A design method for advanced pre-support of pipe-roof grouting of broken ore body
By acquiring ore and grout parameters, conducting grouting tests, and constructing a micro-rock arch model, the problem of uncertain design parameters in the support of fractured ore body roadways was solved, achieving safe and efficient support design and reducing the risk of collapse.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- YILIANG CHIHONG MINING IND
- Filing Date
- 2026-02-02
- Publication Date
- 2026-05-29
Smart Images
Figure CN122113387A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of pipe roof support technology, and in particular to the design method of pipe roof grouting pre-support for fractured ore bodies. Background Technology
[0002] In the underground mining process of non-coal mines, the tunneling and support of fractured ore bodies (such as fault fracture zones, dense joint zones, or weathering and alteration zones) has always been a key technical challenge restricting the safe and efficient production of mines.
[0003] Currently, the industry mainly employs two methods for roadway support in fractured ore bodies: the I-beam frame short-excavation and short-support technique, and the combined advanced small-diameter pipe pre-support technique. The traditional I-beam frame "short-excavation and short-support" technique uses I-beam frames for immediate support immediately following the excavation face. However, due to its passive load-bearing capacity and limited support rigidity, the support range is limited to the excavated roadway and cannot pre-reinforce the unexcavated fractured rock mass ahead. The combined advanced small-diameter pipe pre-support technique involves driving multiple rows of small-diameter steel pipes obliquely outward from the roadway outline and grouting them before excavation to form a reinforced shell within a certain range. However, the small-diameter pipes have low individual rigidity and limited load-bearing capacity, resulting in a thin reinforced arch shell with poor overall integrity, making it difficult to effectively withstand the large overlying rock pressure in deep or large-section roadways. Problems such as insufficient reinforcement range and uneven grout diffusion often occur, leading to unstable pre-support effects and high costs.
[0004] In recent years, some mines have attempted to introduce advanced pre-support technology combining "large pipe roofs and grouting." This involves pre-installing one or more rows of large-diameter steel pipes in front of the working face, grouting the pipes and surrounding rock mass, so that the steel pipes and the reinforced rock mass together form a high-strength, large-span continuous load-bearing arch structure. This effectively reinforces and actively supports the structure, significantly improving support safety and permissible excavation progress. However, the core bottleneck of large pipe roof grouting technology lies in the lack of scientific, systematic, and reliable theories and methods for determining key support design parameters. The design of parameters such as the reasonable spacing of the pipe roofs, the permissible span of the pipe roofs, the required anchorage depth of the pipe roofs, and the matching grouting pressure and diffusion radius often relies on tunnel engineering experience or estimations, failing to fully consider the non-uniform improvement characteristics of the mechanical properties of the fractured ore body after grouting reinforcement, and the complex mechanical mechanism of the synergistic effect among the pipe roof, the grout-reinforced body, and the original rock.
[0005] Therefore, a systematic pre-support design method for pipe roof grouting, specifically tailored to the conditions of fractured ore bodies, is needed. By combining theoretical models with experimental verification, key design parameters can be determined to solve the support problem for safe and efficient tunneling in fractured ore bodies. Summary of the Invention
[0006] To address or partially address the problems existing in related technologies, this application provides a design method for pre-support of pipe roof grouting in fractured ore bodies, aiming to solve the problem of determining key design parameters during pre-support of pipe roof grouting.
[0007] This application provides a design method for pre-support of fractured ore body by pipe roof grouting, including: Obtain ore and rock parameters and slurry parameters, and calculate the slurry diffusion radius using a semi-empirical method; the ore and rock parameters include the permeability coefficient of the ore and rock mass, which is determined by conducting indoor permeability tests or in-situ ore and rock mass pressure tests through core sampling. Grouting tests were conducted to determine the grouting parameters and the actual grout diffusion radius. Determine the mechanical parameters of the ore and rock after grouting reinforcement. The measured mechanical parameters of the ore and rock include the internal friction angle and cohesion of the ore and rock. A calculation model for pipe roof spacing was constructed. Based on the mechanical parameters of the rock and ore after grouting reinforcement, the maximum allowable net spacing of the pipe roof was calculated. Specifically, according to the basic principle of the rock and soil arch effect, under certain conditions, the rock mass and steel pipes between the pipe roofs interact to form a rock arch, and the inner sides of the two pipe roofs become the arch feet, supporting the pressure of the overlying rock layer. A micro rock and soil arch model was constructed to calculate the maximum allowable net spacing of the pipe roof. A calculation model for the span and anchorage depth of the pipe roof was constructed. Based on the mechanical parameters of the rock and ore after grouting reinforcement, the maximum allowable span and minimum anchorage depth of the pipe roof were calculated.
