CN105468812A - Method for measuring reliability of buried suspended pipeline - Google Patents

Abstract

The present invention relates to the field of oil and gas pipelines, and discloses a method for measuring reliability of a buried suspended pipeline, to solve a technical problem in the prior art that reliability of a buried suspended pipeline cannot be measured accurately. The method comprises: determining yield strength sigma s of the buried suspended pipeline; according to the yield strength sigma s, determining a failure performance function, shown in the specification, of the buried suspended pipeline, wherein sigma 1 represents axial strength of the buried suspended pipeline, sigma 2 represents hoop stress of the buried suspended pipeline, and sigma 3 represents radial stress of the buried suspended pipeline; using a random sampling method to perform sampling for N times to obtain N sets of the axial strength sigma 1 and the hoop stress sigma 2; and according to a formula shown in the specification, determining a failure probability of the buried suspended pipeline, wherein when g(X)<0, Ig(X)=1, and when g(X)>=0, Ig(X)=0. According to the method, a technical effect of accurately measuring reliability of a buried suspended pipeline is achieved.

Description

A kind of buried suspended piping fiduciary level measuring method

Technical field

The present invention relates to oil and gas pipes field, particularly relate to a kind of buried suspended piping fiduciary level measuring method.

Background technology

Long-distance oil & gas pipeline geographical environment along the line is complicated, and under the impact of the geologic hazards such as natural cause and flood, landslide, Loess Collapsibility, buried oil and gas pipes pipe trench often occurs and corrodes, and even occurs exposed unsettled section of certain length.Now, under the Action of Gravity Field of pipeline self with interior fluid mediums self, suspended piping can deform, and larger distortion can cause pipeline failure, causes serious accident.

Given this, domestic and international many scholars analyze the safety of suspended piping from different perspectives.Such as, certain scholar establishes suspended piping sedimentation Failure Assessment model according to strength theory; Such as, certain scholar, for the Pipeline through Loess Plateau, utilizes theory of beam on elastic to analyze the mechanical model of pipeline when subsiding; Such as, certain scholar has carried out simulation calculation to the suspended piping under the coombe condition of earth's surface; Such as, certain scholar establishes the stressed elastic-plastic foundation model of Loess Collapsibility section suspended piping, and comparatively Winkler foundation model computational accuracy is higher to point out this model, more meets engineer applied.More than discuss and mostly check according to numerical simulation and the safe condition of strength theory to suspended piping, but can accurately not measure the fiduciary level of buried suspended piping.

Summary of the invention

The invention provides a kind of buried suspended piping fiduciary level measuring method, cannot exactly to the technical matters that the fiduciary level of buried suspended piping is measured in prior art to solve.

The embodiment of the present invention provides a kind of buried suspended piping fiduciary level measuring method, comprising:

Determine the yield strength σ of described buried suspended piping _s;

Based on described yield strength σ _sdetermine described buried suspended piping invalidation functions function $g\left(X\right)={\mathrm{\&sigma;}}_s-\sqrt{\frac{1}{2}\&lsqb;{({\mathrm{\&sigma;}}_1-{\mathrm{\&sigma;}}_2)}^2+{({\mathrm{\&sigma;}}_1-{\mathrm{\&sigma;}}_3)}^2+{({\mathrm{\&sigma;}}_2-{\mathrm{\&sigma;}}_3)}^2\&rsqb;},$ Wherein σ ₁represent the axial stress of described buried suspended piping, σ ₂represent the circumference stress of described buried suspended piping, σ ₃represent the radial stress of described buried suspended piping;

Adopt method of random sampling to carry out N sampling and obtain the described axial stress σ of N group ₁with described circumference stress σ ₂;

According to formula $P_f=\frac{1}{N}\underset{i=1}{\overset{N}{\&Sigma;}}Ig\left(X\right)$ Determine the failure probability of described buried suspended piping, wherein, as g (X) < 0, Ig (X)=1, as g (X) >=0, Ig (X)=0.

Optionally, described determine the failure probability of described buried suspended piping after, described method also comprises:

Based on formula determine the RELIABILITY INDEX of described buried suspended piping;

Wherein, β represents described RELIABILITY INDEX;

U represents the mean of a probability distribution of described invalidation functions function;

σ represents the standard deviation of the probability distribution of described invalidation functions function.

