Silty soil is relatively easy to excavate and transport, with low discharge pressure under corresponding flow velocity and concentration, and less wear on dredging flow-passing components and pipelines.
For cutter selection, a small-arm, wide-opening structure with flat teeth is preferred to reduce suction resistance. The cutter speed can be properly reduced to minimize mud diffusion caused by cutter disturbance, which is conducive to suction.
For impeller selection, a multi-blade high-efficiency impeller is generally selected, and the impeller diameter shall be determined according to the driving mode and discharge distance, based on the highest efficiency of the dredge pump. Due to low wear in silty soil, the service life of impellers and liners can reach 10–12 months or even longer, with low spare parts consumption.
Cohesive soil forms spheres of different sizes during transportation, and the sphere size depends on the cutting thickness and clay grade. Excavation and transportation of cohesive soil are difficult, but the wear on flow-passing components is low.
A small-arm cutter with flat teeth or shovel teeth is recommended. The cutter power is relatively high during excavation; excavation at the maximum speed is preferred to reduce cutting thickness and improve suction performance.
A multi-blade large-diameter impeller is suitable for dredge pumps to enhance system transportation capacity. Cohesive soil dredging is often mixed with siltstone conglomerates, which increases wear and transportation difficulty.
The replacement cycle of flow-passing components such as impellers and pump liners is about 4–6 months (taking the Lianyungang Ganyu Project of TIAN KUN HAO as an example). Steel pipes are preferred for pipelines to reduce the use of hoses and lower pipeline resistance.
Sandy soil dredging features high concentration, easy transportation, and severe wear; flow-passing components may need maintenance or replacement within one month in extreme cases. Flow velocity control is critical in dredging.
A small-arm, wide-opening cutter with flat teeth and shovel teeth is adopted. Dredge pump impellers, pump liners, and shoulder rings wear out quickly, so sufficient spare parts shall be prepared.
Installation of Submersible Pump Impeller:
Gravelly soil is unrestricted in excavation but difficult to transport with high wear.
A universal 5-arm cutter with combined chisel teeth and shovel teeth is generally used. Wear-resistant pipes must be used for pipelines, as gravel causes significant wear on hoses; inspection and spare parts storage for rubber hoses shall be emphasized during construction.
Multi-blade high-efficiency impellers are required for gravel transport. Impellers, pump liners, and other flow-passing components wear quickly, with a maintenance cycle of 2–3 months. The replacement ratio of impellers to pump liners and shoulder rings is generally 2:1. Wear on small liners is insignificant under good water flushing.
Excavation and transportation of rocky soil are difficult; long-distance transportation is not recommended. High-strength multi-arm cutters (7G6-arm / 8G6-arm) shall be used for rocky soil excavation.
Cutter teeth wear severely, with consumption up to 400 teeth per day at peak periods; 8G teeth are more wear-resistant than 7G teeth. Meanwhile, the maintenance and replacement of cutter tooth holders and arms are frequent. For medium-weathered or harder rock, a cutter needs to be replaced every 10–15 days, and cutter repair takes 5–7 days each time.
For rocky soil transportation, impellers with different passages are selected based on the block size of excavated rock; small-blade large-passage impellers are usually used to improve passing capacity. Devices such as mud suction stone deflectors and anti-stone rings can be properly installed on suction pipes. Wear is similar to gravel, causing heavy wear on pipelines, impellers, and pump liners.
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