CN115288213B - Marine steel cylinder stability prediction method - Google Patents
Marine steel cylinder stability prediction method Download PDFInfo
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- CN115288213B CN115288213B CN202210822498.4A CN202210822498A CN115288213B CN 115288213 B CN115288213 B CN 115288213B CN 202210822498 A CN202210822498 A CN 202210822498A CN 115288213 B CN115288213 B CN 115288213B
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 229
- 239000010959 steel Substances 0.000 title claims abstract description 229
- 238000000034 method Methods 0.000 title claims abstract description 26
- 238000012856 packing Methods 0.000 claims abstract description 50
- 239000002689 soil Substances 0.000 claims description 325
- 238000004364 calculation method Methods 0.000 claims description 23
- 239000000945 filler Substances 0.000 claims description 22
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 14
- 239000004927 clay Substances 0.000 claims description 5
- 230000002776 aggregation Effects 0.000 claims description 3
- 238000004220 aggregation Methods 0.000 claims description 3
- 230000000694 effects Effects 0.000 claims description 2
- 238000010276 construction Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
Classifications
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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
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- 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
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- 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 stability of an offshore steel cylinder, which is characterized in that the steel cylinder is assumed to topple towards the sea at any rotation point, the packing pressure, external friction, internal friction, vertical counter force and horizontal resistance of a foundation bed to the steel cylinder in the steel cylinder are calculated, and the anti-toppling moment and the toppling moment of the steel cylinder under the condition of toppling towards the sea are calculated to obtain the safety coefficient of toppling towards the sea; then under the same rotation point, the steel cylinder is assumed to rotate to the land side, the safety coefficient of the steel cylinder tilting to the land side is calculated, the two safety coefficients are compared, and the smaller value of the two safety coefficients is used as the safety coefficient under the rotation point. And then, selecting a new rotation point again, calculating the safety coefficient corresponding to the new rotation point according to the steps, and taking the minimum value of the safety coefficients in all the rotation points as the final safety coefficient under the working condition.
Description
Technical Field
The invention belongs to the technical field of stability calculation of offshore steel cylinders, and particularly relates to a stability prediction method of an offshore steel cylinder.
Background
The inserted cylinder structure is used as a novel marine structure, has the advantages of low cost, short construction period, strong stability and the like, and is widely applied to engineering practice of artificial island construction. However, several pouring failures occur in the application, and the stability design calculation method is still an imperfect place.
The patent application 2022103961255 provides a method for predicting the steel cylinder anti-tilting stability, which can predict the steel cylinder anti-tilting stability at any rotation point. However, the solution of this patent application is only aimed at the condition that the steel cylinder buried soil is non-clay soil and the land side filled soil slope surface is horizontal, so that the solution has a large limitation, and cannot be applied to the condition that the clay buried soil and the land side filled soil have slope angles.
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 stability of an offshore steel cylinder comprises the following steps:
step 1, acquiring water line information, soil layer information and external load data of a steel cylinder embedded environment, wherein the soil layer information comprises: thickness hi, density Y of soil layer i Cohesive force C i Angle of frictionCoefficient of friction delta between soil body and steel cylinder i ；
Step 2: assuming that the steel cylinder is tilted to the sea, the coordinates of the rotation point O at which the steel cylinder is tilted are defined as (R xi ，R yi )，The soil outside the land-side steel 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 land-side steel 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 buried soil of the steel cylinder is any soil body and the land side soil filling slope angle 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;
step 3: calculating the packing pressure inside the steel cylinder
3.1: the inside of the steel cylinder is divided into three sections from top to bottom, namely: an AB segment, a BC segment and a CD segment,
