Combined negative carbon stiff mixing pile and construction method

Abstract

The invention discloses a combined negative carbon stiff mixing pile and a construction method, and belongs to the technical field of mixing pile carbonization and reinforcement processes. Semicircular hollow hoops are tightly connected to the outer wall of a hollow prefabricated pipe pile through a strong double-faced adhesive layer pre-coated on the inner wall in advance; the ventilation connecting pipes and the semicircular hollow hoops are sequentially arranged at equal intervals from top to bottom and are connected in series to form a communicating system; after the construction of the soft soil foundation stirring pile prepared from the industrial solid waste-based negative carbon alkali-activated gel for grouting is finished, the prefabricated pipe pile is inserted into the stirring pile; and after the mixing pile is solidified to the expected age, a CO2 aerostatic press is connected through an inlet of a connecting pipe of the negative carbon ventilation system at the top of the pile to convey carbon dioxide, and carbonization and mineralization construction is completed on the whole stiff composite pile body. According to the combined negative carbon stiff mixing pile and the construction method, the construction cost is effectively reduced, meanwhile, more exhaust hole positions are arranged, the migration and diffusion efficiency of carbon dioxide in the mixing pile body is improved, and the uniformity of the carbonization effect is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of carbonization reinforcement technology for mixing piles, and in particular to a combined negative carbon stiff mixing pile and a construction method. Background Art

[0002] With the rapid development of my country's coastal economy, the scale of infrastructure construction is gradually expanding, but the available land resources are becoming less and less. Soft soil foundations with low strength are often encountered during construction. Soft soil foundations have the characteristics of low strength, high compressibility, high natural water content and high disturbance. Uneven settlement and foundation instability often occur during road and building construction, posing great safety hazards to construction safety. Cement soil mixing piles are a commonly used pile type for soft soil foundation treatment. They are low in cost and simple to construct, but the pile body strength is very low, the deformation is large and the construction quality is difficult to control. In order to further enhance the bearing capacity of the pile body, rigid mixing piles came into being.

[0003] The rigid mixing pile is a new type of pile formed by inserting a high-strength pipe pile into a cement mixing pile. It can be used in foundations such as silt, silty soil, clay soil, silt, sandy soil, and artificial fill. The cement-soil mixing pile uses a large contact area to provide lateral friction resistance, while the high-strength precast concrete pile is used to bear the vertical load, so that the advantages of the two types of piles can be fully utilized at the same time. It has the characteristics of simple construction, reliable quality, good economy, and high bearing capacity. Application No. 202010971390.2 uses the hollow steel pipe as part of the mixing pile, so that the cement-soil mixing pile on the outside of the hollow steel pipe can be separated from the cast-in-place concrete pile on the inside of the hollow steel pipe, effectively solving the problems of soil squeezing and eccentricity between the cement-soil mixing pile and the cast-in-place concrete pile, and improving the bearing capacity of the composite pile; for example, Application No. 202321953073.3 proposes a rigid composite pile suitable for sand geological conditions, including an outer core and an inner core, the outer core is a cement-soil pile, and the inner core is a PHC pipe pile, which can effectively improve the bearing capacity of a single pile, and can greatly reduce the pile length and foundation settlement under the same bearing capacity. The above cases and conventional rigid mixing pile construction methods all use high-energy consumption and high-emission cement as a soil curing agent, and achieve good construction results at the cost of being unfriendly to the environment and increasing carbon emission pressure.

[0004] During the construction of mixing piles, cement will react with CO2 in the air to form carbonate products. The calcite, aragonite or pyroxene produced makes the original cement stone structure more compact, improving the mechanical properties and durability of concrete. This is actually a manifestation of the "carbon neutrality" of concrete. In addition, industrial solid waste such as mineral powder and fly ash are mainly composed of silicon-, aluminum- and calcium-based compounds, which can be used as curing agent raw materials or additives. Under reasonable ratio design, they can partially or completely replace cement for engineering construction.

