Method for calculating influence of uneven deformation of bottom soil body on underground flexible pipeline joint

Abstract

The invention discloses a method for calculating the influence of non-uniform deformation of a bottom soil body on an underground flexible pipeline joint, and the method comprises the steps: calculating the overburden soil pressure F of a flexible pipeline along the longitudinal unit length according to the diameter and burying depth of the flexible pipeline; determining a deformation difference value delta s of the soil body at the bottom of the flexible pipeline according to the spring stiffness of the soil bodies of the pipelines at the two ends; calculating the shearing force # imgabs0 # and the total corner # imgabs1 # of the pipeline joint when the pipeline joint is a torque release pipeline joint; calculating a pipeline joint shearing force # imgabs2 # and a joint bending moment # imgabs3 # when the pipeline joint is a torque transmission pipeline joint; and judging the service state of the current flexible pipeline according to the calculated value.

Description

Technical Field

[0001] The invention belongs to the technical field of pipeline engineering, and in particular relates to a method for calculating the influence of uneven deformation of bottom soil on underground flexible pipeline joints. Background Art

[0002] Under long-term underground service conditions, the soil at the bottom of the pipeline often deforms unevenly due to uneven construction compaction, rainwater infiltration, etc., which in turn causes the buried flexible pipeline to bend and deform. As the weakest link in the pipeline system, the pipeline joint is more likely to fail.

[0003] The interaction between buried flexible pipelines and soil involves nonlinear mechanical behavior, and the stress concentration phenomenon at pipeline joints is particularly complex. Most existing studies focus on the mechanical behavior characteristics of continuous pipelines, and there are few studies on the stress and deformation of pipeline joints, and related theoretical analysis methods are relatively scarce. Summary of the invention

[0004] Purpose of the invention: The technical problem to be solved by the present invention is to provide a method for calculating the influence of uneven deformation of the bottom soil on underground flexible pipe joints in view of the shortcomings of the prior art, so as to obtain and track the service status of underground pipe joints in real time.

[0005] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is as follows:

[0006] A method for calculating the influence of uneven deformation of the bottom soil on the joint of an underground flexible pipe comprises the following steps:

[0007] S1. Calculate the overburden pressure F of the flexible pipeline per unit length along the longitudinal direction according to the diameter and burial depth of the flexible pipeline;

[0008] S2. Determine the deformation difference Δ of the soil at the bottom of the flexible pipeline based on the soil spring stiffness of the pipeline at both ends. s ;

[0009] S3. Calculate the shear force of the pipe joint when the pipe joint is a moment release pipe joint. and total rotation angle ;

[0010] S4. Calculate the shear force of the pipe joint when the pipe joint is a moment transmission pipe joint. and joint bending moment ;

[0011] S5. According to the calculated value of step S3 or step S4, the current service status of the flexible pipeline is determined.

[0012] Specifically, in step S1, the overburden pressure F of the flexible pipe per unit length in the longitudinal direction is calculated by the following formula (1):

[0013] (1);

[0014] Where D is the diameter of the flexible pipe, in m; H is the buried depth of the flexible pipe, in m; γ is the soil density, in kN / m 3 ; is the soil arch coefficient.

[0015] Specifically, in step S2, the deformation difference Δ of the soil at the bottom of the pipeline s Calculated by the following formula (2):

[0016] (2);

[0017] In the formula, The spring stiffness of the soil on the pipe socket side, in kN / m 2 ; The spring stiffness of the soil on the side of the pipe socket, in kN / m 2 .

[0018] Specifically, the calculation process of step S3 is as follows:

[0019] S3-1. Calculate the shear force of the pipeline joint according to the deformation coordination conditions between the pipeline and the soil. ;

[0020] S3-2. Calculate the total rotation angle of the pipe joint based on the rotation angle θ1 of the pipe socket end and the rotation angle θ2 of the spigot end. .

