RU2741684C2 - Method of underground pipeline protection against mechanical damages - Google Patents

Abstract

FIELD: transport machine building.

SUBSTANCE: invention relates to pipeline transport of oil and gas and can be used for protection of underground pipelines laid in rock and/or frozen soils. Object of the invention is to develop a method of protecting an underground pipeline from mechanical damage, eliminating said shortcomings of analogs and a prototype, reduced labor intensity of trench arrangement in rocky ground, as well as increased operational reliability of pipeline. Method for protection of underground pipeline from mechanical damages includes arrangement of pipeline in trench on supports with upper support surface of concave saddle shape, corresponding to laid pipeline. At that, lower support base is equipped with deformable base, which is compressed under weight load from pipeline and filling ground, wherein the first support is located in close proximity to the boundary of the rock mass and the upsetting soil mass, with such reduction of the compression value of the deformable base of each next support, that the pipeline transition from the section made in an array of rocky soil to the section made in the massif of the upsetting soil occurs along the smooth arc.

EFFECT: technical result is simplification of technology of trench preparation in rock soils, mechanical protection of pipeline against action of fragments of rocky soil protruding relative to the general level of the bottom, mechanical protection of the lower part of the pipeline from plastic deformations at boundaries of rocky and sedimenting soils.

1 cl, 2 dwg

Description

The invention relates to pipeline transport of oil and gas and can be used to protect underground pipelines laid in rocky and / or frozen soils.

The traditional means of protecting an underground pipeline from mechanical damage are rock sheets and / or lining.

Known rocky sheet to protect the pipeline (options) and a method of manufacturing rocky sheet [RF patent No. 2317475, F16L 57/00, publ. 02/20/2008, bul. No. 5], consisting of a flexible web made of single-layer, two-layer or multi-layer of sheet one-sided or double-sided laminated fibrous nonwoven fabric based on fibers of the group of polypropylene or polyesters impregnated with fibrous nonwoven fabric throughout the entire thickness with a self-curing composition.

The disadvantage of this rock sheet is the impossibility of preventing the formation of zones of plastic deformation of the pipe walls (dent) in the lower part of the pipeline, at the points of contact with protruding local solid fragments of soil located at the bottom of the trench, under conditions of intense weight load from the pipeline and backfill soil.

To prevent the formation of dents in pipes to protect an underground pipeline, in addition to the rock sheet, the bottom of the trench and around the pipe is usually backfilled with imported sand, which is expensive, especially if there are no natural reserves of sandy soils on the site. Also, if the pipeline is located on a sloping section, the sand bed of the pipeline is susceptible to washout down the slope when draining rain and melt water into the trench, which leads to the pipeline settling down to the rocky soil of the trench base and the formation of dents.

The known method of laying a pipeline in rocky and semi-rocky soils on a longitudinal slope [RF patent No. 2516984, F16L 1/028, publ. 05/27/2014, bul. No. 15], which consists in the preparation of the trench bottom by revealing the leveling and subsequent elimination of local protrusions and local depressions of the trench bottom, continuous laying of sandbags on the trench bottom on the prepared trench bottom, installing the pipeline on sandbags, which reduce the washing out of imported sandy soil and therefore reduce damage to the pipeline insulation.

The disadvantages of this method are:

1) Significant laboriousness of work on leveling the bottom of the trench in rocky or slightly deformable soils.

2) Significant cost and labor intensity of work on the delivery of sand, filling the bags with sand, their continuous laying on the bottom of the trench.

Known lining mat (options) [RF patent No. 137077, F16L 1/06, publ. 27.01.2014, bul. No. 3], designed to protect the insulating coating of the pipeline from mechanical damage at underwater crossings through water barriers, as well as in conditions of rocky, gravel and rubble soils, made in the form of a single structure, consisting of separately manufactured extended elements of polymer material, fastened together in various ways, forming an outer cylindrical shell of the pipeline during installation.

The disadvantages of a lining mat are:

1) Significant cost of the product, high labor intensity of installation.