[0008] Optionally, in some implementations, constructing a micro-rock arch model includes: Based on the fundamental principle of the soil arch effect, a micro-soil arch model is constructed: Based on the uniformly distributed load q acting on the arch, the axial force N at the arch crown, the horizontal reaction H at the arch foot, and the vertical reaction V are derived through static equilibrium conditions: (2) (3) In the formula, N represents the horizontal axial force at the arch crown section, H represents the horizontal reaction force at the arch foot support of the micro-soil arch, V represents the vertical upward reaction force, q represents the overburden load, l represents the distance between the centers of adjacent pipe sheds, and h represents the arch height. The arch foot reactions H and V are decomposed into directions parallel to and perpendicular to the arch foot tangent, and the local stress at the arch foot of the pipe roof is analyzed: (4) In the formula, This represents the angle between the tangent to the arch axis at point O and the horizontal direction. (5) (6) In the formula, , These represent the resultant forces of the support reaction H and the tangent at point O parallel to the arch axis and perpendicular to the arch axis, respectively. To ensure that the reaction force of the arch can be effectively transferred to the pipe roof through friction, the stable friction conditions at the arch foot of the pipe roof are as follows: (7) In the formula, This indicates the coefficient of friction between the outer side of the steel pipe and the rock mass; The strength requirements of the arch itself: (8) (9) In the formula, Indicates the maximum principal stress. Indicates the minimum principal stress. represents the internal friction angle of the rock mass, and c represents the cohesion of the rock mass; (10) In the formula, d represents the diameter of the pipe shed; This indicates the maximum principal stress at point F, which is located at the bottom of the mid-span section of the arch crown. It is the theoretical compressive strength of the rock mass under uniaxial conditions, representing the bearing capacity of the rock mass itself; (11) In the formula, This represents the maximum principal stress at point D, where D is the lower edge point of the arch foot section. It is the additional compressive stress caused by the stress state of the arch; and It must be less than or equal to the actual uniaxial compressive strength of the rock mass after grouting reinforcement; usually These are control conditions; the maximum allowable net spacing between pipe sheds is... The spacing equal to the actual uniaxial compressive strength of the rock mass after grouting reinforcement.
[0009] Optionally, in some implementations, calculating the maximum allowable net spacing of the pipe shed includes: Based on the frictional stability condition, when the horizontal thrust at the arch foot is too large, exceeding the frictional force between the steel pipe and the rock mass, the soil arch will slide and fail along the pipe roof. To ensure that the reaction force at the arch foot can be completely transferred to the pipe roof through friction, the maximum allowable net spacing of the pipe roofs should meet the following requirements: (12) Based on rock mass strength conditions, when the compressive stress on the rock mass at the arch foot exceeds its uniaxial compressive strength, the rock mass will be crushed and the soil arch will be destroyed. To ensure that the maximum principal stress of the rock mass at the arch foot does not exceed its bearing capacity, the maximum allowable net spacing of the pipe roof should meet the following requirements: (13) The final maximum allowable net spacing between pipe sheds should be: (14) Based on two different failure mechanisms, and taking into account both frictional stability and rock mass strength, the design of pipe roof support is made safe and reliable.
