Self-adaptive modified waste mud carbon sequestration environment-friendly pile and preparation method and application thereof

Abstract

The invention belongs to the technical field of civil engineering, and discloses a self-adaptive modified waste slurry carbon sequestration environment-friendly pile and a preparation method and application thereof.The preparation method comprises the following specific steps that (1) waste slurry is sieved, and impurities are removed for standby application; (2) a curing agent is added into the waste mud obtained in the step (1) and mixed to be uniform, modified waste mud is obtained, and the curing agent is prepared from, by mass, 60%-80% of slag, 20%-30% of an alkali activator, 5%-15% of industrial byproduct gypsum, 5%-10% of charcoal and 0-0.5% of a composite additive; and (3) adding the modified waste slurry into a mold, and performing drainage consolidation and maintenance to obtain the self-adaptive modified waste slurry carbon sequestration environment-friendly pile. According to the method, green high-added-value recycling of the waste mud and comprehensive utilization of a large amount of solid waste can be achieved, the treatment cost is reduced while carbon reduction and carbon sequestration are achieved, the soft soil foundation is effectively reinforced and improved, the problem of foundation settlement is solved, and the bearing capacity is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of civil engineering, and in particular relates to an adaptive modified waste mud carbon fixation environmental protection pile and a preparation method and application thereof. Background Art

[0002] With the increasing number of projects, the construction of high-grade roads has developed rapidly. Due to the differences in geological conditions of high-grade roads, many roads are built on soft soil foundations, but the soft soil foundation has obvious unfavorable characteristics such as thixotropy, high compressibility and low strength, which cause serious harm to the roadbed, so it must be treated.

[0003] When reinforcing the roadbed foundation in soft soil layers during urban infrastructure construction, conventional methods include prefabricated pipe pile reinforcement, CFG pile reinforcement, cement soil mixing pile reinforcement or bulk material pile reinforcement. However, prefabricated pipe pile and CFG pile reinforcement are expensive and do not perform well in soft soil layers. Cement soil mixing piles have poor permeability, which is not conducive to the drainage and consolidation of soil between piles. Bulk material piles have weak integrity and are prone to swelling damage after loading.

[0004] At the same time, a large amount of waste mud will be generated during the development of urban underground space construction, dredging projects, and island and reef projects. The engineering properties of waste mud are poor, and its stacking requires a long time and a large area of ​​land, and it is easy to cause environmental pollution and difficult to handle. The conversion of waste excavated geological materials into engineering materials through chemical modification can effectively solve the land use and pollution problems of the yard, and has good economic and environmental benefits. At present, in the resource treatment of waste excavated geological materials, a common method is to chemically modify cement-based materials to improve their mechanical properties, but cement is a high-carbon emission material, and the use of cement-based materials to treat waste excavated geological materials is not in line with the concept of environmental protection. In addition, large amounts of solid waste generated by industrial activities, such as blast furnace slag and industrial by-product gypsum, have not been effectively utilized, and large amounts of accumulation will also cause environmental pollution and waste of resources.

[0005] If waste mud can be modified and used as pile material to treat soft soil foundation, it can reduce land resource consumption and environmental pollution, and can effectively strengthen and improve soft soil foundation, reduce foundation settlement problems and improve bearing capacity. However, there is no relevant research in the prior art. Therefore, it is an urgent problem for technicians in this field to provide an adaptive modified waste mud carbon fixation environmentally friendly pile and a preparation method thereof. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides an adaptive modified waste mud carbon fixation environmentally friendly pile and its preparation method and application. The method of the present invention can realize the green and high value-added recycling of waste mud and the comprehensive utilization of bulk solid waste, reduce carbon and fix carbon while reducing processing costs, effectively reinforce and improve soft soil foundations, reduce foundation settlement problems and improve bearing capacity.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A method for preparing an adaptive modified waste mud carbon fixation environmental protection pile comprises the following specific steps:

[0009] (1) Screen the waste mud to remove impurities and set aside;

[0010] (2) adding a curing agent to the waste mud obtained in step (1) and mixing them evenly to obtain modified waste mud, wherein the curing agent comprises the following raw materials in percentage by weight: 60-80% slag, 20-30% alkali activator, 5-15% industrial by-product gypsum, 5-10% biochar and 0-0.5% composite admixture;

[0011] (3) Adding the modified waste mud into a mold, draining, consolidating and curing the mold to obtain an adaptive modified waste mud carbon fixation environmentally friendly pile.

