A test method for evaluating the long-term effects of chemical grouting in porous and fractured rock formations on groundwater quality

Abstract

The present invention discloses an experimental method for evaluating the long-term impact of chemical grouting of porous and fractured rock formations on groundwater quality, comprising the following steps: construction of a model system, pretreatment of test materials and filling of a grouting model, slurry selection and closed grouting, grouting body infiltration, and water quality analysis and hydrochemical analysis and evaluation of the filtered water. The method of the present invention has the characteristics of replaceable grouting materials and adjustable infiltration flow rate; it can realize long-term real-time dynamic monitoring and recording of infiltration flow rate through digital flow and velocity meters, and measure the permeability coefficient of the grouting body; by analyzing the water quality information of the grouting body leachate, it is possible to explore the pollution effect of grouting on the groundwater environment and the interaction between the slurry and the geological body; the method also provides a subsequent hydrochemical analysis template of the grouting body leachate, thereby constituting an indoor systematic evaluation of grouting pollution.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrogeology and environmental geotechnical engineering, and particularly relates to a test method for evaluating the long-term impact of chemical grouting in porous and fissured rock strata on groundwater quality. Background Art

[0002] Grouting is a common engineering technique used in mine remediation. It's crucial for shaft and tunnel reinforcement and leakage prevention, but it also poses a potential risk of contamination to the regional groundwater environment. During grouting, large amounts of slurry can alter groundwater pH, total dissolved solids, and ion concentration, impacting water quality. Therefore, it's necessary to conduct long-term model tests to investigate the effects of specific grouting materials on groundwater quality, studying their pollution characteristics and patterns, and assessing their severity and degradation cycle.

[0003] Currently, existing research on the impact of grouting on the groundwater environment primarily involves collecting water samples from underground drainage holes and excavation water points, submitting these samples for testing and conducting relevant water quality chemical analysis to explore the inherent relationship between grouting activities and changes in the groundwater environment. This approach is somewhat random and is significantly constrained by actual site conditions and engineering plans. It cannot rule out excessive interference of localized anomalous geochemical properties of the rock mass with water quality. Sampling is also time-consuming and labor-intensive, resulting in inflexibility and high sampling costs. Existing laboratory research primarily relies on shake flask batch experiments on water-rock interactions, which cannot provide dynamic groundwater dynamics and cannot measure groundwater infiltration.

[0004] Given this, it is urgent to expand the current research paradigm. Therefore, a new post-grouting percolation model system for geological bodies, applicable to a variety of chemical grouting materials, capable of simulating groundwater flow rates within a specific range, and possessing cyclic and sustainable characteristics, is constructed. This will form a research and evaluation method system for grouting contamination of groundwater environments, thereby more accurately evaluating the potential impacts of grouting activities on the groundwater environment and their mechanisms of action. Summary of the Invention

[0005] Technical problems to be solved: In response to the above technical problems, the present invention provides an experimental method for evaluating the long-term impact of chemical grouting in porous and fractured rock formations on groundwater quality, so as to solve the problems that the current related research methods are not flexible enough, have limitations and cannot be sustained for multiple cycles.

[0006] Technical solution: The present invention provides a test method for evaluating the long-term impact of chemical grouting in porous and fractured rock formations on groundwater quality, comprising the following steps:

[0007] S1. Construction of the model system: The model system includes a grouting system for grouting operations and an infiltration system for infiltration operations;

[0008] S2. Pretreatment of test materials and filling of grouting models: Based on the specific working conditions to be studied, porous and fractured rock samples within the study area are selected and tested for their key properties. The obtained data serves as preliminary basic data for subsequent tests. The porous and fractured rock blocks are then fully pre-saturated with water to simulate the water-rich and saturated environment in actual formations.

[0009] S3. Grout selection and closed grouting: Select the type of grout according to the research plan requirements and perform closed grouting on the pores and fractures in the model;

[0010] S4. Grouting penetration: After the grouting liquid is fully solidified, select an appropriate seepage rate to penetrate the grouting model;

[0011] S5. Analyze the water quality of the percolation water: During the test, collect the percolation water from the grouting body and conduct a comprehensive and special water quality analysis.