[0021] Specifically, in step S3-1:

[0022] The vertical deflection y1 of the pipe socket end and the vertical deflection y2 of the spigot end caused by shear force are calculated by equations (3) and (4):

[0023] (3);

[0024] (4);

[0025] In the formula, is the shear force of the pipe joint, in kN; and They are the calculation parameters of the pipe socket end and the spigot end, in m -1 , calculated by equation (5) and equation (6) respectively:

[0026] (5);

[0027] (6);

[0028] Where EI is the longitudinal bending stiffness of the pipeline (kN•m 2 );

[0029] According to the deformation coordination condition between the pipeline and the soil, equation (7) can be obtained:

[0030] (7);

[0031] Right now,

[0032] (8);

[0033] Further,

[0034] (9).

[0035] Specifically, in step S3-2, the angle θ1 of the pipe socket end and the angle θ2 of the spigot end are calculated by the following formulas (10) and (11):

[0036] (10);

[0037] (11);

[0038] Total rotation angle of pipe joint Calculated by the following formula (12):

[0039] (12);

[0040] Substituting formulas (9), (10) and (11) into formula (12), we get:

[0041] (13).

[0042] Specifically, the calculation process of step S4 is as follows:

[0043] S4-1. Since there are both bending moment and shear force at the moment transmission pipeline joint, the shear force of the pipeline joint is calculated according to the deformation coordination conditions of the pipeline and the soil. ;

[0044] S4-2. Pipe socket end rotation angle θ generated by shear force V1 and the socket end angle θ V2 , the pipe socket end rotation angle θ caused by the bending moment M1 and the socket end angle θ M2 , calculate the bending moment of pipe joints .

[0045] Specifically, in step S4-1, since there are both bending moment and shear force at the moment transmission pipe joint, the vertical deflection deformation y of the pipe socket end caused by the shear force is V1 and the vertical deflection deformation y of the socket end V2 , respectively:

[0046]

[0047]

[0048] in, is the shear force of the pipe joint, in kN; and They are the calculation parameters of the pipe socket end and the spigot end, in m -1 , calculated by equation (5) and equation (6) respectively:

[0049] (5);

[0050] (6);

[0051] Where EI is the longitudinal bending stiffness of the pipeline (kN•m 2 );

[0052] The vertical deflection of the pipe socket caused by the bending moment M1 and the vertical deflection deformation y of the socket end M2 , respectively calculated by the following formula (14) and formula (15):

[0053] (14);

[0054] (15);

[0055] According to the deformation coordination condition between the pipeline and the soil, equation (16) can be obtained:

[0056] (16);

[0057] For moment transmission pipe joints, the pipe socket end rotation angle θ caused by shear force V1 and the socket end angle θ V2 , respectively calculated by the following formulas;

[0058]

[0059]

[0060] The pipe socket end rotation angle θ caused by the bending moment M1 and the socket end angle θM2 , can be calculated by formula (17) and formula (18) respectively:

[0061] (17);

[0062] (18);

[0063] For torque transmission pipe joints, the total rotation angle θ of the pipe socket end J1 Equal to the total angle θ of the pipe spigot end J2 , we can get formula (19):

[0064] (19);

[0065] Further, we can get:

[0066] (20);

[0067] Substituting formula (20) into formula (16), we can obtain:

[0068] (twenty one).

[0069] Specifically, in step S4-2, by substituting formula (21) into formula (20), the pipe joint bending moment can be obtained: The calculation formula (22) is:

[0070] (twenty two).

[0071] Further, in step S5, for the torque release pipe joint, when the calculated total rotation angle of the pipe joint is Greater than the allowable value of the joint angle, or the shear force of the pipe joint If the calculated bending moment of the pipe joint is greater than the allowable value of the joint shear force, the current pipe joint has failed and needs to be repaired accordingly. Greater than the allowable value of the joint bending moment, or the shear force of the pipe joint If it is greater than the allowable value of the joint shear force, the current pipe joint has failed and needs to be repaired accordingly.

