Method for evaluating field groutability of fault fracture zone in water-rich environment

Abstract

The invention discloses a method for evaluating field groutability of a fault fracture zone in a water-rich environment, and belongs to the field of unfavorable geological treatment of engineering. The method aims to solve the problems of index dispersion, data lag and difficulty in real-time visualization of the existing evaluation means. The method is technically characterized by comprising the following steps: acquiring initial conductivity of underground water on site; injecting saturated salt water into the water injection holes at a constant speed and measuring the real-time conductivity of a plurality of circles of water outlet holes around; calculating an initial groutability index of each water outlet hole based on the initial conductivity and the real-time conductivity; correcting the initial index according to the orientation of the water outlet hole relative to the gravity and the water flow direction to obtain a corrected groutability index; and generating a groutability spatial distribution thermodynamic diagram based on the corrected indexes of the water outlet holes at the same moment. The grouting stone body can be further scanned through CT, the setting rate is calculated, and grout matching correction is conducted on the groutability index. The method is mainly used for grouting reinforcement construction guidance in water-rich environments such as tunnels and underground pipelines.

Description

Technical Field

[0001] This invention belongs to the field of engineering adverse geological treatment technology, and in particular relates to a method for on-site injectionability assessment of fault fracture zones in water-rich environments. Background Technology

[0002] Water-rich fault fracture zones are complex geological bodies most prone to water inrush and mudslide disasters in underground engineering. They are characterized by abundant internal water resources, strong pore connectivity, high permeability, and often high mud content, significantly limiting the feasibility of grouting and other injection operations. Traditional field exploration and evaluation methods mainly rely on geophysical exploration, drilling, and advanced prediction technologies. Geophysical methods such as direct current method, induced polarization method, and seismic wave method can determine the distribution and water pressure characteristics of water-rich fracture zones; drilling provides direct parameters such as core samples, porosity, and water content; while advanced prediction technologies such as TSP and infrared water detection can identify fault fracture zones and their water-rich state in advance, providing a basis for subsequent construction. The evaluation of grouting effectiveness typically uses indicators such as grouting pressure, flow rate, and grout injection volume, and is verified through post-testing methods such as inspection holes, water pressure tests, and PQ curves. However, these methods still have significant shortcomings in practical field applications. First, evaluation indicators are often scattered, focusing only on single parameters such as grouting pressure or permeability coefficient, making it difficult to systematically assess the overall injectability of water-rich fault fracture zones. Second, geophysical and drilling results are mostly obtained before construction, lacking real-time updating capabilities, making it difficult to dynamically adjust grouting schemes according to actual geological conditions. Third, the key impact of clay content on grout permeability has not been fully quantified, and the weighting of clay in existing models lacks sufficient experimental support, affecting the accuracy of the assessment.

[0003] Furthermore, existing technologies for monitoring grouting effectiveness also have significant limitations. For example, seismic methods based on surface waves, refracted waves, or reflected waves respond weakly to small, thin-layered pores and fractures, especially under hard overburden layers where wave energy is strongly damped, making it difficult to capture subtle wave velocity changes within the grout body, resulting in limited detection depth and low resolution. While electromagnetic methods can effectively distinguish the distribution of pores and fractures in different layers, they are subject to stringent requirements regarding borehole spacing and water filling conditions, often making them difficult to implement in large-scale, rapid detection applications. Overall, existing monitoring methods suffer from low accuracy and operational difficulties, failing to meet the urgent need for real-time, visual monitoring of grouting effectiveness in the field. Due to these technological gaps, experimental methods for rapidly acquiring, comprehensively analyzing, and visually presenting the injectability of fault fracture zones in the field have been scarce, posing practical challenges to the scientific formulation and dynamic optimization of grouting reinforcement schemes in water-rich environments. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a method for assessing the injectability of fault fracture zones in a water-rich environment. Through on-site resistivity calibration and dynamic water injection tests, the method enables real-time monitoring and dynamic visualization assessment of the injectability of fault fracture zones, allowing the grouting scheme to be adjusted based on real-time data.

