Owners of patent RU 2653277:

The invention relates to pipeline transport and can be used in the construction and/or reconstruction of main pipeline crossings through natural and artificial obstacles constructed using trenchless methods. In the proposed method, filling the annulus space with solution is carried out in stages. At each stage, the solution is pumped into the annulus and after the solution has solidified, the solution of the next stage is supplied. Filling of the annular space is carried out by means of two injection pipelines, which are supplied into the annular space from one of the ends of the tunnel passage at a distance L. To fill the annular space, a solution is used with a density of at least 1100 kg/m 3, a Marsh viscosity of no more than 80 s and time setting time of at least 98 hours. Technical result: improving the quality of filling the interpipe space with plastic material when organizing tunnel crossings of the main pipeline under natural or artificial obstacles, mainly filled with water, by creating a continuous, void-free, plastic damper that prevents damage to the pipeline during possible mechanical or seismic impacts. 5 salary f-ly, 4 ill.

Method of filling the interpipe space of a tunnel transition of a main pipeline with a solution

Field of technology to which the invention relates

The invention relates to pipeline transport and can be used in the construction and/or reconstruction of main pipeline crossings through natural and artificial obstacles constructed using trenchless methods.

State of the art

A method of manufacturing a system for crossing a main pipeline across a road is known from the prior art, which consists of placing the pipeline under the road in a protective casing and ensuring the tightness of the interpipe space between the pipeline and the protective casing using end seals. In this case, the interpipe space between the pipeline and the protective casing is filled with liquid plastic mass based on synthetic high-molecular compounds (patent RU 2426930 C1, publication date 08/20/2011, IPC F16L 7/00).

The disadvantage of this known method is its narrowly targeted use on short-length crossings, mainly under automobile and railways with a straight gasket profile. In addition, the above method is not applicable to the implementation of work on filling the interpipe space in tunnel crossings with the possibility of simultaneous displacement of water.

The essence of the invention

The problem to be solved by the claimed invention is to create a plastic damper in the interpipe space that prevents damage to the pipeline under possible mechanical and seismic influences.

The technical result achieved by implementing the claimed invention is to improve the quality of filling the interpipe space with plastic material when organizing tunnel crossings of the main pipeline under natural or artificial obstacles, mainly filled with water, by creating a continuous, void-free, plastic damper that prevents damage to the pipeline during possible mechanical or seismic impacts.

The claimed technical result is achieved due to the fact that the method of filling the annulus space of the tunnel transition of the main pipeline with a solution is characterized by the fact that the filling of the annulus space with the solution is carried out in stages, at each stage the solution is pumped into the annulus space and after the solution has hardened, the solution of the next stage is supplied, while filling the annulus spaces are carried out by means of two injection pipelines, which are supplied into the annulus from one of the ends of the tunnel passage to a distance L, while to fill the annulus a solution is used with a density of at least 1100 kg/m 3, a Marsh viscosity of no more than 80 s and time setting time of at least 98 hours.

In addition, in a particular case of implementation of the invention, the distance L is 0.5-0.7 of the length of the tunnel passage.

In addition, in a particular case of implementing the invention, an auxiliary pit is additionally constructed for installing a horizontal directional drilling machine that supplies injection pipelines into the annulus.

In addition, in a particular case of implementing the invention, the injection pipelines are equipped with roller or rollerless support-guide rings, ensuring unhindered movement of the injection pipelines in the interpipe space.

In addition, in a particular case of implementing the invention, as the interpipe space is filled, the injection pipelines are removed from the interpipe space.

In addition, in the particular case of implementing the invention, in the process of supplying injection pipelines into the annulus, continuous monitoring of their supply speed and visual control position relative to the pipeline.

Information confirming the implementation of the invention

In Fig. 1 shows a general view of the receiving pit with injection pipelines;

in Fig. Figure 2 shows a general view of a tunnel passage under a water obstacle with injection pipelines placed;

in Fig. 3 shows a tunnel passage with placed injection pipelines (cross section);

in Fig. Figure 4 shows a general view of the roller support-guide ring (cross section).

Positions in the drawings have the following designations:

1 - interpipe space;

1 1 - tunnel passage;

2 - natural obstacle;

3 - receiving (starting) pit;

4 - auxiliary pit;

5 - horizontal directional drilling machine;

6 - wall of the receiving (starting) pit;

7 - technological hole in the wall of the receiving (starting) pit;

8 - discharge pipelines;

9 - support table;

10 - roller bearings;

11 - roller support-guide rings;

12 - pipeline;

13 - steel clamp of the support-guide ring;

14 - spacer friction material of the support-guide ring;

15 - rollers of the support-guide ring;

16 - roller holders;

17 - tunnel lining;

18 - pumping station.