[0005] However, like the industrial solid waste-based alkali-activated gel material curing agent, there are currently few domestic engineering cases for the construction of carbonized mixing piles, which are insufficient for reference. In order to respond to the energy-saving and emission reduction policies and the dual-carbon strategic development tasks, combined with the shortcomings and problems in the current reinforcement technology of soft soil foundation composite piles and carbonization reinforcement methods, it is urgent to invent a new, convenient and low-cost negative carbon stiffening mixing pile construction method. Summary of the invention

[0006] The purpose of the present invention is to provide a combined negative carbon rigid mixing pile and construction method, which realizes high-value recycling of solid waste and enhances the interaction between hollow prefabricated pipe piles and solidified soil through the rib effect of the combined negative carbon ventilation device and carbonization mineralization, and also improves the strength of the rigid composite pile and the bearing capacity of the composite foundation.

[0007] To achieve the above-mentioned purpose, the present invention provides a combined negative carbon rigid mixing pile, including a combined negative carbon ventilation device, the combined negative carbon ventilation device includes a semicircular hollow clamp and a ventilation connecting pipe, the adjacent combined negative carbon ventilation devices are fixed on the outer wall of the hollow prefabricated pipe pile along the axial direction of the hollow prefabricated pipe pile, and the hollow prefabricated pipe pile is integrally inserted and embedded in the industrial solid waste-based negative carbon alkali-induced gel-solidified soil mixing pile.

[0008] Preferably, a negative carbon ventilation system connecting pipe is provided on the pile top of the hollow prefabricated pipe pile, and the negative carbon ventilation system connecting pipe is connected to the CO2 compressor.

[0009] Preferably, the semicircular hollow clamp is hollow inside, and the semicircular hollow clamp comprises an outer layer hoop, a one-way membrane and an inner layer hoop from the outside to the inside. The semicircular hollow clamp is formed by nesting the outer layer hoop and the inner layer hoop, and the ventilation connecting pipe is vertically connected to the middle of the semicircle of the semicircular hollow clamp.

[0010] Preferably, the outer hoop of the semicircular hollow clamp has four groups of exhaust holes evenly spaced along the center line of the circle, the one-way membrane at the exhaust holes is not cut and is filled with permeable stone, crushed stone and reticulated foam plastic in sequence, and an insect-proof net is provided outside the exhaust holes.

[0011] Preferably, 8 groups of protruding nails are evenly distributed on the outer edge of the inner hoop, and circular positioning holes are left at corresponding positions on the inner edge of the outer hoop. The inner hoop and the outer hoop are fixedly connected through the positioning holes and the protruding nails, and corresponding openings are opened on the one-way membrane at the protruding nails.

[0012] Preferably, the ventilation connecting tube is a PVC hollow tube with a diameter of 4-6 cm, the exhaust hole has a diameter of 2-4 cm, the protruding nail of the inner hoop has a diameter of 1-2 cm and a height of 2-4 cm, the positioning hole on the outer hoop has a diameter 1-2 mm wider than the diameter of the protruding nail, and the depth of the positioning hole is consistent with the height of the protruding nail.

[0013] Preferably, the hollow prefabricated pipe pile is a reinforced concrete prefabricated pile, the pile body of which is hollow and has rubber plugs at both ends. The outer diameter of the hollow prefabricated pipe pile is 400-800 mm and the inner diameter is 150-400 mm.

[0014] The present invention also provides a construction method of a combined negative carbon stiff mixing pile, comprising the following steps:

[0015] Step 1: Bond the semicircular hollow clamp to the outer wall of the pile through the strong double-sided adhesive layer pre-applied on the inner wall, and arrange them in the order of ventilation connecting pipe-semicircular hollow clamp from top to bottom to form a connection system in series, and ensure the connection sealing through water pressure test;

[0016] Step 2: Put the pile mixing machine in place and align the pile machine drill rod and drill bit vertically with the predetermined pile position;

[0017] Step 3: Start the pile mixing machine and penetrate it into the foundation soil until the spiral drill bit is spun into the set depth;

[0018] Step 4: Switch the mixing pile machine to the lifting state. While lifting, the nozzle near the drill bit sprays the industrial solid waste base alkali-induced gel material curing agent, and then repeatedly stirs twice according to the same steps to mix the curing agent and the foundation soil evenly, completing the preliminary forming of the mixing pile body;

[0019] Step 5: Before the mixing pile body is solidified, a hollow prefabricated pipe pile equipped with a combined negative carbon ventilation device is vertically inserted into the industrial solid waste-based negative carbon alkali-induced gel-solidified soil mixing pile;

[0020] Step 6. After the mixing pile solidifies to the expected age, the CO2 compressor is connected to the inlet of the pile top negative carbon ventilation system connecting pipe arranged on the top of the combined negative carbon ventilation device to transport carbon dioxide to the entire rigid composite pile body for carbonization and mineralization until the construction of the combined negative carbon rigid mixing pile is completed.

