RU2274792C1 - Method of repairing underground pipeline - Google Patents

Abstract

FIELD: pipeline engineering.

SUBSTANCE: method comprises stripping the pipeline to define pits of specified depth and length below it, trenching under the pipeline, removing soil, and repairing damaged sections of the pipeline. The pits are filled with loose material. A minimum possible stress gradient along the sections is provided.

EFFECT: enhanced quality and safety of repairing.

3 cl, 4 dwg

Description

The invention relates to the field of construction and repair of trunk pipelines of underground laying on sagging and washed out areas in the channels of small water barriers.

A known method of repairing sagging and washed out sections of the pipeline, including opening the repaired section of the pipeline, deepening the trench under it, its subsequent laying at new elevations and backfilling with soil [1].

The disadvantage of this method is that the deepening of the pipeline causes an increase in bending moments, reaching a maximum value at the ends of the planted section, and the erosion of the bottom of the trench causes uncontrolled bending stresses when laying the pipeline, which reduces its operational reliability.

There is another method for repairing sagging and washed out sections of pipelines, which we have taken as a prototype, which includes opening the repaired pipeline in parts, starting at the ends of the section, forming pits under the pipeline of calculated depth and length, filling the pits with bulk material, developing a trench under the pipeline by the calculated value, followed by soil extraction, the formation of support and water-retaining bridges that limit the channel part of the site, digging a drainage sleeve with the organization of a watercourse is the bank part, development in line with the trench isolation repair, cutting with water-detention setting jumpers prigruzki, simultaneous cutting of the support webs and with a final restoration channel trench backfilling [2].

The disadvantages of the method adopted as a prototype are as follows:

1. The probability of the presence of pipes with metal damage on the repaired section, the increase in stresses in which may cause their destruction during repair or subsequent operation, is not taken into account.

2. The distance between the supporting jumpers is determined without taking into account the presence of pipes with metal damage, which limit the maximum use of the bending strength of the pipeline.

3. When replanting a pipeline section, the actual stresses from the longitudinal load, bending moment and internal pressure in the local sections may exceed the calculated values due to unevenness of the bottom of the trench, as well as the presence of curves of elbows of elastoplastic bending and pipes welded at an angle.

4. In the channel part, the actual profile of the planted area may differ from the calculated shape due to the fact that when the water-retaining bridges are cut off, the water rushing into the trench of the channel part causes soil and erodes the trench, which causes insufficient deepening of the pipeline in the channel, which is compensated only by excessive loading and introduction of the pipeline in poorly structured water-saturated soil. As a result, the bending stresses in this place are not controlled and can exceed the permissible value, which reduces the safety of repairs and the operational reliability of the pipeline.

5. The load after cutting off the jumpers in the flooded part of the section can practically be carried out only by “saddle-shaped” reinforced concrete weights installed on top of the pipeline. Such weights are prone to flushing with a stream of water and tipping over, especially with non-projected deepening of the pipeline in the channel of the trench and a high level of groundwater, for example, during the flood period, which reduces the reliability of the pipeline.

6. The lack of manufacturability of the trench development operation in the channel, due to the complexity of extracting water-saturated soil, the impassability of the entrances for equipment to the channel and the low speed due to the constant drainage of water into the trench.

The objective of the invention is to reduce the volume of earthwork in flooded and loosely coupled soils of the channel and the near-river part of the water barrier, simplifying, improving the quality and safety of repair and operational reliability of the pipeline.

The task in the known method of repairing sagging and washed out sections of an underground pipeline, including opening the repaired pipeline in parts, starting from the ends of the section, forming pits under the pipeline of calculated depth and length, filling the pits with bulk material, developing a trench under the pipeline by the calculated value, followed by soil extraction, formation of support bridges, digging of a drainage sleeve with organization of a watercourse outside the channel part, development of a trench in the channel with repair of insulation and, at the same time, cutting the supporting bridges, restoring the channel with the final filling of the trench, it is decided that after opening the pipeline the damage to the metal of the pipes is determined by non-destructive testing methods, the damaged pipes are repaired, the supporting bridges are formed without critically damaged pipes being detected, while under the damaged pipes they form additional supporting jumpers, drainage sleeve is performed so that the water level in the sleeve is below the surface of the pipeline in a seated position above p by the decree, a drainage pit is dug in the near-river part, after cutting the jumpers, the stresses in the pipeline are measured by non-destructive testing methods, by leveling the bottom of the trench, the voltage value in the pipeline is not more than normative, and on damaged pipes they provide the minimum possible voltage gradient along the length of these pipes.

The problem is also solved by the fact that as a non-destructive testing method for measuring stresses in the pipeline metal, the method of measuring coercive force is used.

The problem is also solved by the fact that as a non-destructive testing method to determine the damage to the metal of the pipeline, the method of measuring coercive force is used.

The problem is also solved by the fact that the minimum distance between the water level in the drainage sleeve and the surface of the pipeline above the sleeve is determined based on the probability of increasing the water level during repair, cohesive and filtering properties of the soil.

