CN115288213A - Method for predicting stability of offshore steel cylinder - Google Patents

Method for predicting stability of offshore steel cylinder Download PDF

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Publication number
CN115288213A
CN115288213A CN202210822498.4A CN202210822498A CN115288213A CN 115288213 A CN115288213 A CN 115288213A CN 202210822498 A CN202210822498 A CN 202210822498A CN 115288213 A CN115288213 A CN 115288213A
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soil
steel cylinder
pressure
calculating
soil layer
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CN115288213B (en
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于长一
潘伟
李一勇
张乃受
曹永华
刘爱民
岳长喜
寇晓强
陈智军
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CCCC First Harbor Engineering Co Ltd
Tianjin Port Engineering Institute Ltd of CCCC Frst Harbor Engineering Co Ltd
Tianjin Harbor Engineering Quality Inspection Center Co Ltd
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CCCC First Harbor Engineering Co Ltd
Tianjin Port Engineering Institute Ltd of CCCC Frst Harbor Engineering Co Ltd
Tianjin Harbor Engineering Quality Inspection Center Co Ltd
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    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D33/00—Testing foundations or foundation structures
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D1/00—Investigation of foundation soil in situ
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D21/00—Measuring or testing not otherwise provided for
    • G01D21/02—Measuring two or more variables by means not covered by a single other subclass

Abstract

The invention discloses a method for predicting the stability of a marine steel cylinder, which comprises the steps of supposing that the steel cylinder is inclined towards the sea side at any rotating point, calculating the filling pressure, the external friction force, the internal friction force and the vertical counter force and the horizontal resistance of a foundation bed to the steel cylinder in the steel cylinder, and calculating the anti-inclination moment and the overturning moment under the condition that the steel cylinder is inclined towards the sea side, so as to obtain the safety coefficient of inclination towards the sea side; and then, assuming that the steel cylinder rotates towards the land side under the same rotation point, calculating the safety factor of the steel cylinder inclining towards the land side, comparing the two safety factors, and taking the smaller value of the two safety factors as the safety factor under the rotation point. And then, selecting a new rotation point again, calculating the corresponding safety factor of the new rotation point according to the steps, and taking the minimum safety factor value of all the rotation points as the final safety factor under the working condition.

Description

Method for predicting stability of offshore steel cylinder
Technical Field
The invention belongs to the technical field of calculation of stability of an offshore steel cylinder, and particularly relates to a method for predicting the stability of an offshore steel cylinder.
Background
The plug-in cylinder structure is used as a novel marine structure, has the advantages of low manufacturing cost, short construction period, strong stability and the like, and is widely applied to engineering practice of artificial island construction. However, in the application, several pouring failures occur, and the stability design calculation method is still imperfect.
The patent application with the application number of 2022103961255 provides a steel cylinder anti-tilt stability prediction method, which can predict the anti-tilt stability of a steel cylinder at any rotation point. However, the solution of this patent application is only limited to the condition that the steel cylinder soil is cohesionless soil and the land side soil is level with the slope, and thus cannot be applied to the case that the cohesiveness soil and the land side soil have a slope angle.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a method for predicting the stability of an offshore steel cylinder.
The invention is realized by the following technical scheme:
a method for predicting the stability of an offshore steel cylinder comprises the following steps:
step 1, acquiring water level line information, soil layer information and external load data of a steel cylinder embedding environment, wherein the soil layer information comprises: thickness hi and density Y of soil layer i Cohesion force C i Angle of friction
Figure BDA0003745072960000011
Coefficient of friction delta between soil and steel cylinder i ；
Step 2: assuming that the steel cylinder is tilted to the sea side, let the coordinate of the rotation point O at which the steel cylinder is tilted be (R) xi ，R yi ) Then the soil outside the Liu Cegang cylinder above the rotation point O and the soil outside the sea side steel cylinder below the rotation point O are active soil pressures Pa1 and Pa2, and the soil outside the Liu Cegang cylinder below the rotation point O and the soil outside the sea side steel cylinder above the rotation point O are passive soil pressures Pp1 and Pp2;
under the condition that the soil buried in the steel cylinder is any soil body and the slope angle of the land side soil filling is any value, calculating the active soil pressure and the passive soil pressure outside the steel cylinder by adopting a Coulomb theory or a Muller-Breslau theory;
and step 3: calculating the filling pressure inside the steel cylinder
3.1: the interior of the steel cylinder is divided into three sections from top to top, which are respectively as follows: an AB segment, a BC segment and a CD segment,
height of the AB section:
Figure BDA0003745072960000021
height of CD segment:
Figure BDA0003745072960000022
