A composite modifier applicable to the backfill soil of a casing well and a preparation method thereof

Abstract

The present invention discloses a composite modifier applicable to the backfill soil of a casing well and a preparation method thereof, which is composed of 60-80 parts by weight of a main modifier, 10-20 parts by weight of a crack resistance stabilizer, 3-4 parts by weight of an activity 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 crack resistance stabilizer includes 8-15 parts by weight of phosphogypsum and 2-5 parts by weight of calcium carbonate whiskers. The activity activator includes 1-2 parts by weight of bentonite, 0.5-1 part by weight of nano-silica, and 0.5-1 part by weight of nano-aluminum oxide. The main modifier can improve the mechanical properties of the backfill soil, the crack resistance stabilizer can improve the stability of the backfill soil, and the activity activator can enhance the anti-permeability of the backfill soil, and the three act synergistically. This composite modifier 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.

Description

Technical Field

[0001] This application relates to the technical field of water conservancy engineering materials, and particularly relates to a composite modifier applicable to the soil for well-sleeved backfill and a preparation method thereof. Background Art

[0002] Due to the limitations of financial resources, material resources, and technical strength at the time of construction of some small reservoirs, there are many problems in many projects, such as poor quality and many "sequelae". Coupled with years of operation, hidden dangers are gradually exposed and dangerous situations occur from time to time. To ensure the safety of the reservoir, it is necessary to carry out danger removal and reinforcement. Currently, common measures include curtain grouting, well-sleeved clay backfill, concrete cut-off wall, split grouting, high-pressure jet grouting, geomembrane anti-seepage, etc. Among them, the well-sleeved clay backfill measure is most widely used in the reinforcement of small reservoirs in China due to its economy and easy technical operation. Although the well-sleeved clay backfill can prevent risks such as seepage of the reservoir dam body, it still needs to be strengthened in terms of permeability, water stability, and durability. Moreover, in the well-sleeved clay backfill process, it is necessary to find better-quality replacement soil for filling. After the original soil is taken out from the dam body, due to the change of the aggregate structure, when it is re-backfilled, the permeability coefficient increases, which cannot meet the anti-seepage requirements of the dam. The original soil needs to be transported and stacked, and these processes will increase the construction cost, and the stacking of the discarded soil may cause secondary pollution and risks.

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

[0004] The purpose of the embodiments of this application is to provide a composite modifier applicable to the soil for well-sleeved backfill and a preparation method thereof, so as to solve the problems that the existing soil modifiers have certain limitations in well-sleeved backfill, including limited improvement effect on mechanical properties and insufficient anti-permeability. This composite modifier can significantly improve the mechanical properties, anti-permeability, and stability of the soil during the well-sleeved backfill process, thereby improving the sustainability and safety of the well-sleeved project. This invention provides a feasible solution for improving the performance of the soil for well-sleeved backfill.

[0005] In order to achieve the above technical objectives, the embodiments of the present invention are implemented through the following technical solutions:

[0006] In a first aspect, a composite modifier applicable to the soil body backfilled in a casing well is provided. The composite modifier is composed of 60-80 parts by weight of a main modifier, 10-20 parts by weight of a crack resistance stabilizer, 3-4 parts by weight of an activity activator, and 16-20 parts by weight of water. Among them, the main modifier includes 45-60 parts by weight of cement and 15-20 parts by weight of lime, the crack resistance stabilizer includes 8-15 parts by weight of phosphogypsum and 2-5 parts by weight of calcium carbonate whiskers, and the activity activator includes 1-2 parts by weight of bentonite, 0.5-1 part by weight of nano-silica, and 0.5-1 part by weight of nano-aluminum oxide.

[0007] Further, the cement is 32.5 Portland cement or 42.5 Portland cement, and the lime is quicklime with a purity of more than 95%.

[0008] Further, the phosphogypsum has a mesh number of 1250, and the calcium oxide content is higher than 25%.

