Grouting design method and system for reinforcement range of elliptical terminal hole splitting in porous medium

Abstract

The application discloses a pore medium elliptical final hole splitting reinforcement range grouting design method and system, relates to the technical field of splitting grouting, and steps are as follows: tunnel surrounding rock characteristics are acquired, the type of the injected medium and the grouting mode are confirmed; ground stress is measured, the spatial distribution of the ground stress is obtained, and the expansion direction of slurry is predicted; a target grouting reinforcement range is divided, the elliptical single-hole splitting reinforcement range is determined according to the spatial distribution of the ground stress; according to the target grouting reinforcement range and the elliptical single-hole splitting reinforcement range, drilling parameters, including drilling hole distance, drilling hole inclination and drilling hole quantity, are determined; the application fully considers the influence of the spatial distribution of the ground stress in the injected medium, so that the design of the advanced curtain grouting is more in line with actual geological conditions and more accurate and effective grouting reinforcement is realized, the uneven reinforcement effect and the emergence of the reinforcement blind area are effectively avoided, and then the reinforcement quality and efficiency are improved.

Description

Technical Field

[0001] This invention relates to the field of grouting reinforcement technology, specifically to a grouting design method and system for reinforcing elliptical final hole splitting in porous media. Background Technology

[0002] With the rapid expansion of engineering construction, tunnels are increasingly traversing complex strata such as water-rich, soft surrounding rock, significantly increasing the risk of geological disasters such as mudslides and water inrushes. To address this challenge, grouting reinforcement technology has become a key means of dealing with mudslides and water inrushes. Among these, fracturing grouting, due to its significant effect on the reinforcement and control of porous media surrounding rock, is widely used in the treatment of large-scale water inrush geological disasters, providing important guarantees for improving tunnel construction safety and engineering stability.

[0003] In the field of grouting engineering, based on the pore characteristics and structural morphology of the injected medium, it can be classified into three types: pipe-type injected medium, fracture-type injected medium, and porous injected medium. Pipe-type injected medium refers to a medium with continuous internal channels, whose pore structure is mainly characterized by a well-connected tubular or porous network. This type of medium typically has large pore sizes and strong connectivity, allowing the grout to move rapidly along the pipe channels, exhibiting typical pipe flow characteristics. Fracture-type injected medium consists of a network of fractures in the soil or rock mass, with its pore structure exhibiting an irregular sheet-like or strip-like distribution. The fracture width is small, and the connectivity is between that of pipe-type and porous media; the flow pattern of the grout in this type of medium mainly exhibits fracture flow characteristics. Porous injected medium consists of tiny pores between particles, and its internal pore network exhibits a dispersed, non-connected microstructure. Due to the extremely small pore size and poor connectivity, the grout in this medium mainly moves in the form of seepage flow, and may even split and expand when seepage is restricted.

[0004] In tunnel construction, when facing adverse geological conditions and requiring reinforcement, advanced curtain grouting is often used as an important treatment method for the pore-filled medium. However, in existing advanced curtain splitting grouting final hole design methods, the final hole range is often simplified to a perfectly circular splitting diffusion range. This design has the following drawbacks:

[0005] First, based on the results of indoor split grouting physical tests, the morphology of split grout veins revealed during on-site split grouting excavation, the hydraulic fracturing theory developed over a century ago, and the mature split grout vein diffusion mechanism, it is evident that split grout veins preferentially develop along the direction of maximum principal stress, compacting the injected medium distributed on both sides of the split grout vein, and rarely developing towards the direction of minimum principal stress. This phenomenon indicates that in the direction of maximum principal stress, the grout drives the expansion of the split surface and exerts a compacting effect on the surrounding medium, thereby enhancing the reinforcement effect; while in the direction of minimum principal stress, due to weaker stress constraints, grout expansion is limited, making it difficult to form an effective split channel. The circular split diffusion range ignores the significant influence of the spatial distribution of ground stress on the direction of grout split diffusion, resulting in the grout diffusion direction not matching the actual ground stress field, easily causing uneven reinforcement effects. Especially in the direction of minimum principal stress, insufficient grout expansion fails to effectively cover weak areas, leading to reduced reinforcement quality and even forming reinforcement blind zones in some places, affecting the stability of the surrounding rock and the safety of the tunnel.

[0006] Secondly, the drilling layout is inefficient. Because the circular diffusion range is not optimized according to the geostress in different directions, traditional designs often require uniform drilling throughout the entire area. However, variations in the geostress field lead to different reinforcement requirements in different areas. The circular design results in an unreasonable distribution of hole spacing between weak and dominant directions, often requiring more holes to achieve the same reinforcement effect. This leads to an excessive number of holes, increased borehole length, extended construction period, reduced project efficiency, and increased construction costs. Summary of the Invention

[0007] To address one or more shortcomings of the existing technology, this invention provides a grouting design method and system for elliptical final hole splitting reinforcement range in porous media. It fully considers the significant influence of ground stress on the diffusion direction and range of splitting grout veins, optimizes the hole layout and number of grouting holes, and achieves precise and effective division of the effective reinforcement range of the splitting grout veins on the strata. It leaves no blind spots in splitting grouting reinforcement, improves the effect of curtain grouting reinforcement, ensures the long-term stability of tunnel engineering, and improves engineering efficiency.

