CN114595544B - Comprehensive safety evaluation method for buried pipeline in coal mine goaf - Google Patents
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Abstract
The invention discloses a comprehensive safety evaluation method for a buried pipeline in a coal mine goaf, which relates to the field of oil and gas transmission and comprises the steps of obtaining a surface subsidence displacement curve of the goaf; dividing a goaf surface displacement early warning interval according to the surface subsidence displacement curve; acquiring a pipeline dynamic stress curve, and dividing a pipeline dynamic early warning interval; and comprehensively evaluating the buried pipeline in the goaf to obtain a comprehensive evaluation grade by combining the displacement early warning interval of the surface of the goaf and the dynamic early warning interval of the pipeline. The invention provides a comprehensive safety evaluation method for a buried pipeline in a coal mine goaf, which aims to solve the problem that the comprehensive safety evaluation of the buried pipeline penetrating through the coal mine goaf is difficult in the prior art, realize the comprehensive evaluation of the dynamic risk of the buried pipeline penetrating through the coal mine goaf, provide a complete model for actual prediction and early warning and provide a guidance basis for engineering evaluation.
Description
Technical Field
The invention relates to the field of oil and gas transmission, in particular to a comprehensive safety evaluation method for a buried pipeline in a coal mine goaf.
Background
Along with the large-scale exploitation of coal mine resources, the forming range of a goaf is gradually enlarged. Therefore, the influence on various buildings and structures on the ground is increased. The petroleum and natural gas are used as one of the main energy sources, and the long oil and gas pipeline is called as the largest transportation carrier element by national economic arteries. The oil and gas pipeline inevitably passes through a plurality of complex regions in the transportation process, and then meets a plurality of geological disasters, the coal mine goaf subsidence is one of more typical disasters, and the oil and gas pipeline inevitably passes through the coal mine goaf in the long-distance transportation process, so that the oil and gas pipeline is damaged greatly.
Taking a west-east gas pipeline laying area as an example, the west-east gas pipeline laying engineering is laid along a line through 9 provinces, the line is laid through about 76 coal mine mining goafs, wherein 8 major goafs are located in four provinces such as Shanxi and Ningxia, the length of a pipe section affected by coal mine mining is about 388 kilometers in total, and the oil and gas pipeline passing through the coal mine goafs not only affects the mining of underground coal mine resources, but also seriously affects the transportation performance of the oil and gas pipeline.
For a coal mine goaf, excessive mining is highly likely to cause secondary geological disasters such as surface cracking and even collapse. When an oil and gas pipeline passes through a mining area, the pipeline is mainly bent and pulled due to the subsidence effect of the earth surface, and if the pipeline passes through the rapid subsidence area formed in the mining area, the pipeline can be suspended or even broken. However, in the prior art, no specific and comprehensive safety judgment standard exists for critical damage of an oil and gas pipeline penetrating through a coal mine goaf.
Disclosure of Invention
The invention provides a comprehensive safety evaluation method for a buried pipeline in a coal mine goaf, which aims to solve the problem that the comprehensive safety evaluation of the buried pipeline penetrating through the coal mine goaf is difficult in the prior art, realize the comprehensive evaluation of the dynamic risk of the buried pipeline penetrating through the coal mine goaf, provide a complete model for actual prediction and early warning and provide a guide basis for engineering evaluation.
The invention is realized by the following technical scheme:
a comprehensive safety evaluation method for buried pipelines in a coal mine goaf comprises the following steps:
acquiring a ground surface subsidence displacement curve of the goaf; dividing a goaf surface displacement early warning interval according to the surface subsidence displacement curve;
acquiring a pipeline dynamic stress curve, and dividing a pipeline dynamic early warning interval;
and comprehensively evaluating the buried pipeline in the goaf to obtain a comprehensive evaluation grade by combining the displacement early warning interval of the surface of the goaf and the dynamic early warning interval of the pipeline.
The invention provides a comprehensive safety evaluation method for a buried pipeline in a coal mine goaf, aiming at the problem that the buried pipeline penetrating through the coal mine goaf is difficult to comprehensively evaluate safety in the prior art. The inventor finds that the surface subsidence deformation is a gradual influence process from bottom to top formed by the gradual mining of an underground coal bed, the subsidence of the surface directly influences the safe operation of a buried pipeline in the area, and the existing technology completely ignores the factor. Therefore, the method comprises the steps of firstly obtaining a ground surface subsidence displacement curve of the goaf, and then dividing a goaf ground surface displacement early warning interval according to the obtained ground surface subsidence displacement curve; then, acquiring a dynamic stress curve of the pipeline, and dividing a dynamic early warning interval of the pipeline based on a stress failure criterion; and finally, comprehensively evaluating the buried pipeline in the goaf by combining the obtained goaf surface displacement early warning interval and the obtained pipeline dynamic early warning interval. The method has the advantages that the ground surface subsidence displacement of the goaf and the dynamic stress of the buried pipeline penetrating through the goaf are combined, the comprehensive evaluation method suitable for the buried pipeline of the coal mine goaf is established, the blank of the prior art is filled, the dynamic safety risk of the buried pipeline penetrating through the coal mine goaf can be comprehensively evaluated, a complete model is provided for actual prediction and early warning, and a guidance basis is provided for engineering evaluation.