height of AB section:
height of CD segment:
height of BC segment: h is a 2 ＝H-h 1 -h 3
Wherein,the friction angle of the filler in the steel cylinder; delta is the friction angle between the steel cylinder and the filler; d (D) 0 Is the diameter of a steel cylinder;
3.2: calculating the packing pressure of the AB section:
vertical pressure sigma of packing in steel cylinder y The method comprises the following steps: sigma (sigma) y ＝Y Am+q 0 e -h/A
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 natural logarithm, q 0 Is an external load, A is a parameter to be determined;
λ 0 is the side thrust coefficient of the filler;
the horizontal pressure sigma of the filler to the inner wall of the AB section of the steel cylinder x The method comprises the following steps: sigma (sigma) x ＝λ 0 σ y ；
3.3: calculating the packing pressure of the BC segment:
the packing pressure of the BC-stage is considered to be equal, and therefore the formula σ in step 3.2 is used x ＝λ 0 σ y Calculating the packing pressure sigma at the point B Bx Packing pressure elsewhere in BC segment and packing pressure sigma at point B Bx Equal;
3.4: calculation of packing pressure for CD section:
calculating the filler pressure at the point C and the point D to obtain a linear relation of the filler pressure of the CD section along with the depth change, wherein:
packing pressure sigma at point C Cx Packing pressure σ at point =b Bx ；
The packing pressure at point D is calculated using the following formula: sigma (sigma) Dx ＝λ 0 (σ mid -σ x ) Wherein σ is mid Is the average pressure at the bottom of the steel cylinder;
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 is tilted towards the sea;
4.1: calculating the friction force of the soil layer exposed outside the steel cylinder:
friction force E between soil layer i and outside of steel cylinder yi ＝tan(δ i )·E axi Or E is yi ＝tan(δ i )·E pxi ；
The above formula depends on whether soil layer i participates in the calculation of active soil pressure or passive soil pressure, E when soil layer i participates in the calculation of active soil pressure yi ＝tan(δ i )·E axi ，E axi Is the active soil pressure resultant force of soil layer i;e when the soil layer i participates in the passive soil pressure yi ＝tan(δ i )·E pxi ，E pxi Is the resultant force of the passive soil pressure of the soil layer i;
4.2: the friction force of the filler received inside the steel cylinder is calculated:
friction force E applied to AB section inside steel cylinder yt1AB ＝tan(δ)·σ Bx ·h 1 ·0.5
Friction force E applied to BC segment in steel cylinder yt1BC ＝tan(δ)·σ Cx ·h 2
Friction force E applied to CD segment inside steel cylinder yt1CD ＝tan(δ)·(σ Cx +σ Dx )·h 3 ·0.5；
Step 5: respectively calculating the vertical counterforce and the horizontal resistance of the foundation bed to the steel cylinder under the condition that the steel cylinder is tilted to the sea;
step 6: calculating the moment M of resistance to tilting in case of tilting the steel cylinder to sea r And overturning moment M s ；
The active soil pressure outside the steel cylinder provides a overturning moment; the passive soil pressure, the vertical counterforce 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 provide anti-tilting moment, and the external load provides anti-tilting moment or tilting moment according to the moment direction calculation;
step 7: the safety coefficient Kl of the steel cylinder dumping to the sea side is calculated,
step 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 Liu Gang 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 land side steel cylinder above the rotation point O are passive soil pressures; according to the method, the active soil pressure, the passive soil pressure, the vertical counterforce 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 are recalculated under the condition that the steel cylinder rotates to the land side; calculating an anti-tilting moment and a tilting moment under the condition that the steel cylinder tilts to the land side, and calculating a safety coefficient Kr of tilting of the steel cylinder to the land side;
step 9: comparing Kl and Kr, and taking the smaller value of the two as the safety factor F at the rotation point i ；
Step 10: re-selecting a new rotation point, calculating the safety coefficient corresponding to the new rotation point according to the steps, and taking the minimum value of the safety coefficients in all the rotation points as the final safety coefficient F under the working condition min 。
In the above technical scheme, in step 2, under the condition that the buried soil of the steel cylinder is any soil mass and the slope angle of the land side filled soil is any value, the active soil pressure and the passive soil pressure outside the steel cylinder are calculated by adopting the Coulomb theory. The method comprises the following specific steps:
2.1: calculating active earth pressure