[0072] Beneficial effects:

[0073] The present invention provides a method for calculating the influence of the uneven deformation of the bottom soil on the underground flexible pipe joint, which takes into account the influence of the uneven deformation of the bottom soil on the pipe joint, and can more accurately predict the stress condition and deformation trend of the pipe joint, providing a scientific basis for the safe operation of the pipeline. Through precise calculation, the potential risks of the pipe joint can be warned in advance, and corresponding maintenance measures can be taken, thereby extending the service life of the pipeline and reducing the occurrence of sudden accidents. The method can help operation and maintenance personnel to carry out pipeline maintenance in a targeted manner, avoid blind maintenance, reduce unnecessary maintenance costs, and improve maintenance efficiency; it is suitable for various types of underground flexible pipe joints, has strong versatility and practicality, and can meet the needs of different engineering environments. Through this method, engineering management personnel can better grasp the operating status of underground pipelines, optimize pipeline maintenance strategies, and improve the overall engineering management level. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more clear.

[0075] Figure 1 This is a diagram of the buried status of underground flexible pipelines.

[0076] Figure 2 Schematic diagram of the pipeline being affected by uneven deformation of the bottom soil. DETAILED DESCRIPTION

[0077] The present invention can be better understood with reference to the following examples.

[0078] Combination Figure 1 and Figure 2 As shown, the diameter of the buried flexible pipeline of the present invention is D (m), the buried depth is H (m), and the soil weight is γ (kN / m 3 ).

[0079] The overburden pressure F on the longitudinal unit length of the pipeline can be calculated by the following formula:

[0080] (1);

[0081] In the formula, is the soil arch coefficient.

[0082] Deformation difference of soil at the bottom of the pipeline Δ s , can be calculated by the following formula:

[0083] (2);

[0084] In the formula, is the soil spring stiffness on the pipe socket side (kN / m 2 ); is the soil spring stiffness on the pipe spigot side (kN / m 2 ).

[0085] 1. When the pipe joint is a torque release pipe joint

[0086] (1) Calculation of shear force at pipe joints

[0087] The vertical deflection y1 of the pipe socket end and the vertical deflection y2 of the spigot end can be calculated by the following formula:

[0088] (3);

[0089] (4);

[0090] In the formula, is the shear force of the pipe joint (kN).

[0091] (5);

[0092] (6);

[0093] Where EI is the longitudinal bending stiffness of the pipeline (kN•m 2 ).

[0094] According to the deformation coordination condition between the pipeline and the soil, it can be obtained that:

[0095] (7);

[0096] Right now,

[0097] (8);

[0098] Further,

[0099] (9).

[0100] (2) Calculate the total rotation angle θ of the pipe joint j

[0101] The angle θ1 of the pipe socket end and the angle θ2 of the spigot end can be calculated by the following formula:

[0102] (10);

[0103] (11);

[0104] The total rotation angle of the pipe joint can be calculated by the following formula:

[0105] (12);

[0106] Substituting formulas (9), (10) and (11) into formula (12), we can obtain:

[0107] (13).

[0108] 2. When the pipe joint is a torque transmission pipe joint

[0109] (1) Calculation of shear force at pipe joints

[0110] Since there are both bending moment and shear force at the moment transmission pipe joint, the vertical deflection deformation y of the pipe socket end caused by the shear force is V1 and the vertical deflection deformation y of the socket end V2 , which can be calculated by formulas (3) and (4) respectively; and the vertical deflection deformation y of the pipe socket end caused by the bending moment M1 and the vertical deflection deformation y of the socket end M2 , can be calculated by the following formula:

[0111] (14);

[0112] (15);

[0113] According to the deformation coordination conditions between the pipeline and the soil, it can be obtained:

[0114] (16);

[0115] For moment transmission pipe joints, the pipe socket end rotation angle θ caused by shear force V1 and the socket end angle θ V2 , which can be calculated by formulas (10) and (11) respectively; and the pipe socket end rotation angle θ caused by the bending moment M1 and the socket end angle θ M2 , can be calculated by the following formula:

[0116] (17);

[0117] (18);

[0118] For torque transmission pipe joints, the total rotation angle θ of the pipe socket end J1 Equal to the total angle θ of the pipe spigot end J2 , we can get:

[0119] (19);

[0120] Further, we can get:

[0121] (20);

[0122] Substituting formula (20) into formula (16), we can obtain:

[0123] (twenty one).

