Centrifuge excavation test support device and method

Abstract

The present application relates to the field of civil engineering geotechnical test, and specifically provides a centrifuge foundation pit excavation test supporting device and method, which comprises a centrifuge device, the centrifuge device is equipped with a centrifuge test model box, one side of the centrifuge test model box is provided with a surrounding structure, further comprising a cushion block, a fixing mechanism, a jacking mechanism and a driving mechanism, the cushion block is placed at the bottom of the side edge of the centrifuge test model box, the fixing mechanism is installed on the cushion block, the jacking mechanism comprises a plurality of supporting rods and a plurality of flanges, the tail end of the supporting rod is fixedly connected with the flange, the driving mechanism comprises a stepping motor, the stepping motor is used to drive the supporting rod to move forward and backward, when the surrounding structure is not supported, the front end of the supporting rod is separated from the surrounding structure, so as to avoid the influence of the supporting rod on the test precision, when the surrounding structure needs to be supported by the supporting rod, the stepping motor controller can drive the supporting rod to move quickly to abut against the surrounding structure, so as to simulate the supporting condition after the foundation pit is excavated.

Description

Technical Field

[0001] This invention relates to the field of geotechnical testing in civil engineering, and more particularly to a support device and method for centrifuge pit excavation testing. Background Technology

[0002] Foundation pit engineering is a complex engineering discipline with strong practical application. To deeply study the deformation laws, stability, and impact on the surrounding environment of foundation pits, centrifuge model tests are often used to reconstruct the stress field. Currently, there are several methods for foundation pit excavation in centrifuge high-gravity tests. One method is unsupported foundation pit excavation, which uses unloading of heavy blocks or drainage of heavy liquid to simulate excavation by machine. However, this method is only suitable for shallow foundation pit conditions and cannot simulate foundation pits with internal supports. Another method is internally supported foundation pit excavation, mainly using a shutdown excavation method. That is, excavating to the design depth under normal gravity conditions and installing supports, then simulating high gravity conditions, repeating this step until the foundation pit excavation is completed. However, the shutdown excavation method completes the foundation pit excavation and support under normal gravity conditions, which is equivalent to completing the support in advance, resulting in a difference from the actual working conditions and distortion of the deformation and stress state of the support system. In addition, this method requires frequent shutdown and restart, causing repeated stress changes in the entire foundation pit system, which may interfere with the test results and significantly increase the operational complexity and test costs.

[0003] A patent document (publication number CN101350152B) discloses a hydraulically controlled simulation system for the entire construction process of a centrifuge-supported foundation pit. The system includes a centrifuge model box, a support system, a drainage system, a foundation pit retaining structure, and rigid baffles. The support system and drainage system are fixed to the rigid baffles, which are fitted snugly against the foundation pit retaining structure within the centrifuge model box. During high-speed centrifuge operation, the drainage system, controlled by the main unit's hydraulic system, discharges the soil-replacing liquid in layers and locks the support rods at each stage. However, this patent still has some shortcomings: the support rods must remain in contact with the retaining structure before the test begins, which may interfere with the stress on the retaining structure and affect the accuracy of the test results. Summary of the Invention

[0004] To address the problem of inconvenience in setting up supports for foundation pit excavation tests, this invention provides a support device and method for centrifuge foundation pit excavation tests. The technical solution adopted by this invention to solve its technical problem is: a centrifuge pit excavation test support device, including a centrifuge device, the centrifuge device is equipped with a centrifuge test model box, a protective structure is provided on one side of the centrifuge test model box, and also includes a pad, a fixing mechanism, a top support mechanism and a driving mechanism. The pad is placed at the bottom of the side of the centrifuge test model box, the fixing mechanism is installed on the pad, the top support mechanism includes multiple support rods and multiple flanges, each flange is slidably connected to the fixing mechanism, the tail end of each support rod is fixedly connected to a flange one-to-one, the front ends of the multiple support rods are used to support the protective structure, and the driving mechanism includes a stepper motor, the stepper motor is installed on the fixing mechanism, and the stepper motor is used to drive the support rods to move back and forth. Preferably, the fixing mechanism includes a positioning plate and a device plate. A connecting plate is fixed to the bottom of the positioning plate. The connecting plate has connecting holes and countersunk screw holes. The bottom of the positioning plate has threaded holes that correspond one-to-one with the countersunk screw holes. The connecting holes are used for fixed connection with the pad block. The device plate has bolt holes for inserting bolts. The device plate is fixedly connected to one side of the positioning plate by bolts. The stepper motor is fixed to the device plate.

