RU2613151C1 - Method for laying of underground pipeline - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: prior to pipeline laying a multi-layer base is prepared, for which power belt are rolled out across the trench with ends fixed on the trench berm with temporary pins, and hollow overlapping plates are laid at the trench bottom. Heat-insulating "mattresses" are formed on the plates, consisting of two or three layers of expanded fine perlite sand, enclosed in non-woven synthetic material (NSM). NSM edges are welded by thermal heating. Pipeline is laid on the prepared surface, and then covered, together with the multilayer base of the trench bottom and trench side surfaces by flexible permeable carpets, with subsequent backfilling with granulated expanded clay with height of at least 200 mm on top generatrix. Prior to pipeline backfilling with, power belt ends are exempt from temporary pins and tied with tension along the expanded clay enclosed in NSM. Final filling with bunding is made in a traditional way.

EFFECT: increased operational reliability of pipeline.

4 cl, 3 dwg

Description

The invention relates to construction and can be used in the construction of pipelines transporting a product with a temperature that is positive or variable in time, with underground laying in permafrost soils (MMG) of predominantly island type.

It is known that during operation underground pipelines change their initial position, which occurs in connection with the product pumping conditions due to the special laying of the pipeline during the construction of pipelines in permafrost soils (MMG).

Known Recommendations for the design of heat-insulating structures of main pipelines in the form of a continuous ring, as well as with heat-insulating screens and bedding ("Recommendations for the design of heat-insulating structures of main pipelines" P536-84 VNIIST, Moscow, 1985). Also known are heat-insulating segments made of extruded Extrol expanded polystyrene, which are intended for thermal insulation of pipelines with a diameter of 57 mm to 1420 mm, including in areas with permafrost soils transporting a medium with a temperature of minus 63 ° C to plus 75 ° C, and polystyrene extrusion plates "Extrol" TU 5767-004-77909577-12 and TU 5767-003-77909577-2012.

The disadvantages of using heat-insulating segments and shells include an increase in the size of the trench, the need for additional loading, equipping the plethovozers with removable pencil cases and wooden lodgements with an arcuate shape with rubber gaskets, increasing the cost of their storage, and most importantly, the lack of instrumental control of the integrity of the ring insulation during the construction of pipelines with the underground laying method before filling with the transported product and in accordance with paragraph 5.8 of SNiP 41-03-2003 with a channel-free piercing Pre-insulated pipelines with polyurethane foam insulation in a polyethylene sheath must be equipped with a system for operational monitoring of insulation moisture (UEC).

Known methods of laying an underground pipeline in areas of continuous and intermittent propagation of permafrost soils (MMG), including the development of a trench in a filled embankment with a width exceeding the radius of the thawing halo, or laying the pipeline in an enlarged trench with a dump along the surface and along the length of the pipeline of prismatic prisms with distances not exceeding the beam span, the height determined by the calculation. As a result of the thawing of soils of the near-tube space, the subsidence of soils with the pipe sediment is compacted to the level of non-subsiding soils (patent RU 2494302, publ. 09.27.2013).

There are other known methods of laying pipelines in MMG (patent RU 2244191, publ. 10.01.2005, patent of the Russian Federation 2066806, publ. 09/20/1996).

All the above methods have common drawbacks: the increase in the volume of earthwork, the need for imported sand and the unpredictability of the possible development of thawing haloes of MMG with a subsequent change in the design position of the pipeline.

A known method of laying an underground pipeline and a device for its implementation in the construction of trunk pipelines in winter on the slopes of the route, composed of high-ice permafrost soils (RF patent 2472053, publ. 01/10/2013), which consists in excavating a trench, laying on its bottom of the pipeline with placement on its sides of two drainage channels, consisting of tubular elements joined together, and backfilling the trench with soil. Sections of the surface of the bottom of the trench are performed at an angle with decreasing to its vertical axis. The joined tubular elements are knocked into the space between the pipeline and the bottom of the trench, after which they block the pipeline, the bottom of the trench, the side surfaces of the tubular elements and trenches with flexible permeable carpets, followed by filling them with soil, covering it with free side sections of the carpets and finally filling the trench. Each tubular element is made in the form of a bending-natural straight prism of triangular section, consisting of high-strength fiberglass.