The method is implemented as follows.

Before carrying out work to fill the interpipe space 1 of tunnel passages 1 1 of main pipelines through natural or artificial obstacles 2, built using trenchless methods (microtunneling), auxiliary technological work is carried out (Fig. 1). Next to the receiving (starting) pits 3, made at both ends of the tunnel passage 1 1, auxiliary pits 4 are built for the installation of a horizontal directional drilling machine 5 for supplying injection pipelines, for example, a horizontal directional drilling machine (HDD) and other auxiliary equipment (not shown). In the wall 6 of the receiving (starting) pit 3, using a diamond wall cutter (not shown), technological holes 7 with dimensions of 1.0×1.0 m are cut through which two injection pipelines 8 are passed, intended for supplying filler, prepared in the form of a solution, into annulus space 1. In the receiving (starting) pit 3, a support table 9 with roller supports 10 is installed, ensuring smooth supply of injection pipelines 8 into the annulus 1. In a preferred embodiment of the invention, the method can be used both in the organization of tunnel transitions 1 1 having a straight line gasket profile, and when organizing tunnel passages 1 1 having a curved gasket profile, including essentially inclined end parts and an essentially rectilinear central part. The discharge pipeline 8 is a collapsible pipeline made, for example, from polyethylene pipes.

The solution is supplied to the interpipe space 1 (Fig. 2) through at least two injection pipelines 8, the laying of which begins from one of the ends of the tunnel passage 1 1 filled with water. The laying of injection pipelines 8 is carried out at a distance L, preferably amounting to 0.5-0.7 of the length of the tunnel transition 1 1 , which ensures the possibility of supplying the solution to the required zone of the annular space 1 and uniform filling of the annular space 1 without the formation of voids with simultaneous displacement of water in the direction receiving pit 3, located at the end of the tunnel passage, from which the filling of the interpipe space begins. The supply of injection pipelines 8 into the annulus 1 is carried out using a horizontal directional drilling machine 5 and several roller support-guide rings 11 installed on the injection pipelines 8 (Fig. 3), or rollerless support-guide rings (not shown). The roller support-guide ring 11 (Fig. 4) includes a steel clamp 13 installed on the discharge pipeline 8 through a friction gasket 14, which ensures reliable fixation of the ring 11 with the pipeline 8, at least four polyurethane wheels (rollers) 15 installed in holders 16, preferably at an angle of 90° to each other. In this case, at least two rollers 15 rest on the surface of the tunnel lining 17, and at least one of the rollers 15 rests on the surface of the pipeline 12, which ensures smooth movement of the injection pipelines 8 along the surface of the pipeline 12 in the interpipe space 1 in a given direction (Fig. 3). The use of at least two injection pipelines 8 allows the interpipe space 1 to be uniformly filled with solution on both sides of the pipeline 12, which allows maintaining the design position of the pipeline. To prevent pipeline 12 from “floating up,” the interpipe (tunnel) space 1 is filled with solution in stages. At each stage, the solution is injected into the annulus 1, where it hardens and acquires its strength properties, and only after that the solution of the next stage is supplied. Thus, a continuous, uniform filling of the annular space 1 with solution is ensured, with simultaneous displacement of water into the receiving pit 3 with its subsequent pumping out using a pumping station 18. As the annular space 1 is filled with solution, the injection pipelines 8 are removed from the annular space 1. After this, similar operations to fill the remaining part of the annular space 1 are carried out from the other end of the tunnel passage 1 1 . In this case, the laying of injection pipelines 8 is carried out at a distance from the part of the tunnel passage 1 that is not filled with solution.

The use of the proposed method ensures the possibility of continuous, uniform filling of the interpipe space of the tunnel transition 1 1 without the formation of voids. In addition, the method of filling the interpipe space 1 allows work to be carried out at an operating transition of the main pipeline without stopping the pumping of the product.

To ensure continuous monitoring of the movement and position of the injection pipelines 8 when moving in the annulus 1, as well as assessing the general condition of the annulus 1, video recording means, for example a web camera (not shown), can be installed on the injection pipelines 8. When the injection pipelines 8 move in the tunnel passage 1 1, the image from the video recording device in real time is sent to the information display device located in the horizontal directional drilling machine 5 (not shown). Based on the information received, the operator can limit the flow rate of the injection pipes 8 depending on the actual position of the outlet openings of the injection pipes 8, for example, if any obstacles are detected or the injection pipes 8 deviate from the specified path.

