A reinforced column for confined and solidified sulfate soil suitable for lateral load-bearing

Abstract

This invention discloses a constrained and solidified sulfate-alkali soil reinforced column suitable for lateral load-bearing, belonging to the field of transportation engineering. Specifically, for sulfate-alkali soil with a salt content of 1-50%, a corrosion-resistant pipe with good mechanical properties is used as the constraining pipe, and a corrosion-resistant reinforcing material with good mechanical properties is used as the vertical reinforcement, which is uniformly arranged inside the constraining pipe and closely attached to the inner wall of the pipe, with a reinforcement ratio of 0.6-4.2%. The curing agent consists of an expansion component and a cementing component. A material that hydrates rapidly and forms an expanding hydrate with sulfate ions is used as the expansion component, and a material with a slow hydration rate is used as the cementing component. The underground burial depth and above-ground height of the constrained and solidified sulfate-alkali soil reinforced column are designed according to the requirements. Saline soil is used as the column preparation material, and the soil moisture content and the water-cement ratio of the curing agent are controlled. The curing agent is mixed with the sulfate-alkali soil at a fixed water-cement ratio, uniformly filled into the constraining pipe, and compacted to form a constrained and solidified sulfate-alkali soil reinforced column with high strength and good lateral load-bearing performance.

Description

Technical Field

[0001] This invention relates to a reinforced column in constrained and solidified sulfate soil suitable for lateral load-bearing, belonging to the field of traffic engineering. Background Technology

[0002] my country has a large area of ​​sulfate-rich soil, with salt content reaching up to 50%. The construction of transportation infrastructure such as airports, roads, and industrial buildings in this region requires numerous column structures with good lateral load-bearing capacity. However, the widely used reinforced concrete column structures often suffer severe corrosion from sulfate ions, especially high-sulfate content, leading to premature failure and inability to meet long-term service requirements. This poses a significant challenge to transportation infrastructure construction in the region. Furthermore, the large carbon emissions generated during the production of silicate cements hinder my country's timely achievement of its carbon emission targets. Therefore, developing a low-carbon column structure with good lateral load-bearing capacity that can serve for a long time in high-sulfate environments has significant economic and social value.

[0003] Constrained solidification technology, which organically combines a solidifying agent containing an expansive component with the constrained body, enables the resource utilization of soil and possesses good vertical bearing capacity, as detailed in patents "Construction Method of Solidified Soil Piles" (ZL201610183422.6) and "Treatment Method of Contaminated Soil" (201610184702.9). However, constrained solidification technology uses ordinary silicate cement as the solidifying agent, and the corrosive effect of sulfate ions on silicate cement makes it unsuitable for sulfate-containing soils, especially those with high sulfate content. Furthermore, the insufficient ability to withstand horizontal loads limits the application scope of constrained solidification technology, and the use of ordinary silicate cement as the solidifying agent generates significant carbon emissions.

[0004] Based on this, the present invention proposes a reinforced column for constrained solidified sulfate soil suitable for lateral load-bearing. Summary of the Invention

[0005] This invention proposes a reinforced column for constrained solidification of sulfate-contaminated soil that utilizes sulfate resources. It aims to solve the problems of insufficient ability of constrained solidification technology to resist horizontal loads and insufficient durability in sulfate-contaminated soil environments. It provides a new type of column that is low-carbon, economical, and has good horizontal bearing capacity for sulfate-contaminated soil areas, and realizes the resource utilization of sulfate.

[0006] This invention proposes a reinforced column for confined and solidified sulfate-alkali soil suitable for lateral load-bearing. Specifically, for sulfate-alkali soil with a salt content of 1-50%, a corrosion-resistant pipe with good mechanical properties is used as the confining pipe, and corrosion-resistant steel bars with good mechanical properties are used as vertical reinforcements, uniformly arranged inside the confining pipe and tightly attached to the inner wall of the pipe, with a reinforcement ratio ranging from 0.6-4.2%. The curing agent consists of an expansion component and a cementing component. A material that hydrates rapidly and forms an expanding hydrate with sulfate ions is used as the expansion component, and a material with a slow hydration rate is used as the cementing component. The mass ratio of the component and the cementing component is 15~70:30~85. The underground burial depth and above-ground height of the constrained and solidified sulfate-reinforced column are designed according to requirements. Sulfate-reinforced soil is used as the column preparation material. The moisture content of the sulfate-reinforced soil and the water-cement ratio of the curing agent are controlled. The curing agent is mixed evenly with the sulfate-reinforced soil at a fixed water-cement ratio near the optimum moisture content, filled into the constrained tube, and compacted to form the constrained and solidified sulfate-reinforced column. The constrained and solidified sulfate-reinforced column has high strength, good horizontal bearing capacity, and durability, while also realizing the resource utilization of sulfate.

