A method for calculating the stability of a fast-excavation coal roadway anchor rod and anchor cable supporting roof partition

Abstract

A method for calculating the zonal stability of roof support using anchor bolts and cables in fast-excavation coal roadways belongs to the field of coal mine roadway support and surrounding rock stability control technology. The method involves acquiring rock physical and mechanical parameters and applying in-situ stress and support; calculating the loads on anchor bolts and cables separately; adaptively dividing the roof into zones along the roadway width using gradients; calculating the support effectiveness of each zone based on the load, deformation, anchoring influence coefficient, and redundancy coefficient of the anchor bolts and cables; calculating the unit released energy by multiplying the difference in energy density between the elastic and plastic stages by the unit volume, and summing the regional released energy for both supported and unsupported conditions; using the difference in released energy between unsupported and supported conditions as the support suppression energy; defining the support effectiveness index as the ratio of support effectiveness to released energy with support; combining current classification, evolution trend, trend prediction, and dynamic evaluation of classification migration; and determining reinforcement priority based on the proportion of released energy. This method can accurately reflect the stability differences of different areas of the roof under partial support conditions.

Description

Technical Field

[0001] This invention belongs to the field of coal mine roadway support and surrounding rock stability control technology, specifically relating to a method for calculating the zonal stability of the roof supported by anchor bolts and anchor cables in fast-excavation coal roadways. Background Technology

[0002] With the continuous increase in coal mining depth and intensity, rapid tunneling technology has been continuously developed, and rapid tunneling equipment such as integrated roadheader-bolt machines have been widely used, significantly improving the efficiency of coal roadway excavation. Rock bolt support, as the main form of coal roadway support, is increasingly widely used. However, under rapid tunneling conditions, the problem of roof and surrounding rock stability control has become increasingly prominent, and the support process has become a key factor restricting rapid coal roadway excavation.

[0003] During rapid tunneling, due to the time difference between the tunneling speed and the support construction process, the roof within a certain range behind the working face is partially supported by anchor bolts. The surrounding rock of the roof undergoes a dynamic transformation from unsupported to partially supported to fully supported, and its bearing capacity gradually transitions from an unsupported state to a stable bearing state. The stability of the roof under this partially supported state is the core challenge for safety control in rapid tunneling coal roadways.

[0004] Existing anchor bolt support design theories mainly include suspension theory, composite beam theory, and reinforced arch theory, among which suspension theory is the most widely used. The core idea of ​​suspension theory is to suspend the unstable lower rock strata to the stable upper rock strata using anchor bolts. However, suspension theory is mainly based on the overall suspension assumption, treating the roof as a whole for suspension calculations. It does not consider the bearing differences of different areas of the roof surrounding rock during rapid tunneling, nor the range of action of anchor bolt support, nor does it fully consider the local bearing capacity of the installed anchor bolts under partial support conditions. Furthermore, existing methods do not quantitatively evaluate the interaction between support and surrounding rock from an energy perspective, making it difficult to reflect the inhibitory effect of support on the energy release of surrounding rock. This leads to conservative calculation results for roof stability under partial support conditions, which do not match the actual bearing capacity of the roof, making it difficult to provide accurate quantitative basis for the design of roof support in rapid coal roadways.

[0005] Therefore, it is urgent to propose a calculation method that can quantitatively and qualitatively evaluate the stability of different regions of the roof in fast-excavating coal roadways and its evolution over time, and to determine the priority of reinforcement support for each region of the roof based on this method, so as to accurately reflect the stability differences of different regions of the roof under partial support conditions and provide a scientific basis for the design and construction of roof support in fast-excavating coal roadways. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a method for calculating the zonal stability of the roof supported by anchor bolts and anchor cables in fast-excavating coal roadways. This method achieves quantitative and qualitative evaluation of the zonal stability of the roof in fast-excavating coal roadways from the perspectives of energy efficiency and time-varying evolution, and can accurately reflect the stability differences of different areas of the roof under partial support conditions and their evolution over time.

[0007] To achieve the above objectives, the present invention provides a method for calculating the zonal stability of roof support using anchor bolts and anchor cables in fast-excavation coal roadways, comprising the following steps:

[0008] Step 1: Obtain on-site rock samples, test the basic physical and mechanical parameters of the rocks, and use FLAC. 3D Numerical simulation software is used to model coal mine roadways based on actual on-site engineering conditions, apply ground stress, and provide support for different areas of the roof.

[0009] Step 2: Calculate the anchor load based on the stress monitored by the anchor tray and the tray area;

[0010] Step 3: Calculate the anchor cable load based on the stress monitored by the anchor cable tray and the tray area;

[0011] Step 4: Adaptively divide the roof area according to the gradient distribution of energy density released by plastic failure along the width direction to obtain multiple roof partitions;

[0012] Step 5: In the multi-factor support effectiveness model, calculate the support effectiveness of the anchor bolts and anchor cables in each area of ​​the roof slab based on the anchor bolt and anchor cable load, deformation, anchorage influence coefficient and redundancy coefficient.

[0013] Step 6: Multiply the difference in energy density between the elastic stage and the plastic stage by the unit volume to obtain the energy released by the plastic failure of the surrounding rock unit in each area of ​​the roadway roof.

[0014] Step 7: Sum the released energy of all plastic failure units in each area of ​​the roadway roof under both supported and unsupported conditions.

