CN103632038A - Automatic batch checking calculation method for safety of submarine pipeline suspended span sections - Google Patents

Abstract

The invention discloses an automatic batch checking calculation method for safety of submarine pipeline suspended span sections. The automatic batch checking calculation method includes the following steps of (1) data preparation which includes the steps of preparing submarine pipeline design parameter data comprising material constants, pipe wall thicknesses and the like and obtaining submarine pipeline routing mud surface elevation data comprising a submarine pipeline routing key mileage point KP, the relative distance h between the mud surface and the lower edge of a submarine pipeline and the absolute depth of the mud surface, (2) suspended span identification which includes the steps of judging starting points and terminal points of suspended spans according to h and obtaining mud surface elevation data of all the suspended spans, (3) model calculation which includes the steps of performing the following one or more calculations so as to obtain strength, rigidity and/or wet modal frequency and/or the fatigue life of the suspended span sections, (4) submarine pipeline suspended span section safety evaluation which is performed according to the obtained strength, rigidity and/or wet modal frequency and/or the fatigue life of the suspended span sections. According to the automatic batch checking calculation method, the efficiency and the precision of suspended span safety checking and treatment plan making can be improved.

Description

A kind of submarine pipeline suspended span section security automatic batch is checked computing method

Technical field

The invention belongs to ocean engineering structure risk management field, relate in particular to the security check method of a kind of submarine pipeline (being called for short sea pipe) suspended span section.

Background technology

Suspended span is the main hidden danger of sea pipe safe operation, the method that the security of existing sea pipe suspended span section is checked is the model based on conditions such as the given depth of water, boundary constraints, calculate the Fatigue Life Curve of different length suspended span, according to obtaining safe critical suspended span length designed life.

On the one hand, the environmental baseline parameter of actual every section of suspended span is different, adopts the model prediction result of same setting not have universality, needs to adopt actual parameter to every section of independent modeling of suspended span under some condition; On the other hand, China's many Offshore petroleum Near Pipelines landform is rugged, bed ripples enrichment, wash away serious, suspended span phenomenon occurs frequent, there is nearly 4000 places suspended span in the sea pipe that certain marine site is 130 kilometers, if adopt common finite element software to every section of independent Modeling Calculation of suspended span, require a great deal of time and brought great difficulty with evaluation and the control of manpower ，Zhe Dui production management department.

Summary of the invention

The problem existing for prior art, the object of this invention is to provide a kind of submarine pipeline suspended span section security automatic batch and checks computing method, can improve efficiency and the accuracy of suspended span security check and resolution formulation work.

Method of the present invention comprises the steps:

1) data are prepared: prepare sea pipe design parameter data, comprise material constant, thickness of pipe etc.; Obtain extra large pipeline by mud face altitude figures, comprising: extra large pipeline is by critical importance point KP(Key Point), relative distance h, the mud face absolute depth on mud face and the lower edge of sea pipe;

2) suspended span identification: according to h judgement suspended span start, end, obtain the mud face altitude figures of all suspended spans;

3) model calculates: carry out following one or more computing, with obtain suspended span section intensity,

Rigidity and/or wet model frequency and/or fatigue lifetime:

A, single span computation model:

Its mathematical expression is as follows:

${\mathrm{\ρ}}_e\frac{{\∂}^{2}w}{{\∂t}^2}+\frac{{\∂}^2}{{\∂x}^2}\left(\mathrm{EI}\frac{{\∂}^{2}w}{{\∂x}^2}\right)=q(x,t);$

ρ wherein _efor the equivalent density of extra large pipe, w is vertical deviation, the equivalent elastic modulus that E is extra large pipe, and the moment of inertia of cross-section that I is extra large pipe, q is external applied load;

B, multispan computation model:

Its mathematical expression is as follows:

$i.\left\{\begin{array}{c}w\left(0\right)=w\left(L\right)=0\\ {\frac{\∂w\left(x\right)}{\∂x}|}_{x=0}={\frac{\∂w\left(x\right)}{\∂x}|}_{x=L}=0\end{array}\right.$

$\mathrm{ii}.\left\{\begin{array}{c}w\left(L_{{\mathrm{sh}}_{2k-1}}\right)=w\left(L_{{\mathrm{sh}}_{2k}}\right)=0\\ {\frac{{\∂}^{2}w\left(x\right)}{{\∂x}^2}|}_{x=L_{{\mathrm{sh}}_{2k-1}}}={\frac{{\∂}^{2}w\left(x\right)}{{\∂x}^2}|}_{x=L_{{\mathrm{sh}}_{2k}}}=0\end{array};k=\mathrm{1,2},...n\right.$

Wherein, the total length that L is whole multispan, x is the position along tubular axis line, L _sh2k-1and L _sh2krepresent k section across the left end of shoulder and right-hand member respectively apart from the distance of multispan starting point, k is that k section in multispan is across shoulder;

4) according to suspended span section intensity, rigidity and/or the wet model frequency and/or the fatigue lifetime that obtain the security of submarine pipeline suspended span section being evaluated.