[0021] Preferably, the mass proportions of the components in the industrial solid waste-based alkali-induced gel material in step four are: mineral powder 25-35%, fly ash 10-15%, attapulgite 15-20%, magnesium oxide 15-25%, quicklime 15-20%, sodium silicate 10-15%, and the water-cement ratio is 0.7:1-1.1:1.

[0022] Preferably, in step six, the carbonization time is 1-2 days, and the gas injection pressure is 0.2-0.3 MPa.

[0023] The present invention arranges the combined negative carbon ventilation system at a certain interval along the length direction of the prefabricated pipe pile in advance and connects them in series through the ventilation connecting pipe to form a communication system, ensures the connection sealing through a water pressure test, and then uses industrial solid waste-based negative carbon alkali gel to prepare grouting for soft soil foundation mixing pile construction, and inserts the prefabricated pipe pile into the mixing pile after the construction is completed, and finally connects the air compressor to the inlet of the negative carbon ventilation system connecting pipe on the pile top to transport carbon dioxide to realize carbonization and mineralization of the entire rigid composite pile body after the mixing pile is solidified to the expected age, and the construction of the negative carbon rigid mixing pile is completed. The synergistic effect of the mixing pile and the cement concrete pile is achieved, which not only enhances the bearing capacity of the foundation, but also plays a positive role in carbon fixation and emission reduction.

[0024] Therefore, the present invention adopts the above-mentioned combined negative carbon stiff mixing pile and construction method, which has the following beneficial effects:

[0025] (1) Using industrial solid waste-based alkali-activated cementitious materials as a curing agent for foundation soil can achieve the recycling of industrial solid waste while ensuring the reinforcement effect, reduce energy consumption during construction, and be environmentally friendly;

[0026] (2) Carbonization and mineralization of mixing piles are carried out to achieve the synergistic effect of mixing piles and cement concrete piles, which not only enhances the bearing capacity of the foundation, but also plays a positive role in carbon sequestration and emission reduction;

[0027] (3) The combined negative carbon ventilation device of the present invention can be used to perform carbonization and mineralization of the mixing pile, which can avoid drilling holes in the prefabricated pipe piles, effectively reducing the construction cost. At the same time, more exhaust holes can be arranged, increasing the migration and diffusion efficiency of carbon dioxide in the mixing pile body, and ensuring the uniformity of the carbonization effect;

[0028] (4) The multi-layer circular clamps are connected to the outside of the pipe pile, which increases the side friction resistance between the prefabricated pipe pile and the mixing pile, and improves the bearing capacity of the rigid mixing pile to a certain extent;

[0029] (5) The combined negative carbon ventilation device proposed in the present invention is independent of the prefabricated pipe piles, and is convenient to construct and simple to operate. At the same time, its combined installation design can be reused in special circumstances or the layout of the composite piles can be adjusted in time when pile formation fails;

[0030] (6) The grouting materials for mixing piles are industrial solid wastes such as mineral powder and fly ash. According to the mixing ratio proposed in the present invention, higher strength can be achieved in a shorter time after negative carbonization, which is different from traditional cement-based solidifying materials and provides a new idea for solving the problems of high energy consumption and serious environmental pollution in actual construction.

[0031] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a structural schematic diagram of a combined negative carbon ventilation device of an embodiment of a combined negative carbon rigid mixing pile and a construction method of the present invention;

[0033] Figure 2 It is a cross-sectional view of a combined negative carbon ventilation device of an embodiment of a combined negative carbon rigid mixing pile and a construction method of the present invention;

[0034] Figure 3 It is an exploded view of a semicircular hollow clamp of an embodiment of a combined negative carbon stiff mixing pile and a construction method of the present invention;

[0035] Figure 4 It is a schematic diagram of the inner hoop structure of an embodiment of a combined negative carbon stiff mixing pile and a construction method of the present invention;

[0036] Figure 5 It is a load displacement curve diagram of a rigid mixing pile in an embodiment of a combined negative carbon rigid mixing pile and a construction method of the present invention;