[0005] To achieve the above objectives, this invention provides a method for assessing the injectability of fault fracture zones in water-rich environments, comprising: The initial electrical conductivity of groundwater was obtained in the fault fracture zone at the site; A fluid of a set concentration was injected into the injection hole of the fault fracture zone at a constant rate, while the conductivity of multiple outlet holes arranged around the injection hole was measured during the injection process. Based on the initial conductivity and the real-time conductivity of each outlet hole, the preliminary injectability index of each outlet hole location is calculated. Based on the orientation of each outlet relative to the direction of gravity and the direction of groundwater flow, the preliminary injectability index is corrected to obtain the corrected injectability index. Based on the corrected injectability index of all water outlets at the same time, a spatial distribution map of injectability of the fault fracture zone is generated.

[0006] Optionally, obtaining the initial electrical conductivity of groundwater includes: Groundwater drawn from the fault fracture zone is introduced into a measuring container with fixed geometric dimensions; Measure the resistance and temperature of the groundwater inside the container; The initial conductivity is determined based on the geometric dimensions of the measuring container, the resistance, and the temperature-corrected conductivity.

[0007] Optionally, the injected fluid of a set concentration is saturated brine, the concentration of which is determined based on the measured temperature of the groundwater.

[0008] Optionally, multiple water outlets arranged around the water injection hole are distributed in multiple concentric rings with the water injection hole as the center, and the number of water outlets on each ring increases with the radius of the ring.

[0009] Optionally, the process of calculating the preliminary injectability index of each outlet location is based on the following relationship: the ratio of the real-time conductivity of each outlet to the initial conductivity is used as the preliminary injectability index of the outlet location.

[0010] Optionally, revising the preliminary injectability index includes: A first adjustment coefficient related to the direction of gravity is introduced, which is determined based on the angle between the orientation of each water outlet and the direction of gravity. A second adjustment coefficient related to the direction of groundwater flow is introduced, which is determined based on the angle between the orientation of each outlet and the direction of groundwater flow. The modified injectability index is obtained by multiplying the preliminary injectability index, the first adjustment coefficient, and the second adjustment coefficient.

[0011] Optionally, the method further includes performing slurry matching correction on the modified injectability index, including: The grout to be evaluated is injected into the injection hole to form a grouting stone body; Images of different cross-sections of the grouting stone body were obtained, and the solidification rate of each cross-section was calculated; Based on the aforementioned settling rate, the revised injectability index is further revised.

[0012] Optionally, the process of acquiring images of different cross sections of the grouting stone body is achieved through CT scanning; the process of calculating the solidity rate of each cross section is achieved by using image processing algorithms to identify the pore area in the cross section image and calculate the ratio of the pore area to the total cross section area.

[0013] An electronic device, the electronic device comprising: a processor and a memory storing computer program instructions; When the processor executes the computer program instructions, it implements the method for assessing the on-site injectability of fault fracture zones in a water-rich environment.

[0014] A computer storage medium storing computer program instructions, which, when executed by a processor, implement the method for assessing the in-situ injectability of fault fracture zones in a water-rich environment.

[0015] Technical advantages of this invention: This invention discloses a method for assessing the injectability of fault fracture zones in water-rich environments, effectively overcoming the shortcomings of existing technologies such as scattered evaluation indicators, data lag, and insufficient monitoring accuracy. Through on-site resistivity calibration and dynamic water injection tests, real-time monitoring and dynamic visualization assessment of the injectability of fault fracture zones are achieved, allowing grouting schemes to be adjusted based on real-time data. By introducing gravity and water flow direction correction coefficients and post-grouting CT compaction rate correction, the method systematically integrates the influence of multiple factors, including formation characteristics, grout properties, and groundwater environment, significantly improving the systematicness and accuracy of the assessment. This method is simple to operate, highly adaptable to field conditions, and can intuitively generate a spatial distribution heat map of injectability, providing a direct and reliable technical basis for grout selection and process parameter optimization in water-rich environments. Attached Figure Description