Optionally, described axial stress σ ₁following formulae discovery is adopted to obtain:

${\mathrm{\&sigma;}}_1={\mathrm{\&sigma;}}_p+{\mathrm{\&sigma;}}_{N_0}+{\mathrm{\&sigma;}}_q+{\mathrm{\&sigma;}}_{\mathrm{\&Delta;}t}$

Wherein, σ _pthe axial stress caused is pressed in representing;

represent the axial stress that horizontal pull causes;

σ _qrepresent the axial stress that pipeline moment of flexure causes;

σ _{Δ t}represent the axial stress that temperature difference causes.

Optionally, described circumference stress σ ₂obtained by following formulae discovery:

${\mathrm{\&sigma;}}_2=\frac{p_{a}D}{2t}$

Wherein, p _afor pressing in described buried suspended piping;

D represents the external diameter of described buried suspended piping;

T represents the wall thickness of described buried suspended piping.

Optionally, carry out N sampling at described employing method of random sampling and obtain the described axial stress σ of N group ₁with described circumference stress σ ₂before, described method also comprises:

Determine the suspended piping deflection differential equation of described buried suspended piping:

$EI\left(\frac{d^{2}y}{{\mathrm{dx}}^2}\right)=M_0+N_0(y-v_0)+\frac{{\mathrm{qx}}^2}{2}-\frac{qlx}{2}$

Wherein, M ₀represent the section turn moment of buried suspended piping described in pipeclay intersection;

N ₀represent the horizontal pull suffered by described buried suspended piping;

Y represents the longitudinal coordinate of described buried suspended piping;

X represents the lateral coordinates of described buried suspended piping;

ν ₀represent pipeclay intersection bending deflection of pipe;

Q represents the imposed load of described buried suspended piping;

L represents the length of described buried suspended piping;

Determine the maximal value position of the described differential equation.

Optionally, described employing method of random sampling carries out N the described axial stress σ of sampling acquisition N group ₁with described circumference stress σ ₂, be specially:

Method of random sampling is adopted to obtain the described axial stress σ of N group described maximal value position ₁.

Beneficial effect of the present invention is as follows:

Due in embodiments of the present invention, first determine the yield strength σ of described buried suspended piping _s; Then, based on described yield strength σ _sdetermine described buried suspended piping invalidation functions function $g\left(X\right)={\mathrm{\&sigma;}}_s-\sqrt{\frac{1}{2}\&lsqb;{({\mathrm{\&sigma;}}_1-{\mathrm{\&sigma;}}_2)}^2+{({\mathrm{\&sigma;}}_1-{\mathrm{\&sigma;}}_3)}^2+{({\mathrm{\&sigma;}}_2-{\mathrm{\&sigma;}}_3)}^2\&rsqb;},$ Wherein σ ₁represent the axial stress of described buried suspended piping, σ ₂represent the circumference stress of described buried suspended piping, σ ₃represent the radial stress of described buried suspended piping; Then, adopt method of random sampling to carry out N sampling and obtain the described axial stress σ of N group ₁with described circumference stress σ ₂; Finally, according to formula determine the failure probability of described buried suspended piping, wherein, as g (X) < 0, Ig (X)=1, as g (X)>=0, Ig (X)=0.In other words, can by the yield strength σ of buried suspended piping _s, axial stress σ ₁, circumference stress σ ₂with radial stress σ ₃determine the failure probability of buried suspended piping, and the reliability of buried suspended piping can be determined based on failure probability easily, reach the technique effect can measuring the reliability of buried pipeline accurately.

Accompanying drawing explanation

Fig. 1 is the process flow diagram of buried suspended piping fiduciary level measuring method in the embodiment of the present invention;

Fig. 2 is the schematic diagram of buried suspended piping mechanical model in the embodiment of the present invention;

Fig. 3 is earthing schematic diagram above pipeline in the embodiment of the present invention.

Embodiment

The invention provides a kind of buried suspended piping fiduciary level measuring method, cannot accurately to the technical matters that the fiduciary level of buried suspended piping is measured in prior art to solve.

