{"id":12832,"date":"2026-09-16T15:12:55","date_gmt":"2026-09-16T15:12:55","guid":{"rendered":"https:\/\/www.raxpower.com\/?p=12832"},"modified":"2026-09-19T18:44:25","modified_gmt":"2026-09-19T18:44:25","slug":"%d8%af%d9%84%d9%8a%d9%84-%d8%a7%d8%ae%d8%aa%d9%8a%d8%a7%d8%b1-%d9%85%d8%b1%d8%a7%d8%b3%d9%8a-%d8%a7%d9%84%d8%aa%d8%b1%d8%a8-%d8%a8%d8%a7%d9%84%d8%af%d9%82","status":"publish","type":"post","link":"https:\/\/www.raxpower.com\/ar\/blog\/percussion-earth-anchor-selection-guide\/","title":{"rendered":"\u0627\u062e\u062a\u064a\u0627\u0631 \u0645\u0631\u0627\u0633\u064a \u0627\u0644\u062a\u0631\u0628\u0629 \u0627\u0644\u0627\u0631\u062a\u062c\u0627\u062c\u064a\u0629: \u0627\u0644\u062d\u0645\u0644 \u0645\u0642\u0627\u0628\u0644 \u0627\u0644\u062a\u0631\u0628\u0629"},"content":{"rendered":"

Every percussion earth anchor<\/a> catalog prints a holding number long before anyone touches the ground: 300 pounds here, 5,000 pounds there, 40,000 on the heavy page. Each of those figures assumes a specific soil, and the soil at your pole location never agreed to the assumption. Selecting a driven anchor is therefore a two-variable decision \u2014 the load the guy must carry and the soil profile that has to resist it.<\/p>\n

Our order desk sees the mismatch in reverse. Inquiries arrive with a guy load and a pole count but no soil line item. The duckbill that held a distribution guy in one region's stiff clay then refuses to enter the loose fill a hundred miles down the route. The selection path below closes that gap: soil class first, anchor family second, load rating third, proof test last.<\/p>\n

What Counts as a Percussion Earth Anchor<\/h2>\n

A percussion earth anchor is installed by impact, not by torque. A drive rod slides over the anchor's pilot pin, a sledgehammer or jackhammer strikes the rod until the anchor reaches depth, and the rod is withdrawn. Under the first sustained pull, the anchor rotates into a bearing position against undisturbed soil \u2014 the way you would swing a toggle bolt open behind a wall panel.<\/p>\n

The family covers four working types on most utility catalogs. Slim bullet and arrowhead anchors carry cable or rod terminations for guy loads, while duckbills toggle open under tension at light-duty ratings. Manta Ray plates are driven flat, then locked at depth for heavy guy loads. If your line uses torqued helixes or grouted rods, you are in a different family. Those screw and grouted types follow another selection logic, covered in the common types of earth anchors overview<\/a>.<\/p>\n

Impact installation is the family's defining advantage and its defining constraint. There is no auger to clog, no torque meter to watch, and no spoils to haul. But the anchor accepts whatever soil it is driven into, so the selection decision moves almost entirely to the front: know the soil before you choose the steel.<\/p>\n

Why Soil Class Sets Holding Capacity<\/h2>\n

Soil class is the backbone of anchor selection. Manufacturers grade ground from class 1 (very dense, cemented) down to class 8 (swamp and organic silt). The labels rest on probe torque and the SPT blow count N per ASTM D1586. Class 4 ground is medium dense sand and gravel or very stiff clay, probing at 400 to 500 in-lb. Class 7 is loose fine sand, alluvium, and fill at 100 to 200 in-lb.<\/p>\n

Here is the fact most buyers miss: the rated capacity on a driven anchor's datasheet is not a property of the anchor. Federal design guidance rates the standard duckbill line \"in an average soil condition (class 5)\". The same guidance adds that classes above 5 deliver less capacity than the printed number, and denser classes can deliver more.<\/p>\n

