CN115233753A - Method for rapidly obtaining bearing capacity of foundation pile based on reverse self-balancing pile testing method - Google Patents
Method for rapidly obtaining bearing capacity of foundation pile based on reverse self-balancing pile testing method Download PDFInfo
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Abstract
The invention discloses a method for quickly obtaining bearing capacity of a foundation pile based on a reverse self-balancing pile test method, which comprises the steps of adopting abaqus software to carry out reverse self-balancing pile test simulation, firstly establishing a reverse self-balancing pile test model, then endowing each part of the model with corresponding material attribute parameters, assembling each part in a general coordinate system, reserving a proper initial interval between an upper pile and a lower pile, then selecting an analysis type from an analysis step module, setting a contact interface type in an interaction module, then setting a convenient boundary condition in a load module, carrying out loading according to the reverse self-balancing pile test method to obtain a load displacement curve, and obtaining the bearing capacity of the foundation pile according to a calculation method of the reverse self-balancing pile test method. The invention does not need complicated and long test piles and in-situ engineering pile tests, greatly reduces the engineering period and improves the construction efficiency.
Description
Technical Field
The invention belongs to the field of pile foundation engineering, relates to a pile foundation bearing capacity calculation method, and particularly relates to a method for quickly obtaining the bearing capacity of a foundation pile based on a reverse self-balancing pile testing method.
Background
The existing method for obtaining the bearing capacity of the foundation pile comprises an in-situ static load test and a self-balancing pile test method. The in-situ static load test is the most reliable method for detecting the bearing capacity of the foundation pile. The counter force of the static load test can be provided by the counter force of the ballast platform or the anchor pile, but is limited by the volume of the ballast platform and the condition for arranging the anchor pile, and the test of the bearing capacity of a special site and a large-tonnage foundation pile is difficult to meet. The self-balancing pile testing method utilizes the dead weight and the frictional resistance of the pile as the counter force of the resistance at the pile end, does not need an additional weight platform or pile loading, breaks through the limitation of the tonnage of the test pile, and is particularly suitable for the bearing capacity detection of the large-diameter pile foundation. The method has the advantages of time and labor saving, convenient test, strong adaptability and the like, and is widely applied to engineering at present. However, the self-balancing pile test method has two problems to be solved because the load action position and direction are different, which causes the load transmission rule and the pile side frictional resistance to be different from the traditional static load test pile:
(1) The self-balancing test result needs to be converted to obtain the bearing capacity of the foundation pile, so that the determination of the conversion coefficient is a key link in the application of the self-balancing pile test method.
(2) The determination of the position of the balance point is particularly critical, and if the position of the balance point cannot be estimated accurately, the difference between the detection result and the actual result is large, and reliable data cannot be provided for engineering design and pile foundation safety evaluation.
Aiming at the problem of determining the conversion coefficient in the self-balancing pile testing method, a test method for obtaining the bearing capacity of a foundation pile based on a reverse self-balancing pile testing method is provided, a pile top vertical loading device is added on the basis of the self-balancing pile testing method, the technical problem that the negative friction resistance of an upper section pile needs to be converted to the positive friction resistance in the self-balancing pile testing method is solved, and meanwhile the tensile bearing capacity of the pile can be tested. At present, the reverse self-balancing pile testing method is still in a theoretical and experimental research stage, and a problem needs to be solved urgently. However, the model test and the field test are long in period, high in cost, unrepeatable and large in uncertainty of influencing factors, and if the model test and the in-situ test are carried out blindly, the scientificity and the success rate of the test cannot be guaranteed. The finite element analysis has the characteristics of low cost and short period. Therefore, the reverse self-balancing model is established through finite element simulation software, the problems existing in the application of the reverse self-balancing pile testing method are analyzed and demonstrated, and the application of the reverse self-balancing pile testing method in foundation pile engineering is promoted.