Further, the method for obtaining the ground surface subsidence displacement curve of the goaf comprises the following steps:
setting a calculation point, and calculating the maximum subsidence value of the ground surface of the goaf;
and obtaining a dynamic subsidence equation based on the segmented Knothe time function, and drawing a surface subsidence displacement curve according to the dynamic subsidence equation.
The Knothe time function model accords with a creep theory, and the sinking speed at the time of surface sinking is considered to be the final sinking value of the surface, and the difference of the dynamic sinking values at the time is in a certain proportional relation. The segmented Knothe time function is an improvement of the original Knothe time function, and the earth surface settlement amount obtained through prediction is more accurate and has smaller error. According to the scheme, the equation expression of the subsidence of the earth surface is obtained based on the combination of the segmented Knothe time function and the maximum subsidence value, and the subsidence displacement curve of the earth surface can be drawn.
Furthermore, those skilled in the art will appreciate that the Knothe time function is a term commonly used in the art, without standard Chinese translation.
Further, the maximum subsidence value of the goaf ground surface is calculated by the following formula:W m =hqcosψ；
in the formula (I), the compound is shown in the specification,W m is the maximum sinking value;his the thickness of the coal bed;qis the sinking coefficient;ψis the coal bed inclination angle;
the dynamic subsidence equation is:
in the formula (I), the compound is shown in the specification,W(t) Is the maximum sinking point dynamic sinking value;tis time;cis a time coefficient;τthe time when the maximum sinking speed occurs at the surface point is taken as the reference point;Tis the total sinking duration;Ф 1 (t)、Ф 2 (t) As a function of segmented Knothe time;eis a natural logarithm.
Further, the method for acquiring the dynamic stress curve of the pipeline comprises the following steps:
setting a calculation point, and calculating the maximum subsidence value of the ground surface of the goaf;
calculating the radius of influence of the goaf on the coal seam, and taking the edge of the radius of influence as a sinking initial point of pipeline deformation;
calculating the bending moment of the pipeline at the sinking initial point;
calculating the dynamic stress of the pipeline according to the maximum sinking value, the influence radius and the bending moment of the pipeline at the sinking initial pointσ 1 ；
Calculating stress of pipeline due to internal pressureσ 0 ；
Calculating the ultimate stress of the pipeσ：σ=σ 1 +σ 0 ；
According to final stressσAnd drawing a dynamic stress curve of the pipeline.
The dynamic stress curve of the pipeline can reflect the stress-strain condition of the buried pipeline when the buried pipeline passes through a coal mine mining space region, and the dynamic stress curve of the scheme adopts the dynamic stress of the pipelineσ 1 On the basis, the stress condition of the pipeline due to the internal pressure is considered, and the sum of the two is used as the final stress to draw a pipeline dynamic stress curve. Compared with the conventional mode of directly taking dynamic stress as a stress analysis basis, the method has more practical engineering application value. Of course, the dynamic stress can be obtained by those skilled in the art according to the existing stress analysis means, and will not be described herein.
Further, the maximum subsidence value of the ground surface of the goaf is calculated by the following formula:W m =hqcosψ(ii) a In the formula (I), the compound is shown in the specification,W m is the maximum sinking value;hthe thickness of the coal bed;qis the sinking coefficient;ψis the coal seam dip angle;
the influence radius is calculated by the following formula:r=H/tanα(ii) a In the formula (I), the compound is shown in the specification,rin order to influence the radius of the film,Hthe mining depth of the coal bed is determined,αto mine the angle of influence;
if the buried pipeline belongs to pipe-soil cooperative deformation in the goaf, the bending moment of the pipeline at the sinking initial point is calculated by the following formula:
in the formula (I), the compound is shown in the specification,M A the bending moment of the pipeline at the sinking starting point,W(l 1 ,γ) Is the sinking value of the maximum sinking point of the pipeline,Lfor the distance of the convergence starting point to the calculation point,EIin order to provide the bending stiffness of the pipe,λto set the coefficient, and
，kis the elastic foundation coefficient;
if the buried pipeline belongs to pipe-soil non-cooperative deformation in the goaf, the bending moment of the pipeline at the sinking initial point is calculated by the following formula:
in the formula (I), the compound is shown in the specification,M A the bending moment of the pipeline at the sinking starting point,EIin order to be able to provide the bending stiffness of the pipe,y D is the sinking value of the tail end of the dark suspension area,x D the distance from the sinking starting point to the tail end of the dark suspended area,iis the ground surface gradient corresponding to the tail end of the dark suspension area,λto set the coefficient, and
，kis the elastic foundation coefficient;
stress on pipes due to internal pressureσ 0 Calculated by the following formula:σ 0 =PD/2S(ii) a In the formula (I), the compound is shown in the specification,Pfor the purpose of the internal pressure of the pipeline,Dis the outer diameter of the pipeline,Sthe wall thickness of the pipe.
The pipe-soil cooperative deformation refers to the condition that the change of the earth surface is small at the early mining stage, and the buried pipeline deforms together with the soil body in the small change process of the earth surface;
the pipe-soil non-cooperative deformation refers to that the ground settlement is continuously increased along with the continuous development of mining, when the deformation of a soil body below a pipeline is larger than that of the pipeline, the deformation of the pipeline and the soil body is shown as that the pipeline is separated from the soil body at the maximum sinking point, and a local hidden suspension state below the pipeline appears, and the pipe-soil non-cooperative deformation is called at this moment. In the pipe-soil non-cooperative deformation stage, the pipeline in the hidden suspension area bears the self weight of the pipeline and the weight of the soil body borne by the pipeline from the upper side. And the supporting force of the soil body below the pipeline is larger when the pipe-soil part without the hidden suspension state is closer to the edge of the goaf. With the continuous development of mining, the mining area is larger and larger, and the formed dark suspension area is larger and larger. When the formed dark suspension area is large enough, the soil above the pipeline can crack due to the sinking of the surrounding soil. Therefore, pipe-soil non-cooperative deformation is a more complex mechanical model, but is also a practical situation more easily encountered in engineering sites.