Manufacturers publish a correction method for exactly this. NRCS Technical Supplement 14E divides the probe value of the actual soil by the class 5 average probe value, then multiplies the rated capacity by that ratio. The ratio scales on paper; the soil does not always cooperate. A percussion earth anchor punishes soil guesses harder than screw anchors do, because there is no torque reading to lean on.<\/p>\n

\n\"Excavated
Soil profile exposed for horizon classification<\/figcaption><\/figure>\n

Reading the Soil Classification Chart<\/h2>\n

Anchor catalogs express soil classes through three connected columns: a plain-language description, a probe torque band in inch-pounds, and a blow count band from the SPT hammer. Field crews probe at anchor depth, read the torque gauge, and take the class straight from the chart. The bands below follow the chart published for CHANCE anchor products and repeated in MacLean's expanding anchor bulletin.<\/p>\n\n\n\n\n\n\n\n\n\n\n
Soil class<\/th>\nCommon description<\/th>\nProbe torque (in-lb)<\/th>\nBlow count N<\/th>\n<\/tr>\n<\/thead>\n
3<\/td>\nDense sands and gravels; hard silts and clays<\/td>\n500\u2013600<\/td>\n35\u201350<\/td>\n<\/tr>\n
4<\/td>\nMedium dense sand and gravel; very stiff clays<\/td>\n400\u2013500<\/td>\n24\u201340<\/td>\n<\/tr>\n
5<\/td>\nMedium dense coarse sand; stiff silts and clays<\/td>\n300\u2013400<\/td>\n14\u201325<\/td>\n<\/tr>\n
6<\/td>\nLoose to medium dense sands; firm clays and silts<\/td>\n200\u2013300<\/td>\n7\u201314<\/td>\n<\/tr>\n
7<\/td>\nLoose fine sand; alluvium; fill; wet clays<\/td>\n100\u2013200<\/td>\n4\u20138<\/td>\n<\/tr>\n
8<\/td>\nPeat, organic silt, swamp, very soft clays<\/td>\nUnder 100<\/td>\n0\u20135<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Two practical notes belong next to the chart. First, hard rock classes sit outside percussion work entirely \u2014 class 1 and 2 ground usually demands drilled rock anchors instead. Second, seasonal water matters: the same sandy class 6 soil can behave like class 7 once saturated, so probe the route in the wet season when you can. Buyers planning exposed routes should also read the high-wind ground anchor selection guide<\/a>, where uplift demand peaks exactly when soil strength is least certain.<\/p>\n

Failure Modes: Soil Shear Versus Steel Yield<\/h2>\n

A driven anchor fails in one of two places, and honest datasheets mark which one governs each cell of the capacity table. Federal tables footnote every value as either anchor-strength-limited or soil-structure-limited. The first is a steel problem; the second is a ground problem.<\/p>\n

Soil failure comes first in weak ground. The anchor is strong, but the soil around it shears, and the plate drags upward through a plug of failing earth. This mode dominates in classes 6 through 8, and no catalog upgrade fixes it. Only a larger bearing area, more embedment, or more anchors per guy do.<\/p>\n

Structural failure comes first in strong ground, where the soil would hold far more than the anchor can transmit. There the limiter is the assembly rating: anchor plate, drive rod, and anchor rod must all carry the guy load. MacLean's expanding anchor bulletin reminds buyers that \"anchor load capacity may be limited by the rod rating\". A 5\/8-inch rod caps the assembly at 16,000 lbs-force no matter how hard the ground holds.<\/p>\n

By the time the rod stops ringing on a stubborn hole, the ground has already cast its vote. A refusal that leaves the anchor short of depth is a third, milder mode \u2014 treat it as a capacity warning, not a victory.<\/p>\n

