Special-shaped concrete heat exchange energy pile monitoring device

Abstract

The utility model discloses a special-shaped concrete heat exchange energy pile monitoring device which comprises an energy pile, the energy pile is composed of a plurality of energy pile units, and heat exchange pipes are arranged in the energy pile units. The heat exchange pipe is connected with a ground source heat pump; each energy pile unit comprises a pile body and a pile cap, each pile body is composed of a plurality of branches, and each branch comprises a flange and a web; the center of the pile body is provided with an inlet leading into the heat exchange pipe, and the center of the branch is provided with a heat exchange pipe outlet. A strain sensor is arranged on the pile body, and an optical fiber temperature sensor is arranged in the pile body; the optical fiber strain sensor and the optical fiber temperature sensor are connected with a distributed optical fiber demodulator; longitudinal steel bars are arranged on the periphery of the pile body, stirrups surround the periphery of the pile body, the longitudinal steel bars are arranged to resist vertical loads, and the stirrups surround the periphery of the pile body so that the mechanical property of the pile can be optimized. According to the utility model, the problem that the pile foundation is unstable due to the fact that the existing pile body in a common shape cannot provide enough side friction resistance in a soft soil area is solved.

Description

Technical Field

[0001] This utility model relates to irregularly shaped concrete cast-in-place piles in the fields of rock and soil engineering, construction, and soft soil foundation reinforcement in geological engineering, and particularly to a monitoring device for irregularly shaped concrete heat exchange energy piles. Background Technology

[0002] In soft soil foundation pits and highway bridge approach transition sections, the stability often decreases due to the characteristics of soft soil. Ordinary piles cannot fully utilize the bearing capacity of each soil layer, cannot provide sufficient side friction resistance, and may even lead to pile foundation instability. Therefore, using irregularly shaped piles solves the problem that ordinary piles cannot meet the requirements for side friction resistance, effectively addressing the difficulty of insufficient foundation bearing capacity.

[0003] Currently, energy consumption for heating and cooling in urban residential buildings will continue to rise. Within 200 meters below the surface, due to the soil's good heat retention capacity, a large amount of shallow geothermal energy is stored. Underground energy structures can effectively utilize this shallow geothermal energy to achieve heating and cooling for buildings, and are considered a potential alternative to conventional fossil fuels, alleviating the current energy crisis. However, most energy piles currently used in pile foundations are round piles, which can only provide heating or cooling for the superstructure and do not significantly improve the bearing capacity of the foundation.

[0004] Energy pile technology embeds heat exchange pipes directly within the building's pile foundation. In summer, it transfers excess heat from the building interior to the soil, cooling the building; in winter, it extracts heat from the soil for heating. Energy piles effectively utilize the high thermal conductivity and heat storage capacity of concrete, serving the dual purpose of bearing the building's load and exchanging heat with the surrounding soil. Compared to traditional ground source heat pump technology, it offers advantages such as reduced drilling costs, superior heat transfer performance, and savings in underground space.

[0005] Currently, irregularly shaped piles are rarely used, and they also lack the function of heating and cooling for the superstructure. Energy piles, on the other hand, are prefabricated components used for heating and cooling in large buildings. These foundation piles should be equipped with heat exchange pipes within their bodies, forming an internal piping system for circulating heat exchange agents. How to incorporate heat exchange pipes into irregularly shaped piles while simultaneously providing high pile side friction resistance and heat exchange with the soil, thereby addressing the issue of foundation bearing capacity under both hot and cold conditions, requires further investigation. Utility Model Content

[0006] Purpose of this utility model: Addressing the shortcomings of existing technologies, this utility model aims to propose a monitoring device for irregularly shaped concrete heat exchange energy piles. By improving the pile cross-sectional shape and integrating the pile foundation with a ground-source heat exchange system, an irregularly shaped concrete energy pile is formed. This energy pile has an irregular cross-section. After adding a heat exchange system to the irregularly shaped concrete pile foundation, the strain and temperature of the pile body are monitored, significantly increasing the pile's side surface area, improving side friction resistance and foundation bearing capacity. This solves the problem that existing ordinary-shaped piles cannot provide sufficient side friction resistance in soft soil areas, leading to pile foundation instability. Furthermore, it provides a heat exchange system for the irregularly shaped pile, enabling it to have corresponding heat exchange capabilities under hot and cold conditions, thus better adapting to pile foundation design problems in different regions.

