An energy pile structure based on CFRP toughened fabric bag grouting technology

Abstract

This invention provides an energy pile structure based on CFRP-reinforced geotextile bag grouting technology, belonging to the field of building construction technology. The energy pile structure includes: a core hollow steel-concrete composite core, an extended steel pipe section, an outer reinforced concrete component, a heat pump exchange pipe component, a CFRP-reinforced heat transfer network, and a geotextile bag. This energy pile structure enables rapid pile casting in karst areas, especially in environments with significant silt and soil blockage in the underlying karst caves. It can quickly penetrate the mud layer while ensuring the geotextile bag is not easily damaged, forming a pile structure with strong load-bearing capacity. Simultaneously, combining the geotextile bag grouting technology and the characteristics of CFRP fabric, it also enables rapid exchange of heat pump exchange pipes with external geothermal energy, significantly improving geothermal energy conduction efficiency and providing a better option for the development of geothermal renewable clean energy in the karst regions of southwestern my country.

Description

Technical Field

[0001] This utility model belongs to the field of building construction technology, specifically relating to an energy pile based on CFRP toughened bag grouting technology in karst development areas. Background Technology

[0002] Karst landforms are a unique geological type dominated by calcium carbonate rocks. This geological environment often features vast and complex underground cave networks formed by chemical dissolution. Typical characteristics include surface valleys and numerous underground caves and conduit systems. The formation of karst landforms involves long-term interaction between water and rock, leading to the dissolution and collapse of rock strata. Under different climatic and geological conditions, karst landforms can exhibit diverse morphologies and structures, significantly impacting regional hydrological characteristics and geological structures. In southwestern regions of my country, such as Guangxi and Guizhou, the highly developed karst landforms and widespread underground cave and conduit networks have caused significant challenges to the design and construction of pile foundations in building engineering. Because current geological exploration techniques cannot accurately predict the size, extent, and orientation of underground cave networks in advance, the unexpected discovery of unexplored underground cave systems during construction is frequent. Traditional reinforced concrete pile foundation work cannot be directly poured when encountering underground caves. Some large underground cave systems, due to their large volume and the interference of groundwater, may even be unable to undergo effective consolidation grouting. Bag grouting technology refers to a construction method in which the main steel structure is encased in an outer geotextile bag during the construction of building pile foundations, and concrete is poured into the geotextile bag to form the pile foundation structure, enabling pile foundation construction in large underground karst systems. This technology can avoid the problems of difficult consolidation grouting and excessively high construction costs in underground karst systems, ensuring the feasibility and economy of pile foundation construction in underground karst systems, and has become one of the main means to solve related engineering problems. However, due to the complex internal environment of underground karst systems, silt accumulation and blockage are prone to occur, causing the geotextile bag to be easily damaged by friction with rock walls and silted soil during the downward hoisting process, resulting in grout leakage and making it impossible to pour the outer concrete properly. Furthermore, the pile skeleton structure encased in the geotextile bag is difficult to penetrate the silt-blocked area to reach the designated depth, seriously hindering the normal construction of related pile foundation projects.

[0003] Geothermal energy is a highly efficient, stable, and environmentally friendly renewable resource. By utilizing the near-constant temperature of the soil, rocks, and groundwater in the vicinity of geothermal hotspots, geothermal exchange systems can be established to transfer geothermal energy to the surface for use. In areas with highly developed karst landforms, underground cave systems contain pipes that can penetrate hundreds of meters underground. The groundwater flowing within these systems carries energy from deep geothermal hotspots to shallower strata, thus forming numerous shallow geothermal hotspots. However, the existing design of externally mounted heat pump exchange pipes in geothermal exchange systems generally fails to achieve the desired effect in underground caves. Due to the influence of groundwater in the caves, the heat pump exchange pipes are susceptible to erosion from floods and impacts from soil and rocks during the flood season, leading to structural damage. Therefore, the energy pile structure is the most commonly used geothermal exchange system design scheme with built-in heat pump exchange pipes in karst landform development areas. The external concrete protective layer can ensure that the geothermal exchange system can work normally under complex geological conditions. However, traditional reinforced concrete energy pile structures have problems such as relatively low structural bearing capacity and difficulty in pouring and constructing in karst development areas. At the same time, the limitation of pile volume also leads to relatively low geothermal exchange efficiency of energy pile structures, which weakens the application value of energy pile structures.