Wherein C is i Cohesive force of soil layer i;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 a i For the thickness of soil layer i, gamma i For the volume weight of soil layer i, the soil above the water level adopts natural volume weight and waterFloating volume weight is adopted below the bit line; k (K) axi The active soil pressure coefficient of the soil layer i; e, e axi1 The top active soil pressure of the soil layer i; e, e axi2 The soil pressure is active at the bottom of the soil layer i; e (E) axi The resultant force of the active soil pressure of the soil layer i; the active soil pressure Pa1 is equal to the active soil pressure resultant force E of all soil layers i outside the land-side steel cylinder above the rotation point O axi The sum of which is equal to the active soil pressure resultant force E of all soil layers i outside the sea-side steel cylinder below the rotation point O, the active soil pressure Pa2 axi And (3) summing;
2.2: calculating passive earth pressure
Wherein K is pxi The soil pressure coefficient is the passive soil pressure coefficient of the soil layer i; e, e pxi1 The top passive soil pressure of the soil layer i; e, e pxi2 The bottom passive soil pressure of the soil layer i; e (E) pxi The resultant force of the passive soil pressure of the soil layer i; the passive earth pressure Pp1 is equal to the passive earth pressure resultant force E of all the earth layers i outside the land-side steel cylinder below the rotation point O pxi The sum of the passive soil pressure Pp2 is equal to the resultant force E of the passive soil pressure of all soil layers i outside the sea-side steel cylinder above the rotation point O pxi And (3) summing.
In the above technical solution, in step 2, under the condition that the buried soil of the steel cylinder is any soil body and the slope angle of the land side filled soil is any value, the active soil pressure and the passive soil pressure outside the steel cylinder are calculated by using a Muller-Breslau theory, and the method comprises the following steps:
2.1 calculation of active soil pressure
Wherein C is i Cohesive force of soil layer i;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 a i For the thickness of soil layer i, gamma i For the volume weight of the soil layer i, the soil above the water level adopts the natural volume weight, and the soil below the water level adopts the floating volume weight, K axi The active soil pressure coefficient caused by the dead weight of the soil layer i; k (K) acxi The active soil pressure coefficient is caused by soil layer clay aggregation force; e, e axi1 The top active soil pressure of the soil layer i; e, e axi2 The soil pressure is active at the bottom of the soil layer i; e (E) axi The resultant force of the active soil pressure of the soil layer i;
2.2 calculating the passive soil pressure
Wherein K is pxi The soil pressure coefficient is the passive soil pressure coefficient of the soil layer i; e, e pxi1 The top passive soil pressure of the soil layer i; e, e pxi2 The bottom passive soil pressure of the soil layer i; e (E) pxi Is the resultant force of the passive soil pressure of the soil layer i.
In the above technical solution, in step 3.2, in order to simplify the calculation, the change of the packing pressure of the AB segment is regarded as a linear change, and then the formula σ is used x ＝λ 0 σ y Calculating the packing 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 reaction force of foundation 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 vertical counterforce of the foundation bed to the steel cylinder is F when the shear strength of the foundation soil body is not drained q ＝q*L q ，L q For the distance L between the rotation point and the inclined side q According to the coordinates of the rotation point and the diameter of the steel cylinder, calculating;
5.2: horizontal resistance of foundation bed to 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:
according to the invention, the anti-tilting stability of the steel cylinder under any rotating point can be predicted, the safety coefficient corresponding to each rotating point is calculated by selecting any rotating point, and the minimum value of the safety coefficients in all the rotating points is taken as the final safety coefficient under the working condition.
Drawings
FIG. 1 is a diagram showing the limit of the tilting of a steel cylinder to the sea.
FIG. 2 is a schematic view of the inside and bottom forces of a steel cylinder.
FIG. 3 is a diagram showing the limit of tilting of the steel cylinder to the land side.
Other relevant drawings may be made by those of ordinary skill in the art from the above figures without undue burden.
Detailed Description
In order to make the person skilled in the art better understand the solution of the present invention, the following describes the solution of the present invention with reference to specific embodiments.
