Vertical static load test device for pile foundation model

Abstract

The invention relates to the technical field of teaching demonstration and practical training equipment, and discloses a pile foundation model vertical static load test device which comprises a base, a test pile soil unit, a force measurement system and a displacement measurement system. According to the device, a reduced-scale pile model is adopted to carry out a vertical static load test, different foundation soil layers, different pile types and different bearing properties can be simulated, and tests on stress characteristics of piles, influence factors of pile foundation bearing capacity and the like are carried out, so that students can learn the bearing properties of the pile foundations and determine the bearing capacity; the basic method of the pile foundation static load test is known, and the load-displacement P-s curve of the static load test is drawn. The device can be used for practical teaching of civil engineering and related professions, so that trainees can establish pile foundation engineering concepts.

Description

Technical Field

[0001] The present invention belongs to the technical field of teaching demonstration and training equipment, and specifically relates to a vertical static load test device for a pile foundation model. Background Art

[0002] In the field of modern civil engineering, pile foundations, as the most common foundation form, are widely used in multi-story and high-rise buildings, industrial plants, bridges, and underground projects. According to the differences in experimental techniques, pile foundations are mainly divided into precast piles and cast-in-place piles; according to different bearing behaviors, they can be further divided into friction piles, end-bearing piles, and others. In actual projects, the bearing capacity of pile foundations is affected by many factors, among which the selection of pile types, the properties of foundation soil layers, and bearing behaviors play key roles. Once the settlement and deformation of pile foundations exceed the specified standards, it will not only affect the normal use function of engineering structures but also may lead to serious safety accidents. Therefore, for students majoring in civil engineering and relevant engineering personnel, it is particularly important to learn and master the mechanical properties of pile foundations and their influencing factors.

[0003] In the study of the mechanical properties of pile foundations, although the prototype full-scale pile foundation test can provide relatively real and accurate conditions, such tests have high requirements for site conditions and technical levels. For example, a large test site is required, professional experiments are needed, and experienced technical personnel are required. Moreover, the full-scale pile foundation after the test is usually unable to be used again, resulting in waste of resources. In addition, the production of full-scale pile foundations requires a large amount of material and labor costs, and the production process is complex. However, the characteristic of teaching experiments is that they often need to be repeatedly carried out for comparative tests under various working conditions so that students can deeply understand the mechanical properties and influencing factors of pile foundations. In view of the above limitations of the prototype full-scale pile foundation test, it is not suitable for teaching and training in schools or enterprises, and the present device makes up for this defect.

[0004] In view of this, the present invention is specifically proposed. Summary of the Invention

[0005] To solve the above technical problems, the basic concept of the technical solution adopted by the present invention is as follows: A vertical static load test device for a pile foundation model includes a base; and a support loading mechanism installed on the base for installing a force measuring system and a displacement measuring system; wherein, the force measuring system includes a pressure sensor and a force display; the displacement measuring system includes a displacement scale and a displacement display; It further includes an experimental pile-soil unit arranged on the base for storing the test pile soil and cooperating with the installation of the force measuring system and the displacement measuring system to form the entire experimental process.

[0006] As a preferred embodiment of the present invention, the support loading mechanism includes a reaction frame which is vertically fixed on the base, and a control switch is installed on the reaction frame.

[0007] As a preferred embodiment of the present invention, a vertically downward electric push rod is installed on the reaction frame. The driving end of the electric push rod is connected to one end of a pressure sensor, and the other end of the pressure sensor is installed on the pile cap. A reduced-scale pile is fixed at the bottom of the pile cap.

[0008] As a preferred embodiment of the present invention, the experimental pile-soil unit includes a sand tank, which is installed on the base and filled with sandy soil inside.

[0009] As a preferred embodiment of the present invention, the displacement scale is slidably arranged on the reaction frame, and the displacement display screen is arranged on the reaction frame and electrically connected to the displacement scale.

[0010] As a preferred embodiment of the present invention, the lower end of the displacement scale is fixed on the electric push rod; the pressure sensor is electrically connected to the force display, and the force display is installed on the base.

[0011] The present invention has the following beneficial effects compared with the prior art: 1. Rich teaching functions: This patent can use reduced-scale piles of different pile types and sandy soils of different particle sizes to simulate various working conditions, creating diverse test conditions for trainees to learn the bearing properties of piles, the determination methods of bearing capacity, and the factors affecting bearing capacity. At the same time, trainees can proficiently master the basic process of pile foundation static load tests and the drawing method of static load test curves, improving their understanding and practical ability of pile foundation knowledge.

