Test method for evaluating long-term influence of chemical grouting of hole fractured rock stratum on water quality of underground water

Abstract

The invention discloses a test method for evaluating the long-term influence of chemical grouting of a hole fractured rock stratum on the water quality of underground water. The test method comprises the following steps: building a model system, pretreating a test material, filling a grouting model, selecting slurry, carrying out closed grouting, permeating a grouting body, and carrying out water quality analysis and water chemical analysis and evaluation on percolated water. The method disclosed by the invention has the replaceability of the grouting material and the adjustability of the seepage flow velocity; the long-term real-time dynamic monitoring and recording of the seepage velocity can be realized through a digital display flow rate and flow velocity meter, and the seepage coefficient of the grouting body is measured; the pollution effect of grouting on the groundwater environment and the interaction between slurry and a geologic body can be explored by analyzing the water quality information of the grouting percolate; the invention further provides a subsequent water chemical analysis sample plate of the grouting percolate, so that indoor system evaluation on grouting pollution is formed.

Description

Technical Field

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

[0002] Grouting is a common engineering technology for mine management. It is crucial for shaft and tunnel reinforcement and leakage prevention, but it also poses a risk of pollution to the regional groundwater environment. During grouting, a large amount of slurry will change the pH value, total dissolved solids and ion concentration of groundwater, affecting the water quality. Therefore, it is necessary to conduct long-term model tests on the impact of specific grouting materials on groundwater quality, study their pollution characteristics and laws, and evaluate the degree of pollution and degradation cycle.

[0003] At present, existing research on the impact of grouting on groundwater environment mainly collects water samples from underground drainage holes and excavation water points, and then conducts relevant water quality chemical analysis to explore the intrinsic relationship between grouting activities and groundwater environmental changes. This method has a certain degree of randomness, is greatly restricted by the actual site conditions and engineering plans, and cannot rule out the excessive interference of local abnormal geochemical characteristics of rock and soil on water quality. The sampling cost and cycle are long, time-consuming and labor-intensive, and not flexible enough. Existing indoor research mainly relies on water-rock interaction shake bottle batch experiments, which cannot provide dynamic groundwater dynamics and cannot achieve groundwater infiltration.

[0004] In view of this, it is urgent to expand the current research paradigm. Therefore, a new post-grouting percolation model system of geological bodies that is suitable for a variety of chemical grouting materials, can simulate groundwater flow rates within a specific range, and has cyclic and sustainable characteristics is constructed, thereby forming a research and evaluation method system for grouting pollution of groundwater environment, so as to more accurately evaluate the potential impact of grouting activities on the groundwater environment and its mechanism 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 a model system: The model system includes a grouting system for grouting operation and an infiltration system for infiltration operation;

[0008] S2. Pretreatment of test materials and filling of grouting model: According to the specific working conditions to be studied, select porous and fractured rock samples in the study area, and test the key properties of the porous and fractured rock samples. The obtained data will be used as the preliminary basic data for subsequent tests, and then the porous and fractured rock will be fully pre-saturated with water to simulate the water-rich and saturated environment in the actual formation;

[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 body 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 filtered water: During the test, collect the water filtered out by the grouting body and conduct a comprehensive and special analysis of its water quality;

[0012] S6. Hydrochemical analysis and evaluation: Based on the water quality analysis data obtained, 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 arranged on a support seat, an upper flange is provided on the top of the barrel body, the upper flange is connected to the upper flange connection plate of the barrel body side wall by fastening screws, a plastic flange pad and a rubber diaphragm pad are provided between the upper flange 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 clamping 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, and the lower A plastic flange gasket and a rubber diaphragm gasket are arranged between the flange and the lower flange connection plate. A through hole is opened on the lower flange, a filter is arranged in the through hole, the through hole is connected to the liquid outlet pipe, a ball valve switch is arranged on the liquid outlet pipe, pressure transmitters are arranged on 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 grouting of the rock block 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, 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 comprises lignin, phosphoric acid curing agent urea-formaldehyde resin, oxalic acid curing agent urea-formaldehyde resin, acrylate, epoxy resin and polyurethane.