In the process of calculating the bending moment, the buried pipeline in the goaf belongs to two conditions of pipe-soil cooperative deformation or pipe-soil non-cooperative deformation, and bending moment calculation formulas which are respectively suitable for the buried pipeline and the pipe-soil cooperative deformation are respectively provided in a targeted manner, so that the calculation accuracy and precision of subsequent dynamic stress are obviously improved.
Further, the method for dividing the goaf surface displacement early warning interval comprises the following steps:
drawing a tangent angle change diagram of the displacement curve according to the surface subsidence displacement curve;
finding out two critical time points with the tangent angle equal to 45 degrees in the tangent angle change diagram of the displacement curve, and recording the two critical time points asT 1 、T 2 WhereinT 1 ＜T 2 ；
Dividing a goaf surface displacement early warning interval:
if the time t satisfies t < (R) >T 1 Then dividing into primary early warning;
if the time t is satisfiedT 1 ≤t＜T 2 If so, classifying the early warning into a middle early warning;
if the time t is satisfiedT 2 And (5) dividing the early warning into high-grade early warnings if the t is less than or equal to t.
According to the scheme, the displacement curve tangent angle is introduced to carry out scientific and reasonable early warning interval division on the displacement change of the earth surface.
The inventor finds that the goaf surface deformation is divided into three processes of a surface subsidence initial period, an active period and a decline period in a large amount of research processes, and the speed of the goaf surface deformation is changed from slow to fast and then slow. Therefore, when the tangent angle formed by the surface change rate in unit time is less than 45 degrees, the initial period of surface subsidence, namely the initial deformation stage, can be defined; defining the tangent angle formed by the earth surface change rate in unit time as an earth surface displacement active period, namely an earth surface accelerated deformation stage, when the tangent angle is more than 45 degrees; after the accelerated deformation stage, the tangent angle formed by the surface change rate in unit time is less than 45 degrees and is defined as the surface displacement regression period, namely the deceleration deformation stage.
Therefore, the scheme adopts two critical time points with the tangent angle equal to 45 degrees in the displacement curve tangent angle change diagramT 1 、T 2 And the displacement is used as a critical point for dividing the goaf surface displacement early warning interval. Wherein the risk levels of the primary, intermediate, and advanced pre-warnings increase in sequence, as will be appreciated by those skilled in the art.
When t <T 1 In the process, the mining area of the underground coal mine is not large, the stress redistribution area of the rock stratum is not large, so that the rock stratum moves slowly, the time required for the rock stratum to reach a stress rebalancing state is long, and the displacement of the earth surface also moves slowly. In the stage, the earth surface is just beginning to move and deform, the moving speed is not large, so that the influence on the change of the mechanical behavior of the pipeline is not large, the threat degree of the mining process to the pipeline is small, and the pipeline is in the initial deformation stage along with the slow deformation of the earth surface. Therefore, the danger degree of the pipeline and the ground surface of the goaf is smaller at this stage, and the ground surface displacement early warning interval of the goaf is divided into primary early warnings.
When in useT 1 ≤t＜T 2 And the mining area of the coal mine reaches a certain scale, so that a large area of rock stratum moves, the original stress damage range of the rock stratum is wider due to the larger mining area, so that the overlying rock stratum needs a larger area for stress rebalancing, and the rock stratum moves faster at the moment. Because the deformation speed of the earth surface is high and the deformation displacement is large at this stage, the mechanical behavior of the pipeline is greatly changed at this stage, and the gradual mining of the goaf has great threat to the pipeline. Therefore, the goaf surface displacement early warning interval at the stage is divided into middle-level early warnings.
When in useT 2 At t, the coal mining is substantially complete, and only a small amount of the area previously mined is required at this stage due to the movement of the formation through the active period of the formationThe displacement movement of the rock stratum can achieve the rebalancing of the rock stratum stress, and the displacement change rate at the stage is slow. However, the earth surface still has partial displacement at this stage, and the partial displacement determines whether the pipeline is damaged at some time, so that collapse and complicated and changeable geology exist in the goaf, the stress and strain of the pipeline are increased, and the danger degree of the pipeline is increased. Therefore, the goaf surface displacement early warning interval at the stage is divided into high-grade early warnings.
Further, the method for dividing the dynamic early warning intervals of the pipeline comprises the following steps:
if the time t satisfies t <T 1 Then, dividing into first-level early warning;
if the time t is satisfiedT 1 ≤t＜T 3 Dividing the early warning into two levels;
if the time t is satisfiedT 3 ≤t＜T 4 If yes, dividing into three-stage early warning;
if the time t is satisfiedT 4 If t is less than or equal to t, four-level early warning is divided;
wherein the content of the first and second substances,T 3 is a critical time point of three-level early warning,T 4 All are four-stage early warning critical time points; and the risk levels of the first-level early warning, the second-level early warning, the third-level early warning and the fourth-level early warning are sequentially increased.
