Modeling of landslide occurrence in the hilly areas of Bududa District, Eastern Uganda

• Main Author: Nelson, Okello
• Format: Thesis
• Language: English
• Published: 2015
• Subjects: TA Engineering (General). Civil engineering (General)
• Online Access: http://eprints.utm.my/id/eprint/53918/25/OkelloNelsonMFKA2015.pdf; http://eprints.utm.my/id/eprint/53918/; http://dms.library.utm.my:8080/vital/access/manager/Repository/vital:85685

The purpose of this study was to model landslide occurrence (LO) in the hilly areas of Bududa District taking to consideration the effect of commonly known causative factors and an uncommon landslide causal factor of wind forces on slope with eucalyptus trees. Five different slope models, without and with additional shear strength infrom of tree root cohesion have been use to obtain the final results of LO, with all subjected six (6) different failure criteria (FC). The first four failure criteria (FC1, FC2, FC3 and FC4) assumed were for; group of trees on the slope, tree at the top, tree in the middle and tree at the toe of the slope , while FC5 and FC6 were for slope models with rainfall infiltration only and rainfall plus group of tree weight respectively. Beaufort wind scale 11 was used, and Tree Diameters at Breast Heights (DBH) were varied, commencing with 25cm, 30cm and 60cm for assumed eucalyptus tree height of 25cm. The additional shear strength due to an increased cohesion from the roots ( was assumed, on the top soil layer of silty clay. Finite element analysis with SEEP/W 2007 was coupled with Limit equilibrium analysis software of SLOPE/W 2007 to achieve expected output or results from different failure criteria. Initial suction of 50kPa at the top of silty clay and 20kPa in the layer of silty gravel, with a total 1044 generated deformed mesh boundary condition were used in transient seepage analysis. Slope model 1 with eucalyptus trees of DBH 25cm yielded an output minimum factor of safety (FOS) of 1.012 for FC3 and value of 1.253 for FC3 (an increase of 23.81% from slope model 4), without and with increased cohesion respectively. With DBH increased to a maximum of 60cm, for slope model 3, safety of the community around this site diminished as the FoS reduced to 0.562 with FC2 and 0.601 with FC3 on day 25, without cohesion, just hours before the fateful day on the 26th June 2012 and remained below 1.0 (from 0.601 to 0.800) with FC3 with roots cohesion, although a gain in the FoS of 33.11% was realized.