[0012] Since slag itself has potential hydraulic hardness in the curing agent, it will produce good activity after chemical stimulation such as alkali stimulation and sulfate stimulation; the sulfate rich in industrial by-product gypsum has a good stimulation effect in an alkaline environment, and adding alkaline substances and industrial by-product gypsum to slag can achieve two-way stimulation of alkali stimulation and sulfate stimulation; due to the physical and chemical differences between slag cementitious materials and cement, its curing effect is better than cement, which makes slag have the potential to replace high-carbon emission curing materials such as cement; biochar is a product produced by thermal cracking of biomass raw materials, and is usually used as a soil conditioner in agricultural production. Since biochar has rich pore structure, high chemical stability and contains functional groups such as carboxyl and phenolic hydroxyl groups on its surface Energy group, a large amount of CO2 will be consumed during the carbonization process, and it can absorb CO2 in the air. It is a very potential carbon fixation material. The CO2 adsorbed by biochar can react with calcium ions in the solidifying material to generate calcium carbonate crystals, and can also react with alkaline oxides in the solidifying material to generate corresponding carbonates; in addition, in an alkaline environment, the CO2 adsorbed by biochar can participate in the volcanic ash reaction to form a gelling product CSH, and these reaction products can increase the density, strength and stability of the material; at the same time, the functional groups such as carboxyl and phenolic hydroxyl groups on the surface of biochar can react chemically with the solidifying material to form a strong interface bond, generate a stable polymer network structure, wrap on the surface of biochar particles, and improve the durability of the material. Therefore, the introduction of biochar in the present invention can not only achieve the purpose of reducing carbon emissions and realize the function of increasing carbon sink capacity, but also improve the strength, bearing capacity and stability durability of the pile body.

[0013] Preferably, in step (2), the mass ratio of the curing agent to the waste mud is 1:7-8;

[0014] The stirring speed of the mixing is 60-180 rpm.

[0015] Preferably, the water content of the waste slurry in step (2) is 90-120%;

[0016] The slag has a specific surface area of ​​400-800 m2 / kg and a basicity greater than or equal to 1.0;

[0017] The particle size of the alkaline activator is less than 0.08 mm and the purity is more than 96%;

[0018] The average particle size of the industrial by-product gypsum is below 0.08 mm;

[0019] The main elements of the biochar include: C 46-79wt%, O 5-38wt%; the specific surface area of ​​the biochar is 300-550m 2 / kg, pore volume is 0.01-0.3cm 3 , pore size is 1-35nm;

[0020] The composite admixture is at least one of an accelerator, an early strength agent, a retarder and an antifreeze agent.

[0021] Preferably, the mold in step (3) is a permeable geotextile made of polypropylene yarns sewn together, and the structure thereof is a hollow cylinder after being filled with the modified waste mud;

[0022] The drainage consolidation adopts pipeline airbag expansion. When the pipeline airbag is fully expanded, the outer diameter is 18-25cm, the length is 1.5-3.5m, and the maximum pressure is 0.05MPa;

[0023] The curing temperature is 20±2°C and the humidity is above 90%.

[0024] Preferably, the inner diameter of the adaptive modified waste mud carbon fixation environmentally friendly pile in step (3) is 14-20 cm, the outer diameter is 50-60 cm, and the water content is 60-80%.

[0025] An adaptive modified waste mud carbon fixation environmentally friendly pile is obtained by the preparation method as described above.

[0026] As described above, an adaptive modified waste mud carbon fixation environmentally friendly pile is used in strengthening the foundation.

[0027] Preferably, the pile body in the reinforced foundation adopts the adaptive modified waste mud carbon fixation environmental protection pile, and the core material is slurry reinforced bulk material;

[0028] The slurry is modified waste mud, and the bulk material is sand and gravel excavated during the foundation drilling process or other solid waste that is difficult to reuse.

