Dynamic regulation and control method and system for protecting existing pile foundations around during foundation pit excavation

Abstract

The invention discloses a dynamic regulation and control method and system for protecting existing pile foundations on the periphery during excavation of a foundation pit, and the method comprises the steps: S1, building a three-dimensional finite element model of the foundation pit and the existing pile foundations on the side by adopting finite element software according to the foundation pit to be excavated; s2, simulating by adopting a three-dimensional finite element model, and establishing a deflection curve database; s3, grouting pipes are arranged on the periphery of the pile foundation, and the grouting pipes are connected with a grouting controller; s4, inputting the deflection curve database into a grouting controller as a grouting control standard; s5, along with the change of the excavation depth of the foundation pit, according to the deflection curve, the corresponding grouting controller controls the grouting pipe connected with the grouting controller to start and stop; and S6, according to a real-time value measured by the measuring instrument, the real-time value is compared with a calculated value of the point in the three-dimensional finite element model so as to correct the deflection curve database, and then the deflection curve database is input into the grouting controller. According to the method, additional deflection deformation of the existing pile foundation in the whole foundation pit excavation process can be accurately and dynamically regulated and controlled, and the bearing capacity is not affected.

Description

Technical Field

[0001] This invention relates to the field of pile foundation technology, specifically to a dynamic control method and system for protecting existing pile foundations in the surrounding area during foundation pit excavation. Background Technology

[0002] With the large-scale construction of urban infrastructure in my country, the impact of new facilities on existing facilities is inevitable. When excavation is carried out on the side of existing pile foundations, the pile foundations must have sufficient strength and stability. In order to ensure the normal and safe construction of tunnels, the problem of reinforcing and protecting existing pile foundations sometimes arises, especially in silty soil foundations with abundant groundwater and fluid plasticity. The unloading effect of excavation may cause additional deformation of the pile foundations on the side. Solutions to such problems include demolishing and rebuilding existing pile foundations and replacing pile foundations, but these solutions bring a series of engineering and economic problems. Therefore, reinforcing or isolating the area around the pile foundations is the current mainstream solution.

[0003] Currently, the solutions to the above problems, such as the structure disclosed in the authorization announcement number CN 221523658 U, "Anti-settlement Reinforcement Structure for Tunnels Passing Under Existing Pile Foundations," involve saturation reinforcement of the pile foundations. However, this approach fails to pre-judge the relationship between pile foundation deformation and tunnel construction distance and progress, and cannot be adjusted based on real-time construction conditions, thus lacking precision. While the application number 202111013706.8, "A Segmented Grouting Reinforcement Method for Existing Pile Foundations," achieves segmented reinforcement of the pile foundations in the depth direction, making it more precise, it still fails to integrate with real-time construction conditions and cannot achieve precise dynamic control.

[0004] In summary, current methods of grouting reinforcement for existing pile foundations and the construction of isolation piles between pile foundations and tunnels are still traditional passive reinforcement methods. These methods are somewhat haphazard, failing to anticipate the impact of construction and accurately control the reinforcement effect. Furthermore, if the reinforcement fails, it is difficult to adjust the original passive reinforcement method. In addition, traditional passive reinforcement methods are generally saturated, resulting in high consumption of grouting materials, higher costs, and longer construction periods. Extensive grouting work on the ground can also have adverse effects on the surrounding strata and environment.

[0005] Since the impact of foundation pit construction on existing pile foundations is a dynamic process, the deflection and curvature of the existing pile foundations are constantly changing during the excavation process. Therefore, a method for protecting existing pile foundations that can be dynamically, accurately, efficiently, and in real-time controlled throughout the entire dynamic process of foundation pit excavation is needed. Summary of the Invention

[0006] The primary objective of this invention is to overcome the shortcomings of the prior art and provide a dynamic control method for protecting existing pile foundations during foundation pit excavation. This dynamic control method for protecting existing pile foundations during foundation pit excavation can accurately and dynamically control the existing pile foundations to prevent additional deflection deformation throughout the entire foundation pit excavation process. It also avoids the problem of ineffective or excessive reinforcement of the pile foundations caused by inaccurate grouting pressure and timing.