height of BC section: h is 2 ＝H-h 1 -h 3
Wherein the content of the first and second substances,
Figure BDA0003745072960000023
the friction angle of the filler in the steel cylinder; delta is the friction angle between the steel cylinder and the filler; d 0 Is the diameter of the steel cylinder;
3.2: and (3) calculating the filling pressure of the AB section:
vertical pressure sigma of filler in steel cylinder y Comprises the following steps: sigma y ＝Y Am+q 0 e -h/A
Figure BDA0003745072960000024
K＝λ 0 tan(δ)
Wherein Y is the volume weight (kN/m) of the filler in the steel cylinder 3 )；m＝1-e -y/A Y is the calculated depth (m), e is the natural logarithm, q 0 Is an external load, a is a parameter to be determined;
Figure BDA0003745072960000025
λ 0 is the packing side thrust coefficient;
the horizontal pressure sigma of the filler to the inner wall of the AB section of the steel cylinder x Comprises the following steps: sigma x ＝λ 0 σ y ；
3.3: and (3) calculating the packing pressure of the BC section:
the packing pressure of the BC section is considered as equal strength, so the formula sigma in step 3.2 is adopted x ＝λ 0 σ y Calculating the filling pressure sigma at the point B Bx The packing pressure at other positions of the BC section and the packing pressure sigma at the point B Bx Equal;
3.4: calculation of packing pressure in the CD section:
calculating the filling pressure intensity at the point C and the point D to obtain a linear relation of the filling pressure intensity of the CD section along with the depth change, wherein:
packing pressure σ at point C Cx = packing pressure σ at point B Bx ；
The packing pressure at point D was calculated using the following formula: sigma Dx ＝λ 0 (σ mid -σ x ) Wherein σ is mid Is the average pressure at the bottom of the steel cylinder;
and 4, step 4: respectively calculating the external friction force t2 and the internal friction force t1 of the steel cylinder under the condition that the steel cylinder falls to the sea side;
4.1: calculating the friction force of a soil layer on the outer part of the steel cylinder:
frictional force E between soil layer i and outside of steel cylinder yi ＝tan(δ i )·E axi Or E yi ＝tan(δ i )·E pxi ；
The above formula depends on whether the soil layer i participates in the active soil pressure calculation or the passive soil pressure calculation, and when the soil layer i participates in the active soil pressure, E yi ＝tan(δ i )·E axi ，E axi The active soil pressure resultant force of the soil layer i is obtained; when the soil layer i participates in the passive soil pressure, E yi ＝tan(δ i )·E pxi ，E pxi The resultant force of the passive soil pressure of the soil layer i is obtained;
4.2: calculating the friction force of the filler received inside the steel cylinder:
friction force E of AB section in steel cylinder yt1AB ＝tan(δ)·σ Bx ·h 1 ·0.5
Frictional force E borne by BC section in steel cylinder yt1BC ＝tan(δ)·σ Cx ·h 2
Friction force E experienced by the CD section inside the steel cylinder yt1CD ＝tan(δ)·(σ Cx +σ Dx )·h 3 ·0.5；
And 5: respectively calculating the vertical counter force and the horizontal resistance of the foundation bed to the steel cylinder under the condition that the steel cylinder falls to the sea side;
step 6: calculating the anti-tilting moment M under the condition that the steel cylinder tilts towards the sea side r And an overturning moment M s ；
The active soil pressure outside the steel cylinder provides overturning moment; the passive soil pressure, the vertical counter force of the foundation bed to the steel cylinder, the horizontal counter force of the foundation bed to the steel cylinder, the internal friction force of the steel cylinder and the external friction force of the steel cylinder provide an anti-tilting moment, and the external load provides the anti-tilting moment or the overturning moment according to the calculation of the moment direction;
and 7: calculating the safety factor Kl of the steel cylinder toppling towards the sea side,
Figure BDA0003745072960000031
and 8: at the same rotation point O, assuming that the steel cylinder rotates to the land side, the soil outside the sea-side steel cylinder above the rotation point O and the soil outside the sea-land steel cylinder below the rotation point O are active soil pressures, and the soil outside the sea-side steel cylinder below the rotation point O and the soil outside the Liu Cegang cylinder above the rotation point O are passive soil pressures; recalculating the active soil pressure and the passive soil pressure outside the steel cylinder, the vertical counter force of the foundation bed to the steel cylinder, the horizontal resistance of the foundation bed to the steel cylinder, the internal friction of the steel cylinder and the external friction of the steel cylinder under the condition that the steel cylinder rotates towards the land side according to the method; calculating the anti-tipping moment and the tipping moment under the condition that the steel cylinder tips towards the land side, and calculating the safety coefficient Kr of the steel cylinder tip towards the land side;
and step 9: comparing Kl and Kr, and taking the smaller value as the safety factor F at the rotation point i ；
Step 10: re-selecting a new rotation point, calculating the corresponding safety factor of the new rotation point according to the steps, and taking the minimum safety factor value of all the rotation points as the final safety factor F under the working condition min 。
In the above technical scheme, in step 2, under the condition that the soil buried in the steel cylinder is any soil body and the slope angle of the land side soil filling is any value, the Coulomb theory is adopted to calculate the active soil pressure and the passive soil pressure outside the steel cylinder. The method comprises the following specific steps:
2.1: calculating active soil pressure
Figure BDA0003745072960000041
Figure BDA0003745072960000042
Figure BDA0003745072960000043
Figure BDA0003745072960000044
Wherein, C i Cohesion of the soil layer i;
Figure BDA0003745072960000045
the friction angle of the soil layer i; delta is the friction angle between the steel cylinder and the soil; beta is the slope angle of the slope; h is i Is the thickness of the soil layer i, gamma i The soil layer i is the volume weight of the soil layer i, the soil above the water line adopts natural volume weight, and the floating volume weight is adopted below the water line; k axi The active soil pressure coefficient of the soil layer i is obtained; e.g. of the type axi1 The top active soil pressure of a soil layer i; e.g. of a cylinder axi2 The active soil pressure at the bottom of the soil layer i; e axi The active soil pressure resultant force of the soil layer i is obtained; the active soil pressure Pa1 is equal to the resultant force E of the active soil pressures of all the soil layers i outside the Liu Cegang cylinder above the rotation point O axi The sum of the active soil pressure Pa2 is equal to the resultant active soil pressure E of all soil layers i outside the sea side steel cylinder below the rotation point O axi Summing;
2.2: calculating passive earth pressure
Figure BDA0003745072960000046
Figure BDA0003745072960000047
Figure BDA0003745072960000048
Figure BDA0003745072960000049
Wherein, K pxi The passive soil pressure coefficient of the soil layer i is obtained; e.g. of the type pxi1 The top of the soil layer i is driven by the soil pressure; e.g. of the type pxi2 The bottom of the soil layer i is driven by the soil pressure; e pxi The resultant force of the passive soil pressure of the soil layer i is obtained; the passive soil pressure Pp1 is equal to the resultant force E of the passive soil pressures of all soil layers i outside the Liu Cegang cylinder below the rotation point O pxi In sum, the passive soil pressure Pp2 is equal to the resultant passive soil pressure force E of all soil layers i outside the sea side steel cylinder above the rotation point O pxi And (4) summing.
In the above technical solution, in the step 2, under the condition that the soil buried in the steel cylinder is any soil body and the slope angle of the land side filling is any value, the active soil pressure and the passive soil pressure outside the steel cylinder are calculated by using muller-Breslau theory, including the following steps:
2.1 calculate active Earth pressure
Figure BDA00037450729600000410
Figure BDA0003745072960000051
Figure BDA0003745072960000052
Figure BDA0003745072960000053
Figure BDA0003745072960000054
Wherein C is i Cohesive force of a soil layer i;
Figure BDA0003745072960000055
the friction angle of the soil layer i; delta is steel cylinder and soilThe angle of friction of; beta is the slope angle of the slope; h is i Is the thickness of the soil layer i, gamma i The unit weight of soil layer i, the natural unit weight of soil above water level line, the floating unit weight of soil below water level line, and K axi The active soil pressure coefficient caused by the self weight of the soil layer i; k acxi The active soil pressure coefficient caused by soil layer cohesive force; e.g. of the type axi1 The top of the soil layer i is used for driving the soil pressure; e.g. of the type axi2 The active soil pressure at the bottom of the soil layer i; e axi The active soil pressure resultant force of the soil layer i is obtained;
2.2 calculating the Passive Earth pressure
Figure BDA0003745072960000056
Figure BDA0003745072960000057
Figure BDA0003745072960000058
Figure BDA0003745072960000059
Wherein K is pxi The passive soil pressure coefficient of the soil layer i is obtained; e.g. of the type pxi1 The top of the soil layer i is driven by the soil pressure; e.g. of the type pxi2 The bottom of the soil layer i is driven by the soil pressure; e pxi The resultant force of the passive soil pressure of the soil layer i is obtained.
In the above technical solution, in step 3.2, in order to simplify the calculation, the change of the packing pressure in the AB segment is regarded as a linear change, and then the change is calculated according to the formula σ x ＝λ 0 σ y Calculating the filling pressure sigma at the point B Bx The packing pressure at point a is set to 0.
In the above technical solution, step 5 includes:
5.1: vertical counter-force of bed to steel cylinder
Erecting bed on steel cylinderAverage pressure to counter force of q =9 · C u Wherein, C u The non-drainage shear strength of the foundation soil body is defined as that the vertical counter-force of the foundation bed to the steel cylinder is F q ＝q*L q ，L q Is the distance L between the rotation point and the inclined side q Calculating according to the coordinate of the rotating point and the diameter of the steel cylinder;
5.2: horizontal resistance of the bed to the steel cylinder
Horizontal resistance of the bed to the steel cylinder F = pi/4. D 0 ·D 0 ·C u 。
The invention has the advantages and beneficial effects that:
the method can predict the anti-inclination stability of the steel cylinder at any rotation point, calculate the safety coefficient corresponding to each rotation point by selecting any rotation point, and take the minimum safety coefficient value of all the rotation points as the final safety coefficient under the working condition.
Drawings
Fig. 1 is a force diagram of a steel cylinder in a limited state of falling to the sea side.
FIG. 2 is a schematic view of the forces applied to the inside and bottom of the steel cylinder.
Fig. 3 is a diagram showing the extreme state of the steel cylinder falling to the land side.
For a person skilled in the art, without inventive effort, other relevant figures can be derived from the above figures.
