Detection test device for self-balancing bearing capacity of post-grouting pile foundation

Abstract

The utility model relates to the technical field of post-grouting pile foundation static load tests, in particular to a post-grouting pile foundation self-balancing bearing capacity detection test device which comprises a model box, a model pile, a first dial indicator, a second dial indicator and a telescopic device, and the model pile is embedded in the model box; the model pile comprises a self-balancing upper section pile and a self-balancing lower section pile; the telescopic device is arranged between the self-balancing upper section pile and the self-balancing lower section pile; the first dial indicator is arranged above the self-balancing upper section pile and is used for measuring the displacement amount of the self-balancing upper section pile; and the second dial indicator is arranged below the model box and is used for measuring the displacement amount of the lower displacement rod. The device is convenient to mount and test, can be recycled for multiple times, and can be used for configuring corresponding model tests according to corresponding actual engineering conditions to obtain corresponding test data for guiding engineering practice.

Description

Technical Field

[0001] This utility model patent relates to the field of static load testing technology for post-grouting pile foundations, specifically to a testing device for detecting the self-balancing bearing capacity of post-grouting pile foundations. Background Technology

[0002] Piles are the most commonly used foundation type in building engineering. Their application is increasingly widespread due to their advantages such as flexible selection, no seasonal restrictions on construction, and minimal environmental pollution. In engineering, the static load test method is the most reliable way to determine the ultimate bearing capacity of a single pile. This test method currently best reflects the vertical bearing capacity of pile foundations and is a true reflection of their actual working conditions. Standards such as the "Technical Code for Building Pile Foundations" (JGJ 94-2008) and the "Code for Design of Building Foundations" (GB50007-2011) also clearly stipulate that the bearing capacity of completed engineering piles must be tested. However, for a long time, the equipment used for static load testing has remained limited to two forms: a ballast platform or an anchor pile reaction frame (surcharge method, anchor pile method). The testing work is time-consuming, labor-intensive, and expensive. Therefore, people often try to avoid performing static load tests. Moreover, the higher the bearing capacity of a single pile, the more difficult it is to implement static load tests. As a result, accurate bearing capacity data for large-tonnage pile foundations of many important buildings and structures is often unavailable, and the potential of the pile foundation cannot be rationally utilized. Both the surcharge method and the anchor pile method are limited by tonnage and site conditions. In addition, the surcharge method has the safety hazard of the surcharged object easily overturning during the surcharge and testing process; the anchor pile method has the problems of complicated anchor pile construction, long construction period and high cost.

[0003] The self-balancing pile test method utilizes the internal reaction force of the pile foundation. A load cell is embedded at the equilibrium point inside the pile, and the load is applied by balancing the side friction and self-weight of the upper pile segment with the side friction and end resistance of the lower pile segment. The test results are then converted into the pile's bearing capacity. Therefore, compared to traditional static load tests, the self-balancing pile test method offers advantages such as time-saving, labor-saving, cost-effectiveness, and safety, leading to its increasingly widespread application in engineering projects.

[0004] In practical engineering for pile foundation bearing capacity testing, conducting in-situ tests requires significant time, manpower, and financial resources. Furthermore, various factors related to engineering geological conditions can prevent in-situ testing. In contrast, indoor model tests for pile foundations, based on the actual stress state of the pile, establish a reasonable similarity ratio with the engineering pile. By artificially controlling certain test variables, the bearing characteristics and deformation patterns of the pile foundation under specific loading conditions can be studied. This approach offers advantages such as economy, timeliness, and strong operability. However, currently, there are relatively few publicly available reliable post-grouting techniques. Summary of the Invention