To create a plastic damper that prevents damage to the pipeline 12 under seismic influences, a solution with sufficient strength and elastic-plastic properties is used as a filler. Interpipe space 1 is filled with a solution prepared on the basis of bentonite cement powder with the addition of polymers. As a result of the solidification of the solution, a material is formed that has sufficient strength and elastic-plastic properties and makes it possible to protect the pipeline 12 from possible mechanical and seismic influences. Mixing stations (not shown) are used to prepare the solution. To ensure the required characteristics of the material, the solution must satisfy the following characteristics: solution density of at least 1100 kg/m 3 ; conditional viscosity of the solution according to Marsh is no more than 80 s; Setting time (loss of mobility) is at least 98 hours.

After filling the interpipe space 1, auxiliary technological work is carried out: installation of sealing jumpers at the ends of the tunnel passage (not shown), dismantling of injection pipelines 8 and auxiliary equipment, sealing of the technological hole 7 in the wall 6 of the receiving (starting) pit 3 and backfilling of the auxiliary pit 4.

Thus, the inventive method ensures continuous, without the formation of voids, filling of the interpipe space with plastic material by supplying the solution through injection pipelines with the possibility of simultaneous displacement of water (if necessary) at the transitions of main pipelines through natural and artificial obstacles, built using trenchless methods (microtunnelling).

1. A method of filling the annulus space of a tunnel transition of a main pipeline with a solution, characterized in that the annulus space is filled with a solution in stages, at each stage the solution is pumped into the annulus space and after the solution has solidified, the solution of the next stage is supplied, while the annulus space is filled using two injection pumps pipelines that are supplied to the annulus space from one end of the tunnel transition at a distance L, while to fill the annulus space a solution is used with a density of at least 1100 kg/m 3, a Marsh viscosity of no more than 80 s and a setting time of at least 98 hours .

2. The method according to claim 1, characterized in that the distance L is 0.5-0.7 the length of the tunnel passage.

3. The method according to claim 1, characterized in that they additionally construct an auxiliary pit for installing a horizontal directional drilling machine that supplies injection pipelines into the annulus.

4. The method according to claim 1, characterized in that the injection pipelines are equipped with roller or rollerless support-guide rings, ensuring unhindered movement of the injection pipelines in the interpipe space.

5. The method according to claim 1, characterized in that as the interpipe space is filled, the injection pipelines are removed from the interpipe space.

6. The method according to claim 1, characterized in that during the supply of injection pipelines into the annulus, continuous monitoring of their supply speed and visual monitoring of their position relative to the pipeline are provided.

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The invention relates to pipeline transport and can be used in the construction or reconstruction of main pipeline crossings through natural and artificial obstacles constructed using trenchless methods. In the proposed method, filling the annulus space with solution is carried out in stages. At each stage, the solution is pumped into the annulus and after the solution has solidified, the solution of the next stage is supplied. Filling of the annulus space is carried out by means of two injection pipelines, which are supplied into the annulus space from one of the ends of the tunnel passage at a distance L. To fill the annulus space, a solution is used that has a density of at least 1100 kgm3, a Marsh viscosity of no more than 80 s and a setting time of at least 98 hours. Technical result: improving the quality of filling the interpipe space with plastic material when organizing tunnel crossings of the main pipeline under natural or artificial obstacles, mainly filled with water, by creating a continuous, void-free, plastic damper that prevents damage to the pipeline under possible mechanical or seismic influences . 5 salary f-ly, 4 ill.

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Bortsov Alexander Konstantinovich. Construction technology and methods for calculating the stress state of underwater pipelines “pipe in pipe”: IL RSL OD 61:85-5/1785