[0012] S6. Hydrochemical analysis and evaluation: Based on the acquired water quality analysis data, analyze the extent of the impact of chemical grouting in porous and fractured rock formations on groundwater quality and its dynamic change effect over time.

[0013] Preferably, the grouting system includes a stepper motor propulsion device, a core model device, a paperless recorder, a slurry collection tank and a slurry reflux tank, the stepper motor propulsion device includes a base, a guide rail slide is provided on the base, a stepper motor is provided on the guide rail slide, the output shaft of the stepper motor is connected to the side wall of the base through a transmission screw, a moving slider is provided on the transmission screw, the moving slider is connected to the front end of the piston cylinder liquid storage tank through a piston push rod, a slurry outlet interface is provided at the end of the piston cylinder liquid storage tank, a slurry stop valve is provided at the slurry outlet interface, a motion sensor is provided between the base and the guide rail slide, and a limit switch is provided on the side wall of the base away from the stepper motor; the core model device includes a barrel body, the barrel body is set on a support seat, the top of the barrel body is provided with an upper flange plate, the upper flange plate is connected to the upper flange connection plate of the barrel body side wall by fastening screws, and a plastic flange gasket and a rubber diaphragm gasket are provided between the upper flange plate and the upper flange connection plate. The upper flange is provided with an injection pipe, the side wall of the injection pipe is provided with a return pipe, the return pipe is provided with a check valve, the inner wall of the barrel body is provided with a cast filling layer, the cast filling layer is provided with a hole and crack injected rock block, the outer wall of the hole and crack injected rock block is provided with a rubber diaphragm, the outer walls of the upper and lower ends of the rubber diaphragm are provided with a tightening ring, the bottom end of the barrel body is provided with a lower flange, the lower flange is connected to the lower flange connection plate of the barrel body side wall by fastening screws, the lower A plastic flange gasket and a rubber diaphragm gasket are provided between the flange and the lower flange connection plate. A through hole is opened on the lower flange, a filter is provided in the through hole, the through hole is connected to the liquid outlet pipe, a ball valve switch is provided on the liquid outlet pipe, and a pressure transmitter is provided on both the upper flange and the lower flange. The inlet of the injection pipe is connected to the slurry outlet interface; the pressure transmitter is connected to a paperless recorder, the return liquid pipe is connected to the slurry reflux tank, and the outlet of the liquid outlet pipe is connected to the slurry collection tank.

[0014] Furthermore, stopping the grouting operation requires one of the following conditions: ① When the internal pores of the rock block are completely penetrated by the slurry and the slurry flows out steadily from the outlet pipe, it indicates that the rock grouting has reached a saturated state and the grouting can be stopped; ② When the stepper motor propulsion device reaches the maximum output torque of the stepper motor, that is, when the slider in the stepper motor propulsion device can no longer continue to push the piston cylinder, the grouting is stopped to prevent the equipment from being overloaded and damaged.

[0015] Furthermore, the infiltration system includes a core model device, a constant pressure water supply control cabinet, a leachate storage tank and a digital flow rate flowmeter. The pressure transmitter in the core model device is connected to the constant pressure water supply control cabinet, the leachate storage tank is connected to the outlet of the liquid outlet pipe, and the digital flow rate flowmeter is arranged on the liquid outlet pipe.

[0016] Preferably, the slurry in step S3 includes lignin, phosphoric acid curing agent urea-formaldehyde resin, oxalic acid curing agent urea-formaldehyde resin, acrylate, epoxy resin and polyurethane.

[0017] Preferably, the indicators of water quality analysis in step S5 include general measurement indicators and organic indicators, and the general measurement indicators include K + , Ca 2+ 、Na + Mg 2+ 、CI - 、 OH - 、 F - 、 Br - 、 As well as pH, total dissolved solids TDS, electrical conductivity EC, total hardness TH and oxidation-reduction potential ORP; the organic indicators include total organic carbon TOC, chemical oxygen demand COD, free formaldehyde, methylene bisacrylamide, bisphenol A and free isocyanate; the collected leachate is analyzed for water quality according to the principle of setting time intervals from dense to sparse.