Technical scheme in the embodiment of the present application is solve above-mentioned technical matters, and general thought is as follows:

First the yield strength σ of described buried suspended piping is determined _s; Then, based on described yield strength σ _sdetermine described buried suspended piping invalidation functions function $g\left(X\right)={\mathrm{\&sigma;}}_s-\sqrt{\frac{1}{2}\&lsqb;{({\mathrm{\&sigma;}}_1-{\mathrm{\&sigma;}}_2)}^2+{({\mathrm{\&sigma;}}_1-{\mathrm{\&sigma;}}_3)}^2+{({\mathrm{\&sigma;}}_2-{\mathrm{\&sigma;}}_3)}^2\&rsqb;},$ Wherein σ ₁represent the axial stress of described buried suspended piping, σ ₂represent the circumference stress of described buried suspended piping, σ ₃represent the radial stress of described buried suspended piping; Then, adopt method of random sampling to carry out N sampling and obtain the described axial stress σ of N group ₁with described circumference stress σ ₂; Finally, according to formula determine the failure probability of described buried suspended piping, wherein, as g (X) < 0, Ig (X)=1, as g (X)>=0, Ig (X)=0.That is, can by the yield strength σ of buried suspended piping _s, axial stress σ ₁, circumference stress σ ₂with radial stress σ ₃determine the failure probability of buried suspended piping, and the reliability of buried suspended piping can be determined based on failure probability easily, reach the technique effect of the reliability that can accurately measure buried pipeline.

In order to better understand technique scheme, below by accompanying drawing and specific embodiment, technical solution of the present invention is described in detail, the specific features being to be understood that in the embodiment of the present invention and embodiment is the detailed description to technical solution of the present invention, instead of the restriction to technical solution of the present invention, when not conflicting, the technical characteristic in the embodiment of the present invention and embodiment can combine mutually.

The embodiment of the present invention provides a kind of buried suspended piping fiduciary level measuring method, please refer to Fig. 1, comprising:

Step S101: the yield strength σ determining described buried suspended piping _s;

Step S102: based on described yield strength σ _sdetermine described buried suspended piping invalidation functions function $g\left(X\right)={\mathrm{\&sigma;}}_s-\sqrt{\frac{1}{2}\&lsqb;{({\mathrm{\&sigma;}}_1-{\mathrm{\&sigma;}}_2)}^2+{({\mathrm{\&sigma;}}_1-{\mathrm{\&sigma;}}_3)}^2+{({\mathrm{\&sigma;}}_2-{\mathrm{\&sigma;}}_3)}^2\&rsqb;},$ Wherein σ ₁represent the axial stress of described buried suspended piping, σ ₂represent the circumference stress of described buried suspended piping, σ ₃represent the radial stress of described buried suspended piping;

Step S103: adopt method of random sampling to carry out N sampling and obtain the described axial stress σ of N group ₁with described circumference stress σ ₂;

Step S104: according to formula determine the failure probability of described buried suspended piping, wherein, as g (X) < 0, Ig (X)=1, as g (X)>=0, Ig (X)=0.

In specific implementation process, example stochastic variable used in the embodiment of the present invention is as shown in table 1, and example constant is as shown in table 2, certainly, in specific implementation process, example random sum example constant can also be other values, and the embodiment of the present invention is not restricted.

Table 1

Stochastic variable

External diameter

Wall thickness

Buried depth

Pendulous tank

Yield strength

Interior pressure

The temperature difference

Symbol

D

t

h

l

σ s

p a

Δt

Distribution pattern

Normal distribution

Normal distribution

Normal distribution

Be uniformly distributed

Normal distribution

Normal distribution

Be uniformly distributed

Average

1.016

17.5

2.0

20

485

10

10

Standard deviation

0.007

0.28

0.05

11.5

15

1.2

1.2

Unit

m

mm

m

m

MPa

MPa

℃

Table 2

In step S101, directly can obtain the yield strength σ of buried suspended piping by look-up table 1 _s.

In specific implementation process, carry out N sampling adopting method of random sampling based on step S102 and obtain the described axial stress σ of N group ₁with described circumference stress σ ₂before, described method also comprises:

Determine the suspended piping deflection differential equation of described buried suspended piping:

$EI\left(\frac{d^{2}y}{{\mathrm{dx}}^2}\right)=M_0+N_0(y-v_0)+\frac{{\mathrm{qx}}^2}{2}-\frac{qlx}{2}$

Wherein, M ₀represent the section turn moment of buried suspended piping described in pipeclay intersection;

N ₀represent the horizontal pull suffered by described buried suspended piping;

Y represents the longitudinal coordinate of described buried suspended piping;

X represents the lateral coordinates of described buried suspended piping;

ν ₀represent pipeclay intersection bending deflection of pipe;

Q represents the imposed load of described buried suspended piping;

L represents the length of described buried suspended piping;

Determine the maximal value position of the described differential equation.

And then in step S103, described employing method of random sampling carries out N sampling and obtains the described axial stress σ of N group ₁, be specially: adopt method of random sampling to obtain the described axial stress σ of N group described maximal value position ₁.