Is calculated by the following formulaT 4 ：
In the formula (I), the compound is shown in the specification,Dis the outer diameter of the pipeline,M A the bending moment of the pipeline at the sinking starting point,Iin order to obtain the moment of inertia of the pipeline,Lfor the distance of the sink start point to the calculation point,λto set the coefficients, an
，kIs the elastic foundation coefficient;Ф(T 4 ) Is taken for an independent variableT 4 A Knothe time function of time;σ flexion Is the pipeline yield stress;
is calculated by the following formulaT 3 ：T 3 = T 4 -T'; wherein T' is the total time required for pipeline maintenance.
The total time required for maintaining the pipeline is calculated by the following formula: t' = T 1 + t 2 + t 3 (ii) a Wherein t is 1 For the Emergency mobilization duration, t 2 The time required for personnel to go out and arrive at the disaster site, t 3 The time is long for starting the maintenance till the completion.
The buried oil and gas pipeline penetrating through the goaf is influenced by gradual mining of the coal bed, the pipeline can deform at different speeds along with the movement of the earth surface, and the division of the dynamic early warning interval of the pipeline is used for quantitatively evaluating the safety risk caused by the deformation.
When the pipeline normally runs and passes through a mining space region, the stress strain and displacement of the pipeline are in a slow deformation stage, and a pipeline dynamic early warning interval is divided into first-stage early warnings;
when in useT 1 ≤t＜T 3 When the stress-strain on the pipe suddenly starts to accelerate or the stress-strain on a certain section of the pipe suddenly changes, i.e. fromT 1 And at the moment, the pipeline dynamic early warning interval enters a second-stage early warning, and in the stage, because the stress-strain change speed of the pipeline is high, the maximum stress change rule in the pipeline in the area needs to be concerned in real time, and preparation work for making emergency response needs to be started.
When in useT 3 ≤t＜T 4 When the pipeline dynamic early warning interval passes through the second-stage early warning stage, the goaf continuously sinks, so that when the pipeline is close to the yield limit, the deformation of the earth surface of the goaf can still be in the active period, namely the deformation rate of the pipeline is still high, the influence degree on the pipeline is high, and the early warning level is upgraded to the third-stage early warning. At the moment, in order to make a series of timely emergency response actions such as mobilization, departure, arrival, mobilization and maintenance before the pipeline yields and also consider factors such as complex geology, inconvenient actions and the like of certain coal mine working areas, the maintenance work needs to be completed before the pipeline achieves red early warning.
Two-stage pretreatmentThe time limit between the alarm and the three-level early warning isT 3 The specific value can be determined according to the maximum stress change rate, the distance between the emergency point and the position of the pipeline disaster, the training technical level of the maintenance and repair team, the technical level of emergency equipment, the level of road condition natural conditions and the expected failure severity.
When the temperature is higher than the set temperatureT 4 When the stress is less than or equal to t, the maximum stress on the pipeline is about to reach the yield limit, and if the stress of the pipeline is continuously increased, serious safety accidents such as pipeline damage and the like can occur. Therefore, the pipeline needs to be repaired and maintained before the pipeline reaches the yield limit, and the safe operation of the pipeline is ensured. It is considered that the surface deformation is still in an accelerated deformation state if the coal mine goaf is still in an active period when the pipeline is about to reach the yield limit, i.e. the pipeline stress change will quickly reach the yield limit. Therefore, the time point when the pipeline stress reaches 90% yield limit is taken as the four-stage early warning time point, and the time point is taken as the emergency response maintenance work ending time point, and the time point is calculated by the following formulaT 4 ：
Wherein the content of the first and second substances,Ф(T 4 ) Is taken for an independent variableT 4 The knohe time function of time; it will be understood by those skilled in the art that if a piecewise Knothe time function is employed, this is based onT 4 And in which segmentation time, a corresponding formula is adopted.
Further, the method for comprehensively evaluating the buried pipeline in the goaf comprises the following steps:
if the pipeline dynamic early warning interval belongs to four-level early warning, the comprehensive evaluation grade is a catastrophe grade;
if the pipeline dynamic early warning interval belongs to three levels of early warning, the comprehensive evaluation level is an alarm level;
if the pipeline dynamic early warning interval belongs to the second-level early warning, the comprehensive evaluation level is the warning level;
if the pipeline dynamic early warning interval belongs to primary early warning and the goaf surface displacement early warning interval is primary early warning, the comprehensive evaluation grade is attention grade;
and if the pipeline dynamic early warning interval belongs to a first-level early warning and the goaf surface displacement early warning interval is a middle-level early warning or a high-level early warning, the comprehensive evaluation grade is a warning grade.
Because a mature model for carrying out comprehensive early warning on a buried pipeline penetrating through a coal mine goaf does not exist in the prior art, the application considers that in actual engineering, the stress strain of the pipeline cannot be influenced by goaf mining in an ideal state, and the pipeline may be subjected to sudden change of pipeline mechanical behavior due to local shearing or other behaviors, so that the application takes a pipeline dynamic early warning interval model based on the pipeline mechanical behavior as a main early warning forecast index, takes a goaf surface displacement early warning interval model representing landmark settlement as an auxiliary early warning forecast index, and combines the two indexes to obtain a comprehensive model capable of effectively evaluating the safety level of the oil and gas pipeline in the goaf.
