Calculation method of tunnel impact resistance considering coupling effect of support-pressure relief-surrounding rock

Abstract

The anti-impact calculation method of the tunnel considering the coupling effect of support-unloading-surrounding rock is as follows: the corresponding specimen strength is determined according to the strength grade of the tunnel surrounding rock, and the roof support grade and specimen type are determined by using the support parameters of the roof; the specimen types of the two sides are determined by comprehensively considering the support parameters and unloading parameters of the two sides of the tunnel; the anchoring position is determined according to the roof specimen type, and the anchoring position and hole adding position are determined according to the two side specimen types, and the specimens that meet the requirements are produced; dynamic impact tests and specimen energy calculations are carried out on the specimens, indoor specimens are produced and tested according to the on-site engineering conditions, and then the bearing energy of the anchored surrounding rock per unit volume of the two sides and the roof is calculated according to the stress-strain curves obtained in the test, and finally the calculation results are converted to the on-site engineering for energy calculation of the tunnel anchor bearing structure.

Description

Technical Field

[0001] The invention relates to a tunnel impact resistance calculation method considering the coupling effect of support-pressure relief-surrounding rock. Background Art

[0002] In recent years, with the continuous increase in the depth and intensity of coal mining in my country, the distribution range and number of rock burst mines have become larger and larger, the frequency of rock burst and the degree of damage have become more severe, often causing equipment damage and casualties. Rock burst disasters have become the main disaster restricting the safe, high-yield and efficient mining of coal mines. According to statistics, 90% of rock burst disasters occur in tunnels, and reasonable anti-impact measures in tunnels can effectively reduce or avoid the damage caused by rock burst. At present, the most commonly used methods in my country's rock burst prevention and control technology are mainly strengthening support and large-diameter drilling to relieve pressure. Under the conditions of strengthening support and large-diameter pressure relief, the impact resistance value is a comprehensive evaluation index for the safety, stability and impact resistance of the tunnel, but there is no authoritative standard for how to calculate the impact resistance energy of rock burst tunnels.

[0003] At present, there is only "A Calculation Method for the Impact Resistance of Tunnel Roof Anchor Support" (Application Publication No. CN111259542A), which discloses a calculation method for the impact resistance of tunnel roof anchor support. The invention first calculates the energy of the tunnel roof anchor rod and anchor cable before the ultimate deformation and failure, and then calculates the energy limit value absorbed by the roof support system before failure based on the spacing. Since the energy applied by the roof to the support system when impact ground pressure occurs is the sum of kinetic energy and potential energy, in the critical state, this energy is equal to the energy limit value of the support system, thereby obtaining the minimum speed that causes the failure of the roof support system; the maximum vibration speed of the rock mass corresponding to the maximum mine earthquake energy level obtained by mine monitoring is compared with the obtained minimum speed, and the impact resistance of the current roof anchor cable support is judged according to the comparison result.

[0004] However, this calculation method has the following shortcomings:

[0005] (1) The impact resistance of the roof and the two sides is not considered comprehensively. The tunnel resists the impact ground pressure as a whole, which is not the result of the roof or the side alone; therefore, when calculating the impact resistance of the support system, it is unreasonable to only consider the roof or the two sides alone. Such an impact resistance calculation method cannot fully reflect the actual impact resistance of the tunnel.

[0006] (2) The coupling effect between the support structure and the surrounding rock is not considered. The support structure and the surrounding rock form a unified anchor bearing body, which produces displacement and deformation after being subjected to impact loads. Therefore, in the process of calculating the impact resistance of the support system, it is not in line with engineering practice to consider the support structure and the surrounding rock separately.

[0007] (3) Failure to consider the pressure relief effect. In rock burst tunnels, large-diameter drilling to relieve pressure has become a customary measure. It has an important influence on the calculation of the impact resistance of the anchor bearing structure and is a factor that must be considered. The existing impact resistance calculation methods do not consider the role of pressure relief holes. Summary of the invention

[0008] The present invention proposes a tunnel impact resistance calculation method that comprehensively considers the support-unloading-surrounding rock coupling effect, and calculates the tunnel impact resistance capacity in a more accurate and reasonable way, which is of great significance to reducing production costs, ensuring personnel safety and efficient production.