Detailed Description
In order to make the technical solution of the present invention better understood, the technical solution of the present invention is further described below with reference to specific examples.
Example one
A method for predicting the stability of an offshore steel cylinder, which is shown in the attached drawings and comprises the following steps:
step 1, acquiring water level line information, soil layer information and external load data of a steel cylinder embedding environment, wherein the soil layer information comprises: (1) soil layer geometric data: the thickness hi of the soil layer; (2) soil layer physical data: density Y i Cohesion force C i Angle of friction
Figure BDA0003745072960000063
Coefficient of friction delta between soil and steel cylinder i Wherein i represents the i-th layer soil.
And 2, step: assuming that the steel cylinder is tilted toward the sea side (left side in FIG. 1), the coordinate of the rotation point O at which the steel cylinder is tilted is (R) xi ，R yi ) Then the soil outside the Liu Cegang cylinder above the rotation point O and the soil outside the sea side steel cylinder below the rotation point O are active soil pressures Pa1 and Pa2, and the soil outside the Liu Cegang cylinder below the rotation point O and the soil outside the sea side steel cylinder above the rotation point O are passive soil pressures Pp1 and Pp2.
And under the condition that the soil buried in the steel cylinder is any soil body and the slope angle of the land side soil is any value, calculating the active soil pressure and the passive soil pressure outside the steel cylinder by adopting a Coulomb theory. The method comprises the following specific steps:
2.1: calculating active soil pressure
Figure BDA0003745072960000061
Figure BDA0003745072960000062
Figure BDA0003745072960000071
Figure BDA0003745072960000072
Wherein, C i Cohesive force of a soil layer i;
Figure BDA0003745072960000073
the friction angle of a soil layer i; delta is the friction angle between the steel cylinder and the soil; beta is the slope angle of the slope; h is i Is the thickness of the soil layer i, gamma i The soil above the water line is the natural volume weight of the soil layer iFloating volume weight is adopted below the water line; k axi The active soil pressure coefficient of a soil layer i; e.g. of the type axi1 The top active soil pressure of a soil layer i; e.g. of the type axi2 The active soil pressure at the bottom of the soil layer i; e axi The resultant force of the active soil pressure of the soil layer i is obtained.
The active soil pressure Pa1 is equal to the resultant force E of the active soil pressures of all soil layers i outside the Liu Cegang cylinder above the rotation point O axi The sum of the active soil pressure Pa2 and the total active soil pressure E of all soil layers i outside the sea side steel cylinder below the rotation point O axi And (4) summing.
2.2: calculating passive earth pressure
Figure BDA0003745072960000074
Figure BDA0003745072960000075
Figure BDA0003745072960000076
Figure BDA0003745072960000077
Wherein, K pxi The passive soil pressure coefficient of the soil layer i is obtained; e.g. of the type pxi1 The top of the soil layer i is driven by the soil pressure; e.g. of the type pxi2 The bottom of the soil layer i is driven by the soil pressure; e pxi The passive soil pressure resultant force of the soil layer i is obtained.
The passive soil pressure Pp1 is equal to the resultant force E of the passive soil pressures of all soil layers i outside the Liu Cegang cylinder below the rotation point O pxi In sum, the passive soil pressure Pp2 is equal to the resultant passive soil pressure force E of all soil layers i outside the sea side steel cylinder above the rotation point O pxi And (4) summing.
And 3, step 3: and calculating the filling pressure inside the steel cylinder.
3.1: the interior of the steel cylinder is divided into three sections from top to top, which are respectively as follows: AB section, BC section and CD section, wherein point A and D are the top and bottom of the steel cylinder respectively.
Height of the AB section:
Figure BDA0003745072960000078
height of CD segment:
Figure BDA0003745072960000079
height of BC section: h is 2 ＝H-h 1 -h 3
Wherein, the first and the second end of the pipe are connected with each other,
Figure BDA00037450729600000710
the friction angle of the filler in the steel cylinder; delta is the friction angle between the steel cylinder and the filler; d 0 The diameter of a steel cylinder.
3.2: and (3) calculating the filling pressure of the AB section:
vertical pressure sigma of filler in steel cylinder y Comprises the following steps: sigma y ＝Y Am+q 0 e -h/A
Figure BDA0003745072960000081
K＝λ 0 tan(δ)
Wherein Y is the volume weight (kN/m) of the filler in the steel cylinder 3 )；m＝1-e -y/A Y is the calculated depth (m), e is the natural logarithm, q 0 Is the external load and a is the undetermined parameter.
Figure BDA0003745072960000082
λ 0 Is the packing side thrust coefficient;
the horizontal pressure sigma of the filler to the inner wall of the AB section of the steel cylinder x Comprises the following steps: sigma x ＝λ 0 σ y . In this embodiment, in order to simplify the calculation, the packing pressure change at the AB segment is regarded as a linear change, and then the packing pressure at the B point is calculatedStrong sigma Bx That is, the packing pressure at point a is set to 0.