[0015] Step 8: The difference between the energy released by unsupported and supported structures is taken as the support suppression energy. The ratio of support effectiveness to the energy released by supported structures is defined as the support effect index. Based on the support effect index, the support status of each area of ​​the roof is statically graded and evaluated.

[0016] Step 9: Considering the decay of anchor bolt and anchor cable preload over time and the evolution of surrounding rock energy release over time, establish a time-varying support effect index, and dynamically evaluate the stability of the roof based on the current classification, evolution trend, trend prediction and classification migration.

[0017] Step 10: Use the proportion of energy released in each region to reflect the degree of plastic damage in each region, and determine the reinforcement priority accordingly.

[0018] As a preferred option, in step 1, the process of obtaining on-site rock samples and testing the basic physical and mechanical parameters of the rocks is as follows:

[0019] S11: Obtain the unit parameters of the top strata in both the elastic and plastic stages, including the maximum principal stress in the plastic stage. Intermediate principal stresses during the plastic stage Minimum principal stress during the plastic stage Maximum principal stress in the elastic stage Intermediate principal stress in the elastic stage Minimum principal stress in the elastic stage Poisson's ratio of surrounding rock Elastic modulus of surrounding rock and the volume of each surrounding rock unit. ;

[0020] S12: Obtain the stress at four monitoring points on the anchor plate respectively. , , , Maximum deformation of anchor bolt Anchor bolt anchorage length Spacing between anchor bolts The stress at four monitoring points on the anchor cable tray was obtained respectively. , , , Maximum deformation of anchor cable Anchor cable anchorage length Spacing between anchor cables .

[0021] As a preferred embodiment, in step 2, the prestressed anchor load after excavation equilibrium is calculated according to the following formula. :

[0022]

[0023] In the formula, For the length of the tray, For the width of the tray;

[0024] In step 3, the prestressed anchor cable load after excavation equilibrium is calculated according to the following formula. :

[0025] .

[0026] As a preferred embodiment, in step 4, the process of adaptively dividing the roof region based on the gradient distribution of the energy density released by plastic failure along the roadway width is as follows:

[0027] S41: Calculate the energy density released during plastic failure of each surrounding rock element:

[0028] Calculate the first according to the following formula. Energy density of a surrounding rock unit in the elastic stage :

[0029]

[0030] In the formula, Indicates the elastic phase. Number the surrounding rock units of the roof;

[0031] Calculate the first according to the following formula. Energy density of a surrounding rock unit during the plastic stage :

[0032]

[0033] In the formula, Indicates the plastic stage;

[0034] The following formula yields the first... Energy density released during plastic failure of each surrounding rock unit :

[0035]

[0036] This yields the energy density distribution of plastic failure released by the roof along the width of the roadway;

[0037] S42: Calculate the gradient of the energy density released by plastic failure along the width direction, and use the gradient magnitude to reflect the degree of drastic change of the energy density released by plastic failure along the width direction;

[0038] S43: Using the peak or abrupt change in the energy density gradient released during plastic failure as the partition boundary, the number of top plate partitions and the location of each partition boundary are adaptively determined to obtain the top plate region. .

[0039] As a preferred embodiment, in step 5, the support effectiveness of the anchor bolts and anchor cables in each region of the roof is calculated according to the following formula. :

[0040]

[0041] In the formula, Number the top slab area. This represents the number of anchor bolts in the area. The number of anchor cables in the area. This is the anchorage influence coefficient of the anchor bolt. This is the anchorage influence coefficient of the anchor cable. , These are the margin coefficients for anchor bolts and anchor cables, respectively.

[0042] As a preferred option, in step 6, the energy released by plastic failure of the surrounding rock unit in each area of ​​the roadway roof is calculated according to the following formula. :

[0043]

[0044] In the formula, For the first The volume of a plastically fractured surrounding rock unit.

[0045] As a preferred embodiment, in step 7, the energy released by plastic failure in each region of the roadway roof under supported conditions is calculated according to the following formula. :

[0046]

[0047] In the formula, This represents the number of units in which the surrounding rock of the roof undergoes plastic failure. For the roof under supported conditions Plastic failure in the region releases energy;

[0048] Meanwhile, the energy released by plastic failure in each region of the roadway roof under unsupported conditions is calculated using the following formula. :

[0049]

[0050] In the formula, Roof under unsupported excavation conditions The number of elements in the region that undergo plastic failure. For the first unsupported excavation conditions The energy released by each plastic failure unit, via FLAC 3D Data obtained from unsupported excavation simulation.

[0051] As a preferred option, the process of statically classifying and evaluating the support status of each area of ​​the roof in step 8 is as follows:

[0052] S81: Calculate the suppression energy of the roof support in each area according to the following formula. :

[0053]

[0054] In the formula, For the top plate Regional support suppresses energy;

[0055] S82: Calculate the support effectiveness index for each area of ​​the roof slab according to the following formula. :

[0056]

[0057] S83: Based on the support effectiveness index The support condition is graded and evaluated:

[0058] when If the area is considered a danger zone, suggestions should be made to increase the number of anchor bolts or install additional anchor cables; when When the area is in a basically stable zone, suggestions are provided to increase the preload of anchor bolts or cables, increase the length of anchor bolts or cables, or adjust the anchorage length; when The current period is in a stable zone, and no additional support is required. It is recommended to maintain the original support scheme.