[0008] To achieve the above objectives, the present invention adopts one or more of the following technical solutions:

[0009] A grouting design method for reinforcing elliptical terminal hole splitting in porous media is provided, including the following steps:

[0010] Obtain the characteristics of the surrounding rock of the tunnel and confirm the type of grouting medium and grouting method;

[0011] By measuring in-situ stress, the spatial distribution of in-situ stress can be obtained, and the direction of grout propagation can be predicted.

[0012] The target grouting reinforcement range is defined, and the elliptical single-hole splitting reinforcement range is determined based on the spatial distribution of ground stress; the single-hole splitting reinforcement range includes the reinforcement range in the direction of maximum principal stress and the reinforcement range in the direction of minimum principal stress.

[0013] Based on the target grouting reinforcement range and the elliptical single-hole splitting reinforcement range, determine the drilling parameters, including drilling location, hole spacing, drilling inclination angle, and number.

[0014] Furthermore, the acquisition of tunnel surrounding rock characteristics and confirmation of the type of injected medium and grouting method specifically includes:

[0015] Collect geological and hydrological information, including geological and lithological information, lithological distribution, fracture development, and hydrological conditions in the tunnel area;

[0016] Geomechanical tests are conducted on the surrounding rock of the tunnel to obtain its characteristics, including the compressive strength, porosity, and permeability of the injected medium, and to assess the impact of geological conditions on the grouting design.

[0017] The type of grouting medium is determined based on geological and hydrological information and surrounding rock characteristics, and the grouting method is determined based on the type of grouting medium; the type of grouting medium includes porous grouting medium, fracture grouting medium or pipeline grouting medium.

[0018] Furthermore, obtain in-situ stress test data and analyze the spatial distribution of in-situ stress, including:

[0019] By selecting a ground stress measurement method, obtaining ground stress test data, acquiring the three-dimensional spatial distribution direction of ground stress, clarifying the magnitude of the three-dimensional ground stress, determining the stress field changes in different regions, as well as the direction and magnitude of the maximum and minimum principal stresses, and determining the preferred expansion direction of the grout during grouting.

[0020] Furthermore, the ground stress measurement methods include the pressure pillow method, the rigid inclusion stress gauge method, the hydraulic fracturing method, the borehole stress relief method, and the borehole wall collapse measurement method.

[0021] Furthermore, the division of the target grouting reinforcement area specifically refers to:

[0022] Based on the analysis of the surrounding rock properties and geological defects of the tunnel, the area requiring reinforcement is defined as follows: 5 to 7 meters outside the tunnel excavation outline is the outer outline of the reinforcement range; the area between the tunnel excavation outline and the outer outline of the reinforcement range is the target grouting reinforcement range; both the tunnel excavation outline and the outer outline of the reinforcement range are closed, which can improve stability and prevent long-term damage to the tunnel from water seepage.

[0023] Furthermore, determining the elliptical single-hole splitting reinforcement range based on the spatial distribution of ground stress includes:

[0024] Determine the directions of the maximum and minimum principal stresses based on the geostress test data;

[0025] Determine the slurry diffusion radius in the direction of maximum principal stress:

[0026] ;

[0027] in, The slurry diffusion radius is located in the direction of maximum principal stress. The grouting pressure at the outlet; The minimum principal stress in the environment where the injected medium exists; The Young's modulus in the direction of splitting and diffusion in the injected medium; Poisson's ratio in the direction of splitting and diffusion in the injected medium.

[0028] Furthermore, it also includes determining the slurry diffusion radius in the direction of minimum principal stress, specifically:

[0029] The physical parameters of the rock mass are obtained, and the finite element analysis or discrete element method is used to perform simulation calculations to obtain the effective reinforcement influence range of the splitting and diffusing grout veins on the injected medium in the direction of minor principal stress.

[0030] The elastic modulus, Poisson's ratio, and density of the injected medium are obtained. Based on the theory of circular hole expansion, a mechanical model of the compaction effect of the expansion of the split slurry channel on the injected medium is established.

[0031] Furthermore, based on the target grouting reinforcement range and the elliptical single-hole splitting reinforcement range, the drilling locations and hole spacing are determined, including:

[0032] The borehole spacing along the major axis of the elliptical single-hole splitting reinforcement range is 0.8 to 0.9 times the slurry diffusion radius along the direction of the maximum principal stress.

[0033] The borehole spacing in the short axis direction of the elliptical single-hole splitting reinforcement range is 0.8~0.9 times the slurry diffusion radius in the direction of the minimum principal stress;

[0034] The boreholes are arranged in a ring or radial pattern.

[0035] Furthermore, based on the target grouting reinforcement range and the elliptical single-hole splitting reinforcement range, the borehole inclination angle is determined, including:

[0036] Determine the drilling inclination angle in each direction based on the grouting reinforcement range and the final hole intersection diagram to ensure that the elliptical single-hole splitting reinforcement range of all boreholes can completely cover the required grouting reinforcement range.

[0037] Furthermore, the methods for determining the drilling inclination angle and the number of boreholes are as follows:

[0038] Based on the borehole spacing, the target grouting reinforcement range, and the elliptical single-hole splitting reinforcement range, and following the principle of the minimum number of boreholes that can completely cover the target grouting reinforcement range, the final borehole intersection diagram on the target tunnel section is obtained.

[0039] Connect the center point of the excavation face with the center point of the elliptical single-hole splitting reinforcement range in the final hole intersection diagram on the target tunnel section to obtain the vertical inclination angle, horizontal inclination angle and hole depth in three-dimensional space.

