This specification is applicable to the design of new projects where crude oil and natural gas pipelines pass through artificial and natural obstacles. SY/T 0015.1-1998 Design Specification for Crude Oil and Natural Gas Pipeline Crossing Projects Crossing Projects SY/T0015.1-1998 Standard download decompression password: www.bzxz.net

1 General Principles
Petroleum and Natural Gas Industry Standards of the People's Republic of China Design Specifications for Crossing and Crossing Projects for Crude Oil and Natural Gas Pipelines Crossing Projects
Approval Department: China National Petroleum Corporation Date of Approval: 1998-04-26
Effective Date: 1998-08-01
SY/T 0015.1—1998
Replaces SYJ15-1985
1.0.1 This specification is formulated to implement the relevant national policies and guidelines in the design of crossing projects for crude oil and natural gas pipelines, to achieve advanced technology, economic rationality, safety and applicability, and to ensure quality. 1.0.2 This specification is applicable to the design of new projects for onshore crude oil and natural gas pipelines crossing artificial or natural obstacles. 1.0.3 In addition to complying with this specification, the design of crossing projects shall also comply with the provisions of the relevant mandatory standards currently in force in the country. 2 Terms
2.0.1 Pipeline crossing engineering Pipeline crossing engineering Construction projects where crude oil and natural gas pipelines pass under artificial or natural obstacles. 2.0.2 Cross section
Pipelines that cross artificial or natural obstacles. 2.0.3 Waterswww.bzxz.net
Naturally formed or artificially constructed rivers, lakes, reservoirs, swamps, fish ponds, canals and other areas. 2.0.4 Gully
Gullies formed by water scouring.
2.0.5 Marine section stabilization Marine section stabilization does not float or shift.
2.0.6 Crossing by directional drilling Laying the crossing section with a directional drill.
2.0.7 To lay bare
The crossing section is laid directly on the water bed. 3 Basic regulations
3.1 Basic data
3.1.1 Before designing a crossing project, the physical properties of the medium being transported and the transportation process parameters must be obtained. The requirements should be implemented in accordance with the provisions of the current national standards "Oil Pipeline Engineering Design Code" GB50253 and "Gas Pipeline Engineering Design Code" GB50251. 3.1.2 Before designing a crossing project, the data required for engineering survey and engineering geology must be obtained according to the design stage. Engineering survey data include 1/200~~1/2000 plane topographic maps (large and medium-sized projects) and cross-sections. Engineering geological reports include 1/200~~1/2000 geological cross-sections, bar graphs, geotechnical indicators, hydrogeology and basic intensity of the ground capsule.
SY/T 0015.1—1998
3.1.3 Before designing a crossing water area project, the consent of the water area authority and hydrological data must be obtained. When a reservoir is built upstream, it is necessary to obtain the flood control dispatching data of the reservoir and the analysis data of the reservoir's impact on the downstream. 3.1.4 Before designing the crossing railway or highway project, the railway or highway authority must agree. 3.2 Materials
3.2.1 The domestic steel pipes used in the crossing project shall comply with the provisions of the current national standard "Technical Conditions for Delivery of Steel Pipes for Transportation in the Petroleum and Natural Gas Industry Part 1: Grade A Steel Pipes" GB/T9711.1, and the toughness requirements shall be proposed according to the steel grade and the design use temperature. 3.2.2 Other steel materials used in the crossing project shall comply with the provisions of the current national standards "Carbon Structural Steel" GB/T700, "Technical Conditions for Hot-rolled Carbon Steel for Bridge Construction" GB/T714 and "Hot-rolled Ribbed Steel Bars for Reinforced Concrete" GB1499. 3.2.3 The cement used in the crossing project shall comply with the provisions of the current national standard "Medium Heat Portland Cement Low Heat Slag Portland Cement" GB200
.