[0010] Optionally, in some implementations, a calculation model for the span and anchorage depth of the pipe roof is constructed, including: The anchoring section of the pipe roof must pass through the loosened and fractured zone and enter the stable rock mass. Therefore, it is necessary to estimate the horizontal development range of the plastic zone or loosened zone of the surrounding rock after the tunnel excavation. (15) In the formula, 'a' represents the excavation span. The internal friction angle of the rock mass is represented by L, and the excavation height is represented by L. Minimum anchorage depth It should be greater than the width of the fracture zone. A certain proportion, that is , Indicates the safety factor; Based on the Pasternak foundation model, a calculation model for the span and anchorage depth of the pipe roof is constructed. A single pipe roof is considered as a continuous beam supported on two different foundation layers: a grouting reinforced support section and an anchorage section in the undisturbed rock mass area. The reaction force distribution between the support section and the anchorage section is as follows: (16) (17) (18) (19) In the formula, , These represent the constraint reactions of the support section and the rock mass on the pipe roof anchorage section, respectively. This represents the vertical settlement value of the pipe roof at point x in the excavation direction. This represents the approximate curvature of the pipe roof deflection curve, reflecting the degree of bending. , It represents the ground reaction coefficient of the support section and the anchorage section, which is the reaction force required to generate a unit settlement per unit area of the foundation, reflecting the compressive stiffness of the foundation; , It represents the shear modulus of the foundation in the support section and anchorage section, and indicates the ability of the foundation per unit area to resist shear deformation; This indicates the equivalent foundation shear layer width of the support section. This indicates the equivalent width of the shear layer in the surrounding rock foundation.
[0011] Optionally, in some implementations, calculating the maximum allowable span and minimum anchorage depth of the pipe roof includes: Establish the differential equation for the control of the pipe shed, and , Substituting into the beam's equilibrium equations, we obtain the differential equations for the support section and the anchorage section respectively: Control equations for the support section: (20) Control equations for the excavation section: (twenty one) Anchorage section governing equations: (twenty two) In the formula, I represents the moment of inertia, E represents the elastic modulus, and j represents the circumferential distance between the centers of the pipe shed. The value represents the density of the overlying rock in the tunnel, and y represents the burial depth at the tunnel face. This indicates the vertical settlement value of the pipe roof support section. This indicates the vertical settlement value of the excavated section of the pipe roof. This indicates the vertical settlement value of the pipe roof in the anchoring section; By combining boundary conditions and continuity conditions, the general solutions of the three differential equations are solved respectively, and the settlement curve, bending moment and shear force distribution of the pipe roof are obtained. Maximum allowable span The maximum bending moment of the excavation section shall not exceed the allowable bending moment of the pipe roof material, and the maximum deflection at the end of the excavation section shall not exceed the allowable value; by adjusting the span Perform trial calculations to find the maximum value that satisfies the conditions. That is ; Minimum anchorage depth The anchorage section needs to be long enough so that the displacement and rotation of the far-end boundary conditions approach zero. The displacement at the end of the anchorage section must be reduced to less than 5% of the maximum displacement of the excavation section. This determines the minimum anchorage depth. .
[0012] Optionally, in some implementations, the grouting parameters and the actual grout diffusion radius parameters are determined through experiments, including: Grouting tests can be single-hole grouting tests or multi-hole grouting tests; During single-hole grouting tests, observation holes are set up based on the calculated grout diffusion radius to determine the grout diffusion radius; During the multi-hole grouting test, the spacing between the holes should be 1 to 1.2 times the diffusion radius obtained from the calculation of the grout diffusion radius.
[0013] Optionally, in some embodiments, calculating the slurry diffusion radius includes: Using semi-empirical theoretical formulas: (1) In the formula, R represents the grout diffusion radius, K represents the formation permeability coefficient, t represents the grouting time, and P represents the grouting pressure. Indicates the hole radius. Indicates the radius of the grouting pipe. The viscosity of the slurry is the ratio of its viscosity to that of water, and n represents the porosity of the ore.
[0014] The technical solution provided in this application may include the following beneficial effects: By establishing a systematic process from calculating the grout diffusion radius and verifying grouting tests to determining the mechanical parameters of the reinforced rock mass, and by innovatively constructing a micro-rock arch model and a pipe roof stress analysis model, the scientific and quantitative design of key parameters such as pipe roof spacing, span, and anchorage depth is achieved. This overcomes the blindness of traditional experience-based design, improves the reliability and safety of support, and effectively prevents the risk of collapse during the excavation of fractured ore bodies. It provides a standardized design solution that is replicable and scalable for the support of roadways in fractured ore bodies in non-coal mines.
[0015] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description
[0016] The above and other objects, features and advantages of this application will become more apparent from the more detailed description of exemplary embodiments thereof in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments thereof.