Compared with the prior art, the invention has the following advantages and beneficial effects:
1. the comprehensive safety evaluation method for the buried pipeline in the coal mine goaf, disclosed by the invention, combines the goaf surface subsidence displacement and the dynamic stress of the buried pipeline passing through the goaf, establishes the comprehensive evaluation method suitable for the buried pipeline in the coal mine goaf, fills the blank in the prior art, can comprehensively evaluate the dynamic safety risk of the buried pipeline passing through the coal mine goaf, provides a complete model for actual prediction and early warning, and provides a guidance basis for engineering evaluation.
2. The comprehensive safety evaluation method of the buried pipeline in the coal mine goaf fully considers the effect of the ground surface subsidence displacement of the goaf on the buried oil and gas pipeline, and has practical engineering application value.
3. The comprehensive safety evaluation method for the buried pipeline in the coal mine goaf, provided by the invention, considers the stress condition of the pipeline due to internal pressure, and draws a pipeline dynamic stress curve by taking the combination of the internal pressure and the dynamic stress as the final stress, so that the comprehensive safety evaluation method has more practical engineering application value.
4. The comprehensive safety evaluation method for the buried pipeline in the coal mine goaf considers two conditions of pipe-soil cooperative deformation or pipe-soil non-cooperative deformation of the buried pipeline in the goaf in the process of calculating the bending moment, respectively provides respectively applicable bending moment calculation formulas in a targeted manner, and obviously improves the calculation accuracy and precision of dynamic stress.
5. The invention relates to a comprehensive safety evaluation method for a buried pipeline in a coal mine goaf, which adopts two critical time points with tangent angles equal to 45 degrees in a tangent angle change diagram of a displacement curve as critical points for dividing a goaf surface displacement early warning interval and realizes the division of the goaf surface displacement early warning interval.
6. The comprehensive safety evaluation method for the buried pipeline in the coal mine goaf realizes the division of the dynamic early warning interval of the pipeline by setting and calculating a plurality of critical time points.
7. The invention relates to a comprehensive safety evaluation method for a buried pipeline in a coal mine goaf, which is characterized in that a pipeline dynamic early warning interval model based on pipeline mechanical behavior is used as a main early warning and forecasting index, a goaf surface displacement early warning interval model representing landmark sedimentation is used as an auxiliary early warning and forecasting index, and the two are combined to obtain a comprehensive model capable of effectively evaluating the safety level of an oil and gas pipeline in the goaf.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:
FIG. 1 is a schematic flow chart of an embodiment of the present invention;
FIG. 2 is a plot of surface subsidence displacement in an embodiment of the present invention;
FIG. 3 is a graph of the variation of the tangent angle of the displacement curve in an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention. In the description of the present application, it is to be understood that the terms "front", "back", "left", "right", "upper", "lower", "vertical", "horizontal", "high", "low", "inner", "outer", etc. indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus should not be construed as limiting the scope of the present application.
Example 1:
the comprehensive safety evaluation method for the buried pipeline in the coal mine goaf shown in the figure 1 comprises the following steps:
acquiring a ground surface subsidence displacement curve of the goaf; dividing a goaf surface displacement early warning interval according to the surface subsidence displacement curve;
acquiring a pipeline dynamic stress curve, and dividing a pipeline dynamic early warning interval;
and comprehensively evaluating the buried pipeline in the goaf to obtain a comprehensive evaluation grade by combining the displacement early warning interval of the surface of the goaf and the dynamic early warning interval of the pipeline.
The method for acquiring the ground surface subsidence displacement curve of the goaf comprises the following steps:
setting a calculation point, and calculating the maximum subsidence value of the ground surface of the goaf; the present embodiment preferably sets the calculation point at the maximum displacement of the pipe.
And obtaining a dynamic subsidence equation based on the segmented Knothe time function, and drawing a surface subsidence displacement curve according to the dynamic subsidence equation.
The segment knohe time function in this example is expressed as:
in the formula (I), the compound is shown in the specification,Ф(t) Represents the Knothe time function;Ф 1 (t)、Ф 2 (t) As a function of segmented Knothe time;tis time;cis a time coefficient;τthe time when the maximum sinking speed occurs at the surface point is taken as the reference point;Tis the total sinking time;eis a natural logarithm.
Wherein, the maximum subsidence value of the goaf earth surface is calculated by the following formula:W m =hqcosψ；
in the formula (I), the compound is shown in the specification,W m is the maximum sinking value;his the thickness of the coal bed;qis the sinking coefficient;ψis the coal seam dip angle;
the dynamic dip equation is expressed as:
in the formula (I), the compound is shown in the specification,W(t) Is the maximum sinking point dynamic sinking value;tis time;cis a time coefficient;τthe time when the maximum sinking speed appears at the surface point;Tis the total sinking duration;Ф 1 (t)、Ф 2 (t) As a function of segmented Knothe time;eis a natural logarithm.
The method for acquiring the dynamic stress curve of the pipeline comprises the following steps:
setting a calculation point, and calculating the maximum subsidence value of the ground surface of the goaf;
calculating the radius of influence of the goaf on the coal seam, and taking the edge of the radius of influence as a sinking initial point of pipeline deformation;
calculating the bending moment of the pipeline at the sinking initial point;
calculating the dynamic stress of the pipeline according to the maximum sinking value, the influence radius and the bending moment of the pipeline at the sinking initial pointσ 1 ；
Calculating stress of pipeline due to internal pressureσ 0 ；
Calculating the ultimate stress of the pipeσ：σ=σ 1 +σ 0 ；
Ultimate stressσAnd drawing a dynamic stress curve of the pipeline.