The following features of the invention are not known to the applicant from patent and scientific and technical information:

- after opening the pipeline, damage to the metal of the pipes is determined by non-destructive testing methods and repair damaged pipes;

- supporting jumpers form, provided that critically damaged pipes are not detected;

- under the damaged pipes form additional supporting jumpers;

- drainage sleeve is performed so that the water level in the sleeve is lower than the surface of the pipeline in a seated position above the sleeve;

- a drainage pit is being dug in the riverbed part;

- after cutting the jumpers, the stresses in the pipeline are measured by non-destructive testing methods;

- leveling the bottom of the trench provides stress in the pipeline no more than a standard value;

- on damaged pipes provide the minimum possible stress gradient along the length of these pipes;

- as a non-destructive testing method for measuring stresses in the pipeline metal, the method of measuring coercive force is used;

- as a non-destructive testing method to determine the damage to the metal of the pipeline, the method of measuring coercive force is used;

- the minimum distance between the water level in the drainage sleeve and the surface of the pipeline above the sleeve is determined based on the probability of increasing the water level during repair, cohesive and filtering properties of the soil.

The essence of the method is presented in figures 1-4 and in the table.

Figure 1 shows the profile of the repaired section of the pipeline in two positions: 1 - before repair, 2 - after repair, and before repair, the pipeline was in the mainstream of the water barrier 3. In position 1, the pipeline rests on the supporting jumpers 4. At the end sections of the pipeline, pits are made 5, filled with bulk material 6. A drainage sleeve 7 with a water level of 8 passes under the pipeline.

Figure 2 shows a top view with the outline of the channel of the water barrier 3, the drainage sleeve 7, the protective dam 9 and the drainage pit 10.

Figure 3 and 4 presents two graphs of stresses, respectively, over the entire repaired area and along the length of the damaged pipe: 11 - stresses in the pipeline after cutting the supporting jumpers; 12 - stresses in the pipeline after leveling the bottom of the trench. The location of the damaged pipe 13 and the standard value of the stresses 14 are also shown.

The table shows the scale of metal damage, which determines the degree of damage to the pipes.

The method is implemented as follows. Measure the initial position 1 of the pipeline in the blurry area (figure 1). Set the required depth of the pipeline in the channel of the water barrier. Calculation of the parameters of replanting is carried out, determining the length of the section, the marks of the bottom of the trench in position 2 of the pipeline, the required number of supporting jumpers 4, loads, force factors affecting the pipeline in end sections, the dimensions of the pit, and the deformation characteristics of bulk material. Starting from the ends of the section, a trench is developed to a depth of up to the calculated position 2 of the pipeline, forming pits 5 with bulk material 6. After opening the outside of the section, the degree of damage to the metal of the pipes is determined by non-destructive testing methods, divided into three categories (see table): without damage damaged, critically damaged. Repair damaged pipes. If critical pipes are not detected, the estimated number of supporting jumpers 4 and one additional bridge under each identified damaged (repaired) pipe are formed. Dig a drainage sleeve 7 with the organization of a watercourse using a dam 9 outside the channel portion of section 3 so that the water level in the hose 7 is below the surface of the pipeline in position 2 above the sleeve by a distance Δf, which is necessary to avoid the penetration of water from the sleeve 7 into the channel section 3 after replanting the pipeline. In the near-river part, a drainage pit 10 is dug with the organization of a water stream with weakly connected soil from the channel part of section 3. A trench is developed in the channel and insulation repair is carried out. Determine the degree of damage to the metal of the pipes in the channel part of the site. Repair damaged pipes. At the same time, the supporting jumpers 4 are cut off. Clamp-like weights are installed on the channel part of the section (not shown in FIG. 1) or the pipeline is fixed to the bottom of the trench using anchor devices (not shown in FIG. 1). Determine the voltage 11 (figure 3) in the pipeline by non-destructive testing methods. Mark the location of the pipeline sections, on which the stresses exceed the standard value of 14. Stage-by-stage aligning the bottom of the trench on the marked sections and determining the stresses in the pipeline, achieve a maximum voltage of 12 standard values 14. Under the damaged pipes 13, the bottom of the trench is aligned in such a way as to ensure the lowest possible voltage gradient along the length of these pipes (figure 4). This creates optimal conditions for the operation of the repaired pipe and repair structure. They fill the channel part of the trench and pit the soil, restore the channel of the water barrier and fill the non-channel part of the trench.

Example.

It is necessary to repair a section of the pipeline with a diameter of 1220 × 12 mm from steel grade 17G1S. The standard value of the voltage at which the operation of the pipeline is allowed, according to [3] is 335 MPa. The width of the water barrier is 20 m.

After development, trenches at the ends of the section form pits 5 (Fig. 1) filled with a mixture of sand and peat 6. Open the outside section of the section and determine the degree of damage to the pipe metal by non-destructive testing, for example, coercimetric [4], divided into three categories (see tab.): without damage, damaged, critically damaged.

