CN114117592A - Method for analyzing grouting water-cement ratio of large-diameter cast-in-place pile based on ANSYS numerical simulation - Google Patents
Method for analyzing grouting water-cement ratio of large-diameter cast-in-place pile based on ANSYS numerical simulation Download PDFInfo
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Abstract
The invention discloses a method for analyzing the grouting water-cement ratio of a large-diameter cast-in-place pile based on ANSYS numerical simulation, which comprises the following steps of: step S1, modeling and simulation analysis of ANSYS; step S2, pile testing on site; step S3, comparing the ANSYS simulation result with the pile test result; and step S4, adjusting the ANSYS model to optimize the grouting parameters. The flow rate and grouting pressure of the grout, the cement consumption and the water cement ratio of the grout are connected with a grouting model; the purpose of adjusting grouting pressure, cement consumption and water cement ratio is achieved by adjusting the size of the pile end grouting model. After the ANSYS model is adjusted to obtain reasonable grouting parameters, the reasonable water-cement ratio which is consistent with the corresponding engineering geological condition is adopted for on-site post-grouting, so that the injection amount of the grout can be effectively ensured, and the loss of a large amount of grout is avoided; the cement consumption can be saved, the slurry hole string and the phenomenon caused by excessive cement injection amount are reduced, the construction safety is ensured, meanwhile, the construction cost is effectively reduced, the engineering quality is ensured, and the bearing capacity of the single pile is improved.
Description
Technical Field
The invention relates to a method for analyzing the grouting water-cement ratio of a large-diameter cast-in-place pile based on ANSYS numerical simulation, and belongs to the technical field of building construction.
Background
The post-grouting technology of the cast-in-place pile is listed as 10 new technologies in the construction industry for improving the bearing capacity of the pile foundation and obviously reducing the settlement of the pile foundation and is popularized and applied in China; however, due to the difference of geological conditions and the complexity of rock-soil properties, the water-cement ratio of cement slurry required to be used under different geological conditions is different, and once the water-cement ratio is not matched with the engineering geological conditions, the problems of hole crossing and slurry overflow are caused, so that slurry loss is caused;
in the method for determining the hole distance of the ultra-front deep hole grouting drilling in the complex surrounding environment with the Chinese patent publication No. CN111709065A, an ANSYS is used for establishing a model to determine the grouting pressure by using numerical simulation, however, the ANSYS is not used for obtaining a reasonable water-cement ratio which is consistent with the corresponding engineering geological condition by establishing the model, so that the water-cement ratio still cannot be matched with the engineering geological condition.
Disclosure of Invention
In order to solve the technical problems, the invention provides a method for analyzing the grouting water-cement proportion of a large-diameter cast-in-place pile based on ANSYS numerical simulation.
The invention is realized by the following technical scheme.
The invention provides a method for analyzing the grouting water-cement ratio of a large-diameter cast-in-place pile based on ANSYS numerical simulation, which comprises the following steps of:
step S1, modeling and simulation analysis of ANSYS;
step S2, pile testing on site;
step S3, comparing the ANSYS simulation result with the pile test result;
and step S4, adjusting the ANSYS model to optimize the grouting parameters.
Step S1, ANSYS modeling and simulation analysis:
in ANSYS numerical simulation software, a large-diameter cast-in-place pile model is modeled according to a completely equal proportion, and specifically comprises the steps S11 to S15.
Step S11, establishing a gridding model: ANSYS software can establish a qualified gridding model through a command stream mode.
Step S12, determining boundary conditions: the model adds dead weight and pile body top load according to actual conditions.
Step S13, assigning a model material characteristic value: and soil body combination and simplification are carried out.
Step S14, forming an initial ground stress field: and after the material parameters are endowed to the model by using the command stream, solving the stress field in the initial stress state by using a SOLVE solver.
Step S15, simulating a static load test to obtain a settlement result: and gradually loading the pile end in the model.
Step S2, field pile testing: before the engineering pile is completely unfolded and constructed, a test pile is constructed, post grouting construction is carried out on the test pile, low strain detection and ultrasonic detection are carried out on a pile body after the post grouting construction is finished, and the length of the pile and the integrity of the pile body are determined to meet the design requirements for carrying out static load test.
Step S3, comparing the ANSYS simulation result with the pile test result: and simulating the test pile load working condition through ANSYS to obtain the settlement of the pile end under different load grades and obtain the stress cloud charts of the pile body and the soil body under different load working conditions.
Step S4, adjusting ANSYS model optimization grouting parameters: according to the column type diffusion theory of the grouting body, the grout is injected into a sand soil body from a grouting hole, and the grout diffuses in a column type in the soil layer; according to Darcy's law, the flow rate and grouting pressure of the grout, the cement consumption and the water-cement ratio of the grout are connected with a grouting model; the purpose of adjusting grouting pressure, cement consumption and water cement ratio is achieved by adjusting the size of the pile end grouting model.
