Dynamic regulation and control method for protecting existing pile foundation on side during shield tunneling

Abstract

The invention discloses a dynamic regulation and control method for protecting an existing pile foundation on the side during shield tunneling. The method comprises the steps that S1, a three-dimensional finite element model of a shield tunnel and an existing bridge pile foundation is established; s2, a deflection curve of the deflection of the pile foundation and the longitudinal horizontal clear distance is obtained and drawn; s3, the deflection change range of the pile foundation in the depth is determined to set the height of a grouting body; s4, grouting pipes and grouting controllers are arranged around the pile foundation; s5, the deflection curve is input into a grouting controller; and S6, the grouting pipe is automatically and dynamically adjusted in real time for grouting. Compared with a saturation type and blind type reinforcing mode of a traditional existing pile foundation, the method has the advantages that the existing pile foundation can be accurately and dynamically regulated and controlled to generate no additional deflection deformation in the whole shield lateral penetration process, and the bearing capacity of the pile foundation is not affected. The method is more accurate, efficient, convenient and environment-friendly, and the problem of additional deformation caused by invalid reinforcement or excessive reinforcement of the pile foundation due to inaccurate grouting pressure and time is also avoided.

Description

Technical Field

[0001] The present invention relates to the field of existing pile foundation reinforcement engineering, and in particular to a dynamic control method for protecting lateral existing pile foundations during shield tunneling. Background Art

[0002] With the large-scale construction of urban infrastructure in my country, the spatial overlap of new and existing facilities is inevitable. When tunnels are constructed alongside existing pile foundations, the pile foundations must possess sufficient strength and stability. To ensure normal and safe tunnel construction, the reinforcement and protection of the existing pile foundations sometimes present challenges. This is particularly true in sandy soils with abundant groundwater and poor adhesion. The unloading effect of tunnel excavation may cause additional settlement of the upper pile foundations. Solutions to address these issues include dismantling and rebuilding the existing pile foundations or replacing them, but these solutions bring a series of engineering and economic problems. Therefore, reinforcement or isolation around the pile foundations is currently the mainstream solution.

[0003] At present, solutions to the above problems include the structure disclosed in the "Anti-settlement reinforcement structure for tunnels under existing pile foundations" with authorization announcement number CN 221523658 U, which performs saturated reinforcement on the pile foundations. It does not prejudge the relationship between the deformation of the pile foundation and the distance and progress of tunnel construction, nor can it be adjusted according to the real-time construction situation, which is not accurate enough. Although the "A segmented grouting reinforcement method for existing pile foundations" with application number 202111013706.8 achieves segmentation of pile foundation reinforcement in the depth direction, which is more accurate, it still fails to combine it with the real-time construction situation and still cannot achieve accurate dynamic braking.

[0004] In summary, current methods of grouting existing pile foundations and installing isolation piles between pile foundations and tunnels are still traditional passive reinforcement methods. These methods are relatively blind, fail to predict the impact of construction, and cannot accurately assess the reinforcement effect. Moreover, if the reinforcement fails during this process, the original passive reinforcement method is difficult to adjust. In addition, traditional passive reinforcement methods are generally saturated, resulting in high grouting material loss, higher costs, and longer construction periods. Moreover, the large amount of grouting work on the ground will affect the operation of existing roads and the use of buildings.

[0005] Because the impact of shield construction on existing pile foundations is a dynamic process, the deflection of the existing pile foundations constantly changes as the cutterhead approaches and moves away from the pile foundations. Therefore, a method for protecting existing pile foundations that can be accurately, efficiently, and controlled in real time throughout the dynamic process of shield construction is needed. Summary of the Invention

[0006] The purpose of the present invention is to address the deficiencies of the prior art and provide a dynamic control method for protecting existing pile foundations on the side during shield tunneling.