[0007] Technical solution: The utility model of the irregular concrete heat exchange energy pile monitoring device includes an energy pile, which is composed of multiple energy pile units, and a heat exchange pipe is connected inside the energy pile unit; the heat exchange pipe is connected to a ground source heat pump.

[0008] The energy pile unit includes a pile body and a pile cap. The pile body is composed of multiple branches, which include flanges and webs. An inlet for the heat exchange tube is opened at the center of the pile body, and an outlet for the heat exchange tube is opened at the center of each branch.

[0009] Strain sensors are installed on the pile body, and fiber optic temperature sensors are installed inside the pile body; the fiber optic strain sensors and fiber optic temperature sensors are connected to a distributed fiber optic demodulator.

[0010] The pile body is surrounded by longitudinal steel bars and hoops. The purpose of the longitudinal steel bars is to resist vertical loads, and the hoops are used to optimize the mechanical properties of the pile.

[0011] The heat exchange tubes are bent and connected at the bottom of the pile body to prevent misalignment during concrete pouring and subsequent use.

[0012] The flange is equipped with a threaded sleeve that connects to the pile cap, which fixes the pile cap while ensuring that the heat exchange tube at the top of the pile is not damaged during construction.

[0013] The top of the pile cap is covered with a rubber layer, which reduces the disturbance and damage to the pile caused by the impact load on the pile top during the pile driving process.

[0014] The inner diameter of the heat exchange tube is less than 1% of the flange width, thereby reducing the stress concentration effect on the pile body caused by the installation of the heat exchange tube.

[0015] The pile cap is equipped with a lifting ring on the outside, which facilitates the lifting of the pile during construction.

[0016] The pile body is reinforced with steel bars, which optimizes the mechanical properties of the pile and overcomes the problem of insufficient bearing capacity of plain concrete piles.

[0017] Triangular stirrups are placed at the center of the pile body for reinforcement.

[0018] The heat exchange tubes are equipped with longitudinal ribs to secure them, making it easy to tie them up.

[0019] Fiber optic temperature sensors and fiber optic strain sensors are installed within the triangle formed by the junction of the flange and the web.

[0020] Working Principle: This invention improves the structure of concrete energy piles by using an irregular shape for the pile cross-section, increasing the pile's lateral surface area and thus improving the pile's side friction resistance and foundation bearing capacity. Simultaneously, heat exchange pipe inlets and outlets are set at the center of the pile cross-section and the center of the flanges. U-shaped heat exchange pipes are embedded inside the pile and connected to an indoor ground source heat pump unit, enabling the irregularly shaped pile to simultaneously provide heating and cooling functions for the superstructure. This invention is suitable for solving foundation bearing capacity problems under cold or hot conditions. Finally, the pile strain and temperature are monitored using the monitoring method of this invention, providing a better solution for the utilization of geothermal energy.

[0021] The concrete energy pile of this utility model is suitable for heat exchange of pile foundations composed of multiple piles. After the heat exchange pipes of all irregularly shaped energy piles are laid out and each pile is poured, the heat exchange pipes of each pile are connected in sequence in the space of the pile foundation cap and connected to the ground source heat pump in the room. After the connection is completed, the construction of the pile foundation cap is carried out, thereby realizing the overall heat exchange of the pile group.

[0022] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0023] (1) This utility model adopts an irregular pile cross section, which reduces the self-weight of the pile body and improves the performance of the pile body compared with the traditional round pile and square pile. It also increases the stiffness of the pile foundation. The irregular cross section increases the contact area between the pile side surface and the pile side soil, and increases the pile side friction. The irregular pile improves the horizontal bearing capacity, bending resistance and shear resistance of a single pile, thereby improving the bearing capacity of the pile foundation, reducing the occurrence of uneven settlement, and improving the bearing capacity of the foundation.

[0024] (2) This utility model embeds heat exchange pipes inside the irregularly shaped piles and circulates heat exchange fluid, enabling the pile foundation to exchange heat with the soil while meeting the bearing capacity requirements: in summer or hot conditions, the heat exchange medium absorbs indoor heat and releases it to the soil through the heat exchange pipes; in winter or cold conditions, the heat exchange medium absorbs low-temperature heat energy from the soil and uses this heat for indoor heating. Through the above heat exchange, this utility model solves the indoor heating and cooling problems of the superstructure and is more practical than traditional pile foundations.

