Modified grouting material for inhibiting water swelling of weak kaolinite interlayers and its application method

Abstract

This invention belongs to the field of geotechnical engineering reinforcement materials and grouting technology, specifically a modified grouting material for inhibiting water swelling of weak kaolinite interlayers and its application method. The material consists of a base material, a swelling inhibitor, auxiliary functional components, and water. The base material provides consolidation strength and bearing capacity. The swelling inhibitor inhibits lattice expansion through a triple mechanism: ion exchange to replace interlayer cations, organic membrane encapsulation to block water molecules, and inhibition of urease activity. The auxiliary functional components have both early-strength-promoting and chemical-cementing effects, shortening the consolidation period and enhancing water resistance. In application, geological surveys are conducted first, and the grouting process is carried out in a staggered, quincunx pattern. The mix ratio and pressure are dynamically adjusted using a forward-moving, segmented grouting process. After grouting, anchor mesh and shotcrete with steel arch support are implemented promptly, and a monitoring and feedback mechanism for expansion rate, permeability coefficient, and deformation rate is established. Secondary grouting is performed when necessary. The grout of this invention has good fluidity and strong resistance to water dilution, effectively controlling the water swelling of weak interlayers and ensuring long-term stability of the surrounding rock.

Description

Technical Field

[0001] This invention relates to the technical field, specifically to a modified grouting material for inhibiting the water-induced swelling of weak kaolinite interlayers and its application method. Background Technology

[0002] In geotechnical engineering projects such as mine roadway excavation and tunnel construction, strata containing weak interlayers of kaolinite are widely distributed. As a hydrophilic clay mineral, kaolinite's crystal structure is composed of silicon-oxygen tetrahedra and aluminum-oxygen octahedra linked by hydrogen bonds. When it comes into contact with water, water molecules easily enter the interlayer domain, triggering lattice expansion and hydration. This process leads to a significant decrease in the strength and volume expansion of the weak interlayer, which in turn induces engineering disasters such as surrounding rock instability, roadway floor heave, and roof collapse, seriously threatening construction safety and the lifespan of the project.

[0003] To address the issue of kaolinite swelling upon contact with water, existing technologies have developed various chemical components with specific inhibitory functions. For example, ordinary cement-based grouting materials are used, offering low-cost and convenient construction. However, while ordinary cement grout has acceptable fluidity at high water-cement ratios, the consolidated structure exhibits poor water resistance and is easily eroded by groundwater, leading to reinforcement failure. Lowering the water-cement ratio can increase strength, but it struggles to penetrate the micro-cracks within the kaolinite interlayer, limiting the grout's diffusion radius. More critically, cement hydration products cannot fundamentally inhibit the lattice expansion characteristics of kaolinite, leaving the swelling problem after grouting still prominent. Alternatively, a combined support approach using anchor mesh spraying and steel arch frames can be employed to actively or passively constrain surrounding rock deformation, but this approach focuses on "resistance" rather than "treatment," failing to address the root cause of kaolinite's water-swelling nature. Under high stress or water-rich conditions, the support structure is prone to failure due to excessive expansion pressure. Summary of the Invention

[0004] To solve the above problems, the present invention proposes the following technical solution: a modified grouting material for inhibiting the water-induced swelling of weak kaolinite interlayers, wherein the grouting material is composed of the following components by mass percentage: base material, swelling inhibitor, auxiliary functional components, and water;

[0005] The base material accounts for 55% to 70%, the expansion inhibitor accounts for 8% to 15%, the auxiliary functional components account for 3% to 8%, and the water accounts for 15% to 25%.

[0006] The base material is composed of cement and ultrafine fly ash; the expansion inhibitor is composed of potassium ion compounds, organic polymers and urease inhibitors; the auxiliary functional components are composed of early strength agents and calcium reagents.

[0007] The water-cement ratio of the grouting material is 0.3~0.6.

[0008] Preferably, water glass is added to the grouting material, and the grouting material and water glass are mixed at a volume ratio of 1:0.3~0.8 to form a two-liquid grout.