[0007] In order to achieve the above object, the technical solution of the present invention is:

[0008] A dynamic control method for protecting existing pile foundations on the side during shield tunneling, comprising the following steps:

[0009] S1: Based on the site geological conditions of the tunnel to be excavated, the longitudinal horizontal clearance S between the shield machine and the pile foundation, and the transverse horizontal clearance D between the shield machine and the pile foundation, a three-dimensional finite element model of the entire construction process of the shield tunnel side-penetrating the pile foundation is established using finite element software. The longitudinal horizontal clearance S of the pile foundation generally ranges from 9m before to 9m after the pile foundation is crossed.

[0010] S2: Obtain the longitudinal and transverse deflection results of the pile foundation at different depths in the finite element model established in step S1, and draw a deflection curve of the longitudinal and transverse deflections of the pile foundation and the longitudinal and horizontal clear distance S according to the change of the longitudinal and horizontal clear distance S between the shield machine and the pile foundation during the process;

[0011] S3: According to the deflection curve in step S2, the deflection variation range H of the pile foundation in depth is obtained;

[0012] S4: Arrange grouting pipes and grouting controllers around the pile foundation, and set the height of the corresponding grouting body according to the deflection variation range H in step S3;

[0013] S5: Input the deflection curve in step S2 into the grouting controller;

[0014] S6: Based on the deflection curve, the grouting controller will control whether the grouting pipe starts grouting. Under the joint regulation of several grouting pipes around the pile foundation, it is ensured that the grouting pressure is always applied in the opposite direction of the deflection curve to offset the deflection induced by the shield clearance, thereby maintaining the stability of the pile foundation.

[0015] Furthermore, multiple grouting pipes around the pile foundation can be arranged in parallel and vertical directions according to actual engineering conditions and pile foundation dimensions to enhance the reinforcement effect.

[0016] Furthermore, the grouting controller is located at the top of the grouting pipe. Each grouting controller independently controls the grouting pipe below it, so that each grouting pipe can be grouted separately. The grouting pipes in different directions are used in combination to achieve real-time regulation of the pile foundation deflection during the entire dynamic construction process to maintain its neutrality.

[0017] Furthermore, the grouting controller can measure the longitudinal horizontal clear distance S between the shield machine and the pile foundation in real time.

[0018] Furthermore, the grouting controller will select the corresponding or closest deflection curve according to the measured longitudinal horizontal clear distance S, so as to judge the upcoming deflection change of the pile foundation and control each grouting pipe to perform grouting.

[0019] Furthermore, in step S2, the deflection curve, with the abscissa being the deflection value of the pile foundation and the ordinate being the depth elevation of the pile foundation, is plotted as multiple curves based on different longitudinal horizontal clearance distances S between the shield machine and the pile foundation. This means that the deflection curves of the pile foundation at different longitudinal distances between the shield machine and the pile foundation are obtained and used as a standard for regulating grouting.

[0020] Furthermore, in step S2, the more deflection curves there are, the more accurate and precise the grouting control is, but at least three deflection curves before, during and after the shield machine passes through the pile foundation are required to achieve dynamic control of the grouting during the entire side-penetrating process.

[0021] Furthermore, the height of the grouting body in S4 corresponds to the height within the allowable deflection range of the pile foundation, and can be adjusted according to the actual conditions of the pile foundation and the allowable deflection value.

[0022] Furthermore, the three-dimensional finite element model in step S1 uses the life-death unit control method to simulate the shield excavation process, as follows:

[0023] a) Establish a soil model based on the soil layer conditions of the specific engineering plan, apply gravity, and obtain the stress and deformation of the soil under its own weight, which will be exported and saved as an initial geostress file;

[0024] b) Establish a model of the interaction between soil, pile foundation and shield, and read in the initial ground stress file;

[0025] c) Kill some soil units in the excavated tunnel, simulate the tunnel surrounding rock stress release by 25%, apply 75% of the initial stress to the soil around the excavated tunnel in the reverse direction, and apply 0.15 MPa shield tail grouting pressure at the same time;

[0026] d) After simulating a 75% release of ground stress, 25% of the initial stress was applied to the soil around the excavated tunnel in the reverse direction, while shield tail grouting pressure was applied at the same time;

[0027] e) Simulate the complete ground stress and only apply the shield tail grouting pressure to the soil around the excavated tunnel;

[0028] f) Cancel the grouting pressure and activate the lining structure and grouting layer units.