[0016] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a flowchart illustrating the method for measuring the electrical conductivity of groundwater at fault fracture zones in an on-site setting, as described in an embodiment of the present invention. Figure 2 This is a schematic diagram of the structure of the method for on-site measurement of liquid conductivity according to an embodiment of the present invention; Figure 3 This is a schematic diagram showing the relative positions and included angles of the water inlet hole, water outlet hole, gravity direction, and water flow direction in an embodiment of the present invention; Figure 4 This is a schematic diagram of the process for correcting the injectability of fault fracture zones considering water flow and gravity factors in an embodiment of the present invention. Figure 5 This is a schematic diagram showing the distribution of pores, fissures, skeleton, and filling material in a slice of grouting stone body according to an embodiment of the present invention. Figure 6 This is a flowchart illustrating a method for assessing the injectability of fault fracture zones in a water-rich environment, according to an embodiment of the present invention. Detailed Implementation

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0018] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0019] Existing research often uses transparent experimental devices indoors for grouting visualization studies. However, for field grouting, there are limited means to effectively visualize the injectability of fault fracture zones. Typically, monitoring methods such as seismomagnetism are used to invert the distribution of pores and fractures in the fault fracture zone. However, from a field application perspective, seismic methods such as surface waves, refracted waves, or reflected waves have weak responses to small, thin-layered pores and fractures, especially under hard overburden layers, where wave energy is strongly damped, making it difficult to capture subtle wave velocity changes in the grout body. This results in limited detection depth and low resolution. While electromagnetic methods can distinguish the distribution of pores and fractures in different layers relatively well, they have stringent requirements for field conditions such as pore spacing and water filling within the pores, and are often difficult to implement for large-scale rapid detection. Therefore, existing monitoring methods suffer from disadvantages such as low accuracy and difficulty in operation, which are detrimental to monitoring the effectiveness of field grouting. Based on this field monitoring requirement, a field experimental method for determining the injectability of fault fracture zones is proposed.

[0020] like Figure 6As shown in this embodiment, a method for assessing the injectability of fault fracture zones in a water-rich environment is provided, including: The initial electrical conductivity of groundwater was obtained in the fault fracture zone at the site; A fluid of a set concentration was injected into the injection hole of the fault fracture zone at a constant rate, while the conductivity of multiple outlet holes arranged around the injection hole was measured during the injection process. Based on the initial conductivity and the real-time conductivity of each outlet hole, the preliminary injectability index of each outlet hole location is calculated. Based on the orientation of each outlet relative to the direction of gravity and the direction of groundwater flow, the preliminary injectability index is corrected to obtain the corrected injectability index. Based on the corrected injectability index of all water outlets at the same time, a spatial distribution map of injectability of the fault fracture zone is generated.

[0021] Furthermore, obtaining the initial electrical conductivity of groundwater includes: Groundwater drawn from the fault fracture zone is introduced into a measuring container with fixed geometric dimensions; Measure the resistance and temperature of the groundwater inside the container; The initial conductivity is determined based on the geometric dimensions of the measuring container, the resistance, and the temperature-corrected conductivity.

[0022] Specifically, the implementation process of this embodiment includes: The reciprocal relationship between resistivity and conductivity: (1); Among them, resistivity It is an inherent property of the material itself that hinders the flow of electric current; conductivity. That is its opposite property.

[0023] For a segment of length L Cross-sectional area is A Saltwater conductor, its resistance for: (2); The effect of temperature on conductivity is as follows: (3); In the formula, To account for the temperature effect on conductivity, The electrical conductivity of the salt water at a temperature of 25°C. ; Based on the above derivation, conductivity Represented as: (4).