[0059] As a preferred embodiment, the process of dynamically evaluating the stability of the roof in step 9 is as follows:

[0060] S91: Establishing a time-varying support effectiveness index ,in To account for the time-varying support effectiveness after preload loss, ,in , To account for the time-varying loads on anchor bolts and cables after the preload decays, , These are the time-varying deformations of the anchor bolt and anchor cable, respectively. To pass FLAC 3D Time-varying energy release obtained from rheological or creep analysis;

[0061] S92: Based on the time-varying support effectiveness index Conduct dynamic evaluation:

[0062] At the current moment The current support status level is determined by comparing it with the grading threshold; calculation rate of decrease over time and descent acceleration Analyze the attenuation trend of support effectiveness; based on the current and its rate of decline predict Time required to drop to the next grade threshold ,when Less than the preset warning time Timely issuance of reinforcement warnings; tracking The process of crossing the grading threshold triggers corresponding reinforcement measures when the grading level drops from a high level to a low level.

[0063] As a preferred option, the process of determining the reinforcement priority in step 10 is as follows:

[0064] S101: Calculate the energy contribution rate of plastic failure in each region of the top plate according to the following formula. :

[0065]

[0066] In the formula, For the top plate Regional plastic failure releases energy. The sum of energy released in each region;

[0067] S102: Based on the contribution rate of plastic failure energy in each region of the top plate The size determines the priority of the reinforcement support area.

[0068] This invention addresses the challenges of accurately evaluating roof stability under partial support conditions in rapidly excavated coal roadways and the failure of existing suspension theories to consider regional bearing capacity differences and energy interactions. Through the collaborative design of adaptive zoning, multi-factor support effectiveness, support suppression energy, support energy efficiency, time-varying evaluation, and energy contribution rate, it achieves quantitative and qualitative evaluation of roof zone stability, offering the following beneficial effects:

[0069] 1. The roof region is adaptively divided based on the gradient of energy density released during plastic failure, and the zoning has a clear physical basis. Compared with existing methods that treat the roof as a whole or artificially fixed zoning, this invention adaptively determines the zoning boundary based on the gradient of energy density released during plastic failure of the surrounding rock (i.e., the difference in energy density between the elastic and plastic stages) along the width of the roadway. This can accurately reflect the differences in the bearing state of different areas of the roof and overcome the shortcomings of the overall suspension assumption.

[0070] 2. This invention quantifies the support effect from an energy perspective by using support suppression energy, support effectiveness index, and support energy efficiency. It introduces a no-support control, defining support suppression energy as the difference between the energy released by no support and support, defining the support effectiveness index (used for stability grading) as support effectiveness / support released energy, and defining support energy efficiency as support suppression energy / support effectiveness. This quantifies the support effect from the perspective of energy release suppressed per unit of support effectiveness, thus overcoming the deficiency of existing methods that do not evaluate the interaction between support and surrounding rock from an energy perspective.

[0071] 3. By considering the anchoring mechanism through a multi-factor support effectiveness model, the local bearing capacity under partial support conditions is reflected. This invention introduces an anchoring influence coefficient into the support effectiveness, considering the influence of anchoring length and spacing, which can reflect the local bearing capacity of the installed anchors (cables), making the calculation of roof stability under partial support conditions more consistent with reality.

[0072] 4. Dynamic evaluation of roof stability through time-varying support effectiveness index. This invention considers the evolution of anchor (cable) preload decay and surrounding rock energy release over time, establishes a time-varying support effectiveness index, and performs dynamic evaluation by combining current grading, evolution trend, trend prediction, and grading migration. This enables early warning of support effectiveness decay, prediction of grading degradation time, and evaluation of the long-term evolution law of roof stability, thus making up for the shortcomings of existing static evaluation methods.

[0073] 5. Determining reinforcement priority based on energy contribution rate provides a direct basis for support design and construction. This invention uses the energy contribution rate of plastic failure in each zone to determine reinforcement priority, enabling support design and construction to prioritize reinforcement in areas with concentrated energy release, thereby improving the targeting and economy of the support.

[0074] This method achieves quantitative and qualitative evaluation of the zonal stability of the roof in fast-excavation coal roadways from the perspectives of energy efficiency and time-varying evolution. It can reflect the stability differences of different areas of the roof under partial support conditions and their evolution over time. It can solve the problems of traditional anchor bolt support design methods that do not consider the zonal bearing characteristics of the surrounding rock under rapid excavation conditions, resulting in insufficient targeting of support parameter design and inaccurate evaluation of roof stability. It provides a quantitative basis for the design and construction of roof support in fast-excavation coal roadways. Attached Figure Description

[0075] Figure 1 This is a flowchart of the present invention;

[0076] Figure 2 Schematic diagram of energy release with / without support, support inhibition energy, and support effectiveness;

[0077] Figure 3 This is a schematic diagram of the anchor bolt structure in the timely support zone during rapid excavation roadway support according to an embodiment of the present invention;

[0078] Figure 4 This is a schematic diagram of the anchor bolt and anchor cable structure in the permanent anchoring zone of the rapid excavation roadway support according to an embodiment of the present invention;

[0079] Figure 5 This is a schematic diagram showing the arrangement of anchor tray measuring points and the change of measuring point stress with the number of running steps in the rapid excavation roadway support of this invention.

[0080] Figure 6 This is a schematic diagram showing the arrangement of anchor cable tray measuring points and the change of measuring point stress with the number of running steps in the rapid excavation roadway support of this invention.

[0081] Figure 7 This is a comparison diagram of the energy released by the failure of the plastic zone of the surrounding rock in each section of the roof in the fast-excavation roadway support according to an embodiment of the present invention, and the roof support efficiency.