[0029] Preferably, the finite element software in step S1 is MIDAS GTS software.

[0030] Compared with the prior art, the present invention has the following significant effects:

[0031] (1) The present invention fundamentally abandons the traditional saturated reinforcement and blind reinforcement methods of existing pile foundations, greatly improving the efficiency and accuracy of existing pile foundation reinforcement.

[0032] (2) As the cutterhead of the shield machine continuously approaches and moves away from the pile foundation, the deflection of the existing pile foundation also changes accordingly. The present invention can realize real-time dynamic regulation of the reinforcement of the existing pile foundation.

[0033] (3) The present invention can maintain the existing pile foundation without generating additional deflection and deformation throughout the entire process, without affecting its bearing capacity. It also avoids inaccurate grouting pressure and timing that may lead to ineffective reinforcement or additional deformation during the reinforcement process.

[0034] (4) The grouting material of the present invention has a small loss, a lower cost and a shorter construction period, and is more convenient and environmentally friendly than existing solutions. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] Figure 1 is a flow chart of a method according to an embodiment of the present invention;

[0037] Figure 2 This is a three-dimensional diagram of an embodiment of the present invention before grouting;

[0038] Figure 3 It is a plan view of the position relationship between the shield machine and the pile foundation;

[0039] Figure 4 It is the position relationship between the shield machine and the pile foundation after grouting, as well as the elevation diagram of the grouting body height;

[0040] Figure 5 It is a three-dimensional diagram of the grouting pipe, grouting controller and shield machine;

[0041] Figure 6 is a lateral deflection curve of an embodiment of the present invention;

[0042] Figure 7 is the longitudinal deflection curve of the embodiment of the present invention.

[0043] In the figure: 1—shield machine; 2—shield tunnel; 3—superstructure; 4—pile foundation; 5—grouting controller; 6—grouting pipe; 7—grouting body; S—longitudinal horizontal clear distance between shield machine and pile foundation; D—lateral horizontal clear distance between shield machine and pile foundation; H—grouting height. DETAILED DESCRIPTION

[0044] like Figure 1 As shown, this embodiment discloses a dynamic control method for protecting existing pile foundations on the side during shield tunneling. Figure 2 It is a schematic diagram of a shield tunnel using the present invention passing through an existing pile foundation project.

[0045] S1: According to the geological conditions of the tunnel site to be excavated, such as the thickness of the stratum and geotechnical parameters, the longitudinal horizontal clearance S between the shield machine and the pile foundation, and the transverse horizontal clearance D between the shield machine and the pile foundation, the plan and elevation drawings and the distance position relationship between the two are as follows: Figure 3 、 4 As shown in the figure, the site geological conditions are key considerations throughout the construction process. Differences in stratum thickness and geotechnical parameters will impact subsequent construction operations. Stratum thickness can range from several meters to tens of meters, and geotechnical parameters encompass soil density, porosity, shear strength, and other aspects. The longitudinal and transverse horizontal clearances S and D between the shield machine and the pile foundation determine the initial impact of the shield machine on the pile foundation during excavation. Using the finite element software MIDAS GTS, an appropriate soil size was selected, and meshes and constraints were established. A three-dimensional finite element model of the entire construction process of the shield tunnel through the pile foundation was constructed. Excavation was performed using 1.5-meter segments, simulating the changes in pile foundation deflection as the shield machine approached and then moved away from the pile foundation. When selecting the soil size, it is important to comprehensively consider the soil distribution range in actual projects. The size should not be too large, which increases the computational complexity, nor too small, which may result in the model not accurately reflecting the actual situation. Model meshing is a delicate process, and the density of the mesh affects the accuracy of the finite element calculations. A sparse mesh can lead to inaccurate results, while a dense mesh significantly increases calculation time. The excavation setting of 1.5m segments is based on actual shield construction techniques. This simulation can more realistically reflect the impact of the shield machine on the pile foundation at different stages of excavation.

