Glossary · 66
Rockfall and slope
glossary.
Short definitions of the terms used in our answers, specifications and reports — barrier certification, mesh systems, rock mechanics, survey and debris flow.
Barriers and certification
- Flexible barrierالحاجز المرن
- A rockfall protection structure of steel ropes and net that dissipates impact energy by deforming. Certified under EAD 340059 with MEL and SEL values.
- MEL — Maximum Energy LevelMEL — مستوى الطاقة الأقصى
- The maximum energy a barrier stops in a single impact; the system is repaired afterwards. Declared in kJ in the certificate.
- SEL — Service Energy LevelSEL — مستوى طاقة الخدمة
- The energy level at which two consecutive impacts are stopped without maintenance in between; MEL is at least three times SEL.
- Energy classفئة الطاقة
- The certified energy level of a barrier from the full-scale impact test (classes 0 to 8). The kinetic energy of the design block, multiplied by a safety factor, is compared with these levels.
- Nominal heightالارتفاع الاسمي
- The smallest distance between the line of the post bases and the upper support rope, perpendicular to the reference slope, before impact. Chosen from the bounce height.
- Residual heightالارتفاع المتبقي
- The free height left in the barrier after the impact test, measured with the block still in the net; declared as category A, B or C in the Declaration of Performance.
- Maximum elongationالاستطالة القصوى
- The distance the net travels downslope in the MEL impact; it fixes the clearance between the barrier line and the protected asset.
- Bounce heightارتفاع الارتداد
- The height at which a block leaves the ground at the barrier line; the barrier height is chosen from this value, not from the energy calculation.
- Design blockالكتلة التصميمية
- The block the calculation is built on; chosen from the upper tail of the block-size distribution measured on site. The largest and the most frequent blocks are assessed separately.
- Brake elementعنصر الكبح
- An energy absorber connected in series with the rope line that deforms in a controlled way at impact.
- Support ropeالحبل الحامل
- The upper and lower ropes that carry the net between the posts and transfer the impact load to the anchors.
- Base plateصفيحة القاعدة
- The plate connecting the barrier post to its foundation, usually hinged, so that the post rotates in a controlled way at impact.
- Catch ditchخندق التجميع
- A ditch at the toe of the slope that collects blocks; it has no certified energy class — its performance is defined by width, depth and base slope.
Mesh systems
- Ring netالشبكة الحلقية
- A high-energy net panel woven from interlocking steel wire rings.
- High-tensile meshالشبكة عالية المقاومة
- Steel mesh woven from wire of 1,770 N/mm² tensile strength; gives the same capacity as ordinary woven wire with a much lighter section.
- Double-twist hexagonal meshالشبكة السداسية مزدوجة الجدل
- Galvanized steel wire mesh with hexagonal openings and double-twisted joints to EN 10223-3; used for drapes and gabions.
- Drape meshشبكة التغطية
- A passive system hung from the crest only; it keeps a detached block close to the surface, slows it and delivers it to the toe.
- Anchored meshالشبكة المثبّتة بالمراسي
- An active system pressed to the face with anchors; it holds the mass expected to slide and transfers the load into the ground.
- Attenuatorالستارة المخمّدة
- A net curtain hung from the top with a free lower edge; it slows and guides a block instead of stopping it.
- Pre-tensionالشدّ المسبق
- The force applied to the mesh through the plate at the nail head; it presses the layer to the ground. In the calculation its favourable effect is reduced and its unfavourable effect increased by factors.
- Puncturing resistanceمقاومة الثقب
- The capacity of the mesh to resist pressure in the nail direction around the nail head and plate; one of the anchored-mesh checks, read from the product certificate.
- Plate-edge shearالقصّ عند حافة الصفيحة
- The wedge forming between nails forcing the mesh over the upper edge of the plate; often the governing local check in anchored-mesh design.
- Pressure coneمخروط الضغط
- The assumed cone below the plate in which the pre-tension spreads into the ground; its top radius and inclination narrow the local instability body between nails.
Rock mechanics and stability
- Surface-parallel slidingالانزلاق الموازي للسطح
- Sliding of the soil cover or weathered rock crust along a plane parallel to the slope face; the shallow failure mode anchored-mesh systems are designed for.
- Discontinuityالانقطاع
- A mechanical weakness surface in the rock mass — joint, bedding plane, fault.
- Discontinuity orientationاتجاه الانقطاع
- The dip and dip direction of a discontinuity surface; the basic input of kinematic analysis and of the failure-mode distinction.
- Discontinuity spacingتباعد الانقطاعات
- The perpendicular distance between neighbouring discontinuities of the same set; it fixes the in-situ block size.
- Persistenceالاستمرارية
- The length over which a discontinuity can be traced on the face; it fixes the rock-bridge ratio and whether a block is really free.
- Kinematic analysisالتحليل الحركي
- Comparison of discontinuity orientations with the slope face to determine which failure modes are geometrically possible.
- Planar slidingالانزلاق المستوي
- Sliding of a mass along a single discontinuity surface oriented close to the slope face.
- Wedge failureالفشل الإسفيني
- Sliding of a wedge-shaped mass along the line of intersection of two discontinuities.
- Topplingالانقلاب
- Failure of columns separated by steep discontinuities dipping into the slope, rotating about their base.