Example 1
A method for predicting the stability of an offshore steel cylinder, see the accompanying drawings, comprising the following steps:
step 1, acquiring water line information, soil layer information and external load data of a steel cylinder embedded environment, wherein the soil layer information comprises: (1) soil layer geometry data: the thickness hi of the soil layer; (2) soil layer physical data: density Y i Cohesive force C i Angle of frictionCoefficient of friction delta between soil body and steel cylinder i Wherein i represents the i-th layer of soil.
Step 2: assuming that the steel cylinder is tilted to the sea side (left side in fig. 1), the coordinates of the rotation point O at which the steel cylinder is tilted are set to (R xi ，R yi ) The soil outside the land-side steel 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 land-side steel 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 buried soil of the steel cylinder is any soil body and the land side soil filling slope angle is any value, the active soil pressure and the passive soil pressure outside the steel cylinder are calculated by adopting the Coulomb theory. The method comprises the following specific steps:
2.1: calculating active earth pressure
Wherein C is i Cohesive force of soil layer i;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 a i For the thickness of soil layer i, gamma i The soil above the water level adopts natural volume weight, and the soil below the water level adopts floating volume weight; k (K) axi The active soil pressure coefficient of the soil layer i; e, e axi1 The top active soil pressure of the soil layer i; e, e axi2 The soil pressure is active at the bottom of the soil layer i; e (E) axi Is the active soil pressure resultant force of soil layer i.
The active soil pressure Pa1 is equal to the active soil pressure resultant force E of all soil layers i outside the land-side steel cylinder above the rotation point O axi The sum of which is equal to the active soil pressure resultant force E of all soil layers i outside the sea-side steel cylinder below the rotation point O, the active soil pressure Pa2 axi And (3) summing.
2.2: calculating passive earth pressure
Wherein K is pxi The soil pressure coefficient is the passive soil pressure coefficient of the soil layer i; e, e pxi1 The top passive soil pressure of the soil layer i; e, e pxi2 The bottom passive soil pressure of the soil layer i; e (E) pxi Is the resultant force of the passive soil pressure of the soil layer i.
The passive earth pressure Pp1 is equal to the passive earth pressure resultant force E of all the earth layers i outside the land-side steel cylinder below the rotation point O pxi The sum of the passive soil pressure Pp2 is equal to the resultant force E of the passive soil pressure of all soil layers i outside the sea-side steel cylinder above the rotation point O pxi And (3) summing.
Step 3: the packing pressure inside the steel cylinder was calculated.
3.1: the inside of the steel cylinder is divided into three sections from top to bottom, namely: AB section, BC section and CD section, wherein point A and point D are steel cylinder top and bottom respectively.
Height of AB section:
height of CD segment:
height of BC segment: h is a 2 ＝H-h 1 -h 3
Wherein,the friction angle of the filler in the steel cylinder; delta is the friction angle between the steel cylinder and the filler; d (D) 0 Is the diameter of the steel cylinder.
3.2: calculating the packing pressure of the AB section:
vertical pressure sigma of packing in steel cylinder y The method comprises the following steps: sigma (sigma) y ＝Y Am+q 0 e -h/A
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.
λ 0 Is the side thrust coefficient of the filler;
the horizontal pressure sigma of the filler to the inner wall of the AB section of the steel cylinder x The method comprises the following steps: sigma (sigma) x ＝λ 0 σ y . In the present embodiment, to simplify the calculation, the packing pressure sigma at the point B is calculated by considering the packing pressure variation of the AB segment as a linear variation Bx The packing pressure at point a is set to 0.
3.3: calculating the packing pressure of the BC segment:
the packing pressure of the BC segment is considered to be equal, and therefore, the formula in step 3.2, σ, is used x ＝λ 0 σ y Calculating the packing pressure sigma at the point B Bx Namely, the packing pressure at other positions of the BC segment and the packing pressure sigma at the point B Bx Equal.
3.4: calculation of packing pressure for CD section:
the packing pressure in the CD segment varies linearly, i.e. in the CD segment the ordinate is depth and the abscissa is packing pressure magnitude, both being linear.