[0004] In summary, this study proposes a new type of energy pile structure with high bearing capacity, based on geotextile bags with strong friction resistance and grouting technology. This structure is suitable for convenient construction in geological environments with large underground karst cave systems and can quickly traverse silt deposits. Furthermore, the structural design enhances the geothermal exchange efficiency of the energy pile facilities. This approach is of great significance for large-scale engineering construction, ensuring the structural safety of buildings, and developing new renewable and clean energy sources in the highly developed karst landform areas of southwestern my country. Utility Model Content

[0005] To overcome the problems of low geothermal exchange efficiency, low bearing capacity, and difficulty in casting and construction in karst areas of existing energy pile structures, this utility model provides an energy pile structure based on CFRP toughened bag grouting technology.

[0006] The above-mentioned objectives of this utility model are achieved through the following technical solution:

[0007] An energy pile structure based on CFRP toughened geotextile bag grouting technology includes: a core hollow steel-concrete composite member, a steel pipe extension section, an outer reinforced concrete component, a heat pump exchange pipe component, a CFRP toughened heat transfer network, and a geotextile bag; the core hollow steel-concrete composite member is located in the middle of the overall structure and consists of an inner steel pipe, an outer steel pipe, and core concrete, with the core concrete filling the gap between the inner and outer steel pipes; the steel pipe extension section is located at the lower part of the core hollow steel-concrete composite member and consists of a tapered steel pipe extension section and an outer steel pipe skirt, the tapered steel pipe extension section penetrating the bottom of the geotextile bag and connecting to the bottom of the outer steel pipe, the outer steel pipe skirt being circumferentially set on the tapered steel pipe extension section; the outer reinforced concrete component is encased in the core hollow steel-concrete composite member. The outer reinforced concrete component, surrounding the soil structure, consists of an outer concrete casing and a reinforcing cage. The reinforcing cage encloses the core hollow steel-concrete composite component, and the outer concrete casing fills the space between the core hollow steel-concrete composite component and the geotextile bag. The heat pump exchange pipe component consists of a heat pump exchange spiral pipe and a heat pump exchange straight pipe. The heat pump exchange spiral pipe is located outside the reinforcing cage, and the heat pump exchange straight pipe is located inside the inner steel pipe. The bottom of the heat pump exchange spiral pipe passes through a pre-reserved hole in the extension section of the tapered steel pipe and connects to the bottom of the heat pump exchange straight pipe. The CFRP cloth toughened heat transfer network consists of a CFRP cloth toughening network and a CFRP cloth heat transfer network. The CFRP cloth toughening network is located inside the geotextile bag, and the CFRP cloth heat transfer network is located within the outer concrete casing. The geotextile bag is located outside the outer concrete casing.

[0008] Furthermore, the inner steel pipe and the outer steel pipe are arranged concentrically.

[0009] Furthermore, the inner steel pipe is a circular steel pipe or a polygonal steel pipe, and the outer steel pipe is a circular steel pipe or a polygonal steel pipe.

[0010] Furthermore, the steel cage is formed by binding longitudinal bars and stirrups wrapped around the longitudinal bars.

[0011] Furthermore, the CFRP fabric toughening network is formed by pasting CFRP fabric in a crisscross pattern onto the inside of the geotextile bag.

