Compacted restrained cement soil column for resource utilization of construction waste and its construction method

Abstract

The present invention discloses a compacted constrained cement soil column for resource utilization of engineering slag and a construction method thereof. The cement soil column comprises cement soil, and a steel pipe or a fiber reinforced composite material (FRP) pipe. The present invention combines cement soil with a steel pipe or a fiber reinforced composite material (FRP) pipe, wherein the steel pipe or the FRP pipe provides an outer lateral constraint for the cement soil, and a compacted constrained cement soil column component is formed by compacting the cement soil in the pipe, which greatly improves the pressure mechanical properties of engineering slag and opens up a new path for efficient resource utilization of engineering slag.

Description

Technical Field

[0001] The invention relates to the technical field of recycling of engineering waste, and in particular to a compacted constrained cement soil column for resource utilization of engineering slag and a construction method thereof. Background Art

[0002] In recent years, with the rapid development of urbanization in my country, my country has generated more than 3.5 billion tons of construction waste each year, which has caused great harm to the environment. Among them, construction waste accounts for more than 70% of the total construction waste. Construction waste is mainly abandoned soil generated in underground projects or foundation projects. At present, the resource utilization rate of construction waste in China is less than 5%, while at the same time, the resource utilization rate of construction waste in developed countries has reached more than 90%. The main methods of disposal of construction waste in my country include low-lying land landfill, foundation backfill, mine backfill, and land reclamation. For cities with large construction scales, large-scale construction waste discharge relies heavily on off-site disposal. With the increasing requirements for ecological and environmental protection, the traditional extensive construction waste disposal method can no longer adapt to the sustainable development of Chinese cities. How to promote the recycling of construction waste resources has become a new issue that tests the ability and level of urban governance in the period of rapid development of modern cities.

[0003] Steel or fiber reinforced plastics (FRP) have been widely used as restraint or structural materials in civil engineering due to their excellent properties of light weight and high strength. At present, in actual engineering, steel tube concrete structures and fiber reinforced plastic (FRP) restrained concrete structures are widely used. Restraining concrete can improve its bearing capacity and ductility. In recent years, this type of new composite structure has become a hot application and research direction.

[0004] Cement soil is a material made by mixing soil, cement, water and other components in appropriate proportions, stirring and hardening. Cement soil is a mixed engineering material with mechanical properties between soil and concrete. Cement soil can be used as a base material under asphalt concrete and cement concrete pavement, as well as engineering materials such as slope reinforcement of dams and embankments, lining of trenches-reservoirs-shallow lakes, large-volume cement soil embankment, foundation stabilization, pavement base, slope reinforcement, and anti-seepage lining. The outstanding advantages of cement soil are that it can be made from local materials, reduces transportation, is easy to construct, and is low in price. The large-scale promotion and application of cement soil technology can achieve significant economic benefits.

[0005] Traditional steel pipe or FRP pipe confined concrete columns require a large amount of resources such as sand, gravel and cement. The carbon dioxide emitted by the manufacture of cement, a building material, accounts for 7% of global carbon dioxide emissions. China accounts for nearly half of the world's cement production and carbon emissions in cement production, which has put tremendous pressure on my country to achieve its "dual carbon" goals. The mechanical properties of traditional cement soil that has not been compacted and has no lateral constraints are poor. The unconfined compressive strength is only 0.3-2.0MPa, and it depends greatly on the amount of cement, which has caused great restrictions and constraints on the application of cement soil (Wang Zihan, Research on the horizontal bearing characteristics of large-diameter cement soil composite steel pipe piles, [D], Southeast University, 2021.). Therefore, a new method is needed to solve the problems of significantly low compressive strength of cement soil and relatively high cement dosage in existing projects. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings and deficiencies of the above-mentioned prior art and to provide a compacted constrained cement soil column for efficient resource utilization of engineering waste and a construction method thereof.

[0007] The present invention combines cement soil with steel pipes or fiber reinforced plastic (FRP) pipes. The steel pipes or FRP pipes provide lateral constraints for the cement soil. By compacting the cement soil in the pipes, a compacted constrained cement soil column component is formed, which greatly improves the pressure-bearing mechanical properties of engineering slag and opens up a new path for the efficient resource utilization of engineering slag.

