http://ir.bdu.edu.et/handle/123456789/10265 2001-01-13T05:52:06Z http://ir.bdu.edu.et/handle/123456789/16622 SLOPE STABILITY ANALYSES OF RAINFALL INDUCED LANDSLIDE THE CASE OF REBUGEBEYA-TAMAWITE ROAD, GANKE KEBELE, ETHIOPIA WUBSHET, BANTEGIZIE Rainfall induced landslides have become a cause for loss of life; they also obstruct traffic flow, which ultimately limits the road serviceability level and has an effect on the economy. This thesis includes detailed site and laboratory investigations for the selected failed cut slope sections on the Rebugebeya-Tamaweite road in Ganke Kebele to understand the rainfall induced slope failure using PLAXIS 2D. Along the selected failed slope locations, representative disturbed and undisturbed soil samples were taken from four selected test pits based on the slope angle and the material forming the slope through field observations. Laboratory tests were conducted to determine the index and engineering properties of the soil in the selected slope sections. Following the characterization and classification of the failed slope by detailed investigation and soil laboratory testing, the input parameters were determined for the analysis of the failed slope by PLAXIS 2D. The slope forming soil materials along the failed slope are classified as MH (silt with high plasticity) as per the USCS. It was observed that the road is highly affected by slope instability problems with a circular/rotational mode of failure. The factor of safety (FoS) for the identified slope failure was determined using the Finite Element software, PLAXIS 2D, modeled using Mohr-Coulomb failure criteria based on the strength reduction approach. The mesh and parameter sensitivities were conducted in order to understand the sensitive parameters affecting the slope stability. The result of the stability analysis of the slope for the initial conditions gives a FoS of 1.313. However, under rainfall loading conditions, the FoS reduced to 1.191. This shows that slope instability increases when rainfall infiltrates the slope, which is in line with the failure of the slope in the study area. Further, to reduce the instability of the slope in the study area, slope geometry modification, bamboo reinforcement, vegetation practice, retaining wall, and proper drainage have been recommended as remedial solutions to prevent failure of the existing slopes near the failed slopes. Keywords: rainfall induced landslide, failed slope, PLAXIS 2D, slope stability, factor of safety, strength reduction approach, Sensitivity 2024-09-01T00:00:00Z http://ir.bdu.edu.et/handle/123456789/16621 Improvement of Geotechnical Properties of Expansive Soils using calcined waste marble and chamotte waste Haileysus, Acha Demissie 2024-08-01T00:00:00Z http://ir.bdu.edu.et/handle/123456789/16620 Assessing the Causes of Road Failures along Bahirdar to Woreta Road Section Habtam, Misgan Highways play a crucial role in facilitating transportation and have a significant impact on the economic development of a country. The current condition Bahirdar –Woreta road of the road segment was subjected to heavy defects. As a result of flooding and erosion raveling was the dominant problem from Hamusit to Woreta town, which cause the pavement to lose functioning. In addition to this due to increase in traffic volume and different factors including inappropriate maintenance techniques the rates of deterioration increase rapidly. The Aim of this research was to study assessment of road failures from Bahirdar to the Woreta road segment. Road defect type, Severity level, and causes of failure are investigated. The road condition survey result indicates that most of the defect from Gombat to Woreta town has low severity with high extent of deterioration. The study focused on taking representative samples from six different failed sections of the road for both natural sub-grade soil, sub base and base coarse materials for laboratory testing the liquid limit value of the subgrade ranges from 44.3 % to 97.23 % and subbase also ranges from 21.5 % to 38.2 %. The range of the plasticity index result for sub-grade is 19.65 % to 49.45 % and the range of the plasticity index result for subbase is 4.3 % to 19.15 %. OMC sub grade from 16.9-30.5% and Sub-base material 12.5-21.5%, whereas MDD ranges sub-grade soil is from 1.28-1.84 g/cm3 and sub-base material 1.26-2.02 g/cm3. CBR values of the subgrade range from 1.51 % to 6.73 % and sub base 18.3% to 47.6 %. Based on the result of ACV and LAA all samples are below the requirements (ACV < 25 and LAA < 30). The subgrade soil is classified as A7-6 and A-7-5.and sub base A-2-4 and A-6. The study area also suffers from poor drainage and the expansiveness of the sub grade soil varies from high to very high. Therefore, a number of factors including traffic loads, expansive subgrade, inadequate side drains, poor workmanship and the use of inferior construction materials contribute to pavement failure. Keyword: - Highways, Road Failure, Compaction, CBR Test, Design Standards 2024-10-01T00:00:00Z http://ir.bdu.edu.et/handle/123456789/16619 STABILITY ANALYSIS OF RAINFALL INDUCED LANDSLIDE: A CASE STUDY ON ADDIS ZEMEN-GONDER ROAD AROUND TARA GEDAM Bogale, Senay Amare Slope instability is common in Northern and Central parts of Ethiopia. The topographical nature of Northern part of Ethiopia is mountainous with high slope. The most cause of slope instability in Northern parts of Ethiopian is rainfall. Roads along Abay Gorge, Dese, Wudemen, Mersa and Wurgessa areas are mostly affected due to rainfall-induced landslides. Tara Gedam is found in Northern part of Ethiopia, which was affected by rainfall-induced landslide in August 2020. Landslide in Tara Gedam area affected transportation, embankment of road, agricultural products, forest and nature of land. This study identified the source of problem and analyzing slope stability using SLOPE/W and PLAXIS 2D to give appropriate mitigations. For this study, soil samples, surveying data and rainfall condition were taken to do slope stability analysis of Tara Gedam area. Soil parameters were determined from laboratory but properties of rock and concrete were taken from different literatures. The soil sample was taken from five pits and it is classified as silty sand for pit No. 1 and 2 and elastic silt with sand for pit No. 3, 4 and 5 and characterized as poor drainage condition at all pits. A soil and rock parts were modeled using Mohr- Coulomb and Hoek-Brown models respectively. Slope failure of Tara Gedam area was analyzed with varying of rainfall duration of time and intensity using SLOPE/W and PLAXIS 2D. Using fully coupled flow-deformation analysis for PLAXIS 2D, a factor of safety was calculated based on strength reduction method and the value of factor of safety was decreased as increasing of rainfall duration of time and intensity. A factor of safety was also calculated using SLOPE/W and the value of factor of safety was decreased for increasing of intensity and duration of rainfall. The factor of safety during the rainy season shows significant reduction from its initial dry state value of 1.69 to 1.06 after 2-day rainfall duration using SLOPE/W. A factor of safety was also decreased from 1.86 at dry season to 1.00 after 2 days rainfall using PLAXIS 2D. The slope becomes stable when trench excavation and drainpipes are constructed. Keywords: Slope Stability, LEM, FEM, Rainfall and Tara Gedam area 2024-09-20T00:00:00Z