[0040] Drilling is performed based on the vertical inclination angle, horizontal inclination angle, and hole depth to obtain the number of holes.

[0041] Furthermore, after determining the reinforcement range of the elliptical single-hole fracturing, the single-hole initiation fracturing pressure is obtained based on the magnitude of the minimum principal stress and combined with hydraulic fracturing theory.

[0042] ;

[0043] in, To generate splitting pressure, The fracture toughness coefficient of the injected medium. The minimum principal stress in the environment in which the injected medium exists. The radius of the grouting inlet. The critical radius for splitting extension.

[0044] A grouting design system for reinforcing elliptical terminal hole splitting in porous media is also provided, comprising:

[0045] The data acquisition module is used to acquire tunnel surrounding rock characteristics and ground stress measurement data;

[0046] The grouting analysis module is used to determine the type of grouting medium and grouting method based on the characteristics of the surrounding rock of the tunnel, and to obtain the spatial distribution of ground stress and predict the direction of grout expansion based on ground stress measurement data.

[0047] The target grouting reinforcement range determination module is used to determine the elliptical single-hole splitting reinforcement range based on the spatial distribution of ground stress; the single-hole splitting reinforcement range includes the reinforcement range in the direction of maximum principal stress and the reinforcement range in the direction of minimum principal stress.

[0048] The drilling parameter determination module is used to determine drilling parameters, including drilling location, hole spacing, drilling inclination angle, and number of holes, based on the target grouting reinforcement range and the elliptical single-hole splitting reinforcement range.

[0049] By adopting the above technical solution, the beneficial effects of the present invention are as follows:

[0050] 1. In this invention, the range of elliptical single-hole splitting reinforcement is quantitatively determined based on the diffusion law of elliptical final borehole, thereby optimizing the drilling parameters of splitting grouting. On the one hand, the influence of the spatial distribution of ground stress in the injected medium is fully considered, making the design of advanced curtain grouting more in line with actual geological conditions. On the other hand, the range of single-hole splitting reinforcement is designed according to the direction of maximum principal stress and the direction of minimum principal stress, thereby determining the location and number of boreholes, achieving more precise and effective grouting reinforcement. Compared with traditional grouting design, it effectively avoids uneven reinforcement effect and the occurrence of reinforcement blind spots, thereby improving reinforcement quality and efficiency.

[0051] 2. The present invention designs the borehole spacing based on the elliptical single-hole splitting reinforcement range. It can appropriately increase the hole spacing in the weak direction and increase the hole spacing in the dominant direction, thereby optimizing the diffusion effect of the grouting liquid. Under the same coverage conditions, the number of boreholes is reduced, which effectively improves construction efficiency, reduces the length of the borehole, significantly shortens the project cycle, reduces construction costs, and improves the overall economic benefits of the project. Attached Figure Description

[0052] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0053] Figure 1 This is a schematic diagram of the mechanical model showing the influence of ground stress distribution on the grout diffusion direction and effective reinforcement range in Embodiment 1 of the present invention;

[0054] Figure 2 This is a schematic diagram of the target grouting reinforcement area in Embodiment 1 of the present invention;

[0055] Figure 3 A schematic diagram showing the design of the diffusion range of the circular final hole in advanced curtain splitting grouting technology;

[0056] Figure 4 This is a schematic diagram of the design of the diffusion range of the flat elliptical final hole in the advanced curtain splitting grouting under the condition that the horizontal stress is greater than the vertical stress in Embodiment 1 of the present invention.

[0057] Figure 5 This is a schematic diagram of the design of the diffusion range of the flat elliptical final hole in the advanced curtain splitting grouting under the condition that the vertical stress is greater than the horizontal stress in Embodiment 1 of the present invention.

[0058] Figure 6 This is a schematic diagram comparing the splitting and diffusion range of a flat elliptical terminal hole in Embodiment 1 of the present invention with that of a traditional circular terminal hole. Detailed Implementation

[0059] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0060] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0061] Example 1

[0062] In a typical embodiment of the present invention, combined with Figures 1-5 As shown, a grouting design method for reinforcing elliptical terminal hole splitting in porous media is provided, including the following steps:

[0063] Obtain the characteristics of the surrounding rock of the tunnel and confirm the type of grouting medium and grouting method;

[0064] By measuring in-situ stress, the spatial distribution of in-situ stress can be obtained, and the direction of grout propagation can be predicted.

[0065] The target grouting reinforcement range is defined, and the elliptical single-hole splitting reinforcement range is determined based on the spatial distribution of ground stress; the single-hole splitting reinforcement range includes the reinforcement range in the direction of maximum principal stress and the reinforcement range in the direction of minimum principal stress.

[0066] Based on the target grouting reinforcement range and the elliptical single-hole splitting reinforcement range, determine the drilling parameters, including drilling location, hole spacing, drilling inclination angle, and number of holes.

[0067] It should be noted that existing advanced curtain splitting grouting final hole design methods often neglect the significant influence of the spatial distribution of ground stress on the splitting diffusion direction of the grout, leading to uneven reinforcement effects or blind spots. Therefore, the grouting design method provided in this embodiment fully considers the distribution of ground stress and optimizes the number and location of grouting holes using an elliptical diffusion range, thereby achieving a more precise and efficient reinforcement effect while improving engineering efficiency and reducing construction costs.