[0008] In order to achieve the purpose of the present invention, the present invention adopts the following technical scheme.

[0009] The present invention provides a compacted constrained cement soil column for resource utilization of engineering slag, comprising cement soil, and a steel pipe or a fiber reinforced composite material (FRP) pipe. The cement soil comprises the following raw materials by weight:

[0010] 100-140 parts of construction waste soil after deducting the water content;

[0011] Cement 0-15 parts;

[0012] Water (including the water content of construction waste soil) 0-25 parts;

[0013] The cement soil is located inside the steel pipe or FRP pipe, and a compacted restrained cement soil column component is formed by compacting the cement soil in the pipe.

[0014] Furthermore, the engineering slag is waste soil generated in underground engineering or foundation engineering.

[0015] Furthermore, the cross-sectional shape of the steel pipe or FRP pipe is circular, rectangular or other polygonal.

[0016] Furthermore, the cement soil may be mixed with or not mixed with one or more of the following fibers: chopped steel fiber, basalt fiber, carbon fiber, glass fiber, synthetic fiber, etc. When the above fibers are mixed, the mixing amount is 0.55-50 kg / m 3 .

[0017] Furthermore, the cement soil column also includes high-strength cement mortar with a compressive strength ranging from 30MPa to 100MPa, located in the gap between the upper surface of the cement soil and the upper end opening of the steel pipe or FRP pipe, with a thickness of 0 to 10mm.

[0018] Furthermore, the compaction treatment is to use a pressure device to apply vertical pressure to the cement soil in the pipe to compact the cement soil, wherein the pressure head diameter of the pressure device is 5 to 10 mm smaller than the inner diameter of the steel pipe or FRP pipe.

[0019] The present invention provides a construction method of a compacted pipe-constrained cement soil column for resource utilization of engineering slag, comprising the following steps:

[0020] (1) putting construction waste soil, cement and water according to their weight proportions into a mixer and mixing them thoroughly to obtain cement soil;

[0021] (2) Fill cement soil into the steel pipe or FRP pipe until the cement soil is flush with the upper end opening of the steel pipe or FRP pipe;

[0022] (3) Use pressure equipment to apply vertical pressure to the cement soil in the pipe to compact the cement soil;

[0023] (4) After the cement soil in the pipe is compacted, the height is lowered, and the cement soil filling and compacting operations of the above steps (2) and (3) are repeated until the distance between the upper surface of the compacted cement soil and the upper end opening of the steel pipe or FRP pipe does not exceed 10 mm.

[0024] (5) Finally, high-strength cement mortar is used for sealing and leveling.

[0025] Furthermore, the pressure range of the vertical pressure applied in step (3) is 20MPa to 45MPa.

[0026] Furthermore, in step (3), during the process of applying vertical pressure to the cement soil in the pipe using pressure equipment, the lateral strain of the steel pipe is less than the yield strain of the steel, and the lateral strain of the FRP pipe does not exceed 80% of the ultimate strain of the FRP.

[0027] Compared with the existing technology, the present invention has the following advantages and beneficial effects:

[0028] (1) In the present invention, the main material is engineering waste soil, which has a large output and is difficult to dispose of. Compared with the traditional method of treating engineering waste soil, the resource utilization rate of engineering waste soil is greatly improved, the application field of engineering waste soil is broadened, and a new idea is provided for the resource utilization of engineering waste soil, which can generate significant economic and social benefits.

[0029] (2) Compared with traditional FRP-confined concrete or steel tube concrete, the present invention uses compacted cement soil to directly replace concrete, which greatly reduces the consumption of resources such as sand, stone, and cement, can alleviate the shortage of natural sand and stone and the pressure on the environment caused by cement production, and is highly consistent with the concept of green development.