[0024] Based on this formula, the method for measuring the electrical conductivity of groundwater at the fault fracture zone in the field can be obtained as follows: Figure 1 As shown: S1: Use advanced drilling equipment to drill to the fault fracture zone and install a water diversion pipeline to the work site; S2: Water is drawn from the water pipe and placed in a specially designed container with a radius of [missing information]. r , length is l A cylinder; S3: Connect wires to both ends of the cylinder to a multimeter to measure the resistivity of groundwater in the fault fracture zone, and use a thermometer to measure the temperature of the groundwater. S4: Substitute the data into equation (4) to obtain the initial conductivity of groundwater. .

[0025] Furthermore, the injected fluid is saturated brine of a set concentration, the concentration of which is determined based on the measured temperature of the groundwater.

[0026] Furthermore, the multiple water outlets arranged around the water injection hole are distributed in multiple concentric rings with the water injection hole as the center, and the number of water outlets on each ring increases as the radius of the ring increases.

[0027] Furthermore, the process of calculating the preliminary injectability index of each outlet location is based on the following relationship: the ratio of the real-time conductivity of each outlet to the initial conductivity is used as the preliminary injectability index of the outlet location.

[0028] Specifically, the implementation process of this embodiment includes: like Figures 2-4 As shown, based on field water injection tests, a method of injecting a certain amount of saturated brine in the field is proposed to visualize the injectability at different locations. Due to the influence of gravity and groundwater flow, fluids such as slurry / salt water are more likely to migrate in the direction of groundwater flow and gravity, thereby correcting the injectability at different locations and reducing the influence of water flow and gravity on the injectability assessment of fault fracture zones.

[0029] S1: Based on the groundwater temperature obtained from the field test, and by consulting the brine saturation concentration at different temperatures, brine of that concentration is prepared on-site; S2: Drill a water injection hole using a drilling rig and install a water injection pipe for injecting brine; S3: Drill 3 to 5 rings of holes around the water injection hole as water outlet holes, with the number of holes gradually increasing in each ring, and install water outlet pipes, control valves, test chambers and other components. S4: Close all outlet valves, inject brine at a constant speed using a grouting machine, and open all outlet valves after 1 minute. Thereafter, use a multimeter to test the resistivity of all outlets every minute, and calculate the conductivity of outlets at different locations using equation (3). (n Indicates the first n One water outlet, t represent t (Data measured in minutes) S5: Through initial conductivity and conductivity after water injection Initial injectability indices were obtained for different outlet locations. for: (5).

[0030] Furthermore, the modification of the preliminary injectability index includes: A first adjustment coefficient related to the direction of gravity is introduced, which is determined based on the angle between the orientation of each water outlet and the direction of gravity. A second adjustment coefficient related to the direction of groundwater flow is introduced, which is determined based on the angle between the orientation of each outlet and the direction of groundwater flow. The modified injectability index is obtained by multiplying the preliminary injectability index, the first adjustment coefficient, and the second adjustment coefficient.

[0031] Specifically, the implementation process of this embodiment includes: S6: Introduces gravity and water flow direction adjustment coefficients , Their values ​​are as follows: (6); (7); Its value range is all In the formula, e is the natural constant, when hour, , At this time, the direction of water flow and the direction of gravity are both at the polar angle of the outlet hole installation. Vertically, the effects of water flow and gravity on injectability testing can be ignored.

[0032] S7: Introducing the adjustment coefficients shown in equations (6) and (7) into equation (5) yields the injectability of different outlet positions. They are respectively: (8); S8: Use Matlab to plot the injectability of different water outlets measured at the same time as a thermogram, and obtain the spatial distribution map of injectability of the fault fracture zone at the same time. Continue until the spatial distribution map of injectability of the fault fracture zone is similar to the spatial distribution map of injectability of the fault fracture zone tested in the previous minute, then terminate the test.