[0017] Figure 1 This is a schematic flowchart illustrating the pre-support design method for pipe roof grouting in fractured ore bodies, as shown in the embodiments of this application. Figure 2 This is a schematic diagram of the water pressure test device for the pre-support design method of pipe roof grouting in fractured ore bodies, as shown in the embodiments of this application. Figure 3 This is a schematic diagram of the micro-rock arch model of the pre-support design method for pipe roof grouting in fractured ore bodies, as shown in the embodiments of this application. Figure 4 This is a schematic diagram of the stress analysis of the micro-rock arch in the pre-support design method of pipe roof grouting for fractured ore bodies, as shown in the embodiments of this application. Figure 5This is a theoretical analysis model of the pipe roof after excavation in the pre-support design method of pipe roof grouting for fractured ore bodies shown in the embodiments of this application; Figure 6 This is a model of the span and anchorage depth of the pipe roof grouting advanced pre-support design method for fractured ore bodies shown in the embodiments of this application.
[0018] Attached reference numerals: 1-Water tank, 2-First pipeline, 3-Pressing device, 4-Second pipeline, 5-Pressure gauge, 6-Drill hole, 7-Water stop plug, 8-Test section. Detailed Implementation
[0019] Embodiments of this application will now be described in more detail with reference to the accompanying drawings. While embodiments of this application are shown in the drawings, it should be understood that this application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make this application more thorough and complete, and to fully convey the scope of this application to those skilled in the art.
[0020] In recent years, some mines have attempted to introduce advanced pre-support technology combining "large pipe roofs and grouting." This involves pre-installing one or more rows of large-diameter steel pipes in front of the working face, grouting the pipes and surrounding rock mass, so that the steel pipes and the reinforced rock mass together form a high-strength, large-span continuous load-bearing arch structure. This effectively reinforces and actively supports the structure, significantly improving support safety and permissible excavation progress. However, the core bottleneck of large pipe roof grouting technology lies in the lack of scientific, systematic, and reliable theories and methods for determining key support design parameters. The design of parameters such as the reasonable spacing of the pipe roofs, the permissible span of the pipe roofs, the required anchorage depth of the pipe roofs, and the matching grouting pressure and diffusion radius often relies on tunnel engineering experience or estimations, failing to fully consider the non-uniform improvement characteristics of the mechanical properties of the fractured ore body after grouting reinforcement, and the complex mechanical mechanism of the synergistic effect among the pipe roof, the grout-reinforced body, and the original rock.
[0021] To address the aforementioned issues, this application provides a design method for pre-support of fractured ore bodies using pipe roof grouting. This method establishes a systematic process from calculating the grout diffusion radius and verifying it through grouting tests to determining the mechanical parameters of the reinforced rock mass. It also innovatively constructs a micro-rock arch model and a pipe roof-based stress analysis model, enabling the scientific and quantitative design of key parameters such as pipe roof spacing, span, and anchorage depth. This overcomes the blindness of traditional experience-based design, improves the reliability and safety of the support, and effectively prevents the risk of collapse during the excavation of fractured ore bodies. It provides a replicable and scalable standardized design solution for the support of fractured ore body roadways in non-coal mines.
[0022] The technical solutions of the embodiments of this application are described in detail below with reference to the accompanying drawings.
[0023] Figure 1 This is a schematic flowchart illustrating the pre-support design method for pipe roof grouting in fractured ore bodies, as shown in the embodiments of this application.
[0024] See Figure 1 A design method for pre-support of fractured ore body by pipe roof grouting includes: S101. Obtain ore and rock parameters and slurry parameters, and calculate the slurry diffusion radius using a semi-empirical method; Ore and rock parameters include the permeability coefficient of the ore and rock mass, which is determined through core sampling and laboratory permeability testing or in-situ pressure water testing of the ore and rock mass. When the permeability coefficient of the ore and rock mass is determined through in-situ pressure water testing, the in-situ pressure water testing is as follows: Figure 2 As shown, a test hole was drilled to the target depth at the predetermined location, and the borehole 6 was flushed to remove rock powder and ensure that the test section borehole wall was clean.
[0025] The water-stop plug 7 is lowered to a predetermined depth, usually a certain distance from the bottom of the hole, and then inflated or mechanically pressurized to expand it, tightly fitting the hole wall, thereby sealing and dividing the borehole 6 into an upper non-test section and a lower test section 8.
[0026] Staged pressurization and flow measurement were performed using a water pressure device 3, employing a three-stage, five-phase pressurization method (P1→P2→P3→P2→P1) to eliminate hysteresis effects. At each pressure level, pressure was continuously applied until the injected flow rate stabilized, requiring flow fluctuations to be less than 10% of the average value. The stable pressure at each stage and its corresponding stable flow rate were recorded.