[0007] The second objective of this invention is to provide a dynamic control system for protecting existing pile foundations in the surrounding area during foundation pit excavation.

[0008] The first objective of this invention is achieved through the following technical solution: a dynamic control method for protecting existing pile foundations in the surrounding area during the excavation of this foundation pit, comprising the following steps:

[0009] S1. Based on the site geological conditions of the foundation pit to be excavated, the horizontal net distance S between the foundation pit and the pile foundation, and the excavation depth H of the foundation pit, a three-dimensional finite element model of the foundation pit and the existing pile foundation on the side is established using finite element software.

[0010] S2. Obtain the deflection results of the pile foundation in the three-dimensional finite element model at different horizontal net distances S and different excavation depths H between the pile foundation and the foundation pit, and draw a series of deflection curves of the pile foundation and the foundation pit excavation depth H under different horizontal net distances S, and establish a deflection curve database.

[0011] S3. Grouting pipes are arranged around the pile foundation, and these grouting pipes are connected to the grouting controller.

[0012] S4. Input the deflection curve database into the grouting controller to serve as a standard for grouting control;

[0013] S5. As the depth of the foundation pit excavation changes, the measuring instrument automatically measures the horizontal net distance S and the excavation depth H, selects the deflection curve closest to the deflection curve database, and according to the deflection curve, the corresponding grouting controller will control whether the grouting pipe connected to it starts or stops grouting.

[0014] S6. A measuring instrument set at the top of the foundation pit measures the real-time displacement of the top of the pit after excavation, and compares the real-time value with the calculated value of that point in the three-dimensional finite element model:

[0015] If the deviation between the calculated value and the real-time value is greater than 10%, the geological and excavation parameters in the three-dimensional finite element model are corrected until the difference between the calculated value and the real-time value is less than or equal to 10%. Then, the corrected pile foundation deflection curve database is re-acquired and input into the grouting controller for subsequent grouting control.

[0016] Preferably, the three-dimensional finite element model in step S1 uses the birth and death element control method to simulate the foundation pit excavation process, including the following steps:

[0017] A. Based on the soil conditions of the specific engineering plan, establish a soil model, apply gravity, obtain the stress and deformation of the soil under its own weight, and export and save it as an initial geostress file.

[0018] B. Establish a model of the interaction between soil, pile foundation, and foundation pit, and import the initial stress file;

[0019] C. Kill the soil units inside the foundation pit step by step to simulate the stress release during the foundation pit excavation process.

[0020] Preferably, the finite element software is MIDAS GTS software.

[0021] Preferably, in step S2, the horizontal axis is set to the deflection value of the pile foundation and the vertical axis is set to the depth elevation of the pile foundation. According to different excavation depths H, a series of deflection curves of the pile foundation and the excavation depth H are plotted under different horizontal net distances S, and a deflection curve database is established.

[0022] Preferably, the site geological conditions include stratum thickness and geotechnical parameters.

[0023] Preferably, in step S3, at least two grouting pipes are arranged around the pile foundation.

[0024] The second objective of this invention is achieved through the following technical solution: a dynamic control system for protecting existing pile foundations during foundation pit excavation, comprising:

[0025] The data acquisition module is used to collect site geological conditions, the horizontal net distance S between the foundation pit and the pile foundation, the excavation depth H of the foundation pit, and the displacement of the measuring instrument's location;

[0026] The data processing module is used to calculate the deflection results of the pile foundation at different horizontal net distances S and different excavation depths H from the foundation pit, the relationship between different horizontal net distances S and foundation pit excavation depths H, and to establish a deflection curve database.

[0027] The execution module selects the corresponding deflection curve from the deflection curve database based on the real-time data collected by the data acquisition module to determine whether grouting is necessary.

[0028] The correction module determines whether there is an error between the calculated value and the actual deformation based on the displacement of the measuring instrument's location, corrects the corresponding deflection curve, and feeds the corrected deflection curve back to the execution module.