[0005] To address the above shortcomings, this utility model provides a convenient and effective test device for detecting the self-balancing bearing capacity of post-grouting pile foundations.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A test device for detecting the self-balancing bearing capacity of post-grouting pile foundations includes a model box, a model pile, a first dial gauge, a second dial gauge, and an expansion joint. The model pile is embedded in the model box. The model pile includes a self-balancing upper section pile and a self-balancing lower section pile. The expansion joint is disposed between the self-balancing upper section pile and the self-balancing lower section pile. A lower displacement rod is provided at the lower end of the self-balancing lower section pile. A movable hole is provided at the bottom of the model box. The lower displacement rod passes through the movable hole. The first dial gauge is disposed above the self-balancing upper section pile for measuring the displacement of the self-balancing upper section pile. The second dial gauge is disposed below the model box for measuring the displacement of the lower displacement rod. Optionally, grouting holes are symmetrically provided on the upper sidewall of the self-balancing upper section pile. A pile bottom grouting hole is provided on the bottom surface of the self-balancing lower section pile.

[0008] Optionally, grouting pipes are connected to the grouting hole and the grouting hole at the bottom of the pile, respectively.

[0009] Optionally, a stabilizing device is also included, comprising a 7-shaped fixing base, a lifting and fixing turntable, and a stabilizing screw. The 7-shaped fixing base includes a horizontal bar positioned above the self-balancing upper section pile. A first fixing hole is provided on the upper part of the self-balancing upper section pile. A second screw hole is provided on the horizontal bar corresponding to the first fixing hole. A third screw hole is provided on the lifting and fixing turntable corresponding to the second screw hole. The stabilizing screw passes through the first fixing hole, the second screw hole, and the third screw hole, and is respectively locked and fixed into a whole by nuts, thereby locking the three-dimensional spatial position of the self-balancing upper section pile and preventing the self-balancing upper section pile from swinging.

[0010] Optionally, a turntable lifting screw is provided above the self-balancing upper pile, and a lifting hole is provided in the middle of the lifting fixed turntable corresponding to the turntable lifting screw; the lifting fixed turntable can be lifted and lowered on the turntable lifting screw and is locked and fixed by a nut.

[0011] Optionally, the 7-shaped fixing base includes a vertical rod, which is detachably fixed to the side wall of the model box.

[0012] Optionally, three or more of the 7-shaped fixing seats are provided, arranged alternately along the outer perimeter of the model box. Optionally, a connecting plate is provided on the upper part of the self-balancing upper pile, and the connecting plate is provided with a plurality of the first fixing holes.

[0013] Optionally, it also includes a steel frame, which is disposed above the self-balancing upper pile, and the upper end of the turntable lifting screw is connected to the steel frame.

[0014] Optionally, it also includes a slurry storage tank, an air pump, and a slurry separator; the slurry storage tank is a positive pressure sealed tank, the air pump pressurizes the slurry storage tank, and the slurry separator diverts the slurry in the slurry storage tank to the grouting pipe.

[0015] Compared with the prior art, the beneficial effects of this utility model are:

[0016] 1. This device is easy to install and test, and can be used repeatedly. During the test, it measures the stress and strain distribution of the model pile body, and can analyze the development and distribution law of pile axial force and pile side friction during the self-balancing pile test process. According to the actual situation of the corresponding engineering, the corresponding model test can be configured to obtain the corresponding test data to guide engineering practice.

[0017] 2. The stabilizing device can prevent the self-balancing upper pile from shifting during grouting, ensuring that the self-balancing upper pile is stably maintained in the previously adjusted position. The fixing method of using a 7-shaped fixing seat + lifting fixing turntable improves the stability of the fixing, while also improving the convenience and controllability of the stabilizing screw before and after grouting, and reducing the interference of the stabilizing screw on the position of the self-balancing upper pile during the disassembly and assembly process. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this utility model, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0019] Figure 1 This is a schematic diagram of the structure of this utility model after the stabilizing device has been removed;

[0020] Figure 2 This is a top view of the assembly of the 7-shaped fixing base, model box, and model pile of this utility model;

[0021] Figure 3 This is a side view of the assembly of the stabilizing device, model box, and model pile of this utility model. Detailed Implementation

[0022] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model without creative effort are within the scope of protection of the present utility model.

