RU2661236C2 - Anchor device for fastening pipeline in permafrost - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: invention relates to construction and is intended for the construction of underground pipelines in permafrost soils. In the method, the anchoring device for fixing the pipeline includes two anchors, immersed in permafrost beneath the bottom of the trench on opposite sides of the underground pipeline. Anchors over the pipeline are connected by a power belt. Each anchor has several helical blades with a diameter d, located along the thrust along one screw line with the other blades. Above power belt is made of a flexible element in the form of two branches of a closed loop. Such lower parts of each branch are freely passed inside the rigid support bracket of the circular cross-section or through the rotation roller at the upper end of the traction of each screw anchor and are movable in the direction of the longitudinal axis of the pipeline. In the upper part of the closed loop at two points equidistant from the axis of the anchor device, each branch of the flexible element is attached to a metal cradle, mounted on a soft gasket at the top of the pipeline.

EFFECT: increased reliability of the construction of underground pipelines in permafrost and improved efficiency of construction.

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Description

The invention relates to the construction and is intended for the construction of underground pipelines in permafrost soils.

A known design of an anchor device for securing an underground pipeline in permafrost soils from ascent [Borodavkin P.P. Underground trunk pipelines. M., 2011] (prototype). Wells are being drilled on both sides of the pipeline at the bottom of the trench. They install disc anchors, each with one or two round flat discs welded perpendicular to the anchor rod. Wells with installed anchors are covered with soil, taken out while drilling a well, and filled with water. After laying the pipeline to the bottom of the trench, the anchors are connected by a steel power belt enveloping the upper part of the pipeline. The anchor device is ready for use after the soil completely freezes in the well.

The disadvantages of this device are as follows:

- Disk frozen anchors use the capabilities of the wells insufficiently, their bearing capacity is underestimated, because the diameter of the discs is less than the diameter of the drilled well.

- High-quality filling of wells through narrow gaps between a large number of disks and well walls is difficult and unreliable, therefore, the number of disks is limited to two, and, therefore, the depth of immersion of the anchors is small. For this reason, the bearing capacity of such anchors is limited and it is necessary to increase the number of anchor devices along the length of the pipeline. This leads to a significant increase in the cost of fixing the pipelines in permafrost soils.

- Underground pipelines in permafrost soils during transportation of natural gas with a positive temperature in the initial sections of the main pipelines are elongated and can move in the axial direction by significant values (up to 20-30 cm). For this reason, anchor devices receive additional elongations and stresses that can lead to the destruction of power belts or pulling out of anchors. The design of the anchor devices considered in the prototype does not take this into account.

The aim of the invention is to increase the reliability of the design of underground pipelines in permafrost soils and increase the efficiency of construction.

The goal is achieved by the fact that each anchor blade is made helical and is located along the rod along the same helix with other blades; the power belt is made of a flexible element in the form of two branches of a closed loop, the lower parts of each branch are freely passed inside a rigid support bracket of circular cross section or through a rotation roller at the upper end of the thrust of each screw anchor and has the ability to move in the direction of the longitudinal axis of the pipeline, and in the upper parts of the closed loop at two points equidistant from the axis of the anchor device, each branch of the flexible element is attached to a metal lodgement mounted on a soft pad in the upper part part of the pipeline.

The goal is also achieved by the fact that:

- screw anchors with a blade diameter d are screwed into wells with a diameter d, which are drilled in permafrost and pre-filled with water-saturated sand;

- screw anchors are screwed directly into the permafrost soil into leader wells, exceeding the diameter of the anchor barrel by several millimeters;

- a flexible closed belt is made of two separate halves of the same length, which are connected in the upper part of the pipeline.

Comparative analysis with the prototype shows that the claimed device is distinguished by the totality of the above features. This allows us to conclude that the sign of "novelty."

Comparison not only with the prototype, but also with other technical solutions in the art did not allow them to identify signs that distinguish the claimed device from the prototype, which allows us to conclude that the criterion of "significant differences".

In FIG. 1 shows a cross section of a pipeline with anchoring in permafrost soil. In FIG. 2 shows a pipeline with anchor fastening (side view) with the scheme of the flexible belt working only against vertical load, in the absence of horizontal movement of the pipeline. In FIG. 3 shows a pipeline with anchor fastening (side view) in the initial position, with the possible horizontal movement of the pipeline. In FIG. 4 shows a diagram of the operation of an anchor device of a pipeline with horizontal movement of the pipeline.

Design description

The pipeline 1, laid on the bottom of the trench 14, is kept from ascending or losing longitudinal stability by an anchor device, including two anchors with rods 4 and screw blades 5, immersed in permafrost soil 2 below the bottom of the trench 14 on opposite sides of the underground pipeline 1, as well as the power belt 11 connecting these anchors over the pipeline (FIG. 1). To redistribute the load on the surface of the pipeline 1, a hard steel lodgement 10 is placed under the power belt 11. A soft gasket 13 is installed under it to protect the insulation coating of the pipeline 1 from damage.

Screw blades 5 with a diameter of d are installed with an optimal pitch, providing maximum bearing capacity of the anchors. If there is no thawing of soil under the pipeline, the upper blade is located at a distance of 6d below the bottom 20 of trench 14. In the presence of a zone of thawing soil under the pipeline, the upper blade is located at a distance of 6d from the lower point of the thawing ground of frozen soil under the pipeline.