[0029] The present invention has the following advantages over the prior art:

[0030] (1) This invention fundamentally abandons the traditional saturation-type reinforcement and blind reinforcement methods for existing pile foundations, and greatly improves the efficiency and accuracy of existing pile foundation reinforcement.

[0031] (2) As the foundation pit is continuously excavated, the deflection of the existing pile foundation also changes. This invention can realize real-time dynamic control of the reinforcement of the existing pile foundation.

[0032] (3) The present invention can maintain the existing pile foundation without additional deflection deformation throughout the process, and does not affect its bearing capacity. It also avoids the ineffective reinforcement or additional deformation during the reinforcement process caused by inaccurate grouting pressure and timing.

[0033] (4) The grouting material of the present invention has low loss, lower cost and shorter construction period, and is more convenient and environmentally friendly than the existing solution. Attached Figure Description

[0034] Figure 1 This is a flowchart of the dynamic control method for protecting the surrounding existing pile foundations during the excavation of the foundation pit according to the present invention.

[0035] Figure 2 This is a three-dimensional view after grouting of the dynamic control method for protecting the surrounding existing pile foundations during the excavation of the foundation pit according to the present invention.

[0036] Figure 3 This is a side view after grouting of the dynamic control method for protecting the surrounding existing pile foundations during the excavation of the foundation pit according to the present invention.

[0037] Figure 4 This is a three-dimensional diagram of pile foundations and foundation pit excavation at different horizontal net distances after grouting using the method of this invention (when the foundation pit excavation is relatively shallow).

[0038] Figure 5 This is a three-dimensional diagram of pile foundations and foundation pit excavation at different horizontal net distances after grouting using the method of this invention (when the foundation pit excavation is relatively deep).

[0039] Figure 6 These are a series of deflection curves of the pile foundation and the excavation depth H using the method of this invention (when the horizontal net distance S is H).

[0040] Figure 7 These are a series of deflection curves of the pile foundation and the excavation depth H using the method of this invention (when the horizontal net distance S is 0.5H).

[0041] Wherein, 1 is the pile foundation, 2 is the foundation pit, 3 is the grouting controller, 4 is the grouting pipe, 5 is the grouting body, 6 is the measuring instrument, S is the horizontal net distance between the foundation pit and the pile foundation, and H is the excavation depth of the foundation pit. Detailed Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0043] like Figure 1 As shown, the dynamic control method for protecting the surrounding existing pile foundations during foundation pit excavation includes the following steps:

[0044] S1. Based on the site geological conditions of the foundation pit to be excavated, the horizontal net distance S between the foundation pit and the pile foundation, and the excavation depth H of the foundation pit, a three-dimensional finite element model of the foundation pit and the existing pile foundation on the side is established using finite element software.

[0045] Specifically, the finite element method software used in this embodiment is MIDAS GTS. The selection of the finite element method depends on the site geological conditions of the excavation pit, such as soil layer thickness and geotechnical parameters, the horizontal clearance S between the pit and the pile foundation, and the excavation depth H. Site geological conditions are a key factor to consider throughout the construction process; differences in soil layer thickness and geotechnical parameters will affect subsequent construction operations. Soil layer thickness can range from several meters to tens of meters, while geotechnical parameters encompass various aspects such as soil density, porosity, and shear strength. The magnitude of the horizontal clearance S between the pit and the pile foundation and the excavation depth H determine the initial state of the impact on the pile foundation during the excavation process.

[0046] S2. Obtain the deflection results of the pile foundation at different horizontal clearances S and different excavation depths H in the three-dimensional finite element model, and draw a series of deflection curves of the pile foundation and the excavation depth H at different horizontal clearances S, and establish a deflection curve database; In step S2, let the horizontal axis be the deflection value of the pile foundation and the vertical axis be the depth elevation of the pile foundation. According to different excavation depths H, draw a series of deflection curves of the pile foundation and the excavation depth H at different horizontal clearances S, and establish a deflection curve database.