[0009] The technical solution is: a tunnel impact resistance calculation method that comprehensively considers the coupling effect of support-pressure relief-surrounding rock. The specific steps include:

[0010] Step 1) Investigate the specific tunnel-related engineering support parameters on site.

[0011] (1) Investigate the engineering geological parameters of the tunnel, including the roof and two sides: ① intact rock block strength, ② core quality index RQD / % and ③ discontinuous surface spacing;

[0012] (2) Investigate the specific support parameters of the tunnel: ① tunnel dimension parameters, including: tunnel width A, tunnel height B; ② roof support parameters, including: roof anchor length l g1 , diameter, spacing and row spacing, length of top plate anchor cable l s1 , diameter, spacing and row spacing; ③ tunnel side support parameters and pressure relief parameters: the length of the anchor rods on both sides of the tunnel l g2 , diameter, spacing and row spacing, length of anchor cables on both sides of the tunnel l s2 , diameter, spacing and row spacing, drilling depth l on both sides of the tunnel k , diameter and spacing;

[0013] (3) Investigate the tunnel cycle to determine the step length L;

[0014] Step 2) Model making and mechanical experiment

[0015] Step 2.1) Determine the strength and type of test specimen

[0016] Step 2.11) Determine the strength of the test specimen

[0017] According to the engineering geological parameters of the tunnel investigated in the first step, the three parameters of intact rock block strength, core quality index RQD / %, and discontinuous surface spacing, the top plate and the two sides are scored separately according to the rock classification system shown in Table 1. Different scoring values ​​correspond to different levels of surrounding rock strength. The tunnel surrounding rock strength in the table is divided into grades I to V. As shown in Table 2, different tunnel surrounding rock strengths correspond to different specimen strengths, which means different sand-cement ratios in the specific specimen determination.

[0018] Table 1 Rock mass classification system

[0019]

[0020] Table 2 Correspondence between rock mass score and specimen strength

[0021]

[0022] Step 2.12) Determine the type of test specimen

[0023] ① According to the roof support parameters investigated in the first step, the length of the roof anchor l g1 , diameter, spacing and row spacing, length of top plate anchor cable l s1 , diameter, spacing and row spacing, and determine the type of top plate specimen according to the corresponding conditions between the support level and the specimen shown in Table 3;

[0024] ② According to the specific support parameters and pressure relief parameters of the two sides of the tunnel investigated in the first step, the length of the anchor bolts on the two sides of the tunnel l g2 , diameter, spacing and row spacing, length of anchor cables on both sides of the tunnel l s2 , diameter, spacing and row spacing, drilling depth l on both sides of the tunnel k , diameter and spacing, and combine them according to the support and pressure relief grades in Table 3 and Table 4 to determine the specimen types for the two sides.

[0025] Table 3 Correspondence between support level and specimen

[0026]

[0027] Table 4 Correspondence between pressure relief levels and test pieces

[0028] Pressure relief level Main pressure relief parameters Specimen type I No pressure relief measures No holes II Pressure relief hole parameters: spacing 2.0~2.5m, hole depth 20~30m, hole diameter ≥150mm Single hole III Pressure relief hole parameters: spacing 1.5m~2.0m, hole depth ≥30m, hole diameter ≥150mm Double hole

[0029] Step 2.2) Specimen preparation

[0030] Step 2.21) According to the specimen type determined in step 2.1), the materials are mixed according to the similarity theorem to ensure that the sand-binder ratio is consistent with the specimen strength grade determined in step 1), and standard cylindrical specimens are made, and the size, mass and density of each standard cylindrical specimen are measured and recorded;

[0031] Step 2.22) Make the top plate specimen. According to the type of top plate specimen determined in step 2.1), determine the anchoring position, drill a hole perpendicular to the axial direction on the side of the standard cylindrical specimen, insert the stainless steel wire into it, bond it with adhesive, and pre-tighten it. The anchoring specimen is made. There must be no less than 3 top plate specimens under the same support condition;