In step S103, described axial stress σ ₁following formulae discovery is adopted to obtain:

${\mathrm{\&sigma;}}_1={\mathrm{\&sigma;}}_p+{\mathrm{\&sigma;}}_{N_0}+{\mathrm{\&sigma;}}_q+{\mathrm{\&sigma;}}_{\mathrm{\&Delta;}t}$

Wherein, σ _pthe axial stress caused is pressed in representing;

represent the axial stress that horizontal pull causes;

σ _qrepresent the axial stress that pipeline moment of flexure causes;

σ _{Δ t}represent the axial stress that temperature difference causes.

In step S103, described circumference stress σ ₂obtained by following formulae discovery:

${\mathrm{\&sigma;}}_2=\frac{p_{a}D}{2t}$

Wherein, p _afor pressing in described buried suspended piping;

D represents the external diameter of described buried suspended piping;

T represents the wall thickness of described buried suspended piping.

As a kind of optional embodiment, after the failure probability determining described buried suspended piping based on step S104, described method also comprises:

Based on formula determine the RELIABILITY INDEX of described buried suspended piping;

Wherein, β represents described RELIABILITY INDEX;

U represents the mean of a probability distribution of described invalidation functions function;

σ represents the standard deviation of the probability distribution of described invalidation functions function.

Optionally, described axial stress σ ₁following formulae discovery is adopted to obtain:

${\mathrm{\&sigma;}}_1={\mathrm{\&sigma;}}_p+{\mathrm{\&sigma;}}_{N_0}+{\mathrm{\&sigma;}}_q+{\mathrm{\&sigma;}}_{\mathrm{\&Delta;}t}$

Wherein, σ _pthe axial stress caused is pressed in representing;

represent the axial stress that horizontal pull causes;

σ _qrepresent the axial stress that pipeline moment of flexure causes;

σ _{Δ t}represent the axial stress that temperature difference causes.

Optionally, described circumference stress σ ₂obtained by following formulae discovery:

${\mathrm{\&sigma;}}_2=\frac{p_{a}D}{2t}$

Wherein, p _afor pressing in described buried suspended piping;

D represents the external diameter of described buried suspended piping;

T represents the wall thickness of described buried suspended piping.

The buried suspended piping fiduciary level measuring method further understood the embodiment of the present invention to enable those skilled in the art and introduce, is introduced the application in this way in specific implementation process it below.

The method specifically comprises the following steps:

Step 1: set up buried suspended piping mechanical model, as shown in Figure 2.

Step 1-1: set up suspended piping deflection differential equation according to the stress model of pipeline:

$EI\left(\frac{d^{2}y}{{\mathrm{dx}}^2}\right)=M_0+N_0(y-v_0)+\frac{{\mathrm{qx}}^2}{2}-\frac{qlx}{2}$

Step 1-2: calculate pipeclay intersection pipeline section moment of flexure:

$M_0=(\frac{ql}{2}-\frac{{\mathrm{ql\&beta;}}^2{N}_0}{k_{0}d}-\frac{q}{k}th(\frac{kl}{2}\left)\right)/(\frac{4{\mathrm{\&beta;}}^3{N}_0}{k_{0}d}+kth(\frac{kl}{2}\left)\right)$

Step 1-3: calculate suspended piping arbitrary section moment of flexure:

$M\left(x\right)=M_0(\frac{e^{kx}}{1+e^{kl}}+\frac{e^{-kx}}{1+e^{-kl}})+\frac{q}{k^2}(\frac{e^{kx}}{1+e^{kl}}+\frac{-e^{kx}}{1+e^{-kl}}-1)$

Wherein: $\mathrm{\&beta;}=\sqrt[4]{\frac{k_{z}d}{4EI}},k=\sqrt{\frac{N_0}{EI}},I=\frac{\mathrm{\&pi;}(D^2-d^2)}{4},N_0=\mathrm{\&pi;}D\&lsqb;c+\frac{1}{2}\mathrm{\&gamma;}h(1+K_0)tg\mathrm{\&phi;}\&rsqb;l^{\&prime;}+{\mathrm{ql}}^{\&prime;}tg\mathrm{\&phi;}$

In formula, M ₀represent the section turn moment of buried suspended piping described in pipeclay intersection; N ₀represent the horizontal pull suffered by described buried suspended piping; E is tubing elastic modulus, and I is pipeline section moment of inertia, ν ₀for pipeclay intersection bending deflection of pipe, d is internal diameter of the pipeline, and q is the imposed load of suspended piping, and l is suspended piping length, k _zfor bed base system number, N ₀horizontal pull suffered by pipeline, c is the cohesive force of soil, and φ is the angle of friction of soil, and l' is the deformable length (1.5 times that get suspended piping length) that pipeline stretches in the soil body, and γ is the unit weight of soil, K ₀for coefficient of static earth pressure, β is an intermediate variable, constant for its β value of specific pipeline.