[0030] (3) The present invention adopts a combination of steel pipe or FRP pipe and cement soil. The steel pipe or FRP pipe provides effective lateral restraint for the cement soil, so that the compaction of the cement soil can be achieved. Compared with the uncompacted cement soil, its pressure mechanical properties are greatly improved, so that the application range of the cement soil is greatly expanded. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the overall structure of a compacted confined cement soil column;

[0032] Figure 2 is a schematic diagram of the transverse section of a compacted confined cement soil column;

[0033] Figure 3 is a schematic diagram of the longitudinal section of a compacted confined cement soil column;

[0034] Among them: 1-compacted cement soil; 2-steel pipe or FRP pipe; 3-high-strength cement mortar. DETAILED DESCRIPTION

[0035] The implementation of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but the implementation of the present invention is not limited thereto. It should be noted that if there are processes or parameters that are not particularly described in detail below, they can be understood or implemented by those skilled in the art with reference to the prior art.

[0036] The construction waste soil used in the embodiments of the present invention is all weathered granite soil taken from the foundation pit of the second phase project of Luogang Station of Guangzhou Metro Line 7. Weathered granite soil is a very common construction waste soil in the engineering construction process in Guangdong.

[0037] Example 1

[0038] This embodiment prepares a compacted constrained cement soil column. The overall structure of the compacted constrained cement soil column is as follows: Figure 1 (left) shows the cross-sectional view. Figure 2 (left) shows the longitudinal cross-sectional view. Figure 3As shown in the figure, 1-compacted cement soil; 2-steel pipe or FRP pipe; 3-high-strength cement mortar.

[0039] The cement soil described in this embodiment includes the following raw materials by weight:

[0040] 100 parts of construction waste soil after deducting the water content;

[0041] 15 parts of cement;

[0042] Water (including the water contained in construction waste soil) 25 parts;

[0043] In this embodiment, the cement soil outer pipe constraint adopts Q235 round seamless steel pipe with an outer diameter of 325mm, a wall thickness of 6mm and a height of 900mm.

[0044] The pressure equipment used for compaction processing in this embodiment is a reaction frame and a jack, wherein the diameter of the pressure head is 5 mm smaller than the inner diameter of the steel pipe.

[0045] The specific construction method of this embodiment includes the following steps:

[0046] (1) 110 kg of construction waste soil after deducting the water content, 16.5 kg of cement, 27.5 kg of water (including the water content of the construction waste soil), and 3.3 kg of chopped steel fibers were put into a mixer and stirred thoroughly to obtain cement soil;

[0047] (2) Fill the steel pipe with cement soil until the cement soil is flush with the upper opening of the steel pipe;

[0048] (3) Use a reaction frame and a jack to apply vertical pressure to the cement soil in the pipe, and the applied pressure is 30 MPa;

[0049] (4) After compaction, the height of the cement soil in the pipe decreases, and the filling and compaction operations of the cement soil in steps (2) and (3) are repeated. After the last compaction, the distance between the upper surface of the compacted cement soil and the upper end opening of the steel pipe is 5 mm;

[0050] (5) Finally, high-strength cement mortar with a compressive strength of 40 MPa is used for sealing and leveling.

[0051] When the reaction frame and jack are used to apply vertical pressure to the cement soil in the pipe, the maximum lateral strain of the steel pipe is 70% of the yield strain of Q235 steel.

[0052] When the compacted restrained cement soil column produced in this embodiment reaches 28 days old, the compressive bearing capacity is tested, and it is measured that the compressive bearing capacity can reach more than 2800 kN, which greatly improves its pressure bearing mechanical performance compared with the cement soil that has not been compacted and has no lateral restraint.

[0053] Example 2

[0054] This embodiment prepares a compacted constrained cement soil column. The overall structure of the compacted constrained cement soil column is as follows: Figure 1 (left) shows the cross-sectional view. Figure 2 (left) shows the longitudinal cross-sectional view. Figure 3 As shown in the figure, 1-compacted cement soil; 2-steel pipe or FRP pipe; 3-high-strength cement mortar.