[0018] Preferably, the water chemical analysis and evaluation in step S6 includes the following steps:

[0019] S6-1. Draw a map based on the measured leachate ion concentration to determine the leachate hydrochemical type. This will allow analysis of the pattern of changes in the groundwater hydrochemical type caused by the grouting fluid and the identification of the negative effects of grouting contaminants on the overall hydrochemical characteristics of the regional groundwater at a macro level.

[0020] S6-2. Develop time-dependent evolution curves of water quality indicators and ion concentrations to analyze the impact patterns and changing trends of the grouting fluid on groundwater quality indicators. By fitting indicators that change significantly during monitoring, accurately determine the time required for the grouting contamination effect to change from significant to negligible. This allows for the identification of the underlying mechanisms of grouting contaminants affecting regional groundwater quality at a microscopic level, and the assessment of the impact period of grouting on groundwater ion balance.

[0021] S6-3. Draw a Schoeller diagram to analyze the degree of disturbance to groundwater quality caused by the grouting project. By analyzing the fluctuation range of water quality indicators, the degree of normalization and degradation of groundwater quality in the area after grouting can be determined.

[0022] S6-4. Draw a correlation heat map to analyze the internal connections and interactions between various pollution factors in the grouting pollution process, and analyze the sources and mechanisms of grouting pollutants from the perspective of indicator correlation;

[0023] S6-5. Draw a PCA principal component map to analyze the dominant role of the grouting fluid in the groundwater pollution process and reveal the main mechanism of action in the slurry pollution process from the perspective of multivariate statistical dimensionality reduction.

[0024] Beneficial effects: 1) Replaceability of grouting materials: After completing the percolation test of one slurry, the device can be disassembled and replaced with another slurry to be studied, thus realizing continuous, flexible and highly customized experimental research; 2) Adjustability of infiltration flow rate: The required infiltration flow rate can be adjusted by changing the output parameters such as the osmotic pressure of the constant pressure water supply control cabinet; 3) Long-term real-time dynamic monitoring and recording of the infiltration flow rate can be achieved through digital flow and velocity meters, and the permeability coefficient of the grouting body can be measured; 4) By analyzing the water quality information of the grouting body leachate, the pollution effect of grouting on the groundwater environment and the interaction between the slurry and the geological body can be explored; 5) This method also provides a subsequent water chemical analysis sample of the grouting body leachate, thereby constituting an indoor system evaluation of grouting pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of a module of the grouting system of the present invention;

[0026] Figure 2 It is a schematic diagram of the modules of the infiltration system of the present invention;

[0027] Figure 3 It is a structural schematic diagram of the stepping motor propulsion device of the present invention;

[0028] Figure 4 It is a structural schematic diagram of the core model device of the present invention;

[0029] Figure 5 It is a structural schematic diagram of the grouting system of the present invention;

[0030] Figure 6 It is a schematic structural diagram of the filtration system of the present invention;

[0031] The serial numbers in the figure are: 1. Stepper motor, 2. Motion slider, 3. Piston cylinder liquid storage tank, 4. Slurry stop valve, 5. Slurry outlet interface, 6. Guide rail slide, 7. Motion sensor, 8. Base, 9. Transmission screw, 10. Limit switch, 11. Fastening screw, 12. Upper flange, 13. Plastic flange gasket, 14. Rubber diaphragm gasket, 15. Upper flange connection plate, 16. Barrel, 17. Casting filling layer, 18. Rubber diaphragm, 19. Filter, 20. Ball valve, 21. Liquid outlet pipe, 22. Support seat, 23. Rock block to be injected into hole and fracture, 24. Clamping ring, 25. Pressure transmitter, 26. Liquid return pipe, 27. Check valve, 28. Liquid injection pipe, 29. Core model device, 30. Stepper motor propulsion device, 31. Paperless recorder, 32. Slurry collection tank, 33. Slurry return tank, 34. Grouting system, 35. Constant pressure water supply control cabinet, 36. Leachate storage tank, 37. Digital flow rate meter, 38. Seepage system. DETAILED DESCRIPTION

[0032] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments:

[0033] Example 1

[0034] A test method for evaluating the long-term impact of chemical grouting in porous and fractured rock formations on groundwater quality comprises the following steps:

[0035] S1. Construction of model system:

[0036] The model system includes a grouting system 34 for grouting operations and an infiltration system 38 for infiltration operations. Figure 1 As shown, the grouting system consists of three modules: the first is the slurry injection module, which is the starting part of the entire grouting process and can provide slurry fluid with sufficient pressure to ensure that the slurry effectively penetrates the rock mass; the second is the injected module connected to the slurry injection module, whose main function is to simulate the infiltration process of slurry in porous and fractured rock mass; the third is the slurry collection module, which is used to collect the outflowing slurry. Specifically, the grouting system 34 includes a stepper motor propulsion device 30, a core model device 29, a paperless recorder 31, a slurry collection tank 32 and a slurry reflux tank 33.