Match Duckbill Models to Light Duty Loads<\/h2>\n

Duckbill anchors are the entry tier of the percussion earth anchor family, and their model ladder is the cleanest illustration of load-versus-soil selection. Each model is a slim, slotted anchor driven on a matching rod; under the first pull it pivots roughly ninety degrees into a bearing plate. Their official specification table is rated in class 5 soil, so every number below assumes that medium-firm ground.<\/p>\n\n\n\n\n\n\n\n\n
Duckbill model<\/th>\nRated capacity (lb)<\/th>\nDrive rod<\/th>\nNormal depth<\/th>\n<\/tr>\n<\/thead>\n
40<\/td>\n300<\/td>\n1\/4 in<\/td>\n20 in<\/td>\n<\/tr>\n
68<\/td>\n1,100<\/td>\n1\/2 in<\/td>\n2.5 ft<\/td>\n<\/tr>\n
88<\/td>\n3,000<\/td>\n3\/4 in<\/td>\n3.5 ft<\/td>\n<\/tr>\n
138<\/td>\n5,000<\/td>\n1 in<\/td>\n5 ft<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\n\"Duckbill
Duckbill models step up in size and rating<\/figcaption><\/figure>\n

Read the ladder as a package, not four separate products. Capacity rises tenfold from model 40 to model 138, but so does the drive rod weight and the hammer size, and the depth nearly triples. Crews pairing these anchors with rods and eye hardware should check the mating end first. The triple eye anchor rod field guide<\/a> covers how the rod side meets driven heads. Remember the trade, too: a duckbill is permanent once locked, so the unrecoverable selection error is a model chosen for a load that later grows.<\/p>\n

Manta Ray Anchors for Heavy Guy Loads<\/h2>\n

When the guy demand outgrows the duckbill ladder, selection moves to driven plate anchors. The Manta Ray line is the utility workhorse here \u2014 driven by jackhammer rather than augered or torqued, RUS approved, and installed with equipment that fits in a pickup bed. Every anchor is proof tested during standard installation, which gives the crew a measured tension number instead of a hope.<\/p>\n

The capacity table shows the same soil sensitivity as the duckbills, scaled up. In very dense fine sands and hard clays (blow counts 45 to 60), an MR-1 holds 36 to 40 kips. Drop the same model into loose fine sand or soft clays at 4 to 8 blow counts, and expected capacity falls to 8 to 12 kips. The table footnotes tell you why: dense-ground cells run out of anchor strength, soft-ground cells run out of soil.<\/p>\n

Assembly ratings complete the picture. The utility models carry ultimate ratings from 16,000 lbs (MR-3 on a 5\/8-inch rod) to 23,000 or 36,000 lbs (MR-1, MR-2, and MR-SR on 3\/4-inch or 1-inch rods). The full catalog table lives on the Manta Ray utility anchor specifications<\/a> page. Very hard caliche, glacial till, and permafrost sit within the installation range, though pilot holes may be required where penetration stalls.<\/p>\n

\n\"Manta
Manta Ray plate locks perpendicular under load<\/figcaption><\/figure>\n

Arrowhead and Bullet Anchors in Weak Soil<\/h2>\n

Arrowhead and bullet anchors fill the middle of the percussion earth anchor range: heavier than duckbills, faster than plates. Their published behavior confirms the soil-first rule from the other direction. One manufacturer's 8-inch aluminum arrowhead lists pullout strength at its minimum 4-foot installed depth. The same part holds about 1,250 lb in loose fine sand and up to 9,000 lb in hardpan \u2014 a sevenfold spread for identical steel.<\/p>\n

Weak soils change the installation arithmetic as much as the rating. In loose topsoil the anchor tends to deviate unless the crew keeps the rod plumb, and saturated silty sand can pump around the plate as it locks. The field details \u2014 pilot holes in hardpan, proof tensioning, avoiding rod deviation \u2014 are covered in the arrowhead installation guide<\/a> and the arrowhead field application guide<\/a>. Neither substitutes for the selection decision. In ground classified below class 5, plan on deeper embedment or a plate anchor rather than trusting a cable anchor's top rating.<\/p>\n

\n
\n

Sourcing the Percussion Range<\/h3>\n

Hot-dip galvanized duckbill, Manta Ray, arrowhead, and bullet anchors ship with the material certificates and proof-test documentation utility buyers expect.<\/p>\n

View the Ground Anchor Range<\/a>\n<\/div>\n

<\/div>\n<\/div>\n

Sizing Flow From Guy Load to Anchor Model<\/h2>\n

Selection compresses into a five-step sequence that a purchasing desk can run without a geotechnical engineer on staff:<\/p>\n