[0012] Furthermore, the CFRP cloth heat transfer network is formed by wrapping and pasting CFRP cloth onto the heat pump exchange spiral tube.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] 1) The hollow sandwich steel tube concrete structure was adopted as the core in the energy pile structure design. Compared with the traditional reinforced concrete energy pile, it effectively improved the structural bearing capacity and enhanced the ability of the energy pile structure to resist floods and soil and rock impacts in karst areas.

[0015] 2) By using bag grouting technology, the energy pile structure can be conveniently cast on-site in karst areas.

[0016] 3) By combining bag grouting technology and CFRP fabric toughening technology, the possibility of local damage to the outer geotextile bag caused by friction with the rock walls and silt in the karst cave during construction is effectively reduced, which may lead to grout leakage and prevent the normal pouring of the outer concrete.

[0017] 4) By setting a tapered steel pipe extension section at the bottom of the hollow sandwich steel pipe concrete, the pile's ability to penetrate silt is greatly enhanced, effectively solving the problem that the structure is difficult to lower to the specified depth when encountering silt blockage in the karst cave during construction.

[0018] 5) By utilizing the characteristic that the extended section of the tapered steel pipe can penetrate deep into the lower strata of the structure, the geothermal energy stored in the bottom strata can be quickly transferred to the vicinity of the heat pump exchange pipe through the high thermal conductivity of steel, thereby improving the geothermal exchange efficiency of the energy pile structure.

[0019] 6) Utilizing the characteristics of large pile volume formed by bag grouting technology and the good thermal conductivity of CFRP cloth, geothermal energy around the pile can be quickly transferred to the heat pump exchange pipe. Through a larger geothermal exchange area, a longer geothermal exchange distance and a faster geothermal conduction speed than existing energy pile structures, the efficiency of geothermal energy utilization can be significantly improved.

[0020] In summary, the energy pile structure based on CFRP toughened geotextile bag grouting technology proposed in this invention enables rapid pile casting in karst areas. Particularly effective in environments with significant silt and rock blockage in underlying karst caves, it can quickly penetrate mud layers while ensuring the geotextile bag remains relatively intact, resulting in a pile structure with strong load-bearing capacity. Furthermore, combining the geotextile bag grouting technology with the characteristics of CFRP fabric, it also enables rapid exchange of heat pump exchange pipes with external geothermal energy, significantly improving geothermal energy conduction efficiency and providing a superior option for the development of geothermal renewable clean energy in the karst regions of southwestern my country. Attached Figure Description

[0021] Figure 1 This is a cross-sectional view of the overall structure of the energy pile structure of this utility model when it adopts a circular inner steel pipe and a circular outer steel pipe.

[0022] Figure 2 This is a cross-sectional view of the overall structure of the energy pile structure of this utility model when it adopts a circular inner steel pipe and a square outer steel pipe.

[0023] Figure 3This is a cross-sectional view of the overall structure of the energy pile structure of this utility model when it adopts a square inner steel pipe and a circular outer steel pipe.

[0024] Figure 4 This is a cross-sectional view of the overall structure of the energy pile structure of this utility model when it adopts a square inner steel pipe and a square outer steel pipe.

[0025] Figure 5 This is an overall structural elevation view of the energy pile structure of this utility model before the external concrete pouring.

[0026] Figure 6 This is an elevation view of the overall structure of the energy pile structure of this utility model after the outer concrete is poured.

[0027] Figure 7 This is a bottom view of the overall structure of the energy pile structure of this utility model after the outer concrete is poured.

[0028] Figure 8 This is a schematic diagram of the geothermal exchange system in the energy pile structure of this utility model.

[0029] Figure 9 This is a schematic diagram of the CFRP cloth toughened heat transfer network in the energy pile structure of this utility model.