3.3: and (3) calculating the packing pressure of the BC section:
the packing pressure of the BC section is considered as equal strength, so the formula in step 3.2, σ, is used x ＝λ 0 σ y Calculating the filling pressure sigma at the point B Bx That is, the packing pressure at other positions of the BC section and the packing pressure sigma at the B point Bx And are equal.
3.4: calculation of packing pressure in the CD section:
the packing pressure of the CD section is linearly changed, namely in the CD section, the ordinate is the depth, the abscissa is the size of the packing pressure, and the two are in a linear relation.
Therefore, the linear relation of the packing pressure of the CD section along with the change of the depth can be obtained by calculating the packing pressure at the point C and the point D (namely, a straight line is determined by the two points). Wherein:
packing pressure σ at point C Cx = packing pressure σ at point B Bx ；
The calculation of the packing pressure at the point D of the cylinder bottom is based on the average pressure sigma mid at the bottom of the steel cylinder, and according to the analysis of the existing experimental data, the packing pressure at the point D is calculated by adopting the following formula: sigma Dx ＝λ 0 (σ mid -σ x ) Wherein σ is mid Is the average pressure at the bottom of the steel cylinder.
And 4, step 4: the outer friction t2 and the inner friction t1 of the steel cylinder in the case where the steel cylinder is tilted to the sea side are calculated, respectively.
4.1: calculating the friction force of a soil layer on the outer part of the steel cylinder:
frictional force E between soil layer i and outside of steel cylinder yi ＝tan(δ i )·E axi Or E yi ＝tan(δ i )·E pxi ；
The above formula depends on whether the soil layer i participates in the active soil pressure calculation or the passive soil pressure calculation, and when the soil layer i participates in the active soil pressure, E yi ＝tan(δ i )·E axi (ii) a When the soil layer i participates in passive soil pressure, E yi ＝tan(δ i )·E pxi 。
4.2: calculating the friction force of the filler received inside the steel cylinder:
friction force E of AB section in steel cylinder yt1AB ＝tan(δ)·σ Bx ·h 1 ·0.5
Frictional force E borne by BC section in steel cylinder yt1BC ＝tan(δ)·σ Cx ·h 2
Friction E against the CD section inside the steel cylinder yt1CD ＝tan(δ)·(σ Cx +σ Dx )·h 3 ·0.5
And 5: and respectively calculating the vertical counter force and the horizontal resistance of the foundation bed to the steel cylinder under the condition that the steel cylinder falls to the sea side.
5.1: vertical counter-force of bed to steel cylinder
The average pressure of the vertical reaction force of the foundation bed to the steel cylinder is q =9 · C u Wherein, C u The non-drainage shear strength of the foundation soil body is obtained, and the vertical counter force of the foundation bed to the steel cylinder is F q ＝q*L q ，L q Is the distance L between the rotation point and the inclined side (sea side) q And calculating according to the coordinates of the rotating point and the diameter of the steel cylinder.
5.2: horizontal resistance of the bed to the steel cylinder
Horizontal resistance of the bed to the steel cylinder F = pi/4. D 0 ·D 0 ·C u
And 6: and calculating the anti-tilting moment and the overturning moment under the condition that the steel cylinder tilts towards the sea side.
The active soil pressures Pa1 and Pa2 outside the steel cylinder provide overturning moment; the passive earth pressures Pp1 and Pp2, the vertical reaction force q of the foundation bed to the steel cylinder, the horizontal resistance F of the foundation bed to the steel cylinder, the internal friction force t1 of the steel cylinder and the external friction force t2 of the steel cylinder provide anti-tilting moments, and the external loads Fx and Fy provide anti-tilting moments or overturning moments according to the calculation of moment directions.
And 7: and calculating the safety coefficient Kl of the steel cylinder toppling towards the sea side.
Figure BDA0003745072960000091
Wherein M is s Overturning moment, M r -a moment of resistance to tilting;
wherein:
Figure BDA0003745072960000092
M s ＝P a1 *|y a1 -R yi |+P a2 *|y a2 -R yi |
P p1 is the resultant force of the pressure of the land side passive soil, y p1 Is P p1 The y-coordinate of (a); p is p2 The resultant force of the passive earth pressure on the sea side, y p2 Is P p2 Y-coordinate of (a); n is the number of soil layers outside the cylinder, x i Is E yi In x coordinate, y F Y-coordinate, P, of the horizontal resistance F of the bed to the steel cylinder a1 Is the resultant force of the active earth pressure on the land side, P a2 For the resultant force of active earth pressure on the sea side, y a1 Is P a1 Y coordinate of (a), y a2 Is P a2 The y-coordinate of (a). In the formula, no external load calculation is added, and if the steel cylinder has an external load effect, the external loads Fx and Fy are calculated according to the moment direction to provide the anti-tilt moment or the overturning moment.
And step 8: referring to fig. 3, at the same rotation point O, assuming that the steel cylinder rotates to the land side, the soil mass outside the sea-side steel cylinder above the rotation point O and the soil mass outside the sea-side steel cylinder below the rotation point O are active soil pressures Pa1 'and Pa2', and the soil mass outside the sea-side steel cylinder below the rotation point O and the soil mass outside the Liu Cegang cylinder above the rotation point O are passive soil pressures Pp1 'and Pp2'.