[0012] 2. Flexible test conditions: This device and test method are not restricted by the site and complex equipment, and the test can be carried out in an ordinary classroom or laboratory (training room). Moreover, due to the strong repeatability of the device, the test can be carried out repeatedly many times, which not only overcomes the limitations of traditional tests in terms of materials, processing, site, equipment, and funds, but also enables the teaching of pile foundation mechanical performance tests to be carried out regularly in relevant professional schools or enterprise engineering training, improving the utilization efficiency of teaching resources.

[0013] 3. Innovative design: Compared with traditional pile foundation test devices, this patent fully considers teaching needs in design, reasonably simplifies and optimizes complex pile foundation tests, and presents them in the form of reduced-scale model tests. Through an integrated design, the test frame, test pile-soil, force measurement system, and displacement measurement system are organically combined, realizing the miniaturization, portability, and multi-functionality of the test device, providing a new test equipment and teaching method for experimental teaching in civil engineering majors.

[0014] The following further describes in detail the specific embodiments of the present invention with reference to the accompanying drawings. Description of the Drawings

[0015] In the accompanying drawings: Figure 1 It is a front view structural schematic diagram of the overall vertical static load test device for a pile foundation model; Figure 2 It is a side view structural schematic diagram of the overall vertical static load test device for a pile foundation model; Figure 3 It is a diagram showing the change of the implementation state of the vertical static load test device for a pile foundation model.

[0016] In the figure: 1 - base; 2 - reaction frame; 3 - control switch; 4 - electric push rod; 5 - pressure sensor; 6 - force display; 7 - displacement scale; 8 - displacement display; 9 - sand tank; 10 - sandy soil; 11 - reduced-scale pile; 12 - pile cap. Specific implementation manners

[0017] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention. Embodiment

[0018] As Figures 1 to 3 shown, a vertical static load test device for a pile foundation model includes a test frame, a test pile soil, a force measurement system and a displacement measurement system.

[0019] (1) Test frame: The test frame is the support and loading basic structure of the whole device, and is composed of a base and a loading mechanism. The base plays an important role in supporting the sand tank and the loading mechanism, provides a stable and reliable foundation for the whole test device, ensures that the device will not displace or shake during the test, and guarantees the accuracy of the test data. The loading mechanism includes a reaction frame, an electric push rod and a control switch, and realizes vertical loading on the reduced-scale pile through the control switch. Among them, the reaction frame is a portal structure connected to the base and installed with all test components, and provides a stable reaction force during the loading process. The maximum stroke of the electric push rod installed on it is 250 mm, the maximum loading force is 2 KN, and the power source is an electric loader using a 24V power supply. The electric push rod is controlled by the on (+) / on (-) / off operation of the power control switch to control the electric loader to drive the extension / retraction / stop movement of the electric push rod, and apply a downward vertical load to the reduced-scale pile. The loading mechanism can provide a continuous and stable loading force according to the test requirements. The operator realizes precise loading control of the test through the control switch.

[0020] (2)Test pile soil: The test pile soil includes scaled-down piles, pile caps, sand pots, and sands with different particle sizes. The scaled-down piles are made of materials such as acrylic, wood, and steel, and have various cross-sectional shapes and sizes. The circular cross-section has diameters of Ф10mm, Ф15mm, Ф20mm, etc., and the side length of the square cross-section has various options such as 10mm×10mm, 15mm×15mm, 20mm×20mm, etc. The length of the scaled-down pile is uniformly set at 330mm to fit the reaction frame of this patent. The scaled-down pile can simulate different types of precast piles in actual projects. The pile cap size is adapted to the scaled-down pile, with a circular cross-section of Ф64mm and a height of 42mm, and a circular groove that can adapt to different pile diameters is provided in the center. The function of the pile cap is to make the force on the top of the scaled-down pile uniform and reduce stress concentration. The sand pot is placed on the base and is used to hold sands with different particle sizes (fine sand, medium sand, or coarse sand). The particle size of the sand can be configured according to the test requirements, and can be arranged in layers or without layers to simulate various foundation soil states, providing the possibility for studying the mechanical properties of pile foundations under different geological conditions.

[0021] (3)Force measurement system: The force measurement system is used to measure the vertical load borne by the pile foundation during the loading process. It consists of a force sensor and a force display. The force sensor uses an S-type pressure sensor, which has the characteristics of high precision and good stability. The force sensor is fixed between the electric push rod and the pile top and is connected in series with them. When the pile is subjected to a vertical load, it can quickly receive the load signal and transmit it to the force display. The force display is a digital display, connected to the force sensor, and converts the received load analog signal into a digital display mode through analog-to-digital conversion, so as to intuitively display the load value and facilitate the test personnel to record and analyze data in real time.