[0047] like Figure 6 , 7 As shown, this is a very simple deflection curve database, in which Figure 6 When the horizontal clearance S is taken as H, a series of deflection curves for the pile foundation and the excavation depth H show that the impact on the pile foundation is relatively limited at this horizontal clearance. As the excavation depth H increases, although the displacement of the pile foundation, especially the top, continues to increase, the trend of the curves remains stable. However, if... Figure 7 When the horizontal clearance S is 0.5H, the pile foundation is relatively close to the foundation pit. As the foundation pit is excavated to a certain depth, the deflection curve of the pile foundation tends to "bulge out". Therefore, both the horizontal clearance S and the excavation depth H will affect the development of the deflection curve. It is necessary to use the controlled variable method and list all the required deflection curves according to the actual needs of the project.

[0048] These data and curves are of great significance for the grouting controller to accurately determine the deformation state of the pile foundation and carry out corresponding grouting operations.

[0049] Obtaining these results requires detailed data analysis of the finite element model. The mechanical properties of pile foundations differ at different depths. For example, shallow pile foundations may be more susceptible to surface loads and surface deformation caused by excavation, while deeper pile foundations are more affected by changes in the stress of the surrounding soil. The deflection curve results reflect the horizontal deformation of the pile foundation. The deflection curve database can visually display the deformation pattern of the pile foundation as the horizontal clearance S and excavation depth H change. This process requires precise calculations and data processing to ensure that the curves accurately reflect the actual situation.

[0050] To further improve the accuracy of the curve, the three-dimensional finite element model in this embodiment uses the birth and death element control method to simulate the foundation pit excavation process, including the following steps:

[0051] A. Based on the soil conditions of the specific engineering plan, establish a soil model, apply gravity, obtain the stress and deformation of the soil under its own weight, and export and save it as an initial geostress file.

[0052] B. Establish a model of the interaction between soil, pile foundation, and foundation pit, and import the initial stress file;

[0053] C. Kill the soil units inside the foundation pit step by step to simulate the stress release during the foundation pit excavation process.

[0054] S3. Grouting pipes are arranged around the pile foundation, and these grouting pipes are connected to grouting controllers. In this embodiment, grouting pipes are set on both sides of the pile foundation, and each grouting pipe is equipped with a separate grouting controller. Specifically, the number of grouting pipes can be determined according to the actual situation. For example, multiple grouting pipes can be arranged on both sides near and far from the foundation pit according to the actual project conditions and pile foundation size to enhance the reinforcement effect. Figures 2-5 As shown.

[0055] S4. Input the deflection curve database into the grouting controller to serve as a standard for grouting control. This is also a key step in achieving dynamic control.

[0056] S5. As the depth of the foundation pit excavation changes, the measuring instrument automatically measures the horizontal net distance S and the excavation depth H, selects the deflection curve closest to the deflection curve database, and according to the deflection curve, the corresponding grouting controller will control whether the grouting pipe connected to it starts or stops grouting.

[0057] The initial state of the pile foundation with no deflection serves as a baseline. As the foundation pit is excavated, the deflection gradually changes. Figure 4 and 6Taking H=3.0m as an example in section 7, since the initial excavation is relatively shallow, the top of the pile foundation undergoes significant deformation. The displacement of the top of the pile foundation closer to the excavation pit is also greater than that of the pile foundation farther away. At this time, the grouting controller for the closer pile foundation will control the grouting pipe to grout at the elevation where the top of the pile foundation exhibits significant deflection, thus forming a grout body. The pile foundation farther away is less affected and does not activate grouting at this excavation depth.

[0058] However, as the excavation depth H of the foundation pit increases, with Figure 5 and 6 In Example 7, when H = 15.0m, the deflection trend of piles farther apart remains stable, with the largest displacement still occurring at the top. Therefore, as the foundation pit is excavated, the grouting controller will control the grouting pipe to inject grout at the top of the pile. However, for piles closer together, due to changes in the deflection curve trend, the deflection curve of the pile will show a "bulging" trend, and the bottom of the pile will displace away from the foundation pit, showing an overall tendency to tilt towards the inside of the foundation pit. Therefore, as the foundation pit is excavated, the grouting controller will control the grouting pipe to continuously inject grout in the middle of the "bulging" pile, and when the bottom shows a reverse displacement, the grouting controller on the other side will control the grouting pipe to inject grout at its bottom to resist the tilting tendency of the pile.

