Kûra Hoffman ji bo kargehên kerpîçan bi kapasîteya rojane ya li ser 50,000-200,000 kerpîçan maqûl e.
(Heke kapasîteya we pir zêde ye, em pêşniyar dikintew ji bo we sobeya tunelê ye.)
Parametreyên bingehîn ên firna Hoffman:
| Hejmara derî | Beşek ji agir | firehiya hundir (m) | Bilindahiya hundir (m) | Kapasîteya rojane (pcs) |
| 18-24 | 1 | 3.6-3.9 | 2.6-2.8 | ≥70,000 |
| 18-24 | 1 | 3.9-4.2 | 2.6-2.8 | ≥80,000 |
| 32-48 | 2 | 3.6-3.9 | 2.6-2.8 | ≥130,000 |
| 32-48 | 2 | 3.9-4.2 | 2.6-2.8 | ≥150,000 |
| 48-72 | 3 | 3.6-3.9 | 2.6-2.8 | ≥190,000 |
| 48-72 | 3 | 3.9-4.2 | 2.6-2.8 | ≥210,000 |
| ≥72 | ≥4 | 3.6-3.9 | 2.6-2.8 | ≥250,000 |
Dema şandinê: Tebax-23-2021