[0025] (3) This utility model measures the strain of the irregular energy pile during its entry into the soil and during its operation by installing distributed strain fiber optic sensors on the pile body; at the same time, it installs fiber optic temperature sensors inside the energy pile to monitor the temperature change of the pile body during the heat transfer process, thereby sensing the heat transfer range of the irregular energy pile.

[0026] (4) The pile cap of this utility model reduces the damage to the heat exchange tube and fiber optic sensor of the pile body during the pile driving process. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the on-site monitoring of the irregular concrete heat exchange energy pile monitoring device of this utility model;

[0028] Figure 2 This is a schematic diagram of the reinforcement of the irregular concrete heat exchange energy pile of this utility model;

[0029] Figure 3 This is a longitudinal cross-sectional view of the irregular concrete heat exchange energy pile of this utility model;

[0030] Figure 4 This is a top view of the pile cap of the irregularly shaped concrete heat exchange energy pile of this utility model;

[0031] Figure 5 This is a side view of the pile cap of the irregularly shaped concrete heat exchange energy pile of this utility model;

[0032] Figure 6 This is a flowchart illustrating the on-site construction process of the irregularly shaped concrete heat exchange energy pile of this utility model. Detailed Implementation

[0033] This utility model relates to an irregularly shaped concrete heat exchange energy pile, which is a cast-in-place concrete pile with a cross-section as shown in the figure. Figure 1 As shown in the figure. In this embodiment, the cross-section of the heat exchange energy pile consists of three branches of the same size and shape. Each branch includes two flanges 12 and one web 13. The two flanges and one web have the same length and width. The branches are connected by equilateral triangles, and the three branches form an included angle of 120°. At the same time, the three branches are also connected by equilateral triangles to form an irregular pile cross-section.

[0034] Each irregular cross-section of this utility model is divided into 9 rectangular regions and 3 equilateral triangular regions. In addition to keeping the width of the rectangular regions and the side length of the triangular regions the same, the length-to-width ratio of the rectangular regions is between 1 and 1.5 to reduce the occurrence of local instability problems in the pile cross-section and increase the service life of the irregular energy pile.

[0035] The pile body is equipped with heat exchange pipes to exchange heat with the soil beside the pile. The location of the heat exchange pipes embedded inside the irregularly shaped energy pile of this invention is as follows: Figure 1 , Figure 2 As shown.

[0036] To reduce construction time, high-pressure-bearing plastic pipes are used for the heat exchanger in this embodiment. The heat exchanger is embedded in a U-shape, with an outlet 15 located in one branch. To minimize stress concentration on the pile body 5 due to the heat exchanger installation, the inner diameter of the heat exchanger is controlled within 1% of the flange width. The U-shaped heat exchanger is formed by bending two heat exchanger pipes at the bottom and then splicing them together. One heat exchanger is positioned at the center of the pile cross-section, and the other at the center of another branch. The length of the spliced ​​U-shaped heat exchanger is 90% of the pile length to ensure heat exchange between the heat exchange medium and the soil, thus increasing the heat exchange capacity. To maximize the temperature influence area of ​​the heat exchange medium, it is introduced into the irregularly shaped energy pile from the heat exchanger inlet 14 at the center of the pile cross-section and then exits from the heat exchanger outlet 15 at the branch center, completing one heat exchange with the soil.

[0037] To prevent the heat exchange tubes from shifting during concrete pouring and subsequent use, the two heat exchange tubes are first bent and connected into a U-shape. Then, the U-shaped heat exchange tubes are tied to the longitudinal bars of the steel cage to form a whole. The steel cage and heat exchange tubes are placed before the concrete is poured.

[0038] To ensure the heat exchange tubes at the pile top are not damaged during construction, a pile cap is connected to the top of the irregularly shaped pile to protect the pile head area, as shown in the figure. Threaded sleeves 24 are embedded at the center of the six flanges at the pile top, and the irregularly shaped pile is connected to the pile cap 27 using high-strength bolts. To accommodate the pile shape of the energy pile, the pile cap is hexagonal, and its size is larger than that of the irregularly shaped pile. Furthermore, to protect the heat exchange tubes and fiber optic sensors exposed at the pile top, the depth of the pile cap is at least 1m, and a 10cm depth is left between the bolt connection and the top of the pile cap.