[0007] The constraint tube of the present invention includes, but is not limited to, rigid materials and flexible materials, as well as combinations of the two types of materials; the reinforcing material includes, but is not limited to, steel reinforcement, bamboo reinforcement, FRP reinforcement, and combinations of different types of reinforcing materials.

[0008] When the constraint tube described in this invention is made of rigid material or a combination of rigid and flexible materials, it is optional to provide circumferential structural ribs inside the constraint tube. When the constraint tube is made of flexible material, circumferential structural ribs must be provided inside the constraint tube. When the constraint tube and ribs have insufficient durability in a sulfate environment, the constraint tube and ribs need to be treated with anti-corrosion measures. The anti-corrosion measures include, but are not limited to, forming an anti-corrosion layer by using epoxy resin, chlorinated polyolefin, polyurethane resin, fluorocarbon resin coating, acrylic resin, polyurea waterproof and anti-corrosion coating, anti-corrosion structural adhesive, etc.

[0009] The expansion component of this invention is a rapidly hydrating material. The expansion component rapidly hydrates with sulfate ions in the soil to generate an expansion hydrate. The expansion hydrate generated by the hydration of the expansion component includes, but is not limited to, hydrated calcium sulfoaluminate. The expansion component includes, but is not limited to, a mixture composed of aluminate cement, quicklime, and gypsum in a mass ratio ranging from 9 to 12:16 to 23:0 to 30.

[0010] The cementing component of this invention is a material with a slow hydration rate, and the cementing hydrates produced by its hydration include, but are not limited to, hydrated calcium silicate. The cementing component is composed of cementing materials and activators. The cementing materials include, but are not limited to, one or more combinations of slag, copper slag, phosphorus slag, coal gangue, bottom ash, rice husk ash, kiln ash, etc. The activator is an alkaline activator and includes, but is not limited to, one or more combinations of quicklime, hydrated lime, active magnesium oxide, sodium hydroxide, hydrated sodium silicate, etc.

[0011] The rigid materials described in this invention include, but are not limited to, steel pipes, polyvinyl chloride pipes, polyethylene pipes, reinforced high-density polyethylene pipes, polybutene pipes, polypropylene pipes, and fiber braided pultruded pipes; the flexible materials include, but are not limited to, basalt fiber composite fabrics, glass fiber composite fabrics, and carbon fiber composite fabrics.

[0012] The vertical reinforcement described in this invention penetrates all cross sections of the reinforced column in the constrained and solidified sulfate soil; when the constraining tube and reinforcement have good durability in the sulfate environment, they do not need to be treated with anti-corrosion and can be directly used in the preparation of the reinforced column in the constrained and solidified sulfate soil; the ratio of the ultimate constraining stress provided by the constraining tube to the strength of the solidified sulfate soil is greater than 0.3.

[0013] The dosage of the curing agent described in this invention is 10-100% of the total dry weight of the curing agent and the sulfate-saline soil; all components of the curing agent are industrial grade, and all curing agent materials have a specific surface area greater than 150 m². 2 / kg of powder.

[0014] The expansion component described in this invention needs to be determined according to the sulfate ion content in the sulfate-saline soil and the chemical equation for the formation of expansion hydrates by hydration, and the specific proportion of each component material in the expansion component needs to be determined by a known calculation method.

[0015] The cementing component described in this invention needs to be designed according to the hydration rate of the cementing component and the specific ratio of cementing material and alkali activator in the cementing component is determined through preliminary experiments; the mass ratio of the cementing material and alkali activator in the cementing component is in the range of 70~100:0~30.

[0016] The water-cement ratio control of the curing agent described in this invention refers to controlling the water-cement ratio according to the composition of the curing agent to meet the minimum water consumption required for all curing agent materials to be fully hydrated.