[0005] Preferably, the connecting hole and the pad are fixedly connected by bolts, anchors or pins.

[0006] Preferably, the top support mechanism further includes a bushing and a linear bearing, the bushing being fixed to the positioning plate, the linear bearing being fixed inside the bushing, and the support rod being slidably inserted into the linear bearing.

[0007] Preferably, the drive mechanism further includes a motor lead screw and a nut, wherein the motor lead screw is coaxially and fixedly connected to the output shaft of the stepper motor, the nut is threadedly connected to the motor lead screw, and one end of the flange is coaxially and fixedly connected to the nut.

[0008] Preferably, the flange is a square flange, and the positioning plate has a guide groove for accommodating the square flange, and the square flange is slidably installed in the guide groove.

[0009] Preferably, the support rod is hollow inside, and a ball head is provided at the free end of the support rod.

[0010] A method for supporting a centrifuge pit excavation test includes the aforementioned centrifuge pit excavation test support device, and further includes the following steps: S1, placing a pad block at the bottom of the side of the centrifuge test model box and filling the centrifuge test model box with soil; S2, inserting the retaining structure into the soil at a preset position; S3, excavating soil between the retaining structure and the boundary of the model box to form a simulated pit; S4, placing a drainage bag and a top support mechanism in the simulated pit, and installing the fixing mechanism on the pad block; S5, pouring heavy liquid into the drainage bag to simulate the presence of soil; S6, when starting the pit excavation and support test, draining heavy liquid to simulate the excavation of the current soil layer, and when the liquid is drained to the position of the top support mechanism, driving a part of the support rod of the top support mechanism forward through the driving mechanism and abutting against the pad block to complete the support; S7, repeating S6 until the pit excavation is completed.

[0011] The beneficial effects of this invention are as follows: First, by cooperating with the drive mechanism and the top support mechanism, when the retaining structure is not supported, the ball head at the front end of the support rod separates from the retaining structure, thus avoiding the support rod from affecting the test accuracy. When it is necessary to support the retaining structure with the support rod, the stepper motor controller can drive the support rod to move quickly to the position where it abuts against the retaining structure, so as to simulate the support situation after the foundation pit is excavated.

[0012] Secondly, it recreates the actual situation and stress of foundation pit excavation, improving the authenticity and accuracy of the test. Using dynamic control, when support is needed, a stepper motor can quickly move the support rod to the position where it contacts the retaining structure, simulating foundation pit excavation support. This better replicates the layered excavation and support process in actual foundation pit construction, reducing inaccuracies in stress state caused by downtime excavation or support pre-installation, thus improving the authenticity and accuracy of the test.

[0013] Third, the support rod is actively controlled by a stepper motor to achieve support, reducing interference from the top support mechanism to the test. When support is not needed, the ball head at the front end of the support rod separates from the enclosure structure, avoiding passive contact of the support rod affecting the stress on the enclosure structure and reducing interference with the test.