[0023] In the description of this utility model, it should be noted that the terms "inner", "front", "rear", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship that the utility model product is usually placed in during use. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0024] In the description of this utility model, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0025] A test device for detecting the self-balancing bearing capacity of post-grouting pile foundations includes a model box 18, a model pile, a first dial gauge 11, a second dial gauge 3, and an expansion joint 1. The model pile is embedded in the model box 18. The soil layers can be set according to actual needs; for example, the soil for the test layered foundation model can be selected from two soil samples: clay 5 and silt 10. In this embodiment, as shown... Figure 1 As shown, the model box 18 is an open-top galvanized barrel with a height of 880mm, a diameter of 580mm, a capacity of 200L, and a wall thickness of 3mm. A 3mm circular steel plate is welded to the bottom of the barrel to prevent deformation of the bottom of the barrel during ramming. A 5mm hole is opened at the bottom of the model box 18 to allow the strain gauge wire of the self-balancing lower section pile to be led out from the bottom of the barrel. In this embodiment, the model box 18 is placed on a masonry platform with a height of 650mm.

[0026] The model piles include a self-balancing upper section pile 8 and a self-balancing lower section pile 6, both of which are aluminum alloy hollow tube model piles with an outer diameter of 50mm and an inner diameter of 45mm. Strain gauges are installed at various parts of the pile body of the self-balancing upper section pile 8 and the self-balancing lower section pile 6. A 5-8mm round hole is opened on one side of the self-balancing upper section pile 8 at 30mm from the top of the pile to lead out the connecting wires of the strain gauges at various parts of the pile body. A 5-8mm round hole is opened on one side of the self-balancing lower section pile 6 at 30mm from the bottom of the pile to lead out the connecting wires of the strain gauges at various parts of the pile body. The wires are then passed through the soil layer at the bottom of the pile and led out along the small hole at the bottom of the tube.

[0027] The telescopic device 1 is installed between the self-balancing upper section pile 8 and the self-balancing lower section pile 6. In this embodiment, a jack is used, and the telescopic movement is controlled by an external loader 7. A lower displacement rod 2 is installed at the lower end of the self-balancing lower section pile 6. A 5mm movable hole is provided at the bottom of the model box 18. The lower displacement rod 2 passes through the movable hole and can move freely up and down. The first dial gauge 11 is installed above the self-balancing upper section pile 8 and is fixed with a magnetic base. It is used to measure the displacement of the self-balancing upper section pile 8. The second dial gauge 3 is installed below the model box. It is used to measure the displacement of the lower displacement rod.

[0028] Optionally, the upper sidewall of the self-balancing upper section pile 8 is provided with grouting holes 9 with a diameter of 8mm on each side symmetrically along the left and right sides; the bottom surface of the self-balancing lower section pile 6 is provided with pile bottom grouting holes 4 with a diameter of 8mm.

[0029] Optionally, grouting pipes 12 are connected to the grouting holes 9 and 4 at the pile bottom, respectively. Simultaneously, sealing nails of the same size are used to seal each grouting hole 9 and the pile bottom grouting hole 4 to prevent sand from entering the grouting holes / pile bottom grouting holes before grouting, thus preventing blockage. In this embodiment, a grout storage tank 13, an air pump 14, a grout separator 16, and a valve 15 are also included. The grout storage tank is a positive pressure sealed tank, and the air pump pressurizes the grout storage tank. The grout separator diverts the grout in the grout storage tank to the grouting pipes.

[0030] In this embodiment, a steel frame 17 is also included, which is disposed above the self-balancing upper pile, and the upper end of the turntable lifting screw is connected to the steel frame. In this embodiment, as... Figure 1 As shown, the steel frame 17 is an angle steel support embedded in the masonry, with its two sides located on both sides of the model box. Each angle frame is fixed with short angle frame bolts with a width of 20mm and a length of 300mm and is supported by diagonal bracing.