[0017] The application scope of the constrained and solidified sulfate-treated soil reinforced columns described in this invention includes, but is not limited to, airport engineering, road engineering, and industrial building engineering.

[0018] The construction process of the constrained and solidified sulfate-reinforced column described in this invention is as follows: First, an engineering survey is conducted on the sulfate-reinforced soil to understand its salt content, ion types, and physical properties. Second, the underground burial depth and above-ground height of the constrained and solidified sulfate-reinforced column are designed according to requirements. Then, based on the solidified sulfate-reinforced column strength, column body strength, and horizontal bearing capacity design value, the material composition and dimensions of the constraining tube, the type and quantity of reinforcement, the material composition of the expansion and cementing components in the curing agent, the curing agent dosage, and the water-cement ratio are determined. Finally, the reinforcement is evenly placed around the inner wall of the constraining tube. Construction parameters are determined through on-site testing. The curing agent is mixed with the sulfate-reinforced soil at a fixed water-cement ratio, uniformly filled into the constraining tube, and compacted to form the constrained and solidified sulfate-reinforced column. When the curing age is reached, the performance of the constrained and solidified sulfate-reinforced column is tested.

[0019] The advantages of this invention are: This invention utilizes sulfate-alkali soil as the main material for preparing constrained and solidified sulfate-alkali soil reinforced columns, significantly saving building materials and realizing the resource utilization of sulfate. By setting corrosion-resistant reinforcement materials and a reinforcement ratio ranging from 0.6% to 4.2%, the constrained and solidified sulfate-alkali soil reinforced columns have good resistance to horizontal loads. It also achieves significant carbon emission savings by completely replacing silicate-based cement with industrial waste residue as a binding material, providing a new type of column that is low-carbon, economical, and has good horizontal bearing capacity and durability for sulfate-alkali soil areas. Detailed Implementation

[0020] The following detailed description of a constrained and solidified sulfate-reinforced column suitable for lateral load-bearing, based on specific embodiments, further illustrates the present invention. However, the application forms and scope of the constrained and solidified sulfate-reinforced column provided by the present invention are not limited to this.

[0021] Example 1 The sulfate-laden soil in a certain airport project is to be reinforced using the method described in this invention, which is suitable for lateral load-bearing confined and solidified sulfate-laden soil reinforced column reinforcement. Engineering investigation of the sulfate-laden soil foundation revealed that the salt content of the sulfate-laden soil is 1.24%, and the main ionic component and content is Ca. 2+ 0.13%, Mg 2+ 0.12%, K + and Na + 0.08%, 0.88%, 0.01%, The moisture content of the sulfate-saline soil is 32%, with a content of 0.02%. The constrained and solidified sulfate-saline soil reinforced column, suitable for lateral load bearing, as described in this invention, is used for reinforcement. The design of the constrained and solidified sulfate-saline soil reinforced column is as follows: underground burial depth 2m, above-ground height 2m, and column diameter 300mm. The strength of the solidified sulfate-saline soil and the column body strength are 10MPa and 35MPa, respectively. The horizontal critical load of the constrained and solidified sulfate-saline soil reinforced column is 6kN.

[0022] A 12mm thick UPVC pipe, wrapped with two layers of GFRP fabric, was selected as the confinement pipe. Eight 9mm diameter bamboo strips were chosen as vertical reinforcements and treated with anti-corrosion agents. The curing agent, by weight, consisted of 3.6 parts aluminate cement, 5.8 parts quicklime, and 4.2 parts gypsum, and 7.5 parts slag and 2.5 parts quicklime as the binder. The curing agent dosage was 13% of the total dry weight of the curing agent and the sulfated soil, with a water-cement ratio of 0.45. The reinforcements were evenly placed on the inner wall of the confinement pipe and tightly adhered to its perimeter. Construction parameters were determined through field tests, and the moisture content of the sulfated soil was controlled. The curing agent, mixed with the sulfated soil at a fixed water-cement ratio, was then uniformly filled into the confinement pipe and compacted to form a confinement-cured sulfated soil reinforced column. Testing showed that after 28 days of curing, the strength of the cured sulfated soil, the column body strength of the confinement-cured sulfated soil reinforced column, and the horizontal critical load of the confinement-cured sulfated soil reinforced column all met the requirements.