[0055] The cement soil described in this embodiment includes the following raw materials by weight:

[0056] 130 parts of construction waste soil after deducting the water content;

[0057] 4 parts of cement;

[0058] Water (including the water content of construction waste soil) 6 parts;

[0059] In this embodiment, the cement soil outer pipe is constrained by a circular glass fiber tube (this glass fiber tube is one of the FRP tubes), the outer diameter of the glass fiber tube is 350 mm, the wall thickness is 6 mm, and the height is 900 mm.

[0060] The pressure equipment used for compaction in this embodiment is a reaction frame and a jack, wherein the diameter of the pressure head is 7 mm smaller than the inner diameter of the glass fiber tube.

[0061] The specific construction method of this embodiment includes the following steps:

[0062] (1) 162.5 kg of construction waste soil after deducting the water content, 5 kg of cement, and 7.5 kg of water (including the water content of the construction waste soil) were put into a mixer and stirred thoroughly to obtain cement soil (in this example, no fiber was added);

[0063] (2) Fill cement soil into the fiberglass tube until the cement soil is flush with the upper end opening of the fiberglass tube;

[0064] (3) Use a reaction frame and a jack to apply vertical pressure to the cement soil in the pipe, and the applied pressure is 25 MPa;

[0065] (4) After compaction, the height of the cement soil in the pipe decreases, and the filling and compaction operations of the cement soil in steps (2) and (3) are repeated. After the last compaction, the distance between the upper surface of the compacted cement soil and the upper end opening of the fiberglass pipe is 10 mm.

[0066] (5) Finally, high-strength cement mortar with a compressive strength of 30 MPa is used for sealing and leveling.

[0067] When the reaction frame and the jack are used to apply vertical pressure to the cement soil in the pipe, the maximum lateral strain of the fiberglass pipe is 50% of the ultimate strain of the pipe.

[0068] When the compacted constrained cement soil column produced in this embodiment reaches 28 days old, a compressive bearing capacity test is performed, and it is measured that the compressive bearing capacity can reach more than 2500 kN, which greatly improves its pressure bearing mechanical performance compared with uncompacted and non-laterally constrained cement soil.

[0069] Example 3

[0070] This embodiment prepares a compacted constrained cement soil column. The overall structure of the compacted constrained cement soil column is as follows: Figure 1 (right) shows the cross-sectional view. Figure 2 (right) shows the longitudinal cross-sectional view. Figure 3 As shown in the figure, 1-compacted cement soil; 2-steel pipe or FRP pipe 3-high-strength cement mortar.

[0071] The cement soil described in this embodiment includes the following raw materials by weight:

[0072] 120 parts of construction waste soil after deducting the water content;

[0073] 5 parts of cement;

[0074] Water (including the water contained in construction waste soil) 15 parts;

[0075] In this embodiment, the cement soil outer tube is constrained by a square carbon fiber tube (this carbon fiber tube is one of the FRP tubes), the outer side length of the carbon fiber tube is 300 mm, the tube wall thickness is 5 mm, and the height is 900 mm.

[0076] The pressure equipment used for compaction in this embodiment is a reaction frame and a jack, wherein the side length of the square pressure head is 6 mm smaller than the inner side length of the carbon fiber tube.

[0077] The specific construction method of this embodiment includes the following steps:

[0078] (1) 132 kg of construction waste soil after deducting the water content, 5.5 kg of cement, and 16.5 kg of water (including the water content of the construction waste soil) were put into a mixer and stirred thoroughly to obtain cement soil (in this example, no fiber was added);

[0079] (2) Fill cement soil into the carbon fiber tube until the cement soil is flush with the upper end opening of the carbon fiber tube;

[0080] (3) Use a reaction frame and a jack to apply vertical pressure to the cement soil in the pipe, and the applied pressure is 40 MPa;

[0081] (4) After compaction, the height of the cement soil in the tube decreases, and the filling and compaction operations of the cement soil in steps (2) and (3) are repeated. After the last compaction is completed, the distance between the upper surface of the compacted cement soil and the upper end opening of the carbon fiber tube is 8 mm;

[0082] (5) Finally, high-strength cement mortar with a compressive strength of 55 MPa is used for sealing and leveling.

