RU2227238C2 - Pipeline securing method - Google Patents

Abstract

FIELD: building industry, particularly underground pipeline laying. SUBSTANCE: method involves digging out stepped trench having upper step formed as backfill trench of rectangular or trapezoid profile and lover step having rectangular profile; solidifying base for pipeline laying by means of plate having convex shell with radius equal to outer pipeline diameter; changing rectangular lower trench step profile to semicircular profile; lying pipeline into lower trench step; layered filling trench with soil from either pipeline sides; smoothing soil; solidifying the first soil layer by working plate having concave shall with radius equal to outer pipeline diameter; filling trench with the second and following layers and solidifying thereof; solidifying the last soil layer by means of flat plate, solidifying soil above trench at the height of not less than 0.3 m by means of flat plate or vibroroller. EFFECT: increased reliability of pipeline securing. 9 dwg

Description

The present invention relates to the field of construction of trunk pipelines laid in flooded and non-flooded soils.

Known methods and devices for securing pipelines in the required (design) position (1, 2, 3, 4, 5), including excavating a backhoe for a trench profile specified by the project, laying pipelines into it, laying the pipeline in the design position with reinforced concrete weights (UBO) , ASG, UBC) or anchor devices and backfilling of the pipeline with soil without compaction. In this case, the dimensions of the transverse profile of the trench according to SNiP 2.05.06-85 should be taken as follows:

a) for pipelines laid in flooded soils, figure 1:

- trench depth (h _tr ):

- the width of the trench down (in _tr ):

- the width of the trench on top (B _Tr ):

b) for pipelines laid in non-irrigated soils, figure 2:

- trench depth (h _tr ):

- the width of the trench down (in _tr ):

- the width of the trench on top (V _Tr ):

where h _h is the height of the backfill layer above the pipeline, taken equal to 1.0 m for pipelines with a diameter of ≥1.02 m and 0.8 m for pipelines with a diameter of less than 1.02 m; D _Tr - the outer diameter of the pipeline; m is the foundation of the trench.

The disadvantages of the known methods and devices for securing pipelines are large volumes of earthwork (for 1 meter of trench you need to develop 10.5 m ^{3 of} soil for a pipeline with a diameter of 1.42 m), the high cost of securing pipelines with reinforced concrete weights (for 1 km of pipeline costs make up about 30% of its estimated cost), unreliable fastening of the pipeline in the design position due to non-compaction of soil around the pipeline and throughout the volume of the trench, insufficient clearance between the slopes of the trench and reinforced concrete b allotting elements and their non-rigid fixing on the pipeline, and when fixing the pipeline with screw anchors, the latter lose their ballasting ability as a result of temperature (longitudinal and transverse) deformations of the pipeline when a hot product (gas, oil) passes through it.

The closest technical solution in relation to the claimed one is to fix the pipeline using the “Tamped trench bottom” method, including trenching with trenching equipment, compacting the bottom of the trench so that it matches the profile of the pipeline on a short circular arc, laying the pipeline in the trench and compacting the soil backfill around piping manually or by light planar vibrators (2).

The “Tamped trench bottom” method has the following disadvantages. Large volumes of earthwork in connection with the installation of a trench with a depth equal to (h _s + D _tr ). The use of inefficient manual compaction of soil around the pipeline and low-performance lightweight planar vibrators. Manual tamping of the necessary profile of the bottom of the trench, coinciding on a small arc with the outer diameter of the pipeline.

The purpose of the invention is to reduce the cost of securing the pipeline in the design position, laid in flooded and non-flooded soils, and increasing the reliability of its operation in the construction and operational periods.