[0037] Figure 6 It is a graph showing the change of the side friction force of the uncarbonized rigid mixing pile before and after the application of upper layer loads of different sizes in an embodiment of a combined negative carbon rigid mixing pile and a construction method of the present invention;

[0038] Figure 7 It is a graph showing the change of the side friction force of the carbonized post-reinforced stirring pile before and after the application of upper layer loads of different sizes in an embodiment of a combined negative carbon resilient stirring pile and a construction method of the present invention;

[0039] Figure 8 It is a H-ΔY0 / ΔH (horizontal force-displacement gradient) curve diagram of a rigid mixing pile of a combined negative carbon rigid mixing pile and a construction method embodiment of the present invention under the action of a horizontal load.

[0040] Reference numerals

[0041] 1. Semicircular hollow clamp; 2. Ventilation connecting pipe; 3. Negative carbon ventilation system connecting pipe; 4. Exhaust hole; 5. Strong double-sided adhesive layer; 6. Protruding nails; 7. One-way membrane; 8. Inner hoop; 9. Outer hoop. DETAILED DESCRIPTION

[0042] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0043] Unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0044] Embodiment 1

[0045] like Figures 1 to 4 As shown, the present invention provides a combined negative carbon stiff mixing pile, and the mixing pile grouting material adopts industrial solid waste-based negative carbon alkali-activated cementitious material, the specific mass proportion is 25-35% of mineral powder, 10-15% of fly ash, 15-20% of attapulgite, 15-25% of magnesium oxide, 15-20% of quicklime, 10-15% of sodium silicate, the water-cement ratio is 0.7-1.1, and the dosage of industrial solid waste-based alkali-activated cementitious material is 15-30%. Using industrial solid waste as raw materials can effectively reduce waste emissions, reduce environmental pollution, and conform to the concept of sustainable development. As a mixing pile grouting material, it can effectively penetrate and solidify loose soil, improve the mechanical properties of soil, such as compressive strength and shear strength, thereby increasing the stability and bearing capacity of the foundation. Alkali-activated reaction can activate the silicon-aluminum components in industrial solid waste to form a cementitious material similar to cement. This chemical reaction can not only quickly solidify, but also form a strong bond between soil particles, which is suitable for foundation reinforcement, anti-seepage treatment and other purposes.

[0046] A combined negative carbon rigid mixing pile includes a combined negative carbon ventilation device, which includes a semicircular hollow clamp 1 and a ventilation connecting pipe 2. The semicircular hollow clamp 1 plays a role of reinforcement and positioning, and the ventilation connecting pipe 2 plays a role of exhaust. Adjacent combined negative carbon ventilation devices are fixed on the outer wall of the hollow prefabricated pipe pile at intervals of 30-35cm along the axial direction of the hollow prefabricated pipe pile, and the hollow prefabricated pipe pile is integrally inserted and embedded in the industrial solid waste-based negative carbon alkali gel-cured soil mixing pile. A negative carbon ventilation system connecting pipe 3 is provided on the top of the hollow prefabricated pipe pile, and the negative carbon ventilation system connecting pipe 3 is connected to a CO2 compressor. The negative carbon ventilation system connecting pipe 3 is used to connect the hollow prefabricated pipe pile and the CO2 compressor. The CO2 compressor is used to transport carbon dioxide to achieve carbonization and mineralization of the entire rigid composite pile body.

[0047] The semicircular hollow clamp 1 is hollowed out inside. From outside to inside, the semicircular hollow clamp 1 is composed of an outer layer hoop 9, a one-way membrane 7 and an inner layer hoop 8. The one-way membrane 7 can play a role of ventilation without liquid. The semicircular hollow clamp 1 is formed by the outer layer hoop 9 and the inner layer hoop 8 being nested. A ventilation connecting pipe 2 is vertically connected to the middle of the semicircle of the semicircular hollow clamp 1. The connection uses a buckle design to realize the ventilation design between the upper and lower structures.

[0048] The outer hoop 9 of the semicircular hollow clamp 1 has four groups of exhaust holes 4 evenly spaced along the center line of the circle. The one-way membrane 7 at the exhaust holes 4 is not cut open and is filled with permeable stones, crushed stones and reticulated foam plastics in sequence. An insect-proof net is provided outside the exhaust holes 4 to ensure gas discharge and prevent mud from seeping in from the outside of the pile.