The power belt 11 is made of a flexible element in the form of a closed loop, for example, of a flexible steel cable. The loop forms two branches: left 15 and right 19 (Fig. 2), (Fig. 3). The upper ends of each branch of the closed loop at two points 12 equidistant from the axis of the anchor device are fixed from horizontal movements along the metal lodgement 10.

The lower parts of the power belt 11 are freely passed inside a rigid support bracket 3 of circular cross section or through a rotation roller 9 located at the upper end of the rod 4 of each screw anchor. The first option, simpler, is used in the case when horizontal temperature movements during operation of the pipeline 1 are absent or insignificant (Fig. 1b, Fig. 2). The second option is used for large horizontal movements of the pipeline 1 together with the left 15 and right 19 branches of the power belt 11. This leads to the movement of the branches 15 and 19 of the power belt 11 relative to the rotating roller 9 (Fig. 1, a, Fig. 3, Fig. 4).

An anchor consists of a rod 4 with screw blades attached to it 5. In FIG. 1 shows two possible options for anchors.

In the first embodiment, screw anchors are screwed directly into the permafrost soil 2 into pre-drilled leader wells 8, which are several millimeters larger than the diameter of the tie rod 4 of the anchor (Fig. 1, a). This facilitates their screwing into a very strong permafrost. The forces in the anchor when screwing into such a soil are very large, therefore, the diameter of the rod 4 and the thickness of the blades 5 of such an anchor are much larger than with the embodiment shown in FIG. 1 b.

In the second embodiment, screw anchors are screwed into pre-drilled wells 6 filled with water-saturated sand. The diameter of the helical blade is equal to the diameter of the leader well. The force of screwing a screw anchor into non-frozen water-saturated sand is much less than with the first option, therefore, the dimensions of the rod and blades are also smaller, with the same bearing capacity of the anchor, and the number of screwed screw blades is much larger. Such an anchor acquires the design bearing capacity only after freezing of water-saturated sand.

Each of these options has its own advantages and should be used for certain specific conditions and technical capabilities of construction equipment.

The principle of operation of the device

In the absence of horizontal pipeline movements, only vertical loads 7 from the buoyancy forces of water and loss of longitudinal stability of the pipeline (Fig. 1, b) and (Fig. 2) act on the anchor device. These vertical loads are perceived by two branches 19 and 15 of the power belt 11.

For large horizontal movements of the pipeline 1 in the direction 18, a second embodiment of the design of the anchor device with rollers 9 at the upper end of the tie rod 4 of the anchor shown in FIG. 1a, FIG. 3, FIG. 4. In the initial installation position, the upper ends of each branch 19 and 15 of the power belt 11 are fixed at two points 12 and are equidistant from the axis of the anchor device by an amount S equal to the design value of the movement of the pipeline 1 at the place of fastening by the anchor device (Fig. 3). In the process of moving the pipeline 1, the upper ends of each branch move together with the pipeline 1, but the distance between them does not change, remaining equal to 2S, and the lower ends remain in the initial position. For this reason, the branches 15 and 19 of the power belt 11 take the position shown in FIG. 4 with a dashed line. With the maximum permissible design movement, the left branch 15 takes the vertical position 16, and the movement of the right branch 19 in the limit position 17 is S. The presence of the roller support 9 significantly reduces the amount of force transmitted to the upper end of the anchor rod 4 when moving the branches 15 and 19 of the power belt. This effort will be minimal when using a roller bearing with a sealed ball bearing.

When moving the pipeline 1 in the opposite direction, the branches 15 and 19 of the power belt 11 return to their original position.

For ease of installation of the power belt (for example, a steel cable) in cramped conditions at the bottom of a narrow trench 1, it is made of two separate halves, the same length from each half of the pipeline. After immersion in the soil of the anchor, each half of the cable is passed through the support roller 9 or the anchor bracket 3, and the upper ends of the cable are temporarily fixed on the berm of the trench 14. After laying the pipeline 1 at the bottom of the trench, the corresponding ends of the cable are connected to the lodgement in the upper part of the pipeline with special cable clamps.

Claims (4)

1. Anchor device for securing a pipeline in permafrost soil in a trench, including anchors immersed in permafrost soil below the bottom of the trench, on opposite sides of the underground pipeline, and a power belt connecting these anchors on top of the pipeline on each anchor; several blades of diameter d are installed along the length of the rod, characterized in that each anchor blade is helical and is located along the rod along the same helix with the other blades; the power belt is made of a flexible element in the form of two branches of a closed loop, the lower parts of each branch are freely passed inside a rigid support bracket of circular cross section or through a rotation roller at the upper end of the thrust of each screw anchor and have the ability to move in the direction of the longitudinal axis of the pipeline, and in the upper parts of the closed loop at two points equidistant from the axis of the anchor device, each branch of the flexible element is attached to a metal lodgement mounted on a soft pad in the upper part part of the pipeline. 2. Anchor device according to claim 1, characterized in that screw anchors with a blade diameter d are screwed into wells with a diameter d that are drilled in permafrost and pre-filled with water-saturated sand. 3. Anchor device according to claim 1, characterized in that the screw anchors are screwed directly into the permafrost soil into the leader wells exceeding the diameter of the anchor rod by several millimeters. 4. Anchor device according to claim 1, characterized in that the power belt is made of two separate halves of the same length, which are connected in the upper part of the pipeline.

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