Introduction

1. Design of an underwater pipeline “pipe in pipe” with an interpipe space filled with cement stone 7

1.1. Double-pipe pipeline designs 7

1.2. Technical and economic assessment of the underwater transition of the pipe-to-pipe pipeline 17

1.3. Analysis of completed work and setting research objectives 22

2. Technology for cementing the interpipe space of pipe-in-pipe pipelines 25

2.1. Materials for cementing the annulus 25

2.2. Selection of cement mortar formulation 26

2.3. Cementing equipment 29

2.4. Filling the annulus 30

2.5. Cementing calculation 32

2.6. Experimental testing of cementing technology 36

2.6.1. installation and testing of a two-pipe rubbing horse 36

2.6.2. Cementing the annulus 40

2.6.3. Pipeline strength testing 45

3. Stress-strain state of three-layer pipes under internal pressure 50

3.1. Strength and deformation properties of cement stone 50

3.2. Stresses in three-layer pipes when cement stone perceives tangential tensile forces 51

4. Experimental studies of the stress-strain state of three-layer pipes 66

4.1. Methodology for conducting experimental studies 66

4.2. Model manufacturing technology 68

4.3. Test stand 71

4.4. Methodology for measuring deformations and testing 75

4.5. The influence of excess cementing pressure of the mek-pipe space on the redistribution of stresses 79

4.6. Checking the adequacy of theoretical dependencies 85

4.6.1. Methodology for planning an experiment 85

4.6.2. Statistical processing of test results! . 87

4.7. Testing of full-scale three-layer pipes 93

5. Theoretical and experimental studies bending rigidity of pipe-in-pipe pipelines 100

5.1. Calculation of bending stiffness of pipelines 100

5.2. Experimental studies of flexural stiffness 108

Conclusions 113

General conclusions 114

Literature 116

Applications 126

Introduction to the work

In accordance with the decisions of the XXII Congress of the CPSU in the current five-year plan at an increased pace The oil and gas industries are developing, especially in the regions of Western Siberia, in the Kazakh SSR and in the north of the European part of the country.

By the end of the five-year period, oil and gas production will be 620-645 million tons and 600-640 billion cubic meters, respectively. meters.

To transport them, it is necessary to construct powerful main pipelines with a high degree of automation and operational reliability.

One of the main tasks in the five-year plan will be the further accelerated development of oil and gas fields, the construction of new ones and increasing the capacity of existing gas and oil transport systems running from the regions of Western Siberia to the main places of oil and gas consumption - in the Central and Western regions of the country. Pipelines of considerable length will cross a large number of different water barriers along their path. Crossings over water barriers are the most complex and critical sections of the linear part of main pipelines, on which the reliability of their operation depends. When underwater crossings fail, enormous material damage is caused, which is defined as the sum of damage to the consumer, the transport enterprise and from environmental pollution.

Repairing and restoring underwater crossings is a complex task that requires significant effort and resources. Sometimes the costs of repairing a crossing exceed the costs of its construction.

Therefore, great attention is paid to ensuring high reliability of transitions. They must operate without failures or repairs throughout the entire design life of the pipelines.

Currently, to increase reliability, crossings of main pipelines through water barriers are constructed in a two-line design, i.e. parallel to the main thread, at a distance of up to 50 m from it, an additional one is laid - a reserve one. Such redundancy requires double the capital investment, but as operating experience shows, it does not always provide the necessary operational reliability.

Recently, new design schemes have been developed that provide increased reliability and strength of single-strand transitions.

One such solution is the design of an underwater pipeline transition “pipe in pipe” with an interpipe space filled with cement stone. A number of crossings have already been built in the USSR using the “pipe-in-pipe” design scheme. Successful experience in the design and construction of such crossings indicates that the smoldering theoretical and Constructive decisions the technology of installation and laying, quality control of welded joints, and testing of two-pipe pipelines are sufficiently developed. But, since the inter-pipe space of the constructed transitions was filled with liquid or gas, the issues related to the peculiarities of the construction of underwater transitions of “pipe-in-pipe” pipelines with an inter-pipe space filled with cement stone are essentially new and poorly understood.

Therefore, the purpose of this work is the scientific substantiation and development of technology for the construction of underwater pipelines “pipe in pipe” with an interpipe space filled with cement stone.

To achieve this goal, a large program was carried out

theoretical and experimental research. The possibility of using sub-tubes to fill the annulus space is shown.

water pipelines "pipe in pipe" materials, equipment and technological methods, used in cementing wells. An experimental section of a pipeline of this type was built. Formulas are derived for calculating stresses in three-layer pipes under the action of internal pressure. Experimental studies of the stress-strain state of three-layer pipes for main pipelines were carried out. A formula has been derived for calculating the bending stiffness of three-layer pipes. The bending rigidity of a pipe-in-pipe pipeline was experimentally determined.

Based on the research carried out, “Temporary instructions for the design and construction technology of pilot-industrial underwater gas pipeline crossings for a pressure of 10 MPa or more of the “pipe-in-pipe” type with cementation of the interpipe space” and “Instructions for the design and construction of offshore underwater pipelines according to the design scheme” were developed. pipe in pipe" with cementation of the interpipe space", approved by Mingazprom in 1982 and 1984.

The results of the dissertation were practically used in the design of the underwater passage of the Urengoy - Uzhgorod gas pipeline through the Pravaya Khetta river, the design and construction of sections of the Dragobych - Stryi and Kremenchug - Lubny - Kyiv oil and product pipelines, sections of the Strelka 5 - Bereg and Golitsyno - Bereg offshore pipelines.