[0030] The markings in the diagram are as follows: 1-Inner steel pipe, 2-Core concrete, 3-Outer steel pipe, 4-Extension of tapered steel pipe, 5-Outer steel pipe skirt, 6-Reinforcing cage, 601-Longitudinal reinforcement, 602-Stirrups, 7-Outer concrete casing, 8-Heat pump exchange pipe component, 801-Heat pump exchange spiral pipe, 802-Heat pump exchange straight pipe, 9-CFRP cloth toughened heat transfer network, 901-CFRP cloth toughened network, 902-CFRP cloth heat transfer network, 10-Geotextile bag, 11-Grouting pipe, 12-Plastic collar, 13-One-way valve. Detailed Implementation

[0031] The technical solution of this utility model will be further described in detail below with reference to the accompanying drawings.

[0032] like Figure 1-9As shown, this utility model provides a hybrid energy pile structure based on CFRP toughened geotextile bag grouting technology, including: a core hollow sandwich steel pipe concrete component, a steel pipe extension section, an outer reinforced concrete component, a heat pump exchange pipe component, a CFRP toughened heat transfer network, and a geotextile bag; the core hollow sandwich steel pipe concrete component is located in the middle of the overall structure and is composed of an inner steel pipe 1, an outer steel pipe 3, and a core concrete 2, with the core concrete 2 filling the gap between the inner steel pipe 1 and the outer steel pipe 3; the steel pipe extension section is located at the lower part of the core hollow sandwich steel pipe concrete component, and is composed of a tapered steel pipe extension section 4 and an outer steel pipe skirt 5. The tapered steel pipe extension section 4 penetrates the bottom of the geotextile bag 10 and connects to the bottom of the outer steel pipe 3, and the outer steel pipe skirt 5 is circumferentially arranged on the tapered steel pipe extension section 4; the outer reinforced concrete component is wrapped around the core hollow sandwich steel pipe concrete component, and is composed of an outer concrete 7 and a reinforcing cage. The structure consists of six components: a reinforcing cage 6, which is formed by binding longitudinal bars 601 and stirrups 602 wrapped around the longitudinal bars; the reinforcing cage 6 is wrapped around the core hollow steel pipe concrete component; the outer concrete 7 is filled between the core hollow steel pipe concrete component and the geotextile bag; the heat pump exchange pipe component 8 is composed of a heat pump exchange spiral pipe 801 and a heat pump exchange straight pipe 802; the heat pump exchange spiral pipe 801 is located outside the reinforcing cage 6, and the heat pump exchange straight pipe 802 is located inside the inner steel pipe 1; the bottom of the heat pump exchange spiral pipe 801 passes through the reserved hole of the tapered steel pipe extension section 4 and connects to the bottom of the heat pump exchange straight pipe 802; the CFRP cloth toughened heat transfer network 9 is composed of a CFRP cloth toughened network 901 and a CFRP cloth heat transfer network 902; the CFRP cloth toughened network 901 is located inside the geotextile bag 10, and the CFRP cloth heat transfer network 902 is located in the outer concrete 7; the geotextile bag 10 is located outside the outer concrete 7.

[0033] Furthermore, such as Figure 1-4 As shown, the inner steel pipe 1 and the outer steel pipe 3 are concentrically arranged. The core hollow sandwich steel pipe concrete component is mainly divided into four types according to the cross-section of the inner steel pipe 1 and the outer steel pipe 3: (1) the inner steel pipe 1 is a circular steel pipe and the outer steel pipe 3 is a circular steel pipe; (2) the inner steel pipe 1 is a circular steel pipe and the outer steel pipe 3 is a polygonal steel pipe; (3) the inner steel pipe 1 is a polygonal steel pipe and the outer steel pipe 3 is a circular steel pipe; (4) the inner steel pipe 1 is a polygonal steel pipe and the outer steel pipe 3 is a polygonal steel pipe. The circular steel pipe can be a standard circular steel pipe, an elliptical steel pipe and other special circular steel pipes. The polygonal steel pipe can be a square steel pipe, a rectangular steel pipe, a regular hexagonal steel pipe, a regular octagonal steel pipe and other standard and non-standard polygonal steel pipes. The specific steel pipe cross-section is selected according to the different engineering design needs.