    \n
  1. Fix the design guy load at the anchor, including the safety factor your specification requires.<\/li>\n
  2. Classify the soil at anchor depth by probe torque or SPT blow count, and note the water table.<\/li>\n
  3. Shortlist the anchor family by class: duckbills for light loads in class 4 to 6 ground, Manta Ray plates for heavy guys, arrowheads where cable terminations suit.<\/li>\n
  4. Derate the catalog rating to the actual class, and check the rod rating governs the assembly, not the plate.<\/li>\n
  5. Schedule a proof test per anchor on acceptance, and keep the load locker reading with the delivery file.<\/li>\n<\/ol>\n

    In our experience, crews who probe the route before ordering buy once; crews who guess buy twice. Two boundary cases deserve a sentence each. Where the route alternates between clay knobs and sand stretches, treat every pole as its own soil site rather than averaging the route. And where a cross plate or deadman already exists on site, check the cross plate anchor guide<\/a> first. Do not buy hardware that duplicates capacity you already own.<\/p>\n

    Proof Load Before You Trust the Rating<\/h2>\n

    The last step converts a catalog number into a field fact. Federal guidance is blunt on this point. Driving resistance is \"a good indicator of its pullout capacity\", but \"proof-loading is the only way to ensure the exact pullout capacity of any soil anchor\". Larger installations use a hydraulic load locker that both sets the plate and measures the tension it reaches. The proof-tested value should be compared against design values before the guy hardware is signed off.<\/p>\n

    How much margin should the design carry? Factors of safety for anchored structures typically range from 1.5 up to 3.0. The low end assumes known soils and limited impact loads; the high end assumes thin data. A field split-spoon log and a probe reading justify the low end of that band. Guesswork pushes the design to the high end and taxes every anchor on the route.<\/p>\n

    Treat the proof test as a purchasing document, not just a crew ritual. Anchors supplied with batch traceability and hot-dip galvanizing to ISO 1461 hold their ratings through the seasons; anchors with no paper trail force you to re-verify every year. Specification discipline at ordering time is what makes the acceptance test a formality instead of a confrontation.<\/p>\n

    \n\"Opened
    Split spoon core confirms the blow count log<\/figcaption><\/figure>\n

    <\/p>\n

    Frequently Asked Questions<\/h2>\n
    \n

    Which soil class are percussion anchor ratings based on?<\/h3>\n

    Duckbill ratings apply to class 5 soil \u2014 medium-firm clay, loose standard gravel, or compacted coarse sand. Denser classes hold more, and looser classes hold less than the printed figure.<\/p>\n<\/div>\n

    \n

    How much does each duckbill model hold?<\/h3>\n

    Model 40: 300 lb at 20 inches. Model 68: 1,100 lb at 2.5 ft. Model 88: 3,000 lb at 3.5 ft. Model 138: 5,000 lb at 5 ft \u2014 all rated in class 5 soil.<\/p>\n<\/div>\n

    \n

    When do crews step up from duckbill to Manta Ray anchors?<\/h3>\n

    When guy loads exceed the 5,000 lb duckbill ceiling or soils turn tough. Manta Ray models carry ultimate ratings from 16,000 to 36,000 lbs and drive through caliche, glacial till, even permafrost.<\/p>\n<\/div>\n

    \n

    How far does soil class swing a driven anchor's capacity?<\/h3>\n

    Dramatically. The same Manta Ray holds 36 to 40 kips in very dense fine sand. In loose fine sand it holds only 8 to 12 kips \u2014 an identical anchor, a threefold spread.<\/p>\n<\/div>\n

    \n

    Do percussion earth anchors work in rock?<\/h3>\n

    No. Rock, loose fill, and highly organic soils sit outside the design range. In very hard soils a pilot hole may be drilled; swamp-spec models handle saturated ground.<\/p>\n<\/div>\n

    \n

    How is holding capacity verified after driving?<\/h3>\n

    Proof-load the installed anchor and compare the reading with design values. Driving resistance indicates capacity, but only a pull test confirms the exact pullout capacity.<\/p>\n<\/div>\n