A method for calculating the influence of uneven deformation of the bottom soil on the underground flexible pipe joint

Abstract

The present invention discloses a method for calculating the influence of uneven deformation of the bottom soil on the underground flexible pipeline joint, including calculating the overburden pressure F per unit length along the longitudinal direction of the flexible pipeline according to the diameter and burial depth of the flexible pipeline; determining the deformation difference Δ of the soil at the bottom of the flexible pipeline according to the soil spring stiffness of the pipelines at both ends s ; calculating the shear force #imgabs0# and the total rotation angle #imgabs1# of the pipeline joint when the pipeline joint is a moment-release pipeline joint; calculating the shear force #imgabs2# and the joint bending moment #imgabs3# of the pipeline joint when the pipeline joint is a moment-transfer pipeline joint; and judging the service state of the current flexible pipeline according to the above calculated values.

Description

Technical Field

[0001] The present invention belongs to the technical field of pipeline engineering, and particularly relates to a method for calculating the influence of uneven deformation of the 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 undergoes uneven deformation due to reasons such as uneven construction compaction and rainwater infiltration, which in turn causes flexural deformation of the buried flexible pipeline. As the weakest link in the pipeline system, pipeline joints are more likely to fail.

[0003] The interaction between buried flexible pipelines and soil involves non-linear mechanical behavior, and the stress concentration phenomenon at the pipeline joint is particularly complex. Most existing studies focus on the discussion of the mechanical behavior characteristics of continuous pipelines, with less research on the stress and deformation of pipeline joints, and relatively few relevant theoretical analysis methods. Summary of the Invention

[0004] Object 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 pipeline joints in view of the deficiencies of the prior art, so as to obtain and track the service state of underground pipeline joints in real time.

[0005] In order to achieve the above 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 underground flexible pipeline joints, comprising the following steps:

[0007] S1. Calculate the overburden pressure F per unit length along the longitudinal direction of the flexible pipeline 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 according to the soil spring stiffness of the pipelines at both ends s ;

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

[0010] S4. Calculate the shear force and the joint bending moment of the pipeline joint when the pipeline joint is a moment-transfer pipeline joint;

[0011] S5. Judge the service state of the current flexible pipeline according to the calculated value of step S3 or step S4.

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

[0013] (1);

[0014] In the formula, D is the diameter of the flexible pipeline, in m; H is the burial depth of the flexible pipeline, in m; γ is the unit weight of soil, in kN / m 3 ; is the soil arch coefficient.

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

[0016] (2);

[0017] In the formula, is the soil spring stiffness on one side of the socket end of the pipeline, in kN / m 2 ; is the soil spring stiffness on one side of the spigot end of the pipeline, 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 condition between the pipeline and the soil ;

[0020] S3-2. Calculate the total rotation angle of the pipeline joint according to the rotation angles θ1 at the socket end and θ2 at the spigot end of the pipeline .

[0021] Specifically, in step S3-1:

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

[0023] (3);

[0024] (4);

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

[0026] (5);

[0027] (6);

[0028] Wherein, EI is the longitudinal flexural stiffness of the pipeline (kN•m 2 );

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

[0030] (7);

[0031] That is,

[0032] (8);

[0033] Furthermore, it can be obtained that

[0034] (9).

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

[0036] (10);

[0037] (11);

[0038] Total rotation angle of the pipeline joint Is 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 pipeline joint during moment transfer, according to the deformation coordination condition between the pipeline and the soil body, calculate the shear force at the pipeline joint ;

[0044] S4-2. According to the rotation angle θ V1 At the socket end of the pipeline and the rotation angle θ V2 At the spigot end, the rotation angle θ M1 At the socket end caused by the bending moment and the rotation angle θ M2 At the spigot end, calculate the bending moment Of the pipeline joint.