3.2.4 The allowable stress of steel pipes that meet Article 3.2.1 of this Code shall be calculated according to Formula (3.2.4). [o] Fd,
Wherein, [o] is the allowable stress of steel pipes for oil and gas transportation (MPa); the weld coefficient of steel pipes shall be selected according to Table 3.2.4-1; a is the specified yield strength of steel pipes (MPa); F—~---the design coefficient shall be selected according to Table 3.2.4-2. Table 3.2.4-1
Steel pipe standard
GB/T 9711.1
Steel type or steel grade
Yield strength
(MPa)
Crossing pipe section conditions
I and IV grade roads with casing
III and IV grade roads without casing
【, and highways, expressways, railways with casingGully crossing
Small gullies, water crossing
Large and medium water crossing
Steel pipe weld coefficient and specified pressure resistance
Weld coefficient
Steel pipe standard
Steel type or steel grade
GB/T 9711. 1
Table 3.2.4-2 Design coefficient
Regional grade of gas pipeline
Service strength
Weld coefficient
Oil pipeline
3.2.5 The allowable tensile stress and allowable compressive stress of steel used in structural engineering should not exceed 60% of its minimum service strength, the allowable shear stress should not exceed 45% of its minimum service strength, and the support stress (end pressure) should not exceed 90% of its minimum service strength. 3.3 Water area and gully crossing
3.3.1 The selected crossing location should be consistent with the overall direction of the line. For large and medium-sized crossing projects, the local direction of the line should be adjusted according to the selected crossing location by 180
.
SY/T 0015.1—1998
3.3.2 The scheme and location of large and medium-sized crossing projects shall be determined through technical and economic demonstration based on hydrological, geological, topographical, soil and water conservation, environmental, meteorological, traffic, construction and management conditions. 3.3.3 Crossing projects shall be classified into engineering grades according to Table 3.3.3-1 and Table 3.3.3-2. Table 3, 3.3-1 Crossing water area engineering grade
Engineering grade
Multi-year average water level and water surface width
≥200
≥100~~<200
≥100～200
≥40～<100
Hydrological characteristics of crossing water area
Note: ①When the maximum flow rate during construction is greater than 2 m/s, the grade of medium and small projects can be increased by one level. ②For projects with special requirements, the engineering grade can be increased. Table 3.3.3-2 Gully Crossing Project Grade Project Grade
Gully Depth (m)
Note: For gully slopes less than the listed slope angles, the grade of large and medium-sized projects is reduced by one level. Corresponding water depth
Inconsider water depth
Inconsider water depth
Inconsider water depth
Gully characteristics
Gully slope (°)
3.3.4 Large-scale crossing projects should be designed for a 100-year flood, medium-sized crossing projects should be designed for a 50-year flood, and small-scale crossing projects should be designed for a 20-year flood.
When designing crossing projects downstream of a reservoir, the impact of reservoir regulation should be considered. The crossing project within 300m upstream of a bridge should not be lower than the design flood frequency standard of the bridge. 3.3.5 When crossing a river or gully, attention should be paid to the natural evolution of scouring on both sides. If the crossing project changes the natural state, general scouring and peripheral scouring should be distinguished. For crossing projects located downstream of a reservoir, local scouring and clean water scouring data during flood discharge from the reservoir must be obtained. 3.3.6 The minimum distance between the crossing pipe section and the bridge shall meet the requirements of Table 3.3.6. If trenching is done by blasting, the safety distance shall be increased by calculation.
Table 3.3.6 Distance between the crossing pipe section and the bridge
Bridge grade
Spacing requirements
Medium and small bridges
The distance between the crossing pipe section and the port, dock, underwater structure or water diversion structure shall not be less than 200 m. 3.3.7
3.3.8 When the crossing pipe section is located in an area with a basic earthquake intensity of 7 degrees or above, an earthquake-resistant design shall be carried out. m
3.3.9 The buried depth of the crossing pipe section on a navigable river shall prevent damage by anchors or navigation equipment. All measures of the crossing project shall not affect the passage of the waterway and shall obtain the consent of the waterway authority. 3.3.10 If there is a backup line or double line in the crossing section, the distance between it and the backup line or double line should not be less than 40m in the riverbed and 30m in the river beach.