[0027] Based on parameters such as stable flow rate, test pressure, and test section length L, the permeability of the rock mass is calculated. Its physical meaning is the amount of water per minute per meter of test section under a pressure of 1 MPa.
[0028] Subsequently, the permeability is converted into the permeability coefficient based on empirical formulas or related relationships.
[0029] Specifically, the slurry diffusion radius is calculated using a semi-empirical theoretical formula: (1) In the formula, R represents the grout diffusion radius, K represents the formation permeability coefficient, t represents the grouting time, and P represents the grouting pressure. Indicates the hole radius. Indicates the radius of the grouting pipe. The viscosity of the slurry is the ratio of its viscosity to that of water, and n represents the porosity of the ore.
[0030] S102. Conduct grouting tests to determine grouting parameters and actual grout diffusion radius parameters. Specifically, the grouting parameters and the actual grout diffusion radius parameters are determined through experiments, including: Grouting tests can be single-hole grouting tests or multi-hole grouting tests; During single-hole grouting tests, observation holes are set up based on the calculated grout diffusion radius to determine the grout diffusion radius; During the multi-hole grouting test, the spacing between the holes should be 1 to 1.2 times the diffusion radius obtained from the calculation of the grout diffusion radius.
[0031] S103. Determine the mechanical parameters of the ore and rock after grouting reinforcement. The measured mechanical parameters of the ore and rock include the internal friction angle and cohesion of the ore and rock. Methods for determining the mechanical parameters of minerals and rocks include coring for indoor testing or conducting in-situ testing. The main mechanical parameters to be measured include the internal friction angle and cohesion of the minerals and rocks.
[0032] S104. Construct a calculation model for pipe roof spacing, and calculate the maximum allowable net spacing of pipe roofs based on the mechanical parameters of the rock and ore after grouting reinforcement. Specifically, based on the fundamental principle of the soil arching effect, a micro-soil arch model is constructed: like Figure 3 , 4 As shown in Figure 5, based on the uniformly distributed load q acting on the arch, the axial force N at the arch crown, the horizontal reaction H at the arch foot, and the vertical reaction V are derived through static equilibrium conditions: (2) (3) In the formula, N represents the horizontal axial force at the arch crown section, H represents the horizontal reaction force at the arch foot support of the micro-soil arch, V represents the vertical upward reaction force, q represents the overburden load, l represents the distance between the centers of adjacent pipe sheds, and h represents the arch height. The arch foot reactions H and V are decomposed into directions parallel to and perpendicular to the arch foot tangent, and the local stress at the arch foot of the pipe roof is analyzed: (4) In the formula, This represents the angle between the tangent to the arch axis at point O and the horizontal direction. (5) (6) In the formula, , These represent the resultant forces of the support reaction H and the tangent at point O parallel to the arch axis and perpendicular to the arch axis, respectively. To ensure that the reaction force of the arch can be effectively transferred to the pipe roof through friction, the stable friction conditions at the arch foot of the pipe roof are as follows: (7) In the formula, This indicates the coefficient of friction between the outer side of the steel pipe and the rock mass; The strength requirements of the arch itself: (8) (9) In the formula, Indicates the maximum principal stress. Indicates the minimum principal stress. represents the internal friction angle of the rock mass, and c represents the cohesion of the rock mass; (10) In the formula, d represents the diameter of the pipe shed; This indicates the maximum principal stress at point F, which is located at the bottom of the mid-span section of the arch crown. It is the theoretical compressive strength of the rock mass under uniaxial conditions, representing the bearing capacity of the rock mass itself; (11) In the formula, This represents the maximum principal stress at point D, where D is the lower edge point of the arch foot section. It is the additional compressive stress caused by the stress state of the arch; and It must be less than or equal to the actual uniaxial compressive strength of the rock mass after grouting reinforcement; usually These are control conditions; the maximum allowable net spacing between pipe sheds is... The spacing equal to the actual uniaxial compressive strength of the rock mass after grouting reinforcement.