[0033] The injectability of fault fracture zones in water-rich conditions is affected not only by the inherent porosity characteristics of the fault itself but also by the properties of the injected grout. For example, granular grouts, such as cement grout, often exhibit a filtration effect during injection due to the presence of solid particles, thus affecting injectability and resulting in porous aggregates after grouting. Chemical grouts, on the other hand, do not exhibit this unfavorable property and are poorly soluble in groundwater, thus generally resulting in aggregates with a small number of pores after grouting. However, their cost is higher than that of ordinary cement grout, and the injection grout should be rationally selected based on the formation being injected. This involves the issue of grout compatibility with the formation. When the formation porosity is high and cement grout also provides good injection conditions, both chemical and cement grouts will have good compaction rates, and the choice of grout has little impact on the injectability of the formation. When the formation porosity is low and contains multiple random microfractures, based on the above analysis, the injectability of chemical grouts is greater than that of cement grouts.

[0034] Furthermore, the method also includes performing slurry matching correction on the modified injectability index, including: The grout to be evaluated is injected into the injection hole to form a grouting stone body; Images of different cross-sections of the grouting stone body were obtained, and the solidification rate of each cross-section was calculated; Based on the aforementioned settling rate, the revised injectability index is further revised.

[0035] Furthermore, the process of acquiring images of different cross-sections of the grouting stone body is achieved through CT scanning; the process of calculating the solidity rate of each cross-section is achieved by using image processing algorithms to identify the pore area in the cross-sectional image and calculate the ratio of the pore area to the total cross-sectional area.

[0036] Specifically, the implementation process of this embodiment includes: like Figures 5-6 As shown, in order to further correct the influence of grouting material on the injectability of water-rich fault fracture zones, the injectability was adjusted again based on post-grouting CT testing. The specific steps are as follows: S1: According to Figure 2 In the perforated mode, close all water outlet valves, use professional grouting equipment to inject grout through the water injection holes, and cure it until it is fully hardened; S2: After grouting, the water outlet is filled with grouting material. Core samples (grouting stone body) are taken from the water outlet location on site and then ground into standard test blocks in the laboratory. S3: Use CT scans to perform tomographic scans on different cross sections of grouting stone bodies at different locations; S4: Use MATLAB to develop image processing algorithms to identify two-dimensional grouting stone body slices from CT scans and calculate the pores, fissures, skeleton, and filling material of the grouting stone body slices; S5: Calculate the compaction rate of grouting stones at different locations and cross-sections using the following formula: (9); In the formula, Let be the grouting stone compaction rate at the nth grouting hole and the i-th cross-section; This represents the area occupied by the pores of the grouting stone body at the nth grouting hole and the i-th cross section. Extract the cross-sectional area of ​​the grouting stone body from the nth grouting hole.

[0037] S6: Calculate the average compaction rate of grouting aggregate at a specific location. for: (10); In the formula: q is the total number of slices of the grouting stone body at a certain location.

[0038] S7: The injectability of different outlet hole positions in equation (8) is modified in terms of grouting materials. The injectability of different outlet hole positions after modification are as follows: (11); S8: Use Matlab to draw a heat map to obtain the spatial distribution of injectability of the fault fracture zone under the coupling effect of multiple factors such as water flow, gravity, injected grout, and strata.

[0039] An electronic device, the electronic device comprising: a processor and a memory storing computer program instructions; When the processor executes the computer program instructions, it implements the method for assessing the on-site injectability of fault fracture zones in a water-rich environment.

[0040] A computer storage medium storing computer program instructions, which, when executed by a processor, implement the method for assessing the in-situ injectability of fault fracture zones in a water-rich environment.

[0041] This invention discloses a method for assessing the injectability of fault fracture zones in water-rich environments, effectively overcoming the shortcomings of existing technologies such as scattered evaluation indicators, data lag, and insufficient monitoring accuracy. Through on-site resistivity calibration and dynamic water injection tests, real-time monitoring and dynamic visualization assessment of the injectability of fault fracture zones are achieved, allowing for adjustments to the grouting scheme based on real-time data. By introducing gravity and water flow direction correction coefficients and post-grouting CT compaction rate correction, the method systematically integrates the influence of multiple factors, including formation characteristics, grout properties, and groundwater environment, significantly improving the systematicness and accuracy of the assessment. This method is simple to operate, highly adaptable to field conditions, and can intuitively generate a spatial distribution heat map of injectability, providing a direct and reliable technical basis for grout selection and process parameter optimization in water-rich environments.