[0037] like Figure 3As shown: the stepper motor propulsion device 30 includes a base 8, a guide rail slide 6 is provided on the base 8, a stepper motor 1 is provided on the guide rail slide 6, the output shaft of the stepper motor 1 is connected to the side wall of the base 8 through a transmission screw 9, a motion slider 2 is provided on the transmission screw 9, and the motion slider 2 is connected to the front end of the piston cylinder liquid storage tank 3 through a piston push rod, a slurry outlet interface 5 is provided at the end of the piston cylinder liquid storage tank 3, a slurry stop valve 4 is provided at the slurry outlet interface 5, a motion sensor 7 is provided between the base 8 and the guide rail slide 6, and a limit switch 10 is provided on the side wall of the base 8 away from the stepper motor 1;

[0038] like Figure 4 As shown: the core model device 29 includes a barrel body 16, the barrel body 16 is set on the support seat 22, the top of the barrel body 16 is provided with an upper flange 12, the upper flange 12 is connected to the upper flange connection plate 15 on the side wall of the barrel body 16 by a fastening screw 11, and a plastic flange gasket 13 and a rubber diaphragm gasket 14 are provided between the upper flange 12 and the upper flange connection plate 15. An injection pipe 28 is provided on the upper flange 12, and a return pipe 26 is provided on the side wall of the injection pipe 28. A check valve 27 is provided on the return pipe 26. The inner wall of the barrel body 16 is provided with a cast filling layer 17, and a hole and crack injected rock block 23 is provided in the cast filling layer 17. The hole and crack injected rock block 23, that is, the outer wall of the grouting body is provided with a rubber diaphragm 18, and the outer walls of the upper and lower ends of the rubber diaphragm 18 are provided with a tightening ring 24. The bottom end of the barrel body 16 is provided with a lower flange, and the lower flange is connected to the lower flange connection plate of the side wall of the barrel body 16 by a fastening screw 11. A plastic flange gasket 13 and a rubber diaphragm gasket 14 are provided between the lower flange and the lower flange connection plate. A through hole is opened on the lower flange, and a filter screen 19 is provided in the through hole. The through hole is connected to the liquid outlet pipe 21, and a ball valve switch 20 is provided on the liquid outlet pipe 21. The upper flange 12 and the lower flange are both provided with a pressure transmitter 25. The inlet of the injection pipe 28 is connected to the slurry outlet interface 5;

[0039] like Figure 5 As shown, the pressure transmitter 25 is connected to a paperless recorder 31, the return pipe 26 is connected to a slurry reflux tank 33, and the outlet of the discharge pipe 21 is connected to a slurry collection tank 32. The entire experimental system, utilizing a high-precision, high-torque stepper motor, screw-slide, piston-cylinder propulsion device, generates a high-pressure, stable slurry flow, allowing the slurry to fully penetrate and diffuse within the porous and fractured rock mass, ultimately achieving complete penetration of the injected rock mass and providing an experimental foundation for subsequent tests.