The essence of the invention lies in a certain sequence of production operations, consisting of a device, depending on the type, condition and degree of watering of the soil and the diameter of the pipeline, an excavator with a special trench profile shovel, tamping and base formation, which coincides with the outer diameter of the pipeline by half of its diameter, mounted a vibratory rammer equipped with a convex-shaped working plate with a radius equal to the outer radius of the pipeline (including its insulation), pipe laying pipelaying the pipeline into the trench according to the existing technology, layer-by-layer backfilling of the pipeline with soil and layer-by-layer compaction of the soil of the backfilling by a mounted vibratory rammer having a working plate with a concave shape and a radius of concavity equal to the outer diameter of the pipeline (including its insulation), and when the layer height is reached above the top pipeline 0.3 m, further compaction of the backfill soil is carried out by a mounted vibratory rammer with a flat horizontal shell of the working plate or a vibrating roller m (trailed or self-propelled) in order to intensify work on compaction of the backfill soil.

At the same time, through the use of the holding ability of the backfill soil during its vibration compaction to the required (by the stability condition) density, the pipeline is rigidly fixed in the specified design position, which completely eliminates the use of various types of pipeline ballasting with reinforced concrete weights and anchors, this also reduces the preparation period pipeline construction, there is no dependence on the availability and supply of components of ballasting products and Qdim adjusting the construction schedule of the pipeline in their absence.

In addition, high-quality soil compaction around the pipeline and along the entire profile of the trench and, as a result, uniform loading and rigid fastening of the pipeline along the route, significantly increase the reliability of the pipeline during construction and operational periods in connection with the joint operation of the pipeline with the soil. It also allows you to take into account the attached mass of soil in the strength calculations of the pipeline.

At the same time, due to the construction of a special profile of the trench for laying the pipeline, the volume of excavation work for excavation is reduced by at least 1.55 times, and for backfilling - by 1.6 times when laying the pipeline in disconnected irrigated soils and 1.75 times - in cohesive flooded soils. The volume of excavation work for excavation and backfilling of the soil when laying pipelines in non-irrigated soils is reduced by 1.35 times. It is also possible to further reduce the volume of excavation by 20-30% by reducing the thickness of the backfill layer by 20-30 cm. The costs of drainage, which is carried out to drain the trench when laying the pipeline in flooded soils, are also reduced.

Figure 1 shows the transverse profile and shows the dimensions of the trench, arranged according to the existing technology, when laying the pipeline in flooded soils and securing it in the design position with reinforced concrete loads (UBO).

Figure 2 shows the transverse profile and the dimensions of the trench, arranged according to the existing technology, when laying the pipeline in non-watered soils and securing the pipeline with backfill soil without compaction.

Figure 3 presents the transverse profile and the dimensions of the trench arranged by the proposed technology, when laying pipelines in flooded and non-flooded soils.

Figure 4 shows the options for the transverse profiles and the dimensions of the trenches arranged according to the proposed technology, when laying pipelines in flooded and non-flooded soils.

For comparison purposes, in FIG. 1, 2, 3 and 4 also shows the values of the areas of the transverse profile of the trenches (F _Tr ), arranged according to the existing and proposed technologies.

In FIG. 5, 6 and 7 show the sequence of technological operations of securing the pipeline in flooded and non-flooded soils according to the proposed method.

In FIG. 8 and 9 respectively show the device - mounted rammers (VTN) and forms of working interchangeable plates designed to secure the pipeline according to the proposed method, laid in watered and non-watered soils.

Technological operations of fixing the pipeline, laid in flooded and non-flooded soils, the proposed method and device for its implementation, are performed in the following sequence:

- a device, depending on the type and condition of the soil, as well as the diameter of the pipeline with an excavator, a backhoe shovel of a stepped profile of a trench, possible options of which are shown in FIG. 2, 3 and 4, and for the embodiment shown in FIG. 3, the transverse profile of the trench consists of two steps:

a) the upper trapezoidal (1-2-3-4, figure 3), we call it a backfill trench, the dimensions of which must be taken as follows:

- trench depth (h $\genfrac{}{}{0ex}{}{\text{0.3}}{\text{tr}}$ ):

- the width of the trench down (in $\genfrac{}{}{0ex}{}{\text{0.3}}{\text{tr}}$ ):

- width of trench on top (B $\genfrac{}{}{0ex}{}{\text{0.3}}{\text{tr}}$ ):

b) lower rectangular (a-b-c-d, figure 3), which serves as the basis for the pipeline with dimensions determined by the formulas:

- trench depth (h $\genfrac{}{}{0ex}{}{\text{0}}{\text{P}}$ ):

- trench width (in $\genfrac{}{}{0ex}{}{\text{0}}{\text{P}}$ ):

And for the options shown in figa and 4b, the dimensions of the backfill trench should be determined by the formulas:

where a is the safety factor of the width of the caterpillar or pneumatic wheels of the base machine with a mounted vibration rammer;

in _EC - the stroke width of the base machine, on which the rammer is hung;

b, a, c - coefficients depending on the type and condition of the soil, the height and width of the teeth of the bucket of the excavator;

- following the installation of the necessary profile of the lower stage of the trench by a mounted vibratory rammer (pos. 1, fig. 5b), mounted, for example, on an excavator EO-3322 (pos. 2, fig. 5b), having a convex shell (pos. 3, fig. 5b) with a radius equal to the outer diameter of the pipeline, including insulation, and rigidly attached to the working plate (item 4, fig. 5b), the base is rammed to the density and marks specified by the project under the pipeline, and at the same time, the rectangular profile is transformed the lower stage of the trench (a-b-c-d, figa) in a semicircular (a-b-c, figb) at half the diameter of the pipeline, while the speed of ramming the base under the pipeline is at least 125 mp per hour (or 1000 mp per shift);

- then, according to existing technology, the pipe layers lay the pipeline into the lower stage of the trench of the semicircular profile with a base compacted to the density required by the design (item 5, fig. 5c);

- further, a backhoe is excavated by layer-by-layer backfilling of the trench with soil on both sides of the laid pipeline and leveling of the soil, and the soil adjacent to the pipeline should not contain large fractions, the permissible sizes of which are established experimentally, and the thickness of the first backfill layer (after leveling) depending on the diameter of the pipeline is taken equal to (0.25-0.50) D _tp (item 6, figa);

- after filling and leveling of the first layer, it is compacted by mounted vibratory rammers (pos. 7, fig.6b) equipped with working plates (RP) with a concave shell (pos. 8, fig.6b) with a radius equal to the outer radius of the pipeline in this case, the concave shell allows the soil to be compacted in close proximity to the pipeline, since in this case compressive normal stresses are created and thereby the soil is prevented from sliding along the pipeline, as a result of which damage to the pipeline insulation would be possible;

- similarly, filling and compaction of the second layer is carried out (item 9, figv);

- then the recesses formed as a result of compaction in the second layer are covered with soil (pos. 10, figa), the layer is leveled, and this layer is re-compacted over its entire surface with a mounted ram rammer (pos. 11, fig.7b), the thickness of the filling (pos. 12 and 13, figv) of the second and subsequent layers (pos. 12 and 13, figv) is taken equal to (0.25-0.50) D _tr , and their compaction after reaching a layer height above the pipeline equal to 0.3 m can be carried out not only by ramming with a flat working plate, but also by vibrating roller (trailer or self-propelled) in order to intensify the work of compaction of backfill soil at the appropriate;

- during winter work, the first layer is poured and the pipeline is sprinkled with sand or clay melt soil, for this purpose the necessary volumes of soil reserves are created along the pipeline route, which are insulated, for example, with rolled material alveolite or alveolene, whose thermal conductivity (λ _A ) is 25 times below the thermal conductivity of mineral wool (λ _mv ), and transportation of thawed soil along the route can be carried out by road or a specially designed soil trolley, moved along the route with any traction mechanism (tractor, car, pipe layer), and after sprinkling the pipeline and sprinkling the first layer with thawed soil, the sprinkling of the second and next layers is taken to be (0.25-0.50) D _mp , and their compaction is carried out by a mounted vibratory rammer with a concave shell working plate and with a flat working plate;

- after compaction of each layer, quality control of compaction of the backfill soil is carried out using the cutting ring method in accordance with GOST 5180-84, with the number of samples per 1000 mp pipeline routes at the initial stage can be taken equal to 25-30 pieces, approximately one sample per 200 m ^{3 of} compacted soil or 7-8 samples per layer, and then, as experience is gained by the manufacturer and the geotechnical control service, the volume of samples decreases and is selected based on one sample on 250-300 m of soil.