[0034] Furthermore, such as Figure 5 , 6As shown, the CFRP fabric toughening network 901 is formed by pasting CFRP fabric in a crisscross pattern onto the inside of the geotextile bag 10. The CFRP fabric heat transfer network 902 is formed by wrapping and pasting CFRP fabric onto the heat pump exchange spiral tube 801.

[0035] Based on the structural characteristics of the energy pile designed according to the CFRP toughened bag grouting technology of this utility model, the construction method steps are as follows:

[0036] Step 1: Drill holes and collect core samples to analyze geological characteristics and determine the type and size of the pile cross-section.

[0037] Step 2: Place the inner steel pipe 1 in the middle of the outer steel pipe 3, with the two placed concentrically, and pour the core concrete 2 into the gap between the inner steel pipe 1 and the outer steel pipe 3.

[0038] Step 3: Place a heat pump straight pipe 802 inside the inner steel pipe 1 and a heat pump spiral pipe 801 outside the outer steel pipe 3. After passing the bottom of the heat pump spiral pipe 801 through the reserved hole of the tapered steel pipe extension section 4, connect it to the bottom of the heat pump straight pipe 802.

[0039] Step 4: Weld the tapered steel pipe extension section 4 and the outer steel pipe skirt 5 to the bottom of the outer steel pipe 3;

[0040] Step 5: Using the heat pump exchange spiral pipe 801 as a frame, tie the longitudinal reinforcement 601 and the stirrups 602 to form the steel cage 6;

[0041] Step 6: CFRP cloth is pasted on the inside of geotextile bag 10 to form CFRP cloth toughening network 901, and another part of CFRP cloth is wrapped and pasted on heat pump exchange spiral tube 801 to form CFRP cloth heat transfer network 902, thus forming CFRP cloth toughening heat transfer network 9.

[0042] Step 7: Wrap the main structure with geotextile bag 10, attach the end of CFRP heat transfer network 902 to CFRP toughening network 901, then tie the top and bottom ends of geotextile bag 10 tightly, and insert grouting pipe 11 into the bag. The bottom of the grouting pipe is connected to a one-way valve 13, and the top of the grouting pipe 11 passes through plastic collar 12.

[0043] Step 8: Hoist the entire structure to the designated location in the underground cave. If silt blockage occurs, use the lower conical steel pipe extension 4 to pass through the mud layer.

[0044] Step 9: Pour concrete 7 into the geotextile bag 10 through the grouting pipe 11 to form the outer casing concrete 7. The one-way valve 13 connected to the bottom of the grouting pipe can only allow cement grout to pass through in one direction to prevent backflow. After the pouring is completed, unscrew the grouting pipe 11 and plug the plastic collar 12 with the one-way valve 13.

[0045] Step 10: After the outer concrete 7 has cured, inject the heat exchange fluid from the ground surface into the heat pump exchange spiral pipe 801. After the energy is fully exchanged at the geothermal hot spot, it is then drawn back to the ground surface for use through the heat pump exchange straight pipe 802.