[0042] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for assessing the injectability of fault fracture zones in a water-rich environment, characterized in that, include: The initial electrical conductivity of groundwater was obtained in the fault fracture zone at the site; A fluid of a set concentration was injected into the injection hole of the fault fracture zone at a constant rate, while the conductivity of multiple outlet holes arranged around the injection hole was measured during the injection process. Based on the initial conductivity and the real-time conductivity of each outlet hole, the preliminary injectability index of each outlet hole location is calculated. Based on the orientation of each outlet relative to the direction of gravity and the direction of groundwater flow, the preliminary injectability index is corrected to obtain the corrected injectability index. Based on the corrected injectability index of all effluents at the same time, a spatial distribution map of injectability of the fault fracture zone is generated.

2. The method for assessing the injectability of fault fracture zones in a water-rich environment as described in claim 1, characterized in that, The initial electrical conductivity of groundwater is obtained by: Groundwater drawn from the fault fracture zone is introduced into a measuring container with fixed geometric dimensions; Measure the resistance and temperature of the groundwater inside the container; The initial conductivity is determined based on the geometric dimensions of the measuring container, the resistance, and the calculated relationship between the temperature-corrected conductivity and the resistance.

3. The method for assessing the injectability of fault fracture zones in a water-rich environment as described in claim 2, characterized in that, The injected fluid is saturated brine of a set concentration, which is determined based on the measured temperature of the groundwater.

4. The method for assessing the injectability of fault fracture zones in a water-rich environment as described in claim 1, characterized in that, Multiple water outlets arranged around the water injection hole are distributed in multiple concentric rings with the water injection hole as the center, and the number of water outlets on each ring increases as the radius of the ring increases.

5. The method for assessing the injectability of fault fracture zones in a water-rich environment as described in claim 1, characterized in that, The process of calculating the preliminary injectability index of each outlet location is based on the following relationship: the ratio of the real-time conductivity of each outlet to the initial conductivity is used as the preliminary injectability index of the outlet location.

6. The method for assessing the injectability of fault fracture zones in a water-rich environment as described in claim 1, characterized in that, The revision of the preliminary injectability index includes: A first adjustment coefficient related to the direction of gravity is introduced, which is determined based on the angle between the orientation of each water outlet and the direction of gravity. A second adjustment coefficient related to the direction of groundwater flow is introduced, which is determined based on the angle between the orientation of each outlet and the direction of groundwater flow. The modified injectability index is obtained by multiplying the preliminary injectability index, the first adjustment coefficient, and the second adjustment coefficient.

7. The method for assessing the injectability of fault fracture zones in a water-rich environment as described in claim 1, characterized in that, The method further includes correcting the slurry matching of the modified injectability index, including: The grout to be evaluated is injected into the water injection hole to form a grouting stone body; Images of different cross-sections of the grouting stone body were obtained, and the solidification rate of each cross-section was calculated; Based on the aforementioned settling rate, the revised injectability index is further revised.

8. The method for assessing the injectability of fault fracture zones in a water-rich environment as described in claim 7, characterized in that, The process of acquiring images of different cross-sections of the grouting stone body is achieved through CT scanning; the process of calculating the solidity rate of each cross-section is achieved by using image processing algorithms to identify the pore area in the cross-sectional image and calculate the ratio of the pore area to the total cross-sectional area.

9. An electronic device, characterized in that, The electronic device includes: a processor and a memory storing computer program instructions; When the processor executes the computer program instructions, it implements the method for assessing the injectability of fault fracture zones in a water-rich environment as described in any one of claims 1-8.

10. A computer storage medium, characterized in that, The computer storage medium stores computer program instructions, which, when executed by a processor, implement the method for assessing the in-situ injectability of fault fracture zones in a water-rich environment as described in any one of claims 1-8.

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