[0033] The calculation of the maximum allowable net spacing of the pipe roof includes considerations based on frictional stability conditions. When the horizontal thrust at the arch foot is too large, exceeding the frictional force between the steel pipe and the rock mass, the soil arch will slide and fail along the pipe roof. To ensure that the reaction force at the arch foot can be completely transferred to the pipe roof through friction, the maximum allowable net spacing of the pipe roof should meet the following requirements: (12) Based on rock mass strength conditions, when the compressive stress on the rock mass at the arch foot exceeds its uniaxial compressive strength, the rock mass will be crushed and the soil arch will be destroyed. To ensure that the maximum principal stress of the rock mass at the arch foot does not exceed its bearing capacity, the maximum allowable net spacing of the pipe roof should meet the following requirements: (13) The final maximum allowable net spacing between pipe sheds should be: (14) Based on two different failure mechanisms, and taking into account both frictional stability and rock mass strength, the design of pipe roof support is made safe and reliable.
[0034] S105. Construct a calculation model for the span and anchorage depth of the pipe roof. Based on the mechanical parameters of the rock and ore after grouting reinforcement, calculate the maximum allowable span and minimum anchorage depth of the pipe roof.
[0035] Specifically, a calculation model for the span and anchorage depth of the pipe roof is constructed, including: like Figure 6 As shown, the anchoring section of the pipe roof must pass through the loosened and fractured zone and enter the stable rock mass. Therefore, it is necessary to estimate the horizontal development range of the plastic zone or loosened zone of the surrounding rock after the tunnel excavation. (15) In the formula, 'a' represents the excavation span. The internal friction angle of the rock mass is represented by L, and the excavation height is represented by L. Minimum anchorage depth It should be greater than the width of the fracture zone. A certain proportion, that is , Indicates the safety factor; Based on the Pasternak foundation model, a calculation model for the span and anchorage depth of the pipe roof is constructed. A single pipe roof is considered as a continuous beam supported on two different foundation layers: a grouting reinforced support section and an anchorage section in the undisturbed rock mass area. The reaction force distribution between the support section and the anchorage section is as follows: (16) (17) (18) (19) In the formula, , These represent the constraint reactions of the support section and the rock mass on the pipe roof anchorage section, respectively. This represents the vertical settlement value of the pipe roof at point x in the excavation direction. This represents the approximate curvature of the pipe roof deflection curve, reflecting the degree of bending. , It represents the ground reaction coefficient of the support section and the anchorage section, which is the reaction force required to generate a unit settlement per unit area of the foundation, reflecting the compressive stiffness of the foundation; , It represents the shear modulus of the foundation in the support section and anchorage section, and indicates the ability of the foundation per unit area to resist shear deformation; This indicates the equivalent foundation shear layer width of the support section. This indicates the equivalent width of the shear layer in the surrounding rock foundation.
[0036] Calculate the maximum allowable span and minimum anchorage depth of the pipe roof, including: Establish the differential equation for the control of the pipe shed, and , Substituting into the beam's equilibrium equations, we obtain the differential equations for the support section and the anchorage section respectively: Control equations for the support section: (20) Control equations for the excavation section: (twenty one) Anchorage section governing equations: (twenty two) In the formula, I represents the moment of inertia, E represents the elastic modulus, and j represents the circumferential distance between the centers of the pipe shed. The value represents the density of the overlying rock in the tunnel, and y represents the burial depth at the tunnel face. This indicates the vertical settlement value of the pipe roof support section. This indicates the vertical settlement value of the excavated section of the pipe roof. This indicates the vertical settlement value of the pipe roof in the anchoring section; By combining boundary conditions and continuity conditions, the general solutions of the three differential equations are solved respectively, and the settlement curve, bending moment and shear force distribution of the pipe roof are obtained. Maximum allowable span The maximum bending moment of the excavation section shall not exceed the allowable bending moment of the pipe roof material, and the maximum deflection at the end of the excavation section shall not exceed the allowable value; by adjusting the span Perform trial calculations to find the maximum value that satisfies the conditions. That is ; Minimum anchorage depth The anchorage section needs to be long enough so that the displacement and rotation of the far-end boundary conditions approach zero. The displacement at the end of the anchorage section must be reduced to less than 5% of the maximum displacement of the excavation section. This determines the minimum anchorage depth. .
[0037] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.