[0082] Figure 8This is a comparison diagram of the energy released during the failure of the plastic zone of the surrounding rock in each section of the roof in the permanent anchoring zone of the quick-excavation roadway support according to an embodiment of the present invention, and the roof support effectiveness.

[0083] Figure 9 This is a comparison chart of the support effect index of each zone of the roof in the timely support zone and the permanent anchoring zone in the rapid excavation roadway support of this invention;

[0084] Figure 10 This represents the contribution rate of energy released by plastic failure of the surrounding rock in each zone of the roof during the rapid excavation tunnel support in this embodiment of the invention. Detailed Implementation

[0085] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. These embodiments are merely one of the preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention.

[0086] like Figure 1 As shown, this invention provides a method for calculating the zonal stability of roof support using anchor bolts and anchor cables in fast-excavation coal roadways, comprising the following steps:

[0087] Step 1: Obtain on-site rock samples, test the basic physical and mechanical parameters of the rocks, and use FLAC. 3D Numerical simulation software is used to model coal mine roadways based on actual on-site engineering conditions, apply ground stress, and provide support for different areas of the roof.

[0088] As a preferred method, the process of obtaining on-site rock samples and testing the basic physical and mechanical parameters of the rocks is as follows:

[0089] S11: Obtain parameters for each zone of the top strata in both the elastic and plastic stages, including the maximum principal stress in the plastic stage. Intermediate principal stresses during the plastic stage Minimum principal stress during the plastic stage Maximum principal stress in the elastic stage Intermediate principal stress in the elastic stage Minimum principal stress in the elastic stage All units are Pa, Poisson's ratio of the surrounding rock. (Dimensionless) Elastic modulus of surrounding rock (in Pa), and the volume of each surrounding rock unit. ;

[0090] S12: Obtain the stress at four monitoring points on the anchor plate respectively. , , , All units are Pa, representing the maximum deformation of the anchor bolt. (Unit: m) Anchor bolt anchorage length Spacing between anchor bolts The stress at four monitoring points on the anchor cable tray was obtained respectively. , , , Maximum deformation of anchor cable (Unit: m) Anchor cable anchorage length Spacing between anchor cables .

[0091] Step 2: Calculate the anchor load based on the stress monitored by the anchor tray and the tray area;

[0092] As a preferred method, the prestressed anchor load after excavation equilibrium is calculated according to the following formula. :

[0093]

[0094] In the formula, The length of the pallet (in meters). Pallet width (in meters). Its dimension is force (unit: N);

[0095] Step 3: Calculate the anchor cable load based on the stress monitored by the anchor cable tray and the tray area;

[0096] As a preferred method, the prestressed anchor cable load after excavation equilibrium is calculated according to the following formula. :

[0097]

[0098] In the formula, The dimension of force is N.

[0099] Step 4: Adaptively divide the roof area according to the gradient distribution of energy density released by plastic failure along the width direction, resulting in multiple roof partitions, replacing the fixed three-part division, so that the partitions have a clear physical basis;

[0100] As a preferred method, the process of adaptively dividing the roof region based on the gradient distribution of energy density released during plastic failure along the roadway width is as follows:

[0101] S41: Calculate the energy density released during plastic failure of each surrounding rock element:

[0102] Calculate the first according to the following formula. Energy density of a surrounding rock unit in the elastic stage :

[0103]

[0104] In the formula, Indicates the elastic phase. Number the surrounding rock unit of the roof. The dimension is energy density (unit: J / m³). ;

[0105] Calculate the first according to the following formula. Energy density of a surrounding rock unit during the plastic stage :

[0106]

[0107] In the formula, Indicates the plastic stage, The dimension is energy density (unit: J / m³). 3 );

[0108] The following formula yields the first... Energy density released during plastic failure of each surrounding rock unit :

[0109]

[0110] This yields the energy density distribution of plastic failure released by the roof along the width of the roadway;

[0111] S42: Calculate the gradient of the energy density released by plastic failure along the width direction, and use the gradient magnitude to reflect the degree of drastic change of the energy density released by plastic failure along the width direction;

[0112] S43: Using the peak or abrupt change in the energy density gradient released during plastic failure as the partition boundary, the number of top plate partitions and the location of each partition boundary are adaptively determined to obtain the top plate region. ( , (The number of partitions is adaptively divided), instead of a fixed three-part division;

[0113] Step 5: In the multi-factor support effectiveness model, calculate the support effectiveness of the anchor bolts and anchor cables in each area of ​​the roof slab based on the anchor bolt and anchor cable load, deformation, anchorage influence coefficient and redundancy coefficient.

[0114] As a preferred option, the support effectiveness of the anchor bolts and anchor cables in each region of the roof is calculated according to the following formula. :

[0115]

[0116] In the formula, Number the top slab area. This represents the number of anchor bolts in the area. The number of anchor cables in the area. The anchorage influence coefficient (dimensionless) is related to the anchorage length. and row spacing Related, The anchorage influence coefficient (dimensionless) is related to the anchorage length of the anchor cable. and row spacing Related, , These are the allowance coefficients (dimensionless) for anchor bolts and anchor cables, respectively, which are related to the burial depth and the top plate area. Its dimension is energy (unit is J);

[0117] Step 6: Multiply the difference in energy density between the elastic stage and the plastic stage by the unit volume to obtain the energy released by the plastic failure of the surrounding rock unit in each area of ​​the roadway roof.