[0009] Further, the effective substance content of the calcium carbonate whiskers is higher than 98%, the mesh number is 1250, and the aspect ratio is greater than 30.

[0010] Further, the bentonite is calcium-based bentonite, the mesh number is 1250, and the water absorption rate is greater than 2 times.

[0011] Further, the nano-silica and alumina are industrial grade, and the particle size is less than 30 nanometers.

[0012] In a second aspect, a preparation method of the composite modifier according to the first aspect is provided. The preparation method includes the following steps:

[0013] (1) Mix and stir evenly cement, lime, phosphogypsum, calcium carbonate whiskers, bentonite, nano-silica, and nano-aluminum oxide;

[0014] (2) Add water and continue to stir until the material reaches a flowing state to obtain a composite modifier applicable to the soil body backfilled in a casing well.

[0015] Before adding water and stirring, mix and stir evenly cement, lime, phosphogypsum, calcium carbonate whiskers, bentonite, nano-silica, and nano-aluminum oxide, so as to avoid uneven dispersion of the admixture; after adding water and stirring, the modifier is put into the soil body to be solidified, which is beneficial to the uniform dispersion of the composite modifier in the backfilled soil body.

[0016] According to the above technical solutions, the beneficial effects of the embodiments of the present invention are:

[0017] The composite modifier applicable to the soil body backfilled in the casing well of the present invention is mainly composed of cement, lime, phosphogypsum, calcium carbonate whiskers, bentonite, nano-silica and nano-aluminum oxide. By adopting the composite modifier, the advantages of cementitious materials, active minerals and nano-modifiers are comprehensively utilized, so that the mechanical properties, impermeability and stability of the soil body are significantly improved. By optimizing the basic mix ratio, the unconfined compressive strengths of the improved soil at 3 days, 7 days and 28 days can reach 3.89 MPa, 4.20 MPa and 5.96 MPa 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 modifier can effectively extend the service life of the casing well project and improve the safety of the dam.

[0018] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit this application. Brief Description of the Drawings

[0019] The drawings here are incorporated into the specification and form a part of this specification, showing the embodiments consistent with this application, and are used together with the specification to explain the principles of this application.

[0020] Figure 1 It is a schematic diagram of the stress-strain relationship curve measured during the uniaxial compression test on the soil body backfilled in the casing well in Example 1.

[0021] Figure 2 It is a schematic diagram of the stress-strain relationship curve measured during the uniaxial compression test on the soil body backfilled in the casing well in Example 2.

[0022] Figure 3 It is a schematic diagram of the stress-strain relationship curve measured during the uniaxial compression test on the soil body backfilled in the casing well in Example 3. Detailed Embodiments

[0023] The following details the specific embodiments of the present invention, but the content of the present invention is not limited to the following embodiments.

[0024] Example 1:

[0025] A composite modifier applicable to the soil body backfilled in the casing well provided in this embodiment is composed of 60 parts by weight of the main modifier, 10 parts by weight of the crack resistance stabilizer, 3 parts by weight of the activity activator and 16 parts by weight of water. Among them, there are 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-silica and 1 part by weight of nano-aluminum oxide.

[0026] The above cement is 32.5 Portland cement or 42.5 Portland cement, the lime is quicklime with a purity above 95%; the phosphorus gypsum has a mesh number of 1250, 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, and the aspect ratio is greater than 30; the bentonite is calcium-based bentonite, the mesh number is 1250, and the water absorption rate is greater than 2 times; the nano-silica and alumina are industrial grade, and the particle size is less than 30 nanometers.

[0027] Mix the cement, lime, phosphorus gypsum, calcium carbonate whiskers, bentonite, and nano-silica and nano-alumina evenly; then add water and continue to stir until the material reaches a flowing state to obtain a composite modifier suitable for the soil body backfilled in the casing well.

[0028] As shown in Table 1, the unconfined compressive strengths of the soil body backfilled in the casing well prepared in this example at 3 days, 7 days, and 28 days can reach 3.23 MPa, 3.84 MPa, and 5.41 MPa respectively, and the splitting tensile strength at 28 days is 0.78 MPa.