SY/T 0015.1--1998
3.3.11 If the pipeline passes through the embankment and the ground on both sides is lower than the river water level, a water stop ring or water blocking wall should be installed. 3.3.12 The crossing section shall not be laid in railway or highway tunnels (except for special tunnels). 3.4 Railway and highway crossing
3.4.1 Pipelines crossing railways shall comply with the "Several Provisions on the Relationship between Long-distance Crude Oil and Natural Gas Pipelines and Railways" [(87) Youjian No. 505, Tieji (1987) No. 780].
3.4.2 Pipelines crossing roads shall comply with the "Several Provisions on Dealing with the Relationship between Oil Pipelines and Natural Gas Pipelines and Highways" (Trial) [(78) Jiaogonglu Zi No. 698, (78) Youhua Pipeline Zi No. 452]. 3.4.3 Pipelines crossing railways and roads shall avoid rocky areas, high-fill areas, road cuttings, and steep slopes with the same slope on both sides of the road. 3.4.4 Pipelines are strictly prohibited from crossing railway yards, guarded crossings, substations, tunnels, and equipment. 3.4.5 It is strictly prohibited to set elbows and produce horizontal or vertical curves on the pipe sections crossing railways and roads. 3.5 Survey requirements
3.5.1 Large-scale crossing projects should be surveyed in two stages: preliminary survey and detailed survey. For large-scale crossing projects with clear plans, a detailed survey can be adopted on the basis of investigation and research.
3.5.2 There should be no less than two positioning piles on each bank to mark the crossing position, and they should be set in a stable and reliable place that is not flooded or washed away. 3.5.3 Physical exploration methods can be used for preliminary engineering geological survey, and drilling exploration methods should be used for detailed survey to obtain complete and accurate first-hand information. 3.5.4 Layout of exploration drilling points. If trenching and burying are used for crossing, they should be arranged on the center line of the crossing pipe section; if directional drilling, jacking pipe or tunnel laying are used for crossing, they should be arranged crosswise on both sides of the center line of the crossing pipe section, 50m away from the center line. 3.5.5 The drilling depth should be 3~5m below the stable layer of the riverbed. If bedrock is encountered, drill 3~5m. 3.5.6 For large-scale crossing projects located in areas with a basic earthquake intensity of 7 degrees or above, the following four conditions should be clarified and quantitative indicators should be obtained:
Whether there are faults and the activity of faults;
2Whether cracks or displacements occur on both banks or in the beach during an earthquake; 3
Whether sand liquefaction will occur during an earthquake;
Whether an earthquake will cause landslides or deep sliding on both banks. 4
Measurement requirements should be implemented in accordance with the provisions of the current national standard "Measurement Specifications for Long-distance Oil and Gas Pipelines" SY0055. 3.5.7
3.5.8Survey requirements should be implemented in accordance with the provisions of the current national standard "Survey Specifications for Geotechnical Engineering of Oil and Gas Pipelines" SY/T0053. 3.6Others
3.6.1The anti-corrosion and insulation design of the crossing pipe section should be carried out in accordance with the provisions of the current national standard "Design Specifications for Anti-corrosion Engineering of Steel Pipelines and Storage Tanks" SYJ7.
3.6.2 For large-scale crossing projects, cut-off valves should be installed at both ends of the crossing. A reserved head should be reserved in the cut-off valve chamber. If it is a double-line crossing, a reserved head may not be provided. The crossing cut-off valve can be combined with the line cut-off valve. 3,6.3 The cut-off valve chamber should be set in a place that is not submerged by the design flood, and attention should be paid to ventilation. 3.6.4 When crossing a navigable river, signs should be set in accordance with the provisions of the current national standard "Inland River Traffic Safety Signs" GB13851. Line piles can be used as crossing signs for non-navigable rivers. 3.6.5 When crossing railways and highways, signs should be set in accordance with the requirements of the railway and highway departments. 3.6.6 The wall thickness of the steel pipe of the crossing pipe section should be calculated according to the allowable stress specified in Article 3.2.4 of this Code, and the diameter-to-thickness ratio should not be greater than 100.