Step 2: the imposed load calculating suspended piping;

Step 2-1: according to the deadweight of unit of account length tube, wherein ρ _pfor Pipes Density, D is outer diameter tube, and g is acceleration of gravity;

Step 2-2: according to q ₂=100p _ad ²the weight of unit of account length tube inner high voltage gas, wherein p _afor pressing in pipeline, in usual pipeline, pressure is the normalization numerical value of operation pipeline, relevant with throughput rate, and each production department of pipeline company and field, station all can be apparent;

Step 2-3: according to q ₃=hD ρ _sthe weight of soil layer above g unit of account length tube, wherein h is buried depth of pipeline, ρ _sfor covered soil density above pipeline, wherein, above pipeline, covered soil density can be tabled look-up according to the type of actual field soil and to be obtained or field measurement obtains, and is illustrated in figure 3 earthing schematic diagram above pipeline.

Therefore, the imposed load of suspended piping $q=\frac{1}{4}{\mathrm{\&pi;\&rho;}}_{p}g(D^2-d^2)+100p_a{d}^2+{\mathrm{hD\&rho;}}_{s}g$

Step 3: the stress calculating pipeline;

Step 3-1: according to calculate the axial stress of pipeline, in formula σ _{Δ t}=E α Δ t, wherein, t is pipeline wall thickness, S _sfor wall cross-section area, W is pipeline bending resistant section coefficient, and α is tubing coefficient of thermal expansion, with temperature difference when running when Δ t is Pipe installing.

Step 3-2: according to ${\mathrm{\&sigma;}}_2=\frac{p_{a}D}{2t}$ Calculate the circumference stress of pipeline;

Step 3-3: pipeline is considered as thin wall cylinder, according to σ ₃the radial stress of=0 calculating pipeline.

Step 4: by pipeline axial stress σ ₁, circumference stress σ ₂with radial stress σ ₃substitute into the invalidation functions function of suspended piping;

Invalidation functions function is: $g\left(X\right)={\mathrm{\&sigma;}}_s-\sqrt{\frac{1}{2}\&lsqb;{({\mathrm{\&sigma;}}_1-{\mathrm{\&sigma;}}_2)}^2+{({\mathrm{\&sigma;}}_1-{\mathrm{\&sigma;}}_3)}^2+{({\mathrm{\&sigma;}}_2-{\mathrm{\&sigma;}}_3)}^2\&rsqb;},$ Wherein, σ _sfor the yield strength of pipeline.

Step 5: the fiduciary level calculating suspended piping.

Step 5-1: determine the stochastic variable in invalidation functions function and probability distribution thereof.In this example, the stochastic variable of invalidation functions function is respectively outer diameter tube, wall thickness, buried depth, pendulous tank, yield strength, interior pressure and the temperature difference, wherein pendulous tank is interval [0,40] obey in and be uniformly distributed, the temperature difference is obeyed and is uniformly distributed in interval [0,20], the equal Normal Distribution of other stochastic variable, statistical parameter is in table 1, and the constant of invalidation functions function is in table 2.

Step 5-2: adopt Monte Carlo method of random sampling according to $P_f=\frac{1}{N}\underset{i=1}{\overset{N}{\&Sigma;}}Ig\left(X\right)$ Calculate pipeline failure probability, wherein, N is frequency in sampling, as g (X) < 0, and I=1, as g (X) >=0, I=0.Based on example parameter, in Matlab, carry out sampling simulation, number realization N=10 ⁶secondary, calculating and trying to achieve pipeline failure probability is 0.0167

Step 5-3: the fiduciary level P=1-P calculating suspended piping _f=98.33%.