Advantage of the present invention: by above-mentioned flow process and method, the present invention has greatly reduced the loaded down with trivial details step to the manual modeling analysis of each suspended span section, can improve order of accuarcy and the counting yield of sea pipe running status prediction, can avoid utilizing single calculating results to pass judgment on the error of sea pipe security.

Accompanying drawing explanation

Fig. 1 is that the hydrodynamic force coefficient while changing with bottom distance is managed in different depth scour pit Shanghai;

Fig. 2 is the decision rule of multispan of being coupled on different soil property bottoms.

Embodiment

Method of the present invention comprises the steps.

1) data are prepared: prepare sea pipe design parameter data, comprise material constant, thickness of pipe etc.; Obtain extra large pipeline by mud face altitude figures, comprising: extra large pipeline is put Kp, mud face and the extra large relative distance h that manages lower edge, mud face absolute depth by critical importance;

2) suspended span identification: according to h judgement suspended span start, end, obtain the mud face altitude figures of all suspended spans;

3) model calculates: carry out following one or more computing, with obtain suspended span section intensity,

Rigidity and/or wet model frequency and/or fatigue lifetime.

A, single span computation model:

I. model specification:

A) its bending equations is:

${\mathrm{\ρ}}_e\frac{{\∂}^{2}w}{{\∂t}^2}+\frac{{\∂}^2}{{\∂x}^2}\left(\mathrm{EI}\frac{{\∂}^{2}w}{{\∂x}^2}\right)=q(x,t);$

ρ wherein _efor the equivalent density of extra large pipe, w is vertical deviation, the equivalent elastic modulus that E is extra large pipe, and the moment of inertia of cross-section that I is extra large pipe, q is external applied load.

The external applied load of this algorithm considered as the upper hydrodynamic nearly bottom effect of nearly bottom works sea pipe, and this effect is distinguished sea pipe hydrodynamic force and the hydrodynamic force of standpipe without bottom or other limit wall impacts, tension leg etc. to some extent.

For sea pipe suspended span, the scour pit degree of depth at diverse location place causes hydrodynamic force coefficient difference to some extent for a moment; And suspended span section is when stressed generation sedimentation deformation, changed near the flow field extra large pipe with the variation of bottom distance, thereby caused its hydrodynamic force to change.This process is the process of typical fluid-structural response Dynamic Coupling.Single span computing method have been simulated on different depth scour pit, and the hydrodynamic force coefficient while changing with bottom distance is managed in sea, thereby simulates the hydrodynamic force coefficient curved surface shown in Fig. 1, for the dynamic process calculating of suspended span sea pipe flexural subsidence.

B) edge-restraint condition is clamped/hinged;

C) external applied load is considered sea pipe self gravitation and two kinds of load of outflow muscle power, and outflow muscle power and bottom form and the depth of water, flow velocity are relevant.

Ii. mechanical analysis content:

A) according to sea pipe parameter and suspended span length, can carry out static load, mode and dynamically time domain calculating;

B) result of calculation can obtain respectively maximum deflection displacement, stress, wet model frequency, dynamic stress time-histories, the fatigue lifetime of suspended span section.

Iii. calculation process in batches:

A) according to suspended span start, end parameter, read in pipe design and mud face parameter;

B) according to suspended span length-diameter ratio, divide finite element mesh;

C) carry out the analytical calculation of one or more types;

D) output suspended span parameter and result of calculation thereof;

E) successively next suspended span is calculated.

B, multispan computation model:

For standoff distance nearer two sections or several sections of suspended spans, while there is deflection or vibration, its mechanical response behavior meeting influences each other, and is referred to as the multispan that is coupled, and the model that needs foundation to be different from single span is analyzed.

Iii. model specification:

A) across a constraint condition, adopt hinged being similar to, mathematical expression is as follows.

$\mathrm{iv}.\left\{\begin{array}{c}w\left(0\right)=w\left(L\right)=0\\ {\frac{\∂w\left(x\right)}{\∂x}|}_{x=0}={\frac{\∂w\left(x\right)}{\∂x}|}_{x=L}=0\end{array}\right.$

$v.\left\{\begin{array}{c}w\left(L_{{\mathrm{sh}}_{2k-1}}\right)=w\left(L_{{\mathrm{sh}}_{2k}}\right)=0\\ {\frac{{\∂}^{2}w\left(x\right)}{{\∂x}^2}|}_{x=L_{{\mathrm{sh}}_{2k-1}}}={\frac{{\∂}^{2}w\left(x\right)}{{\∂x}^2}|}_{x=L_{{\mathrm{sh}}_{2k}}}=0\end{array};k=12...n\right.$

Wherein, the total length that L is whole multispan, x is the position along tubular axis line, L _sh2k-1and L _sh2krepresent k section across the left end of shoulder and right-hand member respectively apart from the distance of multispan starting point, k is that k section in multispan is across shoulder;

B) all the other are identical with single span computation model.One large feature of this model is to have considered the intersegmental elastic restraint effect across the shoulder soil body of adjacent suspended span, contributes to obtain influencing each other of adjacent suspended span deflection and dynamic response.Therefore due to what ignore, be the elastic deformation across the shoulder soil body, with actual state gap slightly still, but this model form is simple, solves conveniently, has caught the main aspect of Problems Existing.