[0118] As a preferred option, the energy released by plastic failure of the surrounding rock unit in each region of the roadway roof is calculated using the following formula. :

[0119]

[0120] In the formula, For the first Volume of a plastically fractured surrounding rock unit (in m³) 3 ), The dimension of is energy (unit is J); if This indicates that no energy was released when the surrounding rock unit of the roof underwent plastic failure. At this point, let... ;

[0121] Step 7: Sum the released energy of all plastic failure units in each area of ​​the roadway roof under both supported and unsupported conditions to provide a dual-condition comparison for the calculation of support suppression energy.

[0122] As a preferred option, the energy released by plastic failure in various regions of the roadway roof under supported conditions is calculated according to the following formula. :

[0123]

[0124] In the formula, This represents the number of units in which the surrounding rock of the roof undergoes plastic failure. For the roof under supported conditions The plastic failure of the region releases energy (J);

[0125] Meanwhile, the energy released by plastic failure in each region of the roadway roof under unsupported conditions is calculated using the following formula. :

[0126]

[0127] In the formula, Roof under unsupported excavation conditions The number of elements in the region that undergo plastic failure. For the first unsupported excavation conditions The energy released by each plastic failure unit (in J). via FLAC 3D Data obtained from unsupported excavation simulation;

[0128] Step 8: The difference between the energy released without support and with support is taken as the support suppression energy, and the ratio of support effectiveness to the energy released with support is defined as the support effect index. Based on the support effect index, the support status of each area of ​​the roof is statically graded and evaluated. At the same time, the ratio of support suppression energy to support effectiveness is taken as the support energy efficiency, which serves as an auxiliary indicator for the economic evaluation of support.

[0129] As a preferred option, the process of statically classifying and evaluating the support status of different areas of the roof is as follows:

[0130] S81: Calculate the suppression energy of the roof support in each area according to the following formula. :

[0131]

[0132] In the formula, For the top plate Regional support suppression energy (in J);

[0133] Among them, there is support for energy release. Unsupported energy release Support and suppression energy With support effectiveness The interrelationships are shown in Figure 2;

[0134] S82: Calculate the support effectiveness index for each area of ​​the roof slab according to the following formula. :

[0135]

[0136] In the formula, The unit is J. Dimensionless;

[0137] S83: Based on the support effectiveness index The support condition is graded and evaluated:

[0138] when If the area is considered a danger zone, suggestions should be made to increase the number of anchor bolts or install additional anchor cables; when When the area is in a basically stable zone, suggestions are provided to increase the preload of anchor bolts or cables, increase the length of anchor bolts or cables, or adjust the anchorage length; when The current period is in a stable zone, and no additional support is required. It is recommended to maintain the original support scheme.

[0139] S84: Calculate the support energy efficiency of each zone of the roof using the following formula. :

[0140]

[0141] It reflects the energy release suppressed by the unit support effectiveness and is used to evaluate the marginal efficiency of support schemes and the economic comparison of support parameters. It is not directly used for hazard / stability classification.

[0142] Step 9: Considering the decay of anchor bolt and anchor cable preload over time and the evolution of surrounding rock energy release over time, establish a time-varying support effect index, and dynamically evaluate the stability of the roof based on the current classification, evolution trend, trend prediction and classification migration.

[0143] As a preferred approach, the process for dynamically evaluating roof stability is as follows:

[0144] S91: Establishing a time-varying support effectiveness index ,in To account for the time-varying support effectiveness after preload loss, ,in , To account for the time-varying loads on anchor bolts and cables after the preload decays, , These are the time-varying deformations of the anchor bolt and anchor cable, respectively. For time-varying energy release obtained through FLAC3D rheological or creep analysis; Dimensionless;

[0145] S92: Based on the time-varying support effectiveness index Conduct dynamic evaluation:

[0146] At the current moment The current support status level is determined by comparing it with the grading threshold; calculation rate of decrease over time and descent acceleration Analyze the attenuation trend of support effectiveness; based on the current and its rate of decline predict Time required to drop to the next grade threshold ,when Less than the preset warning time Timely issuance of reinforcement warnings; tracking The process of crossing the grading threshold triggers corresponding reinforcement measures when the grading level drops from a high level to a low level.

[0147] Step 10: Use the proportion of energy released in each region to reflect the degree of plastic damage in each region, and determine the reinforcement priority accordingly;

[0148] As a preferred option, the process for determining reinforcement priorities is as follows:

[0149] S101: Calculate the energy contribution rate of plastic failure in each region of the top plate according to the following formula. :

[0150]

[0151] In the formula, For the top plate Energy released during regional plastic failure (in J). The sum of energy released in each region (in J). This is a dimensionless percentage.

[0152] S102: Based on the contribution rate of plastic failure energy in each region of the top plate The size determines the priority of the reinforcement support area and its contribution rate. The larger the area, the higher the priority for reinforcement and support in that area.

[0153] The present invention will be further described below with reference to specific embodiments:

[0154] To further illustrate the calculation method for the zonal stability of the roof supported by anchor bolts (cables) in fast-excavation coal roadways, a working face in a coal mine is taken as an example. This working face has an average burial depth of 144m, an average coal seam thickness of 3.7m (stable thickness), an average dip angle of 2°, well-developed endogenous fractures, and a Protodyakonov hardness of [missing information]. .