4 Water and gully crossing design
4.1 Crossing location selection
4.1.1 The water and gully crossing location should be selected according to hydrological, topographical and geological conditions. 1
Should be selected in the section where the river channel or gully is straight and the water flow is gentle; 182
2Should be selected in the section where the cross section is basically symmetrical and there are sufficient construction sites on both sides;Should be selected in the section where the rock and soil composition is relatively simple and the slope is stable. 3
SY/T 0015. 1—1998
4.1.2The crossing position in the reservoir area should avoid the reservoir area and the tailwater area. If crossing downstream of the reservoir, it should be selected outside the concentrated scouring influence area downstream of the dam.
4.1.3The crossing pipe section should be perpendicular to the axial direction of the water flow; if it is to be oblique, the intersection angle should not be less than 60°. 4.1.4The crossing position should not be selected on the seismically active fault. 4.1.5The crossing position should not be selected in the section where the river channel is frequently dredged and deepened, the bank erosion is serious, or the changes of erosion and siltation of the beach are strong. 4.2 Laying and requirements
4.2.1 According to the hydrological and geological conditions, the crossing pipe section can be laid by trenching, directional drilling, pipe jacking, and tunneling. In areas with conditions, it can also be laid in an exposed manner
4.2.2 When the pipeline is buried to cross a river or lake, it should be laid in the stable layer of the riverbed or lakebed. When exposed laying is adopted, measures should be taken to stabilize the pipe to prevent vibration damage. 4.2.3 Elbows and fixed piers should not be set in the flooded parts of the crossing pipe section at the normal water level; for large and medium-sized crossing pipe sections, elbows and fixed piers should be set 50m away from the water edge of the normal water level; when it is necessary to set elbows or fixed piers within the normal water level range, in addition to strength verification, attention should also be paid to the vibration effect of the moving water of the pipe section.
4.2.4 When trenching is used to bury the crossing pipe section, the excavation depth should be determined according to the engineering grade and scouring conditions in accordance with the provisions of Table 4.2.4. Table 4.2.4 Depth of buried pipe top in crossing waters
In waters with scouring or dredging, it should be below the designed flood scouring or planned dredging line
In waters without scouring or dredging, it should be below the bottom of the water bed When the riverbed is bedrock Depth of embedded in bedrock (not scour during the designed flood)
Note that anchors and dredging equipment must not
damage the anti-corrosion layer
Cover the top with concrete to prevent
4.2.5 The bottom width and slope of the underwater trench should be determined according to the soil properties, water flow velocity, siltation and construction conditions; if there is a lack of hydrological and geological data and underwater equipment is used for excavation, it can be determined according to the provisions of Table 4.2.5; if a dredger is used, it should be determined according to the type of dredger, bucket capacity, positioning method, etc.
Table 4.2.5 Dimensions of underwater trenches
Soil types
Silt, silt sand, fine sand
Sub-sand soil, medium sand, coarse sand
Sand soil, gravel soil
Sub-clay
Minimum width of trench bottom
Note: ①The width of the trench bottom refers to the net width required for laying a single pipe, excluding siltation. The trench depth is less than 2.5m
②In deep water areas, the width of the trench bottom should also include the distance for divers to dive. ③In case of quicksand, the trench bottom width and slope should be determined separately according to the construction method. ①D is the outer diameter of the pipe body structure.
Slope of trench
Ditch depth shall not be less than 2.5m
SY/T 0015. 1---1998
4.2.6 For trench laying of underwater crossing pipe sections, if natural silting is adopted or the scouring range and scouring depth cannot be determined by survey data, the design and calculation shall be carried out in accordance with the provisions of Article 4.3.2 of this Code. 4.2.7 The excavation depth of rock trench shall exceed the value listed in Table 4.2.4 of this Code by 20cm; before the pipe section is placed in the trench, a 20cm thick sandy soil or fine soil cushion shall be filled.