[0068] Specifically, the steps of the grouting design method in this embodiment are as follows:

[0069] Step 1: Obtain the characteristics of the surrounding rock of the tunnel and confirm the type of grouting medium and grouting method.

[0070] Step 101: Collect geological and hydrological information; conduct geomechanical tests on the surrounding rock of the tunnel to obtain the characteristics of the surrounding rock.

[0071] Before implementing advanced curtain grouting, it is essential to collect and analyze detailed engineering geological and hydrological environmental information, including geological and lithological information of the tunnel area, lithological distribution, fracture development, and hydrological conditions. Through drilling, geological exploration, and other geomechanical tests, as well as geophysical property tests, the main characteristics of the surrounding rock, such as the compressive strength, porosity, and permeability of the grouting medium, are obtained to assess the impact of geological conditions on the grouting design. Furthermore, the analysis of hydrological conditions helps determine the groundwater level, potential water sources, and their pressure, which is crucial for designing the grouting pressure and grout type.

[0072] Step 102: Analyze the type of the medium to be injected and determine the grouting method.

[0073] The type of grouting medium is determined based on geological and hydrological information and surrounding rock characteristics, and the grouting method is then determined based on the type of grouting medium. According to the porosity characteristics of the rock mass, the grouting medium is classified into one of three types: porous grouting medium, fracture grouting medium, or conduit grouting medium. The porosity characteristics and connectivity of different media have a significant impact on the diffusion characteristics of the grout, which is crucial for analyzing the applicability of the fracturing diffusion grouting design method. For porous media, the grout's permeation and flow are restricted, making fracturing more likely; for fractured media, the grout extends along the fractures, and the development direction of the fracturing grout veins is significantly influenced by the fracture orientation. Through the applicability analysis of the grouting medium, it can be determined whether curtain fracturing grouting design is suitable and a reasonable grouting scheme can be determined.

[0074] Step 2: Measure the ground stress to obtain the spatial distribution of ground stress and predict the direction of grout propagation.

[0075] Step 201: Select the ground stress measurement method.

[0076] When conducting spatial distribution analysis of in-situ stress, it is necessary to select appropriate measurement methods. Commonly used methods include the pressure pillow method, the rigid inclusion stress gauge method, and the hydraulic fracturing method. In addition, indirect methods such as the borehole stress relief method and the borehole wall collapse measurement method can also be used. When selecting a method, the geological complexity and construction conditions of the tunnel face area should be considered. The applicability and accuracy of each method need to be selected based on the actual situation and adjusted reasonably according to the site conditions.

[0077] Step 202: Calculate the direction and magnitude of the geostress.

[0078] After selecting a suitable in-situ stress measurement method, in-situ stress test data is obtained to determine the three-dimensional spatial distribution direction of in-situ stress. Based on the test results, the stress characteristics of different regions can be obtained. In-situ stress test data includes the spatial azimuth and magnitude of in-situ stress. Analyzing the spatial distribution of this data clarifies essential information such as the magnitude of the three-dimensional in-situ stress. Of particular interest are the direction and magnitude of the maximum and minimum principal stresses, which directly affect the direction of grout splitting and diffusion in the injected medium within the pores. By analyzing this data, the preferred expansion direction of the grout during injection can be determined, thereby optimizing the grouting borehole layout and designing the grouting pressure.

[0079] Step 203: Combined analysis of geostress and geological characteristics.

[0080] By combining the spatial distribution of in-situ stress with the fracture characteristics of the surrounding rock, the influence of in-situ stress on the propagation of fracturing grout veins is further analyzed. For example, in high-stress areas, grout may preferentially propagate along the direction of the maximum principal stress, while in areas with lower stress, grout propagation is limited. Through this comprehensive analysis, designers can determine the range of influence of the stress field and reasonably predict the direction of grout propagation, ultimately optimizing the design of grouting hole locations and spacing to avoid reinforcement blind spots. Figure 1 As shown, in the injected medium simplified to a homogeneous layer, the fracturing grout preferentially diffuses towards the direction of maximum principal stress. The main fracturing grout vein develops in the direction of maximum principal stress. In the direction of minimum principal stress, the fracturing diffusion of the main grout vein is hindered, often resulting in a compaction diffusion effect. Therefore, the single-hole fracturing reinforcement range can be more scientifically divided into an ellipse. Within its grout vein fracturing-compaction influence range, the fracturing diffusion range along the major axis of the ellipse can approach the tip of the main fracturing grout vein, while the compaction diffusion range along the minor axis of the ellipse often represents the boundary of the compaction effect of the main fracturing grout vein on the injected medium.

[0081] For example, using fully weathered Anshan basalt as the injection medium, with a vertical ground stress of 6 MPa, an injection pressure of 2.2 MPa, and cement-water glass double-liquid grout (water-cement ratio 1:1, volume ratio 1:1), the influence range of the split grout vein on the compaction of the injection medium in the direction of minor principal stress (short axis direction of elliptical diffusion range) is 5-10 cm per side, then the short axis length is 10-20 cm.

[0082] Step 3: Divide the target grouting reinforcement range and determine the elliptical single-hole splitting reinforcement range based on the spatial distribution of ground stress.

[0083] Step 301: Analyze the properties of the surrounding rock and the reinforcement requirements.