[0155] Step 1: Parameter Acquisition, Modeling, and Support; Sampling of rock strata within a vertical range of 40m vertically upwards and 20m vertically downwards from the coal seam in the working face, testing basic physical and mechanical parameters (see Table 1), and using FLAC... 3DNumerical simulation software was used to model the actual on-site engineering conditions. Table 1 shows the rock strata mechanical parameters (density, bulk modulus, shear modulus, tensile strength, cohesion, and internal friction angle), involving four layers: medium sandstone, coal, mudstone, and sandy mudstone. Under in-situ stress conditions, the model was assigned elastic model parameters and balanced. During the elastic stage, excavation was conducted and the coordinates, maximum / intermediate / minimum principal stresses, and volumes of the surrounding rock elements in each area of ​​the roof were derived. Then, the balanced model was assigned Mohr-Coulomb model parameters and balanced again. During the plastic stage, excavation was conducted and the coordinates, principal stresses, elastoplastic state, and volumes of each element were derived. Simultaneously, the stress and maximum deformation of the anchor bolts at four monitoring points on the anchor bolt tray, the stress and maximum deformation of the anchor cables at four monitoring points on the anchor cable tray, and the anchor bolt (cable) anchorage length and spacing were obtained. The model was positioned at a distance from the working face. Partial support for the roof slab at m (immediate support zone), full support for the roof slab beyond 5m (permanent anchorage zone); roof anchor bolts in the immediate support zone. mm, row spacing mm, anchor bolt preload 50kN, timely support zone anchor bolt structure as follows Figure 3 As shown; the permanent anchorage zone is reinforced on the basis of timely support, and the spacing between anchor bolts is... mm, anchor cable mm, row spacing mm, preload 200kN, permanent anchorage zone anchor bolt and anchor cable structure as follows Figure 4 As shown.

[0156] Table 1 Rock strata mechanical parameters

[0157]

[0158] Step 2: Calculate the anchor bolt load; the arrangement of anchor bolt tray measuring points and the change of measuring point stress with the number of running steps are as follows: Figure 5 As shown;

[0159]

[0160]

[0161] .

[0162] Step 3: Calculate the anchor cable load; the arrangement of anchor cable tray measuring points and the change of measuring point stress with the number of running steps are as follows: Figure 6 As shown;

[0163]

[0164]

[0165] .

[0166] Step 4: Adaptive zoning; calculate the energy density released by plastic failure of each surrounding rock unit according to the formula described in S41 of Step 4. The energy density distribution of the roof along the width of the roadway was obtained; its gradient along the width direction was calculated, and the gradient peak value was used as the partition boundary to adaptively determine the partition. Under this working condition, the adaptive partitioning resulted in three regions: left region I (about 2m from the left side), middle region II (about 1m to the left and right of the center line), and right region III (about 2m from the right side), which are basically consistent with the uniform partition boundary of the 6.0m roadway width.

[0167] Step 5: Calculate support effectiveness; according to The calculation shows that the anchoring influence coefficient in this embodiment is taken as... , m, Timely support zone: Zone I , , J; II District , , J; III District , , J. Permanent anchorage zone: Zone I , , J; II District , , J; III District , , J.

[0168] Step 6: Calculate the energy released by the unit; for the plastic failure unit, according to... Calculate, if Then set it to 0.

[0169] Step 7: Calculate the energy released in each zone; the energy released during plastic failure in the three zones under supported conditions are as follows: J、 J、 J (Model length 5m). Passed via FLAC 3D The energy released in the three zones, obtained from unsupported excavation simulation, is as follows: J、 J、 J (In this embodiment, the energy released without support is approximately twice that with support). Based on the length of the cyclic support unit: the energy released per unit support length in the timely support zone (1.1m) I, II, and III are 598.29J, 817.66J, and 578.35J, respectively; in the permanent anchorage zone (3.3m), they are 1794.87J, 2452.99J, and 1735.04J, respectively; the corresponding energy released per unit support length without support are 1196.58J, 1635.33J, and 1156.69J in the timely support zone, and 3589.74J, 4905.98J, and 3470.08J in the permanent anchorage zone.

[0170] Step 8: Calculate and classify support suppression energy, support effectiveness index, and support energy efficiency; support suppression energy The effective support index was 598.29 J, 817.67 J, and 578.34 J for zones I, II, and III, respectively, and 1794.87 J, 2452.99 J, and 1735.04 J for zones III, respectively, for zones IV, V, and III. Timely support zones I, II, and III are respectively All are in the basically stable zone ( The energy released by the failure of the plastic zone of the surrounding rock in each section of the roof of the timely support area is related to the roof support effectiveness, for example... Figure 7 As shown; the permanent anchorage zones are 2.44, 3.55, and 2.53, respectively, all within the stable zone. The energy released during failure of the plastic zone of the surrounding rock in each section of the permanent anchorage zone and the effectiveness of the roof support are compared to, for example... Figure 8 As shown. Support energy efficiency: Timely support zones I, II, and III are respectively , , The permanent anchorage zones are respectively , , This reflects the marginal decrease in support energy efficiency as the support strength increases. As an auxiliary indicator for evaluating the economic efficiency of support, it compares the support effectiveness index of each zone of the roof slab in the timely support area with that of the permanently anchored zone. Figure 9 As shown.