Wherein, the maximum sinking value of the ground surface of the goaf is communicatedCalculated by the following formula:W m =hqcosψ；
in the formula (I), the compound is shown in the specification,W m is the maximum sinking value;his the thickness of the coal bed;qis the sinking coefficient;ψis the coal seam dip angle;
the influence radius is calculated by the following formula:r=H/tanα(ii) a In the formula (I), the compound is shown in the specification,rin order to influence the radius of the film,Hthe mining depth of the coal bed is determined,αto mine the angle of influence;
if the buried pipeline belongs to pipe-soil cooperative deformation in the goaf, the bending moment of the pipeline at the sinking initial point is calculated by the following formula:
in the formula (I), the compound is shown in the specification,M A the bending moment of the pipeline at the sinking starting point,W(l 1 ,γ) Is the sinking value of the maximum sinking point of the pipeline,Lfor the distance of the convergence starting point to the calculation point,EIin order to be able to provide the bending stiffness of the pipe,λis a coefficient, and
，kis the elastic foundation coefficient;
if the buried pipeline belongs to pipe-soil non-cooperative deformation in the goaf, the bending moment of the pipeline at the sinking initial point is calculated by the following formula:
in the formula (I), the compound is shown in the specification,M A the bending moment of the pipeline at the sinking starting point,EIin order to provide the bending stiffness of the pipe,y D is the sinking value of the tail end of the dark suspension area,x D the distance from the sinking starting point to the tail end of the dark suspended area,iis the ground surface gradient corresponding to the tail end of the dark suspension area,λto set the coefficient, and
，kis the elastic foundation coefficient;
stress on pipes due to internal pressureσ 0 Calculated by the following formula:σ 0 =PD/2S(ii) a In the formula (I), the compound is shown in the specification,Pin order to obtain the internal pressure of the pipeline,Dis the outer diameter of the pipeline,Sis the wall thickness of the pipe.
Example 2:
a comprehensive safety evaluation method for buried pipelines in a coal mine goaf is disclosed in the embodiment 1:
firstly, dividing a goaf surface displacement early warning interval:
drawing a tangent angle change diagram of the displacement curve according to the surface subsidence displacement curve;
finding out two critical time points with the tangent angle equal to 45 degrees in the tangent angle change diagram of the displacement curve, and recording the two critical time points asT 1 、T 2 WhereinT 1 ＜T 2 ；
Dividing a goaf surface displacement early warning interval:
if the time t satisfies t <T 1 Then dividing into primary early warning;
if the time t is satisfiedT 1 ≤t＜T 2 If so, classifying the early warning into a middle early warning;
if the time t is satisfiedT 2 And if t is less than or equal to t, high-grade early warning is divided.
Secondly, dividing a pipeline dynamic early warning interval:
if the time t satisfies t < (R) >T 1 Then, dividing into first-level early warning;
if the time t is satisfiedT 1 ≤t＜T 3 If so, dividing into two-stage early warning;
if the time t is satisfiedT 3 ≤t＜T 4 If so, dividing into three levels of early warning;
if the time t is satisfiedT 4 If t is less than or equal to t, dividing the early warning into four levels;
wherein the content of the first and second substances,T 3 is a critical time point of three-level early warning,T 4 All are four-stage early warning critical time points; and the risk levels of the first-level early warning, the second-level early warning, the third-level early warning and the fourth-level early warning are sequentially increased.
Wherein, the calculation is performed by the following formulaT 4 ：
In the formula (I), the compound is shown in the specification,Dis the outer diameter of the pipeline,M A the bending moment of the pipeline at the sinking starting point,Iin order to obtain the moment of inertia of the pipeline,Lfor the distance of the convergence starting point to the calculation point,λto set the coefficient, and
，kis the elastic foundation coefficient;Ф(T 4 ) Is taken for an independent variableT 4 The knohe time function of time;σ flexion type Is the pipeline yield stress;
is calculated by the following formulaT 3 ：T 3 = T 4 -T'; wherein T' is the total time required for pipeline maintenance.
The total time required for pipeline maintenance is calculated by the following formula: t' = T 1 + t 2 + t 3 (ii) a Wherein t is 1 For the Emergency mobilization duration, t 2 The time required for personnel to go out and arrive at the disaster site, t 3 The time is long for starting the maintenance till the completion.
And (III) finally, comprehensively evaluating the buried pipeline in the goaf:
if the pipeline dynamic early warning interval belongs to four-level early warning, the comprehensive evaluation grade is a catastrophe grade;
if the dynamic early warning interval of the pipeline belongs to three levels of early warning, the comprehensive evaluation level is an alarm level;
if the pipeline dynamic early warning interval belongs to the second-level early warning, the comprehensive evaluation level is the warning level;
if the pipeline dynamic early warning interval belongs to primary early warning and the goaf surface displacement early warning interval is primary early warning, the comprehensive evaluation grade is attention grade;
and if the pipeline dynamic early warning interval belongs to a first-level early warning and the goaf surface displacement early warning interval is a middle-level early warning or a high-level early warning, the comprehensive evaluation grade is a warning grade.
In this embodiment, a coal mine gob is taken as an example for calculation and evaluation.