[0014] Fourth, the overall structure of this application is simple and compact, easy to integrate and install, and small, convenient, economical and practical. The device adopts a modular design, with strong connections and reasonable layout between the components, which is especially suitable for the space-constrained environment of centrifuge model chambers, and is conducive to its application in a variety of test scenarios; at the same time, it avoids complex hydraulic or special system control, has a simple structure, is easy to process and reproduce, and the cost of each component is low. Attached Figure Description

[0015] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the overall structure of a centrifuge pit excavation test support device according to the present invention; Figure 2 This is a schematic diagram of the top support mechanism of a centrifuge pit excavation test support device according to the present invention; Figure 3 This is a schematic diagram of the positioning plate of a centrifuge pit excavation test support device according to the present invention; Figure 4 This is a schematic diagram of the structure of the nut of the centrifuge pit excavation test support device of the present invention; Figure 5 This is a schematic diagram of the structure of the bushing of the centrifuge pit excavation test support device of the present invention; Figure 6 This is a schematic diagram of the support rod of a centrifuge pit excavation test support device according to the present invention; Figure 7 This is a schematic diagram of the threaded hole structure of a centrifuge pit excavation test support device according to the present invention; Figure 8 This is a schematic diagram of the connection hole structure of a centrifuge pit excavation test support device according to the present invention.

[0017] Reference numerals in the attached drawings: 1. Stepper motor; 102. Nut; 103. Motor lead screw; 2. Equipment plate; 3. Positioning plate; 301. Threaded hole; 302. Countersunk screw hole; 4. Bushing; 402. Linear bearing; 5. Support mechanism; 501. Support rod; 502. Ball head; 6. Bolt hole; 7. Connecting plate; 702. Connecting hole; 8. Gasket; 9. Flange; 10. Stepper motor controller; 11. Power supply; 12. Centrifuge test model box; 13. Enclosure structure; 14. Drainage bag. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] The concepts involved in this application will first be described with reference to the accompanying drawings. It should be noted that the following descriptions of various concepts are only for the purpose of making the content of this application easier to understand and do not constitute a limitation on the scope of protection of this application; furthermore, the embodiments and features in the embodiments of this application can be combined with each other unless otherwise specified. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0020] like Figures 1 to 8 As shown, the present invention provides an embodiment of a centrifuge pit excavation test support device and method, including centrifuge equipment, equipped with a centrifuge test model box 12, a protective structure 13 is provided on one side of the centrifuge test model box 12, and also includes a pad 8, a fixing mechanism, a top support mechanism 5 and a driving mechanism, with the pad 8 placed at the bottom of the side of the centrifuge test model box 12.

[0021] The fixing mechanism is installed on the pad 8. The fixing mechanism includes a positioning plate 3 and an equipment plate 2. A connecting plate 7 is fixed to the bottom of the positioning plate 3. The connecting plate 7 has a connecting hole 702 and a countersunk screw hole 302. The bottom of the positioning plate 3 has a threaded hole 301 that corresponds one-to-one with the countersunk screw hole 302. The connecting hole 702 is fixedly connected to the pad 8 by bolts, anchors or pins.

[0022] In some other embodiments, the bottom of the positioning plate 3 can be directly bent to form the connecting plate 7, so as to improve the stability between the positioning plate 3 and the connecting plate 7, and a connecting hole 702 is opened in the connecting plate 7 to fix it to the pad 8.

[0023] The top support mechanism 5 includes multiple support rods 501 and multiple flanges 9. Each flange 9 is slidably connected to the fixing mechanism. The flange 9 is a square flange. The positioning plate 3 of the fixing mechanism has a guide groove for accommodating the square flange. The square flange is slidably installed in the guide groove.

[0024] The tail end of each support rod 501 is fixedly connected to the flange 9 one by one. The ball head (502) at the front end of the multiple support rods 501 is used to support the enclosure structure 13. The inside of the support rod 501 is hollow to reduce the weight of the support rod 501 itself, improve the response speed of the support rod 501, and prevent the support rod 501 from bending and deforming due to gravity.