Vi. mechanical analysis content: identical with single span computation model.

Vii. calculation process in batches:

A) multispan identification: as two sections of adjacent suspended span length parameter L _sh/ L and L _a/ L meets regulation and stipulation relation (as shown in Figure 2), wherein, and L _shfor between suspended span across shoulder length degree, L, La are respectively the length of adjacent two sections of suspended spans;

B) all the other are identical with single span computation model.

2 kinds of related computation models of batch computation process of the present invention can also be combined arbitrarily and can be used separately, and many algorithms result contrasts the judgement that is conducive to dangerous suspended span mutually.

Provide the example of above-mentioned calculating detailed process below.

Take KP280～310 in certain extra large pipe is example, adopts single span and multispan computation model to carry out security to suspended span section wherein and checks and calculate, and the single span that wherein will check is 38 places, and multispan is 22 places.Following table is sea pipe and environmental parameter.

Adopt single span computation model to carry out static load and model analysis, following table is the suspended span parameter that transfinites (start, end KP, length) and the wet model frequency result of dimensionless maximum deflection, stress and dimensionless single order thereof obtaining.

Adopt multispan computation model to carry out static load and model analysis, following table is multispan parameter (start, end KP, length connect across number) and the wet model frequency result of dimensionless maximum deflection, stress and dimensionless single order thereof transfiniting again.

Adopt FINITE ELEMENT METHOD PROGRAMMING to realize said process, whole suspended span, multispan identification, automatic batch calculate less than consuming time 1 minute.By two kinds of the model calculation above, can be found out, multispan computation model due to considered across coupling, adjacent suspended span is made to as a whole its mechanical behavior of predicting, so the shorter suspended span that index does not exceed standard in single span computation model there will be the situation of exceeding standard.And this checks sea pipe security than simple code requirement algorithm in the past and more tallies with the actual situation, so provide accuracy higher data basis for sea pipe safety evaluation.

Claims (1)

1. submarine pipeline suspended span section security automatic batch is checked computing method, it is characterized in that, comprises the steps:

1) data are prepared: prepare sea pipe design parameter data, comprise material constant, thickness of pipe etc.; Obtain extra large pipeline by mud face altitude figures, comprising: extra large pipeline is put KP, mud face and extra large relative distance h, mud face absolute depth of managing lower edge by critical importance;

2) suspended span identification: according to h judgement suspended span start, end, obtain the mud face altitude figures of all suspended spans;

3) model calculates: carry out following one or more computing, with obtain suspended span section intensity,

Rigidity and/or wet model frequency and/or fatigue lifetime:

A, single span computation model:

Its mathematical expression is as follows:

${\mathrm{\ρ}}_e\frac{{\∂}^{2}w}{{\∂t}^2}+\frac{{\∂}^2}{{\∂x}^2}\left(\mathrm{EI}\frac{{\∂}^{2}w}{{\∂x}^2}\right)=q(x,t);$

ρ wherein _efor the equivalent density of extra large pipe, w is vertical deviation, the equivalent elastic modulus that E is extra large pipe, and the moment of inertia of cross-section that I is extra large pipe, q is external applied load;

B, multispan computation model:

Its mathematical expression is as follows:

$i.\left\{\begin{array}{c}w\left(0\right)=w\left(L\right)=0\\ {\frac{\∂w\left(x\right)}{\∂x}|}_{x=0}={\frac{\∂w\left(x\right)}{\∂x}|}_{x=L}=0\end{array}\right.$

$\mathrm{ii}.\left\{\begin{array}{c}w\left(L_{{\mathrm{sh}}_{2k-1}}\right)=w\left(L_{{\mathrm{sh}}_{2k}}\right)=0\\ {\frac{{\∂}^{2}w\left(x\right)}{{\∂x}^2}|}_{x=L_{{\mathrm{sh}}_{2k-1}}}={\frac{{\∂}^{2}w\left(x\right)}{{\∂x}^2}|}_{x=L_{{\mathrm{sh}}_{2k}}}=0\end{array};k=\mathrm{1,2},...n\right.$

Wherein, the total length that L is whole multispan, x is the position along tubular axis line, L _sh2k-1and L _sh2krepresent k section across the left end of shoulder and right-hand member respectively apart from the distance of multispan starting point, k is that k section in multispan is across shoulder;

4) according to suspended span section intensity, rigidity and/or the wet model frequency and/or the fatigue lifetime that obtain the security of submarine pipeline suspended span section being evaluated.

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