Claims
1. A design method for pre-support of fractured ore body using pipe roof grouting, characterized in that, include: Obtain ore and rock parameters and slurry parameters, and calculate the slurry diffusion radius using a semi-empirical method; the ore and rock parameters include the permeability coefficient of the ore and rock mass, which is determined by conducting indoor permeability tests or in-situ ore and rock mass pressure tests through core sampling. Grouting tests were conducted to determine the grouting parameters and the actual grout diffusion radius. Determine the mechanical parameters of the ore and rock after grouting reinforcement. The measured mechanical parameters of the ore and rock include the internal friction angle and cohesion of the ore and rock. A calculation model for pipe roof spacing was constructed. Based on the mechanical parameters of the rock and ore after grouting reinforcement, the maximum allowable net spacing of the pipe roof was calculated. Specifically, according to the basic principle of the rock and soil arch effect, under certain conditions, the rock mass and steel pipes between the pipe roofs interact to form a rock arch, and the inner sides of the two pipe roofs become the arch feet, supporting the pressure of the overlying rock layer. A micro rock and soil arch model was constructed to calculate the maximum allowable net spacing of the pipe roof. A calculation model for the span and anchorage depth of the pipe roof was constructed. Based on the mechanical parameters of the rock and ore after grouting reinforcement, the maximum allowable span and minimum anchorage depth of the pipe roof were calculated.
2. The design method for pre-support of fractured ore body pipe roof grouting according to claim 1, characterized in that, The construction of the micro-rock and soil arch model includes: Based on the fundamental principle of the soil arching effect, a micro-soil arch model is constructed: Based on the uniformly distributed load q acting on the arch, the axial force N at the arch crown, the horizontal reaction H at the arch foot, and the vertical reaction V are derived through static equilibrium conditions: （2） （3） In the formula, N represents the horizontal axial force at the arch crown section, H represents the horizontal reaction force at the arch foot support of the micro-soil arch, V represents the vertical upward reaction force, q represents the overburden load, l represents the distance between the centers of adjacent pipe sheds, and h represents the arch height. The arch foot reactions H and V are decomposed into directions parallel to and perpendicular to the arch foot tangent, and the local stress at the arch foot of the pipe roof is analyzed: （4） In the formula, This represents the angle between the tangent to the arch axis at point O and the horizontal direction. （5） （6） In the formula, , These represent the resultant forces of the support reaction H and the tangent at point O parallel to the arch axis and perpendicular to the arch axis, respectively. To ensure that the reaction force of the arch can be effectively transferred to the pipe roof through friction, the stable friction conditions at the arch foot of the pipe roof are as follows: （7） In the formula, This indicates the coefficient of friction between the outer side of the steel pipe and the rock mass; The strength requirements of the arch itself: （8） （9） In the formula, Indicates the maximum principal stress. Indicates the minimum principal stress. represents the internal friction angle of the rock mass, and c represents the cohesion of the rock mass; （10） In the formula, d represents the diameter of the pipe shed; This indicates the maximum principal stress at point F, which is located at the bottom of the mid-span section of the arch crown. It is the theoretical compressive strength of the rock mass under uniaxial conditions, representing the bearing capacity of the rock mass itself; （11） In the formula, This represents the maximum principal stress at point D, where D is the lower edge point of the arch foot section. It is the additional compressive stress caused by the stress state of the arch; and It must be less than or equal to the actual uniaxial compressive strength of the rock mass after grouting reinforcement; usually These are control conditions; the maximum allowable net spacing between pipe sheds is... The spacing equal to the actual uniaxial compressive strength of the rock mass after grouting reinforcement.
3. The pre-support design method for pipe roof grouting in fractured ore bodies according to claim 1, characterized in that, The calculation of the maximum allowable net spacing of the pipe shed includes: Based on the frictional stability condition, when the horizontal thrust at the arch foot is too large, exceeding the frictional force between the steel pipe and the rock mass, the soil arch will slide and fail along the pipe roof. To ensure that the reaction force at the arch foot can be completely transferred to the pipe roof through friction, the maximum allowable net spacing of the pipe roofs should meet the following requirements: （12） Based on rock mass strength conditions, when the compressive stress on the rock mass at the arch foot exceeds its uniaxial compressive strength, the rock mass will be crushed and the soil arch will be destroyed. To ensure that the maximum principal stress of the rock mass at the arch foot does not exceed its bearing capacity, the maximum allowable net spacing of the pipe roof should meet the following requirements: （13） The final maximum allowable net spacing between pipe sheds should be: （14） Based on two different failure mechanisms, and taking into account both frictional stability and rock mass strength, the design of pipe roof support is made safe and reliable.