[0017] Preferably, the water quality analysis indicators 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 redox potential ORP; the organic indicators include total organic carbon TOC, chemical oxygen demand COD, free formaldehyde, methylene bisacrylamide, bisphenol A and free isocyanate; the water quality of the collected leachate is analyzed according to the principle of setting the time interval 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 hydrochemical type of the leachate, analyze the change pattern of the grouting fluid on the hydrochemical type of groundwater, and identify the negative effects of grouting pollutants on the overall hydrochemical characteristics of regional groundwater from a macro perspective;

[0020] S6-2. Draw the time evolution curves of water quality indicators and ion concentrations to analyze the influence and change trend of the grouting fluid on groundwater quality indicators. By fitting the indicators that have changed significantly during monitoring, accurately determine the time required for the grouting pollution effect to change from significant to negligible, identify the internal mechanism of grouting pollutants on regional groundwater quality changes at the microscopic level, and evaluate the impact period of grouting on groundwater ion balance;

[0021] S6-3. Draw Schoeller diagrams to analyze the degree of disturbance of groundwater quality caused by grouting. 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 connection and interaction between various pollution factors in the grouting pollution process, and analyze the formation source and mechanism of grouting pollutants from the perspective of indicator correlation;

[0023] S6-5. Draw the PCA principal component map to analyze the dominant role of the grouting liquid 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, so as to realize continuous circulation, 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) The infiltration flow rate can be monitored and recorded in real time in a long term through the 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 a grouting system of the present invention;

[0026] Figure 2 is a schematic diagram of a module of an 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 diagram of the structure 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. pouring filling layer, 18. rubber diaphragm, 19. filter screen, 20. ball valve, 21. Liquid outlet pipe, 22. Support seat, 23. Rock block to be injected into hole and fissure, 24. Tightening 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 reflux tank, 34. Grouting system, 35. Constant pressure water supply control cabinet, 36. Leachate storage tank, 37. Digital flow rate and velocity meter, 38. Seepage system. DETAILED DESCRIPTION

[0032] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments:

[0033] Example 1

[0034] A test method for evaluating the long-term effect 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 into 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, 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 arranged on a 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 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 arranged between the upper flange 12 and the upper flange connection plate 15, an injection pipe 28 is arranged on the upper flange 12, a return pipe 26 is arranged on the side wall of the injection pipe 28, a check valve 27 is arranged on the return pipe 26, a casting filling layer 17 is arranged on the inner side wall of the barrel body 16, a hole and crack injected rock block 23 is arranged in the casting filling layer 17, and the hole and crack injected rock block 23, that is, a rubber diaphragm 18 is provided on the outer wall of the grouting body, and a clamping ring 24 is provided on the outer wall of the upper and lower ends of the rubber diaphragm 18, and a lower flange is provided at the bottom end of the barrel body 16, 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, and a plastic flange gasket 13 and a rubber diaphragm gasket 14 are provided between the lower flange and the lower flange connection plate, and a through hole is opened on the lower flange, and a filter screen 19 is provided in the through hole, and 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, and a pressure transmitter 25 is provided on the upper flange 12 and the lower flange, and 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 the paperless recorder 31, the return pipe 26 is connected to the slurry reflux tank 33, and the outlet of the outlet pipe 21 is connected to the slurry collection tank 32. The entire experimental system, with the help of a high-precision and high-torque stepper motor screw slide piston cylinder propulsion device, can form a high-pressure and stable slurry flow, so that the slurry can fully penetrate and diffuse in the porous and fractured rock mass until it achieves complete penetration of the injected rock mass, thereby providing an experimental basis for subsequent tests.

[0040] After the grouting is completed, the infiltration step is carried out. At this time, the post-grouting infiltration system of 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 flows out after the infiltration. Specifically, Figure 6 As shown: the infiltration system 38 includes a core model device 29, a constant pressure water supply control cabinet 35, a percolate storage tank 36 and a digital flow velocity meter 37. The pressure transmitter 25 in the core model device 29 is connected to the constant pressure water supply control cabinet 35, the percolate storage tank 36 is connected to the outlet of the liquid outlet pipe 21, and the digital flow velocity meter 37 is arranged on the liquid outlet pipe 21. The entire experimental system can form a high-pressure and stable water flow with the help of a high-precision and high-pressure servo motor negative feedback constant pressure water supply control cabinet, so that groundwater can be fully infiltrated in the grouting body.

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

[0042] Before conducting the grouting experiment, it is necessary to select samples of porous and fissured rock blocks in the study area according to the specific working conditions to be studied, and test the key properties of the rock blocks such as chemical composition and mineral composition, and use the obtained data as the preliminary basic data for subsequent experiments. Then the porous and fissured rock blocks are fully pre-saturated with water to simulate the water-rich and saturated environment in the actual formation. According to the requirements of the experimental plan, a blank control model is set as the experimental control benchmark. Except for the grouting variables, the other conditions are consistent with the experimental group; at the same time, according to the same operating process, a number of core model devices are set up synchronously to carry out multiple groups of multi-type chemical penetration grouting parallel experiments.