[0029] Figure 1 It is a schematic diagram of the stress-strain relationship curve measured during the uniaxial compression test on the soil body backfilled in the casing well in Example 1. It can be seen from the figure that the soil backfilled in the casing well obtained in Example 1 has good mechanical properties.

[0030] Example 2:

[0031] A composite modifier suitable for the soil body backfilled in the casing well provided in this example is composed of 67 parts by weight of the main modifier, 15 parts by weight of the crack resistance stabilizer, 3 parts by weight of the activity activator, and 18 parts by weight of water. Among them, there are 50 parts by weight of cement and 17 parts by weight of lime, 12 parts by weight of phosphorus gypsum and 3 parts by weight of calcium carbonate whiskers, 2 parts by weight of bentonite, 0.5 parts by weight of nano-silica and 0.5 parts by weight of nano-alumina.

[0032] The above cement is 32.5 Portland cement or 42.5 Portland cement, the lime is quicklime with a purity above 95%; the phosphorus gypsum has a mesh number of 1250, 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, and the aspect ratio is greater than 30; the bentonite is calcium-based bentonite, the mesh number is 1250, and the water absorption rate is greater than 2 times; the nano-silica and alumina are industrial grade, and the particle size is less than 30 nanometers.

[0033] Mix the cement, lime, phosphorus gypsum, calcium carbonate whiskers, bentonite, and nano-silica and nano-alumina evenly; then add water and continue to stir until the material reaches a flowing state to obtain a composite modifier suitable for the soil body backfilled in the casing well.

[0034] As shown in Table 1, the unconfined compressive strengths of the shaft-sinking backfill soil prepared in this example at 3 days, 7 days, and 28 days can reach 3.82 MPa, 4.15 MPa, and 5.73 MPa respectively, and the splitting tensile strength at 28 days is 0.83 MPa. Figure 2 It is a schematic diagram of the stress-strain relationship curve measured during the uniaxial compression test of the shaft-sinking backfill soil in Example 2. It can be seen from the figure that the shaft-sinking backfill soil obtained in this Example 2 has good mechanical properties.

[0035] Example 3:

[0036] A composite modifier applicable to shaft-sinking backfill soil provided in this example is composed of 80 parts by weight of the main modifier, 20 parts by weight of the crack-resistant stabilizer, 4 parts by weight of the activity activator, and 20 parts by weight of water. Among them, there are 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-silica and 1 part by weight of nano-aluminum oxide.

[0037] The above cement is 32.5 Portland cement or 42.5 Portland cement, and the lime is quicklime with a purity of more than 95%; the phosphogypsum has a mesh number of 1250 meshes and a calcium oxide content higher than 25%; the effective substance content of the calcium carbonate whiskers is higher than 98%, the mesh number is 1250 meshes, and the aspect ratio is greater than 30; the bentonite is calcium-based bentonite with a mesh number of 1250 meshes and a water absorption rate greater than 2 times; the nano-silica and alumina are industrial grade with a particle size less than 30 nanometers. Mix the cement, lime, phosphogypsum, calcium carbonate whiskers, bentonite, and nano-silica and nano-aluminum oxide evenly; then add water and continue to stir until the material reaches a flowing state to obtain a composite modifier applicable to shaft-sinking backfill soil.

[0038] As shown in Table 1, the unconfined compressive strengths of the shaft-sinking backfill soil prepared in this example at 3 days, 7 days, and 28 days can reach 3.89 MPa, 4.20 MPa, and 5.96 MPa respectively, and the splitting tensile strength at 28 days is 0.95 MPa.

[0039] Figure 3 It is a schematic diagram of the stress-strain relationship curve measured during the uniaxial compression test of the shaft-sinking backfill soil in Example 3. It can be seen from the figure that the shaft-sinking backfill soil obtained in this Example 3 has good mechanical properties.

