CN113806852B - Method for predicting stability of deepwater thin-wall steel cylinder - Google Patents
Method for predicting stability of deepwater thin-wall steel cylinder Download PDFInfo
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Abstract
The invention discloses a method for predicting the stability of a deepwater thin-wall steel cylinder, which comprises the steps of firstly establishing a steel cylinder simulation analysis model according to seabed geological condition parameters and steel cylinder condition parameters, and establishing a functional relation among the seabed geological condition parameters, the steel cylinder condition parameters and a limit load; then collecting dynamic stress data generated by the periodic displacement of the steel cylinder on the seabed soil body under the action of the wave cyclic load, obtaining test data of the weakening range and the weakening strength of the seabed soil body under the same dynamic stress level through an indoor test, and establishing a correlation function of the weakening range and the weakening strength with the wave cyclic load; then according to the weakening range and the weakening strength test data of the seabed soil body, calculating the corresponding bearing capacity of the weakened seabed soil body, calculating equivalent seabed geological condition parameters through inversion, and calculating the corresponding ultimate load attenuation coefficient; and finally, combining the attenuation coefficient of the ultimate load and the obtained functional relation to obtain a prediction model of the ultimate load of the steel cylinder under the action of the wave cyclic load.
Description
Technical Field
The invention belongs to the field of design of in-situ stability of a deepwater steel cylinder, and particularly relates to a method for predicting the stability of a deepwater thin-wall 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. A great deal of engineering experience and research has shown that: the working mechanism of the plug-in steel cylinder structure is complex, the plug-in steel cylinder structure cannot be considered as a gravity type structure, and the stability of the plug-in steel cylinder structure is obviously influenced by factors such as seabed, waves, internal fillers and the like.
In the past domestic and foreign engineering practice, in order to prevent the instability of the steel cylinder, the instability-resistant design of the steel cylinder can be carried out only by means of field tests and similar engineering experience. However, in the steel cylinder construction process, the hydrological conditions of the steel cylinder construction site are in continuous change, the instability resistance of the seabed foundation under the wave cyclic load is also in continuous change, and the influence of the changes on the stability of the steel cylinder is difficult to accurately evaluate by early design, so that the potential instability risk of the steel cylinder can be caused.
Disclosure of Invention
The method for predicting the stability of the deepwater thin-wall steel cylinder is characterized by comprising the following steps of:
step 1: establishing a steel cylinder simulation analysis model by using finite element analysis software according to the seabed geological condition parameters and the steel cylinder condition parameters;
step 2: analyzing the limit load when the corresponding steel cylinder is unstable under different seabed geological condition parameters and steel cylinder condition parameters by using a simulation analysis model, and establishing a functional relation among the seabed geological condition parameters, the steel cylinder condition parameters and the limit load;
and step 3: acquiring the size of dynamic stress generated by the periodic displacement of the steel cylinder on the seabed soil body under the action of different wave cyclic loads and dynamic stress distribution area data, then obtaining test data of the seabed soil body weakening range A and the weakening strength eta under the same dynamic stress size and dynamic stress distribution by adopting a static triaxial shear test and a dynamic triaxial shear test, and then establishing a functional relation between the seabed soil body weakening range A and the weakening strength eta and the wave cyclic loads;
and 4, step 4: calculating the corresponding bearing capacity of the weakened seabed soil body by using an indoor model test method according to the seabed soil body weakening range A and the weakening strength eta test data obtained in the step 3, and calculating equivalent seabed geological condition parameters after weakening; then, combining the established functional relationship among the seabed geological condition parameters, the steel cylinder condition parameters and the ultimate loads in the step 2, calculating the ultimate load corresponding to the weakened equivalent seabed geological condition parameters, calculating the ultimate load attenuation coefficient epsilon, and then establishing the functional relationship among the ultimate load attenuation coefficient epsilon, the seabed soil body weakening range A and the weakening strength eta;
and 5: and (4) combining the functions obtained in the steps 2 to 4 to obtain a prediction model of the instability limit load of the steel cylinder under the action of the wave cyclic load.
In the above technical solution, the seabed geological condition parameters include: soil body gravity, soil body cohesion and soil body internal friction angle.
In the above technical scheme, the steel cylinder condition parameters specifically include: the steel cylinder outer diameter, the steel cylinder wall thickness, the steel cylinder height, the steel cylinder burying depth and the steel cylinder internal packing type.