[0029] Preferably, the adaptive modified waste mud carbon fixation environmentally friendly piles are cut in the reinforced foundation to form holes, the holes are evenly distributed around the piles, and the upper and lower centers of the holes are spaced 1-3m apart.

[0030] Preferably, the specific construction method of reinforcing the foundation is:

[0031] 1) Cutting the adaptive modified waste mud carbon fixation environmental protection pile to form holes for standby use;

[0032] 2) Use the double casing method to drill a hole in the soil layer, drive it into the foundation to the elevation, and then pull out the inner tube together with the soil in the inner tube without vibration;

[0033] 3) The adaptive modified waste mud carbon fixation environmental protection pile obtained in step 1) is placed vertically on the ground according to the designed length, and a grouting pipe is inserted into the center of the adaptive modified waste mud carbon fixation environmental protection pile, which is connected to a grouting pump through a hose; then, the hollow position of the adaptive modified waste mud carbon fixation environmental protection pile is filled with bulk material to the ground height, which can overflow the pile body;

[0034] 4) Pull out the outer tube of the double-casing tube, and continue to put the bulk material into the adaptive modified waste mud carbon fixation environmental protection pile, so that it can overflow from the hole and fill around the adaptive modified waste mud carbon fixation environmental protection pile;

[0035] 5) Under the action of soil squeezing, the pore water in the soil layer around the pile is discharged along the bulk material in the middle of the adaptive modified waste mud carbon fixation environmentally friendly pile, and the pile and soil are adaptive. After the drainage in the surrounding soil layer is completed, the grouting pump is used to inject slurry into the bulk material along the grouting pipe. The slurry and the bulk material are consolidated and penetrate into the soil around the pile through the holes and the bulk material overflowing from the holes, and at the same time fill the entire internal cavity of the adaptive modified waste mud carbon fixation environmentally friendly pile, so that the bulk material, the adaptive modified waste mud carbon fixation environmentally friendly pile and the surrounding soil layer form a whole.

[0036] The method for reinforcing the foundation of the present invention can significantly reduce the settlement after construction. The surrounding soft soil layer is reinforced through the drainage channel function and grouting consolidation effect of the sand and gravel bulk materials, thereby significantly reducing the settlement after construction. At the same time, the bearing capacity and stability of the composite foundation are improved, and the modified waste mud piles are used to consolidate with the bulk materials and the surrounding soil into a whole, thereby greatly improving the bearing capacity and stability of the composite foundation.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] (1) The present invention converts waste mud into high value-added engineering materials through modification treatment, thereby realizing green and environmentally friendly recycling of waste mud, reducing the land occupation and environmental pollution problems of stacking, and having good economic and environmental benefits. At the same time, through the comprehensive utilization of large-scale solid wastes such as slag, industrial by-product gypsum and construction waste, efficient resource utilization is achieved, and environmental pollution and resource waste are reduced.

[0039] (2) The present invention introduces biochar as a carbon-fixing material, which not only consumes a large amount of carbon dioxide during the carbonization process, but also absorbs carbon dioxide in the air and reacts with solidifying materials to generate carbonates, thereby achieving the purpose of carbon reduction and carbon fixation, which is in line with the concept of environmental protection. By using waste mud and solid waste materials to replace cement, high energy consumption and high carbon emissions in cement production are avoided.

[0040] (3) The present invention uses a scientific ratio of industrial by-product gypsum, alkali activator, slag, biochar and other components to give full play to the characteristics and synergistic effects of each component, thereby improving the curing effect and material performance.

[0041] (4) The present invention combines the modified waste mud carbon fixation environmentally friendly piles with the slurry-stabilized bulk material, so that the pile body is self-adaptive and the bulk material can overflow from the pile body before grouting, thereby providing a drainage channel, reinforcing the surrounding soft soil layer, and significantly reducing post-construction settlement. After grouting, the slurry fills the pores of the bulk material and enters the surrounding soil through the bulk material channel, so that the bulk material, the modified waste mud carbon fixation environmentally friendly piles and the surrounding soil are solidified into a whole, thereby greatly improving the bearing capacity and stability of the composite foundation.