The specified solution has the following disadvantages:

- the design does not prevent the process of thawing MMG near-tube space at a positive temperature of the transported product;

- the complexity of the profile of the bottom of the trench;

- the constancy of the living section of the tubular elements does not guarantee the passage of water during the service life, i.e. non-repairable without removal of flexible waterproof carpets from the pipeline.

As a prototype, a method of constructing a pipeline in permafrost soils with an alternating relief pattern (patent 2244192, publ. 10.01.2005), which consists in extracting the trench, laying the pipeline in it, fixing it and securing it at the design elevations with backfill, has been adopted. At the same time, at transitions with a calm relief, a trench is torn in the active layer with a depth that ensures that the upper generatrix of the pipeline is not higher than the level of the day surface, and before laying the pipeline, the walls and the bottom of the trench are lined with non-woven synthetic material (NSM) sheets with overlapping overlapping edges transverse to them on the pipeline berm trenches. The backfill soil is placed in ballasting polymer-panel devices (PPU) hung on the pipeline adjacent to each other, followed by the filling of the embankment protecting the pipeline.

The disadvantages of the prototype method are as follows:

- the design of ballasting devices does not prevent the thawing of MMG and is laborious during installation;

- the absence of a heat-insulating base under a warm pipeline provokes the development of MMH thawing halos;

- in thawed soils as a result of subsidence of the loaded pipeline, the probability of a violation of the fastening of the longitudinal edges of the panels of NSM on the trench burs is not excluded;

- the backfill soil laid on the NSM abroad of ballasting polymer-panel devices does not participate in the ballasting of the pipeline.

The claimed invention is aimed at eliminating the unpredictable thawing of MMG at positive temperatures of the transported product in large-diameter steel pipelines.

The objective of the invention is to increase the reliability of underground pipelines laid on permafrost soils mainly island type. The technical result of the invention, which is achieved by the implementation of this method, is to ensure a stable position of the pipeline and soil in the trench due to the multilayer structure combining the elements of thermal insulation and loading.

The task in the method of laying an underground pipeline, which consists in excavating a trench, laying a pipeline, blocking the pipeline, the bottom of the trench and side surfaces with water-permeable panels of non-woven synthetic material (HCM), filling the near-pipe space with a height of at least 200 mm above the upper forming expanded clay, closing the panel HC by heat soldering, installation of weights at the ends of the heat-insulating construction made of expanded clay expanded clay and final filling with soil, it is decided that before laying flexible power belts are laid out in the cross section of the trench with fastening the ends on the berm of the trench with temporary pins and along the bottom of the trench with the construction of a multilayer base from hollow reinforced concrete slabs, on the surface of which a soft heat-insulating bed of sand of perlite expanded, small, closed by thermal soldering in two three layers of non-woven synthetic material, and NSMs closed by thermal soldering along the upper generatrix along the entire length of the panel are additionally strengthened with with a tight tension of flexible power belts, while mattresses made in basic conditions can be used as a heat-insulating bed.

In particular cases of the method, reinforced concrete floor slabs are provided with eyes and power belts are fixed at one end to the eyes of reinforced concrete floor slabs, and the other end is fixed on the berm of the trench with temporary pins.

Thus, a closed thermal insulation structure of the lateral and upper surfaces of the warm pipeline is formed, which, after a bundle of soft power belts, creates a circular heat-insulating layer, and the presence of hollow reinforced concrete floor slabs laid on the MMG base helps to dissipate the heat flow under the pipe and prevent the entire pipeline structure from sagging during extreme thawing of the surface soil of the embankment. In addition, the heat-insulating layer does not require trench broadening and special installation quality control, as a similar design is regulated for ballasting gas pipelines with mineral soils in combination with panels of non-woven synthetic material (NSM) (paragraph 2.14 of BCH 39-1.9-003-98).

The invention is illustrated by graphic material, where in FIG. 1 and FIG. 2 shows a cross section of a pipeline laid in a MMG section; FIG. 3 is a longitudinal profile with stacked heat insulating and loading devices, wherein in FIG. 1 shows a cross section of a pipeline filled with expanded clay before joining the edges of the NSM panels, and FIG. 2 - the same cross-section of the pipeline after soldering panels NSM, a bunch of flexible belts and the final backfilling of the trench with soil.