In the above technical solution, the wave cyclic load includes the following parameters: water depth, wave wavelength, different wave forces.
In the above technical solution, step 2 includes the following steps:
s2.1: changing single parameter of seabed geological condition parameter and steel cylinder condition parameter in simulation analysis modelx 1Then calculating the change of the corresponding limit load size P under the given load action height H, and carrying out data correlation analysis to obtain the corresponding single parameter representing the single parameter under the given load action heightx 1Dimensionless influence coefficient beta of the degree of influence1；
S2.2: repeat step S2.1 to obtain the givenThe height H of the load represents the remaining parameters in the geological condition parameters of the seabed and the condition parameters of the steel cylinder (x 2，x 3，x 4，x 5… …) degree of influence (β) is dimensionless2，β3，β4，β5……)；
S2.3: based on the results of steps S2.1 and S2.2, the establishment is based on the respective parametersx 1，x 2，x 3，x 4，x 5… …) predicting the function relation of the limit load size P: p to f (H, beta)1，β2，β3，β4，β5……)。
In the technical scheme, in step 3, in-situ soil sampling is performed on a foundation soil body in an engineering area according to the size of dynamic stress generated on a seabed soil body by the periodic displacement of the steel cylinder and dynamic stress distribution area data, an undisturbed soil sample is transported to a laboratory and then is subjected to static triaxial shear test and dynamic triaxial shear test respectively, the static shear strength of the soil sample is obtained through the static triaxial shear test, the dynamic shear strength of the soil sample is obtained through the dynamic triaxial shear test, and the dynamic shear strength and the static shear strength are divided to obtain the weakening strength eta of the soil sample at the soil sampling point.
In the above technical scheme, in step 3, the thin-wall soil sampler is used for in-situ soil sampling, at least two adjacent undisturbed soil samples are taken from each soil sampling point, one undisturbed soil sample is used for a soil static triaxial shear test, and the other undisturbed soil sample is used for a soil dynamic triaxial shear test.
In the technical scheme, in the step 4, epsilon is equal to the limit load size corresponding to the weakened equivalent seabed geological condition parameter divided by the limit load size corresponding to the initial seabed geological condition parameter of the seabed soil body without the action of wave circulating load.
In the above technical solution, in step 4, the calculated equivalent seabed geological condition parameters after weakening include: soil mass gravity after weakeningW Weak (weak)Weakened soil mass cohesionc Weak (weak)And a weakened internal soil friction angle ϕWeak (weak)The calculation method is as follows:
according to a Hansen foundation bearing capacity calculation formula:
p=c×N c ×S c ×d c ×i c +q×N q ×S q ×i q +0.5×W×D×N r ×S r ×i r whereinS c 、S q 、S r Is a shape correction factor for the structure base,d c is a correction coefficient of the buried depth of the foundation of the structure,i c 、i q 、i r for the load tilt correction factor of the structure,qis the total weight of the steel cylinder structure,Dthe diameter of the steel cylinder is the same as the diameter of the steel cylinder, and the 9 parameters are unchanged before and after the weakening of the seabed soil body, so the ratio of the bearing capacity before and after the weakening of the seabed soil body
，p Original sourceIn order to weaken the bearing capacity of the front seabed soil body,p weak (weak)In order to weaken the bearing capacity of the seabed soil body,G1representsS c ×d c ×i c ，G2Representsq×S q ×i q ，G3Represents0.5×D×S r ×i r ，G1、G2、G3Before and after the weakening of the seabed soil body, the seabed soil body is unchanged;
N c 、N q 、N r for correction factors related to the soil internal friction angle ϕ,
，
，
；
assuming sea bed bearing capacity after weakeningp Weak (weak)Is the original bearing capacityp Original sourceIs/are as followskDoubly, then need to guarantee
Wherein, first, calculate
Because of
Containing only ϕWeak (weak)An unknown number is calculated to obtain the weakened internal friction angle ϕ of the soil bodyWeak (weak)(ii) a Second calculation
And
due to ϕWeak (weak)After the fact that the information is known, the information is obtained,N cweak (weak)AndN rweak (weak)Is also known, therefore, to findc Weak (weak)AndW weak (weak)。
The invention has the advantages and beneficial effects that:
the method for predicting the stability of the deep water thin-wall steel cylinder realizes the prediction of the stability of the steel cylinder and the design of a reinforcing scheme by establishing a mathematical model of the correlation between various engineering parameters and the limit load which can be born by the steel cylinder. Different from the traditional method based on the past engineering experience and small-scale indoor model test, the invention discloses and quantifies the influence degree of each engineering parameter on the instability limit load of the steel cylinder, and simultaneously considers the problem of foundation weakening caused by cyclic wave load, so the reliability of the stability prediction of the steel cylinder is far higher than that of the traditional method.
