ABSTRACT
Every nation strives hard to achieve economic development for which adequate infrastructure is required to accomplish the desired goals. In mountainous terrain, road and highway networks play an important role for transportation, public conveyance and other socio-economic activities. Infrastructure development in hilly areas warrants excavations for the construction or road widening purpose undermining the stability of the slopes. The unplanned excavations of Tertiary rock slopes for construction and/or widening purposes before the political unrest in and around Taiz city have caused the instability of the slopes and thus threatened the very purpose of achieving the economic development. In the present work, evaluation of the stability of 12 rock slopes along road cuts and natural outcrops in and around Taiz city was carried out, employing the Landslide Possibility Index (LPI) system. The results showed that the possibility of failures and the degree of hazard in one rock slope location (No.25) is ‘Moderate’, while in the eight rock slope locations (Nos. 15, 16, 17, 20, 22, 23, 24 and 26) are ‘High’. The possibility of failure in the slope location Nos. 18 and 19 are ‘Very High’ while in the location No. 21 is ‘Low’. The areas of‘Moderate Hazard’ are represented by granite and jointed rhyolite /dacite rockswhile the slopes of ‘High Hazard’ are represented by different lithologies. The remedial measures for 12 slope locations are suggested based on the degree of possibility of failure and field observations. The intensive field studies indicate that the various causal factors in addition to rainfall have a bearing on causing the instability along the rock slopes of the study area.