[0039] Meanwhile, lifting rings are welded at the center of the three long sides on the outer side of the pile cap to facilitate lifting of the pile during construction. A rubber layer 28 with a thickness of 15mm is installed on the top of the pile cap to reduce the disturbance and damage to the pile caused by the impact load on the pile top during pile driving.

[0040] To address the insufficient bearing capacity of plain concrete piles, steel reinforcement is incorporated into irregularly shaped concrete heat exchange energy piles to optimize their mechanical properties. For example... Figure 2 As shown, longitudinal steel bars 18 are arranged around the pile contour to resist vertical loads, and are surrounded by stirrups 17. Stirrups 19 are added to the triangular area at the center of the pile cross-section. At the same time, a longitudinal bar is added above the heat exchange tube to facilitate the binding of the heat exchange tube. This longitudinal bar is connected to the steel cage by two structural steel bars 20 to form a whole.

[0041] For monitoring the temperature and strain of irregularly shaped concrete energy piles, before concrete pouring, distributed fiber optic temperature sensors 4 and distributed fiber optic strain sensors 6 are installed within the triangular area at the junction of the web and flange of the remaining two branches inside the pile body 5. The distributed fiber optic temperature sensors 4 and distributed fiber optic strain sensors 6 are tied to the longitudinal reinforcement bars of the reinforcing cage, secured with cable ties 23 at least 10 cm intervals. To ensure the survival rate of the fiber optic sensors, the measurement range of the fiber optic sensors is from the bottom of the reinforcing cage to 0.5 m below the pile top. Lead wires are connected within a 0.5 m area above the pile top and pass through the pile head; the lead wires above the pile top are protected by a protective sleeve.

[0042] To monitor the driving and heat exchange processes of irregularly shaped energy piles, this invention utilizes distributed fiber optic strain and temperature sensors to monitor changes in pile strain and temperature. To meet the demands for higher foundation bearing capacity and heat exchange, existing buildings typically employ pile foundations. During the driving process of the irregularly shaped energy pile, strain sensor 6 and distributed fiber optic demodulator 9 are connected via fiber optic strain sensor lead 8. Simultaneously, distributed fiber optic demodulator 9 is connected to computer terminal 11 via data transmission line 10 to monitor pile side strain. After the irregularly shaped pile reaches the required driving depth, the inlet and outlet of the heat exchange tubes are connected to constant temperature water tank 1 via inlet pipe 3 and outlet pipe 2, respectively. A water pump 22 is installed on the inlet pipe to control the water flow rate within the heat exchange tubes. All heat exchange tubes are connected end-to-end to form an integrated heat exchange tube 24. Simultaneously, temperature sensor 4 is connected to fiber optic demodulator 9 via fiber optic temperature sensor lead 7 to test changes in pile temperature and thermal strain during the heat exchange process. Based on this, a load was applied to the top of the pile to test the temperature and strain increment of the irregular energy pile under the action of thermo-coupling.

[0043] The fabrication and on-site construction method of this utility model of irregularly shaped concrete heat exchange energy pile includes the following steps:

[0044] (1) Use high-precision steel molds or composite material molds to ensure the forming accuracy of the irregular bifurcated structure; make an irregular steel reinforcement cage, tie the heat exchange tubes and distributed fiber optic sensors to the steel reinforcement cage to form an integral whole, select high-strength C40 or higher, low-shrinkage concrete, vibrate in layers to avoid cavities, and the curing period is not less than 28 days. Before initial setting, embed threaded sleeves at specific positions on the flange to facilitate the subsequent connection of the pile cap.

[0045] (2) Use a transport frame to fix the irregularly shaped piles to prevent collision damage to the flanges; place wooden blocks on site to prevent pile deformation caused by foundation settlement. After the piles are transported to the site, connect the top of each pile to the pile cap with bolts.