The invention has the beneficial effects that: after the ANSYS model is adjusted to obtain reasonable grouting parameters, the reasonable water-cement ratio which is consistent with the corresponding engineering geological condition is adopted for on-site post-grouting, so that the injection amount of the grout can be effectively ensured, and the loss of a large amount of grout is avoided; the cement consumption can be saved, the slurry hole string and the phenomenon caused by excessive cement injection amount are reduced, the construction safety is ensured, meanwhile, the construction cost is effectively reduced, the engineering quality is ensured, and the bearing capacity of the single pile is improved.
Drawings
FIG. 1 is a flow chart of the steps of the present invention;
FIG. 2 is an overall modeling diagram of the present invention;
FIG. 3 is a modeling diagram of the grout of the present invention;
FIG. 4 is a table of numerical simulation model parameters of the present invention;
FIG. 5 is a graph of the maximum imbalance force of the present invention;
FIG. 6 is a Z-direction stress cloud of the initial stress field of the present invention;
FIG. 7 is a cloud view of model subsidence during loading of the present invention;
FIG. 8 is a graph comparing simulated values to actual values for the curves of the present invention;
FIG. 9 is a graph comparing Q-S curves for different water-cement ratios according to the present invention;
FIG. 10 is a graph comparing the Q-S curves for different cement loadings according to the present invention.
Detailed Description
The technical solution of the present invention is further described below, but the scope of the claimed invention is not limited to the described.
As shown in fig. 1-10.
The invention discloses a method for analyzing the grouting water-cement ratio of a large-diameter cast-in-place pile based on ANSYS numerical simulation, which comprises the following steps of:
step S1, ANSYS modeling and simulation analysis:
in ANSYS numerical simulation software, modeling a large-diameter cast-in-place pile model according to a completely equal proportion;
wherein the soil body model adopts an MC elastic-plastic model, and the filling pile and the grouting material are established by adopting an elastic model; in the modeling process, the soil body is considered to be an isotropic elastoplastic body; in the numerical simulation process, post-grouting only considers the permeation and compaction effects and does not consider the splitting reinforcement effect; the pile end and the pile side consolidation body are simplified into a regular cylinder; simulating a contact surface between the pile wall and the soil body by using a contact surface unit; and pile top load is set to be uniformly distributed load during simulation static load test.
Step S11, establishing a gridding model: the ANSYS software has a powerful grid modeling function, a satisfactory grid model can be established in a command stream mode, the obtained overall modeling is shown in figure 2, and the obtained slurry modeling is shown in figure 3.
Step S12, determining boundary conditions: certain displacement constraints are added at the bottom and around the model to limit the translation, vertical displacement and rotation of the model. The model itself needs to add dead weight and pile body top load according to actual conditions.
Step S13, assigning a model material characteristic value: and selecting the most representative parameters for soil body combination and simplification according to the design drawing, the standard requirement and the geological survey data. According to the past engineering experience and the related data test results, the minimum value of the elastic modulus of the cement-soil consolidation body at the grouting end is 1770MPa, the strength of the consolidation body formed by field grouting is lower than that of a laboratory model, the elastic modulus of the model consolidation body is selected to be 1000MPa under the common condition, and the body calculation parameters are shown in figure 4.
Step S14, forming an initial ground stress field: after the material parameters are given to the model by using the command stream, solving a stress field in an initial stress state by using a SOLVE solver, ensuring that the stress of the model is in a convergence state, wherein the maximum unbalanced force in the calculation process is shown in FIG. 5; and verifying the reasonability of the model parameter setting, and obtaining a Z-direction stress cloud picture of the initial stress field after the calculation is completed, as shown in FIG. 6.
Step S15, simulating a static load test to obtain a settlement result: according to design requirements and the stress condition of a single pile, gradually applying load to the pile end in the model, and acquiring a Q-S curve of the post-grouting cast-in-place pile; the cloud pattern of model Z-direction subsidence during load application is shown in fig. 7.
Step S2, field pile testing: before the engineering pile is completely unfolded and constructed, 2 groups of test piles are constructed according to design requirements and corresponding parameters, post-grouting construction is carried out on the test piles according to drawing requirements, and the post-grouting construction process is recorded in detail; and after the post-grouting construction is finished, carrying out low strain detection and ultrasonic detection on the pile body, determining that the pile length and the integrity of the pile body meet the design requirements, then carrying out static load test according to the design requirements, and recording the test process and corresponding data.