Drawings
FIG. 1 is a flow chart of the method for predicting the stability of a deep-water thin-wall steel cylinder according to the present invention.
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 the working flow chart of the drawings of the specific embodiment.
Referring to the attached figure 1, the method for predicting the stability of the deepwater thin-wall steel cylinder comprises the following steps:
step S1: and establishing a steel cylinder simulation analysis model by using finite element analysis software according to the seabed geological condition parameters and the steel cylinder condition parameters.
Firstly, collecting field engineering measured data, including: and (3) seabed geological condition parameters (the seabed geological condition parameters comprise soil mass weight W, soil mass cohesive force c and soil mass internal friction angle ϕ), and steel cylinder condition parameters (the steel cylinder condition parameters comprise steel cylinder outer diameter D, steel cylinder wall thickness W, steel cylinder height Hc, steel cylinder burying depth S and steel cylinder internal packing type M).
According to the data, a steel cylinder simulation analysis model is established by ABAQUS finite element analysis software, and the model can be used for calculating the limit load size and the limit load action height when the steel cylinder is unstable (the height position of the steel cylinder is set in the simulation analysis model, when the displacement of the steel cylinder starts to be infinitely increased, the load at the moment is the corresponding limit load when the steel cylinder is unstable, and the height position of the applied load is the limit load action height, namely, the loads are applied at different height positions, and the corresponding unstable limit load size can be obtained). Specifically speaking: in this embodiment, first, three-dimensional solid modeling is performed in the ABAQUS software, and a steel cylinder model, a steel cylinder internal filler model, and a seabed foundation model are respectively established. Wherein, the outer diameter, the wall thickness and the height of the steel cylinder model are selected according to engineering data; the size of the seabed foundation model is as follows: the length and the width are both equal to 10 times of the outer diameter of the steel cylinder, the depth is the buried depth of the steel cylinder plus 50m, and the seabed foundation model is endowed with appropriate unit types and constraints according to data such as soil mass weight W, soil mass cohesive force c, soil mass internal friction angle ϕ and the like; assembling the steel cylinder and the seabed foundation soil body, and dividing grids, wherein the size of the grids is divided by taking 1m as a typical scale. 4 analysis steps are set during calculation, wherein the 1 st analysis step is a ground stress balance analysis step and is used for recovering the foundation stress in the original foundation soil body; 2, digging a simulation step for the steel cylinder, digging a soil body of the inserted part of the steel cylinder in the undisturbed foundation, sinking the steel cylinder to a specified elevation, and then applying gravity to the steel cylinder; step 3, simulating steel cylinder filler, namely filling the steel cylinder filler into a steel cylinder model, and applying gravity to the filler in the cylinder; and 4, a step of analyzing the stability of the steel cylinder, namely applying a concentrated horizontal force to a certain point on the steel cylinder, gradually increasing the numerical value of the horizontal force until the steel cylinder generates instability damage under the action of the horizontal force, recording the magnitude of the horizontal force at the moment and the height of the horizontal force application point from the surface of the seabed mud, wherein the group of numerical values are the magnitude P of the ultimate load of the steel cylinder and the corresponding height H of the ultimate load action.
Step S2: and analyzing the ultimate load when the corresponding steel cylinder is unstable under different seabed geological condition parameters and steel cylinder condition parameters by using the simulation analysis model, and establishing a functional relation among the seabed geological condition parameters, the steel cylinder condition parameters and the ultimate load according to the following process.