The patent CN111894051A discloses a reverse self-balancing model test device of pile foundation bearing capacity and a test method thereof, and the device comprises a model box, model piles, a counter-force anchoring system, a loading system, a jack protection box and a measuring system, wherein a simulation rock stratum is poured at the bottom in the model box, a soil filling layer is arranged above the simulation rock stratum, each model pile comprises an upper-section pile and a lower-section pile, the upper-section pile and the lower-section pile are connected together through an anchor cable and a pile top counter-force end plate, the upper-section pile and the lower-section pile are prefabricated hollow tubular piles, and the top and the bottom of the lower-section pile, the top of the upper-section pile and the bottom of the lower-section pile are provided with end sealing plates; when the method is used for pouring, the lower section pile is buried in a simulated rock stratum, loads of the upper section pile and the lower section pile which move oppositely and oppositely are applied by using the two jacks, and the strain and the displacement of the model pile and the model box are measured by using the measuring system. The method can be used for researching the applicability and the bearing characteristic of the reverse self-balancing pile test method and can provide guidance for the design of a relevant model test in the future. However, the technology needs to perform a model pile test, the test process is long, the obtained data is influenced by a monitoring means, and most importantly, the technology does not consider the problem of the reserved space between an upper pile and a lower pile, the space is insufficient, the accurate limit positive bearing capacity of the upper pile cannot be obtained when a pile jack is loaded, the calculation of the limit bearing capacity is finally wrong, the project is wasted when the space is too large, the possibility that soil around the upper pile and the lower pile collapses in the loading process is existed, the accurate limit bearing capacity cannot be obtained, the accurate initial space between the upper pile and the lower pile needs to be obtained, a large amount of test verification needs to be performed, the test period is very long, and the cost is very high.
Disclosure of Invention
The invention aims to provide a method for quickly obtaining bearing capacity of a foundation pile based on a reverse self-balancing pile testing method, and solves the problems of long pile testing model time and high cost in the prior art.
The invention also aims to provide a method for quickly obtaining the bearing capacity of a foundation pile based on a reverse self-balancing pile testing method, and the method is used for solving the problem that the bearing capacity of an upper-section pile cannot be well exerted because a proper initial distance is reserved between an upper pile and a lower pile in the prior art.
The invention also aims to provide a method for quickly obtaining the bearing capacity of a foundation pile based on a reverse self-balancing pile testing method, which solves the problem that the bearing capacity of a pile foundation cannot be truly reflected due to early end of loading caused by the fact that the anchorage of a lower section pile is not enhanced in the prior art.
In order to solve the technical problems, the technical means adopted by the invention are as follows:
a method for rapidly obtaining bearing capacity of a foundation pile based on a reverse self-balancing pile test method adopts abaqus software to simulate a reverse self-balancing pile test, and is characterized by comprising the following steps:
8.1, removing the pile in the reverse self-balancing pile test model, performing ground stress analysis on the soil body only, applying displacement constraint on the side surface and the bottom surface of the pile and the soil, applying self-weight load on the soil body, and performing soil body stress self-balancing calculation by adopting Geostatic analysis stepping;
step 8.2, in the load module, pile-soil contact calculation is carried out, and the load effect of a soil body after pile forming on the pile is simulated; adding a pile in the second Geostatic analysis step, canceling the displacement constraint of the pile and soil to enable the pile and the soil to be in contact, and simultaneously counting the influence of the self weight of the pile;
8.3, loading the pile body in the load module; in the Static General analysis step, upward uniform load is applied to the bottom of an upper section pile, and downward uniform load is applied to the top of a lower section pile;
8.4, in the load module, unloading the pile body in the newly-built Static General analysis step and applying uniform load for simulating the unloading stress state of the pile;
step 8.5, pile top loading is carried out in the load module, downward uniform load is applied to the pile top of the upper section of the pile in the newly-built Static General analysis step, and upward uniform load is applied to the pile top of the lower section of the pile at the same time, so that loading analysis of the reverse self-balancing pile test model is completed;
step 9, in the task module, creating an analysis job, submitting calculation, and then generating an inp calculation file;
and step 10, in a visualization module of abaqus software, obtaining a reverse self-balancing pile test model and loading analysis result information from a task module output database, and performing subsequent data processing analysis, wherein the subsequent data processing analysis comprises a contour cloud chart, a vector diagram, a grid deformation diagram and an XY curve diagram.