[0025] The free end of the support rod 501 is provided with a ball head 502. After long-term use, the end of the support rod 501 will deform, affecting the supporting accuracy of the support rod 501. By replacing the deformed ball head 502, the accuracy of the support rod 501 itself can be guaranteed. On the other hand, the ball head 502 is in point contact with the enclosure structure 13, which can also improve the positioning accuracy of the support rod 501 when supporting.

[0026] The supporting mechanism 5 also includes a bushing 4 and a linear bearing 402. The bushing 4 is fixed on the positioning plate 3, and the linear bearing 402 is fixed inside the bushing 4. The support rod 501 is slidably inserted into the linear bearing 402. The linear bearing 402 supports the middle part of the support rod 501 to prevent the free end of the support rod 501 from sagging, thereby improving the positioning accuracy of the support rod 501 and ensuring that the support rod 501 can be accurately supported in the required position. At the same time, the linear bearing 402 can also keep the support rod 501 coaxial with the drive mechanism so that the drive mechanism can smoothly drive the support rod 501 to move back and forth along its axial direction.

[0027] The drive mechanism includes a stepper motor 1, which is mounted on a fixed mechanism. The stepper motor 1 is connected to a power supply 11 and a stepper motor controller 10. The drive mechanism also includes a motor lead screw 103 and a nut 102. The motor lead screw 103 is coaxially and fixedly connected to the output shaft of the stepper motor 1. The nut 102 is threadedly connected to the motor lead screw 103. One end of the flange 9 is coaxially and fixedly connected to the nut 102. The stepper motor 1 is used to drive the support rod 501 to move back and forth. When the retaining structure 13 is not supported, the ball head 502 at the front end of the support rod 501 is separated from the retaining structure 13 to avoid the support rod 501 affecting the test accuracy. When it is necessary to support the retaining structure 13 through the support rod 501, the support rod 501 can be quickly moved to the position of contact with the retaining structure 13 by the stepper motor controller 10 to simulate the support situation after the foundation pit is excavated. The equipment plate 2 has bolt holes 6 for inserting bolts. The equipment plate 2 is fixedly connected to one side of the positioning plate 3 by bolts. The stepper motor 1 is fixed on the equipment plate 2, while the support rod 501 is slidably installed on the positioning plate 3. On the one hand, this can reduce the impact of the vibration of the stepper motor 1 on the positioning plate 3, and play a partial vibration isolation effect. On the other hand, the stepper motor 1 is small in size. Fixing multiple stepper motors 1 on the same equipment plate 2 can reduce the use of motor brackets and further reduce the overall space occupied, so that the centrifuge pit excavation test support device of this application can be applied to smaller centrifuge equipment.

[0028] A method for supporting a centrifuge pit excavation test, comprising the aforementioned centrifuge pit excavation test support device, and further comprising the following steps: S1. Place the pad 8 at the bottom of the side of the centrifuge test model box 12 and fill the centrifuge test model box 12 with soil; S2. Insert the retaining structure 13 into the soil according to the preset position; S3. Excavate the soil between the retaining structure 13 and the boundary of the model box to form a simulated foundation pit; S4. Place the drainage bag 14 and the top support mechanism 5 in the simulated foundation pit, and install the fixing mechanism on the pad 8; S5. Pour heavy liquid into the drainage bag 14 to simulate the presence of soil; S6. When the foundation pit excavation and support test begins, drain the heavy liquid to simulate the excavation of the current soil layer. When the liquid is drained to the position of the top support mechanism 5, drive the top support mechanism 5 to move forward by a part of the support rod 501 and make the ball head 502 abut against the pad 8 to complete the support; S7. Repeat the drainage and support steps S6 until the foundation pit excavation is completed. This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. The above are only preferred embodiments of this application. It should be noted that due to the limitations of textual expression, while there are objectively infinite specific structures, those skilled in the art can make several improvements, modifications, or changes without departing from the principles of this application, and can also combine the above technical features in an appropriate manner. These improvements, modifications, changes, or combinations, or the direct application of the inventive concept and technical solution to other situations without modification, should all be considered within the scope of protection of this application.

