An assessment of stability measures chosen to stabilise rock cuttings in Precambrian rhyolite and Upper Carboniferous Coal Measures in Shropshire and West Glamorgan, United Kingdom, respectively is presented. The paper comments upon the analyses performed in assessing the stability of the cuttings rock slopes and the different approaches that were required in the design of stability measures. The design of stability measures included methods for stabilising local areas of potential instability such as rock bolts and dowels for unstable blocks, buttress walls for completely weathered master joints within shear zones and geotextile reinforcement for overburden above the rock slopes.


Cet article presente une evaluation des mesures choisies pour stabiliser des tranchees dans des roches telles que la rhyolite du precambrien et les couches du carbonifère Superieur respectivement du Shropshire et du West Glamorgan en Grande Bretagne. L'article commente les analyses effectuees pour, evaluer, la stabilite des parois rocheuses de tranchees ainsi que les differentes approches necessaires lors de la conception des mesures de stabilisation. Le proget de mesures de stabilisation etudie differentes methodes pour stabiliser des zones precises à potentiel d'instabilite. Ces procedes sont l'usage de gougeons et de boulons d'ancrage pour les blocs instables, la construction de murs de contrefort pour les joints principaux desagreges dans les zones de cisaillement et l'emploi de geotextiles pour renforcer les couches de sols au dessus des paroies rocheuses.


Es liegt eine Beurteilung der gewahlten Stabilitatsmessungen zur Stabilisierung von Felsaushub im prakambrischen Rhyolit und den Kohleschichten des Oberkarbon jeweils in Shropshire und in West Glamorgan, Groβbritannien, vor. Der Bericht kommentiert die durchgefuehrten Analysen bei der Bewertung der Stabilitat. Von Felshangen der Aushuebe und die unterschiedlichen Ansatze, die bei der Erstellung der Stabilitatsmessungen erforderlich waren. Die Stabilitatsmessungen umfaβten Methoden zur Stabilisierung örtlicher Bereiche potentieller Instabilitat wie z.B. Felsnagel und Duebel fuer instabile Blöcke, Felsvorsprungwande fuer vollstandig verwitterte Hauptkluften in Scherzonen und geotextile Verstarkungen fuer Deckgebirge ueber den Felshangen.


The rock cutting at Overley Hill is situated west of the M54 terminus at Cluddley on the A5 Improvement between Telford and Shrewsbury approximately 2 km west of the town of Wellington, Shropshire, UK (Figure 1). The cutting is approximately 500 m in length and has been constructed through glacial sand and gravel, boulder clay and Precambrian rhyolite. The Earlswood Rock Cutting forms part of the western extension to the M4 motorway 2 km west of Neath, West Glamorgan (Figure 1). The cutting is approximately 400 m long with a maximum depth of 35 m in the Upper coal Measures.


Overley Hill is an inlier of rhyolite, dated from zircon within the rock at 566 ± 2 Ma, which is bordered on its western and eastern slopes by the Brockton and Burcot Faults (continuations of the Church Stretton Fault) respectively. Coed-yr-Allt (Upper Coal Measures) sandstone and mudstone forms the low lying ground surrounding Overley Hill. Faults master joints within the Precambrian rock strike in a north north-east to south south-west direction which is parallel to the prevailing direction of major folds and faults within Shropshire. Natural ground water is at the interface of the rhyolite and the overlying boulder clay. The geology of the Earlswood area in that of rhythmically deposited sediments of the Pennant Measures (Upper Coal Measures). These rocks comprise sandstones, mudstones and siltstones of a fluviatile origin with occasional coals and seat earths. The sequence forms part of the southerly limb of the synform which forms the South Wales Coalfield, and as such the dip is generally northwards at approximately 30°.

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