[0023] Example 2 A highway project plans to treat the sulfate-laden soil using a reinforced column method for confined and solidified sulfate-laden soil suitable for lateral load-bearing, as described in this invention. Engineering investigation of the sulfate-laden soil foundation revealed a salt content of 21.58%, with the main ionic component and content being Ca. 2+ 3.12%, Mg 2+ 2.11%, K + and Na + 4.12%, 12.21%, 0.01%, The content of the sulfate-saline soil is 0.01%, and the moisture content is 30%. The constrained and solidified sulfate-saline soil reinforced column, suitable for lateral load bearing, as described in this invention, is used for reinforcement. The designed underground burial depth of the constrained and solidified sulfate-saline soil reinforced column is 6m, the above-ground height is 3m, and the column diameter is 250mm. The strength of the solidified sulfate-saline soil and the column body strength are 25MPa and 68MPa, respectively. The horizontal critical load of the constrained and solidified sulfate-saline soil reinforced column is 10kN.

[0024] A 10mm thick steel pipe, wrapped with four layers of BFRP fabric, was selected as the confinement pipe. Ten 12mm diameter steel bars were chosen as vertical reinforcements. The steel pipe and steel bars underwent anti-corrosion treatment. The curing agent, by weight, consisted of 2.6 parts aluminate cement, 3.6 parts quicklime, and 1.2 parts gypsum, and 9.0 parts slag and 1.0 part quicklime as the binder. The curing agent dosage was 54% of the total dry weight of the curing agent and the sulfated soil, with a water-cement ratio of 0.48. The reinforcement was evenly placed on the inner wall of the confinement pipe and tightly adhered to its perimeter. Construction parameters were determined through field tests, and the moisture content of the sulfated soil was controlled. The curing agent, mixed with the sulfated soil at a fixed water-cement ratio, was then uniformly filled into the confinement pipe and compacted to form a confinement-cured sulfated soil reinforced column. Tests showed that the strength of the solidified sulfate soil, the column strength of the reinforced column of the solidified sulfate soil, and the horizontal critical load of the reinforced column of the solidified sulfate soil all met the requirements after 28 days of curing.

[0025] Example 3 A high-speed railway project plans to reinforce its sulfate-affected soil using a method described in this invention, suitable for lateral load-bearing confined and solidified sulfate-affected soil reinforced column. Engineering investigation of the sulfate-affected soil foundation revealed a salt content of 32.03%, with the main ionic component and content being Ca. 2+ 3.82%, Mg 2+ 2.66%, K + and Na + 2.55%, 22.98%, 0.01%, The moisture content of the sulfate-treated soil is 43%, with a content of 0.01%. The constrained and solidified sulfate-treated soil reinforced column, suitable for lateral load bearing, as described in this invention, is used for reinforcement. The designed underground burial depth of the constrained and solidified sulfate-treated soil reinforced column is 5m, the above-ground height is 6m, and the column diameter is 420mm. The strength of the solidified sulfate-treated soil and the column body strength are 35MPa and 78MPa, respectively. The horizontal critical load of the constrained and solidified sulfate-treated soil reinforced column is 25kN.

[0026] A 23mm thick CFRP pipe was selected as the confinement pipe. Twenty 14mm diameter GFRP bars were chosen as vertical reinforcement, and bamboo reinforcement was installed inside the confinement pipe as circumferential reinforcement. The reinforcement was treated with anti-corrosion measures. The curing agent, by weight, consisted of 4.6 parts aluminate cement and 7.6 parts quicklime as its expansion component, and 9.0 parts slag and 1.0 part quicklime as its binding component. The curing agent dosage was 68% of the total dry weight of the curing agent and the sulfate soil, with a water-cement ratio of 0.48. The reinforcement was evenly placed on the inner wall of the confinement pipe and tightly adhered to its perimeter. Construction parameters were determined through field tests, and the moisture content of the sulfate soil was controlled. The curing agent was mixed evenly with the sulfate soil at a fixed water-cement ratio, filled into the confinement pipe, and compacted to form a confinement-cured sulfate soil reinforced column. Tests showed that the strength of the solidified sulfate soil, the column strength of the reinforced column of the solidified sulfate soil, and the horizontal critical load of the reinforced column of the solidified sulfate soil all met the requirements after 28 days of curing.