2) Insufficient effectiveness of protection, for example, at the joints of the lining mats sections, as well as in case of violation of the integrity of the protective shell formed by them due to the destruction of the fastening tapes during the laying and operation of the pipeline.

The listed analogs protect the pipeline from mechanical damage by placing intermediate layers and / or shells around the pipe and under the pipe. At the same time, the experience of operating underground pipelines built using these means shows the presence of a significant number of mechanical defects in areas of rocky soils in the form of through damage to anticorrosive pipe coatings and dents in the pipe metal.

The predominant part of mechanical damage is localized at the bottom of the pipeline, and is caused by mechanical contact between the subsiding pipeline and the rocky soil of the foundation. Obviously, in order to increase the degree of protection, it is necessary to significantly increase the thickness and resistance to local punching of these protective equipment, and this will lead to a significant increase in the cost of pipeline construction.

It is possible to radically solve the problem of protecting the pipeline from mechanical damage by guaranteeing a gap between the rocky soil of the trench base and the lower surface of the pipeline by placing the pipeline in a trench on underground supports, which will exclude direct or indirect (through protective means) contact between the pipeline and the rocky soil of the trench base.

Closest to the proposed method (prototype) is a device [RF patent No. 2613703, E04G 25/00, publ. 03/21/2017, bul. No. 9], designed to support the pipeline in a trench or temporarily lay the pipeline on the soil surface during repair work, made in the form of a polymer support, which is a hollow thin-walled body with a rectangular base, inclined side trapezoidal walls with stiffeners, and an upper supporting surface of a saddle forms. The method of using the prototype consists in placing polymer supports at the bottom of the trench with a given pitch and then laying it in the trench on the polymer supports of the pipeline or in fixing the polymer supports on the lower part of the pipeline, followed by laying it in the trench.

The disadvantages of the prototype are:

1) Insufficient stability of the considered support structure on the rocky base of the trench. In order to securely fix the pipeline and prevent its deformation after laying under the influence of its own weight, as well as the weight of the backfill soil, it is necessary that the supports are placed vertically on a flat base, which is impossible to perform in rocky soils without sand backfilling. Otherwise, the supports will be deformed by bending, which will lead to the loss of their stability.

2) Insufficient impact strength of the considered support structure. For the manufacture of the support, polyethylene, polypropylene or compounds based on them are used, which have low plasticity under low air temperatures (winter). When a supported pipeline is laid on rock, significant weight or shock loads, especially on uneven rock in a trench, will cause the supports to crack or splinter.

The aim of the invention is to create a method for protecting an underground pipeline from mechanical damage, eliminating the indicated disadvantages of analogs and prototypes, reducing the labor intensity of arranging a trench in rocky, soils, as well as increasing the operational reliability of the pipeline.

The technical result of the invention is to simplify the technology of preparing a trench in rocky soils, mechanical protection of the pipeline from the impact of fragments of rocky soil protruding relative to the common bottom level, mechanical protection of the lower part of the pipeline from plastic deformations at the boundaries of rocky and settling soils.

The goal and the technical result in the method of protecting an underground pipeline from mechanical damage, including placing the pipeline in a trench on supports with an upper support surface with a concave saddle shape corresponding to the pipeline being laid, are solved by the fact that the lower base of the support is equipped with a deformable base, which is compressed under the influence of a weight load from pipeline and backfill soil, and the first support is located in close proximity to the boundary of rock mass and settling soil, with such a decrease in the compression of the deformable base of each subsequent support, that the transition of the pipeline from the section made in the rock mass to the section made in the settling soil, occurs along a smooth arc.

The essence of the invention is illustrated in FIG. 1, 2. FIG. 1 shows a diagram of the installation of a polymer support with a deformable polymer base. FIG. 2 shows the layout of polymer supports with a deformable polymer base at the boundary of rock massifs and settling soil.