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

[0046]

[0047]

[0048] where is the shear force of the pipeline joint, with the unit of kN; and are the calculation parameters of the socket end and spigot end of the pipeline respectively, with the unit of m -1 and are calculated respectively through formulas (5) and (6):

[0049] (5);

[0050] (6);

[0051] In the formula, EI is the longitudinal flexural rigidity of the pipeline (kN•m 2 );

[0052] The vertical deflection y of the socket end of the pipeline caused by the bending moment M1 and the vertical deflection y of the spigot end M2 are calculated respectively through the following formulas (14) and (15):

[0053] (14);

[0054] (15);

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

[0056] (16);

[0057] For the torque transmission pipeline joint, the rotation angle θ of the socket end of the pipeline caused by the shear force V1 and the rotation angle θ of the spigot end V2 are calculated respectively through the following formulas;

[0058]

[0059]

[0060] And the rotation angle θ of the socket end of the pipeline caused by the bending moment M1 and the rotation angle θ of the spigot endM2 , it can be calculated by formula (17) and formula (18) respectively:

[0061] (17);

[0062] (18);

[0063] For the torque transmission pipe joint, the total rotation angle θ of the socket end of the pipe J1 is equal to the total rotation angle θ of the spigot end of the pipe J2 , and formula (19) can be obtained:

[0064] (19);

[0065] Furthermore, it can be obtained:

[0066] (20);

[0067] Substituting formula (20) into formula (16), it can be obtained:

[0068] (21).

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

[0070] (22).

[0071] Furthermore, 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 rotation angle, or the shear force of the pipe joint is greater than the allowable value of the joint shear force, then the current pipe joint has failed and corresponding repair treatment is required; for the torque transmission pipe joint, when the calculated bending moment of the pipe joint is greater than the allowable value of the joint bending moment, or the shear force of the pipe joint is greater than the allowable value of the joint shear force, then the current pipe joint has failed and corresponding repair treatment is required.

[0072] Beneficial effects:

[0073] A method for calculating the influence of uneven deformation of the bottom soil on the underground flexible pipeline joint provided by the present invention takes into account the influence of uneven deformation of the bottom soil on the pipeline joint, can more accurately predict the stress condition and deformation trend of the pipeline joint, and provides a scientific basis for the safe operation of the pipeline. Through precise calculation, potential risks of the pipeline 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. This method can help operation and maintenance personnel to carry out pipeline maintenance targeted, avoid blind overhaul, reduce unnecessary maintenance costs, and improve maintenance efficiency; it is applicable to various types of underground flexible pipeline joints, has strong generality and practicability, and can meet the needs of different engineering environments. Through this method, engineering managers can better master the operation status of underground pipelines, optimize pipeline maintenance strategies, and improve the overall engineering management level. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] The following further describes the present invention in detail with reference to the drawings and specific embodiments, and the above and / or other advantages of the present invention will become clearer.

[0075] Figure 1 It is a diagram of the buried state of the underground flexible pipeline.

[0076] Figure 2 It is a schematic diagram of the pipeline affected by uneven deformation of the bottom soil. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0077] The present invention can be better understood according to the following embodiments.

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

[0079] The overburden pressure F per unit length of the pipeline in the longitudinal direction can be calculated by the following formula,

[0080] (1);

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

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

[0083] (2);

[0084] In the formula, is the soil spring stiffness on one side of the socket end of the pipeline (kN / m 2 ). is the soil spring stiffness on one side of the socket end of the pipeline (kN / m 2 ).

[0085] I. When the pipeline joint is a moment-releasing pipeline joint

[0086] (1) Calculate the shear force of the pipeline joint

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

[0088] (3);

[0089] (4);

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

[0091] (5);

[0092] (6);

[0093] In the formula, EI is the longitudinal flexural 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] That is,

[0097] (8);

[0098] Furthermore, it can be obtained that

[0099] (9).

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

[0101] The rotation angle θ1 at the bell end of the pipeline and the rotation angle θ2 at the socket end can be calculated by the following formula:

[0102] (10);

[0103] (11);

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

[0105] (12);

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

[0107] (13).

[0108] II. When the pipe joint is a torque - transmitting pipe joint

[0109] (1) Calculate the shear force of the pipe joint

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

[0111] (14);

[0112] (15);

[0113] According to the deformation coordination condition between the pipe and the soil, we get:

[0114] (16);

[0115] For the torque - transmitting pipe joint, the rotation angle θ V1 at the socket end of the pipe and the rotation angle θ V2 at the spigot end of the pipe caused by the shear force can be calculated by formulas (10) and (11) respectively; while the rotation angle θ M1 at the socket end of the pipe and the rotation angle θ M2 at the spigot end of the pipe caused by the bending moment can be calculated by the following formula:

[0116] (17);

[0117] (18);

[0118] For the torque - transmitting pipe joint, the total rotation angle θ J1 at the socket end of the pipe is equal to the total rotation angle θ J2 at the spigot end of the pipe, we get:

[0119] (19);

[0120] Furthermore, we get:

[0121] (20);

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

[0123] (21).