The author thanks the head of the Moscow underground gas storage station of the Mostransgaz production association O.M. Korabelnikov, head of the laboratory of strength of gas pipelines at VNIIGAZ, Ph.D. tech. Sciences N.I. Anenkov, head of the well fastening detachment of the Moscow deep drilling expedition O.G. Drogalin for assistance in organizing and conducting experimental studies.

Technical and economic assessment of the underwater transition of the pipe-to-pipe pipeline

Pipe-in-pipe pipeline crossingsTransitions of main pipelines through water barriers are among the most critical and complex sections of the route. Failures of such transitions can cause a sharp decrease in productivity or a complete stop in pumping the transported product. Repair and rehabilitation of subsea pipelines are complex and expensive. Often the costs of repairing a crossing are comparable to the costs of building a new crossing.

Underwater crossings of main pipelines in accordance with the requirements of SNiP 11-45-75 [70] are laid in two threads at a distance of at least 50 m from one another. With such redundancy, the likelihood of failure-free operation of the crossing as a transport system as a whole increases. The costs of building a reserve line, as a rule, correspond to the costs of building the main line or even exceed them. Therefore, we can assume that increasing reliability through redundancy requires doubling capital investment. Meanwhile, operating experience shows that this method of increasing operational reliability does not always give positive results.

The results of studying the deformations of channel processes showed that the zones of channel deformations significantly exceed the distances between the laid passages. Therefore, erosion of the main and reserve threads occurs almost simultaneously. Consequently, increasing the reliability of underwater crossings should be carried out in the direction of carefully taking into account the hydrology of the reservoir and developing crossing designs with increased reliability, in which the failure of the underwater crossing was taken to be an event leading to a violation of the tightness of the pipeline. During the analysis, the following design solutions were considered: double-strand single-pipe design - pipeline strings are laid in parallel at a distance of 20-50 m from one another; underwater pipeline with continuous concrete covering; pipeline design “pipe in pipe” without filling the interpipe space and filled with cement stone; a passage constructed using the inclined drilling method.

From the graphs shown in Fig. 1.10, it follows that the highest expected probability of failure-free operation is at the underwater transition of a “pipe-in-pipe” pipeline with an annular space filled with cement stone, with the exception of a transition built by the inclined drilling method.

Currently, experimental studies of this method and the development of its basic technological solutions are being carried out. Due to the complexity of creating drilling rigs for directional drilling, it is difficult to expect widespread introduction of this method into pipeline construction practice in the near future. In addition, this method can be used in the construction of crossings of only a short length.

To construct transitions according to the “pipe-in-pipe” structural scheme with an interpipe space filled with cement stone, the development of new machines and mechanisms is not required. When installing and laying two-pipe pipelines, the same machines and mechanisms are used as during the construction of single-pipe pipelines, and to prepare cement mortar and fill the interpipe space, cementing equipment is used, which is used for cementing oil and gas wells. Currently in the system of Shngazprom and the Ministry of Oil and Gas Industry Several thousand cementing units and cement mixing machines are in operation.

Main technical and economic indicators of underwater pipeline crossings various designs are given in Table 1.1. Calculations were performed for the underwater transition of the pilot section of the gas pipeline at a pressure of 10 MPa without taking into account the cost shut-off valves. The length of the transition is 370 m, the distance between parallel threads is 50 m. The pipes are made of X70 steel with a yield strength (et - 470 MPa and tensile strength Є6р = 600 MPa. The thickness of the pipe walls and the necessary additional ballasting for options I, P and Sh are calculated according to SNiP 11-45-75 [70].The thickness of the casing wall in option W is determined for a pipeline of category 3. The hoop stresses in the pipe walls from the operating pressure for the indicated options are calculated using the formula for thin-walled pipes.

In the “pipe-in-pipe” pipeline design with an interpipe space filled with cement stone, the wall thickness of the inner pipe is determined according to the method given in [e], the thickness of the outer wall is taken to be 0.75 of the thickness of the inner one. The hoop stresses in the pipes are calculated according to formulas 3.21 of this work, the physical and mechanical characteristics of the cement stone and pipe metal are taken to be the same as in the calculation of Table. 3.1.The most common two-strand, single-pipe transition design with ballasting with cast iron weights was taken as the comparison standard ($100). As can be seen from table. І.І, the metal consumption of the “pipe-in-pipe” pipeline design with an interpipe space filled with cement stone for steel and cast iron is more than 4 times

Cementing Equipment

The specific features of the work on cementing the annulus of pipe-in-pipe pipelines determine the requirements for cementing equipment. The construction of crossings of main pipelines through water barriers is carried out in various areas of the country, including remote and hard-to-reach ones. The distances between construction sites reach hundreds of kilometers, often in the absence of reliable transport communications. Therefore, cementing equipment must have great mobility and be convenient for transportation over long distances in off-road conditions.

