusion
The results obtained from the analysis of geomorphic factors, including weathering conditions, elevation, slope and hydrological data, show similar results with the results obtained from geomechanical tests on the samples of sediments and rocks on the slopes of the road in terms of the stability of the slopes. In general, the length of the road that has traversed the Alborzmountain range is mostly consistent with the stratigraphic structures of the route. The slope direction of the slopes in relation to the road trenches is one of the most important factors of slope instability in this route, in such a way that the direction of the slope of the rock layers or soil cover with the road trenches causes rock falls or slope slides in the route has been lengthened and at the same time it has affected the possibility of transverse expansion of the road. This research, which has been done by combining the information obtained from the analysis of geomorphological processes and the results obtained from geomechanical data, has the ability to be used in the evaluation of other transportation routes in the country and can be used to help manage the safety of the route as well as the road development plan by the Ministry of Roads and Urbanization is used.
Funding
There is no funding support.
Authors’ Contribution
All of the authors approved thecontent of the manuscript and agreed on all aspects of the work.
Conflict of Interest
Authors declared no conflict of interest.
Acknowledgments
We are grateful to all the scientific consultants of this paper.
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