[0124] (2) Calculation of pipe joint bending moment

[0125] Substituting formula (21) into formula (20), we can obtain:

[0126] (twenty two).

[0127] Example

[0128] The diameter D of the corrugated steel pipe is 0.94 m, the burial depth h is 6.1 m, and the longitudinal bending stiffness EI is 700 kN•m 2 , soil weight is 22 kN / m 3 , the soil arch coefficient is taken as 1.43, and the soil spring stiffness k1 and k2 are 23500 kN / m 2 and 47000 kN / m 2 .

[0129] 1. When the pipe joint is a torque release pipe joint

[0130] (1) Calculation of shear force at pipe joints

[0131] According to formula (1),

[0132] ;

[0133] According to formulas (5) and (6), we can get:

[0134] ;

[0135] ;

[0136] According to formula (9), we can get:

[0137] .

[0138] (2) Calculate the total rotation angle θ of the pipe joint j

[0139] According to formula (13), we can get:

[0140] .

[0141] 2. When the pipe joint is a torque transmission pipe joint

[0142] (1) Calculation of shear force at pipe joints

[0143] According to formula (21), we can get:

[0144] .

[0145] (2) Calculation of pipe joint bending moment

[0146] According to formula (22),

[0147] .

[0148] 3. Verification

[0149] According to the existing test method (Zhou Min. Research on Mechanical Response Characteristics of Buried HDPE Pipeline Induced by Uneven Foundation Settlement [D]. Southeast University, 2018.), Table 1 shows the comparison between the experimental measured values ​​and the calculated values ​​of the method of the present invention. It can be seen from the table that the error between the calculated values ​​of the method of the present invention and the experimental measured values ​​is less than 5%, indicating that this method is reliable and effective in calculating the influence of uneven deformation of the bottom soil on the joints of underground flexible pipes.

[0150] Table 1 Comparison of experimental values ​​and calculated values ​​by the method of the present invention

[0151]

[0152] The present invention provides a method and idea for calculating the influence of uneven deformation of the bottom soil on the underground flexible pipe joint. There are many methods and ways to implement the technical solution. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention. All components not specified in this embodiment can be implemented by existing technologies.

Claims

1. A method for calculating the influence of uneven deformation of the bottom soil on underground flexible pipe joints, characterized in that: The steps include: S1. Calculate the overburden pressure F of the flexible pipeline per unit length along the longitudinal direction according to the diameter and burial depth of the flexible pipeline; S2. Determine the deformation difference Δ of the soil at the bottom of the flexible pipeline based on the soil spring stiffness of the pipeline at both ends. s ; S3. Calculate the shear force of the pipe joint when the pipe joint is a moment release pipe joint. and total rotation angle ; S4. Calculate the shear force of the pipe joint when the pipe joint is a moment transmission pipe joint. and joint bending moment ; S5. According to the calculated value of step S3 or step S4, the current service status of the flexible pipeline is determined.

2. The method for calculating the influence of uneven deformation of the bottom soil on underground flexible pipe joints according to claim 1 is characterized in that: In step S1, the overburden pressure F of the flexible pipe per unit length in the longitudinal direction is calculated by the following formula (1): （1）； Where D is the diameter of the flexible pipe, in m; H is the buried depth of the flexible pipe, in m; γ is the soil density, in kN / m 3 ; is the soil arch coefficient.

3. The method for calculating the influence of uneven deformation of the bottom soil on underground flexible pipe joints according to claim 2 is characterized in that: In step S2, the deformation difference Δ of the soil at the bottom of the pipeline s Calculated by the following formula (2): （2）； In the formula, The spring stiffness of the soil on the pipe socket side, in kN / m 2 ; The spring stiffness of the soil on the side of the pipe socket, in kN / m 2 .

4. The method for calculating the influence of uneven deformation of the bottom soil on underground flexible pipe joints according to claim 3 is characterized in that: The calculation process of step S3 is as follows: S3-1. Calculate the shear force of the pipeline joint according to the deformation coordination conditions between the pipeline and the soil. ; S3-2. Calculate the total rotation angle of the pipe joint based on the rotation angle θ1 of the pipe socket end and the rotation angle θ2 of the spigot end. .