[0040] After the grouting is completed, the infiltration step is carried out, and the post-grouting infiltration system of the porous and fractured rock mass is used, such as Figure 2As shown: The infiltration system consists of three modules: the first is the constant pressure water supply control module, which is the starting part of the entire infiltration process and can provide infiltration water flow with sufficient and stable pressure for the infiltration of the rock mass after grouting, thereby ensuring the effective infiltration of groundwater into the grouting body; the second is the injected module connected to the constant pressure water supply module, whose main function is to simulate the infiltration process of groundwater in the porous and fractured rock mass after grouting; the third is the groundwater leachate collection module, which is used to collect the groundwater that has flowed out through the infiltration effect. Specifically, as Figure 6 As shown, the infiltration system 38 includes a core model device 29, a constant pressure water supply control cabinet 35, a leachate storage tank 36, and a digital flow rate flowmeter 37. The pressure transmitter 25 in the core model device 29 is connected to the constant pressure water supply control cabinet 35, the leachate storage tank 36 is connected to the outlet of the liquid outlet pipe 21, and the digital flow rate flowmeter 37 is installed on the liquid outlet pipe 21. The entire experimental system uses a high-precision, high-pressure servo motor negative feedback constant pressure water supply control cabinet to generate a high-pressure and stable water flow, allowing groundwater to fully infiltrate the grouting body.

[0041] S2. Pretreatment of test materials and filling of grouting model:

[0042] Before conducting grouting experiments, samples of porous and fractured rock blocks within the study area are selected based on the specific conditions to be studied. Key properties, such as the chemical composition and mineralogy, are tested, with the resulting data serving as preliminary baseline data for subsequent experiments. The porous and fractured rock blocks are then fully presaturated with water to simulate the water-rich, saturated environment found in actual formations. Based on the experimental plan's requirements, a blank control model is established as a control baseline. Except for the grouting variables, all other conditions remain the same as those in the experimental group. Simultaneously, several core model devices are set up simultaneously, following the same operating procedures, to facilitate the conduct of multiple parallel chemical infiltration grouting experiments.

[0043] Notably, the prefabricated porous and fractured rock blocks are tightly wrapped with a rubber diaphragm, and stirrups are used at the lower and upper ends of the blocks to ensure a tight seal around the sidewalls. Subsequently, the lower extension of the rubber diaphragm is clamped and secured using a lower flange and a plastic flange gasket. Subsequently, an expansive cementitious material is poured into the gap between the rock block and the inner sidewall of the model. During the pouring process, it is important to ensure that the cementitious material evenly and fully fills the gap to achieve a good sealing and securing effect. After the cementitious material has fully solidified, the upper portion of the rubber diaphragm is clamped and secured using the same method using an upper flange and a plastic flange gasket, ensuring that the rock block's lateral perimeter is completely and saturated with the cementitious material. This method restricts groundwater migration and infiltration to the rock block cross-section, effectively preventing the release of impurities during subsequent infiltration, which could occur due to contact between the infiltrating groundwater and the filling material, triggering hydration and hydrolysis reactions. Therefore, the interference of impurities on the water quality of the grouting body leachate was avoided, ensuring the accuracy and reliability of the water quality monitoring data during the experiment.

[0044] S3. Grout selection and closed grouting: Select the type of grout according to the research plan requirements, and perform closed grouting on the pores and fractures in the model.

[0045] Suitable slurries include, but are not limited to, lignin, phosphoric acid curing agent urea-formaldehyde resin, oxalic acid curing agent urea-formaldehyde resin, acrylates, epoxy resins, and polyurethanes.

[0046] Grouting implementation steps: After completing the model filling operation, follow Figure 5 After connecting all components of the grouting system, the rock saturation operation is immediately carried out. This involves using a stepper motor to propel the device until a steady flow of water flows out of the model's outlet pipe. After the saturation process is completed, the chemical slurry is pumped and stored within the piston cylinder of the propulsion device. In the initial grouting phase, the propulsion device is controlled to slowly push the slurry into a buffer chamber located above the rock block within the model. During this process, the slurry's pressure is used to displace any remaining water within the buffer chamber through a check valve, ensuring that only pure chemical slurry remains within the buffer chamber. Once the water has been completely displaced, the check valve is immediately closed and the grouting process begins. During grouting, pressure transmitters and paperless recorders are used to dynamically monitor and record pressure changes at the slurry inlet and outlet ports within the grouting model. The collected data will serve as a basis for subsequent analysis of the grouting effect and judgment of the rationality of the grouting process.

[0047] During grout injection, a stepper motor propulsion device is used as the grouting power device to ensure stable and accurate injection of the grout into the rock medium. During this process, the dynamic changes in grouting pressure are collected and recorded in real time through the coordinated use of pressure transmitters and paperless recorders.

