Grown wall

Thin steel strips in a grid, seawater, current. Limestone grows on the steel until it is a wall. Two years to grow, then it is rock. Billed per statute mile.

peer-reviewed published   field measured on a real install   derived this site   input your choice

One mile of sandbar — full design

  1. Ours: $3M steel, power, anchors. Not priced: barge, divers, anodes, rectifiers, cable, permits.
  2. Rock mound: $7.5M installed. field USACE Mordecai Island 2022.
  3. Wave through: ours 0%, rock 26%. peer-reviewed Kriebel 1992 · d’Angremond 1997.
  4. Material: ours 5,400 t, rock 116,000 t.
  5. Energy: 4 GWh to grow, 260 kW for two years. After that 95 kW, 14 kW, or off — your choice below.
  6. Unknown: install cost; whether the limestone holds the wave with no steel. One panel test answers the second.

Single wall calculator

One porous wall, finished 20% open, half the wave through (Kt 0.5). Choose the sea and the prices; the page finds the cheapest strips. The electrolysis and price choices here are also used by the sandbar wall.

Sea and life

Electrolysis and prices — shared with the sandbar page

Steel 100 MPa allowable, AISC F11 buckling. Limestone carries no load unless you give it a tensile strength. Type strips to see that design; change anything else and it re-searches.

The cage is a grid of steel strips; the finished wall must be 20% open. Grow more limestone on each strip and the grid can be coarser, so fewer strips, less steel, fewer anchors. Cost falls to the right until electricity and grow time take over. Thickness is time: about 2 cm per year per side at 1.5 A/m², so the lower axis shows years. Ring: the design in the boxes above. Lines: strip depth (front to back).

Against the state of the art

Published $/ft × 5,280, installed. Our bar: build cost to kept-alive total, no install. Different structures, different seas — the sandbar page runs our wall at one built project’s exact conditions.

Structure$ per mileBasis

What we learned

Six things the calculators taught us

  1. Anchors set the price, and thin is not cheap. 2 mm strips span ~1 m and need ~9,000 anchors a mile; 5–6 mm × 200 mm strips span 3–4 m and need ~1,000. The optimiser lands on thick strips for that reason. derived steel-only bending, AISC F11 buckling.
  2. Day one is the light-load day. A bare grid is ~95% open; the wave goes through and the anchors see almost nothing. The load arrives as the holes close to 20%. The page sizes anchors for that finished wall, so the count is right for year two and conservative for year zero.
  3. The limestone can carry the wave. Give it 1 MPa tensile (C20/25 design value) and the cheapest mile drops ~30%: the optimiser thins the steel to a scaffold and lets the rock carry bending between anchors. Anchor count barely moves; steel nearly disappears. Untested — no tensile or bond data exists for grown mineral, and nothing checks a 0.5 mm bare cage surviving handling. Set it in the calculator.
  4. Thickness is time. At 1.5 A/m² and 73% of Faraday the skin grows ~2 cm/yr per side. Faster current makes brucite, which flakes and dissolves. field EUDP 5052-0010 · peer-reviewed Sharker 2023.
  5. Electricity is the small bill at 73% of Faraday: ~$0.5M of a $3M mile. field Cuba 0.4–0.5 kg/kWh at 6 V (Goreau 2012).
  6. Power after growth is a choice. 0.55 A/m² keeps growing; 0.08 A/m² protects the steel (DNV-RP-B401); off works only if the limestone holds alone — the one panel test worth doing.

Where the numbers come from: Physics (accretion rates, Kriebel wave check, every constant with its source). Two-cage chamber wall for a bar: Sandbar. What rock costs and does: Rock. The one prior electrolytic shore job: History.

Sources for the benchmarks