Further, in step 1, the reverse self-balancing test pile model creation types include a three-dimensional model, a two-dimensional plane model and an axisymmetric space model, wherein the axisymmetric space model is symmetric about a pile axis and is half of the two-dimensional plane model.
Further, the reverse self-balancing test pile model is an axisymmetric space model, soil bodies around the pile are arranged in a layered mode, the vertical direction of the soil body model is 1.5-3 times of the total length of the foundation pile, and the horizontal direction size of the soil body is 15-30 times of the diameter of the foundation pile.
Further, in step 2, the parameters of the material properties of the foundation pile include young's modulus, poisson's ratio and gravity; parameters of material attributes of the soil body around the pile comprise Young modulus, poisson ratio, gravity, cohesive force and internal friction angle; and after the material parameters are input, defining interface attributes, and distributing the interface attributes to corresponding areas to realize material partitioning.
Further, in step 3, a certain initial distance is reserved between the upper pile and the lower pile, and the initial distance is obtained through calculation or determined according to the loading analysis result in step 8, so that the load displacement curve of the upper pile changes suddenly before the upper pile contacts the lower pile in the process of loading the pile top.
Further, in the interaction module, the bottom surface of the foundation pile is in a surface-surface contact pair type with the outer rock soil and the outer bed rock; the pile is a main control surface, the rock soil is a subordinate surface, a face-to-face discrete method is adopted, and limited slippage is adopted in a pile and soil body contact tracking method; the contact property between the pile and the rock-soil contact surface comprises two aspects, namely, the normal direction adopts hard contact allowing separation, and the tangential direction adopts a coulomb penalty rigidity algorithm to determine a friction coefficient; and simultaneously, determining the bonding strength between the pile bottom of the lower section of pile and the soil body.
Further, in the step 7, in the grid division process, the part close to the pile body is densely divided, and the part far away from the pile body is sparse; the pile and the soil body adopt C3D8R grid units, namely node quadrilateral linear plane strain reduction integral units.
Further, in step 8.1, in the soil stress self-balancing calculation process, the self-balancing convergence condition is that the soil displacement is less than 10 -5 m。
Further, in step 8.2, a plurality of Static General analysis steps are established to increase the load step by step.
Further, in step 8.3 and step 8.5, the end-of-loading condition is that any one of sudden change of load-displacement curve, destruction of upper section pile, destruction of lower section pile, and destruction of soil around between upper and lower piles occurs, and then the end is completed.
Further, the air conditioner is provided with a fan,
compared with the prior art, the invention has the following beneficial effects:
the invention can rapidly calculate the bearing capacity of the pile foundation in a simulation mode without complicated and long test piles and in-situ engineering pile tests, thereby greatly reducing the engineering period and improving the construction efficiency.
The invention considers the proper initial distance reserved between the upper pile and the lower pile, so that the bearing capacity of the pile foundation obtained by the invention is more accurate and more conforms to the actual condition of the engineering pile.
The invention increases the anchoring condition of the lower section of the pile, so that the invention can exert the bearing capacity of the upper section of the pile to the maximum extent, and the pile foundation bearing capacity obtained by the invention is more accurate and more conforms to the actual condition of the engineering pile.
Drawings
Fig. 1 is a schematic structural diagram of a pile test model of the reverse self-balancing pile test method.
Fig. 2 is a schematic diagram of a finite element model with a reverse self-balancing test pile model, wherein a in fig. 2 is a finite element geometric model diagram, and b in fig. 2 is a mesh division diagram of the finite element model.
Fig. 3 is a schematic view of reverse self-balancing loading, where a in fig. 3 is a schematic view of loading and stress of a pile body, and b in fig. 3 is a schematic view of loading and stress of a pile top.
Fig. 4 is a load-displacement curve diagram of the engineering pile static load foundation pile in the embodiment of the invention.
Fig. 5 is a load-displacement curve diagram of a reverse self-balancing foundation pile, wherein a in fig. 5 is a load-displacement curve diagram of a pile body jack, and b in fig. 5 is a load-displacement curve diagram of a pile jack.
