Composite modifier suitable for casing well backfill soil body and preparation method

Abstract

The invention discloses a composite modifier suitable for casing well backfill soil and a preparation method, the composite modifier is composed of 60-80 parts by weight of a main modifier, 10-20 parts by weight of an anti-crack stabilizer, 3-4 parts by weight of an active activator and 16-20 parts by weight of water, the main modifier comprises 45-60 parts by weight of cement and 15-20 parts by weight of lime, the anti-crack stabilizer comprises 8-15 parts by weight of phosphogypsum and 2-5 parts by weight of calcium carbonate whisker, and the active activator comprises 3-4 parts by weight of an active activator. The active exciting agent comprises the following components in parts by weight: 1-2 parts of bentonite, 0.5-1 part of nano silicon dioxide and 0.5-1 part of nano aluminum oxide. The main modifier can improve the mechanical property of the backfill soil body, the anti-crack stabilizer can improve the stability of the backfill soil body, the active activator can enhance the permeability resistance of the backfill soil body, and the main modifier, the anti-crack stabilizer and the active activator have a synergistic effect. The composite modifier can remarkably improve the mechanical property, the permeability resistance and the stability of a soil body in the casing well backfilling process, so that the sustainability and the safety of casing well engineering are improved.

Description

Technical Field

[0001] The present application relates to the technical field of water conservancy engineering materials, and in particular to a composite improver suitable for casing well backfill soil and a preparation method thereof. Background Art

[0002] Due to the limitations of financial, material and technical resources at the time of construction of some small reservoirs, many projects have poor quality and many "sequelae". In addition, after years of operation, hidden dangers have gradually been exposed and dangerous situations have occurred from time to time. In order to ensure the safety of the reservoir, it is necessary to remove the danger and reinforce it. At present, the commonly used measures include curtain grouting, casing clay backfill, concrete anti-seepage wall, split grouting, high-pressure jet grouting, geomembrane anti-seepage, etc. Among them, casing clay backfill measures are the most widely used in the reinforcement of small reservoirs in my country due to its economy and technical operability. Although casing clay backfill can prevent the occurrence of risks such as leakage of reservoir dam body, it still needs to be strengthened in terms of permeability, water stability and durability. In the casing clay backfill process, it is necessary to find replacement soil with better soil quality for filling. After the original soil is taken out from the dam body, due to the change of aggregate structure, when it is backfilled, the permeability coefficient increases, which cannot meet the anti-seepage requirements of the dam. The original soil needs to be cleared and piled up. These processes will increase construction costs, and the pile up of abandoned soil may cause secondary pollution and risks.

[0003] Inorganic improvers are generally in powder form. Traditional inorganic improvers mainly include cement, lime, fly ash, silica fume, coal gangue, etc. Since some engineering waste is added, the engineering cost can be effectively reduced, and the improved soil formed has good strength, rigidity and stability, so it is widely used in engineering practice. This curing agent mainly improves the strength of the soil through its own hydrolysis, hydration, and the chemical reaction products between the hydration products and the soil particles. However, the soil improvers currently available on the market have certain limitations in casing well backfilling, including limited mechanical property improvement effects and insufficient anti-permeability. Summary of the invention

[0004] The purpose of the embodiments of the present application is to provide a composite improver and preparation method suitable for casing well backfill soil, so as to solve the limitations of related soil improvers in casing well backfill, including limited mechanical property improvement effect, insufficient anti-permeability and other problems. The composite improver can significantly improve the mechanical properties, anti-permeability and stability of the soil during the casing well backfill process, thereby improving the sustainability and safety of the casing well project. The invention provides a feasible solution for improving the performance of casing well backfill soil.

[0005] In order to achieve the above technical objectives, the embodiments of the present invention are implemented through the following technical solutions: In a first aspect, a composite modifier suitable for backfill soil in a casing well is provided, the composite modifier consisting of 60 to 80 parts by weight of a main modifier, 10 to 20 parts by weight of an anti-cracking stabilizer, 3 to 4 parts by weight of an active activator and 16 to 20 parts by weight of water, wherein the main modifier comprises 45 to 60 parts by weight of cement and 15 to 20 parts by weight of lime, the anti-cracking stabilizer comprises 8 to 15 parts by weight of phosphogypsum and 2 to 5 parts by weight of calcium carbonate whiskers, and the active activator comprises 1 to 2 parts by weight of bentonite, 0.5 to 1 parts by weight of nano-silicon dioxide and 0.5 to 1 parts by weight of nano-alumina.

[0006] Furthermore, the cement is 32.5 silicate cement or 42.5 silicate cement, and the lime is quicklime with a purity of more than 95%.

[0007] Furthermore, the mesh number of the phosphogypsum is 1250 mesh, and the calcium oxide content is higher than 25%.