S2.1: changing single parameter of seabed geological condition parameter and steel cylinder condition parameter in simulation analysis modelx 1Then calculating the change of the corresponding limit load size P under the given load action height H, and carrying out data correlation analysis to obtain the corresponding representative parameter under the given load action height Hx 1Dimensionless influence coefficient beta of the degree of influence1. That is, each different load height corresponds to a different dimensionless influence coefficient β1In the present embodiment, fromThe height of the steel cylinder of more than 40 meters at intervals of 1 meter along the height direction of the steel cylinder is determined as a load action position, and each load action position corresponds to one representing the parameterx 1Dimensionless influence coefficient beta of the degree of influence1。
S2.2: repeating the step S2.1 to obtain the remaining parameters (x 2，x 3，x 4，x 5… …) degree of influence (β) is dimensionless2，β3，β4，β5……)。
S2.3: based on the results of steps S2.1 and S2.2, the establishment is based on the respective parametersx 1，x 2，x 3，x 4，x 5… …) predicting the function relation of the limit load size P: p to f (H, beta)1，β2，β3，β4，β5… …), e.g., P = k1β1×k2β1×k3β3×k4β4×k5β5×…×knH/Hc, where Hc is the height of the steel cylinder, k1 、k2 、k3 、k4、k5、knFor undetermined coefficients, each load action height H corresponds to a set of dimensionless influence coefficients (beta)1，β2，β3，β4，β5……）。
Step S3: the method comprises the steps of obtaining the size of dynamic stress generated by periodic displacement of a steel cylinder on a seabed soil body under the action of wave cyclic loads of different water depths Hw, wave wavelengths L and wave forces F and dynamic stress distribution area data, then analyzing the seabed soil body strength weakening rule under the same dynamic stress level by adopting an indoor static triaxial shear test and a dynamic triaxial shear test, and obtaining test data of a seabed soil body weakening range A and weakening strength eta. Specifically speaking: firstly, according to the magnitude of dynamic stress generated by the periodic displacement of the steel cylinder on the seabed soil body and the data of the dynamic stress distribution area, the soil of the foundation of the engineering area is subjected to in-situ soil borrowing, for example, the distance from the steel cylinder to the steel cylinderWithin the horizontal distance of the cylinder of 100 m, the foundation soil body within the depth of 30 m can be obviously influenced, the soil body in the area needs to be sampled, and the horizontal distance of the soil sampling point positions is planned according to the attenuation degree of the dynamic stress along with the horizontal distance. If the attenuation of the dynamic stress along with the horizontal distance is obvious, the horizontal distance of the soil sampling point position needs to be reduced; if the dynamic stress slowly attenuates with the horizontal distance, the horizontal distance of the soil sampling point position can be properly increased. The in-situ soil sampling adopts a thin-wall soil sampler, at least two adjacent undisturbed soil samples are taken from each soil sampling point, one undisturbed soil sample is used for a soil static triaxial shear test, and the other undisturbed soil sample is used for a soil dynamic triaxial shear test. Then, the undisturbed soil sample is transported to a laboratory and then is subjected to static triaxial shear test and dynamic triaxial shear test respectively, the static shear strength of the soil sample is obtained through the static triaxial shear test, the dynamic shear strength of the soil sample subjected to power cycle loading is obtained through the dynamic triaxial shear test, and the dynamic shear strength is divided by the originally obtained static shear strength, so that the weakening strength eta of the soil sample at the soil sampling point is obtained. According to the weakening strength eta data of all soil sampling point location soil samples, the distribution conditions of the seabed soil weakening area range and the weakening strength eta in the weakening area range can be obtained, the weakening range A is reasonably divided according to the size grade of the weakening strength eta of each soil sampling point location, and in the embodiment, the weakening range A is divided into three parts:
。
then, fitting the relation between the water depth Hw, the wave wavelength L and the wave force F and the weakening range A and the weakening strength eta of the seabed soil body by using a least square method according to the obtained weakening range A and weakening strength eta data of the seabed soil body, and establishing the relevant functions of the weakening range A and the weakening strength eta and the water depth Hw, the wave wavelength L and the weakening strength F: (A, η) ~ζ (Hw, L, F), for example,
wherein D is the outer diameter of the steel cylinder.