According to the method, active soil pressures Pa1 'and Pa2', passive soil pressures Pp1 'and Pp2', vertical reaction force q 'of the bed to the steel cylinder, horizontal resistance force F' of the bed to the steel cylinder, internal friction force t1 'of the steel cylinder and external friction force t2' of the steel cylinder under the condition that the steel cylinder rotates towards the land side are calculated again.
And step 9: and calculating the anti-tipping moment and the tipping moment under the condition that the steel cylinder tips towards the land side. It should be noted that no matter which side the steel cylinder inclines to, the active earth pressure outside the steel cylinder provides the overturning moment; the passive soil pressure, the vertical counter force of the bed to the steel cylinder, the horizontal counter force of the bed to the steel cylinder, the internal friction force of the steel cylinder and the external friction force of the steel cylinder provide anti-tilting moment. Therefore, when the steel cylinder is inclined toward the land side, the overturning moment is provided by the active earth pressures Pa1 'and Pa2' outside the steel cylinder in step 8, and the overturning moment is provided by the passive earth pressures Pp1 'and Pp2', the vertical reaction force q 'of the bed to the steel cylinder, the horizontal resistance force F' of the bed to the steel cylinder, the internal friction force t1 'of the steel cylinder, and the external friction force t2' of the steel cylinder.
Step 10: and calculating the safety factor Kr of the steel cylinder toppling towards the land side.
Step 11: the smaller of the two values is taken as a safety factor F at the rotation point O by comparing Kl and Kr i 。
Step 12: re-selecting a new rotation point, calculating the corresponding safety factor of the new rotation point according to the steps, and taking the minimum safety factor value of all the rotation points as the final safety factor F under the working condition min 。
Example two
The difference between the present embodiment and the first embodiment is: step 2 in example one can also calculate the active and passive earth pressure outside the steel cylinder using Muller-Breslau theory, including the following steps:
2.1 calculate active Earth pressure
Figure BDA0003745072960000101
Figure BDA0003745072960000102
Figure BDA0003745072960000111
Figure BDA0003745072960000112
Figure BDA0003745072960000113
Wherein C i Cohesive force of a soil layer i;
Figure BDA0003745072960000114
the friction angle of a soil layer i; delta is the friction angle between the steel cylinder and the soil; beta is the slope angle of the slope; h is i Is the thickness of the soil layer i, gamma i The volume weight of soil layer i, the natural volume weight of soil above water level line, the floating volume weight of soil below water level line, K axi The active soil pressure coefficient caused by the self weight of the soil layer i; k acxi The active soil pressure coefficient caused by soil layer cohesive force; e.g. of the type axi1 The top active soil pressure of a soil layer i; e.g. of the type axi2 The active soil pressure at the bottom of the soil layer i; e axi The resultant force of the active soil pressure of the soil layer i is obtained.
2.2 calculating Passive Earth pressure
Figure BDA0003745072960000115
Figure BDA0003745072960000116
Figure BDA0003745072960000117
Figure BDA0003745072960000118
Wherein K pxi The passive soil pressure coefficient of the soil layer i is obtained; e.g. of a cylinder pxi1 The top of the soil layer i is driven by the soil pressure; e.g. of the type pxi2 The bottom of the soil layer i is driven by the soil pressure;E pxi the passive soil pressure resultant force of the soil layer i is obtained.
The invention has been described in an illustrative manner, and it is to be understood that any simple variations, modifications or other equivalent changes which can be made by one skilled in the art without departing from the spirit of the invention fall within the scope of the invention.

