Soil-intake process

Conclusions

• 1. The movement of slurry during suction occurs through the center of the suction tip in the form of a vortex; moreover, the velocity of the vortex depends on the vacuum, and the cross-sectional area of the tip.

• 2. Vigorous suction of soil (slurry) takes place when the suction tip comes in contact with the surface of the soil or with the tip embedded into the stratum of soil.

• 3. With other suction conditions equal, the bulk consistency of the slurry remains the same for different tips to which the suction tip is embedded in the soil stratum.

• 4. The minimum suction velocity depends on the fineness of the soil. The coarser the soil, the higher the suction velocity required. The minimum suction velocity of soil is defined by the relationship

  $$V_{su_{min} } = V_{st} m,$$

  where v_s is the starting velocity of soil particles, and m is an experimental coefficient characterizing the start of soil suction and is equal to 1.1 for all sand fractions.

• 5. The volume of soil evacuated (slurry) is the same for suction tips of equal cross-sectional area, but different shape.

• 6. The maximum volume of evacuated soil corresponds to the suction tip, whose diameter is 1.2–1.6 times greater than the diameter of the suction pipe.

• 7. The suction height on the vacuum gage exerts a major influence on the volume of evacuated soil (slurry). The higher the vacuum, the greater the volume of soil evacuated.