Engineering geology of the Agaba-Ras El Naqab highway re-alignment, Jordan

A detailed geological investigation was conducted along the section of highway between Station 00 and Station 88 km of the proposed Aqaba to Ras El Naqab highway in Jordan including the Ras El Naqab Escarpment (Station 75–80 km). The Escarpment area is characterized by soil-rock slope failures, and a complex geological pattern of rock units and faults in a rugged terrain. ological sequence along the highway alignment consists initially of the Kurnub Sandstones Group and mainly within the Upper and Lower Ajlun Formations. The mechanics of movements associated with the Kurnub Sandstone Group include erosion and toppling of sandstone blocks where undercut. Movements manifested within the Upper Ajlun Formation are due to the opening of joints, formation of gulls, cambering, toppling, sliding, rockfalls and the dislocation of limestone blocks. These slope failures associated with the Lower Ajlun Formation are relatively small while large-scale movements and slips occur within the marl and clay. extensive slope stability analyses were performed an alignment for the proposed road, including the Escarpment stretch was selected, that also included any special construction considerations. locations were selected for the detailed slope stability analyses; initially the critical soil parameters were determined assuming that the slopes are marginally stable. Alternate measures for the stability were then considered and the relative effects on the safety factor were analyzed to determine optimum solutions for locating the proposed road. commended alignment is situated adjacent to the existing road and located on the west up to Station 75 + 000 km and from Station 76 + 000 km to Station 79 + 700 km. Between Station 75 + 000 km and Station 79 + 700 km to the crest of the Escarpment the new alignment is located east of the existing road. criteria adopted for slopes constructed within the Upper Ajlun Formation include protection of exposed marl and clay slopes, sealing of open joints and fractures within the limestone and minimizing the surface areas of marls and clays in slope faces. Criteria for design of slopes within the Lower Ajlun include those presented for the Upper Ajlun as well as proper design of slope angles, placement of interceptor drains, and specific construction techniques to be adopted where mantle creep is anticipated. Features associated with the Kurnub Sandstones require the installation of surface drainage measures as well as revetment techniques to prevent encroachment of rock-block falls onto the highway or into drainage channels.