It is established that the out-of-channel part does not have critically damaged pipes, however, according to the scale of damage to the metal structure (see table), pipe 13 (Fig. 3) has local damage to the metal structure. The value of the coercive force in the area of damage is 6.2 ... 7.5 A / cm, so the pipe is classified as damaged. Repair the damaged area by installing a repair structure such as a reinforcing coupling with a bolted connection.

Form supporting jumpers 4 (figure 1). Additionally, one jumper is formed under the repaired pipe 13. Dig a drainage sleeve 7 with the organization of a water stream using a dam 9 outside the channel portion of section 3 so that the water level in the sleeve 8 is below the surface of the pipeline in position 2 (Fig. 1) over the sleeve at a distance Δf = 1 m. In the near-river part, a drainage pit 10 is dug, with dimensions (length × width) 15 × 15 meters and a depth of 4 meters, with the organization of a watercourse that is filled with water with poorly connected soil from the channel part of section 3, allowing trench development usle and to repair the insulation. The coercimetric method determines that the channel part of the gas pipeline section does not have critically damaged and damaged pipes. Cut the supporting jumpers 4 (figure 1). After that, clamp-shaped weights with a bolted connection are installed on the channel part of the site. Determine the voltage 11 (figure 3) in the pipeline by non-destructive testing methods with a step of 5 m by the value of the anisotropy of the coercive force [5]. The location of the local segment of the section on which the stresses exceed the standard value of 335 MPa with a longitudinal coordinate of 170 ... 200 m is noted. The maximum stresses of 370 MPa are fixed at a point with a coordinate of 195 m.

By leveling the bottom of the trench under the pipeline in the marked section, the stresses in the pipeline are periodically monitored and they are reduced below 335 MPa. Curve 12 (figure 3) shows that the stress does not exceed 300 MPa. Then control the stress on the pipeline sections adjacent to the alignment of the bottom of the trench. So, it was noted that at a point with a coordinate of 220 m, the stresses as a result of changing the section profile of 170 ... 200 m increased from 200 to 300 MPa, but they did not exceed the standard value.

Determine the voltage 11 in the damaged pipe 13 (figure 3) by the value of the anisotropy of the coercive force in increments of 2 m (figure 4). It is expected that the maximum stress gradient along the pipe length is 25 MPa / m between points with coordinates of 6 and 8 m. By aligning the bottom of the trench under the damaged pipe and periodically monitoring the stresses, the minimum possible stress gradient of 5 MPa / m is obtained (determined by curve 12) , thereby minimizing the magnitude of bending stresses.

After that, the channel part of the trench is filled up and the foundation pit is covered with soil, the channel of the water barrier is restored and the outside channel part of the trench is covered.

The effect of the invention is as follows. Determination of damage to pipe metal in the repaired area before the formation of supporting jumpers, i.e. at the moment when the pipeline does not have loads exceeding the operational ones before the repair is carried out, it allows to increase the safety of the repair and further operation. Measurement of stresses in the pipeline and alignment of the bottom of the trench under the pipeline does not allow exceeding the standard value of stress and ensures minimal bending stresses in the damaged and repaired pipes, creating optimal conditions for the pipe to work together with the repair structure, which increases the reliability of the pipeline. The removal of residual water from the channel after the organization of the watercourse along the sleeve using the drainage pit and the special location of the drainage sleeve provides easy access for equipment and people to the pipeline in the channel for trench development, re-insulation, voltage measurement, loading of the pipeline or fixing it with anchor devices, which increases the speed and quality of ongoing repairs.

Claims (4)

1. A method of repairing sagging and eroded sections of an underground pipeline, including opening the repaired pipeline in parts, starting from the ends of the section, forming pits under the pipeline of the calculated depth and length, filling the pits with bulk material, developing a trench under the pipeline by the calculated value with subsequent extraction of soil, forming support lintels, digging a drainage sleeve with the organization of a watercourse outside the channel, the development of a trench in the channel with the repair of insulation, simultaneous cutting of support x bridges, restoration of the channel with the final filling of the trench, characterized in that after opening the pipeline the damage to the metal of the pipes is determined by non-destructive testing methods, the damaged pipes are repaired, the supporting bridges are formed if critically damaged pipes are not identified, and additional supporting bridges are formed under the damaged pipes, drainage the sleeve is configured to have the water level in the sleeve below the surface of the pipeline in a seated position above the sleeve, in bed part drainage ditch digging, after cutting webs measured voltage in line NDT methods, leveling of the trench bottom provide a voltage value in the pipeline no more regulatory, and on damaged pipes provide the smallest possible voltage gradient along the length of these tubes. 2. The pipeline repair method according to claim 1, characterized in that the method of measuring coercive force is used as a non-destructive testing method for measuring stresses in the metal of the pipeline. 3. The pipeline repair method according to claim 1, characterized in that the method of measuring coercive force is used as a non-destructive testing method to determine the damage to the metal of the pipeline. 4. The method of repairing a pipeline according to claim 1, characterized in that the minimum distance between the water level in the drainage sleeve and the surface of the pipeline above the sleeve is determined based on the probability of increasing the water level during repair, cohesive and filtering properties of the soil.

Images