Step S3, comparing the ANSYS simulation result with the pile test result: and simulating the test pile load working condition through ANSYS to obtain the settlement of the pile end under different load grades and obtain the stress cloud charts of the pile body and the soil body under different load working conditions. The comparison of the simulation result and the test pile result can find that: the curve change trend of the numerical simulation result of the single-pile static load test of the post-grouting cast-in-situ bored pile is basically consistent with that of the actual static load test result. The simulated value and the actual value have certain difference under certain loading conditions, and the difference values are within an acceptable range. The numerical simulation result of the post-grouting bored concrete pile through ANSYS is reliable and effective, the numerical simulation result is in accordance with the actual engineering, and a comparison graph of the Q-S curve simulation value and the actual value is shown in FIG. 8.
Step S4, adjusting ANSYS model optimization grouting parameters:
according to the column type diffusion theory of grouting body, the grouting soil layer is assumed to be homogeneous and isotropic, the grout is Newtonian fluid, the grout is injected into the sand body from the grouting hole, and the grout is column type diffused in the soil layer.
According to the law of darcy,
q＝KgAi (1-1)
wherein q represents a flow rate (cm) of the slurry per unit time3/s)；
Kg-the permeability coefficient (cm/s) of the slurry in the formation;
i-water conservancy gradient of the grout;
a-area of penetration section
According to the boundary condition (r ═ r)0When H is H; r ═ r1When h is h0) The following can be derived from the formula (1-1):
it is known that
Thus, there are:
middle A-area of penetration Cross section (cm)2)
a-length of column slurry (cm)
The flow rate and grouting pressure of the grout, the cement consumption and the water cement ratio of the grout and the like can be related to the grouting model by using the formula. The purpose of adjusting grouting pressure, cement consumption and water cement ratio is achieved by adjusting the size of the pile end grouting model.
Determining a reasonable water-cement ratio:
and analyzing the influence of post-grouting on the bearing capacity of the single pile by changing the water-cement ratio of the post-grouting slurry at the pile end. After the pile end rear grouting bored concrete pile is formed, the bearing capacity of the pile end is improved through the combined action of the rear grouting slurry and the pile end soil body. The water-cement ratio of the grouting slurry after the pile end is changed can influence the range and strength of the slurry penetrating into the soil body pores, and further influence the bearing capacity of a single pile.
Under the condition that other conditions are not changed, the influence of the water-cement ratio of the post-grouting slurry at the pile end on the bearing capacity of a single pile of the cast-in-place pile is analyzed by changing the water-cement ratio of the post-grouting slurry, and the influence of the water-cement ratio of the post-grouting slurry on the bearing capacity of the single pile is obtained, so that a Q-S curve comparison graph under different water-cement ratios is obtained, and is shown in FIG. 9.
The numerical simulation results show that:
the bearing capacity of the single pile is gradually increased along with the increase of the water-cement ratio from 0.35, and the bearing capacity of the single pile is reduced when a certain value is reached.
Aiming at the actual conditions of engineering geology, the single pile bearing capacity is the largest when the water-cement ratio is about 0.55-0.65.
When the water ash is small, the grouting slurry is viscous, although the slurry strength is high, the invasion and penetration capacity of the slurry to the soil body is weak, and the bearing capacity is reduced when the water ash reaches a certain degree.
With the increase of the water cement ratio, the fluidity of the cement slurry is increased, the invasion capacity to the soil body is enhanced, but the strength of the cement slurry is weakened after the cement slurry is combined with the soil body at the pile end.
The pile end back grouting bored concrete pile needs to select a proper water-cement ratio for construction aiming at soil bodies of different geological conditions so as to ensure that the bearing capacity of the pile end reaches the highest.
Determining the reasonable cement dosage:
under the condition that other conditions are not changed, the influence of the grouting cement consumption on the bearing capacity of a single pile of the post-grouting bored pile at the pile end is analyzed by changing the mechanical property and the action range of the grouting material at the pile end. The reinforcing form of the pile end back grouting bored concrete pile mainly depends on that the pile end back grouting slurry invades the surrounding soil body and is combined with the surrounding soil body to reinforce the soil body at the pile end, so that the pile end resistance of the bored concrete pile is increased.
The influence of the cement dosage on the bearing capacity of the single pile is analyzed by changing the dosage of the cement in the water injection slurry without changing other factors, and the curve shown in the following graph is obtained. The effect of cement dosage on the bearing capacity of a single pile is shown in figure 10.
It can be known that, with the increase of the cement consumption, the single pile bearing capacity of the post-grouting bored pile is higher. The positive effect of the cement dosage on the bearing capacity of the single pile is gradually reduced along with the increase of the cement dosage. Aiming at the engineering geological condition of software simulation, the single pile bearing capacity of the cement consumption of about 2.5t can meet the requirement. With the increase of the cement consumption, the penetration and diffusion capacity of the cement grout is weakened and the binding capacity with the surrounding soil body is reduced due to certain grouting pressure, so that the bearing capacity of the pile end is reduced.