[0124] (2) Calculate the bending moment of the pipeline joint

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

[0126] (22).

[0127] Embodiment

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

[0129] I. When the pipeline joint is a moment release pipeline joint

[0130] (1) Calculate the shear force of the pipeline joint

[0131] According to formula (1), we have

[0132] ;

[0133] According to formulas (5) and (6), we have

[0134] ;

[0135] ;

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

[0137] .

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

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

[0140] .

[0141] II. When the pipeline joint is a moment transfer pipeline joint

[0142] (1) Calculate the shear force of the pipeline joint

[0143] According to formula (21), it can be obtained that:

[0144] 。

[0145] (2) Calculate the bending moment of the pipeline joint

[0146] According to formula (22), it can be obtained that,

[0147] 。

[0148] III. Verification

[0149] According to the existing test method (Min Zhou. Research on the mechanical response characteristics of buried HDPE pipelines induced by non-uniform settlement of foundation [D]. Southeast University, 2018.), Table 1 shows the comparison between the measured test values and the calculated values by the method of the present invention. It can be seen from the table that the error between the calculated values by the method of the present invention and the measured test values is less than 5%, indicating that the method is reliable and effective when calculating the influence of non-uniform deformation of the bottom soil on the joints of underground flexible pipelines.

[0150] Table 1 Comparison between test values and calculated values by the method of the present invention

[0151]

[0152] The present invention provides an idea and method for calculating the influence of non-uniform deformation of the bottom soil on the joints of underground flexible pipelines. There are many methods and ways to specifically implement this technical solution. The above description is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention. Each component not clearly defined in this embodiment can be implemented by the existing technology.

Claims

1. A method for calculating the influence of uneven deformation of the bottom soil on the joints of underground flexible pipelines, characterized in that, Including the following steps: S1. Calculate the overburden pressure per unit length along the longitudinal direction of the flexible pipeline according to the diameter and burial depth of the flexible pipeline F ; S2. Determine the deformation difference of the soil at the bottom of the flexible pipe according to the soil spring stiffness of the two end pipes Δ s ; S3. Calculate the shear force of the pipe joint and the total rotation angle when the pipe joint is a moment-release pipe joint. and the total rotation angle ; S4. Calculate the shear force of the pipe joint and the joint bending moment when the pipe joint is a torque transmission pipe joint. and the joint bending moment ; S5. According to the calculated value in step S3 or step S4, judge the service state of the current flexible pipeline; In step S1, the overburden pressure on the flexible pipeline per unit longitudinal length F is calculated by the following formula (1): （1）； In the formula, D is the diameter of the flexible pipe, with the unit of m; H is is the burial depth of the flexible pipe, with the unit of m; γ is is the unit weight of soil, with the unit of kN / m 3 ; is the soil arch coefficient; In step S2, the deformation difference of the soil at the bottom of the pipeline Δ s is calculated by the following formula (2): （2）； In the formula, is the soil spring stiffness on one side of the socket end of the pipeline, with the unit of kN / m 2 ; is the soil spring stiffness on one side of the spigot end of the pipeline, with the unit of kN / m 2 .

2. The method for calculating the influence of uneven deformation of the bottom soil mass on the underground flexible pipe joint according to claim 1, wherein, The calculation process of step S3 is as follows: S3-1. Calculate the shear force of the pipeline joint according to the deformation coordination condition between the pipeline and the soil mass ; S3-2. According to the rotation angle of the socket end of the pipeline θ 1 and the rotation angle of the spigot end θ 2, calculate the total rotation angle of the pipeline joint .