[0084] First, the areas requiring reinforcement are analyzed based on the properties and geological defects of the surrounding rock. The stability of the surrounding rock needs to be assessed, and potential adverse geological bodies, such as fractured zones, fissure zones, or weak surrounding rock, need to be identified. These areas have a significant impact on tunnel construction, therefore, reinforcement should be prioritized, and the number of grouting holes within the key reinforcement area should even be increased. In this embodiment, as... Figure 2 As shown, the outer contour of the reinforcement range is 5 to 7 meters outside the tunnel excavation outline. The area between the tunnel excavation outline and the outer contour of the pre-curtain grouting reinforcement range is the target grouting reinforcement range. Both the tunnel excavation outline and the outer contour of the pre-curtain grouting reinforcement range are closed, which can improve stability and prevent long-term damage to the tunnel from water seepage.

[0085] Step 302: Hierarchical and zoned design of the grouting zone.

[0086] When defining the target grouting reinforcement area, the reinforcement zone is divided into multiple grouting zones. Depending on the actual project requirements, segmented forward or backward grouting methods can be adopted. This layered grouting approach ensures that the grout spreads evenly within the target area, forming a stable reinforcement barrier. Zoned design helps improve the reinforcement effect of fracturing grouting and avoids the formation of blind spots.

[0087] Step 303: Determine the range of elliptical single-hole splitting reinforcement based on the direction of ground stress.

[0088] Based on in-situ stress test data, the propagation direction of the fracturing grout veins was determined. According to hydraulic fracturing theory, during fracturing grouting, the propagation direction of the grout is controlled by the in-situ stress field. The grout pressure must overcome the minimum principal stress to form a fracture. Once a fracture is formed, the grout will preferentially propagate along the direction of the maximum principal stress because the normal constraint is strongest in this direction, resulting in a larger fracture opening and lower flow resistance.

[0089] Since the direction of maximum principal stress should be the direction of preferential grout expansion, and considering the actual geological conditions and stress field changes, the grout diffusion range is confirmed to be a flat ellipse, such as... Figures 4-6 As shown, the ellipse is defined by extending its major axis along the direction of maximum principal stress and its minor axis along the direction of minor principal stress. This ensures that the grout can effectively extend to the area that needs reinforcement. Compared with the traditional circular diffusion range, this avoids wasting grout in unwanted areas, greatly reduces construction costs, and effectively reduces blind spots in grouting reinforcement.

[0090] When designing the effective reinforcement range of a single borehole, the grout expansion range is adjusted according to the direction of the maximum principal stress. For areas limited by the direction of the minimum principal stress, the layout of the grouting boreholes is adjusted to ensure that the grout can fully expand in the direction of the maximum principal stress and avoid forming blind spots in the direction of the minimum principal stress, ultimately forming a stable reinforcement barrier.

[0091] The design of the effective fracturing reinforcement range for an elliptical single-hole requires detailed calculations based on the rock mass characteristics, in-situ stress distribution, and grout propagation characteristics. First, the grout propagation radius R of the single hole is estimated based on factors such as grout properties, grouting pressure, and rock mass permeability. Through experimental data and empirical formulas, the grout propagation radius under different conditions can be obtained, and this is used as the basis for determining the effective reinforcement range of the single hole. Typically, this range is elliptical or wing-shaped.

[0092] Step 3031: Determine the effective reinforcement range in the direction of maximum principal stress.

[0093] In advanced curtain grouting design, the calculation of the splitting diffusion radius usually depends on factors such as the in-situ stress of the rock mass, the properties of the grout, and the grouting pressure; the formula for calculating the splitting grout vein diffusion radius in the direction of maximum principal stress is:

[0094] ;

[0095] in, The slurry diffusion radius is located in the direction of maximum principal stress. The grouting pressure at the outlet; The minimum principal stress in the environment where the injected medium exists; The Young's modulus in the direction of splitting and diffusion in the injected medium; Poisson's ratio in the direction of splitting and diffusion in the injected medium.

[0096] Step 3032: Determine the effective reinforcement range in the direction of minimum principal stress.

[0097] In the direction of minor principal stress, the grout diffusion radius is further compacted by the expansion of the fracturing grout channels. The method for determining the grout diffusion radius in the direction of minimum principal stress is as follows:

[0098] Step 1: Obtain the physical parameters of the rock mass and perform simulation calculations using finite element analysis or discrete element method to obtain the effective reinforcement influence range of the splitting and diffusing grout veins on the injected medium in the direction of minor principal stress.

[0099] Step 2: Obtain the elastic modulus, Poisson's ratio, and density of the injected medium. Based on the theory of circular hole expansion, establish a mechanical model of the compaction effect of the split grout channel expansion on the injected medium within the effective reinforcement influence range.

[0100] Step 3: Verify the effective reinforcement range of the splitting and diffusion grout vein on the injected medium in the direction of minor principal stress through on-site mechanical testing.

[0101] Specifically, numerical simulation techniques such as finite element analysis (FEM) or discrete element method (DEM) are used, combined with parameters such as the porosity, compressive strength and minor principal stress of the rock mass, to calculate the effective reinforcement range of the splitting and diffusion grout veins on the injected medium in the direction of minor principal stress, and to simulate the range of influence under different grouting pressures and porosity of the injected medium.

[0102] And through the theory of circular hole expansion, such as Figure 1 As shown, a mechanical model of the compaction effect of the split grout channel expansion on the injected medium is established, taking into account factors such as the elastic modulus, Poisson's ratio, and density of the porous injected medium. Finally, in actual engineering, the effective reinforcement range of the split grout in the porous injected medium on both sides of the injected medium is verified by field mechanical testing, and the design parameters are adjusted according to the actual situation.