[0059] Before excavating the foundation pit, all grouting controllers must be activated and mortar connected. The measuring instrument will automatically and dynamically adjust the grouting pipes in real time based on the measured distance between the pile foundation and the foundation pit, as well as the excavation depth. The grouting controller selects the corresponding deflection curve from the deflection curve database based on the current horizontal clearance S and excavation depth H. The grouting controller in the deflection direction will activate the grouting pipe, applying pressure to the pile foundation in the opposite direction. As the foundation pit approaches, the grouting controller will reassess and select a closer deflection curve. If the pile foundation deflection curve continues to develop in that direction, the grouting controller in that direction will continue to activate. If the pile foundation deflection curve develops in the opposite direction, such as when the bottom of the pile foundation may displace away from the foundation pit, the grouting controller in the opposite deflection direction will activate, and the grouting controller in the deflection direction will deactivate. This process is repeated until the foundation pit excavation is completed and stabilized, at which point all grouting controllers are deactivated. This means that by calculating the pile foundation deflection change curve affected by the foundation pit excavation in advance, and then performing real-time dynamic grouting on the pile foundation according to the curve, the purpose of actively controlling the development of pile foundation deflection can be achieved.

[0060] S6. A measuring instrument set at the top of the foundation pit measures the real-time displacement of the top of the pit after excavation, and compares the real-time value with the calculated value of that point in the three-dimensional finite element model:

[0061] If the deviation between the calculated value and the real-time value is greater than 10%, the geological and excavation parameters in the three-dimensional finite element model are corrected until the difference between the calculated value and the real-time value is less than or equal to 10%. Then, the corrected pile foundation deflection curve database is re-acquired and input into the grouting controller for subsequent grouting control.

[0062] There will be some error between finite element calculations and actual conditions. Therefore, by using a monitoring point at the top of the foundation pit, a parameter inversion can be performed. If the difference is large, the model parameters need to be adjusted and the monitoring values ​​refitted.

[0063] Activating the grouting controller before excavation is a preventative measure. After connecting the mortar, the grouting controller begins its dynamic control function. First, it determines the direction of deflection based on the measured distance between the pile foundation and the pit, combined with the previously input deflection curve. Once the deflection direction is determined, the corresponding grouting pipe is activated to inject grout, applying pressure in the opposite direction to the pile foundation to resist the effects of excavation. As the excavation deepens, the construction environment constantly changes, requiring the grouting controller to re-evaluate and select a new deflection curve. If the deflection curve of the upper pile foundation continues to move towards the pit, the original grouting operation needs to be strengthened, and the grouting controller for the deflection direction will continue operating. If the deflection curve of the lower pile foundation moves away from the pit, the grouting controller on the other side needs to be activated to grout the lower pile foundation. This process needs to be repeated until the pile foundation structure stabilizes, at which point all controllers are deactivated. This real-time dynamic grouting method based on deflection curves effectively and proactively controls the deflection development of the pile foundation, ensuring the stability of existing pile foundations during excavation.

[0064] A dynamic control system to protect the surrounding existing pile foundations during foundation pit excavation includes:

[0065] The data acquisition module is used to collect site geological conditions, the horizontal net distance S between the foundation pit and the pile foundation, the excavation depth H of the foundation pit, and the displacement of the measuring instrument's location;

[0066] The data processing module is used to calculate the deflection results of the pile foundation at different horizontal net distances S and different excavation depths H from the foundation pit, the relationship between different horizontal net distances S and foundation pit excavation depths H, and to establish a deflection curve database.

[0067] The execution module selects the corresponding deflection curve from the deflection curve database based on the real-time data collected by the data acquisition module to determine whether grouting is necessary.

[0068] The correction module determines whether there is an error between the calculated value and the actual deformation based on the displacement of the measuring instrument's location, corrects the corresponding deflection curve, and feeds the corrected deflection curve back to the execution module.

[0069] The above-described specific embodiments are preferred embodiments of the present invention and are not intended to limit the present invention. Any other changes or equivalent substitutions made without departing from the technical solution of the present invention are included within the protection scope of the present invention.