Claims

1. A centrifuge pit excavation test support device, comprising a centrifuge device, wherein the centrifuge device is equipped with a centrifuge test model box (12), and a retaining structure (13) is provided on one side of the centrifuge test model box (12), characterized in that: It also includes a pad (8), a fixing mechanism, a top support mechanism (5) and a driving mechanism. The pad (8) is placed at the bottom of the side of the centrifuge test model box (12). The fixing mechanism is installed on the pad (8). The top support mechanism (5) includes multiple support rods (501) and multiple flanges (9). Each flange (9) is slidably connected to the fixing mechanism. The tail end of each support rod (501) is fixedly connected to the flange (9) one by one. The front ends of the multiple support rods (501) are used to support the enclosure structure (13). The driving mechanism includes a stepper motor (1). The stepper motor (1) is installed on the fixing mechanism. The stepper motor (1) is used to drive the support rods (501) to move back and forth.

2. The centrifuge pit excavation test support device as described in claim 1, characterized in that: The fixing mechanism includes a positioning plate (3) and an equipment plate (2). A connecting plate (7) is fixed to the bottom of the positioning plate (3). The connecting plate (7) has a connecting hole (702) and a countersunk screw hole (302). The bottom of the positioning plate (3) has a threaded hole (301) that corresponds one-to-one with the countersunk screw hole (302). The connecting hole (702) is used to fix the connection with the pad (8). The equipment plate (2) has a bolt hole (6) for inserting bolts. The equipment plate (2) is fixedly connected to one side of the positioning plate (3) by bolts. The stepper motor (1) is fixed on the equipment plate (2).

3. The centrifuge pit excavation test support device as described in claim 2, characterized in that: The connecting hole (702) and the pad (8) are fixedly connected by bolts, anchors or pins.

4. The centrifuge pit excavation test support device as described in claim 2, characterized in that: The top support mechanism (5) also includes a bushing (4) and a linear bearing (402). The bushing (4) is fixed on the positioning plate (3), and the linear bearing (402) is fixed inside the bushing (4). The support rod (501) is slidably inserted into the linear bearing (402).

5. The centrifuge pit excavation test support device as described in claim 2, characterized in that: The drive mechanism also includes a motor lead screw (103) and a nut (102). The motor lead screw (103) is coaxially and fixedly connected to the output shaft of the stepper motor (1). The nut (102) is threadedly connected to the motor lead screw (103). One end of the flange (9) is coaxially and fixedly connected to the nut (102).

6. The centrifuge pit excavation test support device as described in claim 5, characterized in that: The flange (9) is a square flange, and the positioning plate (3) has a guide groove for accommodating the square flange. The square flange is slidably installed in the guide groove.

7. The centrifuge pit excavation test support device as described in claim 1, characterized in that: The support rod (501) is hollow inside, and a ball head (502) is provided at the free end of the support rod (501).

8. A method for test support during centrifuge pit excavation, characterized in that, The centrifuge pit excavation test support device, as described in any one of claims 1 to 7, further includes the following steps: S1. Place the pad (8) at the bottom of the side of the centrifuge test model box (12) and fill the centrifuge test model box (12) with soil. S2. Insert the retaining structure (13) into the soil at the preset position; S3. Excavate soil between the retaining structure (13) and the boundary of the model box to form a simulated foundation pit; S4. Place a drainage bag (14) and a top support mechanism (5) in the simulated pit, and install the fixing mechanism on the pad (8); S5, Heavy liquid is poured into the drainage bag (14) to simulate the presence of soil; S6. When the foundation pit excavation and support test begins, heavy liquid is discharged to simulate the current soil layer excavation. When the liquid is discharged to the position of the top support mechanism (5), a part of the support rod (501) of the top support mechanism (5) is driven forward by the drive mechanism and abuts against the pad block (8) to complete the support. S7. Repeat S6 until the excavation of the foundation pit is completed.

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