[0032] Step 2.23) Make two-side specimens. According to the two-side specimen types determined in step 2.1), determine the anchoring position and the hole adding position. Drill holes perpendicular to the axial direction on the side of the standard cylindrical specimen, insert the stainless steel wire into it, bond it with adhesive, and pre-tighten it to complete the anchoring production; then drill holes perpendicular to the axial direction at the hole adding position on the side of the standard cylindrical specimen. The "anchor + hole" specimen is completed. The two-side specimens under the same support condition shall not be less than 3. When the two sides adopt asymmetric support, no less than 3 specimens shall be made for each of the two sides;

[0033] Step 2.3) Dynamic impact test and specimen energy calculation

[0034] Step 2.31) Impact test: Using a Hopkinson pressure bar test system, impact tests are performed on the test pieces prepared in step 2.2) to obtain stress-strain curves during the test;

[0035] Step 2.32) Calculation of specimen energy.

[0036] Integrate the stress-strain curve obtained from the test to find the area enclosed by the stress-strain curve and the coordinate axis, recorded as K, unit MJ / m 3 , that is, the energy that the anchored surrounding rock can bear per unit volume, and the integral formula is shown in formula (1):

[0037] K=∫σ1dε1 (1)

[0038] The energy calculated from the integration results of the stress-strain curves of multiple specimens of the top plate is averaged and recorded as K d ; The energy calculated from the integration results of the stress-strain curves of multiple specimens in both gangs is averaged and recorded as K b .

[0039] Step 3) Energy conversion calculation of anchored bearing structure under engineering conditions

[0040] The calculation result of the energy that the anchored surrounding rock per unit volume of the two sides and the top plate obtained in step 2) can bear is converted into the energy calculation of the tunnel anchor bearing structure in the on-site project. The calculation formula is as follows:

[0041] The top plate is calculated according to the following formula:

[0042] E D =A×H D ×L×Kd ×η (2)

[0043]

[0044] Where: E D is the energy that can be absorbed by the roof support structure; A is the tunnel width; H D is the equivalent thickness of the top plate (l s1 , l g1 are the lengths of the roof anchor cable and anchor rod, respectively; λ is the corresponding coefficient, which is taken as 1.5 here; L is the periodic pressure step distance of the tunnel; K d The energy that the anchored rock mass per unit volume of the roof can bear, in MJ / m 3 ; η is the conversion factor considering the difference between indoor test and on-site engineering;

[0045] The two gangs are calculated according to the following formula:

[0046] E B =B×H B ×L×K b ×μ (4)

[0047]

[0048] Where: E B is the energy that can be absorbed by the supporting structure of the side; B is the height of the tunnel; H B is the equivalent thickness of the top plate, (l s2 , l g2 are the lengths of the top plate anchor cable and anchor rod, respectively, l k is the drilling depth, λ is the corresponding coefficient, which is taken as 1.5 here); K b It is the energy that the anchored surrounding rock per unit volume can bear, in MJ / m 3 ; η is the conversion factor considering the difference between indoor test and on-site engineering.

[0049] The overall energy calculation formula of the anchor bearing structure is as follows:

[0050]

[0051] Where: E C is the total energy that the anchor bearing structure can absorb; E D E is the energy that can be absorbed by the roof support structure. B The calculated energy that the two supporting structures can absorb.

[0052] Beneficial effects:

[0053] (1) Higher safety. If one of the top plate and the two sides is damaged, the tunnel is damaged. Different from other existing impact resistance calculation methods, the calculation method in the present invention comprehensively considers the impact resistance of the top plate and the two sides, and couples the impact resistance of the top plate and the two sides. The final calculation result is less than any one of the top plate and the two sides. Using this result as the actual impact resistance of the tunnel can make the overall safety factor of the tunnel higher.

[0054] (2) More in line with the actual situation on site. Once installed, support structures such as anchor rods and anchor cables are no longer independent structures, but form a unified whole with the surrounding rock. Different from other existing impact resistance calculation methods, the calculation method in the present invention fully considers the coupling effect between the support structure and the surrounding rock, and calculates the anchor bearing structure formed by the support structure and the surrounding rock as a whole.