3. The method for calculating the influence of uneven deformation of the bottom soil mass on the underground flexible pipe joint according to claim 2, characterized in that In step S3-1: Vertical deflection deformation at the socket end of the pipe caused by shear force y 1 and the vertical deflection deformation at the spigot end y 2 , calculated by Equations (3) and (4): （3）； （4）； In the formula, is the shear force of the pipe joint, with the unit of kN; and are the calculation parameters of the socket end and spigot end of the pipe respectively, with the unit of m -1 , which are calculated respectively through Formula (5) and Formula (6): （5）； （6）； In the formula, EI is the longitudinal flexural stiffness of the pipeline, with the unit of kN•m 2 ; According to the deformation coordination condition between the pipeline and the soil, formula (7) can be obtained: （7）； That is, （8）； Furthermore, it can be obtained that （9）。 4. The method for calculating the influence of uneven deformation of the bottom soil on the underground flexible pipe joint according to claim 3, characterized in that, In step S3-2, the corner angle θ 1 of the socket end of the pipe and the corner angle θ 2 of the spigot end are calculated by the following formulas (10) and (11): （10）； （11）； Total rotation angle of the pipe joint Calculated by the following formula (12): （12）； Substitute formulas (9), (10) and (11) into formula (12), and then we get: （13）。 5. The method for calculating the influence of uneven deformation of the bottom soil mass on the underground flexible pipe joint according to claim 1, 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 joint of the torque transmission pipeline, the shear force of the pipeline joint is calculated according to the deformation coordination condition between the pipeline and the soil body. ; S4-2. Calculate the pipe joint moment based on the socket end rotation θ V1 and spigot end rotation θ V2 caused by shear force, and the socket end rotation θ M1 and spigot end rotation θ M2 caused by bending moment θ V1 and spigot end rotation θ V2 , the socket end rotation θ M1 and spigot end rotation θ M2 , and calculate the pipe joint moment .

6. The method for calculating the influence of uneven deformation of the bottom soil on the underground flexible pipe joint according to claim 5, characterized in that, In step S4-1, since there are both bending moment and shear force at the joint of the torque transmission pipeline, the vertical deflection deformation of the socket end of the pipeline caused by the shear force y V1 and the vertical deflection deformation of the spigot end y V2 are respectively as follows: ； ； Among them, is the shear force of the pipe joint, with the unit of kN; and are the calculation parameters of the socket end and spigot end of the pipe respectively, with the unit of m -1 , and are calculated respectively through Equations (5) and (6): （5）； （6）； In the formula, EI is the longitudinal bending stiffness of the pipeline, kN•m 2 ; The vertical flexural deformation of the socket end of the pipe caused by the bending moment y M1 and the vertical flexural deformation of the spigot end y M2 are calculated respectively by the following formulas (14) and (15): （14）； （15）； According to the deformation coordination condition between the pipeline and the soil, formula (16) can be obtained: （16）； For a torque transmission pipe joint, the socket end rotation angle of the pipe caused by shear force θ V1 and the spigot end rotation angle θ V2 are calculated respectively by the following formulas; ； ； The pipe socket end rotation caused by the bending moment θ M1 and the spigot end rotation θ M2 can be calculated by formulas (17) and (18) respectively: （17）； （18）； For the torque transmission pipe joint, the total rotation angle of the socket end of the pipe θ J1 is equal to the total rotation angle of the spigot end of the pipe θ J2 , and the formula (19) can be obtained as follows: （19）； Furthermore, it can be obtained that: （20）； Substitute formula (20) into formula (16), and we can get: （21）。 7. The method for calculating the influence of uneven deformation of the bottom soil mass on the underground flexible pipe joint according to claim 6, characterized in that, In step S4-2, substituting formula (21) into formula (20), the calculation formula (22) of the pipe joint moment can be obtained: : （22）。 8. The method for calculating the influence of uneven deformation of the bottom soil on the underground flexible pipe joint according to claim 1, characterized in that, In step S5, for the torque release pipe joint, when the total rotation angle of the pipe joint calculated is greater than the allowable rotation angle of the joint, or the shear force of the pipe joint is greater than the allowable shear force of the joint, then the current pipe joint has failed and corresponding repair treatment is required; for the torque transfer pipe joint, when the bending moment of the pipe joint calculated is greater than the allowable bending moment of the joint, or the shear force of the pipe joint is greater than the allowable shear force of the joint, then the current pipe joint has failed and corresponding repair treatment is required.

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