[0027] Example 4 A certain industrial building project plans to use a method described in this invention—a confined and solidified sulfate soil reinforcement column suitable for lateral load-bearing—to strengthen the sulfate soil foundation. Engineering investigation revealed that the sulfate soil has a salt content of 49.22%, and its main ionic components and contents are Ca. 2+ 5.05%, Mg 2+ 4.12%, K + and Na + 5.08%, 34.94%, 0.02%, The moisture content of the sulfate-treated soil is 0.01%, and the water content is 26%. The constrained and solidified sulfate-treated soil reinforced column, suitable for lateral load bearing, as described in this invention, is used for reinforcement. The designed underground burial depth of the constrained and solidified sulfate-treated soil reinforced column is 8m, the above-ground height is 3m, and the column diameter is 200mm. The strength of the solidified sulfate-treated soil and the column body strength are 21MPa and 55MPa, respectively. The horizontal critical load of the constrained and solidified sulfate-treated soil reinforced column is 4kN.

[0028] A 12mm thick HDPE pipe was wrapped with four layers of CFRP fabric. Five 12mm diameter BFRP reinforcing bars and five bamboo reinforcing bars were selected as vertical reinforcements, and the bamboo reinforcing bars were treated with anti-corrosion. The curing agent, calculated by weight, consisted of 4.2 parts aluminate cement and 6.3 parts quicklime as the expansion component, and 8.5 parts slag and 1.5 parts quicklime as the binder component. The curing agent dosage was 40% of the total dry weight of the curing agent and sulfate soil, with a water-cement ratio of 0.52. The reinforcing bars were evenly placed on the inner wall of the confinement pipe and tightly adhered to its perimeter. Construction parameters were determined through field tests, and the moisture content of the sulfate soil was controlled. The curing agent was mixed evenly with the sulfate soil at a fixed water-cement ratio, filled into the confinement pipe, and compacted to form a confinement-cured sulfate soil reinforced column. Testing showed that after 28 days of curing, the strength of the cured sulfate soil, the column body strength of the confinement-cured sulfate soil reinforced column, and the horizontal critical load of the confinement-cured sulfate soil reinforced column all met the requirements.

Claims

1. A reinforced column in confined and solidified sulfate soil suitable for lateral load-bearing, characterized in that: For sulfate-saline soils with a salt content of 1-50%, corrosion-resistant pipes with good mechanical properties are used as confining pipes, and corrosion-resistant reinforcing materials with good mechanical properties are used as vertical reinforcements, uniformly arranged inside the confining pipes and tightly attached to the inner wall of the pipes, with a reinforcement ratio ranging from 0.6-4.2%. The curing agent consists of an expansion component and a cementing component. A material that hydrates rapidly and forms expanding hydrates with sulfate ions is used as the expansion component, and a material with a slow hydration rate is used as the cementing component. The mass ratio of the expansion component to the cementing component is 15-70:30-85. The underground burial depth and above-ground height of the confined and cured sulfate-saline soil reinforced column are designed according to the requirements. Sulfate-saline soil is used as the column preparation material. The moisture content of the sulfate-saline soil and the water-cement ratio of the curing agent are controlled. The curing agent is mixed with the sulfate-saline soil at a fixed water-cement ratio, uniformly filled into the confining pipe, and compacted to form a confined and cured sulfate-saline soil. Reinforced columns in sulfate-confined soil exhibit high strength, good horizontal load-bearing capacity, and durability. The confining tube includes, but is not limited to, rigid and flexible materials, as well as combinations of both. The reinforcing material includes, but is not limited to, steel reinforcement, bamboo reinforcement, FRP reinforcement, and combinations of different types of reinforcement. When the confining tube is a rigid material or a combination of rigid and flexible materials, circumferential structural reinforcement can be optionally installed within the confining tube. When the confining tube is a flexible material, circumferential structural reinforcement must be installed within it. If the confining tube and reinforcement lack durability in a sulfate environment, anti-corrosion treatment is required. Anti-corrosion treatment methods include, but are not limited to, using epoxy resin, chlorinated polyolefin, polyurethane resin, fluorocarbon resin coatings, acrylic resin, polyurea waterproof and anti-corrosion coatings, and anti-corrosion structural adhesives to form an anti-corrosion layer.