4.2.8 For exposed laying, stabilizing measures such as gabions, weighted blocks, composite wall pipe grouting or piling can be adopted. 4.2.9 The materials used for stabilizing measures for crossing salt marshes shall have strong resistance to salt and alkali corrosion. 4.2.10 Directional drilling should be used for laying of clay, sub-clay and sandy riverbeds; it should not be used for laying of rock, quicksand and gravel riverbeds. For directional drilling crossing projects, there should be a drilling rig, mud pool and water reservoir site on one bank, and a pipeline assembly site on the other bank. 4.2.11 When directional drilling is used for laying, the entry angle and exit angle should be selected according to the performance of the drilling rig. In addition to meeting the requirements of Table 4.2.4 of this specification, the burial depth should not be less than 6m. The minimum radius of curvature for laying the crossing pipe section should be greater than 1500DN. 4.2.12 Jacking pipes should be used in soil layers such as gravel, sand, sandy soil, clay, marl and limestone, and should not be used in quicksand, silt, swamp and rock layers. 4.2.13 The inner diameter of the jacking pipe should not be less than 800mm. The working pit should have sufficient construction operation space and attention should be paid to drainage. 4.2.14 When crossing a tunnel, it is advisable to lay multiple pipes, and attention should be paid to the stability and deformation compensation of the pipe sections. Drainage blocking measures should be taken in the tunnel. 4.2.15 Tunnel design should be carried out in accordance with the provisions of the current national standards "Railway Tunnel Design Code" TBJ3 or "Highway Tunnel Design Code" JTJ026.
4.2.16 When crossing a swamp area, the crossing pipe section should be laid using the support method, soil replacement method, sand pile reinforcement method, stone filling method, preloading method or embankment method according to different swamp types.
4.3 Stability of underwater pipe sections
4.3.1 After the underwater crossing pipe section is laid, it shall not float or shift. If floating or shifting is likely to occur, pipe stabilization measures must be adopted. 4.3.2 The anti-floating and anti-shifting calculations of the exposed pipe section shall be carried out according to the following formulas. W≥K(F+Fay)
W≥F+F +Fa
Fay = C,ywD u2 /(2 g)
Fdx = CxwDu2/(2 g)
(4.3.2-1)
(4.3.2-2)
(4.3.2-3)
(4.3.2-4)
Wherein: W is the total weight of the pipe section per unit length (including the deadweight of the pipe body structure, the weight of the protective layer, the weight of the weighting layer, excluding the weight of the medium in the pipe) (N/m);
F is the static water buoyancy of the pipe section per unit length (N/m); Fay is the dynamic water lifting force of the pipe section per unit length (N/m); C,- is the buoyancy coefficient, which is taken as 0.6;|| tt||Fx. Dynamic water thrust per unit length of pipe section (N/m); C thrust coefficient, take 1.2;
D-outer diameter of pipe body structure (m);
w-weight of water in the water area (N/m\); u-designed water flow velocity at the pipe section (m/s); K-stable safety factor, take 1.3 for large and medium-sized projects, and 1.2 for small projects; f sliding friction coefficient between pipe section and riverbed, determined by test or experience; g-gravity acceleration, take 9.8m/s.
If it is laid with exposed elasticity, elastic resistance should also be calculated. 4.3.3 When the crossing pipe section is buried in trenches according to Articles 4.2.4 and 4.2.7 of this Code, the anti-floating calculation shall be carried out according to formula (4.3.3), W ≥ KFs
Where: K——stability safety factor, 1.2 for large and medium-sized projects, and 1.1 for small projects. (4.3.3)
4.3.4 When the crossing pipe section is laid by directional drilling or jacking, and the burial depth exceeds the provisions of Article 4.2.4 of this Code, and is 3m below the design scour line, no anti-floating calculation is required.
4.3.5 When the crossing pipe section is laid in a tunnel, it is not necessary to calculate the underwater stability problem. 4.4 Loads and combinations
4.4.1 The crossing pipe section shall be designed according to the following load combinations. 1Permanent load (constant load) includes:
1) internal pressure of the conveying medium;
2) white weight of the pipe section (including the deadweight of the pipe structure, the weight of the protective layer and the weight of the weighting layer); 3) weight of the conveying medium:
4) lateral and vertical earth pressure;
5) hydrostatic pressure and water buoyancy;
6) dynamic water pressure (when laying bare pipe);
7) temperature stress.