[0055] (3) More scientific and reasonable. Large-diameter drilling pressure relief measures are commonly used preventive measures for rock burst tunnels. Drilling pressure relief achieves pressure relief by destroying the anchoring surrounding rock and transferring high stress to the deep part; in terms of implementation technology, if the spacing between the pressure relief holes is small, it will produce a better anti-impact effect, but it will damage the anchoring bearing structure on a large scale, reduce the stability of the tunnel surrounding rock, and sometimes affect the tunnel excavation speed. Therefore, the effect of the pressure relief holes on the anchoring surrounding rock is a factor that must be considered in the calculation of impact resistance. Different from other existing impact resistance calculation methods, the calculation method in the present invention fully considers the pressure relief effect, and combines the "unloading-solidification" coordinated quantitative control of the tunnel surrounding rock (energy release by the pressure relief holes and energy absorption by the support structure) to make the calculation results more scientific and reasonable.

[0056] (4) Originated from the site and returned to the site. From the first step of field investigation, to the second step of model making and indoor testing, to the third step of energy calculation under engineering conditions, each step of the present invention is closely combined with the site conditions. Each process fully considers the interaction between support, pressure relief and surrounding rock. The calculation method of the present invention adopts dynamic load impact test, which fully considers the dynamic response effect of the on-site anchoring bearing structure, including energy generation, attenuation, energy absorption of the anchoring structure, and energy release process of the pressure relief hole, so that the calculation result is more in line with the actual energy absorption value of the on-site anchored coal rock mass. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 Schematic diagram of the specimen model dimensions and the locations of added holes and anchors. DETAILED DESCRIPTION

[0058] Example 1

[0059] The following is a specific example of a rock burst mine to further illustrate this patent:

[0060] Step 1: Investigate the relevant engineering support parameters of the specific tunnel on site

[0061] (1) Engineering geological parameters of the tunnel. The survey showed that the strength of the intact rock blocks on the roof and two sides of the tunnel were 132MPa and 35MPa respectively; the core quality index RQD was 64% and 34% respectively; the spacing between discontinuous surfaces was 232mm and 189mm respectively;

[0062] (2) Specific tunnel support parameters. ① Tunnel dimension parameters: tunnel width A is 4.8m, tunnel height B is 5.2m; ② Tunnel support parameters: length of roof anchor l g1 The length of the anchor cable is 2.4m, the diameter of the anchor rod is 22mm, the row spacing is 850mm, the spacing is 800mm, and the length of the top plate anchor cable is l s1 The length of the anchor rods is 6.2m, the diameter of the anchor cable is 22mm, the row spacing is 1200mm, and the spacing is 1600mm; the length of the anchor rods on both sides is l g2 The anchor length is 3.0m, the diameter of the anchor rod is 22mm, the spacing is 850mm, the row spacing is 800mm, and the length of the two anchor cables is l s2 The anchor cable is 6.2m in diameter, the spacing is 1200mm, the row spacing is 1600mm, and the drilling depth of the two sides is l k The drilling distance is 20m, the drilling diameter is 150mm, and the drilling spacing is 2m;

[0063] (3) The periodic pressure step distance L of the tunnel is 40m.

[0064] Step 2: Model making and mechanical testing

[0065] I: Determine the strength and type of test specimen

[0066] (1) Determine the strength of the test specimen

[0067] Based on the engineering geological parameters of the tunnel investigated in the first step, the roof and the two sides were scored separately according to the rock classification system shown in Table 1;

[0068] The three parameters of the roof's intact rock strength, core quality index RQD / %, and discontinuous surface spacing were scored as 40, 20, and 10, respectively, with a total score of 70. According to the scoring criteria in Table 2, the surrounding rock strength grade belongs to Grade II, the specimen strength is determined to be a high-strength specimen, and the sand-binder ratio is configured at 5:1;

[0069] The scores of the three parameters of intact rock block strength, core quality index RQD / %, and discontinuous surface spacing of the two sides are 20, 15, and 8 respectively, with a total score of 43. According to the scoring criteria in Table 2, the surrounding rock strength grade belongs to grade III, the specimen strength is determined to be a medium strength specimen, and the sand-binder ratio is configured at 6:1;