[0022] (4)Displacement measurement system: The displacement measurement system is used to measure the settlement of the scaled-down pile during the loading process. This system includes a displacement scale and a displacement display. The maximum stroke of the displacement scale is 250mm, which matches the stroke of the electric push rod. It is installed on the reaction frame and is connected in parallel with the electric push rod. The displacement scale expands and contracts with the telescopic movement of the thrust rod and is linked with the displacement display to measure and record the settlement value of the scaled-down pile in real time.

[0023] The working principle of this patent is as follows: According to the test requirements, the test pile soil for the preset test plan is installed and set. Through the control switch of the electric loader on the electric push rod, the electric push rod is driven to extend / retract / stop, and a downward vertical load is applied to the reduced-scale pile according to the preset loading procedure. During the loading process, the force measurement system receives the vertical load signal in real time, converts and transmits the signal to the force display, and the force display shows and records the vertical static loading data. At the same time, the displacement scale is connected in parallel with the electric push rod and moves synchronously with the extension / retraction / stop of the electric push rod. The associated electronic displacement display measures and records the settlement value of the reduced-scale pile synchronously. By collecting and processing the force and displacement data, the load-displacement (P - s) curve of the pile foundation test can be formed.

[0024] The experimental steps are as follows: 1. Test preparation: Draw up a test plan; select the reduced-scale pile and sand according to the plan, and place and install the relevant components and force and displacement testing devices. The test loading amount of this test pile is 1500 kN.

[0025] 2. Initial pile pressing and data reading: Turn on the control switch 3 and start the pile pressing operation. Press the test under the determined initial pressure, set the control switch to on (+), and then set it to on (-). At this time, read the vertical static loading data in real time through the force display 6, and at the same time use the displacement display 8 to read the initial displacement data of the pile top. If the read data is normal, zero the readings of the force and displacement display.

[0026] The working state at this stage corresponds to Figure 3 .

[0027] 3. Graded loading and data collection Press the pile according to the preset graded loading procedure. In this example, the pile pressing is carried out in 10 levels, with a load of 150 N for each level. Perform graded vertical static loading on the reduced-scale pile 11. After each level of load is applied, at the specified interval time, read the settlement data through the displacement display 8. When the pile sinking reaches the relative stability standard, apply the next level of load in increments of 150 N for each level, and repeat the above data reading steps.

[0028] This working state corresponds to Figure 3 .

[0029] 4. Pile pressing termination and final data recording When the pile pressing force of the force display 6 reaches 1500 N, and the holding time reaches the pile pressing termination condition, and the settlement amount displayed by the displacement display 8 reaches the pile pressing termination condition, turn off the control switch, and the loading mechanism terminates the loading and starts unloading. The value of each level of unloading is 2 times the loading value. After all unloading, read the settlement according to the regulations.

[0030] This working state corresponds to Figure 3。

[0031] 5. Plot the load-settlement (P-s) curve Based on the experimental readings, plot the load-settlement (P-s) curve and analyze the bearing capacity of the pile through the curve.

Claims

1. A vertical static load test device for a pile foundation model, characterized in that: include: Base (1); A supporting loading mechanism is mounted on the base (1) and is used to install a force measuring system and a displacement measuring system; The force measurement system includes a pressure sensor (5) and a force display (6); the displacement measurement system includes a displacement scale (7) and a displacement display (8); It also includes an experimental pile-soil unit, which is arranged on the base (1) and is used to store the experimental pile-soil and is combined with the installed force measurement system and displacement measurement system to form the entire experimental process.

2. A pile foundation model vertical static load test device according to claim 1, characterized in that: The supporting loading mechanism comprises a reaction frame (2) which is vertically fixed on the base (1), and a control switch (3) is installed on the reaction frame (2).

3. A pile foundation model vertical static load test device according to claim 2, characterized in that: A vertically downward electric push rod (4) is mounted on the reaction frame (2); a driving end of the electric push rod (4) is connected to one end of a pressure sensor (5); and the other end of the pressure sensor (5) is mounted on a pile cap (12); a scaled pile (11) is fixed to the bottom of the pile cap (12).

4. A pile foundation model vertical static load test device according to claim 3, characterized in that: The experimental pile-soil unit comprises a sand pot (9) which is installed on a base (1) and is filled with sand (10).

5. A pile foundation model vertical static load test device according to claim 1, characterized in that: The displacement scale (7) is slidably disposed on the reaction frame (2), and the displacement display screen (8) is disposed on the reaction frame (2) and is electrically connected to the displacement scale (7).

6. A pile foundation model vertical static load test device according to claim 5, characterized in that: The lower end of the displacement scale (7) is fixed on the electric push rod (4); the pressure sensor (5) is electrically connected to the force display (6), and the force display (6) is mounted on the base (1).

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