The oil gas pipeline penetrating through the coal mine goaf is an X80 pipe with the outer diameter of 1024mm, the wall thickness of 18mm and the designed internal pressure of 10MPa. The inclination angle of a working face for coal mining is 4-6 degrees, the mining trend size is 571m, the width is 164m, the average mining depth is 260m, and the average mining thickness is 7.5m. Fully-mechanized top coal caving mining is adopted, and a top plate management method is a total caving method. The mining subsidence influence propagation angle is 86.2 degrees, the main influence angle tangent value in the strike direction is 1.9, the main influence angle tangent value in the inclined direction is 2.1 on average, the subsidence coefficient is 0.79, and the horizontal movement coefficient is 0.35. The observation station is provided with 29 point positions along the mining strike direction.
Calculating the maximum subsidence value of the ground surface of the goaf to be-5.925 m; moment of bending of the sinking originM A Is-8272.2 Nm;c=0.037; total length of subsidenceT=364d；τ=0.5T=182d；r=136.84m；L=422.34m；k=4500N/m 3 ；E=2.1×10 11 pa；I=0.0037m 4 ；λ=0.0347；σ 0 =284.4MPa。
Dynamic stress of pipeσ 1 Comprises the following steps:
the surface dynamic subsidence equation is:
the surface subsidence displacement curve is plotted according to the surface dynamic subsidence equation, as shown in fig. 2.
Ultimate stress formula through pipeσ=σ 1 +σ 0 And drawing a dynamic stress curve of the pipeline.
The change of tangent angle of the displacement curve is plotted according to FIG. 2, and as shown in FIG. 3, it can be foundT 1 =74d、T 2 =301d。
According to the emergency repair mobilization time and the emergency mobilization time t of the oil and gas delivery company corresponding to the pipeline 1 =1d, the time t required for personnel to get out and arrive at a disaster site 2 =2d, maintaining the start-up till the completion of the operation for a time period t 3 =7d, so the total time length required for pipeline maintenance is T'=10d。
And the yield stress of the oil and gas pipeline passing through the goaf is 550MPa, and the time for reaching the yield time point is 249d according to a pipeline dynamic stress curve. Calculating to obtain T 4 =202d，T 3 =192d。
Through the above calculation, the comprehensive evaluation model of the present embodiment can be obtained:
the above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Further, the term "connected" used herein may be directly connected or indirectly connected via other components without being particularly described.
Claims (5)
1. A comprehensive safety evaluation method for buried pipelines in a coal mine goaf is characterized by comprising the following steps:
acquiring a ground surface sinking displacement curve of the goaf; dividing a goaf surface displacement early warning interval according to the surface subsidence displacement curve;
acquiring a dynamic stress curve of the pipeline, and dividing a dynamic early warning interval of the pipeline;
comprehensively evaluating the buried pipeline in the goaf by combining the early warning interval of the displacement of the earth surface of the goaf and the dynamic early warning interval of the pipeline to obtain a comprehensive evaluation grade;
the method for dividing the goaf surface displacement early warning interval comprises the following steps:
drawing a tangent angle change diagram of the displacement curve according to the surface subsidence displacement curve;
finding out two critical time points with the tangent angle equal to 45 degrees in the tangent angle change diagram of the displacement curve, and recording the two critical time points as T 1 、T 2 Wherein T is 1 ＜T 2 ；
Dividing a goaf surface displacement early warning interval:
if the time T satisfies T < T 1 Then dividing into primary early warning;
if the time T satisfies T 1 ≤t＜T 2 Then dividing the early warning into middle early warning;
if the time T satisfies T 2 If t is less than or equal to t, high-grade early warning is divided;
the method for dividing the dynamic early warning interval of the pipeline comprises the following steps:
if the time T satisfies T < T 1 Then, dividing into first-level early warning;
if the time T satisfies T 1 ≤t＜T 3 Dividing the early warning into two levels;
if time T satisfies T 3 ≤t＜T 4 If so, dividing into three levels of early warning;
if the time T satisfies T 4 If t is less than or equal to t, four-level early warning is divided;
wherein, T 3 Critical time point T of three-level early warning 4 All are four-stage early warning critical time points; the risk levels of the first-stage early warning, the second-stage early warning, the third-stage early warning and the fourth-stage early warning are sequentially increased;
t is calculated by the following formula 4 ：
Wherein D is the outer diameter of the pipe, M A Is the bending moment of the pipeline at the sinking initial point, I is the inertia moment of the pipeline, L is the distance from the sinking initial point to the calculation point, lambda is a set coefficient, and
k is the elastic foundation coefficient; phi (T) 4 ) Taking T for an argument 4 A Knothe time function of time; sigma Flexion type Is the pipeline yield stress; EI is the bending stiffness of the pipe;
t is calculated by the following formula 3 ：T 3 ＝T 4 -T'; in the formula, T' is the total time required by pipeline maintenance;
the total time required for maintaining the pipeline is calculated by the following formula: t' = T 1 +t 2 +t 3 (ii) a Wherein t is 1 For emergency mobilization duration, t 2 The time required for personnel to go out and arrive at the disaster site, t 3 The time for starting up the maintenance till the completion is long;
the method for comprehensively evaluating the buried pipeline in the goaf comprises the following steps:
if the pipeline dynamic early warning interval belongs to four-level early warning, the comprehensive evaluation grade is a catastrophe grade;
if the dynamic early warning interval of the pipeline belongs to three levels of early warning, the comprehensive evaluation level is an alarm level;
if the pipeline dynamic early warning interval belongs to the second-level early warning, the comprehensive evaluation level is the warning level;
if the pipeline dynamic early warning interval belongs to primary early warning and the goaf surface displacement early warning interval is primary early warning, the comprehensive evaluation grade is attention grade;
and if the pipeline dynamic early warning interval belongs to a first-level early warning and the goaf surface displacement early warning interval is a middle-level early warning or a high-level early warning, the comprehensive evaluation grade is a warning grade.