[0048] The stopping conditions for the grouting operation are based on two points: first, when the internal pores of the rock block are completely penetrated by the slurry and the slurry flows steadily out of the outlet pipe installed at the bottom, it indicates that the rock block grouting has reached a saturated state and the grouting can be stopped; second, when the propulsion device reaches the maximum output torque of the stepper motor, that is, the slider of the propulsion device can no longer continue to push the piston cylinder, the grouting is stopped to prevent the equipment from being overloaded and damaged.

[0049] S4. Grouting penetration:

[0050] After the injected chemical slurry has fully solidified, an appropriate seepage velocity is selected to infiltrate the grouting model. Groundwater from the study area is used for infiltration. For the flow velocity parameters involved in the infiltration process, values ​​matching the average groundwater velocity in the study area are generally selected as the basic simulation conditions to reflect the prevailing groundwater seepage conditions in the area. However, considering the specific research objectives and diverse needs of different experimental schemes, flow velocity settings can be customized within a reasonable range.

[0051] Penetration implementation steps: Based on Figure 6 After assembling and connecting all components of the infiltration system using the connection method shown, the constant pressure water supply control cabinet is activated. The relevant control parameters, particularly the infiltration pressure, are set according to the pre-designed test plan to begin the infiltration process. During the infiltration process, a digital flowmeter is used to dynamically monitor the flow rate and velocity of water flowing through the grouting body in real time. The seeping groundwater leachate is stored in a leachate storage tank for subsequent sampling and analysis.

[0052] Regulation of seepage rate: After the chemical slurry solidifies, the permeability coefficient of the grouting body will tend to be stable. Therefore, under the action of constant infiltration pressure, the water flow rate and seepage flow rate of the grouting body will also remain relatively constant. Therefore, after the infiltration begins, the output water pressure of the constant pressure water supply control cabinet can be adjusted according to the stable water flow rate and seepage flow rate values ​​monitored by the digital flow and flow meter to achieve the preset seepage flow rate by adjusting the output water pressure of the constant pressure water supply control cabinet.

[0053] This constant-pressure water supply control cabinet transmits real-time water pressure data via a pressure transmitter connected to the grouting model, providing precise negative feedback to the internal servo motor for regulation, thereby achieving a constant output of infiltration water pressure. Its excellent long-term standby characteristics enable it to continuously and stably provide constant water pressure conditions to the grouting body over a long period of time, ensuring long-term, uninterrupted, and stable infiltration of the grouting body. This provides an experimental basis for in-depth research on the hydrochemical evolution of the grouting body under long-term infiltration conditions.

[0054] In addition, the system can also measure the permeability coefficient of the grouting body after stabilization. By setting the output water pressure and monitoring the permeability flow rate, the permeability coefficient can be determined according to Darcy's law.

[0055] S5. Analyze the water quality of the filtered water:

[0056] During the test, the water percolating from the grouting body is collected and subjected to comprehensive and special water quality analysis. Water quality testing and analysis indicators include but are not limited to general measurement indicators: K + , Ca 2+ 、Na + Mg 2+ 、CI - 、 OH - 、 F - 、 Br - 、 pH, total dissolved solids (TDS), electrical conductivity (EC), total hardness (TH), and redox potential (ORP). Organic indicators include total organic carbon (TOC), chemical oxygen demand (COD), free formaldehyde, methylene bisacrylamide (MBA), bisphenol A (BPA), and free isocyanate (TDI). Leachate is collected and analyzed at intervals starting with frequent and then sparse.

[0057] S6. Water chemical analysis and evaluation:

[0058] S6-1. Based on the measured leachate ion concentration, plot the Piper diagram and other diagrams to determine the hydrochemical type of the leachate. This allows analysis of the pattern of changes in the groundwater hydrochemical type caused by the grouting fluid. This allows identification of the negative effects of grouting contaminants on the overall hydrochemical characteristics of the regional groundwater at a macro level.

[0059] S6-2. Develop time-dependent evolution curves of water quality indicators and ion concentrations to analyze the impact patterns and changing trends of the grouting fluid on groundwater quality indicators. By fitting indicators that change significantly during monitoring, accurately determine the time required for the grouting contamination effect to change from significant to negligible. This allows for the identification of the inherent mechanisms of grouting contaminants affecting regional groundwater quality at a microscopic level and the assessment of the impact period of grouting on groundwater ion balance.

