Energy pile centrifugal model experimental device suitable for drum centrifuge and use method

Abstract

The present invention belongs to the field of geotechnical engineering technology, and relates to an energy pile centrifugal model experimental device suitable for a drum centrifuge and a method of use. The device includes an energy pile model and a measurement system, wherein the energy pile model includes concrete, a micro heat exchange tube, a strain gauge and a steel cage; the measurement system includes a displacement meter, a force sensor, a micro earth pressure box and a temperature sensor array. The present invention effectively controls the temperature of the pile body and realizes hot and cold cycles by arranging a micro heat exchange tube inside the energy pile model; the pile body is arranged with a strain gauge to measure the strain of the pile body; the soil around the pile is arranged with a temperature sensor array to realize the measurement of the temperature change value of the soil around the pile; the pile side is arranged with a micro earth pressure box to measure the change in the horizontal earth pressure and vertical earth pressure around the pile during the experiment; the model box is arranged in a drum centrifuge, and the energy pile centrifugal model test can be carried out to study its action mechanism. The present invention has a simple structure, is economical and applicable, has strong operability, and is easy to implement.

Description

Technical Field

[0001] The invention belongs to the technical field of geotechnical engineering, and relates to a centrifugal model experiment of a pile buried pipe of a ground source heat pump system, and in particular to an energy pile centrifugal model experiment device suitable for a drum centrifuge and a use method thereof. Background Art

[0002] In pile foundation, since the stress characteristics of a single pile are mainly affected by the pile-soil interaction, the stress characteristics of the pile body are often simulated using linear elasticity. Reasonable simulation of the interaction between piles and soil and reproduction of the soil stress level controlled by gravity are of great significance for pile foundation model experiments. The basic principle of the centrifuge model experiment is to place the geotechnical model in a high-speed rotating centrifuge to subject it to high centrifugal acceleration to compensate for the loss of gravity caused by the scale reduction of the model. With the rapid development of geotechnical test technology, centrifuge model experiments have become an important means of pile foundation research.

[0003] Geothermal heat pump technology is a new energy-saving and emission-reduction technology that utilizes shallow geothermal sources. It is of great significance to improve the traditional petrochemical energy structure and promote social development. This technology utilizes the characteristic that the temperature of shallow geothermal sources does not change with the seasons. Through the flow of liquid in the heat exchange tube, energy is exchanged between the upper building and the shallow geothermal source, thereby achieving the purpose of cooling or heating. The new type of pile foundation formed by organically combining the heat exchange tube and the traditional concrete cast-in-place pile is the energy pile. The energy pile has the functions of both pile foundation and geothermal heat pump. It can not only bear the upper building load, but also improve the heat exchange efficiency of the geothermal heat pump. At the same time, it can also greatly reduce the cost and solve the problem of heat exchange tubes occupying underground space. Therefore, it has gradually attracted the attention of engineering and technical personnel.

[0004] As a special pile foundation, energy piles are subject to thermal coupling during operation, and their bearing capacity is very different from that of ordinary pile foundations. The study of the working performance of energy piles through centrifugal model tests under ng conditions is of great significance for clearly understanding the mechanism of thermal coupling factors on energy piles and their application and promotion. In recent years, a large number of model experiments under 1g conditions have been carried out at home and abroad on energy pile technology and certain results have been achieved. However, model experiments under ng conditions are still relatively rare, and the temperature control is relatively rough, which greatly hinders the research progress of energy piles. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the existing experimental devices and to provide an energy pile centrifugal model experimental device and a use method suitable for a drum centrifuge, so as to study the working mechanism of the energy pile under ng conditions.

[0006] The present invention adopts the following technical solution:

[0007] An energy pile centrifugal model experimental device suitable for a drum centrifuge, comprising an energy pile model 10 and a measurement system;

[0008] The energy pile model 10 is mainly composed of concrete 20, micro heat exchange tubes 18, strain gauges and steel cages 19; the micro heat exchange tubes 18 are supported and surrounded by steel cages 19 on the outside, and the steel cages 19 are covered with concrete 20 on the outside and filled with concrete 20 on the inside, forming the pile body of the cylindrical energy pile model 10; a plurality of strain gauges are attached to the outside of the pile body for measuring the strain of the pile body; a loading cover plate 16 is provided at the pile head of the pile body for loading and measuring the displacement of the pile head; the energy pile model 10 is inserted into the soil 17 around the pile in the model box 8; the inner wall of the model box 8 is coated with a thermal insulation material 14 to prevent heat loss;

[0009] The measuring system comprises a displacement meter 11, a force sensor 12, a micro earth pressure box 13 and a temperature sensor array 15; the displacement meter 11 is installed on a loading cover plate 16 to measure the displacement of the pile head; the force sensor 12 is sleeved on the pile head and fixed on the loading cover plate 16 to measure the load on the pile head; the micro earth pressure box 13 is arranged in the soil body 17 around the pile, located on one side and the bottom of the energy pile model 10, to measure the change values ​​of the horizontal earth pressure and the vertical earth pressure around the pile body and at the bottom of the pile body; the temperature sensor array 15 is arranged in the soil body 17 around the pile, located on the other side of the energy pile model 10, at one, two, three and four times the pile diameter away from the pile body axis, to measure the change value of the temperature of the soil body around the pile.