[0009] Preferably, the mass ratio of cement to ultrafine fly ash is 3:1 to 5:1, and the specific surface area of ​​ultrafine fly ash is ≥400m² / kg.

[0010] Preferably, the cement is P.O42.5 cement.

[0011] Preferably, the potassium ion compound in the swelling inhibitor is potassium chloride or potassium sulfate, the organic polymer is water-soluble epoxy resin or acrylamide, and the urease inhibitor is n-butylthiophosphoric triamine; the mass ratio of the potassium ion compound, the organic polymer, and the urease inhibitor is 4~8:4~7:0.1~1.

[0012] Preferably, the early-strength agent in the auxiliary functional component is calcium formate or calcium sulfoaluminate, and the calcium reagent component in the auxiliary functional component is calcium chloride; the mass ratio of the early-strength agent to the calcium reagent is 2~5:1~3.

[0013] Preferably, the base material also contains a polycarboxylate superplasticizer, the amount of which is 0.5% to 1.5% of the total mass of the base material, thereby reducing the amount of water used in the grouting material to maintain the sum of the mass percentages of each component at 100%.

[0014] The application method of grouting material modified to inhibit the water-induced swelling of weak kaolinite interlayers includes the following steps:

[0015] S1. First, core drilling combined with advanced ground-penetrating radar was used to determine the distribution range, thickness, kaolinite content, water inflow, and fracture development of the kaolinite-bearing weak interlayers. The kaolinite content was classified according to the following standards: high content ≥30%, medium content 10%~30%, low content <10%, and water inflow control threshold ≤0.5m³ / h. Then, core drilling samples were taken from the roof, floor, and sides of the tunnel. No less than 3 boreholes were drilled at each location, with a borehole spacing of no more than 2.5m and a borehole depth greater than the loosened zone of the surrounding rock. The obtained rock samples were tested for kaolinite content and physical and mechanical properties.

[0016] S2. Then, based on the survey results, determine the specific proportions of each component of the chemically modified grouting material. First, dry mix the base material, expansion inhibitor, and auxiliary functional components for 2-3 minutes, then add water and wet mix for 5-8 minutes. Let it stand for 3-5 minutes to eliminate air bubbles and obtain the grouting slurry.

[0017] S3. Construct grouting holes according to the plum blossom-shaped hole layout scheme. The drilling depth should penetrate the weak interlayer by no less than 1m. After drilling is completed, clean the rock debris in the hole, install the grouting pipe and fix it.

[0018] S4. The forward segmented grouting process is adopted, with an initial grouting pressure of 0.5~1.0MPa and a final pressure of 1.5~3.5MPa. The grouting parameters are adjusted according to the kaolinite content and water content. When the kaolinite content is ≥30%, the amount of expansion inhibitor is increased accordingly. In the water-rich section, 1%~2% water glass is added to form a two-liquid grout. The grouting of the water-rich section adopts the "low flow rate, multiple grouting" mode, with a grouting flow rate of 5~8L / min. After a single grouting is completed, grouting is performed at intervals of 2~4 hours. In the crack-developed section, the water-cement ratio is reduced to 0.4~0.5.

[0019] S5. Within 4 to 8 hours after grouting, implement anchor mesh spraying + steel arch support, and spray C25 concrete.

[0020] S6. Finally, install expansion gauges within the weak interlayers, conduct water pressure tests in the verification boreholes after grouting, and set up convergence monitoring points at the tunnel arch and both sides, with an interval of 10-20m between adjacent monitoring points. Collect data on expansion rate, permeability coefficient, and surrounding rock deformation. If the expansion rate is >2% or the permeability coefficient is >1×10⁻⁶, the expansion rate will be considered as a positive result. -6 When the deformation rate is greater than 5 mm / d or the grout ratio is adjusted, or secondary grouting is required, the secondary grouting should use a two-component grout made of grouting material and water glass.

[0021] The beneficial effects of this invention are as follows:

[0022] I. The swelling inhibitor of the present invention works in combination with potassium ion compounds, organic polymers and calcium reagents, acting on multiple levels such as ion exchange, physical encapsulation and fissure filling. The various components work together to produce a good inhibitory effect on the swelling of kaolinite when it comes into contact with water, which can effectively control the swelling of weak interlayers when they come into contact with water and ensure the long-term stability of the surrounding rock.