[0049] There are 8 groups of protruding nails 6 evenly distributed on the outer edge of the inner hoop 8, and circular positioning holes are left at the corresponding positions of the inner edge of the outer hoop 9. The inner hoop 8 and the outer hoop 9 are fixedly connected through the positioning holes and the protruding nails 6, and corresponding openings are opened on the one-way membrane 7 at the protruding nails 6 for passing the protruding nails 6.

[0050] The ventilation connecting pipe 2 is a PVC hollow tube with a diameter of 4-6cm, the exhaust hole 4 has a diameter of 2-4cm, the protruding nail 6 of the inner hoop 8 has a diameter of 1-2cm and a height of 2-4cm, the positioning hole on the outer hoop 9 has a diameter 1-2mm wider than the diameter of the protruding nail 6, and the depth of the positioning hole is consistent with the height of the protruding nail 6.

[0051] Hollow prefabricated pipe piles are reinforced concrete prefabricated piles with a hollow pile body and rubber plugs at both ends. The outer diameter of the hollow prefabricated pipe piles is 400-800mm and the inner diameter is 150-400mm. The rubber plugs seal and protect the hollow prefabricated pipe piles and prevent water loss.

[0052] Embodiment 2

[0053] The present invention also provides a construction method of a combined negative carbon stiff mixing pile, comprising the following steps:

[0054] Step 1: Bond the semicircular hollow clamp 1 to the outer wall of the pile through the strong double-sided adhesive layer 5 pre-applied on the inner wall, and arrange the ventilation connecting pipe 2-semicircular hollow clamp 1 in order from top to bottom to form a connected system in series, and ensure the connection sealing through a water pressure test;

[0055] Step 2: Put the pile mixing machine in place and align the pile machine drill rod and drill bit vertically with the predetermined pile position;

[0056] Step 3: Start the pile mixing machine and penetrate it into the foundation soil until the spiral drill bit is spun into the set depth;

[0057] Step 4: Switch the mixing pile machine to the lifting state. While lifting, the nozzle near the drill bit sprays the industrial solid waste base alkali-induced gel material curing agent, and then repeatedly stirs twice according to the same steps to mix the curing agent and the foundation soil evenly, completing the preliminary forming of the mixing pile body;

[0058] Step 5: Before the mixing pile body solidifies, vertically insert the hollow prefabricated pipe pile equipped with the combined negative carbon ventilation device into the mixing pile;

[0059] Step 6: When the carbonization time comes, connect the CO2 air compressor through the negative carbon ventilation system connecting pipe 3 on the hollow prefabricated pipe pile, and carbonize the mixing pile to form a carbonized mixing pile. The injection pressure of the CO2 air compressor is 0.2-0.3MPa, and the carbonization time of carbonization is 1-2d.

[0060] Embodiment 3

[0061] A construction method for a combined negative carbon stiff mixing pile comprises the following steps:

[0062] (1) Clean the natural ground, lay out the lines and measure, and determine the pile positions;

[0063] (2) preparing a gel material by mixing 26.2% of mineral powder, 12.4% of fly ash, 15.7% of attapulgite, 15.3% of magnesium oxide, 16.2% of quicklime, and 14.2% of sodium silicate in a mass ratio, and making a slurry in a mixer at a water-cement ratio of 0.9:1;

[0064] (4) Using 39.1% mineral powder, 31.2% fly ash, 23.4% metakaolin, and 6.3% sodium silicate at a water-cement ratio of 0.3:1, cast hollow prefabricated pipe piles with an inner diameter of 300 mm and an outer diameter of 600 mm, and carbon curing them for 1 day after molding;

[0065] (5) Connect the semicircular hollow clamp 1 to the outside of the pile through the strong double-sided adhesive layer 5, and connect the ventilation connecting pipe 2. The adjacent devices are fixed to the outer edge of the pile at intervals of 30 cm along the axial direction of the hollow prefabricated pile;

[0066] (6) Drilling a pile at a preset pile position using a pile mixing machine with a pile hole diameter of 1000 mm. When the pile reaches a preset depth of 8 m, the drill bit is lifted and the gel slurry is sprayed at a rate of 55 kg / m3 and stirred twice in the soil layer;

[0067] (7) Remove the pile mixing machine and vertically insert the hollow prefabricated pipe pile into the pile before the pile solidifies;

[0068] (8) Cover the upper end of the air-permeable pile with a sealing bag to protect the pile core and the uppermost negative carbon ventilation system connecting pipe 3 in preparation for normal operation, waiting for the mixing pile to harden;

[0069] (9) Connect the negative carbon ventilation system connecting pipe 3, inject CO2 gas with a pressure of 0.2 MPa, and carbonize the composite pile for 24 hours.