The amount of cement slurry required to fill the annulus can reach hundreds cubic meters, and the pressure when pumping the solution is several megapascals. Consequently, cementing equipment must have high productivity and power to ensure the preparation and injection of the required amount of solution into the annulus within a time not exceeding its thickening time. At the same time, the equipment must be reliable in operation and have sufficiently high efficiency.

The set of equipment intended for cementing wells most fully satisfies the specified conditions [72]. The complex includes: cementing units, cement mixing machines, cement trucks and tank trucks, a station for monitoring and controlling the cementing process, as well as auxiliary equipment and warehouses.

Mixing machines are used to prepare the solution. The main components of such a machine are a bunker, two horizontal unloading augers and one inclined loading auger and a vacuum-hydraulic mixing device. The bunker is usually installed on the chassis of an off-road vehicle. The augers are driven by the vehicle's traction engine.

The solution is pumped into the annulus space using a cementing unit mounted on. chassis of a powerful truck. The unit consists of a cement pump high pressure for pumping the solution, a pump for supplying water and a motor to it, measuring tanks, a pump manifold and a collapsible metal pipeline.

The cementing process is controlled using the SKTs-2m station, which allows you to control the pressure, flow rate, volume and density of the injected solution.

With small volumes of interpipe space (up to several tens of cubic meters), mortar pumps and mortar mixers used for preparing and pumping mortars can also be used for cementing.

Cementing of the annulus space of underwater pipe-in-pipe pipelines can be carried out both after they are laid in an underwater trench, and before they are laid on shore. The choice of location for cementing depends on the specific topographical conditions of construction, the length and diameter of the transition, as well as the availability of special equipment for cementing and laying the pipeline. But it is preferable to cement pipelines laid in an underwater trench.

Cementing of the annulus space of pipelines running in the floodplain (on the shore) is carried out after laying them in a trench, but before backfilling with soil. If additional ballasting is necessary, the annulus space can be filled with water before cementing. The supply of solution into the interpipe space begins from the lowest point of the pipeline section. The outlet of air or water is carried out through special pipes with valves installed on the external pipeline at its highest points.

After the interpipe space is completely filled and the solution begins to flow out, reduce its feed rate and continue pumping until a solution with a density begins to come out of the outlet pipes. equal density pumped" Then the valves on the outlet pipes are closed and excess pressure is created in the interpipe space. Previously, back pressure is created in the internal pipeline, preventing the loss of stability of its walls. When the required excess pressure is reached in the interpipe space, the valve on the inlet pipe is closed. The tightness of the interpipe space and the pressure in the internal pipeline are maintained for the time required for the cement mortar to harden.

When filling, the following methods of cementing the annular space of pipe-in-pipe pipelines can be used: direct; using special cementing pipelines; sectional. This consists of feeding a cement solution into the annular space of the pipeline, which displaces the air or water present in it. The solution is supplied and air or water is discharged through pipes with valves mounted on the external pipeline. The entire pipeline section is filled in one step.

Cementing using special cementing pipelines With this method, small-diameter pipelines are installed in the annulus, through which cement mortar is supplied into it. Cementing is carried out after laying the two-pipe pipeline in an underwater trench. The cement solution is supplied through cementing pipelines to the lowest point of the laid pipeline. This cementing method allows for the highest quality filling of the interpipe space of a pipeline laid in an underwater trench.

Sectional cementing can be used if there is a lack of cementing equipment or high hydraulic resistance when pumping solution, which does not allow cementing the entire pipeline section in one go. In this case, cementing of the annulus is carried out in separate sections. The length of the cementing sections depends on the technical characteristics of the cementing equipment. For each section of the pipeline, separate groups of pipes are installed for injection of cement mortar and outlet of air or water.

To fill the interpipe space of pipe-in-pipe pipelines with cement mortar, it is necessary to know the amount of materials and equipment required for cementing, as well as the time it takes to complete it. The volume of cement mortar required for filling between

Stresses in three-layer pipes when cement stone perceives tangential tensile forces

The stressed state of a three-layer pipe with an interpipe space filled with cement stone (concrete) under the action of internal pressure was considered in their works by P.P. Borodavkin [ 9 ], A. I. Alekseev [ 5 ], R. A. Abdullin when deducing formulas, the authors accepted the hypothesis that a ring made of cement stone perceives tensile tangential forces and its cracking does not occur under loading. Cement stone was considered as an isotropic material having the same modulus of elasticity in tension and compression, and, accordingly, the stresses in a ring of cement stone were determined using Lame's formulas.