[0046] S2: Obtain the longitudinal and transverse deflection results of the pile foundation at different depths in the finite element model established in step S1. Based on the changes in the longitudinal and horizontal clearance distance S between the shield machine and the pile foundation during the process, ultimately plot the deflection curves of the longitudinal and transverse deflections of the pile foundation and the longitudinal and horizontal clearance distance S. Obtaining these results requires detailed data analysis of the finite element model. Pile foundations at different depths have different mechanical properties. For example, shallow pile foundations may be more susceptible to surface loads and ground deformation caused by shield machine excavation, while deeper pile foundations are more affected by changes in surrounding soil stress. The longitudinal and transverse deflection results reflect the deformation of the pile foundation in different directions. Longitudinal deflection may affect the changes in the pile foundation's bearing capacity in the direction of shield excavation, while transverse deflection affects the stability of the pile foundation perpendicular to the direction of excavation. Plotting the deflection curve based on the changes in the longitudinal and horizontal clearance distance S between the shield machine and the pile foundation can intuitively illustrate the deformation pattern of the pile foundation as the distance between the shield machine and the pile foundation changes. This process requires precise calculations and data processing to ensure that the curve accurately reflects the actual situation.

[0047] S3: According to the deflection curve in step S2, the deflection variation range H of the pile foundation in depth is obtained, and the corresponding height within the allowable deflection range is determined as the grouting height, such as Figure 4 、 5 In the grouting process, the grouting height H generated by grouting through the grouting pipe is the height of the pile body where the deflection during shield tunneling exceeds the allowable deflection. Allowable deflection is a key indicator determined based on the structural characteristics of the pile foundation, the surrounding environment, and the overall project requirements. In actual projects, different types of pile foundations may have different allowable deflection standards. When determining the grouting height, it is important to accurately identify the portion corresponding to the allowable deflection based on the deflection curve.

[0048] S4: Arrange grouting pipes around the pile foundation, and each grouting pipe is equipped with a separate controller, and the driving depth and grouting height of the grouting pipe are determined according to the grouting height in step S3. The arrangement of grouting pipes around the pile foundation needs to take into account the shape, size and surrounding soil conditions of the pile foundation. If the pile foundation is circular, the grouting pipes may need to be evenly distributed around the circumference to ensure the uniformity of grouting. For square or other shaped pile foundations, they also need to be reasonably arranged according to their geometric characteristics. Each grouting pipe is equipped with a separate controller to achieve precise control of the grouting process. When determining the driving depth of the grouting pipe according to the grouting height, the effectiveness and economy of the grouting should be taken into account. Driving too shallowly may not achieve the expected grouting effect, while driving too deep may increase unnecessary costs and construction difficulty.

[0049] S5: Input the deflection curve in step S2 into the grouting controller; Figure 6 As shown in the figure, the horizontal axis is the lateral deflection value of the pile foundation (perpendicular to the direction of shield tunneling). A deflection of 0mm represents the existing state of the pile foundation with no initial deflection. The vertical axis represents the elevation of the pile foundation in the depth (length) direction, with an elevation of 0m representing the elevation of the ground surface and -5m representing the elevation of the pile top. The curves in the figure are drawn based on different longitudinal horizontal clearance distances S between the shield machine and the pile foundation. Positive distances represent the horizontal clearance distance between the shield machine and the pile foundation before the shield machine passes through the pile foundation, while negative distances represent the horizontal clearance distance between the shield machine and the pile foundation after the shield machine passes through the pile foundation. Taking the curve with the largest deflection of -6m as an example, that is, after the shield machine has passed through the pile foundation by 6m, the lateral deflection of the pile foundation reaches a maximum value of 7.5mm during the entire crossing process. As can be seen from the shape of the curve, the deflection changes away from the shield machine.

[0050] In this step, inputting the deflection curve into the grouting controller is a key link in achieving dynamic control. The lateral deflection value represented by the horizontal axis reflects the deformation of the pile foundation perpendicular to the direction of shield tunneling. The initial state of the pile foundation without deflection is a benchmark. As the shield machine advances, the lateral deflection will gradually change. The elevation represented by the vertical axis can clearly define the positional relationship of the pile foundation in the depth direction. Different curves correspond to different longitudinal horizontal clearances S between the shield machine and the pile foundation, which reflects the influence of the relative position of the shield machine and the pile foundation on the lateral deflection of the pile foundation. When the shield has passed through the pile foundation for 6m, the lateral deflection reaches a maximum value of 7.5mm. This shows that the pile foundation is most significantly affected by the shield tunneling at this stage, and the trend of deflection changes away from the shield machine also reflects the redistribution of soil stress in this process.