Claims

1. A dynamic control method for protecting existing pile foundations in the surrounding area during excavation of a foundation pit, characterized by, The method comprises the following steps: S1, according to the site geological conditions of the foundation pit to be excavated, the horizontal distance S between the foundation pit and the pile foundation, and the excavation depth H of the foundation pit, a three-dimensional finite element model of the foundation pit and the existing pile foundation on the side is established by using a finite element software; S2, the deflection results of the pile foundation in the three-dimensional finite element model at different horizontal distances S from the foundation pit and different excavation depths H are obtained, a series of deflection curves of the pile foundation and the excavation depth H of the foundation pit at different horizontal distances S are drawn, and a deflection curve database is established; S3, a grouting pipe is arranged around the pile foundation, and the grouting pipe is connected with a grouting controller; S4, the deflection curve database is input into the grouting controller to serve as a standard for grouting control; S5, as the excavation depth of the foundation pit changes, the measuring instrument automatically measures the horizontal distance S and the excavation depth H, selects the closest deflection curve in the deflection curve database, and according to the deflection curve, the corresponding grouting controller controls whether the grouting pipe connected therewith starts or stops grouting; S6, the measuring instrument arranged on the top of the foundation pit measures the real-time value of the displacement of the top of the foundation pit after excavation, and the real-time value is compared with the calculated value of the point in the three-dimensional finite element model: If the deviation between the calculated value and the real-time value is greater than 10%, the geological and excavation parameters in the three-dimensional finite element model are corrected until the difference between the calculated value and the real-time value is less than or equal to 10%, the corrected pile foundation deflection curve database is re-obtained, and the corrected deflection curve database is input into the grouting controller for subsequent grouting control.

2. The method of dynamic control for protecting existing pile foundations during excavation of a foundation pit according to claim 1, wherein, The three-dimensional finite element model in step S1 simulates the process of foundation pit excavation by using the birth-death element control method, which comprises the following steps: A, a soil model is established according to the soil layer conditions of the specific engineering scheme, gravity is applied, and the stress and deformation of the soil under its own weight are obtained as an initial stress file to be exported and saved; B, a model of the interaction of soil, pile foundation and foundation pit is established, and the initial stress file is read in; C, the soil units inside the foundation pit are killed step by step to simulate the stress release in the process of foundation pit excavation.

3. The method of dynamic control for protecting existing pile foundations during excavation of a foundation pit according to claim 1, wherein, The site geological conditions include stratum thickness and geotechnical parameters.

4. The method of dynamic control for protecting existing pile foundations during excavation of a foundation pit according to claim 1, wherein, The finite element software is MIDAS GTS software.

5. The method of dynamic control for protecting the existing pile foundation during the excavation of a foundation pit according to claim 1, wherein, In step S2, the horizontal coordinate is the deflection value of the pile foundation, the vertical coordinate is the depth elevation of the pile foundation, a series of deflection curves of the pile foundation and the excavation depth H at different horizontal distances S are drawn according to different excavation depths H, and a deflection curve database is established.

6. The method of dynamic control for protecting existing pile foundations during excavation of a foundation pit according to claim 1, wherein, The number of grouting pipes arranged around the pile foundation in step S3 is at least 2.

7. A dynamic control system for protecting existing pile foundations during excavation of a foundation pit, characterised in that, It comprises: a data acquisition module for acquiring the site geological conditions, the horizontal distance S between the foundation pit and the pile foundation, the excavation depth H of the foundation pit, and the displacement of the position of the measuring instrument; a data processing module for calculating the deflection results of the pile foundation at different horizontal distances S from the foundation pit and different excavation depths H, the relationship between different horizontal distances S and the excavation depth H of the foundation pit, and establishing a deflection curve database; an execution module for selecting the corresponding deflection curve in the deflection curve database according to the real-time data acquired by the data acquisition module to determine whether to grout. The correction module determines whether there is an error between the calculated value and the actual deformation based on the displacement of the position where the measuring instrument is located, corrects the corresponding deflection curve, and feeds back the corrected deflection curve to the execution module.

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