[0103] In one specific embodiment of the present invention, the injected medium is fully weathered Anshanite basalt with a particle size of less than 0.01 mm, a porosity of 6.3%, and a density of 19.3 g / cm³. 3 When the confining pressure is 2 MPa, the triaxial peak deviatoric stress is 1.5 MPa. Under the in-situ stress environment with a maximum principal stress of 3.6 MPa and a minimum principal stress of 1.2 MPa, and with the grout being a cement-water glass two-component grout with a water-cement ratio of 1:1, a volume ratio of 1:1, a water glass modulus of 3.1, and a Baume degree of 40°, the diffusion radius in the direction of the maximum principal stress of the elliptical single-hole splitting reinforcement range is 0.9–1.15 m, and the diffusion radius in the direction of the minimum principal stress is 0.35–0.6 m.

[0104] Step 4: Single-hole splitting pressure design.

[0105] Step 401: Calculation of rock mass stress state and splitting pressure.

[0106] The design of the initiation splitting pressure is based on the geostress state of the rock mass, particularly the magnitude of the minor principal stress. Based on geostress test data, the minimum principal stress in the rock mass is calculated, and the required initiation splitting pressure is derived using hydraulic fracturing theory. The initiation splitting pressure must be large enough to overcome the minimum principal stress and initiate fracture propagation in the rock mass. A theoretical value can be obtained through calculation formulas, serving as the initial design initiation splitting pressure.

[0107] The calculation formula for the splitting pressure in pre-curtain grouting is typically based on the mechanical properties of the rock mass, the grouting pressure, and the rock mass fracture mechanism. The splitting pressure is the pressure at which the grouting pressure just causes the rock mass to fracture. In practical engineering, the splitting pressure of pre-curtain grouting can be estimated using the following formula:

[0108] ;

[0109] in, It is the splitting pressure, It is the fracture toughness coefficient of the injected medium. It is the minimum principal stress in the environment where the injected medium exists. It is the radius of the grouting port. It is the critical radius for splitting and propagation.

[0110] Step 402: Slurry characteristics and pressure adjustment.

[0111] In practical design, the properties of the grout (such as viscosity and expansibility) have a significant impact on the splitting pressure. Different types of grout require different pressures to effectively propagate the fractures. Based on the grout characteristics and actual construction conditions, designers need to adjust the grouting pressure to avoid unnecessary rock mass damage due to excessive pressure, or ineffective fracture propagation due to insufficient pressure. Therefore, during actual grouting, the splitting pressure needs to be dynamically adjusted based on the feedback from the grout.

[0112] Step 403: On-site verification and adjustment of splitting pressure.

[0113] Before construction, small-scale test grouting is conducted to verify the theoretically designed splitting pressure, and the design is adjusted based on field feedback. The test results will help designers optimize the grouting pressure and adjust the drilling depth and grouting volume. Through repeated adjustments, the splitting pressure is ensured to reach its optimal state, allowing the grout to effectively expand within the rock mass, forming a stable splitting grout vein network and providing sufficient reinforcement.

[0114] In actual engineering projects, splitting of the injected medium can only be achieved when the grouting pressure exceeds the initial splitting pressure. Therefore, the grouting pressure at the outlet is crucial. The value needs to be greater than the splitting pressure. In this embodiment, the splitting pressure on site is confirmed through the above steps to facilitate a more accurate determination of the grouting pressure at the grout outlet. This improves the accuracy of the splitting vein diffusion radius in the directions of maximum and minimum principal stress.

[0115] Step 5: Determine the drilling parameters based on the target grouting reinforcement range and the elliptical single-hole splitting reinforcement range.

[0116] Step 501: Determine the borehole spacing.

[0117] In the design of the elliptical diffusion range, the arrangement of boreholes needs to be optimized according to the direction of the geostress field. The borehole spacing along the major axis should be appropriately increased to allow the grout to spread along the direction of the maximum principal stress. The borehole spacing along the minor axis should be denser to ensure that the grout can effectively cover weak areas. In this embodiment, the borehole spacing along the major axis of the elliptical single-hole splitting reinforcement range is 0.8 to 0.9 times the grout diffusion radius along the direction of the maximum principal stress, ensuring that the grout fully overlaps along the direction of the maximum principal stress. The borehole spacing along the minor axis of the elliptical single-hole splitting reinforcement range is 0.8 to 0.9 times the grout diffusion radius along the direction of the minimum principal stress, densifying the borehole spacing along the minor axis to compensate for insufficient diffusion, improve the reinforcement effect of weak areas, and avoid reinforcement blind spots. After determining the borehole spacing, combining the target grouting reinforcement range and the elliptical single-hole splitting reinforcement range, and following the principle of the minimum number of boreholes required to completely cover the target grouting reinforcement range, a final borehole overlap diagram on a certain tunnel section is obtained, such as... Figure 4 and Figure 5 As shown. The boreholes can be arranged in a ring or radial pattern to ensure that the grout is evenly distributed to the intended reinforcement area.

[0118] Combination Figure 6 As shown, in traditional grouting designs where boreholes are evenly distributed according to the splitting and diffusion range of a perfectly circular final borehole, reinforcement blind zones are easily formed in and around the direction of minimum principal stress. Figure 6 The area where the circular part does not overlap with the ellipse is actually the area where the split grout vein did not spread after drilling. Therefore, this embodiment effectively improves the reinforcement quality of curtain split grouting.