[0171] It should be noted that in this embodiment... Therefore Support energy efficiency This is the support effectiveness index. The reciprocal of the support effectiveness index It reflects the relative strength of the support effectiveness and the energy released. The larger the area, the more stable it is; in this embodiment, the timely support area... for All are in the basically stable zone ( Permanent anchorage zone for All are in the stable region ( Support energy efficiency Reflecting the energy release suppressed by the unit support effectiveness, in this embodiment, the timely support zone Relatively large ( Permanent anchorage area Relatively small This reflects the marginal decrease in support energy efficiency as the support is strengthened, serving as an auxiliary indicator for evaluating the economic efficiency of support; combined with the absolute amount of support suppression energy (permanent anchorage zone) (Larger) and time-varying evaluation, the overall stability of the permanent anchorage area is better.

[0172] The summary results of the energy released by support, energy released without support, energy suppressed by support, support effectiveness, and support effect index in each area of ​​the timely support zone and the permanent anchorage zone of the roof are shown in Table 2.

[0173] Table 2 Calculation parameters for roof support effectiveness and support effect index

[0174]

[0175] Note: Support effectiveness index The larger the value, the more stable it is; support energy efficiency As an auxiliary economic indicator; in this embodiment Therefore .

[0176] Step 9: Time-varying dynamic evaluation; establishing a time-varying support effectiveness index Considering the decay of anchor (cable) preload over time and the evolution of surrounding rock energy release over time; via FLAC 3D Rheological analysis is used to obtain time-varying released energy. In this embodiment, the timely support zone and the permanent anchorage zone are considered. All decrease slowly over time. By calculating the rate of decrease and predicting the time to reach the classification threshold, it is possible to... A reinforcement warning should be issued before the threshold is exceeded; when When a level is downgraded from a high level to a low level, a corresponding level enhancement is triggered.

[0177] Step 10: Calculate the energy contribution rate and determine the reinforcement priority; :I zone Zone II Zone III The energy contribution rates of plastic failure in zones I, II, and III of the top plate are respectively... The contribution rates of Zone II (41%) and Zone III (29%) are higher than those of Zones I and III (closer to the two sides), and the contribution rates of Zones I and III are basically the same. This indicates that under this working condition, there is more plastic failure in the surrounding rock in the middle of the roof. When reinforcing the support, priority should be given to the middle area of ​​the roof. The contribution rates of energy released by plastic failure of the surrounding rock in each zone of the roof are as follows: Figure 10 As shown.

[0178] This embodiment verifies that the proposed method can achieve quantitative and qualitative evaluation of the stability of the roof zoning in fast coal roadways through adaptive zoning, multi-factor support effectiveness, support suppression energy and support effect index, time-varying evaluation and energy contribution rate, providing a basis for support design and construction.

[0179] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Those skilled in the art can make various modifications, substitutions, and variations to these embodiments without departing from the principles and spirit of the invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for calculating the zonal stability of roof support using anchor bolts and anchor cables in fast-excavation coal roadways, characterized in that, Includes the following steps: Step 1: Obtain on-site rock samples, test the basic physical and mechanical parameters of the rocks, and create an actual model of the coal mine roadway based on the on-site engineering conditions. Apply ground stress and provide support for different areas of the roof. Step 2: Calculate the anchor load based on the stress monitored by the anchor tray and the tray area; Step 3: Calculate the anchor cable load based on the stress monitored by the anchor cable tray and the tray area; Step 4: Adaptively divide the roof area according to the gradient distribution of energy density released by plastic failure along the width direction to obtain multiple roof partitions; Step 5: Calculate the support effectiveness of the anchor bolts and anchor cables in each area of ​​the roof slab based on the anchor bolt and cable load, deformation, anchorage influence coefficient and redundancy coefficient; Step 6: Multiply the difference in energy density between the elastic stage and the plastic stage by the unit volume to obtain the energy released by the plastic failure of the surrounding rock unit in each area of ​​the roadway roof. Step 7: Sum the released energy of all plastic failure units in each area of ​​the roadway roof under both supported and unsupported conditions. Step 8: The difference between the energy released by unsupported and supported structures is taken as the support suppression energy. The ratio of support effectiveness to the energy released by supported structures is defined as the support effect index. Based on the support effect index, the support status of each area of ​​the roof is statically graded and evaluated. Step 9: Establish a time-varying support effectiveness index and dynamically evaluate the roof stability based on the current classification, evolution trend, trend prediction and classification migration; Step 10: Use the proportion of energy released in each region to reflect the degree of plastic damage in each region, and determine the reinforcement priority accordingly.

2. The method for calculating the zonal stability of roof support using anchor bolts and cables in a fast-excavation coal roadway according to claim 1, characterized in that, In step 1, the process of obtaining on-site rock samples and testing the basic physical and mechanical parameters of the rocks is as follows: S11: Obtain the unit parameters of the top strata in both the elastic and plastic stages, including the maximum principal stress in the plastic stage. Intermediate principal stresses during the plastic stage Minimum principal stress during the plastic stage Maximum principal stress in the elastic stage Intermediate principal stress in the elastic stage Minimum principal stress in the elastic stage Poisson's ratio of surrounding rock Elastic modulus of surrounding rock and the volume of each surrounding rock unit. ; S12: Obtain the stress at four monitoring points on the anchor plate respectively. , , , Maximum deformation of anchor bolt Anchor bolt anchorage length Spacing between anchor bolts The stress at four monitoring points on the anchor cable tray was obtained respectively. , , , Maximum deformation of anchor cable Anchor cable anchorage length Spacing between anchor cables .