[0008] Furthermore, the calcium carbonate whisker has an effective substance content higher than 98%, a mesh size of 1250 meshes, and an aspect ratio greater than 30.

[0009] Furthermore, the bentonite is calcium-based bentonite with a mesh size of 1250 meshes and a water absorption rate greater than 2 times.

[0010] Furthermore, the nano silicon dioxide and aluminum oxide are of industrial grade, and the particle size is less than 30 nanometers.

[0011] In a second aspect, a method for preparing the composite modifier according to the first aspect is provided, the preparation method comprising the following steps: (1) Mix cement, lime, phosphogypsum, calcium carbonate whisker, bentonite, nano-silicon dioxide and nano-alumina and stir evenly; (2) Add water and continue stirring until the material reaches a fluid state to obtain a composite improver suitable for casing well backfill soil.

[0012] Before adding water and stirring, cement, lime, phosphogypsum, calcium carbonate whisker, bentonite, nano-silicon dioxide and nano-alumina are mixed and stirred evenly to avoid uneven dispersion of the admixtures; the improver is added to the soil to be solidified after adding water and stirring, which is conducive to the uniform dispersion of the composite improver in the backfill soil.

[0013] According to the above technical solution, the beneficial effects of the embodiments of the present invention are: The composite improver suitable for casing well backfill soil of the present invention is mainly composed of cement, lime, phosphogypsum, calcium carbonate whisker, bentonite, nano silicon dioxide and nano aluminum oxide. By adopting the composite improver, the advantages of cementitious materials, active minerals and nano modifiers are comprehensively utilized, so that the mechanical properties, anti-permeability and stability of the soil are significantly improved. By optimizing the basic mix ratio, the unconfined compressive strength of the improved soil prepared by the present invention can reach 3.89MPa, 4.20MPa and 5.96MPa at 3 days, 7 days and 28 days respectively. In addition, the material preparation method of the present invention is simple, the cost is relatively low, and it is suitable for large-scale production. The use of the improver can effectively extend the life of the casing well project and improve the safety of the dam.

[0014] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0016] Figure 1 Schematic diagram of the stress-strain relationship curve measured during the uniaxial compression test of the casing well backfill soil in Example 1.

[0017] Figure 2 Schematic diagram of the stress-strain relationship curve measured during the uniaxial compression test of the casing well backfill soil in Example 2.

[0018] Figure 3 Schematic diagram of the stress-strain relationship curve measured during the uniaxial compression test of the casing well backfill soil in Example 3. DETAILED DESCRIPTION

[0019] Specific embodiments of the present invention are described in detail below, but the present invention is not limited to the following embodiments.

[0020] Embodiment 1: The present embodiment provides a composite modifier suitable for casing well backfill soil, which is composed of 60 parts by weight of a main modifier, 10 parts by weight of an anti-cracking stabilizer, 3 parts by weight of an active stimulant and 16 parts by weight of water, wherein the composite modifier comprises 45 parts by weight of cement and 15 parts by weight of lime, 8 parts by weight of phosphogypsum and 2 parts by weight of calcium carbonate whiskers, 1 part by weight of bentonite, 1 part by weight of nano-silicon dioxide and 1 part by weight of nano-alumina.

[0021] The above-mentioned cement is 32.5 silicate cement or 42.5 silicate cement, and the lime is quicklime with a purity of more than 95%; the mesh number of phosphogypsum is 1250 mesh, and the calcium oxide content is higher than 25%; the effective substance content of the calcium carbonate whisker is higher than 98%, the mesh number is 1250 mesh, and the aspect ratio is greater than 30; the bentonite is calcium-based bentonite, the mesh number is 1250 mesh, and the water absorption rate is greater than 2 times; the nano-silicon dioxide and alumina are industrial grade, and the particle size is less than 30 nanometers.

[0022] Cement, lime, phosphogypsum, calcium carbonate whisker, bentonite, nano silicon dioxide and nano aluminum oxide are mixed and stirred evenly; water is then added, and stirring is continued until the material reaches a fluid state, thereby obtaining a composite improver suitable for casing well backfill soil.

[0023] As shown in Table 1, the unconfined compressive strength of the casing backfill soil obtained in this example can reach 3.23 MPa, 3.84 MPa, and 5.41 MPa at 3 days, 7 days, and 28 days, respectively, and the splitting tensile strength at 28 days is 0.78 MPa.

[0024] Figure 1 The figure is a schematic diagram of the stress-strain relationship curve measured when the casing well backfill soil body in Example 1 is subjected to a uniaxial compression test. It can be seen from the figure that the casing well backfill soil obtained in Example 1 has good mechanical properties.