Therefore, the linear relation of the packing pressure of the CD section along with the depth change (namely, the two points determine a straight line) can be obtained by calculating the packing pressure at the point C and the point D. Wherein:
packing pressure sigma at point C Cx Packing pressure σ at point =b Bx ；
The calculation of the packing pressure at the bottom D point of the cylinder is based on the mean pressure σmid of the bottom of the steel cylinder, analyzed according to the current experimental data, and calculated using the following formula: sigma (sigma) Dx ＝λ 0 (σ mid -σ x ) Wherein σ is mid Is the average pressure at the bottom of the steel cylinder.
Step 4: the external friction force t2 and the internal friction force t1 of the steel cylinder are calculated respectively in the case of tilting the steel cylinder toward the sea.
4.1: calculating the friction force of the soil layer exposed outside the steel cylinder:
friction force E between soil layer i and outside of steel cylinder yi ＝tan(δ i )·E axi Or E is yi ＝tan(δ i )·E pxi ；
The above formula depends on whether soil layer i participates in the calculation of active soil pressure or passive soil pressure, E when soil layer i participates in the calculation of active soil pressure yi ＝tan(δ i )·E axi The method comprises the steps of carrying out a first treatment on the surface of the E when the soil layer i participates in the passive soil pressure yi ＝tan(δ i )·E pxi 。
4.2: the friction force of the filler received inside the steel cylinder is calculated:
friction force E applied to AB section inside steel cylinder yt1AB ＝tan(δ)·σ Bx ·h 1 ·0.5
Friction force E applied to BC segment in steel cylinder yt1BC ＝tan(δ)·σ Cx ·h 2
Friction force E applied to CD segment inside steel cylinder yt1CD ＝tan(δ)·(σ Cx +σ Dx )·h 3 ·0.5
Step 5: and respectively calculating the vertical counterforce and the horizontal resistance of the foundation bed to the steel cylinder under the condition that the steel cylinder is tilted to the sea.
5.1: vertical reaction force of foundation 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 vertical counterforce of the foundation bed to the steel cylinder is F when the shear strength of the foundation soil body is not drained q ＝q*L q ，L q Is the distance L between the rotation point and the inclined side (sea side) q Calculated according to the coordinates of the rotation point and the diameter of the steel cylinder.
5.2: horizontal resistance of foundation bed to steel cylinder
Horizontal resistance of the bed to the steel cylinder f=pi/4·d 0 ·D 0 ·C u
Step 6: and calculating the anti-tilting moment and the tilting moment of the steel cylinder when the steel cylinder tilts towards the sea.
The active soil pressure Pa1 and Pa2 outside the steel cylinder provide overturning moment; passive earth pressures Pp1, pp2, vertical reaction force q of the foundation bed to the steel cylinder, horizontal resistance force F of the foundation bed to the steel cylinder, internal friction force t1 of the steel cylinder and external friction force t2 of the steel cylinder provide anti-tilting moment, and external loads Fx and Fy provide anti-tilting moment or tilting moment according to moment direction calculation.
Step 7: the safety factor Kl of the steel cylinder pouring to the sea side was calculated.
Wherein M is s Overturning moment, M r -an anti-tipping moment;
wherein:
M s ＝P a1 *|y a1 -R yi |+P a2 *|y a2 -R yi |
P p1 is the resultant force of the land side passive soil pressure, y p1 Is P p1 Y-coordinate of (c); p (P) p2 Is the resultant force of the sea passive soil pressure, y p2 Is P p2 Y-coordinate of (c); n is the number of soil layers outside the cylinder body, x i For E yi The x coordinate, y of the location F Is the y coordinate, P of the horizontal resistance F of the foundation bed to the steel cylinder a1 P is the resultant force of land-side active soil pressure a2 Is the resultant force of the active earth pressure at sea side, y a1 Is P a1 Y coordinate, y a2 Is P a2 Is defined as the y coordinate of (c). 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 provide anti-tilting moment or overturning moment according to moment direction calculation.
Step 8: referring to fig. 3, at the same rotation point O, assuming that the steel cylinder is rotated to the land side, the soil outside the sea side steel cylinder above the rotation point O and the soil outside the sea Liu Gang cylinder below the rotation point O are active soil pressures Pa1 'and Pa2', and the soil outside the sea side steel cylinder below the rotation point O and the soil outside the land side steel cylinder above the rotation point O are passive soil pressures Pp1 'and Pp2'.