[0060] S6-3. Draw a Schoeller diagram to analyze the degree of disturbance to groundwater quality caused by the grouting project. By analyzing the fluctuation range of water quality indicators, the degree of normalization and degradation of groundwater quality in the area after grouting can be determined.

[0061] S6-4. Draw a correlation heat map to analyze the internal connections and interactions between various pollution factors in the grouting pollution process. This can be used to analyze the sources and mechanisms of grouting pollutants from the perspective of indicator correlation.

[0062] S6-5. Draw the PCA principal component map to analyze the dominant role of the grouting fluid in the groundwater pollution process, and then reveal the main mechanism of the slurry pollution process from the perspective of multivariate statistical dimensionality reduction.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A test method for evaluating the long-term effects of chemical grouting in porous and fractured rock formations on groundwater quality, characterized in that: The following steps are involved: S1. Construction of a model system: The model system includes a grouting system (34) for grouting operation and an infiltration system (38) for infiltration operation; S2. Pretreatment of test materials and filling of grouting models: Based on the specific working conditions to be studied, porous and fractured rock samples within the study area are selected and tested for their key properties. The obtained data serves as preliminary basic data for subsequent tests. The porous and fractured rock blocks are then fully pre-saturated with water to simulate the water-rich and saturated environment in actual formations. S3. Grout selection and closed grouting: Select the type of grout according to the research plan requirements and perform closed grouting on the pores and fractures in the model; S4. Grouting penetration: After the grouting liquid is fully solidified, select an appropriate seepage rate to penetrate the grouting model; S5. Analyze the water quality of the percolation water: During the test, collect the percolation water from the grouting body and conduct a comprehensive and special water quality analysis. S6. Hydrochemical analysis and evaluation: Based on the acquired water quality analysis data, analyze the extent of the impact of chemical grouting in porous and fractured rock formations on groundwater quality and its dynamic change effect over time; The grouting system (34) includes a stepper motor propulsion device (30), a core model device (29), a paperless recorder (31), a slurry collection tank (32) and a slurry return tank (33). The stepper motor propulsion device (30) comprises a base (8), a guide rail slide (6) is provided on the base (8), a stepper motor (1) is provided on the guide rail slide (6), an output shaft of the stepper motor (1) is connected to the side wall of the base (8) via a transmission screw (9), a motion slider (2) is provided on the transmission screw (9), the motion slider (2) is connected to the front end of the piston cylinder liquid storage tank (3) via a piston push rod, a slurry outlet interface (5) is provided at the end of the piston cylinder liquid storage tank (3), a slurry stop valve (4) is provided at the slurry outlet interface (5), a motion sensor (7) is provided between the base (8) and the guide rail slide (6), and a limit switch (10) is provided on the side wall of the base (8) away from the stepper motor (1); The core model device (29) includes a barrel (16), the barrel (16) is arranged on a support seat (22), the top of the barrel (16) is provided with an upper flange (12), the upper flange (12) is connected to the upper flange connection plate (15) of the side wall of the barrel (16) by a fastening screw (11), a plastic flange gasket (13) and a rubber diaphragm gasket (14) are provided between the upper flange (12) and the upper flange connection plate (15), an injection pipe (28) is provided on the upper flange (12), a return pipe (26) is provided on the side wall of the injection pipe (28), a check valve (27) is provided on the return pipe (26), the inner wall of the barrel (16) is provided with a cast filling layer (17), and a hole and crack injected rock block (23) is provided in the cast filling layer (17). The outer wall of the rock block (23) injected into the hole fissure is provided with a rubber diaphragm (18), and the outer walls of the upper and lower ends of the rubber diaphragm (18) are both provided with a clamping ring (24). The bottom end of the barrel body (16) is provided with a lower flange, and the lower flange is connected to the lower flange connection plate of the barrel body (16) side wall through a fastening screw (11). A plastic flange gasket (13) and a rubber diaphragm gasket (14) are provided between the lower flange and the lower flange connection plate. A through hole is opened on the lower flange, and a filter screen (19) is provided in the through hole. The through hole is connected to the liquid outlet pipe (21), and a ball valve switch (20) is provided on the liquid outlet pipe (21). The upper flange (12) and the lower flange are both provided with a pressure transmitter (25). The inlet of the injection pipe (28) is connected to the slurry outlet interface (5); The pressure transmitter (25) is connected to the paperless recorder (31), the return liquid pipe (26) is connected to the slurry reflux tank (33), and the outlet of the liquid outlet pipe (21) is connected to the slurry collection tank (32); The infiltration system (38) includes a core model device (29), a constant pressure water supply control cabinet (35), a leachate storage tank (36) and a digital flow rate flow meter (37). The pressure transmitter (25) in the core model device (29) is connected to the constant pressure water supply control cabinet (35), the leachate storage tank (36) is connected to the outlet of the liquid outlet pipe (21), and the digital flow rate flow meter (37) is arranged on the liquid outlet pipe (21).

