The Rhuallt Hill Rock The Rhuallt Hill Rock Cutting Cutting

North WalesNorth Wales

Alun RobertsAlun Roberts

Pejman KeikhaPejman Keikha

IntroductionIntroduction

• A 1km long downhill section of the A55 A 1km long downhill section of the A55 North Wales coastal road. North Wales coastal road.

• Allowing traffic to enter and leave the Vale Allowing traffic to enter and leave the Vale of Clwyd.of Clwyd.

• Consists of 2 deep rock cuttings as well as a Consists of 2 deep rock cuttings as well as a large embankment across the valley floor.large embankment across the valley floor.

IntroductionIntroduction

• The height of the cuttings vary up to 27m.The height of the cuttings vary up to 27m.

• The roadway curves through the hillside The roadway curves through the hillside avoiding a potentially intrusive notch in avoiding a potentially intrusive notch in the landscape. the landscape.

• The slope of the cuttings vary from a The slope of the cuttings vary from a graded out 1:2 at the top to a near vertical graded out 1:2 at the top to a near vertical 1:5 slope at road level.1:5 slope at road level.

Geological AspectsGeological Aspects

• The cutting was cut through a monotonous The cutting was cut through a monotonous sequence of mudstones and siltstones of sequence of mudstones and siltstones of the Nant-Y-Glyn flags of Silorian agethe Nant-Y-Glyn flags of Silorian age

• The strata generally dip at about 25The strata generally dip at about 25° along ° along the line of the cutting.the line of the cutting.

• Several transverse faults intersect the Several transverse faults intersect the cutting and local discontinuities have cutting and local discontinuities have adverse dips and orientations.adverse dips and orientations.

Rock Face Stabilisation Rock Face Stabilisation MethodsMethods• Rock AnchorsRock Anchors

– 650 No650 No

– Lengths up to 23mLengths up to 23m

– Monobar Rock Monobar Rock AnchorsAnchors

– Multistrand Rock Multistrand Rock AnchorsAnchors

Rock Face Stabilisation Rock Face Stabilisation MethodsMethods• Rock BoltsRock Bolts

– Mechanically Mechanically Anchored Rock Anchored Rock BoltsBolts

– Resin Anchored Resin Anchored Rock Bolts Rock Bolts

Rock Fall Protection Rock Fall Protection MeasuresMeasures

• Rock Catch DitchRock Catch Ditch

• Barrier FenceBarrier Fence

Thank you for listeningThank you for listening

Any Questions?Any Questions?