The active earth pressures Pa1 'and Pa2', the passive earth pressures Pp1 'and Pp2', the vertical reaction force q 'of the foundation bed to the steel cylinder, the horizontal resistance force 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 are recalculated in the case that the steel cylinder rotates to the land side according to the above method.
Step 9: the moment of resistance to tilting and the moment of tilting of the steel cylinder in the case of tilting to the land side were calculated. It should be noted that no matter which side the steel cylinder is inclined, the active soil pressure outside the steel cylinder provides the overturning moment; the passive soil pressure, the vertical counterforce 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 are all used for providing anti-tilting moment. Therefore, in the case of tilting the steel cylinder to the land side, the active soil pressures Pa1 'and Pa2' outside the steel cylinder in step 8 provide tilting moments, the passive soil 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 t1 'of the steel cylinder, and the external friction t2' of the steel cylinder provide tilting moment.
Step 10: the safety factor Kr of the steel cylinder pouring to the land side was calculated.
Step 11:comparing Kl and Kr, and taking the smaller value of the two as the safety factor F at the rotation point O i 。
Step 12: re-selecting a new rotation point, calculating the safety coefficient corresponding to the new rotation point according to the steps, and taking the minimum value of the safety coefficients in all the rotation points as the final safety coefficient F under the working condition min 。
Example two
The first difference between this embodiment and the second embodiment is that: step 2 in embodiment one may also calculate the active and passive earth pressures outside the steel cylinder using the Muller-Breslau theory, comprising the steps of:
2.1 calculation of active soil pressure
Wherein C is i Cohesive force of soil layer i;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 a i For the thickness of soil layer i, gamma i For the volume weight of the soil layer i, the soil above the water level adopts the natural volume weight, and the soil below the water level adopts the floating volume weight，K axi The active soil pressure coefficient caused by the dead weight of the soil layer i; k (K) acxi The active soil pressure coefficient is caused by soil layer clay aggregation force; e, e axi1 The top active soil pressure of the soil layer i; e, e axi2 The soil pressure is active at the bottom of the soil layer i; e (E) axi Is the active soil pressure resultant force of soil layer i.
2.2 calculating the passive soil pressure
Wherein K is pxi The soil pressure coefficient is the passive soil pressure coefficient of the soil layer i; e, e pxi1 The top passive soil pressure of the soil layer i; e, e pxi2 The bottom passive soil pressure of the soil layer i; e (E) pxi Is the resultant force of the passive soil pressure of the soil layer i.
The foregoing has described exemplary embodiments of the invention, it being understood that any simple variations, modifications, or other equivalent arrangements which would not unduly obscure the invention may be made by those skilled in the art without departing from the spirit of the invention.