5. The method for calculating the influence of uneven deformation of the bottom soil on underground flexible pipe joints according to claim 4 is characterized in that: In step S3-1: The vertical deflection y1 of the pipe socket end and the vertical deflection y2 of the spigot end caused by shear force are calculated by equations (3) and (4): （3）； （4）； In the formula, is the shear force of the pipe joint, in kN; and They are the calculation parameters of the pipe socket end and the spigot end, in m -1 , calculated by equation (5) and equation (6) respectively: （5）； （6）； Where EI is the longitudinal bending stiffness of the pipeline (kN•m 2 ); According to the deformation coordination condition between the pipeline and the soil, equation (7) can be obtained: （7）； Right now, （8）； Further, （9）。 6. The method for calculating the influence of uneven deformation of the bottom soil on underground flexible pipe joints according to claim 5 is characterized in that: In step S3-2, the angle θ1 of the pipe socket end and the angle θ2 of the pipe spigot end are calculated by the following equations (10) and (11): （10）； （11）； Total rotation angle of pipe joint Calculated by the following formula (12): （12）； Substituting formulas (9), (10) and (11) into formula (12), we get: （13）。 7. The method for calculating the influence of uneven deformation of the bottom soil on underground flexible pipe joints according to claim 3 is characterized in that: The calculation process of step S4 is as follows: S4-1. Since there are both bending moment and shear force at the moment transmission pipeline joint, the shear force of the pipeline joint is calculated according to the deformation coordination conditions of the pipeline and the soil. ; S4-2. Pipe socket end rotation angle θ generated by shear force V1 and the socket end angle θ V2 , the pipe socket end rotation angle θ caused by the bending moment M1 and the socket end angle θ M2 , calculate the bending moment of pipe joints .

8. The method for calculating the influence of uneven deformation of the bottom soil on underground flexible pipe joints according to claim 7 is characterized in that: In step S4-1, since there are both bending moment and shear force at the moment transmission pipe joint, the vertical deflection deformation y of the pipe socket end caused by the shear force is V1 and the vertical deflection deformation y of the socket end V2 , respectively: ； ； in, is the shear force of the pipe joint, in kN; and They are the calculation parameters of the pipe socket end and the spigot end, in m -1 , calculated by equation (5) and equation (6) respectively: （5）； （6）； Where EI is the longitudinal bending stiffness of the pipeline (kN•m 2 ); The vertical deflection of the pipe socket caused by the bending moment M1 and the vertical deflection deformation y of the socket end M2 , respectively calculated by the following formula (14) and formula (15): （14）； （15）； According to the deformation coordination condition between the pipeline and the soil, equation (16) can be obtained: （16）; For moment transmission pipe joints, the pipe socket end rotation angle θ caused by shear force V1 and the socket end angle θ V2 , respectively calculated by the following formulas; ； ； The pipe socket end rotation angle θ caused by the bending moment M1 and the socket end angle θ M2 , can be calculated by formula (17) and formula (18) respectively: （17）； （18）； For torque transmission pipe joints, the total rotation angle θ of the pipe socket end J1 Equal to the total angle θ of the pipe spigot end J2 , we can get formula (19): （19）； Further, we can get: （20）； Substituting formula (20) into formula (16), we can obtain: （21）。 9. The method for calculating the influence of uneven deformation of the bottom soil on underground flexible pipe joints according to claim 8, characterized in that: In step S4-2, substitute formula (21) into formula (20) to obtain the pipe joint bending moment: The calculation formula (22) is: （22）。 10. The method for calculating the influence of uneven deformation of bottom soil on underground flexible pipe joints according to claim 1, characterized in that: In step S5, for the moment release pipe joint, when the calculated total rotation angle of the pipe joint is Greater than the allowable value of the joint angle, or the shear force of the pipe joint If the calculated bending moment of the pipe joint is greater than the allowable value of the joint shear force, the current pipe joint has failed and needs to be repaired accordingly. Greater than the allowable value of the joint bending moment, or the shear force of the pipe joint If it is greater than the allowable value of the joint shear force, the current pipe joint has failed and needs to be repaired accordingly.

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