2Variable load (live load) includes:
1) water weight and pressure during trial operation;
2) pipe cleaning load;
3) construction pipe dragging or hanging load.
SY/T 0015. 11998
3Occasional action: located in areas with a basic earthquake intensity of 7 degrees or above, the actions of active fault displacement, sand liquefaction, earthquake earth pressure, etc. caused by earthquakes.
4.4.2 When calculating the structure of the crossing pipe section, the load combination should be carried out according to the laying form, the environment and the operating conditions. 1 Main combination: permanent load.
2 Additional combination: the sum of permanent load and variable load (combined according to the actual possible load). 3 Special combination: the sum of the main combination and the accidental load. 4.4.3 The allowable stress of the steel pipe load combination of the crossing pipe section shall be the value calculated according to Article 3.2.5 of this Code multiplied by the allowable stress increase factor in Table 4.4.3.
Table 4. 4.3 Allowable stress increase factor
Load combination
Main combination
Additional combination
Special combination
4.5 Structural design
Allowable stress increase factor
4.5.1 The strength, rigidity and stability of the crossing pipe section shall be calculated based on the selected wall thickness; if the requirements are not met, the wall thickness of the steel pipe shall be increased. 4.5.22
The axial stress, hoop stress and bending stress shall be considered in calculating the strength of the crossing pipe section, and each individual stress shall be less than the allowable stress of the steel pipe.
The hoop stress caused by the internal pressure is calculated according to formula (4.5.2-1), pd
The hoop stress of the steel pipe in the pipe section (MPa);
p~~The design internal pressure of the conveying medium (MPa); d--Inner diameter of the steel pipe (mm);
----The wall thickness of the steel pipe (mm).
2The axial stress of the pipe section is calculated according to the following formulas. (4.5.2-1)
SY/T 0015.1—1998
1) When the axial deformation of the pipe section is constrained:
2) When the axial deformation of the pipe section is not constrained: Where: a.--
=Ega(t - t)+μgh
Axial stress of the steel pipe of the pipe section (MPa);
Elastic modulus of steel. Take 2.0X10° (MPa); -Linear expansion coefficient of steel, take 1.2×10［m/（m·℃）]; Q--
Ambient temperature when the pipeline is installed and closed (℃); t
Temperature of the conveying medium in the pipeline (℃);.--Poisson's ratio of steel, take 0.3.
3 The bending stress caused by the elastic laying of the crossing pipe section is calculated according to formula (4.5.2-4): Op
Wherein: og--Axial bending stress of the steel pipe when the pipe section is bent (MPa): E.---Elastic modulus of steel, 2.0×105 (MPa); D---Outer diameter of the steel pipe (mm);
R---Elastic laying radius (mm).
(4. 5.2-2)
(4.5.2-3)
(4.5.2-4)
4 The hoop stress, axial stress and bending stress caused by other loads shall be calculated according to the actual possible situation. 4.5.3 The equivalent stress of the crossing pipe section is calculated according to formula (4.5.3). de Zah - Z0, ≤ 0. 90s
Where..…--equivalent stress of the steel pipe in the crossing section (MPa); Zo,--algebraic sum of hoop stresses generated by each load (MPa), algebraic sum of axial stresses generated by each load (MPa). Za.
4.5.4 When the wall thickness of the steel pipe in the crossing section meets the requirements of Article 3.6.6 of this Code, the local buckling caused by the radial deformation of the pipe may not be calculated.
4.5.5 When the temperature difference between the conveying medium temperature and the ambient temperature when the crossing section is laid and closed is large, its axial stability shall be verified according to the following formula.
N = [αE,(t2 - t)+(0. 5-μ)oJA Where: N---Axial force generated by temperature difference and internal pressure (MN); n
(4. 5.5-1)
(4.5.5-2)
Safety factor, for large-scale crossing projects, n=0.7; for medium-sized crossing projects, n=0.8; for small-scale crossing projects, n=0.9: Critical axial force when the pipeline begins to lose stability (calculated according to the provisions of Appendix H of GB50253-1994) (MN); Cross-sectional area of ​​the steel pipe (m).