[0042] (5) The preparation method of the hollow adaptive modified waste mud carbon fixation environmentally friendly piles of the present invention is simple and convenient. The raw materials are scientifically proportioned, the effective ingredients are organically combined, the characteristics and synergistic effects of each component are fully exerted, the process parameters are reasonably adjusted, the optimal process parameter range is optimized, and the raw materials are more firmly combined, so that the curing agent achieves the best effect; the prefabricated hollow adaptive modified waste mud carbon fixation environmentally friendly piles have adaptive characteristics, the construction process is convenient, and the construction difficulty and time cost are reduced.

[0043] (6) The present invention improves the strength and stability of the pile body through design optimization and material utilization, so that it has better supporting capacity in soft soil layers; at the same time, the slurry fills the pores of the bulk material and diffuses into the surrounding soil to form a denser foundation structure, thereby enhancing the overall stability and bearing capacity of the composite foundation; and the carboxyl, phenolic hydroxyl and other functional groups on the surface of the biochar react chemically with the curing material to form a strong interface bond and a stable polymer network structure, which is wrapped around the surface of the biochar particles, thereby improving the durability and long-term stability of the material.

[0044] (7) The present invention can reduce the cost of waste mud disposal and the purchase of high-performance consumables through high-value-added modification and reuse of waste mud and solid waste, and has significant economic value; and the use of this method can reduce the environmental risks in the disposal of waste mud and solid waste, reduce the use of cement, and reduce carbon emissions, with outstanding social benefits.

[0045] (8) The present invention significantly improves the structural stability, bearing capacity, construction convenience and environmental adaptability of the composite foundation through the optimization of the combination of slurry filling and soil, the application of environmentally friendly and energy-saving materials, the optimization design of the pile structure, and the flexible use of bulk materials, while also fixing carbon emissions and reducing emissions, and being green and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0047] Figure 1 A flow chart of the preparation and construction method of a composite foundation of an adaptive modified waste mud carbon fixation environmentally friendly pile provided by the present invention;

[0048] Figure 2 A schematic diagram of the steps for forming an adaptive modified waste mud carbon fixation environmentally friendly pile provided by the present invention, wherein (a) is a hollow modified waste mud carbon fixation environmentally friendly pile, (b) is a hole cut in the middle, (c) is placed in the foundation and a grouting pipe is placed, (d) is a bulk material input, (e) is surrounding soft soil drainage, and (f) is grouting reinforcement pile body forming;

[0049] Figure 3 A schematic diagram of an adaptive modified waste mud carbon fixation environmental protection pile provided by the present invention, wherein (a) is a main view, (b) is a cross-sectional view of the carbon fixation environmental protection pile at AA, and (c) is a cross-sectional view of the carbon fixation environmental protection pile at BB;

[0050] Figure 4 A schematic diagram of the middle hole of an adaptive modified waste mud carbon fixation environmental protection pile provided by the present invention;

[0051] Figure 5 The unconfined compressive strength line graph of the waste mud modified with different gypsum ratios and magnesium oxide ratios of the present invention; wherein (a) is gypsum, and (b) is magnesium oxide;

[0052] Figure 6 A comparison result diagram of the pile body axial force distribution of the force and deformation of an adaptive modified waste mud carbon fixation environmentally friendly pile composite foundation and a general rigid pile composite foundation of the present invention;

[0053] Figure 7 This is a post-construction settlement comparison diagram of the stress and deformation of an adaptive modified waste mud carbon fixation environmentally friendly pile composite foundation and a general rigid pile composite foundation of the present invention. DETAILED DESCRIPTION

[0054] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0055] Example 1

[0056] like Figure 1 The present invention provides an application of an adaptive modified waste mud carbon fixation environmentally friendly pile in the reinforcement of soft soil foundation of a newly built road, comprising the following specific steps:

[0057] (1) Preparation of adaptive modified waste mud carbon fixation environmental protection piles:

[0058] (1-1) The waste mud is passed through a 10-mesh sieve to remove weeds, small stones and other debris in the mud. The moisture content of the waste mud is 100% and it is set aside. The industrial by-product gypsum, magnesium oxide, slag and biochar are dried and ground, passed through a 200-mesh sieve, and configured in a mass ratio of 70:20:5:5, and sodium chloride, an early strength agent, is added, with a mass ratio of 0.1% of the curing agent to obtain a curing agent, which is set aside. The specific surface area of ​​the slag is 400m 2 / kg, and the alkalinity is 1.0, meeting the S95 standard of GB / T18046-2017 Granulated blast furnace slag powder for cement, mortar and concrete; the particle size of magnesium oxide is 0.08mm, and the purity is 96%; the average particle size of industrial by-product gypsum is 0.08mm; the main elements of biochar include: C 68wt%, O 26wt%, and the specific surface area of ​​biochar is 450m 2 / kg, pore volume is 0.10cm 3 , pore size is 30nm;

[0059] (1-2) sending the sieved waste mud into a mixing box, adding a curing agent in portions (the mass ratio of the curing agent to the waste mud is 1:8) and stirring and mixing them thoroughly, and obtaining modified waste mud after stirring evenly at 60 rpm;

[0060] (1-3) Send the modified waste mud to 200g / m 2 The permeable geotextile is hollow in the middle and a pipe airbag is reserved. After filling, a hollow mud column is formed; the preset pipe airbag in the hollow mud column is inflated to expand outward. After it is fully expanded, the hollow mud column is fully drained and consolidated under the action of squeezing to dehydrate; the dehydrated hollow mud column is placed at 20±2℃ and a humidity of more than 90% for maintenance; after reaching the maintenance age, the pipe airbag in the hollow mud column is removed to obtain a hollow adaptive modified waste mud carbon fixation environmentally friendly pile with a diameter of 60cm, an inner diameter of 17cm, a height of 3m, and a water content of 70%;

[0061] (2) Strengthening the soft soil foundation of new roads:

[0062] (2-1) Cut the middle of the hollow adaptive modified waste mud carbon fixation environmental protection pile to form a hole. The three holes are evenly distributed around the pile, and the center interval between the upper and lower holes is 2m (such as Figure 3 and4 ),spare;

[0063] (2-2) The double-casing method is used to drill a hole in the soft soil layer. After the hole is driven into the foundation to the elevation, the inner tube is pulled out together with the soil in the inner tube without vibration;

[0064] (2-3) placing the adaptive modified waste mud carbon fixation environmentally friendly pile obtained in step (2-1) vertically into the ground according to the designed length, and inserting a grouting pipe into the center of the hollow adaptive modified waste mud carbon fixation environmentally friendly pile, and connecting it to the grouting pump through a hose;

[0065] (2-4) Fill the hollow position of the hollow adaptive modified waste mud carbon fixation environmental protection pile with bulk material to the ground height, overflowing the pile body; pull out the outer tube of the double casing, and continue to put the bulk material into the hollow adaptive modified waste mud carbon fixation environmental protection pile, so that it can overflow from the middle hole of the hollow adaptive modified waste mud carbon fixation environmental protection pile and fill around the hollow adaptive modified waste mud carbon fixation environmental protection pile; Figure 2 Schematic diagram of the steps for forming an adaptive modified waste mud carbon fixation environmentally friendly pile, wherein (a) is a hollow adaptive modified waste mud carbon fixation environmentally friendly pile, (b) is a hollow adaptive modified waste mud carbon fixation environmentally friendly pile after a hole is cut in the middle, (c) is a hollow adaptive modified waste mud carbon fixation environmentally friendly pile placed in the foundation and with a grouting pipe, (d) is a hollow adaptive modified waste mud carbon fixation environmentally friendly pile with bulk materials, (e) is a hollow adaptive modified waste mud carbon fixation environmentally friendly pile for drainage of surrounding soft soil (the arrow in the figure indicates the drainage direction), and (f) is a hollow adaptive modified waste mud carbon fixation environmentally friendly pile formed by grouting reinforcement of the pile body;