[0070] Figure 5 The load displacement curve of the rigid mixing pile shows that when the load increases from 0 to 160 kN, the displacement can maintain a stable increase. The load value corresponding to the starting point of the obvious steep change is taken as the limit value of the vertical compressive bearing capacity of the single pile. Therefore, the vertical compressive ultimate bearing capacity of the test pile is 160 kN. The ultimate bearing capacity of the rigid mixing pile does not change significantly before and after carbonization, but the vertical displacement of the pile after carbonization is significantly reduced under the same load. For example, when the load is 200 kN, the displacement of the carbonized pile is 29.76 mm, and the displacement of the non-carbonized pile is 35.84 mm, and the displacement of the carbonized pile is reduced by 16.96%.

[0071] Figure 6 and Figure 7 When the rigid composite pile is affected by upper loads of different sizes, its lateral friction will change with the change of depth. Figure 6 The figure is the change of the side friction force of the uncarbonized rigid mixing pile before and after the application of different upper loads. Figure 7 The following is a graph showing the change in the lateral friction of a carbonized reinforced mixing pile before and after the application of different upper loads. This graph can be used to easily determine the bearing capacity and distribution law of the inner and outer cores of each part during the pile foundation design, providing a basis for the design of pile foundation engineering. As can be seen from the figure, the lateral friction of the interface between the inner and outer core piles of the reinforced composite pile will increase with the increase of the pile top load, and will first increase and then decrease along the depth direction. When the pile top load is 240kN and the depth is 1m, the uncarbonized pile ( Figure 6 ) Side friction resistance 127kPa, carbonized pile ( Figure 7 ) side friction resistance is 146kPa, an increase of 14.9% year-on-year; when the pile top load is 200kN and the depth is 1m, the uncarbonized pile ( Figure 6 ) Side friction resistance 115kPa, carbonized pile ( Figure 7 ) The side friction resistance is 142kPa, an increase of 23.4% year-on-year.

[0072] Figure 8 The figure shows the H-ΔY0 / ΔH (horizontal force-displacement gradient) curve of the rigid mixing pile under horizontal load. It can be seen from the figure that the critical load after carbonization is 170kN and the ultimate load is 100kN. When the load is 100kN, the displacement gradient of the carbonized pile is 0.2mm / kN, and the displacement gradient of the uncarbonized pile is 0.65mm / kN. The displacement gradient of the carbonized pile has decreased by 69.2% year-on-year.

[0073] Therefore, the present invention adopts the above-mentioned combined negative carbon rigid mixing pile and construction method. The carbonization and mineralization of the mixing pile is carried out through the combined negative carbon ventilation device, which can avoid opening holes in the prefabricated pipe piles and effectively reduce the construction cost. At the same time, more exhaust holes can be arranged to increase the migration and diffusion efficiency of carbon dioxide in the mixing pile body and ensure the uniformity of the carbonization effect. The synergistic effect between the mixing pile, the hollow prefabricated pipe pile and the combined negative carbon ventilation device can improve the bearing capacity and lateral friction resistance of the pile body. At the same time, carbonization is beneficial to improving the horizontal bearing capacity of the rigid mixing pile. It is connected to the outside of the hollow prefabricated pipe pile through multiple layers of semicircular hollow clamps, which increases the lateral friction between the hollow prefabricated pipe pile and the mixing pile, thereby improving the bearing capacity of the rigid mixing pile.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A combined negative carbon stiff mixing pile, characterized in that: It comprises a combined negative carbon ventilation device, which comprises a semicircular hollow clamp and a ventilation connecting pipe. Adjacent combined negative carbon ventilation devices are fixed on the outer wall of the hollow prefabricated pipe pile along the axial direction of the hollow prefabricated pipe pile. The hollow prefabricated pipe pile is integrally inserted and embedded in an industrial solid waste-based negative carbon alkali-induced gel-cured soil mixing pile.