[0031] Optionally, to improve the stability of the self-balancing upper pile during grouting and prevent changes in its three-dimensional spatial position, in this embodiment, as follows: Figures 2-3As shown, it also includes a stabilizing device, which includes a 7-shaped fixing base, a lifting and fixing turntable 34, and a stabilizing screw 27. The 7-shaped fixing base includes a horizontal rod 21 and a vertical rod 20. The side wall of the model box 18 is provided with a fixing plate 22, and the vertical rod 20 is detachably fixed to the fixing plate 22 by bolts 23. The horizontal bar 21 is provided with reinforcing ribs 24 and is positioned above the self-balancing upper section pile 8. A connecting plate 19 is provided on the upper part of the self-balancing upper section pile 8, and the connecting plate 19 is provided with a plurality of first fixing holes 26, which can be straight holes or first threaded holes. A second screw hole 28 is provided on the horizontal bar corresponding to the first fixing holes. A third screw hole 30 is provided on the lifting and fixing turntable 34 corresponding to the second screw hole 28. The stabilizing screw 27 passes through the first fixing hole 26, the second screw hole, and the third screw hole, and is respectively locked and fixed into a whole by the first upper and lower nut group 25, the second upper and lower nut group 29, and the third upper and lower nut group 31, thereby locking the three-dimensional spatial position of the self-balancing upper section pile and preventing the self-balancing upper section pile from swinging.

[0032] Optionally, a turntable lifting screw 32 is provided above the self-balancing upper pile, and a lifting hole is provided in the middle of the lifting fixed turntable corresponding to the turntable lifting screw; the lifting fixed turntable can be lifted and lowered on the turntable lifting screw, and is locked and fixed by the fourth upper and lower nut group 33.

[0033] Optionally, three or more 7-shaped fixing seats are provided (three are provided in this embodiment), and they are arranged alternately along the outer perimeter of the model box, such as... Figure 2 As shown, they are arranged in a triangular pattern.

[0034] In use, after the self-balancing upper pile 8 and other positions are adjusted, before grouting, the 7-shaped fixing seat with the stabilizing screw 27 is fixed. At this time, the lifting and fixing turntable 34 is at its highest point. Then, the stabilizing screw 27 is rotated downwards, passing through the first fixing hole 26, and the remaining one of the first upper and lower nut groups 25 is inserted from the lower end of the stabilizing screw 27. Then, the lifting and fixing turntable 34 is moved downwards. When it is about to approach the upper end of the stabilizing screw 27, the third screw hole 30 is aligned with the stabilizing screw 27. Then, the stabilizing screw 27 is rotated upwards until the top of the stabilizing screw 27 passes through the top of the third screw hole 30. Then, the remaining nut of the third upper and lower nut group 31 is inserted from the top of the stabilizing screw 27. Then, all the upper and lower nut groups are tightened. After the installation is completed, the self-balancing upper pile 8 can be installed. After grouting and curing, loosen the first, second, and third upper and lower nut groups. First, rotate the stabilizing screw 27 downwards to disengage its upper end from the lifting and fixing turntable 34. Then, move the lifting and fixing turntable 34 to its highest position. Next, rotate the stabilizing screw 27 upwards to disengage its lower part from the connecting plate 19. Finally, remove the 7-shaped fixing seat and the stabilizing screw 27. This structure improves the stability of the self-balancing upper pile 8. The 7-shaped fixing seat is integrated with the model box 18, and the stabilizing screw 27 provides effective support during assembly and disassembly. This reduces the impact on the position of the self-balancing upper pile 8 during the assembly and disassembly of the stabilizing screw 27 and the connecting plate 19, maintaining stability and improving operational controllability.

[0035] After completing the above operations, relevant testing experiments can begin, such as loading. Based on the expected ultimate load value, loading is performed in ten stages (simultaneous loading of the self-balancing upper pile 8 and the self-balancing lower pile 6). When the increase in displacement is greater than five times that of the previous loading stage, it can be determined that the self-balancing upper pile 8 and the self-balancing lower pile 6 have failed, and the ultimate bearing capacity of the self-balancing upper pile 8 and the self-balancing lower pile 6 is taken. This device is easy to install and test, and can be used repeatedly. During the test, the stress and strain distribution of the model pile is measured, and the development and distribution laws of the pile axial force and pile side friction during the self-balancing pile test can be analyzed. Appropriate model tests can be configured according to the actual engineering conditions to obtain corresponding test data to guide engineering practice.