Step S4: according to the seabed soil weakening range A and the weakening strength eta test data obtained by the indoor static and dynamic triaxial shear test in the step S3, calculating the corresponding bearing capacity of the weakened seabed soil by using an indoor model test method, and calculating equivalent seabed geological condition parameters (including the seriously weakened seabed soil) after weakening by using a bearing capacity calculation theory inversionW Weak (weak)Weakened soil mass cohesionc Weak (weak)And a weakened internal soil friction angle ϕWeak (weak)) The specific calculation method is as follows:
according to a Hansen foundation bearing capacity calculation formula:
p=c×N c ×S c ×d c ×i c +q×N q ×S q ×i q +0.5×W×D×N r ×S r ×i r whereinS c 、S q 、S r Is a shape correction factor for the structure base,d c is a correction coefficient of the buried depth of the foundation of the structure,i c 、i q 、i r for the load tilt correction factor of the structure,qis the total weight of the steel cylinder structure,Dthe diameter of the steel cylinder is the same as the diameter of the steel cylinder, and the 9 parameters are unchanged before and after the weakening of the seabed soil body, so the ratio of the bearing capacity before and after the weakening of the seabed soil body
，p Original sourceIn order to weaken the bearing capacity of the front seabed soil body,p weak (weak)After being weakenedThe bearing capacity of the seabed soil body is improved,G1representsS c ×d c ×i c ，G2Representsq×S q ×i q ，G3Represents0.5×D×S r ×i r ，G1、G2、G3Before and after the weakening of the seabed soil body, the seabed soil body is unchanged;
N c 、N q 、N r for correction factors related to the soil internal friction angle ϕ,
，
，
；
assuming sea bed bearing capacity after weakeningp Weak (weak)Is the original bearing capacityp Original sourceIs/are as followskDoubly, then need to guarantee
Wherein, first, calculate
Because of
Containing only ϕWeak (weak)An unknown number is calculated to obtain the weakened internal friction angle ϕ of the soil bodyWeak (weak)(ii) a Second calculation
And
due to ϕWeak (weak)After the fact that the information is known, the information is obtained,N cweak (weak)AndN rweak (weak)Is also known, therefore, to findc Weak (weak)AndW weak (weak)。
And then combining the function relation P-f (H, beta) of the maximum load size P predicted based on the seabed geological condition parameters and the steel cylinder condition parameters established in the step S21，β2，β3，β4，β5… …), calculating the limit load size corresponding to the weakened equivalent seabed geological condition parameters (during calculation, the action height H of the limit load is taken as the value of the water depth Hw of the corresponding wave circulation load in the step S3, namely, the steel cylinder is loaded at the water surface position), calculating the limit load attenuation coefficient epsilon, epsilon is less than or equal to 1, and epsilon is equal to the limit load size corresponding to the weakened equivalent seabed geological condition parameters divided by the corresponding limit load size under the initial seabed geological condition parameters of the seabed soil body without the wave circulation load; then fitting the relation between the seabed soil body weakening range A and the weakening strength eta and the limit load attenuation coefficient epsilon by using a least square method, establishing the correlation function relation epsilon-g (A, eta) between the limit load attenuation coefficient epsilon and the seabed soil body weakening range A and the weakening strength eta, for example,
。
step S5: according to the functional relationship between the limit load attenuation coefficient epsilon and the seabed soil body weakening range A and weakening strength eta obtained in the step S4 and the functional relationship between the seabed soil body weakening range A and weakening strength eta and the water depth Hw, wave wavelength L and wave force F obtained in the step S3, the functional relationship between the limit load attenuation coefficient epsilon and the water depth Hw, wave wavelength L and wave force F can be obtained, and then the limit load attenuation coefficient epsilon is multiplied by the function of the predicted limit load size P obtained in the step S1, so that the prediction model of the steel cylinder instability limit load under the action of the wave cyclic load can be obtained: p to ε x f (H, β)1，β2，β3，β4，β5……)。
In the actual engineering design, the deep-water thin-wall steel cylinder is adopted for stabilityAccording to the seabed geological condition parameters, the steel cylinder condition parameters and the wave circulating load parameters, the qualitative prediction method can predict and calculate the limit load P which can be born by the steel cylinder and the current actual load born by the steel cylinderP TAnd automatically calculates the safety factor K, K = P P T. If the safety coefficient K is smaller than 1 and the structure is unstable, firstly trial calculation is carried out to determine whether the safety coefficient K can meet the requirement under the condition that attenuation caused by cyclic load is not considered (namely epsilon = 1). And if the requirement is met, designing a foundation reinforcement treatment scheme, and designing the foundation reinforcement depth and range according to the seabed foundation weakening range given by the functions (A, eta) -zeta (Hw, L and F). And if the safety coefficient K still does not meet the requirement during trial calculation under the condition of epsilon = 1, optimizing the design of the steel cylinder until the safety coefficient K meets the requirement.