[0066] (2-5) Under the action of soil squeezing, the pore water in the soft soil around the pile is discharged along the bulk material in the middle of the hollow adaptive modified waste mud carbon fixation environmental protection pile. The pile soil is adaptive. After the surrounding soft soil layer is drained, the modified waste mud slurry is injected into the bulk material along the grouting pipe through the grouting pump. The slurry consolidates with the bulk material and penetrates into the soil around the pile through the holes between the pile sections and the bulk material overflowing from the holes. At the same time, it fills the entire internal cavity of the hollow modified waste mud carbon fixation environmental protection pile, so that the bulk material, the hollow modified waste mud carbon fixation environmental protection pile and the surrounding soft soil form a whole, thereby reinforcing the soft soil roadbed foundation.

[0067] Example 2

[0068] The present invention provides an application of an adaptive modified waste mud carbon fixation environmental protection pile in river bank slope stabilization treatment, comprising the following specific steps:

[0069] (1) Preparation of adaptive modified waste mud carbon fixation environmental protection piles:

[0070] (1-1) The waste mud is passed through a 10-mesh sieve to remove weeds, small stones and other debris in the mud. The moisture content of the waste mud is 110% and is set aside. The industrial by-product gypsum, magnesium oxide, slag and biochar are dried and ground, passed through a 200-mesh sieve, and configured in a mass ratio of 65:20:10:5, and a water-retaining agent and a water-absorbing resin are added, with a mass ratio of 0.1% of the curing agent to obtain a curing agent, which is set aside. The specific surface area of ​​the slag is 400m 2 / kg, and the alkalinity is 1.0, meeting the S95 standard of GB / T18046-2017 Granulated blast furnace slag powder for cement, mortar and concrete; the particle size of magnesium oxide is 0.08mm, and the purity is 97%; the average particle size of industrial by-product gypsum is 0.08mm; the main elements of biochar include: C 68wt%, O 26wt%, and the specific surface area of ​​biochar is 400m 2 / kg, pore volume is 0.15cm 3 , pore size is 30nm;

[0071] (1-2) sending the sieved waste mud into a mixing box, adding a curing agent in portions (the mass ratio of the curing agent to the waste mud is 1:7) and stirring and mixing them thoroughly, and obtaining modified waste mud after stirring evenly at 180 rpm;

[0072] (1-3) Send the modified waste mud to 200g / m 2 The permeable geotextile is hollow in the middle and a pipe airbag is reserved. After filling, a hollow mud column is formed; the preset pipe airbag in the hollow mud column is inflated to expand outward. After it is fully expanded, the hollow mud column is fully drained and consolidated under the action of squeezing to dehydrate; the dehydrated hollow mud column is placed at 20±2℃ and a humidity of more than 90% for maintenance; after reaching the maintenance age, the pipe airbag in the hollow mud column is removed to obtain a hollow adaptive modified waste mud carbon fixation environmental protection pile with a diameter of 50cm, an inner diameter of 15cm, a height of 2.5m, and a water content of 75%;

[0073] (2) Stabilization of river bank damage:

[0074] (2-1) Cut the middle of the hollow adaptive modified waste mud carbon fixation environmental protection pile to form a hole. The three holes are evenly distributed around the pile, and the center interval of the upper and lower holes is 1m, which are reserved;

[0075] (2-2) The double-casing method is used to drill a hole in the soft soil layer. After the hole is driven into the foundation to the elevation, the inner tube is pulled out together with the soil in the inner tube without vibration;

[0076] (2-3) placing the adaptive modified waste mud carbon fixation environmentally friendly pile obtained in step (2-1) vertically into the ground according to the designed length, and inserting a grouting pipe into the center of the hollow adaptive modified waste mud carbon fixation environmentally friendly pile, and connecting it to the grouting pump through a hose;

[0077] (2-4) Fill the hollow position of the hollow adaptive modified waste mud carbon fixation environmental protection pile with bulk material to the ground height, overflowing the pile body; pull out the outer tube of the double casing, and continue to put the bulk material into the hollow adaptive modified waste mud carbon fixation environmental protection pile, so that it can overflow from the middle hole of the hollow adaptive modified waste mud carbon fixation environmental protection pile and fill the surrounding area of ​​the hollow adaptive modified waste mud carbon fixation environmental protection pile;