[0083] When the reaction frame and the jack are used to apply vertical pressure to the cement soil in the tube, the maximum lateral strain of the carbon fiber tube is 60% of the ultimate strain of the tube.

[0084] When the compacted restrained cement soil column produced in this embodiment reaches 28 days old, a compressive bearing capacity test is performed, and it is measured that the compressive bearing capacity can reach more than 4000 kN, which greatly improves its pressure bearing mechanical performance compared with uncompacted and non-laterally restrained cement soil.

[0085] Example 4

[0086] This embodiment prepares a compacted constrained cement soil column. The overall structure of the compacted constrained cement soil column is as follows: Figure 1 (right) shows the cross-sectional view. Figure 2 (right) shows the longitudinal cross-sectional view. Figure 3 As shown in the figure, 1-compacted cement soil; 2-steel pipe or FRP pipe; 3-high-strength cement mortar.

[0087] The cement soil described in this embodiment includes the following raw materials by weight:

[0088] 120 parts of construction waste soil after deducting the water content;

[0089] 8 parts of cement;

[0090] Water (including the water contained in construction waste soil) 12 parts;

[0091] In this embodiment, the outer tube constraint of the cement soil column is Q345B square seamless steel pipe, the outer side length of the steel pipe is 300mm, the wall thickness of the steel pipe is 8mm, and the height is 900mm.

[0092] The pressure equipment used for compaction processing in this embodiment is a reaction frame and a jack, wherein the side length of the square pressure head is 8 mm smaller than the inner side length of the steel pipe.

[0093] The specific construction method of this embodiment includes the following steps:

[0094] (1) 132 kg of construction waste soil after deducting the water content, 8.8 kg of cement, 13.2 kg of water (including the water content of the construction waste soil), and 0.33 kg of glass fiber were put into a mixer and stirred thoroughly to obtain cement soil;

[0095] (2) Fill the steel pipe with cement soil until the cement soil is flush with the upper opening of the steel pipe;

[0096] (3) Use a reaction frame and a jack to apply vertical pressure to the cement soil in the pipe, and the applied pressure is 45 MPa;

[0097] (4) After compaction, the height of the cement soil in the pipe decreases, and the filling and compaction operations of the cement soil in steps (2) and (3) are repeated. After the last compaction, the distance between the upper surface of the compacted cement soil and the upper end opening of the steel pipe is 7 mm;

[0098] (5) Finally, high-strength cement mortar with a compressive strength of 60 MPa is used for sealing and leveling.

[0099] When the reaction frame and jack are used to apply vertical pressure to the cement soil in the pipe, the maximum lateral strain of the steel pipe is 85% of the yield strain of the steel.

[0100] When the compacted constrained cement soil column produced in this embodiment reaches 28 days old, a compressive bearing capacity test is performed, and it is measured that the compressive bearing capacity can reach more than 4500 kN, which greatly improves its pressure bearing mechanical performance compared with uncompacted and non-laterally constrained cement soil.

[0101] The implementation methods of the present invention are not limited to the above-mentioned embodiments, and any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention shall be equivalent replacement methods and shall be included in the protection scope of the present invention.

Claims

1. A compacted constrained cement soil column for resource utilization of engineering slag, characterized in that: It includes cement soil, and steel pipe or FRP pipe; the cement soil includes the following raw materials by weight: 100-140 parts of construction waste soil after deducting the water content; Cement 0-15 parts; 0-25 parts of water; The water includes the water contained in the engineering slag; the cement soil is located inside the steel pipe or FRP pipe, and the cement soil in the pipe is compacted: the pressure range of applying vertical pressure is 20MPa~45Mpa, and in the process of applying vertical pressure to the cement soil in the pipe using pressure equipment, the lateral strain of the steel pipe is less than the yield strain of the steel, and the lateral strain of the FRP pipe does not exceed 80% of the ultimate strain of the FRP, thereby forming a compacted constrained cement soil column component; the cement soil column also includes high-strength cement mortar, whose compressive strength ranges from 30MPa to 100MPa, located in the gap between the upper surface of the cement soil and the upper end opening of the steel pipe or FRP pipe, and the thickness is 0~10mm; The preparation of the compacted constrained cement soil column for resource utilization of engineering slag comprises the following steps: (1) putting construction waste soil, cement and water according to their weight proportions into a mixer and mixing them thoroughly to obtain cement soil; (2) Fill cement soil into the steel pipe or FRP pipe until the cement soil is flush with the upper end opening of the steel pipe or FRP pipe; (3) using a pressure device to apply vertical pressure to the cement soil in the pipe to compact the cement soil; the pressure range of the applied vertical pressure is 20 MPa to 45 MPa; (4) After compaction, the height of the cement soil in the pipe decreases, and the filling and compacting operations of the cement soil in steps (2) and (3) are repeated until the distance between the upper surface of the compacted cement soil and the upper end opening of the steel pipe or FRP pipe does not exceed 10 mm; Finally, high-strength cement mortar is used for sealing and leveling.