1-loading a reaction plate; 2-dial indicator; 3-a data acquisition system; 4-loading the system; 5-upper pile section; 6-a displacement rod; 7-anchor cable; 8-load box; 9-lower section of piles; 10-foundation piles; 11-pile-surrounding soil mass; 12-partial enlargement of the finite element model; 100-fine silt and silt; 200-fine silt and 300-stroke argillite.
Detailed Description
The embodiments of the present invention will be described in further detail with reference to the drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive efforts based on the embodiments of the present invention, shall fall within the scope of protection of the present invention.
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
The invention is further described with reference to the following drawings and specific examples, which are not intended to be limiting.
As shown in fig. 1, referring to patent CN111894051A, a pile foundation self-balancing test apparatus of a reverse self-balancing pile test method includes a loading reaction plate 1, a dial indicator 2, a data acquisition system 3, a loading system 4, a foundation pile 10, a displacement rod 6, an anchor cable 7, a load box 8, and two loading devices, where the foundation pile 10 is divided into an upper pile 5 and a lower pile 9; for two loading devices, firstly, a load box 8 is arranged at a pile body balance point, a pile body jack and a pressure sensor are arranged in the load box 8, and secondly, a pile jack is arranged at the pile top. The top of the pile jack is provided with a loading reaction plate, and the loading reaction plate 1 is connected with a reaction anchoring system arranged at the top of the lower section of pile through an anchor cable freely penetrating through the upper section of pile. When the test is carried out, the load box 8 is pressed through the ground loading system 4, so that the jack of the pile body is ejected out, the upper section pile and the lower section pile are forced to move back to back, the side friction resistance and the end resistance of the pile are excited to be exerted, the displacement monitoring system consisting of the displacement rod 6 and the dial indicator 2 is used for obtaining the pile foundation movement displacement, the pressure sensor in the load box 8 is used for obtaining the pile foundation load, and the negative bearing capacity of the upper section pile 5 and the positive bearing capacity of the lower section pile 9 are obtained. And then, returning oil by using a pile body jack, loading the pile jack, and forcing the upper-section pile 5 and the lower-section pile 9 to move oppositely to obtain the positive bearing capacity of the upper-section pile 5 and the negative bearing capacity of the lower-section pile 9. And finally, the vertical compression resistance total limit bearing capacity of the test pile is the sum of the positive bearing capacity of the upper section pile, the positive bearing capacity of the lower section pile and the self weight of the pile body, and is specifically shown in a formula (1). The total vertical uplift bearing capacity of the pile is the sum of the negative bearing capacity of the upper pile and the negative bearing capacity of the lower pile, the dead weight of the pile body is reduced, and the concrete formula (2) shows,
Q pressing and pressing ＝Q uu + +Q ud + + G formula (1)
Q Pulling out ＝Q uu - +Q ud - -G formula (2)
Wherein Q is Pressing and pressing For testing the vertical compression-resistant total ultimate bearing capacity, Q uu + For positive bearing capacity of upper pile section, Q ud + Is a lower segmentPositive bearing capacity of the pile; q Pulling out For the total ultimate bearing capacity, Q, of the pile in the vertical direction uu - For the upper pile to bear load, Q ud - The bearing capacity of the lower pile is loaded, and G is the dead weight of the pile body.