[0070] (2) Determine the test specimen type

[0071] According to the specific support parameters of the tunnel investigated in the first step, and according to the support grade classification in Table 3, the support grade of the roof is determined to be Class C, and the test specimen type of the roof is "three anchors";

[0072] According to the support parameters of the two gangs, the support grade is determined to be C, and the corresponding specimen type is "three anchors". The pressure relief grade is II, and the corresponding specimen type is "single hole". Therefore, the final specimen type of the two gangs is "single hole + three anchors".

[0073] II: Test piece preparation

[0074] According to the strength and type of the specimens determined in step I, test specimens are made for the top plate and the two sides. The model is made using a standard cylindrical mold with a geometric size of 50mm×100mm and a height-to-diameter ratio of 2.0. The specimen production steps are as follows:

[0075] (1) Mixing materials: Mix materials according to the similarity theorem to ensure that the sand-cement ratio of the top plate and the two sides is 5:1 and 6:1, that is, the total ratio of quartz sand to water, calcium carbonate, gypsum and cement, which is consistent with the strength grade of the specimen determined in the first step;

[0076] (2) In the process of making a standard cylindrical mold, similar raw materials are mixed evenly, placed in a mold coated with dimethyl silicone oil on the inside for filling, tamping, demolding, and drying. After curing for 15 days, the surface of the sample is polished and smoothed. The standard cylindrical specimen is made, and the size, mass, and density of each sample are measured and recorded;

[0077] (3) Make the roof specimen. According to the roof specimen type determined in step I, use a 5 mm diameter drill and drill according to the specimen model diagram. Figure 1 At the "anchoring" position shown by "three anchors", three holes are drilled perpendicular to the axial direction on the side of the standard cylindrical specimen, and the specimen is divided into four equal parts along the axial direction. Then, a stainless steel wire with a diameter of 3 mm is inserted into it, and then a mixture of barite powder and rosin alcohol solution is selected as a binder. A torque wrench is used for pre-tightening, and the "anchoring specimen" is completed. In this example, three specimens are made;

[0078] (4) Make two side specimens. According to the type of two side specimens determined in step I, use a 5 mm diameter drill to drill the specimens according to the following method: Figure 1 In the "anchoring" position of the "single hole + three anchors" shown in the figure, a hole is drilled perpendicular to the axial direction on the side of the standard cylindrical specimen, and a stainless steel wire with a diameter of 3 mm is inserted into it. Then, a mixture of barite powder and rosin alcohol solution is used as a binder, and a torque wrench is used for pre-tightening; then, according to Figure 1The "additional hole" position of the "single hole + three anchors" shown is drilled with a 3mm diameter drill. The anchors and holes divide the specimen into four equal parts along the axial direction. The "additional anchor + additional hole" specimen is completed. In this example, three specimens are made.

[0079] III: Dynamic impact test and specimen energy calculation

[0080] (1) Impact test: After the specimen is made, a dynamic impact test and specimen energy calculation are carried out. The Hopkinson pressure bar test system is used to test the specimens made in the previous step. The specific steps are as follows:

[0081] ① Test device: The incident rod, transmission rod and absorption rod are made of Φ50mm steel rod with elastic modulus of 210GPa, the yield strength of the incident rod and transmission rod is greater than 800MPa, the compression rod material is 48CrMoA, the length of the incident rod and transmission rod is 3000mm, and the length of the absorption rod is 1500mm;

[0082] ② Test conditions: The longitudinal wave velocity is 5190m / s, the impact loading is a cylindrical bullet (Φ50mm, length 500mm, 700mm), and a rectangular wave loading is performed for a certain length of time;

[0083] ③Test result processing: Use PC to export the stress-strain curve during the test.

[0084] (2) Specimen energy calculation

[0085] The obtained stress-strain curve is integrated according to the integral formula (1) to obtain the area enclosed by the stress-strain curve and the coordinate axis.