The invention has been described by way of example, and it is to be understood that any simple variation, modification or equivalent replacement by a person skilled in the art without inventive step falls within the scope of protection of the present invention without departing from the core of the present invention.
Claims (9)
1. The method for predicting the stability of the deepwater thin-wall steel cylinder is characterized by comprising the following steps of:
step 1: establishing a steel cylinder simulation analysis model by using finite element analysis software according to the seabed geological condition parameters and the steel cylinder condition parameters;
step 2: analyzing the limit load when the corresponding steel cylinder is unstable under different seabed geological condition parameters and steel cylinder condition parameters by using a simulation analysis model, and establishing a functional relation among the seabed geological condition parameters, the steel cylinder condition parameters and the limit load;
and step 3: acquiring the size of dynamic stress generated by the periodic displacement of the steel cylinder on the seabed soil body under the action of different wave cyclic loads and dynamic stress distribution area data, then obtaining test data of the seabed soil body weakening range A and the weakening strength eta under the same dynamic stress size and dynamic stress distribution by adopting a static triaxial shear test and a dynamic triaxial shear test, and then establishing a functional relation between the seabed soil body weakening range A and the weakening strength eta and the wave cyclic loads;
and 4, step 4: calculating the corresponding bearing capacity of the weakened seabed soil body by using an indoor model test method according to the seabed soil body weakening range A and the weakening strength eta test data obtained in the step 3, and calculating equivalent seabed geological condition parameters after weakening; then, combining the established functional relationship among the seabed geological condition parameters, the steel cylinder condition parameters and the ultimate loads in the step 2, calculating the ultimate load corresponding to the weakened equivalent seabed geological condition parameters, calculating the ultimate load attenuation coefficient epsilon, and then establishing the functional relationship among the ultimate load attenuation coefficient epsilon, the seabed soil body weakening range A and the weakening strength eta;
and 5: and (4) combining the functions obtained in the steps 2 to 4 to obtain a prediction model of the instability limit load of the steel cylinder under the action of the wave cyclic load.
2. The method for predicting the stability of the deep-water thin-walled steel cylinder according to claim 1, wherein: the seabed geological condition parameters comprise: soil body gravity, soil body cohesion and soil body internal friction angle.
3. The method for predicting the stability of the deep-water thin-walled steel cylinder according to claim 1, wherein: the steel cylinder condition parameters specifically include: the steel cylinder outer diameter, the steel cylinder wall thickness, the steel cylinder height, the steel cylinder burying depth and the steel cylinder internal packing type.
4. The method for predicting the stability of the deep-water thin-walled steel cylinder according to claim 1, wherein: the wave cyclic load comprises the following parameters: water depth, wave wavelength, different wave forces.
5. The method for predicting the stability of the deep-water thin-wall steel cylinder according to claim 1, wherein the step 2 comprises the following steps:
s2.1: changing single parameter of seabed geological condition parameter and steel cylinder condition parameter in simulation analysis modelx 1Then calculating the change of the corresponding limit load size P under the given load action height H, and carrying out data correlation analysis to obtain the corresponding single parameter representing the single parameter under the given load action heightx 1Dimensionless influence coefficient beta of the degree of influence1；
S2.2: repeating the step S2.1 to obtain the residual parameters (in the parameters of the seabed geological condition and the steel cylinder condition under the given load action height H)x 2，x 3，x 4，x 5… …) degree of influence (β) is dimensionless2，β3，β4，β5……)；
S2.3: based on the results of steps S2.1 and S2.2, the establishment is based on the respective parametersx 1，x 2，x 3，x 4，x 5… …) predicting the function relation of the limit load size P: p to f (H, beta)1，β2，β3，β4，β5……)。
6. The method for predicting the stability of the deep-water thin-walled steel cylinder according to claim 1, wherein: in step 3, in-situ soil sampling is carried out on the foundation soil body of the engineering region according to the size of the dynamic stress generated on the seabed soil body by the periodic displacement of the steel cylinder and the data of the dynamic stress distribution region, the undisturbed soil sample is transported to a laboratory and then is respectively subjected to static triaxial shear test and dynamic triaxial shear test, the static shear strength of the soil sample is obtained through the static triaxial shear test, the dynamic shear strength of the soil sample is obtained through the dynamic triaxial shear test, and the dynamic shear strength and the static shear strength are divided to obtain the weakening strength eta of the soil sample at the soil sampling site.