3. The method for calculating the zonal stability of roof support using anchor bolts and anchor cables in a fast-excavation coal roadway according to claim 1, characterized in that, In step 2, the prestressed anchor load after excavation equilibrium is calculated according to the following formula. : In the formula, For the length of the tray, For the width of the tray; In step 3, the prestressed anchor cable load after excavation equilibrium is calculated according to the following formula. : 。 4. The method for calculating the zonal stability of roof support using anchor bolts and cables in a fast-excavation coal roadway according to claim 1, characterized in that, In step 4, the process of adaptively dividing the roof region based on the gradient distribution of the energy density released during plastic failure along the roadway width is as follows: S41: Calculate the energy density released during plastic failure of each surrounding rock element: Calculate the first according to the following formula. Energy density of a surrounding rock unit in the elastic stage : In the formula, Indicates the elastic phase. Number the surrounding rock units of the roof; Calculate the first according to the following formula. Energy density of a surrounding rock unit during the plastic stage : In the formula, Indicates the plastic stage; The following formula yields the first... Energy density released during plastic failure of each surrounding rock unit : Thus, the energy density distribution of plastic failure of the roof along the width of the roadway is obtained; S42: Calculate the gradient of the energy density released by plastic failure along the width direction, and use the gradient magnitude to reflect the degree of drastic change of the energy density released by plastic failure along the width direction; S43: Using the peak or abrupt change in the energy density gradient released during plastic failure as the partition boundary, the number of top plate partitions and the location of each partition boundary are adaptively determined to obtain the top plate region. .

5. The method for calculating the zonal stability of roof support using anchor bolts and cables in a fast-excavation coal roadway according to claim 1, characterized in that, In step 5, the support effectiveness of the anchor bolts and anchor cables in each area of ​​the roof is calculated according to the following formula. : In the formula, Number the top slab area. This represents the number of anchor bolts in the area. The number of anchor cables in the area. This is the anchorage influence coefficient of the anchor bolt. This is the anchorage influence coefficient of the anchor cable. , These are the margin coefficients for anchor bolts and anchor cables, respectively.

6. The method for calculating the zonal stability of roof support using anchor bolts and cables in a fast-excavation coal roadway according to claim 1, characterized in that, In step 6, the energy released by plastic failure of the surrounding rock unit in each area of ​​the roadway roof is calculated according to the following formula. : In the formula, For the first The volume of a plastically fractured surrounding rock unit.

7. The method for calculating the zonal stability of roof support using anchor bolts and cables in a fast-excavation coal roadway according to claim 1, characterized in that, In step 7, the energy released by plastic failure in each area of ​​the roadway roof under supported conditions is calculated according to the following formula. : In the formula, This represents the number of units in which the surrounding rock of the roof undergoes plastic failure. For the roof under supported conditions Plastic failure in the region releases energy; Meanwhile, the energy released by plastic failure in each region of the roadway roof under unsupported conditions is calculated using the following formula. : In the formula, Roof under unsupported excavation conditions The number of elements in the region that undergo plastic failure. For the first unsupported excavation conditions The energy released by each plastic failure unit, Obtained through unsupported excavation simulation.

8. The method for calculating the zonal stability of roof support using anchor bolts and cables in a fast-excavation coal roadway according to claim 1, characterized in that, In step 8, the process of statically classifying and evaluating the support status of each area of ​​the roof is as follows: S81: Calculate the suppression energy of the roof support in each area according to the following formula. : In the formula, For the top plate Regional support suppresses energy; S82: Calculate the support effectiveness index for each area of ​​the roof slab according to the following formula. : S83: Based on the support effectiveness index The support condition is graded and evaluated: when If the area is considered a danger zone, suggestions should be made to increase the number of anchor bolts or install additional anchor cables; when When the area is in a basically stable zone, suggestions are provided to increase the preload of anchor bolts or cables, increase the length of anchor bolts or cables, or adjust the anchorage length; when The current period is in a stable zone, and no additional support is required. It is recommended to maintain the original support scheme.

9. The method for calculating the zonal stability of roof support using anchor bolts and cables in a fast-excavation coal roadway according to claim 1, characterized in that, In step 9, the process of dynamically evaluating the stability of the roof is as follows: S91: Establishing a time-varying support effectiveness index ,in To account for the time-varying support effectiveness after preload loss, ,in , To account for the time-varying loads on anchor bolts and cables after the preload decays, , These are the time-varying deformations of the anchor bolt and anchor cable, respectively. For time-varying energy release obtained through rheological or creep analysis; S92: Based on the time-varying support effectiveness index Conduct dynamic evaluation: At the current moment The current support status level is determined by comparing it with the grading threshold; calculation rate of decrease over time and descent acceleration To analyze the attenuation trend of the support effect; Based on the current and its rate of decline predict Time required to drop to the next grade threshold ,when Less than the preset warning time Timely issuance of reinforcement warnings; tracking The process of crossing the grading threshold triggers corresponding reinforcement measures when the grading level drops from a high level to a low level.

10. The method for calculating the zonal stability of roof support using anchor bolts and cables in a fast-excavation coal roadway according to claim 1, characterized in that, In step 10, the process of determining the reinforcement priority is as follows: S101: Calculate the energy contribution rate of plastic failure in each region of the top plate according to the following formula. : In the formula, For the top plate Regional plastic failure releases energy. The sum of energy released in each region; S102: Based on the contribution rate of plastic failure energy in each region of the top plate The size determines the priority of the reinforcement support area.

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