- Daylightingالظهور على الواجهة
- A discontinuity or the intersection line of two discontinuities emerging from the slope face; the geometric precondition for planar and wedge sliding.
- Friction angleزاوية الاحتكاك
- The angle of resistance to sliding on a discontinuity surface; chosen as the sum of basic friction and the roughness contribution.
- Factor of safetyمعامل الأمان
- The ratio of resisting to driving forces; above 1.0 is stable.
- Partial safety factorمعامل الأمان الجزئي
- Material, load and model uncertainty taken into account with separate factors; design effect is compared with design resistance instead of one global number.
- Rock mass classificationتصنيف الكتلة الصخرية
- Rating of the rock by discontinuity condition, strength and water (RMR, Q, GSI); the first step of choosing support type and density.
- Stereonetالشبكة المجسّمة
- A diagram showing discontinuity orientations by spherical projection; sets and kinematic checks are read on it.
- Scalingالتقشير
- Controlled removal of loose blocks from the surface; on its own it is not permanent protection and does not stop weathering.
- Seepage forceقوة التسرّب
- The volumetric force that slope-parallel groundwater flow exerts on the ground; in a fully saturated layer γw·sin α per unit volume, entering the anchored-mesh calculation as a driving load.
- Submerged unit weightوزن الوحدة المغمور
- The unit weight of ground under water reduced by buoyancy (γ − γw); weights in the seepage load case are calculated with it.
Survey and trajectory
- Block-size distributionتوزيع أحجام الكتل
- The volume distribution of blocks measured on site; the design block is taken from it as a percentile.
- Trajectory analysisتحليل المسار
- Simulation of falling blocks on the measured slope profile; gives impact speed, energy and bounce height at the barrier line as percentiles.
- Restitution coefficientمعامل الارتداد
- The share of speed conserved in an impact; normal and tangential components chosen by surface type and calibrated by field observation.
- Fall lineخط السقوط
- The steepest descent direction on the slope surface; it fixes the path a block follows and the direction of the protection line in plan.
- Runout distanceمسافة الوصول
- The horizontal distance a falling block travels from the source to where it stops; used to calibrate simulation parameters on site.
- Shadow angleزاوية الظل
- The angle to the horizontal of the line joining the top of the talus to the farthest stopped block.
- Energy lineخط الطاقة
- A simplified approach that represents energy loss by the inclination of the line joining the source point and the stopping point.
- Back analysisالتحليل العكسي
- Calibration of model coefficients from a real event — a stopped block, an impact mark; trajectory and friction parameters are verified this way on site.
- Point cloudسحابة النقاط
- A set of coordinated points representing a surface; sections, areas, volumes and discontinuity orientations are read from it.
- Photogrammetryالمسح التصويري
- Producing a scaled three-dimensional surface and point cloud from overlapping photographs; scale and orientation are given by ground control points.
Debris flow and landslides
- Debris-flow barrierحاجز التدفّق الركامي
- A flexible steel barrier across a channel that lets water through and retains solid material.
- Retention volumeحجم الاحتجاز
- The solid volume a debris-flow barrier can hold before it is full; the number of barriers and their staging are chosen from the estimated solid volume.
- Shallow landslide barrierحاجز الانزلاق الضحل
- A flexible barrier installed to retain cover material that starts moving at shallow depth on a hillside.
Materials, anchors and access
- Anchorالمرساة
- A steel element placed in a drilled hole and bonded with grout that transfers load into sound ground.
- Rock boltالبرغي الصخري
- A steel bar, usually grouted, that stitches the rock mass and holds discontinuity surfaces together.
- Galvanized coatingالطلاء المجلفن
- A zinc-based coating protecting the steel surface from corrosion; the class is chosen by the corrosivity of the environment and the target service life.
- Corrosivity categoryفئة التآكل
- The classification of how aggressive the environment is; coating choice and the declared service life are tied to it. Oman's coastal sites fall in the higher categories.
- Rope accessالوصول بالحبال
- Carrying out the work with a rope system on steep faces where scaffolding and platforms cannot be built; the access method also decides what can be measured.
- Erosion-control matحصيرة مكافحة التعرية
- A mat that holds the soil on the slope surface and lets plant roots take hold; usually applied together with hydroseeding.
- Gabionالجابيون
- A flexible retaining and erosion structure built from steel-mesh baskets filled with stone.
Documents and testing
- Pull-out testاختبار الشدّ
- A loading test that measures the bearing capacity of an installed anchor on site; the test regime depends on the anchor type.
- Declaration of Performanceإعلان الأداء
- The document in which the manufacturer states which energy levels, nominal height and residual-height category the product provides.
- EAD 340059-00-0106EAD 340059-00-0106
- The European Assessment Document for flexible rockfall barriers; it replaced the April 2013 ETAG 027 guideline and keeps the full-scale impact test.
- EAD 230025-00-0106EAD 230025-00-0106
- The European Assessment Document for flexible facing systems for slope stabilization; it declares mesh geometry, plate, mechanical resistances, connection strength and durability.
- Bill of quantitiesجدول الكميات
- The work expressed in measures: barrier line length in metres, mesh and drape area in square metres, anchors and connectors in numbers.
Send us your slope.
Share the site and we will assess the hazard, recommend a system and return a costed proposal — engineering-led, no obligation.