7. The method for predicting the stability of a deep water thin-walled steel cylinder according to claim 6, wherein: in the step 3, a thin-wall soil sampler is adopted for in-situ soil sampling, at least two adjacent undisturbed soil samples are taken from each soil sampling point, one undisturbed soil sample is used for a soil static triaxial shear test, and the other undisturbed soil sample is used for a soil dynamic triaxial shear test.
8. The method for predicting the stability of the deep-water thin-walled steel cylinder according to claim 1, wherein: in the step 4, the epsilon is equal to the limit load size corresponding to the weakened equivalent seabed geological condition parameter divided by the limit load size corresponding to the initial seabed geological condition parameter of the seabed soil body without the action of wave circulating load.
9. The method for predicting the stability of the deep-water thin-walled steel cylinder according to claim 1, wherein: in step 4, the calculated equivalent seabed geological condition parameters after weakening comprise: soil mass gravity after weakeningW Weak (weak)Weakened soil mass cohesionc Weak (weak)And a weakened internal soil friction angle ϕWeak (weak)The calculation method is as follows:
according to a Hansen foundation bearing capacity calculation formula:
p=c×N c ×S c ×d c ×i c +q×N q ×S q ×i q +0.5×W×D×N r ×S r ×i r whereinS c 、S q 、S r Is a shape correction factor for the structure base,d c is a correction coefficient of the buried depth of the foundation of the structure,i c 、i q 、i r for the load tilt correction factor of the structure,qis a steel cylinder structure assemblyThe weight of the mixture is measured,Dthe diameter of the steel cylinder is the same as the diameter of the steel cylinder, and the 9 parameters are unchanged before and after the weakening of the seabed soil body, so the ratio of the bearing capacity before and after the weakening of the seabed soil body
，p Original sourceIn order to weaken the bearing capacity of the front seabed soil body,p weak (weak)In order to weaken the bearing capacity of the seabed soil body,G1representsS c ×d c ×i c ，G2Representsq×S q ×i q ，G3Represents0.5 ×D×S r ×i r ，G1、G2、G3Before and after the weakening of the seabed soil body, the seabed soil body is unchanged;
N c 、N q 、N r for correction factors related to the soil internal friction angle ϕ,
，
，
；
assuming sea bed bearing capacity after weakeningp Weak (weak)Is the original bearing capacityp Original sourceIs/are as followskDoubly, then need to guarantee
Wherein, first, calculate
Because of
Containing only ϕWeak (weak)An unknown number is calculated to obtain the weakened internal friction angle ϕ of the soil bodyWeak (weak)(ii) a Second calculation
And
due to ϕWeak (weak)After the fact that the information is known, the information is obtained,N cweak (weak)AndN rweak (weak)Is also known, therefore, to findc Weak (weak)AndW weak (weak)。
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| CN114809125B (en) * | 2022-04-15 | 2023-09-12 | 中交天津港湾工程研究院有限公司 | Method for predicting anti-tilting stability of steel cylinder |
| CN116882320B (en) * | 2023-08-16 | 2024-03-22 | 珠江水利委员会珠江水利科学研究院 | Stability evaluation method, device and medium for offshore engineering service period foundation structure |
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| CN109724864A (en) * | 2019-01-23 | 2019-05-07 | 中国海洋大学 | It tests the more loads of ocean engineering pile foundation-soil dynamic response and couples loading device |
| CN112734081A (en) * | 2020-12-15 | 2021-04-30 | 福建工程学院 | Prediction method of impact force of landslide collapse block on submarine pipeline |
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| CN112948939B (en) | 2021-03-12 | 2022-07-12 | 上海大学 | Single-pile dynamic stability analysis method and system under ship impact load action |
| CN113806852B (en) * | 2021-11-22 | 2022-02-22 | 中交天津港湾工程研究院有限公司 | Method for predicting stability of deepwater thin-wall steel cylinder |
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| CN106644733A (en) * | 2016-11-21 | 2017-05-10 | 上海交通大学 | Testing equipment for simulating response on embedded type pile-seabed by one-dimensional wave load |
| CN109724864A (en) * | 2019-01-23 | 2019-05-07 | 中国海洋大学 | It tests the more loads of ocean engineering pile foundation-soil dynamic response and couples loading device |
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