Claims (5)

1. A method for predicting the stability of an offshore steel cylinder is characterized by comprising the following steps:
step 1, acquiring water level line information, soil layer information and external load data of a steel cylinder embedding environment, wherein the soil layer information comprises: thickness hi and density γ of soil layer i Cohesion force C i Angle of friction phi i Coefficient of friction delta between soil and steel cylinder i ；
Step 2: assuming that the steel cylinder is tilted to the sea side, let the coordinate of the rotation point O at which the steel cylinder is tilted be (R) xi ，R yi ) Then the soil outside the Liu Cegang cylinder above the rotation point O and the soil outside the sea side steel cylinder below the rotation point O are active soil pressures Pa1 and Pa2, and the soil outside the Liu Cegang cylinder below the rotation point O and the soil outside the sea side steel cylinder above the rotation point O are passive soil pressures Pp1 and Pp2;
under the condition that the soil buried in the steel cylinder is any soil body and the slope angle of the land side soil filling is any value, calculating the active soil pressure and the passive soil pressure outside the steel cylinder by adopting a Coulomb theory or a Muller-Breslau theory;
and step 3: calculating the filling pressure inside the steel cylinder
3.1: the interior of the steel cylinder is divided into three sections from top to top, which are respectively as follows: an AB segment, a BC segment and a CD segment,
height of the AB section:
Figure FDA0003745072950000011
height of CD segment:
Figure FDA0003745072950000012
height of BC section: h is 2 ＝H-h 1 -h 3
Wherein phi is the friction angle of the filler in the steel cylinder; delta is the friction angle between the steel cylinder and the filler; d 0 Is the diameter of the steel cylinder;
3.2: and (3) calculating the filling pressure of the AB section:
vertical pressure sigma of filler in steel cylinder y Comprises the following steps: sigma y ＝γAm+q 0 e -h/A
Figure FDA0003745072950000013
K＝λ 0 tan(δ)
Wherein γ is the volume weight of the filler in the steel cylinder (kN/m) 3 )；m＝1-e -y/A Y is the calculated depth (m), e is the natural logarithm, q 0 Is an external load, a is a parameter to be determined;
Figure FDA0003745072950000014
λ 0 is the packing side thrust coefficient;
the horizontal pressure sigma of the filler to the inner wall of the AB section of the steel cylinder x Comprises the following steps: sigma x ＝λ 0 σ y ；
3.3: and (3) calculating the packing pressure of the BC section:
the packing pressure of the BC section is considered as equal strength, so the formula sigma in step 3.2 is adopted x ＝λ 0 σ y Calculating the filling pressure sigma at the point B Bx The packing pressure at other positions of the BC section and the packing pressure sigma at the point B Bx Equal;
3.4: calculation of packing pressure in the CD section:
and (3) calculating the filling pressure intensity at the point C and the point D to obtain a linear relation of the filling pressure intensity of the CD section along with the depth change, wherein:
packing pressure σ at point C Cx = packing pressure σ at point B Bx ；
The packing pressure at point D is calculated using the following formula: sigma Dx ＝λ 0 (σ mid -σ x ) Wherein σ is mid Is the average pressure at the bottom of the steel cylinder;
and 4, step 4: respectively calculating the external friction force t2 and the internal friction force t1 of the steel cylinder under the condition that the steel cylinder falls to the sea side;
4.1: calculating the friction force of a soil layer on the outer part of the steel cylinder:
frictional force E between soil layer i and outside of steel cylinder yi ＝tan(δ i )·E axi Or E yi ＝tan(δ i )·E pxi ；
The above formula depends on whether the soil layer i participates in the active soil pressure calculation or the passive soil pressure calculation, and when the soil layer i participates in the active soil pressure, E yi ＝tan(δ i )′E axi ，E axi The active soil pressure resultant force of the soil layer i is obtained; when the soil layer i participates in the passive soil pressure, E yi ＝tan(δ i )·E pxi ，E pxi The resultant force of the passive soil pressure of the soil layer i is obtained;
4.2: calculating the friction force of the filler received inside the steel cylinder:
friction force E experienced by the AB segment inside the steel cylinder yt1AB ＝tan(δ)·σ Bx ·h 1 ·0.5
Frictional force E borne by BC section in steel cylinder yt1BC ＝tan(δ)·σ Cx ·h 2
Friction force E experienced by the CD section inside the steel cylinder yt1CD ＝tan(δ)·(σ Cx +σ Dx )·h 3 ·0.5；
And 5: respectively calculating the vertical counter force and the horizontal resistance of the foundation bed to the steel cylinder under the condition that the steel cylinder falls to the sea side;
step 6: calculating the anti-tilting moment M under the condition that the steel cylinder tilts towards the sea side r And an overturning moment M s ；
The active earth pressure outside the steel cylinder provides the overturning moment; the passive soil pressure, the vertical counter force of the foundation bed to the steel cylinder, the horizontal counter force of the foundation bed to the steel cylinder, the internal friction force of the steel cylinder and the external friction force of the steel cylinder provide an anti-tilting moment, and the external load provides the anti-tilting moment or the overturning moment according to the calculation of the moment direction;
and 7: calculating safety coefficient K of steel cylinder toppling to sea side l ，
Figure FDA0003745072950000021
And 8: at the same rotation point O, assuming that the steel cylinder rotates to the land side, the soil mass outside the sea-side steel cylinder above the rotation point O and the soil mass outside the sea-land steel cylinder below the rotation point O are active soil pressures, and the soil mass outside the sea-side steel cylinder below the rotation point O and the soil mass outside the Liu Cegang cylinder above the rotation point O are passive soil pressures; recalculating the active soil pressure and the passive soil pressure outside the steel cylinder, the vertical counter force of the foundation bed to the steel cylinder, the horizontal resistance of the foundation bed to the steel cylinder, the internal friction of the steel cylinder and the external friction of the steel cylinder under the condition that the steel cylinder rotates towards the land side according to the method; calculating the anti-tipping moment and the tipping moment under the condition that the steel cylinder tips towards the land side, and calculating the safety coefficient K of the steel cylinder tip towards the land side r ；