Taking a certain project as an example, the feasibility of the method is demonstrated. The method comprises the following specific steps:
And 2, determining the properties of the pile soil material in the property module. The concrete pile soil parameters are shown in table 1. The pile body adopts a linear elastic model, the soil body adopts an elastic-plastic model, a MoCoulomb model is selected, and after interface attributes are defined, the interface attributes are assigned to corresponding areas to realize material zoning;
and 3, assembling the created pile-soil components together in an assembly module, and reserving a certain distance between the piles. In the pile top loading process, if the reserved distance in the pile is too small, the upper-section pile and the lower-section pile may contact prematurely, and the side frictional resistance of the upper-section pile is not fully exerted; if the reserved distance S in the pile is too large, soil around the pile can be sunken towards the reserved space in the loading process, the test result is also not facilitated, and therefore a proper distance needs to be reserved between the upper-section pile and the lower-section pile. Through comparative analysis of the ultimate bearing capacity obtained by simulating different distances, 30mm is selected as the optimal reserved distance in the embodiment;
and 5, in the interaction module, the bottom surface, the outer rock soil and the outer bed rock are in a surface-surface contact pair type. Because the pile has large rigidity relative to rock soil, the pile is a main control surface, the rock soil is a subordinate surface, a face-to-face discrete method is adopted, and limited slippage is adopted in a contact tracking method of the pile and the soil body. The contact property between the pile and the rock-soil contact surface comprises two aspects, namely that a 'hard contact' is adopted in the normal direction and separation is allowed, and that a coulomb penalty rigidity algorithm is adopted in the tangential direction to determine the friction coefficient. Meanwhile, the bonding strength between the pile bottom of the lower section pile and the soil body is determined, and the bonding strength aims to ensure that the lower section pile is not easily pulled out in the pile top loading process;
and 6, determining pile soil boundary conditions in the load module. The top of the soil mass model is free edge unconstrained, the bottom of the soil mass model adopts fixed constraint, and the outer side of the soil mass model is radial displacement constraint; the top of the pile is free and unconstrained;
The soil body area close to the pile body is dense, and the soil body area far away from the pile body is sparse. The grid seeds are arranged according to the number, namely the number of the cells on the edge is directly filled. In this embodiment, the two-dimensional axisymmetric model selects a quadrilateral unit shape. The unit type is C3D8R, namely a node quadrilateral linear plane strain reduction integral unit, and the solving result of the unit type on the displacement is accurate.
step 8.1, carrying out soil body ground stress self-balancing, simulating the original state of a soil body, removing piles in the model, carrying out self-balancing analysis only on the soil body, applying displacement constraint to the side surfaces and the bottom surface of the piles and the soil, applying self-weight load to the soil body, carrying out soil body stress self-balancing calculation step by adopting Geostatic analysis, wherein the self-balancing convergence condition is that the soil body displacement is less than 10 -5 m；
And 8.2, in the load module, performing pile-soil contact calculation, wherein the pile-soil contact calculation is mainly used for simulating the load action of a soil body after pile forming on the pile. Adding a pile in the second Geostatic analysis step, canceling the displacement constraint of the pile and soil to enable the pile and the soil to be in contact, and simultaneously counting the influence of the self weight of the pile;
and 8.3, loading the pile body in the load module. In the Static General analysis step, upward uniform load is applied to the bottom of the upper section pile, and downward uniform load is applied to the top of the lower section pile, as shown in a in fig. 3;
8.4, in the load module, unloading the pile body in the newly-built Static General analysis step and applying uniform load for simulating the unloading stress state of the pile;
and 8.5, loading the pile top in the load module. In the newly-built Static General analysis step, downward uniform load is applied to the pile top of the upper section pile, and meanwhile, upward uniform load is applied to the pile top of the lower section pile, as shown in b in fig. 3.
And 9, in the task module, creating an analysis job and submitting calculation, then generating an inp calculation file, finding an error point when an error is calculated, and modifying the previous corresponding steps.
And step 10, in the visualization module, obtaining a reverse self-balancing pile test model and loading result information from a task module output database to obtain a foundation pile load-displacement curve chart, respectively obtaining the positive bearing capacity and the negative bearing capacity of the upper section of pile loaded and the lower section of pile loaded through the foundation pile load-displacement curve chart, and obtaining the ultimate bearing capacity of the foundation pile through a formula (1) and a formula (2).
Fig. 4 is a load-displacement curve diagram of an actual static load foundation pile of an engineering pile, and along with the slow change of the settlement of the pile top, the load of the pile top is gradually increased, and no load abrupt change point appears in the whole displacement curve, which is a typical slow-change curve, and the load corresponding to the displacement of 40mm is preferably selected, that is, Q =12844kN.