[0078] (2-5) Under the action of soil squeezing, the pore water in the soft soil around the pile is discharged along the bulk material in the middle of the hollow adaptive modified waste mud carbon fixation environmental protection pile. The pile soil is adaptive. After the surrounding soft soil layer is drained, the modified waste mud slurry is injected into the bulk material along the grouting pipe through the grouting pump. The slurry consolidates with the bulk material and penetrates into the soil around the pile through the holes between the pile sections and the bulk material overflowing from the holes. At the same time, it fills the entire internal cavity of the hollow modified waste mud carbon fixation environmental protection pile, so that the bulk material, the hollow modified waste mud carbon fixation environmental protection pile and the surrounding soft soil form a whole, thereby reinforcing the river bank slope.

[0079] Effect of environmental protection modification of waste mud:

[0080] like Figure 5 As shown, it is the unconfined compressive strength of waste mud modified with different gypsum ratios and magnesium oxide ratios. The test block size is a cylinder with a diameter of 5 cm and a height of 10 cm. According to the relevant data, it can be seen that under the same other conditions, it has better strength effect than 30% cement, and under the appropriate ratio, it has better strength effect than 40% cement. Therefore, compared with traditional solidification technology methods, this technology has outstanding technical advantages, can effectively replace cement, and reduce the use of high-carbon emission materials. At the same time, the use of biochar that absorbs carbon dioxide and a large amount of solid waste to modify the waste mud has significant carbon fixation and emission reduction benefits, and the deep modified mud column itself has sufficient strength;

[0081] The implementation effect of adaptive modified waste mud carbon fixation environmental protection pile composite foundation:

[0082] The working principle of the adaptive modified waste mud carbon fixation environmentally friendly pile composite foundation of the present invention is to utilize the strong water permeability of the bulk material inside and around the pile body to accelerate the drainage and consolidation of the soil between the piles in the early stage, and to form a rigid pile with strong bearing capacity and good settlement control effect through grouting and bonding in the later stage; compared with the rigid composite foundation obtained by the commonly used rigid pile treatment method (usually a rigid composite foundation refers to a foundation treatment method in which rigid piles are arranged in a soft foundation to jointly bear the load of the upper structure with the soil between the piles, and common rigid piles include precast concrete piles, cast-in-place piles, steel pipe piles, etc.), the adaptive modified waste mud carbon fixation environmentally friendly pile composite foundation of the present invention can greatly reduce post-construction settlement and effectively improve the bearing capacity of the soft soil foundation while taking into account the drainage capacity and vertical stiffness. The specific results are as follows Figure 6 and 7 As shown, carbon fixation and environmental protection piles and general precast concrete piles prepared by the formula and method of Example 1 are used. It can be seen from the figure that the working principle of the adaptive modified waste mud carbon fixation and environmental protection piles adopted by the present invention is to utilize the strong permeability of the bulk material inside and around the pile body to accelerate the drainage and consolidation of the soil between the piles in the early stage, and to form a rigid pile with strong bearing capacity and good settlement control effect through grouting and bonding in the later stage. This technology has significant advantages.

[0083] The various embodiments are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to in detail.

[0084] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing an adaptive modified waste mud carbon fixation environmental protection pile, characterized in that: The specific steps include: (1) Screen the waste mud to remove impurities and set aside; (2) Adding a curing agent to the waste mud obtained in step (1) and mixing them evenly to obtain modified waste mud, wherein the curing agent comprises the following raw materials in percentage by weight: 60-80% slag, 20-30% alkali activator, 5-15% industrial by-product gypsum, 5-10% biochar and 0-0.5% composite admixture; the water content of the waste mud is 90-120%; the specific surface area of ​​the slag is 400-800m 2 / kg, and the alkalinity is greater than or equal to 1.0; the particle size of the alkaline activator is less than 0.08mm, and the purity is more than 96%; the average particle size of the industrial by-product gypsum is less than 0.08mm; the main elements of the biochar include: C46-79wt%, O 5-38wt%; the specific surface area of ​​the biochar is 300-550m 2 / kg, pore volume is 0.01-0.3cm 3 , the pore size is 1-35nm; the composite admixture is at least one of an accelerator, an early strength agent, a retarder and an antifreeze agent; (3) Adding the modified waste mud into a mold, draining, consolidating and curing the mold to obtain an adaptive modified waste mud carbon fixation environmentally friendly pile.