2. A reinforced column for lateral load-bearing constrained sulfate soil according to claim 1, wherein the expansion component rapidly hydrates with sulfate ions in the sulfate soil to generate expansion hydrates, and the expansion hydrates generated by the hydration of the expansion component include, but are not limited to, hydrated calcium sulfoaluminate; the expansion component includes, but is not limited to, a mixture composed of aluminate cement, quicklime, and gypsum in a mass ratio ranging from 9 to 12:16-23:0 to 30; the cementing component is a material with a slow hydration rate, and the cementing hydrates generated by its hydration include, but are not limited to, hydrated calcium silicate; the cementing component includes, but is not limited to, a mixture composed of slag and alkali activator in a mass ratio ranging from 70 to 100:0 to 30.

3. A reinforced column for lateral load-bearing constrained and solidified sulfate soil as described in claim 1, characterized in that: The rigid materials include, but are not limited to, steel pipes, polyvinyl chloride pipes, polyethylene pipes, reinforced high-density polyethylene pipes, polybutene pipes, polypropylene pipes, and fiber-braided pultruded pipes; the flexible materials include, but are not limited to, basalt fiber composite fabrics, glass fiber composite fabrics, and carbon fiber composite fabrics; the vertical ribs penetrate through all cross sections of the constrained and solidified sulfate-treated soil reinforced column; when the constraining pipes and ribs have good durability in the sulfate environment, they do not require anti-corrosion treatment and can be directly used in the preparation of the constrained and solidified sulfate-treated soil reinforced column; the ratio of the ultimate constraining stress provided by the constraining pipe to the strength of the solidified sulfate-treated soil is greater than 0.

3.

4. A reinforced column for lateral load-bearing constrained and solidified sulfate soil as described in claim 1, characterized in that: The dosage of the curing agent is 10-100% of the total dry weight of the curing agent and the sulfate-saline soil; all components of the curing agent are industrial grade, and all curing agent materials have a specific surface area greater than 150 m². 2 / kg of powder.

5. A reinforced column for lateral load-bearing constrained and solidified sulfate soil as described in claim 1, characterized in that: The specific proportions of each component in the expansion component need to be determined according to the sulfate ion content in the sulfate-saline soil and the chemical equation for the formation of expansion hydrates by hydration, using known calculation methods.

6. A reinforced column for lateral load-bearing constrained and solidified sulfate soil as described in claim 1, characterized in that: The hydration rate of the cementing component needs to be designed based on the cementing component, and the specific ratio of cementing material and alkali activator in the cementing component needs to be determined through preliminary experiments.

7. A reinforced column for lateral load-bearing constrained and solidified sulfate soil according to claim 1, characterized in that: The aforementioned control of the water-cement ratio of the curing agent refers to controlling the water-cement ratio according to the composition of the curing agent to meet the minimum water consumption required for all curing agent materials to complete hydration.

8. A reinforced column for lateral load-bearing constrained and solidified sulfate soil according to claim 1, characterized in that: The applications of the constrained and solidified sulfate-reinforced columns include, but are not limited to, airport engineering, road engineering, and industrial building engineering.

9. A reinforced column for lateral load-bearing constrained and solidified sulfate soil according to claim 1, characterized in that: The construction process for reinforced columns in constrained and solidified sulfate-alkali soil is as follows: ① Conduct an engineering survey of the sulfate-alkali soil to understand its salt content, ion types, and physical properties; ② Design the underground depth and above-ground height of the reinforced column based on the required conditions. Then, determine the material composition and dimensions of the constraining tube, the type and quantity of reinforcement, the material composition of the expansion and cementing components in the curing agent, the dosage of the curing agent, and the water-cement ratio based on the design values ​​of the solidified sulfate-alkali soil strength, column body strength, and horizontal bearing capacity of the reinforced column. ③ Evenly place the reinforcement around the inner wall of the constraining tube. Determine the construction parameters through on-site tests. Mix the curing agent with the sulfate-alkali soil at a fixed water-cement ratio, fill it evenly into the constraining tube, and compact it in layers to form a reinforced column in constrained and solidified sulfate-alkali soil. Test the performance of the reinforced column in constrained and solidified sulfate-alkali soil when it reaches the curing age.