[0043] It is worth noting that the side wall of the prefabricated porous and fissure rock block is tightly wrapped with a rubber diaphragm, and the lower and upper ends of the rock block are ring-tied with stirrups to ensure the sealing of the side wall of the rock block structure. Then, the lower extension of the rubber diaphragm is clamped and fixed with the help of the cooperation between the lower flange and the plastic flange gasket. Subsequently, the expansion cementitious material is poured into the gap between the rock block and the inner wall of the model. During the pouring process, it is necessary to ensure that the cementitious material can evenly and fully fill the gap to achieve a good sealing and fixing effect. After the filled expansion cementitious material is fully cured, the upper part of the rubber diaphragm is clamped and fixed with the upper flange and the plastic flange gasket in the same operation mode, so that the side of the rock block can be completely and saturatedly filled with the expansion cementitious material. This treatment method allows groundwater to migrate and penetrate only through the rock block section, effectively avoiding the phenomenon that the infiltrating groundwater may contact the filling material and then trigger hydration and hydrolysis reactions, resulting in the release of impurities during subsequent infiltration. 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 Connect all the components of the grouting system, and then start the rock saturation operation, that is, use the stepper motor to propel the device to inject water until a stable water flow flows out of the outlet pipe of the model. After the saturation process is completed, the chemical slurry is sucked and stored in the piston cylinder of the propulsion device. In the initial stage of grouting, the propulsion device is controlled to slowly push the slurry into the buffer bin set on the upper part of the rock block in the model. During this process, the pressure of the slurry is used to displace all the residual water in the buffer bin through the check valve to ensure that only pure chemical slurry remains in the buffer bin. When the water is completely displaced, immediately close the check valve and start the grouting process. During grouting, the pressure transmitter and paperless recorder are used to monitor and record the pressure changes of the slurry inlet and outlet ports in the grouting model in real time. The collected data will serve as the basis for subsequent analysis of the grouting effect and judgment of the rationality of the grouting process.

[0047] When injecting grout, the stepper motor propulsion device is used as the grouting power equipment to ensure that the grout can be stably and accurately injected into the rock medium. During this period, the dynamic changes of grouting pressure are collected and recorded in real time by using pressure transmitters and paperless recorders.

[0048] The stop 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 out steadily from the outlet pipe set at the bottom, it indicates that the grouting of the rock block 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. Grout penetration:

[0050] After the injected chemical slurry is fully solidified, an appropriate seepage velocity is selected to infiltrate the grouting body model. The grouting body uses groundwater from the study area for infiltration. For the water flow velocity parameter setting involved in the infiltration process, in general, a value matching the average groundwater flow velocity in the study area is selected as the basic simulation condition to reflect the general state of groundwater seepage in the area. However, considering the specific research purposes and diverse needs of different test schemes, the flow velocity can also be customized within a reasonable range.

[0051] Penetration implementation steps: Based on Figure 6 After the assembly and connection of the various components of the infiltration system are completed, the constant pressure water supply control cabinet is started, and the relevant control parameters, especially the infiltration pressure, are set according to the pre-designed test plan to start the infiltration process. During the infiltration process, a digital flow and velocity meter is used to monitor the water flow and velocity of the grouting body in real time and dynamically. The seepage groundwater leachate is stored in the 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 to achieve the preset seepage flow rate based on the stable water flow rate and seepage flow rate values ​​monitored by the digital flow and flow rate meter.

[0053] The constant pressure water supply control cabinet transmits water pressure data in real time through the pressure transmitter connected to the grouting model to send precise negative feedback adjustment to the internal servo motor to achieve constant output of infiltration water pressure. It also has excellent long-term standby characteristics, and can continuously and stably provide constant water pressure conditions for the grouting body over a long time span, ensuring long-term, uninterrupted and stable continuous infiltration of the grouting body, thereby providing an experimental basis for in-depth exploration of the water chemical evolution law 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 measured 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 water quality analysis, special analysis and other tests. 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, conductivity EC, total hardness TH, redox potential ORP. Organic indicators: total organic carbon TOC, chemical oxygen demand COD, free formaldehyde, methylene bisacrylamide (MBA), bisphenol A (BPA), free isocyanate (TDI). The collected leachate is analyzed for water quality according to the principle of setting the time interval from dense to sparse.

[0057] S6. Water chemical analysis and evaluation:

[0058] S6-1. Draw Piper diagrams and other diagrams based on the measured leachate ion concentration to determine the hydrochemical type of the leachate, so as to analyze the change pattern of the grouting fluid on the hydrochemical type of groundwater, thereby identifying the negative effects of grouting pollutants on the overall hydrochemical characteristics of regional groundwater at a macro level;

[0059] S6-2. Draw the time evolution curves of water quality indicators and ion concentrations to analyze the influence and change trend of the grouting fluid on groundwater quality indicators. By fitting the indicators that have changed significantly during monitoring, accurately determine the time required for the grouting pollution effect to change from significant to negligible. This can identify the internal mechanism of grouting pollutants on regional groundwater quality changes at the microscopic level and evaluate the impact period of grouting on groundwater ion balance.