The method is implemented in the following way:

In trench 1 (Fig. 1), made in rocky ground, supports 2 are installed, in the upper part having a cylindrical recess, and in the lower part equipped with a deformable base 3. Pipeline 4 is laid on supports 2, after which pipeline 4 is filled with soil 5, with Thus, under the simultaneous influence of the weight of the supports 2, the pipeline 4 and the soil 5, the deformable base 3 in the lower part takes the shape of the surface of the bottom of the trench 1, and also compresses by an amount determined by the intensity of the weight effect.

Supports 2 (Fig. 1) are made of polymeric materials that retain their performance at low temperatures. The deformable base 3 of the supports 2, made of polymeric materials, is also made of polymeric materials.

To protect the pipeline 4 from the impact of protruding rock fragments at the bottom of the trench 1, supports 2 (Fig. 2) are placed with a certain step along the pipeline 4. The step of installing supports 2 is determined in accordance with the calculation, according to the value of the permissible deflection of sections of the pipeline 4 between supports 2 under the action of the weight load from the pipeline 4 and soil 5.

When the route of the pipeline 4 (Fig. 2) crosses sequentially located rock mass 6 and settling soil 7, there may be an uneven settlement of the pipeline 4, which is due to the fact that rocky soils 6 are not deformed, and the settling soils 7 are compressed under the influence of pipeline 4 and soil 5 during compaction or thawing. In this case, mechanical contact of the lower part of the pipeline 4 with the boundary 8 of the rock mass 6 and the settling soil 7 can occur.

To protect the pipeline 4 from mechanical damage at the border of 8 rock massifs 6 and settling soil 7, at the bottom of the trench 1 (Fig. 2), within the rocky soil massif 6, supports 2 with a deformable base 3 are installed, and the first support 2 is located in the immediate proximity to the border of 8 massifs of rocky soil 6 and settling soil 7. After laying the pipeline 4 in trench 1, its section, laid within the array of settling soil 7, settles during operation, while compression of the deformable base 3 supports 2 installed on the site , located within the rock mass 6. Since the amount of compression of the deformable base 3 is the greater, the higher the magnitude of the impact on the support 2 of mechanical loads, the maximum compression will be observed at the deformable base 3 of the support 2, located on the border of 8 rock mass 6 and settling soil 7, with a smooth decrease in the amount of compression of the deformable base 3 of each next support 2. As a result, on the border 8 of the rock mass 6 and the settling soil 7, a sharp bend of the pipeline 4 is excluded with the formation of a dent in its lower part, and the transition of the pipeline 4 from the section made in the rock mass 6 to the section, executed in an array of settling soil 7, occurs along a smooth arc.

Example:

It is necessary to protect from mechanical damage a pipeline with a diameter of 1420 mm with a factory anti-corrosive coating, laid on a site that includes a sequential location of rock mass and finely dispersed soil settling during compaction.

In accordance with the calculation performed according to generally accepted methods, it was found that in order to exclude point contact of the lower part of the pipeline with rock fragments at the boundary of the rock massif, it is necessary to use three successive supports, the base deformation of which should be: 0.2 m at the first support located at the border of rock massifs and settling soil; 0.1 m at the second support, 5 m away from the first; 0.05 m at the third support, at a distance of 10 m from the second. To achieve this, the height of the deformable base of the supports, taking into account their compaction under load, is: 1.2 m at the first support; 0.6 m at the second support; 0.3 m at the third support.

At the bottom of the trench, within the rocky ground, supports with a deformable base are installed, a pipeline is laid on the supports, and covered with soil.

Claims (1)

A method of protecting an underground pipeline from mechanical damage, including placing a pipeline in a trench on supports with an upper support surface of a concave saddle shape corresponding to the pipeline being laid, characterized in that the lower base of the support is equipped with a deformable base that is compressed under the influence of a weight load from the pipeline and backfill soil, and the first support is located in the immediate vicinity of the boundary between the rock mass and the settling soil, with such a decrease in the compression value of the deformable base of each subsequent support that the transition of the pipeline from the section made in the rock mass to the section made in the settling soil mass occurs along a smooth arc ...

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