[0051] Similarly, if Figure 7 As shown in the figure, the horizontal axis is the longitudinal deflection value of the pile foundation (parallel to the shield tunneling direction). A deflection of 0mm represents the pile foundation's initial state with no deflection. The vertical axis represents the elevation of the pile foundation in the depth (length) direction, with an elevation of 0m representing the ground surface elevation and -5m representing the pile top elevation. The curves in the figure are drawn based on different longitudinal horizontal clearances S between the shield machine and the pile foundation. Positive distances represent the horizontal clearance between the shield machine and the pile foundation before the shield machine passes through, while negative distances represent the horizontal clearance between the shield machine and the pile foundation after the shield machine passes through. Taking the curve with the largest deflection of -6m as an example, after the shield machine has passed 6m through the pile foundation, the longitudinal deflection of the pile foundation reaches its maximum value of 5.8mm during the entire passage. The curve shape shows that the direction of the longitudinal deflection is consistent with the direction of the shield machine's tunneling.

[0052] The longitudinal deflection here is similar to, but different from, the transverse deflection. The longitudinal deflection reflects the deformation of the pile foundation in the direction of shield tunneling. The maximum value of 5.8 mm indicates that the pile foundation reaches its maximum deformation in this direction when the shield machine penetrates 6 meters into the pile foundation. The alignment of the longitudinal deflection with the shield machine's tunneling direction indicates that the shield machine's advance is pushing the pile foundation, causing deformation in this direction. These data and curves are crucial for the grouting controller to accurately assess the pile foundation's deformation and implement appropriate grouting operations.

[0053] S6: Before the shield machine reaches the pile foundation to be lateral-passed, all grouting controllers are activated and mortar is connected. The grouting controllers automatically and dynamically adjust the grouting pipes in real time based on the distance between the pile foundation and the shield machine. The grouting controllers select the corresponding deflection curve based on the deflection curve and distance. The grouting controllers in the deflection direction activate the grouting pipes, applying pressure to the pile foundation in the opposite direction. As the shield machine approaches, the grouting controllers re-evaluate and select the corresponding deflection curve. If the pile foundation deflection curve continues to move in that direction, the grouting controllers in the deflection direction continue to activate. If the pile foundation deflection curve moves in the opposite direction, the grouting controllers in the opposite direction activate, and the grouting controllers in the deflection direction deactivate. This process is repeated until the shield machine reaches a stable crossing point and all controllers are deactivated. This is achieved by pre-calculating the changing lateral and longitudinal deflection curves of the pile foundation affected by shield tunneling and dynamically grouting the pile foundation in real time based on these curves, thereby achieving active control of pile foundation deflection.

[0054] Activating the grouting controller before the shield machine reaches the side-penetrating pile foundation is a preventative measure. After the mortar is connected, the grouting controller begins its dynamic control function. It first determines the deflection direction based on the measured distance between the pile foundation and the shield machine, combined with the previously input deflection curve. Once the deflection direction is determined, grouting is initiated through the corresponding grouting pipe, applying pressure in the opposite direction to the pile foundation to counteract the impact of the shield machine's advance. As the shield machine approaches, the construction environment continuously changes, requiring the grouting controller to reassess and select a new deflection curve. If the pile foundation deflection curve continues in the original direction, further grouting efforts are required, and the grouting controller for the deflection direction will continue. Conversely, if the deflection curve moves in the opposite direction, the grouting direction must be adjusted, activating the grouting controller for the opposite direction and deactivating the original controller. This process is repeated until the shield machine penetrates the pile foundation and the entire structure stabilizes, at which point all controllers are deactivated. This real-time dynamic grouting method based on deflection curves can effectively and proactively control the deflection development of pile foundations, ensuring the stability of existing pile foundations during shield tunneling.