2. The combined negative carbon stiff mixing pile according to claim 1, characterized in that: A negative carbon ventilation system connecting pipe is provided on the top of the hollow prefabricated pipe pile, and the negative carbon ventilation system connecting pipe is connected to the CO2 compressor.

3. The combined negative carbon stiff mixing pile according to claim 1, characterized in that: The interior of the semicircular hollow clamp is hollowed out, and the semicircular hollow clamp comprises an outer layer hoop, a one-way membrane and an inner layer hoop from the outside to the inside. The semicircular hollow clamp is formed by the outer layer hoop and the inner layer hoop being nested, and the ventilation connecting pipe is vertically connected to the middle of the semicircle of the semicircular hollow clamp.

4. The combined negative carbon stiff mixing pile according to claim 3, characterized in that: The outer hoop of the semicircular hollow clamp has four groups of exhaust holes distributed at equal intervals along the center line of the circle, the one-way membrane at the exhaust holes is not cut and is filled with permeable stones, crushed stones and mesh foam plastics in sequence, and an insect-proof net is arranged outside the exhaust holes.

5. The combined negative carbon stiff mixing pile according to claim 4, characterized in that: The outer edge of the inner hoop is provided with 8 groups of protruding nails at equal intervals, and a circular positioning hole is left at the corresponding position of the inner edge of the outer hoop. The inner hoop and the outer hoop are fixedly connected through the positioning holes and the protruding nails, and corresponding openings are opened on the one-way membrane at the protruding nails.

6. The combined negative carbon stiff mixing pile according to claim 5, characterized in that: The ventilation connecting tube is a PVC hollow tube with a diameter of 4-6cm, the exhaust hole has a diameter of 2-4cm, the protruding nail of the inner hoop has a diameter of 1-2cm and a height of 2-4cm, the positioning hole on the outer hoop has a diameter 1-2mm wider than the diameter of the protruding nail, and the depth of the positioning hole is consistent with the height of the protruding nail.

7. The combined negative carbon stiff mixing pile according to claim 1, characterized in that: The hollow prefabricated pipe pile is a reinforced concrete prefabricated pile, the pile body of which is hollow and has rubber plugs at both ends. The outer diameter of the hollow prefabricated pipe pile is 400-800mm and the inner diameter is 150-400mm.

8. A construction method for a combined negative carbon stiff mixing pile according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1: Bond the semicircular hollow clamp to the outer wall of the pile through the strong double-sided adhesive layer pre-applied on the inner wall, and arrange them in the order of ventilation connecting pipe-semicircular hollow clamp from top to bottom to form a connection system in series, and ensure the connection sealing through water pressure test; Step 2: Put the pile mixing machine in place and align the pile machine drill rod and drill bit vertically with the predetermined pile position; Step 3: Start the pile mixing machine and penetrate it into the foundation soil until the spiral drill bit is spun into the set depth; Step 4: Switch the mixing pile machine to the lifting state. While lifting, the nozzle near the drill bit sprays the industrial solid waste base alkali-induced gel material curing agent, and then repeatedly stirs twice according to the same steps to mix the curing agent and the foundation soil evenly, completing the preliminary forming of the mixing pile body; Step 5: Before the mixing pile body is solidified, a hollow prefabricated pipe pile equipped with a combined negative carbon ventilation device is vertically inserted into the industrial solid waste-based negative carbon alkali-induced gel-solidified soil mixing pile; Step 6. After the mixing pile solidifies to the expected age, the CO2 compressor is connected to the inlet of the pile top negative carbon ventilation system connecting pipe arranged on the top of the combined negative carbon ventilation device to transport carbon dioxide to the entire rigid composite pile body for carbonization and mineralization until the construction of the combined negative carbon rigid mixing pile is completed.

9. The construction method of a combined negative carbon stiff mixing pile according to claim 8, characterized in that: The mass proportions of the components in the industrial solid waste-based alkali-induced gel material in the step four are: mineral powder 25-35%, fly ash 10-15%, attapulgite 15-20%, magnesium oxide 15-25%, quicklime 15-20%, sodium silicate 10-15%, and the water-cement ratio is 0.7:1-1.1:

1.

10. The construction method of a combined negative carbon stiff mixing pile according to claim 8, characterized in that: In step six, the carbonization time is 1-2 days, and the gas injection pressure is 0.2-0.3 MPa.

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