FIG. 5 is a load-displacement curve of a reverse self-balancing test interval of 30mm, and it can be seen from a in FIG. 5 that when the displacement of the pile bottom of the upper section of pile is increased to 12.17mm, the load of the pile bottom hardly changes with the increase of the vertical displacement of the pile bottom, which indicates that the bearing capacity of the upper section of pile reaches the limit value when the displacement is equal to 12.17mm, namely Q u - =3521kN; the load of the lower pile top is increased along with the gradual increase of the displacement of the lower pile top, the load displacement curve is a typical gradual change curve, and the ultimate bearing capacity of the load displacement curve is Q d + =7720kN. In fig. 5 b is a load-displacement curve under the loading of the pile jack in the reverse self-balancing test, for the loading of the upper pile jack, the ultimate bearing capacity displacement curve of the upper pile has an obvious inflection point, and the ultimate bearing capacity of the upper pile is a load corresponding to the displacement equal to 13.87mm, namely Q u + =3981kN, the displacement curve b in fig. 5 has obvious inflection points, and it is easy to judge that the lower pile limit bearing capacity is the load Q corresponding to the displacement equal to 9.74mm d - =4120kN, pile body dead weight G =1206kN. Reverse self-balancing ultimate load Q obtained by simulation experiment Press and press ＝Q u + +Q d + + G =12907kN. The difference between the reverse self-balancing and the static load ultimate bearing capacity of the engineering pile is 63KN and is within an allowable error range. Therefore, the simulation test method for obtaining the bearing capacity of the foundation pile based on the reverse self-balancing pile test method has certain feasibility.
TABLE 1 pile soil parameters
The above embodiments are only for illustrating the present invention and are not to be construed as limiting the present invention. Although the present invention has been described in detail with reference to the embodiments, it should be understood by those skilled in the art that various combinations, modifications or equivalents may be made to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention, and the technical solution of the present invention is covered by the claims of the present invention.
Claims (10)
1. A method for rapidly obtaining bearing capacity of a foundation pile based on a reverse self-balancing pile test method adopts abaqus software to simulate a reverse self-balancing pile test, and is characterized by comprising the following steps:
step 1, establishing a reverse self-balancing pile test model, determining the size of a foundation pile and the distribution of soil body parameters according to engineering pile field survey data in a component module of abaqus software, calculating or estimating the position of a pile balance point, establishing the reverse self-balancing pile test model, and selecting a deformable component according to the component type; the reverse self-balancing pile test model comprises an upper section pile, a lower section pile and a pile surrounding soil body;
step 2, determining material attributes of a pile foundation and a surrounding soil body according to engineering pile site survey data, and respectively endowing a pile body and a soil body around the pile with respective material parameters in an attribute module of abaqus software, wherein the pile body adopts a linear elastic model, and the soil body adopts an elastic-plastic model;
step 3, in an assembly module of abaqus software, assembling the created parts in a general coordinate system, and reserving a certain initial distance between an upper section of pile and a lower section of pile;
step 4, in an analysis step module of the abaqus software, two analysis steps are selected, one is a General Geostatic analysis step, the other is a General Static General analysis step, the Geostatic analysis step is mainly used for ground stress balance analysis, and the Static General analysis step is mainly used for pile-soil contact and pile loading analysis;
step 5, setting a contact interface type in an interaction module of the abaqus software;
step 6, determining boundary conditions of pile soil in a load module of abaqus software, wherein the top of a soil body model is free, free edges are unconstrained, the bottom of the soil body model is fixedly constrained, and the outer side of the soil body model is radially constrained in displacement; the top of the pile is free and unconstrained;
step 7, carrying out meshing on the built part in a mesh module of the abaqus software;
step 8, loading and analyzing, which specifically comprises the following steps:
8.1, removing the pile in the reverse self-balancing pile test model, performing ground stress analysis on the soil body only, applying displacement constraint on the side surface and the bottom surface of the pile and the soil, applying self-weight load on the soil body, and performing soil body stress self-balancing calculation by adopting Geostatic analysis stepping;
step 8.2, in the load module, performing pile-soil contact calculation to simulate the load action of a soil body after pile forming on the pile; adding a pile in the second Geostatic analysis step, canceling the displacement constraint of the pile and soil to enable the pile and the soil to be in contact, and simultaneously counting the influence of the self weight of the pile;
8.3, loading the pile body in the load module; in the Static General analysis step, upward uniform load is applied to the pile bottom of the upper section of pile, and downward uniform load is applied to the pile top of the lower section of pile;
8.4, in the load module, unloading the pile body in the newly-built Static General analysis step and applying uniform load for simulating the unloading stress state of the pile;
step 8.5, pile top loading is carried out in a load module, downward uniform load is applied to the pile top of the upper section of pile in a newly-built Static General analysis step, and meanwhile, upward uniform load is applied to the pile top of the lower section of pile, so that loading analysis of a reverse self-balancing test pile model is completed;
step 9, in the task module, creating an analysis job, submitting calculation, and then generating an inp calculation file;
and step 10, in a visualization module of abaqus software, acquiring a reverse self-balancing test pile model and loading analysis result information from a task module output database, and performing subsequent data processing analysis, wherein the subsequent data processing analysis comprises a contour cloud picture, a vector diagram, a grid deformation diagram and an XY curve diagram.