[0055] The embodiments of the present invention are not limited to these. According to the above contents of the present invention, in accordance with common techniques and customary means in this field, and without departing from the above basic technical ideas of the present invention, the present invention may also have various forms of modifications, replacements or changes, all of which fall within the scope of protection of the present invention.

Claims

1. A dynamic control method for protecting existing pile foundations on the side during shield tunneling, characterized in that: Here are the steps: S1: Based on the geological conditions of the site of the tunnel to be excavated, the longitudinal horizontal clearance S between the shield machine (1) and the pile foundation (4), and the transverse horizontal clearance D between the shield machine (1) and the pile foundation (4), a three-dimensional finite element model of the entire construction process of the shield tunnel (2) side-penetrating the pile foundation (4) is established using finite element software; S2: Obtain the longitudinal and transverse deflection results of the pile foundation (4) at different depths in the finite element model established in step S1, and draw a deflection curve of the longitudinal and transverse deflections of the pile foundation (4) and the longitudinal and horizontal clear distance S according to the change of the longitudinal and horizontal clear distance S between the shield machine (1) and the pile foundation (4) during the process; S3: According to the deflection curve in step S2, the deflection variation range H of the pile foundation (4) in depth is obtained; S4: arranging a grouting pipe (6) and a grouting controller (5) around the pile foundation (4), and setting the height of the corresponding grouting body (7) according to the deflection variation range H in step S3; S5: Inputting the deflection curve in step S2 into the grouting controller (5); S6: According to the deflection curve, each grouting controller (5) controls whether the grouting pipe (6) starts or stops grouting, and the grouting pressure in the opposite direction to the deflection curve is always applied under the joint control of several grouting pipes (6) around the pile foundation (4).

2. The dynamic control method for protecting existing pile foundations on the side during shield tunneling according to claim 1 is characterized by: The number of the grouting pipes (6) is at least 4 and they are arranged around the pile foundation (1), wherein two of the grouting pipes (6) are parallel to the tunneling direction of the shield machine (1), and the other two are perpendicular to the tunneling direction of the shield machine (1).

3. The dynamic control method for protecting existing pile foundations on the side during shield tunneling according to claim 1 is characterized by: The grouting controller (5) is located on the top of the grouting pipe (6), and each grouting controller (5) independently controls the grouting pipe (6) below it.

4. The dynamic control method for protecting existing pile foundations on the side during shield tunneling according to claim 3 is characterized by: The grouting controller (5) can measure the longitudinal horizontal clear distance S between the shield machine (1) and the pile foundation (4) in real time.

5. The dynamic control method for protecting existing pile foundations on the side during shield tunneling according to claim 3 is characterized by: The grouting controller (5) will select the corresponding or closest deflection curve according to the longitudinal horizontal clear distance S.

6. The dynamic control method for protecting existing pile foundations on the side during shield tunneling according to claim 1 is characterized in that: The deflection curve in step S2 has a horizontal coordinate representing the deflection value of the pile foundation (1) and a vertical coordinate representing the depth elevation of the pile foundation (1), and multiple curves are drawn according to different longitudinal horizontal clearances S between the shield machine (1) and the pile foundation (4).

7. The dynamic control method for protecting existing pile foundations on the side during shield tunneling according to claim 1, characterized in that: The deflection curve in step S2 includes at least three deflection curves before, during and after the shield machine (1) passes through the pile foundation (4).

8. The dynamic control method for protecting existing pile foundations on the side during shield tunneling according to claim 1, characterized in that: The height of the grouting body (7) in step S4 corresponds to a height within the allowable deflection range of the pile foundation (1).

9. The dynamic control method for protecting existing pile foundations on the side during shield tunneling according to claim 1, characterized in that: The three-dimensional finite element model in step S1 uses the birth-death element control method to simulate the shield excavation process.

10. The dynamic control method for protecting existing pile foundations on the side during shield tunneling according to claim 1, characterized in that: The finite element software in step S1 is MIDAS GTS software.

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