gg5:【土木】 a sheet pile.
daijr: 建築の基礎工事や土木工事などで，土砂の崩壊または水の浸入を防ぐため，周囲に打ち込む板状の杭。木製，鋼製，鉄筋コンクリート製などがある。
https://www.collinsdictionary.com/dictionary/english/sheet-pile
one of a group of piles made of timber, steel, or prestressed concrete set close together to resist lateral pressure, as from earth or water

I think it's specifically sheet piling. All the kokugos say 板状.
A civil engineering tag might be useful.

@@ -12,2 +12 @@
-<gloss>piling (structural element used in construction)</gloss>
-<gloss>pile</gloss>
+<gloss>sheet pile (structural element used in construction)</gloss>

all kokugos, gg5

https://www.collinsdictionary.com/us/dictionary/english/piling
  "Pilings are wooden, concrete, or metal posts that are pushed into the ground and on which buildings or bridges are built. Pilings are often used in very wet areas so that the buildings do not flood."

https://en.wikipedia.org/wiki/Deep_foundation
  "A pile or piling is a vertical structural element of a deep foundation, driven or drilled deep into the ground at the building site."


Google N-gram Corpus Counts
╭─ーーーーーーー─┬─────────┬───────╮
│ 矢板　　　　　 │ 138,918 │ 98.7% │ - (counts might be inflated by place names)
│ シートパイル　 │   1,766 │  1.3% │
│ シート・パイル │      39 │  0.0% │
╰─ーーーーーーー─┴─────────┴───────╯