The remaining symbols are the same as those specified in Article 4.5.2 of this Code. 4.5.6 For the crossing pipe section laid by directional drilling, its axial stability does not need to be verified. 4.6 Protection Project
4.6.1 The bank protection project in the crossing project shall meet the requirements of smooth water flow and no washing of the crossing pipe section. Other measures such as cut-off walls or cut-off ditches should be provided for the slopes crossing deep gullies.
4.6.2 The building materials used for bank protection and regulation structures should be selected locally according to local conditions. The backfill soil of the bank protection structure should be compacted or compacted in layers, but heavy clay, silt, silt, saline soil or organic soil should not be used for filling. 4.6.3 Under the mortar-laid or dry-laid rubble (concrete or reinforced concrete slab) slope protection, there should be a 10-20 cm thick well-graded gravel cushion layer, and a mortar-laid rubble (or concrete) foundation should be provided at the foot of the slope. If it is dry-laid rubble, the cushion layer should also be considered to act as a filter layer. 186
SY/T 0015.1—1998
4.6.4 When the mortar-laid rubble slope protection is long, expansion joints should be set every 10-20 m, and settlement joints should be set at the corresponding foundation. The seam width is 2~3cm and is filled with asphalt hemp or asphalt strips.
4.6.5 The mortar-laid slope protection should be designed with an appropriate number of drainage holes, and a filter layer should be set at the drainage holes. 4.6.6 The top of the revetment shall not be less than 0.5m above the design flood level (including wave height and water). The length of the revetment shall be determined according to the actual water flow conditions and slope geological conditions, and shall not be less than 5m. The buried depth of the revetment foundation shall meet the following requirements: 1 When the foundation is set in a non-scouring area, except for the rock foundation, the base shall not be less than 1m below the riverbed, and shall not be less than 0.3m below the freezing line
2 When the foundation is set in a scouring area, the base shall not be less than 1m below the scouring line; 3 When the foundation is set on a rock foundation, the strongly weathered layer should be removed and embedded in the rock to a certain depth according to the anti-scouring capacity of the bedrock. 4.6.7 The revetment project shall calculate the anti-sliding stability along the glass surface and along the class surface (or broken line surface). According to the importance of the project, the anti-sliding stability safety factor can be 1.15~1.30. When the angle between the slope protection and the horizontal line at the foot of the slope is less than or equal to the repose angle of the embankment soil, the anti-sliding stability of the slope protection may not be calculated. 4.6.8 The size of the bank protection masonry shall be calculated and determined according to the design flood velocity and the requirements of the "Highway Bridge Site Survey and Design Code" TJ062. 5 Railway and highway crossing design
5.1 General requirements
5.1.1 When the pipeline crosses the railway or the high-grade highway above Class II, it is recommended to use the top pipe or the horizontal hole drilling machine to lay the pipe. When crossing the highway below the mountain level or the general road, the trenching can be used for burial. 5.1.2 When the pipeline crosses the 1, Ⅱ, Ⅱ railway or the high-grade highway above Class II, a protective casing shall be installed. When crossing railway dedicated lines or highways below Grade III, protective casings can be used or the pipe wall thickness can be increased according to the specific situation. The protective casing can be steel pipes or reinforced concrete pipes. 5.1.3 The inner diameter of the protective casing should be 100 to 300 mm larger than the outer diameter of the conveying pipe. Insulating supports should be provided between the casing and the conveying pipe to maintain good insulation performance. The two ends of the casing are sealed with durable insulating materials, and the end of the casing shall not be less than 2 m beyond the slope foot of the roadbed. 5.1.4 When using protective casings to cross railways and highways, the conveying casing should be protected by strip-shaped anodes. 5.2 Loads and combinations