[0046] The designed energy pile structure based on CFRP-toughened geotextile bag grouting technology uses a hollow-core steel-concrete composite structure as its core. Compared with traditional reinforced concrete energy piles, this effectively improves the structural bearing capacity and enhances the energy pile structure's ability to resist floods and soil impacts during the flood season in karst areas. The use of geotextile bag grouting technology ensures convenient on-site casting construction in karst areas. By combining geotextile bag grouting technology and CFRP toughening technology, the possibility of localized damage to the outer geotextile bag 10 due to friction with the rock walls and silted soil in the karst cave during construction, leading to grout leakage and preventing normal casting of the outer concrete 7, is effectively reduced. The tapered steel pipe extension 4 at the bottom significantly strengthens the pile. The ability of the structure to penetrate silt effectively solves the problem of silt blockage in karst caves during construction, making it difficult to lower the structure to the designated depth. By utilizing the characteristic of the tapered steel pipe extension section 4 to penetrate deep into the lower strata of the structure, the geothermal energy stored in the bottom strata can be quickly transferred to the vicinity of the heat pump exchange pipe component 8 through the high thermal conductivity of steel, thereby improving the geothermal exchange efficiency of the energy pile structure. By utilizing the large volume of the pile body formed by the bag grouting technology and the good thermal conductivity of CFRP, the geothermal energy around the pile body can be quickly transferred to the heat pump exchange pipe component 8. With a larger geothermal exchange area, a longer geothermal exchange distance, and a faster geothermal conduction speed than existing energy pile structures, the geothermal energy utilization efficiency is significantly improved.

Claims

1. An energy pile structure based on CFRP toughened fabric bag grouting technology, characterized in that, include: The structure comprises a core hollow-core steel-concrete composite member, a steel pipe extension section, an outer reinforced concrete component, a heat pump exchange pipe component, a CFRP (Crystal Reinforced Polymer) fabric-reinforced heat transfer network, and a geotextile bag. The core hollow-core steel-concrete composite member is located in the center of the overall structure and consists of an inner steel pipe, an outer steel pipe, and core concrete, with the core concrete filling the gap between the inner and outer steel pipes. The steel pipe extension section is located at the bottom of the core hollow-core steel-concrete composite member and consists of a tapered steel pipe extension section and an outer steel pipe skirt. The tapered steel pipe extension section penetrates the bottom of the geotextile bag and connects to the bottom of the outer steel pipe. The outer steel pipe skirt is circumferentially set on the tapered steel pipe extension section. The outer reinforced concrete component surrounds the core hollow-core steel-concrete composite member and is made of reinforced concrete. The component consists of an outer concrete casing and a reinforcing cage. The reinforcing cage is encased around the core hollow steel-concrete composite structure, and the outer concrete casing fills the space between the core hollow steel-concrete composite structure and the geotextile bag. The heat pump exchange pipe component consists of a heat pump exchange spiral pipe and a heat pump exchange straight pipe. The heat pump exchange spiral pipe is located outside the reinforcing cage, and the heat pump exchange straight pipe is located inside the inner steel pipe. The bottom of the heat pump exchange spiral pipe passes through a pre-reserved hole in the extension section of the tapered steel pipe and connects to the bottom of the heat pump exchange straight pipe. The CFRP cloth toughened heat transfer network consists of a CFRP cloth toughening network and a CFRP cloth heat transfer network. The CFRP cloth toughening network is located inside the geotextile bag, and the CFRP cloth heat transfer network is located within the outer concrete casing. The geotextile bag is located outside the outer concrete casing.

2. The energy pile structure based on CFRP toughened fabric bag grouting technology according to claim 1, characterized in that: The inner steel pipe and the outer steel pipe are arranged concentrically.

3. The energy pile structure based on CFRP toughened fabric bag grouting technology according to claim 1, characterized in that: The inner steel pipe is a circular steel pipe or a polygonal steel pipe, and the outer steel pipe is a circular steel pipe or a polygonal steel pipe.

4. The energy pile structure based on CFRP toughened fabric bag grouting technology according to claim 1, characterized in that: The steel cage is made by binding longitudinal bars and stirrups wrapped around the longitudinal bars.

5. An energy pile structure based on CFRP toughened fabric bag grouting technology according to claim 1, characterized in that: The CFRP fabric toughening network is formed by pasting CFRP fabric in a crisscross pattern onto the inside of a geotextile bag.

6. The energy pile structure based on CFRP toughened fabric bag grouting technology according to claim 1, characterized in that: The CFRP cloth heat transfer network is formed by wrapping and pasting CFRP cloth onto the heat pump exchange spiral tube.

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