[0023] II. This invention uses a mixture of P.O42.5 cement and ultrafine fly ash as the base material, combined with a polycarboxylate superplasticizer, to maintain good fluidity of the grout even under low water-cement ratio conditions. This allows it to fully penetrate the micro-fractures within the kaolinite interlayer, while the two-liquid grout system effectively resists dilution by groundwater. Furthermore, by adjusting the water glass dosage, the gelation time can be controlled within a certain range, adapting to the grouting construction requirements under different water content geological conditions.

[0024] Third, this invention adopts a forward segmented grouting process, dynamically adjusting grouting parameters according to kaolinite content and water content, thus realizing differentiated construction for different geological conditions; after grouting, a monitoring and feedback mechanism is established to promptly detect abnormalities and carry out grouting replenishment, ensuring the continuous and stable reinforcement effect. Attached Figure Description

[0025] Figure 1 This is a schematic flowchart of the grouting material application method of the present invention.

[0026] Figure 2 This is a schematic diagram of the core sampling scheme of the present invention;

[0027] Figure 3 This is a schematic diagram of the plum blossom-shaped hole layout for grouting holes according to the present invention. Detailed Implementation

[0028] The embodiments of the present invention are described in detail below.

[0029] A modified grouting material for inhibiting water-induced swelling of weak kaolinite interlayers is provided. The grouting material comprises the following components by mass percentage: base material, expansion inhibitor, auxiliary functional component, and water; the base material accounts for 55%–70%, the expansion inhibitor accounts for 8%–15%, the auxiliary functional component accounts for 3%–8%, and the water accounts for 15%–25%; the base material is composed of cement and ultrafine fly ash; the expansion inhibitor is composed of potassium ion compounds, organic polymers, and urease inhibitors; the auxiliary functional component is composed of early-strength agents and calcium reagents; and the water-cement ratio of the grouting material is 0.3–0.6.

[0030] The grouting material contains water glass, and the grouting material and water glass are mixed at a volume ratio of 1:0.3~0.8 to form a two-liquid grout.

[0031] The mass ratio of cement to ultrafine fly ash is 3:1 to 5:1, and the specific surface area of ​​ultrafine fly ash is ≥400m² / kg; the cement is P.O42.5 cement.

[0032] The potassium ion compound in the swelling inhibitor is potassium chloride or potassium sulfate, the organic polymer is water-soluble epoxy resin or acrylamide, and the urease inhibitor is n-butylthiophosphoric triamine; the mass ratio of the potassium ion compound, the organic polymer, and the urease inhibitor is 4~8:4~7:0.1~1.

[0033] The following are embodiments of the present invention:

[0034] The application object of this embodiment is a weak kaolinite interlayer with a thickness of 0.2~0.8m, a kaolinite content of 13.9%, a water inflow of 3~5m³ / h, and the surrounding rock is the Qingshuijiang Formation slate with well-developed joints and fissures.

[0035] The grouting material is composed of the following components by mass percentage: base material 55%~70%, expansion inhibition synergistic system 8%~15%, auxiliary functional components 3%~8%, and water 15%~25%.

[0036] Water is used as a solvent to adjust the slurry concentration and ensure that all components are fully mixed and reacted; its mass percentage is 15% to 25%.

[0037] The base material is a mixture of P.O42.5 cement and ultrafine fly ash, with a mass ratio of P.O42.5 cement to ultrafine fly ash of 3:1 to 5:1, and the specific surface area of ​​ultrafine fly ash ≥400m² / kg.

[0038] P.O42.5 cement and ultrafine fly ash are mixed in a mass ratio of 3:1 to 5:1. The ultrafine fly ash has a specific surface area of ​​≥400m² / kg, which can fill hydration voids and improve the consolidation strength and fluidity of the slurry. Adding 0.5% to 1.5% polycarboxylate superplasticizer can further optimize the water-cement ratio (0.4 to 0.6), control the slump of the slurry at 120mm to 180mm, and improve the permeability.