[0025] Embodiment 2: The present embodiment provides a composite modifier suitable for casing well backfill soil, which is composed of 67 parts by weight of a main modifier, 15 parts by weight of an anti-cracking stabilizer, 3 parts by weight of an active activator and 18 parts by weight of water, wherein the composite modifier comprises 50 parts by weight of cement and 17 parts by weight of lime, 12 parts by weight of phosphogypsum and 3 parts by weight of calcium carbonate whiskers, 2 parts by weight of bentonite, 0.5 parts by weight of nano-silicon dioxide and 0.5 parts by weight of nano-alumina.

[0026] The above-mentioned cement is 32.5 silicate cement or 42.5 silicate cement, and the lime is quicklime with a purity of more than 95%; the mesh number of phosphogypsum is 1250 mesh, and the calcium oxide content is higher than 25%; the effective substance content of the calcium carbonate whisker is higher than 98%, the mesh number is 1250 mesh, and the aspect ratio is greater than 30; the bentonite is calcium-based bentonite, the mesh number is 1250 mesh, and the water absorption rate is greater than 2 times; the nano-silicon dioxide and alumina are industrial grade, and the particle size is less than 30 nanometers.

[0027] Cement, lime, phosphogypsum, calcium carbonate whisker, bentonite, nano silicon dioxide and nano aluminum oxide are mixed and stirred evenly; water is then added, and stirring is continued until the material reaches a fluid state, thereby obtaining a composite improver suitable for casing well backfill soil.

[0028] As shown in Table 1, the unconfined compressive strength of the casing backfill soil obtained in this example can reach 3.82 MPa, 4.15 MPa, and 5.73 MPa at 3 days, 7 days, and 28 days, respectively, and the splitting tensile strength at 28 days is 0.83 MPa. Figure 2 The figure is a schematic diagram of the stress-strain relationship curve measured when the casing well backfill soil body in Example 2 is subjected to a uniaxial compression test. It can be seen from the figure that the casing well backfill soil obtained in Example 2 has good mechanical properties.

[0029] Embodiment 3: The present embodiment provides a composite modifier suitable for casing well backfill soil, which is composed of 80 parts by weight of a main modifier, 20 parts by weight of an anti-cracking stabilizer, 4 parts by weight of an active activator and 20 parts by weight of water, wherein the composite modifier comprises 60 parts by weight of cement and 20 parts by weight of lime, 15 parts by weight of phosphogypsum and 5 parts by weight of calcium carbonate whiskers, 2 parts by weight of bentonite, 1 part by weight of nano-silicon dioxide and 1 part by weight of nano-alumina.

[0030] The cement is 32.5 silicate cement or 42.5 silicate cement, the lime is quicklime with a purity of more than 95%; the mesh number of phosphogypsum is 1250 mesh, and the calcium oxide content is higher than 25%; the effective substance content of calcium carbonate whisker is higher than 98%, the mesh number is 1250 mesh, and the aspect ratio is greater than 30; the bentonite is calcium-based bentonite, the mesh number is 1250 mesh, and the water absorption rate is greater than 2 times; the nano silicon dioxide and alumina are industrial grade, and the particle size is less than 30 nanometers. The cement, lime, phosphogypsum, calcium carbonate whisker, bentonite, nano silicon dioxide and nano alumina are mixed and stirred evenly; then water is added, and stirring is continued until the material reaches a flowing state to obtain a composite improver suitable for casing well backfill soil.

[0031] As shown in Table 1, the unconfined compressive strength of the casing backfill soil obtained in this example can reach 3.89 MPa, 4.20 MPa, and 5.96 MPa at 3 days, 7 days, and 28 days, respectively, and the splitting tensile strength at 28 days is 0.95 MPa.

[0032] Figure 3 The figure is a schematic diagram of the stress-strain relationship curve measured when the casing well backfill soil body in Example 3 is subjected to a uniaxial compression test. From the figure, it can be seen that the casing well backfill soil obtained in Example 3 has good mechanical properties.

[0033] Comparative Example 1: 60 parts by weight of cement and 20 parts by weight of lime are mixed and stirred evenly; then 16 parts by weight of water are added and stirred continuously until the material reaches a fluid state, thereby obtaining a composite improver suitable for backfilling soil in casing wells. The cement is 32.5 silicate cement or 42.5 silicate cement, and the lime is quicklime with a purity of more than 95%.

[0034] The unconfined compressive strength of the casing backfill soil obtained in this example can reach 1.63MPa, 2.45MPa and 3.71MPa at 3 days, 7 days and 28 days respectively, and the splitting tensile strength at 28 days is 0.35MPa.

[0035] Comparative Example 2: 60 parts by weight of cement, 20 parts by weight of lime, 15 parts by weight of phosphogypsum and 5 parts by weight of calcium carbonate whiskers are mixed and stirred evenly; then 18 parts by weight of water are added, and stirring is continued until the material reaches a fluid state, thereby obtaining a composite improver suitable for backfilling soil in casing wells. The cement is 32.5 silicate cement or 42.5 silicate cement, and the lime is quicklime with a purity of more than 95%; the mesh number of the phosphogypsum is 1250 mesh, and the calcium oxide content is higher than 25%; the effective substance content of the calcium carbonate whiskers is higher than 98%, the mesh number is 1250 mesh, and the aspect ratio is greater than 30.