5.2.1 In addition to complying with the provisions of Article 4.4.1 of this Code, the loads to be considered for the conveying pipe section or casing crossing the railway or highway should include vehicle loads in variable loads and the influence of foundation settlement in accidental actions. 5.2.2 When calculating the structure of the pipe section crossing the railway or highway, load combinations should be made according to the actual possible situations. Main combination: the sum of permanent loads and vehicle loads. 2 Additional combination: the sum of the main combination and a certain variable load. 3 Special combination: the sum of the main combination and the accidental load. 5.2.3 The allowable stress of the railway and highway crossing pipe section shall comply with the provisions of Article 4.4.3 of this Code according to different load combinations. 5.3 Structural design
5.3.1 The strength, rigidity and stability of the crossing pipe section shall be calculated according to the selected wall thickness; if the requirements are not met, the wall thickness of the steel pipe shall be increased. 5.3.2 The strength verification of the crossing pipe section shall comply with the provisions of Articles 4.5.2 and 4.5.3 of this Code. 5.3.3 The radial deformation of the steel casing or the uncased crossing pipe section shall be verified under the condition of no internal pressure under the action of external force, and the deformation in the horizontal diameter direction shall not exceed 3% of the outer diameter of the pipe. The deformation is calculated in accordance with the provisions of Appendix G of the current national standard GB50253--1994. 5.3.4 For pipe sections crossing railways and highways, when the minimum buried depth of the pipe top is greater than 1m, the axial stability may not be verified. 6 Inspection requirements
6.1 Welding
6.1.1 The welding of the crossing pipe section shall be carried out in accordance with the provisions of the current national standard GB5D253 or GB50251. 6.1.2 The butt joint welds of the crossing pipe sections in large and medium-sized waters, railways, and roads above Class II shall be subjected to 100% radiographic inspection. The radiographic inspection shall be carried out in accordance with the provisions of the current national standard "Radiographic Transmission Process and Quality Classification of Steel Pipe Circumferential Fusion Weld Butt Joints" GB/T12605, and Class II is qualified. The inspection standards for the butt joint welds of the small water crossing pipe section or the road crossing pipe section below the spot level shall be the same as the requirements of the engineering section where the line is located.
6.2.1 The crossing pipe sections of large and medium-sized water areas, railways and highways above Class II must be subjected to independent strength pressure tests and tightness tests, and only after passing the tests can they be connected to the adjacent pipe sections. Crossings of small water areas or crossings of highways below Class III do not need to be pressure tested independently, but can be pressure tested together after being connected to the pipeline:
6.2.2 The pressure test medium, test pressure and pressure test time of the crossing pipe sections of oil and gas pipelines shall be implemented in accordance with the provisions of the current national standards CB50253 and GB50251 respectively. The strength test pressure of large and medium-sized crossing pipe sections shall be calculated according to formula (6.2.2), and the tightness test pressure shall adopt the design pressure.
In the formula, — strength test pressure (MPa); — steel pipe design wall thickness (mm);
a—steel pipe specified service limit (MPa); D---steel pipe outer diameterCalculation, the pressure drop rate during the strength test should not exceed 2%. When DN>300mm, the strict test A force ≤ (500/DN)% is considered qualified; when DN≤300mm, the allowable drop rate is 1.5%.
Wherein: Ap-
pressure drop rate (%);
(1)100%
p, = +s
pa= pu +pa
T. —Thermodynamic temperature of the gas in the tube at the beginning of pressure stabilization (K); T
Thermodynamic temperature of the gas in the tube at the end of pressure stabilization (K); p.-absolute pressure of the gas at the beginning of hidden pressure (MPa): p,-absolute pressure of the gas at the end of hidden pressure (MPa); palp---pressure gauge reading at the beginning and end of pressure stabilization (MPa); pzP-local atmospheric pressure at the beginning and end of pressure stabilization (MP). Note: P, T, T, and T all refer to the average values ​​of all measuring points along the entire line. 6.3 Anti-corrosion
6.3.1 The design documents must indicate the name, performance and index requirements of the anti-corrosion materials selected for the crossing pipe section. 6.3.2 The crossing pipe section should be inspected according to the selected anti-corrosion coating materials in accordance with the corresponding standards and specifications. 6.3.3 The same crossing pipe section should not be divided into sections with different anti-corrosion coatings and coating grades. 188
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