[0060] S6-3. Draw Schoeller diagrams to analyze the degree of disturbance of groundwater quality caused by grouting. 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 connection and interaction between various pollution factors in the grouting pollution process, so as to analyze the formation source and mechanism 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 liquid in the groundwater pollution process, and then reveal the main mechanism of action in 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 protection scope of the present invention.

Claims

1. A test method for evaluating the long-term effect of chemical grouting in porous and fractured rock formations on groundwater quality, characterized in that: The following steps are involved: S1. Building 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 model: According to the specific working conditions to be studied, select porous and fractured rock samples in the study area, and test the key properties of the porous and fractured rock samples. The obtained data will be used as the preliminary basic data for subsequent tests, and then the porous and fractured rock will be fully pre-saturated with water to simulate the water-rich and saturated environment in the actual formation; 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 body 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 filtered water: During the test, collect the water filtered out by the grouting body and conduct a comprehensive and special analysis of its water quality; S6. Hydrochemical analysis and evaluation: Based on the water quality analysis data obtained, 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.

2. A 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 system (34) comprises a stepping 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) through a transmission screw (9), a moving slider (2) is provided on the transmission screw (9), the moving 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); The core model device (29) comprises a barrel (16), wherein the barrel (16) is arranged on a support seat (22), an upper flange (12) is arranged at the top of the barrel (16), the upper flange (12) is connected to an upper flange connection plate (15) on the side wall of the barrel (16) by means of a fastening screw (11), a plastic flange gasket (13) and a rubber diaphragm gasket (14) are arranged between the upper flange (12) and the upper flange connection plate (15), an injection pipe (28) is arranged on the upper flange (12), a return pipe (26) is arranged on the side wall of the injection pipe (28), a check valve (27) is arranged on the return pipe (26), a casting filling layer (17) is arranged on the inner side wall of the barrel (16), a hole and fissure injected rock block (23) is arranged in the casting filling layer (17), A rubber diaphragm (18) is provided on the outer wall of the rock block (23) to be injected into the hole and fissure, and a clamping ring (24) is provided on the outer wall of the upper and lower ends of the rubber diaphragm (18). A lower flange is provided at the bottom end of the barrel body (16), and the lower flange is connected to the lower flange connection plate of the side wall of the barrel body (16) 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 a liquid outlet pipe (21), and a ball valve switch (20) is provided on the liquid outlet pipe (21). Pressure transmitters (25) are provided on the upper flange (12) and the lower flange, and the inlet of the injection pipe (28) is connected to the slurry outlet interface (5); The pressure transmitter (25) is connected to a paperless recorder (31), the liquid return pipe (26) is connected to a slurry reflux tank (33), and the outlet of the liquid outlet pipe (21) is connected to a slurry collection tank (32).

3. A test method for evaluating the long-term impact of chemical grouting in porous and fractured rock formations on groundwater quality according to claim 2, characterized in that: To stop the grouting operation, one of the following conditions must be 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 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.

4. A test method for evaluating the long-term impact of chemical grouting in porous and fractured rock formations on groundwater quality according to claim 2, characterized in that: The infiltration system (38) comprises 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).

5. The test method for evaluating the long-term effect 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.

6. The test method for evaluating the long-term effect 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 - , OH - , F - , Br - , As well as pH, total dissolved solids TDS, electrical conductivity EC, total hardness TH and redox potential ORP; the organic indicators include total organic carbon TOC, chemical oxygen demand COD, free formaldehyde, methylene bisacrylamide, bisphenol A and free isocyanate; the water quality of the collected leachate is analyzed according to the principle of setting the time interval from dense to sparse.

7. The test method for evaluating the long-term effect 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 hydrochemical type of the leachate, analyze the change pattern of the grouting fluid on the hydrochemical type of groundwater, and identify the negative effects of grouting pollutants on the overall hydrochemical characteristics of regional groundwater from a macro perspective; S6-2. Draw the time evolution curves of water quality indicators and ion concentrations to analyze the influence and change trend of the grouting fluid on groundwater quality indicators. By fitting the indicators that have changed significantly during monitoring, accurately determine the time required for the grouting pollution effect to change from significant to negligible, identify the internal mechanism of grouting pollutants on regional groundwater quality changes at the microscopic level, and evaluate the impact period of grouting on groundwater ion balance; S6-3. Draw Schoeller diagrams to analyze the degree of disturbance of groundwater quality caused by grouting. 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 connection and interaction between various pollution factors in the grouting pollution process, and analyze the formation source and mechanism of grouting pollutants from the perspective of indicator correlation; S6-5. Draw the PCA principal component map to analyze the dominant role of the grouting liquid 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.

Images