4. The design method for pre-support of fractured ore body pipe roof grouting according to claim 1, characterized in that, The calculation model for the span and anchorage depth of the pipe roof includes: The anchoring section of the pipe roof must pass through the loosened and fractured zone and enter the stable rock mass. Therefore, it is necessary to estimate the horizontal development range of the plastic zone or loosened zone of the surrounding rock after the tunnel excavation. （15） In the formula, 'a' represents the excavation span. The internal friction angle of the rock mass is represented by L, and the excavation height is represented by L. Minimum anchorage depth It should be greater than the width of the fracture zone. A certain proportion, that is , Indicates the safety factor; Based on the Pasternak foundation model, a calculation model for the span and anchorage depth of the pipe roof is constructed. A single pipe roof is considered as a continuous beam supported on two different foundation layers: a grouting reinforced support section and an anchorage section in the undisturbed rock mass area. The reaction force distribution between the support section and the anchorage section is as follows: （16） （17） （18） （19） In the formula, , These represent the constraint reactions of the support section and the rock mass on the pipe roof anchorage section, respectively. This represents the vertical settlement value of the pipe roof at point x in the excavation direction. This represents the approximate curvature of the pipe roof deflection curve, reflecting the degree of bending. , It represents the ground reaction coefficient of the support section and the anchorage section, which is the reaction force required to generate a unit settlement per unit area of the foundation, reflecting the compressive stiffness of the foundation; , It represents the shear modulus of the foundation in the support section and anchorage section, and indicates the ability of the foundation per unit area to resist shear deformation; This indicates the width of the equivalent foundation shear layer of the support section. This indicates the equivalent width of the shear layer in the surrounding rock foundation.
5. The design method for pre-support of fractured ore body pipe roof grouting according to claim 1, characterized in that, The calculation of the maximum allowable span and minimum anchorage depth of the pipe roof includes: Establish the differential equation for the control of the pipe shed, and , Substituting into the beam's equilibrium equations, we obtain the differential equations for the support section and the anchorage section respectively: Control equations for the support section: （20） Control equations for the excavation section: （21） Anchorage section governing equations: （22） In the formula, I represents the moment of inertia, E represents the elastic modulus, and j represents the circumferential distance between the centers of the pipe shed. The value represents the density of the overlying rock in the tunnel, and y represents the burial depth at the tunnel face. This indicates the vertical settlement value of the pipe roof support section. This indicates the vertical settlement value of the excavated section of the pipe roof. This indicates the vertical settlement value of the pipe roof in the anchoring section; By combining boundary conditions and continuity conditions, the general solutions of the three differential equations are solved respectively, and the settlement curve, bending moment and shear force distribution of the pipe roof are obtained. Maximum allowable span The maximum bending moment of the excavation section shall not exceed the allowable bending moment of the pipe roof material, and the maximum deflection at the end of the excavation section shall not exceed the allowable value; by adjusting the span Perform trial calculations to find the maximum value that satisfies the conditions. That is ; Minimum anchorage depth The anchorage section needs to be long enough so that the displacement and rotation of the far-end boundary conditions approach zero. The displacement at the end of the anchorage section must be reduced to less than 5% of the maximum displacement of the excavation section. This determines the minimum anchorage depth. .
6. The design method for pre-support of fractured ore body pipe roof grouting according to claim 1, characterized in that, The determination of grouting parameters and actual grout diffusion radius parameters through experiments includes: Grouting tests can be single-hole grouting tests or multi-hole grouting tests; During single-hole grouting tests, observation holes are set up according to the calculated grout diffusion radius to determine the grout diffusion radius; During the multi-hole grouting test, the spacing between the holes is 1 to 1.2 times the diffusion radius obtained from the calculation of the grout diffusion radius.
7. The design method for pre-support of fractured ore body pipe roof grouting according to claim 1, characterized in that, The calculation of the slurry diffusion radius includes: Using semi-empirical theoretical formulas: （） In the formula, R represents the grout diffusion radius, K represents the formation permeability coefficient, t represents the grouting time, and P represents the grouting pressure. Indicates the hole radius. Indicates the radius of the grouting pipe. The viscosity of the slurry is the ratio of its viscosity to that of water, and n represents the porosity of the ore.