Discussion on the analysis, prevention and mitigation measures of slope instability problems: A case of Ethiopian Railways

作者：Assefa, Eleyas^*; Lin, Li Jian; Sachpazis, Costas I; Feng, Deng Hua; Shu, Sun Xu; Anastasiadis, Anthimos S

来源：Electronic Journal of Geotechnical Engineering, 2016, 21(12): 4531-4547.

• Expansive soils
• Landslide monitoring system
• Limit equilibrium analysis
• Railway
• Reconnaissance surveys
• Risk management process
• Seismically active region
• Stress strain characteristics

Ethiopia is striving to build modern railway infrastructures and services to meet its endeavor in building a globally competitive economy, which uses electricity and connects the country's development centers and links with ports of neighboring countries. However, the planned railway routes in Ethiopia pass through the hilly and mountainous terrains of the highlands of Ethiopia. The hilly terrains of the highlands of Ethiopia remain highly fragile environments in terms of slope stability whereby any external factors such as heavy rainfall and/or excavations could trigger landslides [2]. In Ethiopia large infrastructure works (including railways) already lie or will be in or in close proximity to the some of the most seismically active regions of the country such as Afar Triangle, the Main Ethiopian Rift (MER), and the Southern Most Rift (SMR) where well-documented damage-causing earthquakes are common [6]. Interestingly, secondary effect of earthquakes is slope movement there can be many different types of earthquake-induced slope movement. In addition to seismic hazard, substantial amount of the newly planned railway routes in the country pass in the heart of expansive soils. Expansive soils are cause of slope failures due to swell and reduction in strength. According to the previous case studies [2], Slope failures in Ethiopia are mainly controlled by the presence of soft and low permeability materials or shales. The brittle nature of the failure and the strain-softening are such that the peak strength measured in the laboratory cannot be used directly in limit equilibrium analyses. Moreover, wide coverage of overconsolidated soils with fissures was also identified during site investigations along the new railway routes [10]. In these types of soils, experience shows that conventional practice of testing only vertical samples can be misleading [7]. Since progressive failure can occur for soils with brittle stress-strain characteristics, peak strengths should not be used for these soils in limit equilibrium analyses;using peak strengths for brittle soils can lead to inaccurate and unconservative assessment of stability [7]. Both shallow and deep seated slope failures have been occurring in Ethiopia following prolonged and intensive rainfall. It was indicated that drainage is the principal measure used in the repair of landslides, with modification of slope geometry the second most used method [23]. The judicious choice of alignment can minimize the severity of the problem due to expansive soil, if good reconnaissance surveys are made [31]. For example, if the alignment can be adjusted problems may be mitigated by such approaches as minimizing cuts and areas of poor drainage. ]. Or it can be subsequently recompacted with good moisture and density control to minimize the expansion potential. Risk mitigation is the final stage of the risk management process and provides the methodology of controlling the risk. At the end of the evaluation procedure, it is up to the client or policy makers to decide whether to accept the risk or not, or to decide that more detailed study is required [24] A GPS landslide monitoring system can be used to notify approaching trains if the ground movement is exceeding a threshold that rendered the track impassable.

• 出版日期2016
• 单位三峡大学