[0046] (3) After the site is leveled, mark the pile position, and control the error within ±50mm; place the guide frame at the pile driving position to position the drilling rig 29, align the drill bit with the pile center, and ensure that the verticality is ≤0.5% (two-way monitoring with theodolite) and the positioning deviation is ≤10mm. Control the rotation speed at 16 rpm during the drill bit sinking process and control the rotation speed at 32 rpm during the drill bit lifting process. Stop drilling if the drill gets stuck or deviates.

[0047] (4) Grouting and mixing of the site soil, using cement as a curing agent and adding fly ash admixture, using a mixer 30 to forcibly mix the site soil and cement to form cement soil. The cement dosage is adjusted according to the soil depth, and the mixing time per meter is greater than 2 minutes to ensure that the grout and soil are mixed evenly.

[0048] (5) Use the hoist 31 in conjunction with the balance beam to hoist the lifting ring on the irregular pile cap at multiple points to ensure that the verticality deviation of the irregular pile body is ≤1% and to prevent damage to the flange structure during the pile driving process. After the pile is driven to the design elevation, static pressure is started to ensure that it is pressed in before the cement soil hardens.

[0049] (6) The pre-reserved heat pipe at the top of the pile is connected to the horizontal manifold by electrofusion welding or mechanical connection, and a water pressure test of 0.6-1.0MPa is conducted. The pressure is maintained for 30 minutes without leakage. The exposed part of the pipe is covered with an anti-corrosion and heat insulation layer to prevent freezing expansion or corrosion.

[0050] (7) Backfilling work is carried out in the area around the pile. The backfill material is fine sand or bentonite mixture, and it is compacted in layers to a density of ≥95% to reduce thermal resistance and protect the lateral stability of the pile.

[0051] (8) After the heat exchange medium is injected into the heat exchange tube of the pile, the temperature and thermal strain of the pile are monitored by the distributed optical fiber installed in the pile to verify whether the thermo-mechanical coupling performance meets the design requirements.

Claims

1. A monitoring device for irregularly shaped concrete heat exchange energy piles, characterized in that: It includes an energy pile, which is composed of multiple energy pile units, and each energy pile unit has a heat exchange pipe connected to it; the heat exchange pipe is connected to a ground source heat pump. The energy pile unit includes a pile body (5) and a pile cap (27). The pile body (5) is composed of multiple branches, each of which includes a flange (12) and a web (13). The center of the pile body (5) is provided with an inlet (14) for passing through a heat exchange tube, and the center of each branch is provided with a heat exchange tube outlet (15). The pile body (5) is equipped with an optical fiber strain sensor (6) and an optical fiber temperature sensor (4) is installed inside the pile body (5); the optical fiber strain sensor (6) and the optical fiber temperature sensor (4) are connected to a distributed optical fiber demodulator (9). The pile body (5) is surrounded by longitudinal steel bars (18) and hoops (17).

2. The monitoring device for irregularly shaped concrete heat exchange energy piles according to claim 1, characterized in that: The heat exchange tube is connected after being bent at the bottom of the pile body (5).

3. The monitoring device for irregularly shaped concrete heat exchange energy piles according to claim 1, characterized in that: The flange is provided with a threaded sleeve that connects to the pile cap (27).

4. The monitoring device for irregularly shaped concrete heat exchange energy piles according to claim 1, characterized in that: The top of the pile cap (27) is covered with a rubber layer (28).

5. The monitoring device for irregularly shaped concrete heat exchange energy piles according to claim 1, characterized in that: The inner diameter of the heat exchange tube is less than 1% of the flange width.

6. The monitoring device for irregularly shaped concrete heat exchange energy piles according to claim 1, characterized in that: The outer side of the pile cap (27) is provided with a lifting ring.

7. The monitoring device for irregularly shaped concrete heat exchange energy piles according to claim 1, characterized in that: The pile body (5) is reinforced with steel bars.

8. The monitoring device for irregularly shaped concrete heat exchange energy piles according to claim 1, characterized in that: A triangular stirrup (19) is provided at the center of the pile body (5).

9. The monitoring device for irregularly shaped concrete heat exchange energy piles according to claim 1, characterized in that: The heat exchange tube is provided with longitudinal ribs for fixing the heat exchange tube.

10. The monitoring device for irregularly shaped concrete heat exchange energy piles according to claim 1, characterized in that: Fiber optic temperature sensors (4) and fiber optic strain sensors (6) are arranged in the triangle at the junction of the flange (12) and the web (13).

Images