The device (Fig. 8) is a mounted vibration rammer (VTN) for implementing a method of securing pipelines laid in irrigated and non-irrigated soils, including a base machine, for example, an EO-3322 excavator (the position in Fig. 8 is not shown), a ram rammer (item 15 ), vibration exciter (pos. 16), work plate (pos. 17), fixed plate (pos. 18), traverse (pos. 19), hydraulic equipment (pos. 20), equipped with interchangeable work plates, rigidly bolted to the vibrator body while the working plates are made of various shapes and have a convex , concave and flat shells (Figs. 8 and 9), acting directly on the soil, and the radius of convexity of the concavity of the shell is determined by the diameter of the pipeline being fixed, and the angle α (Fig. 9a) and the angle θ (Fig. 9b) are determined by the slope of the surface of the structure , near which it is planned to carry out soil compaction, and the working plate with a convex rim is intended for the foundation for the pipeline at half its diameter, including its insulation, and with a concave (figa, c and d) - for compaction of the backfill soil at pushing to the pipeline on its sides and in the upper part and, therefore, its rigid fastening in the design position. A plate with a flat horizontal shell and flat inclined shells having a central angle θ (Fig. 9) is designed to compact the soil above the pipeline or other structural elements, and a safe allowable distance from the shell of the working plate to the surface of the pipeline or structural element in each case is established empirically and taking into account the grain composition of the compacted soil.

The safety factor of the pipeline stability (K _y ), fixed by the proposed method, taking into account the density (ρ _i ) and the angle of internal friction (φ _i ), the height of the backfill soil (h _z ), the diameter and mass of the pipeline (M _Tr ) depending on the level groundwater (GW) must be determined by the following formulas:

- at a groundwater level of up to 0.5 D _tr :

- when the groundwater level is equal to D _Tr :

when the groundwater level changes D _Tr to 0.99 (h ₃ + D _Tr ):

- when the groundwater level is equal to and greater (h ₃ + D _Tr ):

where ρ _Wi and ρ _bi are, respectively, the density of non-irrigated and irrigated soil, t / m ³ ; φ _w and φ _вi - respectively, the angle of internal friction of non-irrigated and irrigated soil, deg; M is the mass of the pipeline, t; h _in - the height of the water layer above the top of the pipeline, m; ρ _in - the density of water, t / m ³ .

Claims (1)

A method of securing pipelines, including driving a single-stage profile of a trench, laying a pipeline in it, securing a pipeline, filling the pipeline with soil, characterized in that, in order to reduce the cost of securing the pipeline laid in irrigated and non-irrigated soils, and increased reliability of its operation, the trench is arranged step profile, and the upper step, which is the trench backfill, is a rectangular or trapezoidal profile, and the bottom is rectangular profile, then the base under the pipeline is rammed with a ram, equipped with a working plate with a convex shell with a radius equal to the outer diameter of the pipeline, while the rectangular profile of the lower trench stage changes to semicircular, then the pipeline is laid in the lower stage of the trench of the semicircular profile, then layer-by-layer backfill is performed trenches with soil on both sides of the pipeline and leveling the soil, and the thickness of the first backfill layer is assumed to be equal to from one fifth to half diameter of the pipeline, then the first soil layer is compacted with a rammer equipped with a working plate with a concave shell with a radius equal to the outer diameter of the pipeline, then the second and subsequent layers are filled and compacted like the first and the same rammer until until after compaction of the next layer its height above the pipeline becomes 0.3 m, and the thickness of each layer should be equal to one fifth to half the diameter of the pipeline, and the seal of the last layer ave to rammers made with a flat working plate, after reaching the height of the last layer over the pipeline a value equal to not less than 0.3 m, the trench is refilled through and compactors compacted with a flat working plate or vibratory rollers.

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