The one or more embodiment of the present invention, at least has following beneficial effect:

Due in embodiments of the present invention, first determine the yield strength σ of described buried suspended piping _s; Then, based on described yield strength σ _sdetermine described buried suspended piping invalidation functions function $g\left(X\right)={\mathrm{\&sigma;}}_s-\sqrt{\frac{1}{2}\&lsqb;{({\mathrm{\&sigma;}}_1-{\mathrm{\&sigma;}}_2)}^2+{({\mathrm{\&sigma;}}_1-{\mathrm{\&sigma;}}_3)}^2+{({\mathrm{\&sigma;}}_2-{\mathrm{\&sigma;}}_3)}^2\&rsqb;},$ Wherein σ ₁represent the axial stress of described buried suspended piping, σ ₂represent the circumference stress of described buried suspended piping, σ ₃represent the radial stress of described buried suspended piping; Then, adopt method of random sampling to carry out N sampling and obtain the described axial stress σ of N group ₁with described circumference stress σ ₂; Finally, according to formula $P_f=\frac{1}{N}\underset{i=1}{\overset{N}{\&Sigma;}}Ig\left(X\right)$ Determine the failure probability of described buried suspended piping, wherein, as g (X) < 0, Ig (X)=1, as g (X) >=0, Ig (X)=0.In other words, can by the yield strength σ of buried suspended piping _s, axial stress σ ₁, circumference stress σ ₂with radial stress σ ₃determine the failure probability of buried suspended piping, and the reliability of buried suspended piping can be determined based on failure probability easily, reach the technique effect can measuring the reliability of buried pipeline accurately.

Although describe the preferred embodiments of the present invention, those skilled in the art once obtain the basic creative concept of cicada, then can make other change and amendment to these embodiments.So claims are intended to be interpreted as comprising preferred embodiment and falling into all changes and the amendment of the scope of the invention.

Obviously, those skilled in the art can carry out various change and modification to the present invention and not depart from the spirit and scope of the present invention.Like this, if these amendments of the present invention and modification belong within the scope of the claims in the present invention and equivalent technologies thereof, then the present invention is also intended to comprise these change and modification.

Claims (6)

1. a buried suspended piping fiduciary level measuring method, is characterized in that, comprising:

Determine the yield strength σ of described buried suspended piping _s;

Based on described yield strength σ _sdetermine described buried suspended piping invalidation functions function wherein σ ₁represent the axial stress of described buried suspended piping, σ ₂represent the circumference stress of described buried suspended piping, σ ₃represent the radial stress of described buried suspended piping;

Adopt method of random sampling to carry out N sampling and obtain the described axial stress σ of N group ₁with described circumference stress σ ₂;

According to formula determine the failure probability of described buried suspended piping, wherein, as g (X) < 0, Ig (X)=1, as g (X)>=0, Ig (X)=0.

2. the method for claim 1, is characterized in that, described determine the failure probability of described buried suspended piping after, described method also comprises:

Based on formula determine the RELIABILITY INDEX of described buried suspended piping;

Wherein, β represents described RELIABILITY INDEX;

U represents the mean of a probability distribution of described invalidation functions function;

σ represents the standard deviation of the probability distribution of described invalidation functions function.

3. the method for claim 1, is characterized in that, described axial stress σ ₁following formulae discovery is adopted to obtain:

Wherein, σ _pthe axial stress caused is pressed in representing;

represent the axial stress that horizontal pull causes;

σ _qrepresent the axial stress that pipeline moment of flexure causes;

σ _{Δ t}represent the axial stress that temperature difference causes.

4. method as claimed in claim 3, is characterized in that, described circumference stress σ ₂obtained by following formulae discovery:

Wherein, p _afor pressing in described buried suspended piping;

D represents the external diameter of described buried suspended piping;

T represents the wall thickness of described buried suspended piping.

5. method as claimed in claim 4, is characterized in that, carries out N sampling obtain the described axial stress σ of N group at described employing method of random sampling ₁with described circumference stress σ ₂before, described method also comprises:

Determine the suspended piping deflection differential equation of described buried suspended piping:

Wherein, M ₀represent the section turn moment of buried suspended piping described in pipeclay intersection;

N ₀represent the horizontal pull suffered by described buried suspended piping;

Y represents the longitudinal coordinate of described buried suspended piping;

X represents the lateral coordinates of described buried suspended piping;

ν ₀represent pipeclay intersection bending deflection of pipe;

Q represents the imposed load of described buried suspended piping;

L represents the length of described buried suspended piping;

Determine the maximal value position of the described differential equation.

6. method as claimed in claim 5, is characterized in that, described employing method of random sampling carries out N sampling and obtains the described axial stress σ of N group ₁, be specially:

Described method of random sampling is adopted to obtain the described axial stress σ of N group described maximal value position ₁.