[0039] The swelling inhibition synergistic system consists of a potassium ion compound, an organic polymer, and a urease inhibitor, with a mass ratio of 4~8:4~7:0.1~1.

[0040] Potassium ions replace kaolinite lattice cations through ion exchange, disrupting the expansion conditions. Organic polymers form a coating to prevent water molecules from contacting kaolinite. Urease inhibitors are used in this invention to suppress urease activity that may exist in the formation, prevent urea in groundwater from being decomposed to produce ammonia, and avoid ammonia from interfering with the slurry consolidation process.

[0041] The auxiliary functional components include an early-strength agent and a calcium reagent, with the mass ratio of early-strength agent to calcium reagent being 2~5:1~3;

[0042] Early-strength agents shorten the slurry consolidation cycle and avoid short-term water exposure failure; calcium reagents react with CO3 in formation water. 2- The reaction generates CaCO3 precipitate, which enhances the cementing effect and improves the water resistance stability of the solidified material;

[0043] Water glass is added to the grouting material. The grouting material and water glass are mixed at a volume ratio of 1:0.3~0.8 to form a two-liquid grout. The water glass is 40% concentration liquid sodium silicate. The gelation time is controlled by adjusting the amount of water glass to 30s~180s to meet the needs of rapid sealing under water inrush conditions.

[0044] See Figure 1 The present invention also provides a method for applying a modified grouting material to inhibit the water-induced swelling of weak kaolinite interlayers:

[0045] S1. First, core drilling combined with advanced ground-penetrating radar was used to determine the distribution range, thickness, kaolinite content, water inflow, and fracture development of the kaolinite-bearing weak interlayers. Kaolinite content was graded according to the following standards: high content ≥30%, medium content 10%~30%, low content <10%. The water inflow control threshold was ≤0.5 m³ / h. Then, core samples were taken from the tunnel roof, floor, and sidewalls. Please refer to [link / reference]. Figure 2 Three boreholes were drilled in the roof, floor and two sides of the tunnel, with a spacing of 2.0m and a drilling depth of 5m (2.8m for the loosened surrounding rock). The kaolinite content was found to be in the medium range (10%~30%), the water inflow was 4m³ / h, and the rock mass compressive strength was 15~20MPa.

[0046] S2. Then, based on the survey results, determine the specific proportions of each component of the chemically modified grouting material. In a typical scenario (water inflow ≤ 5 m³ / h), the mass percentages of each component of the chemically modified grouting material are as follows: P.O42.5 cement 48%, ultrafine fly ash 12%, potassium chloride 6%, water-soluble epoxy resin 6%, calcium formate 3%, calcium chloride 1%, NBPT 0.3%, water 23.7%, and add 1.0% polycarboxylate superplasticizer (based on the total mass of the base material). The grouting slurry is prepared according to the process of "dry mixing for 2~3 minutes + wet mixing for 5~8 minutes + standing for 3~5 minutes to remove air bubbles", with a water-cement ratio of 0.5 and a slump controlled at 120~150 mm.

[0047] In water-rich scenarios (water inflow > 5 m³ / h or a sudden increase in water inflow of 30 m³ / h or more), it is necessary to add 40% concentration of liquid sodium silicate (water glass) to the conventional formula to form a two-component grout. The grout volume ratio is chemically modified grout: water glass = 1:0.5. By adjusting the amount of water glass, the gelation time can be controlled from 30s to 180s to meet the rapid sealing requirements under water inflow conditions, thus producing the injection grout.