[0036] The unconfined compressive strength of the casing backfill soil obtained in this example can reach 1.82MPa, 2.61MPa and 3.98MPa at 3 days, 7 days and 28 days respectively, and the splitting tensile strength at 28 days is 0.42MPa.

[0037] Comparative Example 3: 60 parts by weight of cement, 20 parts by weight of lime, 2 parts by weight of bentonite, 1 part by weight of nano silicon dioxide and 1 part by weight of nano alumina are mixed and stirred evenly; 20 parts by weight of water are added, and stirring is continued until the material reaches a fluid state, thereby obtaining a composite improver suitable for backfilling soil in casing wells. The cement is 32.5 silicate cement or 42.5 silicate cement, the lime is quicklime with a purity of more than 95%; the bentonite is calcium-based bentonite with a mesh size of 1250 mesh and a water absorption rate greater than 2 times; the nano silicon dioxide and alumina are industrial grade with a particle size of less than 30 nanometers.

[0038] The unconfined compressive strength of the casing backfill soil obtained in this example can reach 1.76MPa, 2.49MPa and 3.76MPa at 3 days, 7 days and 28 days respectively, and the splitting tensile strength at 28 days is 0.37MPa.

[0039] The specimens formed by the casing well backfill soil according to the above proportion, preparation method and curing system were taken, and a blank control sample (unimproved soil, that is, soil without any improver added to the casing well backfill soil) was added. The compressive strength and splitting tensile strength of the casing well backfill soil at 3d, 7d and 28d were measured respectively. The test results are shown in Table 1 and Appendix. Figures 1 to 3 shown.

[0040] Table 1: Performance test results of different ratios at 3, 7 and 28 days;

[0041] The results in Table 1 above show that, compared with the unimproved soil and comparative examples 1 to 3, the compressive and splitting tensile strengths of the casing well backfill soil treated with the composite modifiers in Examples 1 to 3 of the present invention are increased by more than several times, achieving the effect of soil strengthening. Since the main modifier is used to improve the mechanical properties of the backfill soil, the anti-cracking stabilizer is used to improve the stability of the backfill soil, and the active stimulant is used to enhance the anti-permeability of the backfill soil, the three work synergistically, and the attached figure also shows good mechanical properties. In addition, a large amount of engineering waste soil currently needs to be cleared and piled up. These processes will increase construction costs, and the stacking of waste soil may cause secondary pollution and risks. A new improvement technology will be adopted to improve the original dam body waste soil through nano-high-efficiency inorganic composite agents, which will be used for casing well clay solidification, filling and roadbed stabilization layer, and at the same time, the waste soil will be recycled.

[0042] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A composite improver suitable for backfill soil in casing wells, characterized in that: The composite modifier consists of 60-80 parts by weight of a main modifier, 10-20 parts by weight of an anti-cracking stabilizer, 3-4 parts by weight of an active activator and 16-20 parts by weight of water. The main modifier includes 45-60 parts by weight of cement and 15-20 parts by weight of lime, the anti-cracking stabilizer includes 8-15 parts by weight of phosphogypsum and 2-5 parts by weight of calcium carbonate whiskers, and the active activator includes 1-2 parts by weight of bentonite, 0.5-1 parts by weight of nano silicon dioxide and 0.5-1 parts by weight of nano aluminum oxide.

2. The composite improver according to claim 1, characterized in that The cement is 32.5 silicate cement or 42.5 silicate cement, and the lime is quicklime with a purity of more than 95%.

3. The composite improver according to claim 1, characterized in that The mesh number of the phosphogypsum is 1250 meshes, and the calcium oxide content is higher than 25%.

4. The composite improver according to claim 1, characterized in that The calcium carbonate whisker has an effective substance content higher than 98%, a mesh size of 1250 meshes, and an aspect ratio greater than 30.

5. The composite improver according to claim 1, characterized in that: The bentonite is calcium-based bentonite with a mesh size of 1250 meshes and a water absorption rate greater than 2 times.

6. The composite improver according to claim 1, characterized in that: The nano silicon dioxide and aluminum oxide are of industrial grade, and the particle size is less than 30 nanometers.

7. The method for preparing the composite modifier according to claim 1, characterized in that: The preparation method comprises the following steps: (1) mixing and stirring the cement, lime, phosphogypsum, calcium carbonate whisker, bentonite, nano-silicon dioxide and nano-aluminum oxide uniformly; (2) Add water and continue stirring until the material reaches a fluid state to obtain a composite improver suitable for casing well backfill soil.

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