Claims (3)
1. The method for predicting the stability of the offshore steel cylinder is characterized by comprising the following steps of:
step 1, acquiring water line information, soil layer information and external load data of a steel cylinder embedded environment, wherein the soil layer information comprises: thickness hi, density gamma of soil layer i Cohesive force C i Friction angle phi i Coefficient of friction delta between soil mass and steel cylinder i ；
Step 2: assuming that the steel cylinder is tilted to the sea, the coordinates of the rotation point O at which the steel cylinder is tilted are defined as (R xi ,R yi ) The soil outside the land-side steel 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 land-side steel 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 buried soil of the steel cylinder is any soil body and the land side soil filling slope angle 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;
the method adopts Coulomb theory to calculate the active soil pressure and the passive soil pressure outside the steel cylinder, and comprises the following steps:
2.1: calculating active earth pressure
Wherein C is i Cohesive force of soil layer i;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 a i For the thickness of soil layer i, gamma i The volume weight of soil layer i, waterThe soil above the water line adopts a natural volume weight, and the soil below the water line adopts a floating volume weight; k (K) axi The active soil pressure coefficient of the soil layer i; e, e axi1 The top active soil pressure of the soil layer i; e, e axi2 The soil pressure is active at the bottom of the soil layer i; e (E) axi The resultant force of the active soil pressure of the soil layer i; the active soil pressure Pa1 is equal to the active soil pressure resultant force E of all soil layers i outside the land-side steel cylinder above the rotation point O axi The sum of which is equal to the active soil pressure resultant force E of all soil layers i outside the sea-side steel cylinder below the rotation point O, the active soil pressure Pa2 axi And (3) summing;
2.2: calculating passive earth pressure
Wherein K is pxi The soil pressure coefficient is the passive soil pressure coefficient of the soil layer i; e, e pxi1 The top passive soil pressure of the soil layer i; e, e pxi2 The bottom passive soil pressure of the soil layer i; e (E) pxi The resultant force of the passive soil pressure of the soil layer i; the passive earth pressure Pp1 is equal to the passive earth pressure resultant force E of all the earth layers i outside the land-side steel cylinder below the rotation point O pxi The sum of the passive soil pressure Pp2 is equal to the resultant force E of the passive soil pressure of all soil layers i outside the sea-side steel cylinder above the rotation point O pxi And (3) summing;
the method adopts Muller-Breslau theory to calculate the active soil pressure and the passive soil pressure outside the steel cylinder, and comprises the following steps:
2.1 calculation of active soil pressure
Wherein C is i Cohesive force of soil layer i;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 a i For the thickness of soil layer i, gamma i For the volume weight of the soil layer i, the soil above the water level adopts the natural volume weight, and the soil below the water level adopts the floating volume weight, K axi The active soil pressure coefficient caused by the dead weight of the soil layer i; k (K) acxi The active soil pressure coefficient is caused by soil layer clay aggregation force; e, e axi1 The top active soil pressure of the soil layer i; e, e axi2 The soil pressure is active at the bottom of the soil layer i; e (E) axi The resultant force of the active soil pressure of the soil layer i;
2.2 calculating the passive soil pressure
Wherein K is pxi The soil pressure coefficient is the passive soil pressure coefficient of the soil layer i; e, e pxi1 The top passive soil pressure of the soil layer i; e, e pxi2 The bottom passive soil pressure of the soil layer i; e (E) pxi The resultant force of the passive soil pressure of the soil layer i;
step 3: calculating the packing pressure inside the steel cylinder
3.1: the inside of the steel cylinder is divided into three sections from top to bottom, namely: an AB segment, a BC segment and a CD segment,
height of AB section:
height of CD segment:
height of BC segment: h is a 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 (D) 0 Is the diameter of a steel cylinder;
3.2: calculating the packing pressure of the AB section:
vertical pressure sigma of packing in steel cylinder y The method comprises the following steps: sigma (sigma) y ＝γAm+q 0 e -h/A
K＝λ 0 tan(δ)
Wherein gamma 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;
λ 0 is the side thrust coefficient of the filler;
the horizontal pressure sigma of the filler to the inner wall of the AB section of the steel cylinder x The method comprises the following steps: sigma (sigma) x ＝λ 0 σ y ；
3.3: calculating the packing pressure of the BC segment:
the packing pressure of the BC-stage is considered to be equal, and therefore the formula σ in step 3.2 is used x ＝λ 0 σ y Calculating the packing pressure sigma at the point B Bx Packing pressure elsewhere in BC segment and packing pressure sigma at point B Bx Equal;