[0048] S3. In normal scenarios, a quincunx pattern perforation is used. Please refer to [reference needed]. Figure 3 The hole spacing is 2.0m, the drilling depth is 3.0m (ensuring penetration of the weak kaolinite interlayer ≥1.2m), and the hole diameter is 42mm. After drilling, high-pressure air is used to clean the rock debris in the hole to ensure that the hole is unobstructed. Then, φ42mm grouting pipes are installed, with an exposed length of 20cm, and are fixed together with the subsequent support structure. The operation procedure for water-rich scenarios is the same as that for conventional scenarios. However, if the water inflow increases or the roof rock debris gushes out during the rock debris cleaning process in water-rich / roof collapse risk sections, the cleaning must be stopped immediately. A water exploration and drainage drilling rig is used to explore the water accumulation and cavity conditions on the roof. At the same time, DN25 galvanized grouting pipes (length 3~9m) and drainage pipes are installed. The grouting pipe wall is cut with quincunx-shaped holes at 0.3m intervals to enhance the grout penetration effect. After installation, concrete is first used to fill and isolate the roof water inflow. After the concrete solidifies, the grouting hole fine construction is carried out.

[0049] S4. The conventional grouting process adopts a forward segmented grouting process, with each segment having a length of 1.5m, an initial grouting pressure of 0.8MPa, and gradually increasing the pressure to a final pressure of 1.8MPa. The grouting flow rate is controlled at 6L / min, and the grouting volume per grouting session does not exceed 8m³. The process is carried out in layers and stages, with an interval of more than 1 hour between each grouting session to avoid uneven consolidation caused by grout accumulation.

[0050] The grouting in the water-rich scenario adopts a two-liquid grouting process with a grout volume ratio of chemically modified grout: water glass = 1:0.5. The grouting sequence is first the two sides and then the arch. The grouting pressure is gradually increased to 0.7~3.5MPa. If the grouting process is interrupted, the pipeline should be cleaned in time to prevent blockage.

[0051] S5. Six hours after grouting is completed, anchor mesh spraying + steel arch support will be implemented. The anchor spacing is 150×150mm, the thickness of C25 sprayed concrete is 120mm, and the steel arch spacing is 1.0m.

[0052] S6. Finally, install dilatometers within the weak interlayer. After installation, connect the testing equipment to the display, and the data will be displayed on the monitor. Conduct a water pressure test in the verification borehole after grouting. Set up convergence monitoring points at intervals of 10-20m on the tunnel arch and both sides to collect data on expansion rate, permeability coefficient, and surrounding rock deformation. If the expansion rate is >2% and the permeability coefficient is >1×10⁻⁶, the data will be considered valid. -6 When the deformation rate is greater than 5 mm / d or the grout mix ratio is adjusted, or secondary grouting is performed. Secondary grouting uses a cement and water glass two-component grout, with the grouting pressure increased by 0.3~0.5 MPa compared to the initial grouting. Monitoring results show that after grouting, the water inflow rate decreased to 0.3 m³ / h, meeting the requirement of a water inflow control threshold of ≤0.5 m³ / h. The interlayer water swelling rate was 1.3%, core sample integrity was 92%, the surrounding rock convergence deformation rate was 2.8 mm / d, and the permeability coefficient was 8.5 × 10⁻⁶. -7 In summary, this grouting embodiment achieved significant results in terms of both physical water plugging and mechanical reinforcement.

[0053] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention, which are still covered within the protection scope of the present invention.

Claims

1. A modified grouting material for inhibiting the swelling of weak kaolinite interlayers upon contact with water, characterized in that, The grouting material is composed of the following components by mass percentage: base material, expansion inhibitor, auxiliary functional components, and water; The base material accounts for 55% to 70%, the expansion inhibitor accounts for 8% to 15%, the auxiliary functional components account for 3% to 8%, and the water accounts for 15% to 25%. The base material is composed of cement and ultrafine fly ash; the expansion inhibitor is composed of potassium ion compounds, organic polymers and urease inhibitors; the auxiliary functional components are composed of early strength agents and calcium reagents. The water-cement ratio of the grouting material is 0.3~0.

6.

2. The grouting material for inhibiting water swelling of weak kaolinite interlayers according to claim 1, characterized in that, The grouting material contains water glass, and the grouting material and water glass are mixed at a volume ratio of 1:0.3~0.8 to form a two-liquid grout.

3. The grouting material for inhibiting water swelling of weak kaolinite interlayers according to claim 2, characterized in that, The mass ratio of cement to ultrafine fly ash is 3:1 to 5:1, and the specific surface area of ​​ultrafine fly ash is ≥400m² / kg.