An analysis of the strength and deformation properties of cement stone showed that its tensile and compressive moduli are not equal, and the tensile strength is significantly less than the compressive strength.

Therefore, the dissertation work gives a mathematical formulation of the problem for a three-layer pipe with an interpipe space filled with different modulus material, and an analysis of the stress state in three-layer pipes of main pipelines under the action of internal pressure is carried out.

When determining the stresses in a three-layer pipe due to the action of internal pressure, we consider a ring of unit length cut from a three-layer pipe. The stressed state in it corresponds to the stressed state in the pipe when (En = 0. The tangential stresses between the surfaces of the cement stone and the pipes are taken equal to zero, since the adhesion forces between them are insignificant. We consider the inner and outer pipes as thin-walled. A ring made of cement stone in the inter-tube space we consider it to be thick-walled, made of multi-module material.

Let the three-layer pipe be under the influence of internal pressure PQ (Fig. 3.1), then the inner pipe is subject to internal pressure P and external pressure P-g, caused by the reaction of the outer pipe and cement stone to move the inner one.

The outer pipe is subject to internal pressure Pg caused by the deformation of the cement stone. A ring of cement stone is under the influence of internal P-g and external 2 Pressure.

Tangential stresses in the inner and outer pipes under the action of pressures PQ, Pj and Pg are determined by: where Ri, &i, l 2, 6Z are the radii and wall thicknesses of the inner and outer pipes. Tangential and radial stresses in a ring of cement stone are determined by the formulas obtained for solving the axisymmetric problem of a hollow cylinder made of a different-module material under the influence of internal and external pressure ["6]: cement stone under tension and compression. In the given formulas (3.1) and (3.2) the pressure values ​​Pj and P2 are unknown. We find them from the conditions of equality of the radial displacements of the mating surfaces of the cement stone with the surfaces of the inner and outer pipes. The dependence of the relative tangential deformations on the radial displacements (i) has the form [ 53 ] Dependence of the relative deformations from stresses for pipes Г 53 ] is determined by the formula

Test bench

The alignment of the pipes (Fig. 4.2) of the inner I and outer 2 and the sealing of the interpipe space were carried out using two centering rings 3 welded between the pipes. Into the outer pipe vva-. Two fittings 9 were ripped - one for pumping cement mortar into the annulus, the other for air outlet.

The interpipe space of models with a volume of 2G = 18.7 liters. filled with a solution prepared from cement Portland cement for “cold” wells of the Zdolbunovsky plant, with a water-cement ratio W/C = 0.40, density p = 1.93 t/m3, spreadability along the AzNII cone at = 16.5 cm, beginning of setting t = 6 hours 10 clays, end of setting t „_ = 8 hours 50 min”, the tensile strength of two-day cement stone samples for bending & pcs = 3.1 Sha. These characteristics were determined using the standard testing method for Portland cement cement for “cold” wells (_31j.

The compressive and tensile strength limits of cement stone samples at the beginning of testing (30 days after filling the interpipe space with cement mortar) b = 38.5 MPa, b c = 2.85 Sha, modulus of elasticity in compression EH = 0.137 TO5 Sha, Poisson's ratio ft = 0.28. Compression testing of cement stone was carried out on cubic samples with ribs of 2 cm; for tension - on samples in the form of figure eights, with a cross-sectional area at the narrowing of 5 cm [31]. For each test, 5 samples were prepared. The samples hardened in a chamber with 100% relative air humidity. To determine the elastic modulus of cement stone and Poisson's ratio, we used the method proposed by millet. K.V. Ruppeneit [_ 59 J . Tests were carried out on cylindrical samples with a diameter of 90 mm and a length of 135 mm.

The solution was supplied into the annulus of the models using a specially designed and manufactured installation, the diagram of which is shown in Fig. 4.3.

Cement mortar was poured into container 8 with the lid 7 removed, then the lid was put in place and the mortar compressed air were forced into the annulus of model II.

After the intertubular space was completely filled, valve 13 on the outlet pipe of the sample was closed and excess cementing pressure was created in the annular space, which was monitored by pressure gauge 12. Upon reaching the design pressure, valve 10 on the inlet pipe was closed, then the excess pressure was released and the model was disconnected from the installation. During the hardening of the solution, the model was in a vertical position.

Hydraulic tests of three-layer pipe models were carried out on a stand designed and manufactured at the Department of Metal Technology of the Moscow Institute of Economy and State Enterprise named after. I.M.iubkina. The stand diagram is shown in Fig. 4.4, general view - in Fig. 4.5.