[0119] Step 502: Determine the drilling inclination angle, hole depth, and number of holes.

[0120] The borehole inclination angle should be adjusted according to the elliptical diffusion range. Specifically, in conjunction with... Figure 4 and Figure 5 As shown, the drilling inclination angle in each direction is determined according to the grouting reinforcement range and the final hole intersection diagram to ensure that the elliptical single-hole splitting reinforcement range of all boreholes can completely cover the required grouting reinforcement range.

[0121] The specific determination method is as follows: Based on the required grouting reinforcement length (usually 15-30m) of the curtain grouting in the tunnel axis advancement direction, and the center point of the elliptical single-hole splitting reinforcement range formed by each grouting hole on the final hole intersection diagram, connect the center point of the excavation face and the center point of the elliptical single-hole splitting reinforcement range to obtain three key parameters in three-dimensional space: vertical inclination angle, horizontal inclination angle, and hole depth, thus completing the design of the advanced curtain grouting drilling parameters.

[0122] In this embodiment, the drilling inclination angles along the major axis and minor axis of the elliptical single-hole splitting reinforcement range are 0~35 degrees, respectively, which can prevent the grout from spreading to areas that do not need reinforcement. At the same time, the hole depth should be set according to the thickness of the reinforcement range, with a deeper hole along the major axis to ensure effective grout expansion in that direction and ultimately ensure the formation of a uniform and stable reinforcement curtain.

[0123] Based on the vertical inclination angle, horizontal inclination angle and hole depth within the above three-dimensional spatial range, drilling is performed to obtain the number of boreholes, i.e., the number of grouting holes.

[0124] In a specific embodiment provided by the present invention, combined with Figures 3-5 As shown, a conventional circular split grout vein intersection diagram requires 63 boreholes. However, by adopting the grouting design method for elliptical final-hole splitting reinforcement range in porous media of this invention, and designing a flat elliptical grout vein intersection diagram, only 55 boreholes are needed within the same grouting reinforcement range under the condition that the horizontal stress is greater than the vertical stress, reducing the number of boreholes by 8 (12.7%) and the drilling length by over 200 meters (taking a 25m advanced curtain range as an example); under the condition that the vertical stress is greater than the horizontal stress, only 49 boreholes are needed within the same grouting reinforcement range, reducing the number of boreholes by 14 (22.2%) and the drilling length by over 350 meters (taking a 25m advanced curtain range as an example). This significantly reduces the number of boreholes, shortens the construction period, lowers costs, and improves the safety and economic benefits of tunnel engineering.

[0125] In another typical embodiment of the present invention, a grouting design system for reinforcing elliptical terminal hole splitting in porous media is also provided, comprising:

[0126] The data acquisition module is used to acquire tunnel surrounding rock characteristics and ground stress measurement data;

[0127] The grouting analysis module is used to determine the type of grouting medium and grouting method based on the characteristics of the surrounding rock of the tunnel, and to obtain the spatial distribution of ground stress and predict the direction of grout expansion based on ground stress measurement data.

[0128] The target grouting reinforcement range determination module is used to determine the elliptical single-hole splitting reinforcement range based on the spatial distribution of ground stress; the single-hole splitting reinforcement range includes the reinforcement range in the direction of maximum principal stress and the reinforcement range in the direction of minimum principal stress.

[0129] The drilling parameter determination module is used to determine drilling parameters, including drilling location, hole spacing, drilling inclination angle, and number of holes, based on the target grouting reinforcement range and the elliptical single-hole splitting reinforcement range.

[0130] The grouting design method and system proposed in this invention, based on the elliptical final-hole splitting reinforcement range in porous media, fully considers the influence of in-situ stress on splitting grout veins, clarifies the preferential splitting and diffusion direction and range of splitting grout veins in the injected medium, and optimizes the design of drilling parameters and grouting pressure during advanced curtain grouting by accurately determining the effective reinforcement influence range of the splitting grout veins, thus avoiding reinforcement blind spots and resource waste that occur in traditional designs. Simultaneously, it not only improves the scientific rigor and efficiency of grouting reinforcement but also reduces the number of boreholes and construction period, lowers costs, and enhances the safety and economic benefits of tunnel engineering.

