Diagram of the excavator's operation from the pontoon

Soil excavation is carried out by a single-bucket excavator of the Hitachi EX-200 type when it moves along the axis of the trench in compliance with the design marks of the bottom of the trench and slopes. In watered areas, soil development is carried out with an excavator with slat, with refinement to the design marks, in the channel section with an excavator from a pontoon, and at intersections with underground utilities - manually.

At the same time, the width of the trenches along the bottom in the curved sections of the forced bending branches should be equal to 3.6 - 4.0 m. When ballasting oil pipelines with cargo, it is necessary to ensure the width of the trench of 4.0 m under the condition of ensuring a distance between the cargo and the trench wall of at least 0.2 m.

The steepness of the slope of trenches in loamy soils should be no more than 1:0.75. The steepness of the slopes of the underwater loam trench is assumed to be 1:2 at a depth of 2.5 m or more. In the floodplain and coastal areas, the steepness of the slopes is assumed to be 1:1.25 with a trench depth of 2.0 m or more. In coastal areas, the steepness of slopes is assigned to no more than 1:0.75.

Soil removed from the trench and placed in the dump should be placed no closer than 0.5 m from the edge of the trench.

Cutting of the steep right bank of the river should be carried out with excavators of the Hitachi EX-200 type and a bulldozer of the Komatsu D-85 type in layers with loading of soil on dump trucks and its removal to a temporary storage site.

Leveling of the steep longitudinal slope on the right bank of the river (cutting) in soft soils is carried out by bulldozers, and when working at negative temperatures - with the help of a bulldozer with a ripper ("fang") of the Komatsu D 85D type with the removal of soil to the site for storing mineral soil.

Excavation of the trench with a single-bucket excavator with a backhoe should be carried out without the use of manual cleaning of the bottom. When the excavator approaches the signs indicating the location of underground utilities, work should be stopped. The excavation of the trench in this section should be carried out manually at a distance of at least 2 m from the side wall on both sides of the communication and at least 1 m above the top of the existing communication.

Backfilling of trenches should be carried out with a bulldozer DZ-27, in cramped conditions - with an excavator EO-2621, in watered areas with an excavator with slate, at the intersection with existing underground utilities - manually. Trenches are filled in with a minimum time gap after paving. Backfilling of trenches must be carried out with a margin of height, taking into account the settlement of the soil.

When water appears in the trench, the pipeline is backfilled with preliminary drainage to low places of the terrain.

In the areas of intersection with the existing underground utilities passing within the depth of the trench, it is necessary to fill under the existing utilities with non-frozen sand or other low-compressible (deformation modulus of 20 MPa and more) soil along the entire cross-section of the trench to a height of up to half the diameter of the crossed communication by tamping with soil under the communication and layer-by-layer compaction of the soil. Along the trench, the size of the backfill at the top should be 0.5 m larger on each side of the crossed communication, and the slopes of the backfill should not be steeper than 1:1.

In order to prevent soaking of the foundations for the foundations of valves and other structures with surface water (atmospheric precipitation), it is necessary to cover the open pit with a polyethylene film with a thickness of 0.2-0.3 mm, having previously arranged a sump in the pit in a lowered place to collect water flowing from the film and, in case of groundwater, pump it out of the sump of the pit with the AV-701 unit to low places of the relief.