[0010] The energy pile model 10 has a circular cross section.

[0011] The strength of the concrete 20 is C20-C60, and the concrete 20 is polished or a layer of fine sand is adhered to the pile body to change the roughness of the pile body.

[0012] The micro heat exchange tube 18 is made of polyethylene material and has a U-shaped buried tube shape.

[0013] The thermal insulation material 14 is a composite magnesium aluminum silicate thermal insulation material.

[0014] The invention discloses a method for using an energy pile centrifugal model experimental device suitable for a drum centrifuge. The energy pile model 10 and a measuring system are placed in the soil body 17 around the pile of a model box 8; the inner drum 2 of the drum centrifuge is located inside the outer drum 1 of the drum centrifuge, and a cold and hot circulation water pump 3 is located outside the outer drum 1 of the drum centrifuge; two model boxes 8 are symmetrically fixed in the inner drum 2 of the drum centrifuge, so that the central axes of the two model boxes 8 coincide with the central axes of the drum centrifuge control platform 7 and the drum centrifuge actuator 9; the micro heat exchange tube 18 in the energy pile model 10 is respectively connected to the outlet pipe 4 and the inlet pipe 5 of the cold and hot circulation water pump 3 through a rotary joint 6 to change the temperature of the pile body and realize the cold and hot circulation.

[0015] The beneficial effects of the present invention are as follows: by arranging a micro heat exchange tube inside the energy pile model, and connecting the micro heat exchange tube to a cold and hot circulation water pump, the temperature of the pile body can be effectively controlled to realize cold and hot circulation; a strain gauge is arranged on the pile body to measure the strain of the pile body; a temperature sensor array is arranged on the soil body around the pile to realize the measurement of the temperature change value of the soil body around the pile; a micro soil pressure box is arranged on the side of the pile to measure the change in the horizontal soil pressure and vertical soil pressure around the pile during the experiment; the model box is arranged in a drum centrifuge to carry out the energy pile centrifugal model test to study its action mechanism. The present invention has a simple structure, is economical and applicable, has strong operability, and is easy to realize. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic diagram of the overall arrangement of an embodiment of the present invention;

[0017] Figure 2 is a schematic diagram of the model box arrangement of an embodiment of the present invention;

[0018] Figure 3 is a schematic diagram of a measurement system according to an embodiment of the present invention;

[0019] Figure 4 is a schematic diagram of an energy pile model according to an embodiment of the present invention;

[0020] Figure 5 4 is a top view of the energy pile model according to an embodiment of the present invention.

[0021] In the figure: 1 outer drum of drum centrifuge; 2 inner drum of drum centrifuge; 3 cold and hot circulation water pump; 4 water outlet pipe;

[0022] 5 water inlet pipe; 6 rotary joint; 7 drum centrifuge control platform; 8 model box;

[0023] 9 drum centrifuge actuator; 10 energy pile model; 11 displacement meter; 12 force sensor;

[0024] 13 micro earth pressure box; 14 thermal insulation material; 15 temperature sensor array; 16 loading cover plate;

[0025] 17 soil around pile; 18 micro heat exchange tube; 19 steel cage; 20 concrete. DETAILED DESCRIPTION

[0026] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. The protection scope of the present invention is not limited to the description of this implementation.

[0027] like Figure 1 Shown is a schematic diagram of the overall arrangement of the present invention, as shown in Figure 2The figure shows the layout of the model box. When in use, the model box 8 is symmetrically fixed in the inner drum 2 of the drum centrifuge, so that the central axis is flush with the drum centrifuge control platform 7 and the drum centrifuge actuator 9; the cold and hot circulation water pump 3 is arranged outside the drum centrifuge and connected to the micro heat exchange pipe inside the energy pile model 10, and the energy pile model 10 is placed in the pile surrounding soil 17 inside the model box 8.

[0028] like Figure 3 The schematic diagram of the measuring system of the present invention is shown. When in use, the inner wall of the model box 8 is coated with a heat-insulating material 14 to prevent heat loss, and then the soil 17 around the pile is compacted in layers to a set value. In this process, the micro-soil pressure box 13, the temperature sensor array 15 and the energy pile model 10 are respectively arranged in the soil 17 around the pile. Among them, the micro-soil pressure box 13 is arranged according to the experimental needs, and the temperature sensor array 15 is respectively arranged at one, two, three and four times the pile diameter of the energy pile model 10. A loading cover plate 16 is installed at the pile head of the energy pile model 10 to facilitate loading and measuring the pile head displacement. The pile head load is applied to the energy pile model 10 through the force sensor 12 and the loading cover plate 16. The displacement meter 11 is arranged on the loading cover plate 16 to measure the pile head displacement.