Claims

1. A testing device for detecting the self-balancing bearing capacity of post-grouting pile foundations, characterized in that: The system includes a model box, model piles, a first dial indicator, a second dial indicator, and an expansion joint. The model piles are embedded inside the model box. Each model pile consists of a self-balancing upper pile and a self-balancing lower pile. The expansion joint is positioned between the self-balancing upper pile and the self-balancing lower pile. A lower displacement rod is provided at the lower end of the self-balancing lower pile. A movable hole is provided at the bottom of the model box. The lower displacement rod extends through the movable hole. The first dial indicator is positioned above the self-balancing upper pile and is used to measure the displacement of the self-balancing upper pile. The second dial indicator is positioned below the model box and is used to measure the displacement of the lower displacement rod.

2. The test device for detecting the self-balancing bearing capacity of post-grouting pile foundations according to claim 1, characterized in that: The upper sidewall of the self-balancing upper section pile is symmetrically provided with grouting holes on both the left and right sides; the bottom surface of the self-balancing lower section pile is provided with pile bottom grouting holes.

3. The test device for detecting the self-balancing bearing capacity of post-grouting pile foundations according to claim 2, characterized in that: Grouting pipes are connected to the grouting holes and the pile bottom grouting holes, respectively.

4. The test device for detecting the self-balancing bearing capacity of post-grouting pile foundations according to claim 1, characterized in that: It also includes a stabilizing device, which comprises a 7-shaped fixing base, a lifting and fixing turntable, and a stabilizing screw. The 7-shaped fixing base includes a horizontal bar, which is positioned above the self-balancing upper section pile. A first fixing hole is provided on the upper part of the self-balancing upper section pile. A second screw hole is provided on the horizontal bar corresponding to the first fixing hole. A third screw hole is provided on the lifting and fixing turntable corresponding to the second screw hole. The stabilizing screw passes through the first fixing hole, the second screw hole, and the third screw hole, and is respectively locked and fixed into a whole by nuts, thereby locking the three-dimensional spatial position of the self-balancing upper section pile and preventing the self-balancing upper section pile from swinging.

5. The test device for detecting the self-balancing bearing capacity of post-grouting pile foundations according to claim 4, characterized in that: A turntable lifting screw is provided above the self-balancing upper pile, and a lifting hole is provided in the middle of the lifting fixed turntable corresponding to the turntable lifting screw; the lifting fixed turntable can be lifted and lowered on the turntable lifting screw and is locked and fixed by a nut.

6. The test device for detecting the self-balancing bearing capacity of post-grouting pile foundations according to claim 4, characterized in that: The 7-shaped fixing base includes a vertical rod, which is detachably fixed to the side wall of the model box.

7. The test device for detecting the self-balancing bearing capacity of post-grouting pile foundations according to claim 4, characterized in that: There are three or more 7-shaped fixing seats, which are arranged alternately along the outer perimeter of the model box.

8. The test device for detecting the self-balancing bearing capacity of post-grouting pile foundations according to claim 4, characterized in that: The upper part of the self-balancing upper pile is provided with a connecting plate, and the connecting plate is provided with a plurality of the first fixing holes.

9. The test device for detecting the self-balancing bearing capacity of post-grouting pile foundations according to claim 5, characterized in that: It also includes a steel frame, which is set above the self-balancing upper pile, and the upper end of the turntable lifting screw is connected to the steel frame.

10. The test device for detecting the self-balancing bearing capacity of post-grouting pile foundations according to claim 3, characterized in that: It also includes a slurry storage tank, an air pump, and a slurry separator; the slurry storage tank is a positive pressure sealed tank, and the air pump pressurizes the slurry storage tank; the slurry separator diverts the slurry in the slurry storage tank to the grouting pipe.

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