2. The comprehensive safety evaluation method for the buried pipeline in the coal mine goaf according to claim 1, characterized in that the method for obtaining the surface subsidence displacement curve of the goaf comprises the following steps:
setting a calculation point, and calculating the maximum subsidence value of the ground surface of the goaf;
and obtaining a dynamic subsidence equation based on the segmented Knothe time function, and drawing a surface subsidence displacement curve according to the dynamic subsidence equation.
3. The comprehensive safety evaluation method for the buried pipeline in the coal mine goaf according to claim 2, characterized in that the maximum subsidence value of the ground surface of the goaf is calculated by the following formula:
W m = hqcos ψ; in the formula, W m Is the maximum sinking value; h is the thickness of the coal bed; q is a sinking coefficient; psi is the coal seam dip angle;
the dynamic subsidence equation is:
in the formula, W (t) is the dynamic sinking value of the maximum sinking point; t is time; c is a time coefficient; tau is the moment when the maximum sinking speed occurs at the surface point; t is total sinking duration; phi ( 1 (t)、Ф 2 (t) is a piecewise Knothe time function; e is the natural logarithm.
4. The comprehensive safety evaluation method for the buried pipeline in the coal mine goaf according to claim 1, characterized in that the method for obtaining the dynamic stress curve of the pipeline comprises the following steps:
setting a calculation point, and calculating the maximum subsidence value of the ground surface of the goaf;
calculating the radius of influence of the goaf on the coal seam, and taking the edge of the radius of influence as a sinking initial point of pipeline deformation;
calculating the bending moment of the pipeline at the sinking initial point;
calculating the dynamic stress sigma of the pipeline according to the maximum sinking value, the influence radius and the bending moment of the pipeline at the sinking initial point 1 ；
Calculating stress sigma of pipeline caused by internal pressure 0 ；
Calculating the final stress σ of the pipe: σ = σ 1 +σ 0 ；
And drawing a dynamic stress curve of the pipeline according to the final stress sigma.
5. The comprehensive safety evaluation method for the buried pipeline in the coal mine goaf according to claim 4,
the maximum subsidence value of the ground surface of the goaf is calculated by the following formula: w m = hqcos ψ; in the formula, W m Is the maximum sinking value; h is the thickness of the coal bed; q is a sinking coefficient; psi is the coal seam dip angle;
the influence radius is calculated by the following formula: r = H/tan α; in the formula, r is an influence radius, H is the coal seam mining depth, and alpha is a mining influence angle;
if the buried pipeline belongs to pipe-soil cooperative deformation in the goaf, the bending moment of the pipeline at the sinking initial point is calculated by the following formula:
in the formula, M A Bending moment of the pipe at the beginning of sinking, W (l) 1 Gamma) is the sinking value of the maximum sinking point of the pipeline, L is the distance from the sinking starting point of the pipeline to the calculation point, EI is the bending rigidity of the pipeline, lambda is a set coefficient, and
k is the elastic foundation coefficient;
if the buried pipeline belongs to pipe-soil non-cooperative deformation in the goaf, the bending moment of the pipeline at the sinking initial point is calculated by the following formula:
in the formula, M A The bending moment of the pipe at the beginning of sinking, EI is the bending rigidity of the pipe, y D Is the sinking value, x, of the tail end of the dark suspension area D Is the distance from the sinking initial point to the tail end of the dark suspension area, i is the earth surface gradient corresponding to the tail end of the dark suspension area, lambda is a set coefficient, and
k is the elastic foundation coefficient;
stress sigma of pipe due to internal pressure 0 Calculated by the following formula: sigma 0 = PD/2S; wherein P is the inner pressure of the pipeline, D is the outer diameter of the pipeline, and S is the wall thickness of the pipeline.
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| CN114218518A (en) * | 2021-12-16 | 2022-03-22 | 河南省地质矿产勘查开发局第二地质环境调查院 | Method for measuring and calculating sedimentation amount of coal mine goaf |
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| CN102345796B (en) * | 2010-07-28 | 2013-02-13 | 中国石油天然气股份有限公司 | Method for monitoring oil-gas pipeline in mining subsidence area |
| CN111156425B (en) * | 2020-01-15 | 2021-04-20 | 中国石油化工股份有限公司 | Pipeline state monitoring method, device and system |
| CN113435636A (en) * | 2021-06-18 | 2021-09-24 | 华北水利水电大学 | Dynamic prediction method for coal mining subsidence earth surface point subsidence process |
| CN113670208B (en) * | 2021-08-05 | 2023-10-27 | 国家石油天然气管网集团有限公司 | Oil gas pipeline displacement monitoring system in mining subsidence area |
| CN113792429B (en) * | 2021-09-14 | 2024-05-03 | 国家石油天然气管网集团有限公司 | Method for predicting dynamic stress strain of buried pipeline in goaf by using time function |
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| CN114218518A (en) * | 2021-12-16 | 2022-03-22 | 河南省地质矿产勘查开发局第二地质环境调查院 | Method for measuring and calculating sedimentation amount of coal mine goaf |
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