2. The method for rapidly obtaining the bearing capacity of the foundation pile based on the reverse self-balancing pile testing method according to claim 1, wherein the method comprises the following steps: in the step 1, the reverse self-balancing test pile model creation types comprise a three-dimensional model, a two-dimensional plane model and an axisymmetric space model, wherein the axisymmetric space model is half of the two-dimensional plane model.
3. The method for rapidly obtaining the bearing capacity of the foundation pile based on the reverse self-balancing pile testing method according to claim 2, wherein the method comprises the following steps: the reverse self-balancing test pile model is an axisymmetric space model, soil bodies around the pile are arranged in layers, the vertical direction of the soil body model is 1.5-3 times of the total length of the foundation pile, and the horizontal direction size of the soil body is 15-30 times of the diameter of the foundation pile.
4. The method for rapidly obtaining the bearing capacity of the foundation pile based on the reverse self-balancing pile testing method according to claim 1, wherein the method comprises the following steps: in step 2, parameters of material properties of the foundation pile comprise Young modulus, poisson's ratio and gravity; parameters of material attributes of the soil mass around the pile comprise Young modulus, poisson ratio, gravity, cohesive force and internal friction angle; and after the material parameters are input, defining interface attributes, and distributing the interface attributes to corresponding areas to realize material partitioning.
5. The method for rapidly obtaining the bearing capacity of the foundation pile based on the reverse self-balancing pile testing method according to claim 1, characterized by comprising the following steps: in step 3, a certain initial distance is reserved between the upper section of pile and the lower section of pile, and the load displacement curve of the upper section of pile is subjected to sudden change before the upper section of pile is contacted with the lower section of pile in the process of loading the pile top, wherein the certain initial distance is obtained through calculation or determined according to the loading analysis result in step 8.
6. The method for rapidly obtaining the bearing capacity of the foundation pile based on the reverse self-balancing pile testing method according to claim 1, wherein the method comprises the following steps: step 5, in the interaction module, the contact surface of the foundation pile and the rock soil adopts a surface-surface contact pair type; the pile is a main control surface, the rock soil is a subordinate surface, a face-to-face discrete method is adopted, and the contact tracking method of the pile and the soil body adopts limited slippage; the contact property between the pile and the rock-soil contact surface comprises two aspects, namely, the normal direction adopts the hard contact which allows separation, and the tangential direction adopts the coulomb penalty rigidity algorithm to determine the friction coefficient; and simultaneously, determining the bonding strength between the pile bottom of the lower section pile and the soil body.
7. The method for rapidly obtaining the bearing capacity of the foundation pile based on the reverse self-balancing pile testing method according to claim 1, wherein the method comprises the following steps: in the step 7, in the grid division process, the part close to the pile body is densely divided, and the part far away from the pile body is sparse; the pile and the soil body adopt C3D8R grid units, namely node quadrilateral linear plane strain reduction integral units.