2. The test method for evaluating the long-term impact of chemical grouting in porous and fractured rock formations on groundwater quality according to claim 1, characterized in that: The grouting operation can be stopped only when one of the following conditions is met: ① When the internal pores of the rock block are completely penetrated by the slurry and the slurry flows out steadily from the outlet pipe, it indicates that the rock block grouting has reached saturation and the grouting can be stopped; ② When the stepper motor propulsion device reaches the maximum output torque of the stepper motor, that is, when the slider in the stepper motor propulsion device can no longer continue to push the piston cylinder, the grouting is stopped to prevent the equipment from being overloaded and damaged.

3. The test method for evaluating the long-term impact of chemical grouting in porous and fractured rock formations on groundwater quality according to claim 1, characterized in that: The slurry in step S3 includes lignin, phosphoric acid curing agent urea-formaldehyde resin, oxalic acid curing agent urea-formaldehyde resin, acrylate, epoxy resin and polyurethane.

4. The test method for evaluating the long-term impact of chemical grouting in porous and fractured rock formations on groundwater quality according to claim 1, characterized in that: The water quality analysis indicators in step S5 include general measurement indicators and organic indicators. The general measurement indicators include K + , Ca 2+ 、Na + Mg 2+ 、CI - 、SO4 2- 、CO3 2- 、HCO3 - OH - PO4 3- 、F - 、NO2 - Br - 、NO3 - As well as pH, total dissolved solids TDS, electrical conductivity EC, total hardness TH and oxidation-reduction potential ORP; the organic indicators include total organic carbon TOC, chemical oxygen demand COD, free formaldehyde, methylene bisacrylamide, bisphenol A and free isocyanate; the collected leachate is analyzed for water quality according to the principle of setting time intervals from dense to sparse.

5. The test method for evaluating the long-term impact of chemical grouting in porous and fractured rock formations on groundwater quality according to claim 1, characterized in that: The water chemical analysis and evaluation in step S6 includes the following steps: S6-1. Draw a map based on the measured leachate ion concentration to determine the leachate hydrochemical type. This will allow analysis of the pattern of changes in the groundwater hydrochemical type caused by the grouting fluid and the identification of the negative effects of grouting contaminants on the overall hydrochemical characteristics of the regional groundwater at a macro level. S6-2. Develop time-dependent evolution curves of water quality indicators and ion concentrations to analyze the impact patterns and changing trends of the grouting fluid on groundwater quality indicators. By fitting indicators that change significantly during monitoring, accurately determine the time required for the grouting contamination effect to change from significant to negligible. This allows for the identification of the underlying mechanisms of grouting contaminants affecting regional groundwater quality at a microscopic level, and the assessment of the impact period of grouting on groundwater ion balance. S6-3. Draw a Schoeller diagram to analyze the degree of disturbance to groundwater quality caused by the grouting project. By analyzing the fluctuation range of water quality indicators, the degree of normalization and degradation of groundwater quality in the area after grouting can be determined. S6-4. Draw a correlation heat map to analyze the internal connections and interactions between various pollution factors in the grouting pollution process, and analyze the sources and mechanisms of grouting pollutants from the perspective of indicator correlation; S6-5. Draw a PCA principal component map to analyze the dominant role of the grouting fluid in the groundwater pollution process and reveal the main mechanism of action in the slurry pollution process from the perspective of multivariate statistical dimensionality reduction.

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