[0040] Comparative Example 1:

[0041] Mix 60 parts by weight of cement and 20 parts by weight of lime evenly; then add 16 parts by weight of water and continue to stir until the material reaches a flowing state to obtain a composite modifier applicable to shaft-sinking backfill soil. The cement is 32.5 Portland cement or 42.5 Portland cement, and the lime is quicklime with a purity of more than 95%.

[0042] The unconfined compressive strengths of the shaft sinking backfill soil prepared in this example at 3 days, 7 days, and 28 days can reach 1.63 MPa, 2.45 MPa, and 3.71 MPa respectively, and the splitting tensile strength at 28 days is 0.35 MPa.

[0043] Comparative Example 2:

[0044] Mix 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 evenly; then add 18 parts by weight of water and continue stirring until the material reaches a flowing state to obtain a composite modifier suitable for shaft sinking backfill soil. The cement is 32.5 Portland cement or 42.5 Portland cement, the lime is quicklime with a purity above 95%; the phosphogypsum has a mesh number of 1250 and a calcium oxide content higher than 25%; the effective substance content of the calcium carbonate whiskers is higher than 98%, the mesh number is 1250, and the aspect ratio is greater than 30.

[0045] The unconfined compressive strengths of the shaft sinking backfill soil prepared in this example at 3 days, 7 days, and 28 days can reach 1.82 MPa, 2.61 MPa, and 3.98 MPa respectively, and the splitting tensile strength at 28 days is 0.42 MPa.

[0046] Comparative Example 3:

[0047] Mix 60 parts by weight of cement, 20 parts by weight of lime, 2 parts by weight of bentonite, 1 part by weight of nano-silica, and 1 part by weight of nano-aluminum oxide evenly; then add 20 parts by weight of water and continue stirring until the material reaches a flowing state to obtain a composite modifier suitable for shaft sinking backfill soil. The cement is 32.5 Portland cement or 42.5 Portland cement, the lime is quicklime with a purity above 95%; the bentonite is calcium-based bentonite with a mesh number of 1250 and a water absorption rate greater than 2 times; the nano-silica and alumina are industrial grade with a particle size less than 30 nm.

[0048] The unconfined compressive strengths of the shaft sinking backfill soil prepared in this example at 3 days, 7 days, and 28 days can reach 1.76 MPa, 2.49 MPa, and 3.76 MPa respectively, and the splitting tensile strength at 28 days is 0.37 MPa.

[0049] Take the shaft sinking backfill soil, specimens formed according to the above ratio, preparation method, and curing system, and add a blank control example (unmodified soil, that is, soil without adding any modifier to the shaft sinking backfill soil), and measure the compressive strength and splitting tensile strength of the shaft sinking backfill soil at the ages of 3d, 7d, and 28d respectively. The test results are shown in Table 1 and the appendix Figures 1 - 3 as shown.

[0050] Table 1: Performance test results of different ratios at 3, 7, and 28 days;

[0051]

[0052] As shown by the results in Table 1 above, compared with the unimproved soil and Comparative Examples 1-3, the compressive and splitting tensile strengths of the soil body backfilled by the composite improvers in Examples 1-3 of the present invention have increased by several times, achieving the effect of soil strengthening. Since the main improver is used to improve the mechanical properties of the backfilled soil body, the crack-resistant stabilizer is used to improve the stability of the backfilled soil body, and the activity activator is used to enhance the anti-permeability of the backfilled soil body, the three act synergistically, and the attached drawings also show good mechanical properties. In addition, at present, a large number of engineering waste soils need to be cleared and stacked, and these processes will increase the construction cost, and the stacking of waste soil bodies may cause secondary pollution and risks. The new improvement technology will be adopted to improve the original dam waste soil by a nano-efficient inorganic composite agent for the clay solidification, filling and subgrade stabilizing layer of the casing well, and at the same time, the waste soil body will be recycled.

[0053] It should be understood that for those of ordinary skill in the art, modifications or variations can be made according to the above description, and all such modifications and variations should fall within the protection scope 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 nano 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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