[0131] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Those skilled in the art should understand that the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A grouting design method for reinforcing elliptical terminal hole splitting in porous media, characterized in that, Includes the following steps: Obtain the characteristics of the surrounding rock of the tunnel and confirm the type of grouting medium and grouting method; By measuring in-situ stress, the spatial distribution of in-situ stress can be obtained, and the direction of grout propagation can be predicted. The target grouting reinforcement area is defined, and the elliptical single-hole splitting reinforcement area is determined based on the spatial distribution of in-situ stress. The single-hole splitting reinforcement area includes the reinforcement area along the direction of maximum principal stress and the reinforcement area along the direction of minimum principal stress. Determining the elliptical single-hole splitting reinforcement area based on the spatial distribution of in-situ stress includes: Determine the directions of the maximum and minimum principal stresses based on the geostress test data; Determine the slurry diffusion radius in the direction of maximum principal stress: ； In the formula, The slurry diffusion radius is located in the direction of maximum principal stress. The grouting pressure at the outlet; The minimum principal stress in the environment where the injected medium exists; The Young's modulus in the direction of splitting and diffusion in the injected medium; Poisson's ratio in the direction of splitting diffusion in the injected medium; Based on the target grouting reinforcement range and the elliptical single-hole splitting reinforcement range, determine the drilling parameters, including hole spacing, drilling inclination angle, and number of holes. Specifically: Based on the target grouting reinforcement range and the elliptical single-hole splitting reinforcement range, determine the drilling location and spacing: the drilling spacing along the major axis of the elliptical single-hole splitting reinforcement range is 0.8~0.9 times the grout diffusion radius along the direction of maximum principal stress; the drilling spacing along the minor axis of the elliptical single-hole splitting reinforcement range is 0.8~0.9 times the grout diffusion radius along the direction of minimum principal stress; the drilling arrangement can be annular or radial. The method for determining the borehole inclination angle and the number of boreholes is as follows: Based on the borehole spacing, the target grouting reinforcement range, and the elliptical single-hole splitting reinforcement range, and following the principle of the minimum number of boreholes that can completely cover the target grouting reinforcement range, obtain the final borehole intersection diagram on the target tunnel section; connect the center point of the excavation face with the center point of the elliptical single-hole splitting reinforcement range in the final borehole intersection diagram on the target tunnel section to obtain the vertical inclination angle, horizontal inclination angle, and borehole depth in three-dimensional space; drill boreholes according to the vertical inclination angle, horizontal inclination angle, and borehole depth to obtain the number of boreholes.

2. The grouting design method for the elliptical final hole splitting reinforcement range in porous media as described in claim 1, characterized in that, The acquisition of tunnel surrounding rock characteristics, confirmation of the type of injected medium and grouting method specifically includes: Collect geological and hydrological information, including geological and lithological information, lithological distribution, fracture development, and hydrological conditions in the tunnel area; Geomechanical tests are conducted on the surrounding rock of the tunnel to obtain its characteristics, including the compressive strength, porosity, and permeability of the injected medium, and to assess the impact of geological conditions on the grouting design. The type of grouting medium is determined based on geological and hydrological information and surrounding rock characteristics, and the grouting method is determined based on the type of grouting medium; the type of grouting medium includes porous grouting medium, fracture grouting medium or pipeline grouting medium.

3. The grouting design method for the elliptical final hole splitting reinforcement range in porous media as described in claim 1, characterized in that, Acquire geostress test data and analyze the spatial distribution of geostress, including: By selecting a ground stress measurement method and obtaining ground stress test data, and using a mathematical model to analyze the stress test data, the stress field changes in different regions, as well as the direction and magnitude of the maximum and minimum principal stresses, are determined, thus determining the preferred direction of grout expansion during grouting.

4. The grouting design method for the elliptical final hole splitting reinforcement range in porous media as described in claim 1, characterized in that, The division of the target grouting reinforcement area is specifically as follows: Based on the analysis of the surrounding rock properties and geological defects of the tunnel, the areas that need to be reinforced are defined. The distance outside the tunnel excavation outline is set as the outer outline of the reinforcement range. The area between the tunnel excavation outline and the outer outline of the reinforcement range is the target grouting reinforcement range. Both the tunnel excavation outline and the outer outline of the reinforcement range are closed, which can improve stability and prevent long-term damage to the tunnel from water seepage.

5. The grouting design method for the elliptical final hole splitting reinforcement range in porous media as described in claim 1, characterized in that, This also includes determining the slurry diffusion radius in the direction of minimum principal stress, specifically: The physical parameters of the rock mass are obtained, and the finite element analysis or discrete element method is used to perform simulation calculations to obtain the effective reinforcement influence range of the splitting and diffusing grout veins on the injected medium in the direction of minor principal stress. The elastic modulus, Poisson's ratio, and density of the injected medium are obtained. Based on the theory of circular hole expansion, a mechanical model of the compaction effect of the split grout channel expansion on the injected medium within the effective reinforcement influence range is established.

6. The grouting design method for the elliptical final hole splitting reinforcement range in porous media as described in claim 1, characterized in that, This also includes, after determining the reinforcement range of an elliptical single-hole fracturing operation, obtaining the single-hole initiation fracturing pressure based on the magnitude of the minimum principal stress and in conjunction with hydraulic fracturing theory: ； in, To generate splitting pressure, The fracture toughness coefficient of the injected medium. The minimum principal stress in the environment in which the injected medium exists. The radius of the grouting inlet. The critical radius for splitting extension.

7. A grouting design system for reinforcing elliptical terminal hole splitting in porous media, employing the grouting design method as described in any one of claims 1-6, comprising: The data acquisition module is used to acquire tunnel surrounding rock characteristics and ground stress measurement data; The grouting analysis module is used to determine the type of grouting medium and grouting method based on the characteristics of the surrounding rock of the tunnel, and to obtain the spatial distribution of ground stress and predict the direction of grout expansion based on ground stress measurement data. The target grouting reinforcement range determination module is used to determine the elliptical single-hole splitting reinforcement range based on the spatial distribution of ground stress; the single-hole splitting reinforcement range includes the reinforcement range in the direction of maximum principal stress and the reinforcement range in the direction of minimum principal stress. The drilling parameter determination module is used to determine drilling parameters, including hole spacing, drilling inclination angle, and number of holes, based on the target grouting reinforcement range and the elliptical single-hole splitting reinforcement range.

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