2. The compacted constrained cement soil column for resource utilization of construction waste according to claim 1 is characterized in that: The engineering slag is the abandoned soil generated in underground engineering or foundation engineering.

3. The compacted constrained cement soil column for resource utilization of construction waste according to claim 1 is characterized in that: The cross-sectional shape of the steel pipe or FRP pipe is circular, rectangular or other polygonal.

4. The compacted constrained cement soil column for resource utilization of construction waste according to claim 1 is characterized in that: The cement soil is mixed with short-cut steel fiber, basalt fiber, carbon fiber, glass fiber, or synthetic fiber, and the fiber mixing amount is 0.55-50 kg / m 3 .

5. The compacted constrained cement soil column for resource utilization of construction waste according to claim 1 is characterized in that: The cement soil does not contain chopped steel fibers, basalt fibers, carbon fibers, glass fibers, or synthetic fibers.

6. The compacted constrained cement soil column for resource utilization of construction waste according to claim 1 is characterized in that: The compaction treatment is to use a pressure device to apply vertical pressure to the cement soil in the pipe to compact the cement soil, wherein the pressure head diameter of the pressure device is 5 to 10 mm smaller than the inner diameter of the steel pipe or FRP pipe.

7. A construction method of compacted constrained cement soil column for resource utilization of engineering waste, characterized in that: The compacted constrained cement soil column comprises cement soil and a steel pipe or an FRP pipe; the cement soil comprises the following raw materials in terms of mass fraction: 100-140 parts of construction waste soil after deducting the water content; Cement 0-15 parts; 0-25 parts of water; The water includes the water contained in the engineering slag; the cement soil is located inside the steel pipe or FRP pipe, and the cement soil in the pipe is compacted: the pressure range of applying vertical pressure is 20MPa~45Mpa, and in the process of applying vertical pressure to the cement soil in the pipe using pressure equipment, the lateral strain of the steel pipe is less than the yield strain of the steel, and the lateral strain of the FRP pipe does not exceed 80% of the ultimate strain of the FRP, thereby forming a compacted constrained cement soil column component; the cement soil column also includes high-strength cement mortar, whose compressive strength ranges from 30MPa to 100MPa, located in the gap between the upper surface of the cement soil and the upper end opening of the steel pipe or FRP pipe, and the thickness is 0~10mm; The preparation of the compacted constrained cement soil column for resource utilization of engineering slag comprises the following steps: (1) putting construction waste soil, cement and water according to their weight proportions into a mixer and mixing them thoroughly to obtain cement soil; (2) Fill cement soil into the steel pipe or FRP pipe until the cement soil is flush with the upper end opening of the steel pipe or FRP pipe; (3) using a pressure device to apply vertical pressure to the cement soil in the pipe to compact the cement soil; the pressure range of the applied vertical pressure is 20 MPa to 45 MPa; (4) After compaction, the height of the cement soil in the pipe decreases, and the filling and compacting operations of the cement soil in steps (2) and (3) are repeated until the distance between the upper surface of the compacted cement soil and the upper end opening of the steel pipe or FRP pipe does not exceed 10 mm; Finally, high-strength cement mortar is used for sealing and leveling.

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