3.4: calculation of packing pressure for CD section:
calculating the filler pressure at the point C and the point D to obtain a linear relation of the filler pressure of the CD section along with the depth change, wherein:
packing pressure sigma at point C Cx Packing pressure σ at point =b Bx ；
The packing pressure at point D is calculated using the following formula: sigma (sigma) Dx ＝λ 0 (σ mid -σ x ) Wherein σ is mid Is the average pressure at the bottom of the steel cylinder;
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 is tilted towards the sea;
4.1: calculating the friction force of the soil layer exposed outside the steel cylinder:
friction force E between soil layer i and outside of steel cylinder yi ＝tan(δ i )·E axi Or E is yi ＝tan(δ i )·E pxi ；
The above formula depends on whether soil layer i participates in the calculation of active soil pressure or passive soil pressure, E when soil layer i participates in the calculation of active soil pressure yi ＝tan(δ i )·E axi ，E axi Is the active soil pressure resultant force of soil layer i; e when the soil layer i participates in the passive soil pressure yi ＝tan(δ i )·E pxi ，E pxi Is the resultant force of the passive soil pressure of the soil layer i;
4.2: the friction force of the filler received inside the steel cylinder is calculated:
friction force E applied to AB section inside steel cylinder yt1AB ＝tan(δ)·σ Bx ·h 1 ·0.5
Friction force E applied to BC segment in steel cylinder yt1BC ＝tan(δ)·σ Cx ·h 2
Friction force E applied to CD segment inside steel cylinder yt1CD ＝tan(δ)·(σ Cx +σ Dx )·h 3 ·0.5；
Step 5: respectively calculating the vertical counterforce and the horizontal resistance of the foundation bed to the steel cylinder under the condition that the steel cylinder is tilted to the sea;
step 6: calculating the moment M of resistance to tilting in case of tilting the steel cylinder to sea r And overturning moment M s ；
The active soil pressure outside the steel cylinder provides a overturning moment; the passive soil pressure and the vertical counterforce 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 provide anti-tilting moment;
wherein:
M s ＝P a1 *|y a1 -R yi |+P a2 *|y a2 -R yi |
P p1 is the resultant force of the land side passive soil pressure, y p1 Is P p1 Y-coordinate of (c); p (P) p2 Is the resultant force of the sea passive soil pressure, y p2 Is P p2 Y-coordinate of (c); n is the number of soil layers outside the cylinder body, x i For E yi The x coordinate, y of the location F Is the y coordinate, P of the horizontal resistance F of the foundation bed to the steel cylinder a1 P is the resultant force of land-side active soil pressure a2 Is the resultant force of the active earth pressure at sea side, y a1 Is P a1 Y coordinate, y a2 Is P a2 Y-coordinate of (c); if the steel cylinder has an external load effect, the external loads Fx and Fy provide anti-tilting moment or overturning moment according to moment direction calculation;
step 7: the safety coefficient Kl of the steel cylinder dumping to the sea side is calculated,
step 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 Liu Gang 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 land side steel cylinder above the rotation point O are passive soil pressures; according to the method, the active soil pressure, the passive soil pressure, the vertical counterforce 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 are recalculated under the condition that the steel cylinder rotates to the land side; calculating an anti-tilting moment and a tilting moment under the condition that the steel cylinder tilts to the land side, and calculating a safety coefficient Kr of tilting of the steel cylinder to the land side;
step 9: comparing the safety factor Kl of the steel cylinder obtained in the step 7 and the safety factor Kr of the steel cylinder obtained in the step 8, and taking the smaller value of the two as the safety factor 2 at the rotation point i ；
Step 10: re-selecting a new rotation point, calculating the safety coefficient corresponding to the new rotation point according to the steps, and taking the minimum value of the safety coefficients in all the rotation points as the final safety coefficient F under the working condition min 。
2. The method for predicting stability of an offshore steel cylinder according to claim 1, wherein: in step 3.2, to simplify the calculation, the change in packing pressure in the AB segment is considered to be a linear change, then according to the formula σ x ＝λ 0 σ y Calculating the packing pressure sigma at the point B Bx The packing pressure at point a is set to 0.
3. The method for predicting stability of an offshore steel cylinder according to claim 1, wherein: the step 5 comprises the following steps:
5.1: vertical reaction force of foundation 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 vertical counterforce of the foundation bed to the steel cylinder is F when the shear strength of the foundation soil body is not drained q ＝*L q ，L q For the distance L between the rotation point and the inclined side q According to the coordinates of the rotation point and the diameter of the steel cylinder, calculating;
5.2: horizontal resistance of foundation bed to steel cylinder
Horizontal resistance of the bed to the steel cylinder f=pi/4·d 0 ·D 0 ·C u 。
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