The method is as follows.

In permafrost soils 1, they dig a trench with a depth that provides underground laying of pipeline 2, taking into account the heat-insulating base in the form of hollow reinforced concrete slabs 3, expanded perlite sand (silica) 4, enclosed in HCM 5, closed around the perimeter by heat soldering under route conditions, or delivered in the form of mattresses with dimensions L × B × h (20 × 3 × 0.2) m, as well as taking into account the filling height of not less than 200 mm of expanded clay 6 in the panel of HCM 7 and soil 8 above expanded clay with a total height of at least 1 m from the top piping yes 2.

Before laying the pipeline 2 at a certain distance, depending on the length of the hollow reinforced concrete slabs-floors, power belts 9 are made on the walls and bottom of the trench, made of durable, non-decaying non-woven materials in the soil, which are fixed to the trench berm with temporary pins 10, or one at the end of the belt are attached to the plates in special nests (eyes) before laying them in a trench. After laying the slabs, the second end of the belts is mounted similarly on the berm of the trench with pins 10.

On the laid hollow reinforced concrete slabs-slabs along the trench along the width of the slabs, LFM is spread, on which sand perlite expanded fine sand (silica) is poured with an even layer, followed by LFM coating and heat soldering along the perimeter with sections ~ 20 m long, or silica "mattresses" are supplied from manufacturers and laid out on plates, which also reduces the rigidity of the pipe-plate design.

Pipeline 2 is laid on the prepared heat-insulating base, after which the pipeline, bottom and walls of the trench are closed with flexible water-permeable panels 7 (HCM with dimensions of 20 × 25 m, prepared under basic conditions), followed by their filling with expanded clay 7, and followed by a heat soldering followed by a bundle of flexible belts 9 'and the installation of weights 11, type UBO-M and PKU, at the ends of the insulating structure made of expanded clay.

The final backfill with soil 8 is made in the traditional way from the dump of the trench.

The effect of the invention is that instead of pipes with expensive factory-made thermal insulation with an external waterproofing coating that requires special conditions of transportation and storage on the highway, standard waterproofed pipes are used, and the tube area is formed from structures that use industrial materials with low thermal conductivity :

Expanded fine perlite sand (silica) 0.05-0.06 W / m⋅K;

Expanded clay 0,099-0,148 W / m⋅K;

Hollow core slabs 0.169 W / m⋅K.

In this method, a near-tube medium is created with thermal conductivity that limits the thawing of MMG, which ensures a stable design position for a long service life.

In the case of flooding of the trench, which occurs due to external heat, causing spring-summer snow melting, bulk expanded clay, which is in a closed volume of LFM, as a result of water absorption also plays the role of a load, providing “zero” buoyancy of this section, and solidity is created in the design which combines the insulating and loading properties of the materials used.

Thus, this invention solves the problem of improving the reliability of the pipeline on the tracks, composed of permafrost soils.

Claims (4)

1. The method of laying an underground pipeline, which consists in excavating a trench, laying a pipeline, blocking the pipeline, the bottom of the trench and side surfaces with water-permeable panels of non-woven synthetic material (NSM), filling the near-pipe space with a height of at least 200 mm above the upper claydite forming, closing the fabric of NSM by heat soldering, installation at the ends of a heat-insulating construction made of expanded clay expanded weights and final filling with soil, characterized in that before laying the pipeline in the cross section of the trench is laid out with flexible power belts with fastening the ends on the berm of the trench with temporary pins and the construction of a multilayer base on the bottom of the trench from hollow reinforced concrete slabs, on the surface of which a soft heat-insulating bed of sand of perlite expanded, small, closed by a heat solder in two or three layers is formed non-woven synthetic material, and NSMs closed by thermal soldering along the upper generatrix along the entire length of the panel are additionally strengthened by a bond with tension m flexible power belts. 2. The method according to p. 1, characterized in that as a heat-insulating bed can be used mattresses made in basic conditions. 3. The method according to p. 1 or 2, characterized in that the reinforced concrete slabs are provided with eyes. 4. The method according to p. 3, characterized in that at one end the power belts are fixed in the eyes of reinforced concrete slabs, and the other end is fixed on the berm of the trench with temporary pins.

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