4. The grouting material for inhibiting water swelling of weak kaolinite interlayers according to claim 3, characterized in that, The cement is P.O42.5 cement.

5. The grouting material for inhibiting water swelling of weak kaolinite interlayers according to claim 4, characterized in that, The potassium ion compound in the swelling inhibitor is potassium chloride or potassium sulfate, the organic polymer is water-soluble epoxy resin or acrylamide, and the urease inhibitor is n-butylthiophosphoric triamine; the mass ratio of the potassium ion compound, the organic polymer, and the urease inhibitor is 4~8:4~7:0.1~1.

6. The grouting material for inhibiting water swelling of weak kaolinite interlayers according to claim 5, characterized in that, The early-strength agent in the auxiliary functional component is calcium formate or calcium sulfoaluminate, and the calcium reagent component in the auxiliary functional component is calcium chloride; the mass ratio of early-strength agent to calcium reagent is 2~5:1~3.

7. The grouting material for inhibiting water swelling of weak kaolinite interlayers according to claim 2, characterized in that, The base material also contains a polycarboxylate superplasticizer, which is added at a rate of 0.5% to 1.5% of the total mass of the base material. This reduces the amount of water used in the grouting material to maintain the total mass percentage of each component at 100%.

8. The application method of the modified grouting material for inhibiting water swelling of weak kaolinite interlayers according to any one of claims 6-7, characterized in that, Includes the following steps: S1. First, core drilling combined with advanced ground-penetrating radar was used to determine the distribution range, thickness, kaolinite content, water inflow, and fracture development of the kaolinite-bearing weak interlayers. The kaolinite content was classified according to the following standards: high content ≥30%, medium content 10%~30%, low content <10%, and water inflow control threshold ≤0.5m³ / h. Then, core drilling samples were taken from the roof, floor, and sides of the tunnel. No less than 3 boreholes were drilled at each location, with a borehole spacing of no more than 2.5m and a borehole depth greater than the loosened zone of the surrounding rock. The obtained rock samples were tested for kaolinite content and physical and mechanical properties. S2. Then, based on the survey results, determine the specific proportions of each component of the chemically modified grouting material. First, dry mix the base material, expansion inhibitor, and auxiliary functional components for 2-3 minutes, then add water and wet mix for 5-8 minutes. Let it stand for 3-5 minutes to eliminate air bubbles and obtain the grouting slurry. S3. Construct grouting holes according to the plum blossom-shaped hole layout scheme. The drilling depth should penetrate the weak interlayer by no less than 1m. After drilling is completed, clean the rock debris in the hole, install the grouting pipe and fix it. S4. The forward segmented grouting process is adopted, with an initial grouting pressure of 0.5~1.0MPa and a final pressure of 1.5~3.5MPa. The grouting parameters are adjusted according to the kaolinite content and water content. When the kaolinite content is ≥30%, the amount of expansion inhibitor is increased accordingly. In the water-rich section, 1%~2% water glass is added to form a two-liquid grout. The grouting of the water-rich section adopts the "low flow rate, multiple grouting" mode, with a grouting flow rate of 5~8L / min. After a single grouting is completed, grouting is performed at intervals of 2~4 hours. In the crack-developed section, the water-cement ratio is reduced to 0.4~0.

5. S5. Within 4 to 8 hours after grouting, implement anchor mesh spraying + steel arch support, and spray C25 concrete. S6. Finally, install expansion gauges within the weak interlayers, conduct water pressure tests in the verification boreholes after grouting, and set up convergence monitoring points at the tunnel arch and both sides, with an interval of 10-20m between adjacent monitoring points. Collect data on expansion rate, permeability coefficient, and surrounding rock deformation. If the expansion rate is >2% or the permeability coefficient is >1×10⁻⁶, the expansion rate will be considered as a positive result. -6 When the deformation rate is greater than 5 mm / d or the grout ratio is adjusted, or secondary grouting is required, the secondary grouting should use a two-component grout made of grouting material and water glass.

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