Pipe model II was placed in test chamber 7 through side cover 10. The model, installed with a slight slope, was filled with oil from container 13 by centrifugal pump 12, while valves 5 and 6 were open. When the model was filled with oil, these valves were closed, valve 4 was opened and high-pressure pump I was turned on. Overpressure reset by opening valve 6. Pressure control was carried out with two standard pressure gauges 2, designed for 39.24 Mia (400 kgf/slg). To output information from sensors installed on the model, multi-core cables 9 were used.

The stand allowed experiments to be carried out at pressures up to 38 MPa. The high-pressure pump VD-400/0.5 E had a small flow rate of 0.5 l/h, which allowed for smooth loading of the samples.

The cavity of the inner pipe of the model was sealed with a special sealing device, eliminating the influence of axial tensile forces on the model (Fig. 4.2).

The tensile axial forces arising from the action of pressure on the pistons 6 are almost completely absorbed by the rod 10. As shown by strain gauges, a small transfer of tensile forces (approximately 10%) occurs due to friction between the rubber sealing rings 4 and the inner pipe 2.

When testing models with different internal diameters of the inner tube, pistons of different diameters were also used. To measure the deformed state of bodies, they use various methods and means

where ς is a coefficient taking into account the distribution of load and support reaction of the base, ς = 1.3; P pr - calculated external reduced load, N/m, determined accordingly according to the formulas above, for various backfill options, as well as the absence or presence of water in the polyethylene pipeline; R l - parameter characterizing the rigidity of the pipeline, N/m 2:

where k e is a coefficient that takes into account the influence of temperature on the deformation properties of the pipeline material, k e = 0.8; E 0 is the tensile creep modulus of the pipe material, MPa (with 50 years of operation and a stress in the pipe wall of 5 MPa E 0 = 100 MPa); θ is a coefficient that takes into account the combined effect of base resistance and internal pressure:

where E gr is the modulus of deformation of the backfill (backfill), taken depending on the degree of compaction (for CR 0.5 MPa); P is the internal pressure of the transported substance, P< 0,8 МПа.

Consistently substituting the initial data into the main formulas above, as well as into the intermediate ones, we get following results calculation:

Analyzing the obtained calculation results for this case, it can be noted that in order to reduce the value of P pr it is necessary to strive to reduce the value of P" z + P to zero, i.e. equality in absolute value of the values ​​P" z and P. This can be achieved by changing the degree filling with water polyethylene pipeline. For example, with a filling equal to 0.95, the positive vertical component of the water pressure force P on the internal cylindrical surface will be 694.37 N/m at P" z = -690.8 N/m. Thus, by adjusting the filling, data equality can be achieved quantities

Summarizing the test results bearing capacity according to condition II for all options, it should be noted that maximum permissible deformations do not occur in the polyethylene pipeline.

Load-bearing capacity test according to condition III

The first stage of the calculation is to determine the critical value of the external uniform radial pressure P cr, MPa, which the pipe can withstand without losing its stable cross-sectional shape. The value of Pcr is taken to be the smaller of the values ​​calculated using the formulas:

P cr =2√0.125P l E gr = 0.2104 MPa;

P cr = P l +0.14285 = 0.2485 MPa.

In accordance with the calculations using the formulas above, a smaller value of P cr = 0.2104 MPa is accepted.

The next step is to check the condition:

where k 2 is the coefficient of pipeline operating conditions for stability, taken equal to 0.6; Pvac is the value of possible vacuum in the repair section of the pipeline, MPa; Pgv is the external pressure of groundwater above the top of the pipeline, according to the conditions of the problem Pgv = 0.1 MPa.

The subsequent calculation is carried out by analogy with condition II for several cases:

• for the case of uniform filling of the interpipe space in the absence of water in the polyethylene pipeline:

thus, the condition is met: 0.2104 MPa>>0.1739 MPa;

• the same if there is a filler (water) in a polyethylene pipeline:

thus, the condition is met: 0.2104 MPa >>0.17 MPa;

• for the case of uneven filling of the interpipe space in the absence of water in the polyethylene pipeline:

thus, the condition is met: 0.2104 MPa >>0.1743 MPa;

• the same in the presence of water in a polyethylene pipeline:

thus, the condition is met: 0.2104 MPa >>0.1733 MPa.

Testing the load-bearing capacity according to condition III showed that the stability round shape cross-section of the polyethylene pipeline is observed.

As general conclusions, it should be noted that the implementation construction work for backfilling of the interpipe space for the corresponding initial design parameters will not affect the load-bearing capacity of the new polyethylene pipeline. Even under extreme conditions (with uneven backfilling and high groundwater levels), backfilling will not lead to undesirable phenomena associated with deformation or other damage to the pipeline.