After the ANSYS model is adjusted to obtain reasonable grouting parameters, the reasonable water-cement ratio which is consistent with the corresponding engineering geological condition is adopted for on-site post-grouting, so that the injection amount of the grout can be effectively ensured, and the loss of a large amount of the grout is avoided. Reasonable cement grout injection amount (2.5t) is adopted under the simulated geological condition, so that the cement consumption can be saved, the problems of grout string holes and grout bleeding caused by excessive cement injection amount are solved, the construction safety is ensured, meanwhile, the construction cost is effectively reduced, the engineering quality is ensured, and the bearing capacity of a single pile is improved.
The application records the implementation of the pile foundation originated from the new city project of Guiyang.
Claims (10)
1. A method for analyzing the grouting water-cement ratio of a large-diameter cast-in-place pile based on ANSYS numerical simulation is characterized by comprising the following steps:
step S1, modeling and simulation analysis of ANSYS;
step S2, pile testing on site;
step S3, comparing the ANSYS simulation result with the pile test result;
and step S4, adjusting the ANSYS model to optimize the grouting parameters.
2. The method for analyzing the grouting water-cement ratio of a large-diameter bored concrete pile based on ANSYS numerical simulation as claimed in claim 1, wherein the step S1, the ANSYS modeling and simulation analysis are: in ANSYS numerical simulation software, a large-diameter cast-in-place pile model is modeled according to a completely equal proportion, and specifically comprises the steps S11 to S15.
3. The method for analyzing the grouting water-cement ratio of the large-diameter bored concrete pile based on ANSYS numerical simulation as claimed in claim 2, wherein the step S11 of establishing the gridding model is: ANSYS software can establish a qualified gridding model through a command stream mode.
4. The method for analyzing the grouting water-cement ratio of the large-diameter bored concrete pile based on ANSYS numerical simulation as claimed in claim 2, wherein the step S12 of determining the boundary conditions is: the model adds dead weight and pile body top load according to actual conditions.
5. The method for analyzing the grouting water-cement ratio of the large-diameter cast-in-place pile based on ANSYS numerical simulation as claimed in claim 2, wherein the step S13 is to give the model material characteristic values as: and soil body combination and simplification are carried out.
6. The method for analyzing the grouting water-cement ratio of the large-diameter cast-in-place pile based on ANSYS numerical simulation as claimed in claim 2, wherein the step S14 is to form an initial ground stress field as follows: and after the material parameters are endowed to the model by using the command stream, solving the stress field in the initial stress state by using a SOLVE solver.
7. The method for analyzing the grouting water-cement ratio of the large-diameter bored concrete pile based on ANSYS numerical simulation as claimed in claim 2, wherein the step S15 of simulating the static load test obtains the settlement result as follows: and gradually loading the pile end in the model.
8. The method for analyzing the grouting water-cement ratio of the large-diameter bored concrete pile based on ANSYS numerical simulation as claimed in claim 1, wherein the step S2, the on-site pile testing: before the engineering pile is completely unfolded and constructed, a test pile is constructed, post grouting construction is carried out on the test pile, low strain detection and ultrasonic detection are carried out on a pile body after the post grouting construction is finished, and the length of the pile and the integrity of the pile body are determined to meet the design requirements for carrying out static load test.
9. The method for analyzing the grouting water-cement ratio of the large-diameter bored concrete pile based on ANSYS numerical simulation as claimed in claim 1, wherein step S3, the ANSYS simulation result is compared with the test pile result: and simulating the test pile load working condition through ANSYS to obtain the settlement of the pile end under different load grades and obtain the stress cloud charts of the pile body and the soil body under different load working conditions.
10. The method for analyzing the grouting water-cement ratio of the large-diameter bored concrete pile based on ANSYS numerical simulation as claimed in claim 1, wherein step S4, adjusting an ANSYS model to optimize grouting parameters: according to the column type diffusion theory of the grouting body, the grout is injected into a sand soil body from a grouting hole, and the grout diffuses in a column type in the soil layer; according to Darcy's law, the flow rate and grouting pressure of the grout, the cement consumption and the water-cement ratio of the grout are connected with a grouting model; the purpose of adjusting grouting pressure, cement consumption and water cement ratio is achieved by adjusting the size of the pile end grouting model.
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| WO2024019792A1 (en) * | 2022-07-21 | 2024-01-25 | Halliburton Energy Services, Inc. | Method of grout selection for long term integrity of anchoring piles |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2024019792A1 (en) * | 2022-07-21 | 2024-01-25 | Halliburton Energy Services, Inc. | Method of grout selection for long term integrity of anchoring piles |
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