And step 9: comparison K l And K r The smaller value of the two is taken as the safety factor F at the rotation point i ；
Step 10: re-selecting a new rotation point, calculating the corresponding safety factor of the new rotation point according to the steps, and taking the minimum safety factor value of all the rotation points as the final safety factor F under the working condition min 。
2. The marine steel cylinder stability prediction method of claim 1, characterized in that: in step 2, under the condition that the soil buried in the steel cylinder is any soil body and the slope angle of the land side soil filling is any value, the Coulomb theory is adopted to calculate the active soil pressure and the passive soil pressure outside the steel cylinder, and the steps are as follows:
2.1: calculating active soil pressure
Figure FDA0003745072950000031
Figure FDA0003745072950000032
Figure FDA0003745072950000033
Figure FDA0003745072950000034
Wherein, C i Cohesive force of a soil layer i;
Figure FDA0003745072950000035
the friction angle of a soil layer i; delta is the friction angle between the steel cylinder and the soil; beta is the slope angle of the slope; h is i Is the thickness of the soil layer i, gamma i The volume weight of a soil layer i, the natural volume weight of the soil above the water line, and the floating volume weight of the soil below the water line are adopted; k axi The active soil pressure coefficient of a soil layer i; e.g. of the type axi1 The top active soil pressure of a soil layer i; e.g. of a cylinder axi2 The active soil pressure at the bottom of the soil layer i; e axi The active soil pressure resultant force of the soil layer i is obtained; the active soil pressure Pal is equal to the resultant active soil pressure force E of all soil layers i outside the Liu Cegang cylinder above the rotation point O axi The sum of the active soil pressure Pa2 is equal to the resultant active soil pressure E of all soil layers i outside the sea side steel cylinder below the rotation point O axi Summing;
2.2: calculating passive earth pressure
Figure FDA0003745072950000036
Figure FDA0003745072950000037
Figure FDA0003745072950000038
Figure FDA0003745072950000039
Wherein, K pxi The passive soil pressure coefficient of the soil layer i is obtained; e.g. of the type pxi1 The top of the soil layer i is driven by the soil pressure; e.g. of the type pxi2 The bottom of the soil layer i is driven by the soil pressure; e pxi The resultant force of the passive soil pressure of the soil layer i is obtained; the passive soil pressure Pp1 is equal to the resultant force E of the passive soil pressures of all soil layers i outside the Liu Cegang cylinder below the rotation point O pxi In sum, the passive earth pressure Pp2 is equal to the resultant passive earth pressure E of all earth layers i outside the sea side steel cylinder above the rotation point O pxi And (4) summing.
3. The marine steel cylinder stability prediction method of claim 1, characterized in that: in the step 2, under the condition that the soil buried in the steel cylinder is any soil body and the slope angle of land side filling is any value, the active soil pressure and the passive soil pressure outside the steel cylinder are calculated by adopting Muller-Breslau theory, and the method comprises the following steps:
2.1 calculate active Earth pressure
Figure FDA0003745072950000041
Figure FDA0003745072950000042
Figure FDA0003745072950000043
Figure FDA0003745072950000044
Figure FDA0003745072950000045
Wherein C is i Cohesive force of a soil layer i;
Figure FDA0003745072950000046
the friction angle of a soil layer i; delta is the friction angle between the steel cylinder and the soil; beta is the slope angle of the slope; h is i Is the thickness of the soil layer i, gamma i The volume weight of soil layer i, the natural volume weight of soil above water level line, the floating volume weight of soil below water level line, K axi The active soil pressure coefficient caused by the self weight of the soil layer i; k acxi The active soil pressure coefficient caused by soil layer cohesive force; e.g. of the type axi1 The top active soil pressure of a soil layer i; e.g. of the type axi2 The active soil pressure at the bottom of the soil layer i; e axi The active soil pressure resultant force of the soil layer i is obtained;
2.2 calculating the Passive Earth pressure
Figure FDA0003745072950000047
Figure FDA0003745072950000048
Figure FDA0003745072950000049
Figure FDA00037450729500000410
Wherein K pxi Of soil layer iPassive earth pressure coefficient; e.g. of the type pxi1 The top of the soil layer i is driven by the soil pressure; e.g. of the type pxi2 The bottom of the soil layer i is driven by the soil pressure; e pxi The resultant force of the passive soil pressure of the soil layer i is obtained.
4. The method for predicting stability of an offshore steel cylinder according to claim 1, wherein: in step 3.2, in order to simplify the calculation, the change of the filling pressure in the AB section is regarded as linear change, and then the formula sigma is used x ＝λ 0 σ y Calculating the filling pressure sigma at the point B Bx The packing pressure at point a is set to 0.
5. The marine steel cylinder stability prediction method of claim 1, characterized in that: the step 5 comprises the following steps:
5.1: vertical counter-force of bed to steel cylinder
The average pressure of the vertical reaction force of the foundation bed to the steel cylinder is q =9 · C u Wherein, C u The non-drainage shear strength of the foundation soil body is defined as that the vertical counter-force of the foundation bed to the steel cylinder is F q ＝q*L q ，L q Is the distance L between the rotation point and the inclined side q Calculating according to the coordinate of the rotating point and the diameter of the steel cylinder;
5.2: horizontal resistance of the bed to the steel cylinder
Horizontal resistance of the bed to the steel cylinder F = π/4 · D 0 ·D 0 ·C u 。
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