8. The method for rapidly obtaining the bearing capacity of the foundation pile based on the reverse self-balancing pile testing method according to claim 1, characterized by comprising the following steps: in step 8.1, in the process of soil stress self-balancing calculation, the self-balancing convergence condition is that the soil displacement is less than 10 -5 m。
9. The method for rapidly obtaining the bearing capacity of the foundation pile based on the reverse self-balancing pile testing method according to claim 1, wherein the method comprises the following steps: in step 8.2, a plurality of Static General analysis steps are established to increase the load step by step.
10. The method for rapidly obtaining the bearing capacity of the foundation pile based on the reverse self-balancing pile testing method according to claim 1, characterized by comprising the following steps: in step 8.3 and step 8.5, the loading end condition is that any one of sudden change of the load displacement curve, damage of the upper section pile, damage of the lower section pile and damage of the soil body around the upper and lower piles occurs, and then the loading end condition is ended.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115879201A (en) * | 2022-12-20 | 2023-03-31 | 同济大学 | Permanent pile casing and analysis method for bearing capacity of sediment solidification hoisting cast-in-place pile |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH10153497A (en) * | 1996-11-21 | 1998-06-09 | Mitsubishi Heavy Ind Ltd | Foundation pile bearing power evaluation system |
| CN105735378A (en) * | 2016-04-11 | 2016-07-06 | 湖北工业大学 | Reverse self-balancing method for pile foundation vertical bearing capacity test and test device |
| CN106049559A (en) * | 2016-05-23 | 2016-10-26 | 中国十七冶集团有限公司 | Load-compensation-based large-diameter pile foundation self-balanced detecting method |
| US10823880B1 (en) * | 2020-03-10 | 2020-11-03 | Ramesh Chandra Gupta | Subsurface exploration using load tests on short model piles at various depths of a soil deposit for determining load-settlement relationship and engineering properties of soils and intermediate geomaterials |
| CN111894051A (en) * | 2020-07-31 | 2020-11-06 | 湖北工业大学 | Reverse self-balancing model test device and test method for pile foundation bearing capacity |
| CN113605467A (en) * | 2021-08-02 | 2021-11-05 | 湖北工业大学 | Pile foundation self-balancing test device with balance point compensation function and test method |
-
2022
- 2022-08-31 CN CN202211059400.0A patent/CN115233753A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH10153497A (en) * | 1996-11-21 | 1998-06-09 | Mitsubishi Heavy Ind Ltd | Foundation pile bearing power evaluation system |
| CN105735378A (en) * | 2016-04-11 | 2016-07-06 | 湖北工业大学 | Reverse self-balancing method for pile foundation vertical bearing capacity test and test device |
| CN106049559A (en) * | 2016-05-23 | 2016-10-26 | 中国十七冶集团有限公司 | Load-compensation-based large-diameter pile foundation self-balanced detecting method |
| US10823880B1 (en) * | 2020-03-10 | 2020-11-03 | Ramesh Chandra Gupta | Subsurface exploration using load tests on short model piles at various depths of a soil deposit for determining load-settlement relationship and engineering properties of soils and intermediate geomaterials |
| CN111894051A (en) * | 2020-07-31 | 2020-11-06 | 湖北工业大学 | Reverse self-balancing model test device and test method for pile foundation bearing capacity |
| CN113605467A (en) * | 2021-08-02 | 2021-11-05 | 湖北工业大学 | Pile foundation self-balancing test device with balance point compensation function and test method |
Non-Patent Citations (2)
| Title |
|---|
| 刘永莉等: "基桩承载力反向自平衡试桩法测试原理及数值模拟分析", 河海大学学报(自然科学版), pages 1 - 9 * |
| 巴军涛: "反向自平衡试桩法测试单桩承载力的试验研究", 中国优秀硕士学位论文全文数据库（电子期刊）-工程科技II辑, pages 038 - 626 * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115879201A (en) * | 2022-12-20 | 2023-03-31 | 同济大学 | Permanent pile casing and analysis method for bearing capacity of sediment solidification hoisting cast-in-place pile |
| CN115879201B (en) * | 2022-12-20 | 2023-09-05 | 同济大学 | Analysis method for permanent pile casing and sediment solidification and lifting cast-in-place pile bearing capacity |
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