2. The method for preparing an adaptive modified waste mud carbon fixation environmental protection pile according to claim 1, characterized in that: The mass ratio of the curing agent to the waste mud in step (2) is 1:7-8; The stirring speed of the mixing is 60-180 rpm.

3. The method for preparing an adaptive modified waste mud carbon fixation environmental protection pile according to claim 1, characterized in that: The mold in step (3) is a permeable geotextile made of polypropylene yarn by sewing, and its structure is a hollow cylinder after being filled with the modified waste mud; The drainage consolidation adopts pipeline airbag expansion. When the pipeline airbag is fully expanded, the outer diameter is 18-25cm, the length is 1.5-3.5m, and the maximum pressure is 0.05MPa; The curing temperature is 20±2°C and the humidity is above 90%.

4. The method for preparing an adaptive modified waste mud carbon fixation environmental protection pile according to claim 1, characterized in that: The self-adaptive modified waste mud carbon fixation environmentally friendly pile described in step (3) has an inner diameter of 14-20 cm, an outer diameter of 50-60 cm, and a water content of 60-80%.

5. An adaptive modified waste mud carbon fixation environmental protection pile obtained by the preparation method as described in any one of claims 1-4.

6. Application of the adaptive modified waste mud carbon fixation environmentally friendly pile as described in claim 5 in strengthening the foundation.

7. The use according to claim 6, characterized in that: The pile body in the reinforced foundation adopts the adaptive modified waste mud carbon fixation environmental protection pile, and the core material is slurry reinforced bulk material; The slurry is modified waste mud, and the bulk material is sand and gravel excavated during the foundation drilling process or other solid waste that is difficult to reuse.

8. The use according to claim 6, characterized in that: The adaptive modified waste mud carbon fixation environmental protection pile is cut in the reinforced foundation to form holes, and the holes are evenly distributed around the piles, and the upper and lower centers of the holes are spaced 1-3m apart.

9. The use according to claim 6, characterized in that: The specific construction method of the reinforced foundation is: 1) Cutting the adaptive modified waste mud carbon fixation environmental protection pile to form holes for standby use; 2) Use the double casing method to drill a hole in the soil layer, drive it into the foundation to the elevation, and then pull out the inner tube together with the soil in the inner tube without vibration; 3) The adaptive modified waste mud carbon fixation environmental protection pile obtained in step 1) is placed vertically on the ground according to the designed length, and a grouting pipe is inserted into the center of the adaptive modified waste mud carbon fixation environmental protection pile, which is connected to a grouting pump through a hose; then, the hollow position of the adaptive modified waste mud carbon fixation environmental protection pile is filled with bulk material to the ground height, which can overflow the pile body; 4) Pull out the outer tube of the double-casing tube, and continue to put the bulk material into the adaptive modified waste mud carbon fixation environmental protection pile, so that it can overflow from the hole and fill around the adaptive modified waste mud carbon fixation environmental protection pile; 5) Under the action of soil squeezing, the pore water in the soil layer around the pile is discharged along the bulk material in the middle of the adaptive modified waste mud carbon fixation environmentally friendly pile, and the pile and soil are adaptive. After the drainage in the surrounding soil layer is completed, the grouting pump is used to inject slurry into the bulk material along the grouting pipe. The slurry and the bulk material are consolidated and penetrate into the soil around the pile through the holes and the bulk material overflowing from the holes, and at the same time fill the entire internal cavity of the adaptive modified waste mud carbon fixation environmentally friendly pile, so that the bulk material, the adaptive modified waste mud carbon fixation environmentally friendly pile and the surrounding soil layer form a whole.

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