[0029] like Figure 4 The schematic diagram of the energy pile model of the present invention is shown in Figure 1. During production, the steel cage 19 is configured according to the experimental requirements and fixed together with the micro heat exchange tube 18, and then a certain grade of concrete 20 is poured according to the test requirements, and cured for 28 days under standard conditions. After demoulding, it can be used. The energy pile model 10 is attached with a strain gauge to measure the strain of the pile body; the micro heat exchange tube 18 is connected to the hot and cold water circulation pump 3 through the outlet pipe 4 and the inlet pipe 5, so as to achieve the purpose of subjecting the energy pile model 10 to the temperature load of the hot and cold cycle.

Claims

1. An energy pile centrifugal model experimental device suitable for a drum centrifuge, characterized in that: It includes an energy pile model (10) and a measurement system; The energy pile model (10) is mainly composed of concrete (20), a micro heat exchange tube (18), a strain gauge and a steel cage (19); the micro heat exchange tube (18) is supported and surrounded by a steel cage (19) on the outside, and the steel cage (19) is covered with concrete (20) on the outside and filled with concrete (20) on the inside, forming the pile body of the cylindrical energy pile model (10); a plurality of strain gauges are attached to the outside of the pile body for measuring the strain of the pile body; a loading cover plate (16) is provided at the pile head of the pile body for facilitating loading and measuring the displacement of the pile head; the energy pile model (10) is inserted into the soil body (17) around the pile in the model box (8); the inner wall of the model box (8) is coated with a thermal insulation material (14) to prevent heat loss; The measuring system comprises a displacement meter (11), a force sensor (12), a micro earth pressure box (13) and a temperature sensor array (15); the displacement meter (11) is mounted on a loading cover plate (16) to measure the displacement of the pile head; the force sensor (12) is sleeved on the pile head and fixed on the loading cover plate (16) to measure the load on the pile head; the micro earth pressure box (13) is arranged in the soil body (17) around the pile, located on one side and the bottom of the energy pile model (10), to measure the change value of the horizontal earth pressure around the pile body and the bottom of the pile body; the temperature sensor array (15) is arranged in the soil body (17) around the pile, located on the other side of the energy pile model (10), at one, two, three and four times the pile diameter from the pile body axis, respectively, to measure the change value of the temperature of the soil body around the pile; The energy pile model (10) and the measurement system are placed in the soil (17) around the pile of the model box (8); the inner drum (2) of the drum centrifuge is located inside the outer drum (1) of the drum centrifuge, and the cold and hot circulation water pump (3) is located outside the outer drum (1) of the drum centrifuge; the two model boxes (8) are symmetrically fixed in the inner drum (2) of the drum centrifuge so that the central axes of the two model boxes (8) coincide with the central axes of the drum centrifuge control platform (7) and the drum centrifuge actuator (9); the micro heat exchange tube (18) in the energy pile model (10) is connected to the outlet pipe (4) and the inlet pipe (5) of the cold and hot circulation water pump (3) through a rotary joint (6) to change the temperature of the pile body and realize cold and hot circulation.

2. The energy pile centrifugal model experimental device suitable for a drum centrifuge according to claim 1, characterized in that: The energy pile model (10) has a circular cross section.

3. An energy pile centrifugal model experimental device suitable for a drum centrifuge according to claim 1 or 2, characterized in that: The strength of the concrete (20) is C20-C60, and the concrete (20) is polished or a layer of fine sand is adhered to the pile body to change the roughness of the pile body.

4. An energy pile centrifugal model experimental device suitable for a drum centrifuge according to claim 1 or 2, characterized in that: The micro heat exchange tube (18) is made of polyethylene material and has a U-shaped buried tube form.

5. The energy pile centrifugal model experimental device suitable for a drum centrifuge according to claim 3, characterized in that: The micro heat exchange tube (18) is made of polyethylene material and has a U-shaped buried tube form.

6. An energy pile centrifugal model experimental device suitable for a drum centrifuge according to claim 1, 2 or 5, characterized in that: The thermal insulation material (14) is a composite magnesium aluminum silicate thermal insulation material.

7. The energy pile centrifugal model experimental device suitable for a drum centrifuge according to claim 3, characterized in that: The thermal insulation material (14) is a composite magnesium aluminum silicate thermal insulation material.

8. The energy pile centrifugal model experimental device suitable for a drum centrifuge according to claim 4, characterized in that: The thermal insulation material (14) is a composite magnesium aluminum silicate thermal insulation material.

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