[0086] The energy calculated from the stress-strain curves of the three specimens of the top plate is: 0.85MJ / m 3 、0.93MJ / m 3 、0.62MJ / m 3 , take the average value and record it as K d =0.8MJ / m 3 The energy calculated from the stress-strain curves of the three specimens in the two gangs is: 0.64MJ / m 3 、0.54MJ / m 3 , 0.32MJ / m 3 , take the average value and record it as k b =0.5MJ / m 3 .

[0087] Step 3: Energy calculation of anchor bearing structure.

[0088] According to formulas (2) to (3), the energy that the top plate can absorb is:

[0089]

[0090] E D =A×H D ×L×K d ×η=4.8×2.6×40×0.8×2%=7.9872×10 6 J

[0091] According to formulas (4) to (5), the energy that the two gangs can absorb is:

[0092]

[0093] E B =B×H B ×L×K b ×μ=5.2×2.45×40×0.5×5%=12.74×10 6 J

[0094] According to formula (6), the overall energy of the anchor bearing structure is calculated:

[0095]

[0096] Therefore, the energy that the anchor bearing structure of the tunnel can absorb when the periodic pressure step is a whole is 4.91×10 6 J.

Claims

1. The tunnel impact resistance calculation method considering the coupling effect of support-pressure relief-surrounding rock is characterized by: The following steps are involved: Step 1) Investigate the relevant engineering support parameters of the specific tunnel on site (1) Investigate the engineering geological parameters of the tunnel, including the roof and two sides: ① intact rock block strength, ② core quality index RQD / % and ③ discontinuous surface spacing; (2) Investigate the specific support parameters of the tunnel: ① tunnel dimension parameters, including: tunnel width A, tunnel height B; ② roof support parameters, including: roof anchor length l g1 , diameter, spacing and row spacing, length of top plate anchor cable l s1 , diameter, spacing and row spacing; ③ tunnel side support parameters and pressure relief parameters: the length of the anchor rods on both sides of the tunnel l g2 , diameter, spacing and row spacing, length of anchor cables on both sides of the tunnel l s2 , diameter, spacing and row spacing, drilling depth l on both sides of the tunnel k , diameter and spacing; (3) Investigate the tunnel cycle to determine the step length L; Step 2) Model making and mechanical experiment Step 2.1) Determine the strength and type of test specimen Step 2.11) Determine the strength of the test specimen According to the tunnel engineering geological parameters investigated in the first step, the three parameters of intact rock block strength, core quality index RQD / %, and discontinuous surface spacing, the sum of the three parameters is used to score the roof and the two sides respectively according to the rock classification system. Different scoring values ​​correspond to different levels of surrounding rock strength, and the tunnel surrounding rock strength is divided into multiple levels; according to the tunnel surrounding rock strength level, the corresponding test piece sand-binder ratio and strength are determined; Step 2.12) Determine the type of test specimen ① Based on the roof support parameters investigated in step 1), the length of the roof anchor l g1 , diameter, spacing and row spacing, length of top plate anchor cable l s1 , diameter, spacing and row spacing, determine the support level, and determine the type of top plate specimen according to the correspondence between the support level and the specimen; ② According to the tunnel side support parameters and pressure relief parameters investigated in step 1), the length of the anchor bolts on both sides of the tunnel is l g2 , diameter, spacing and row spacing, length of anchor cables on both sides of the tunnel l s2 , diameter, spacing and row spacing, drilling depth l on both sides of the tunnel k , diameter and spacing, respectively determine the support level and pressure relief level, combine the support level and pressure relief level, and determine the type of specimens on both sides of the tunnel according to the correspondence between the support level, pressure relief level and the specimens; Step 2.2) Specimen preparation Step 2.21) According to the specimen type determined in step 2.1), the materials are mixed according to the similarity theorem to ensure that the sand-binder ratio is consistent with the specimen strength grade determined in step 1), and standard cylindrical specimens are made, and the size, mass and density of each standard cylindrical specimen are measured and recorded; Step 2.22) Make the top plate specimen. According to the type of top plate specimen determined in step 2.1), determine the anchoring position, drill a hole perpendicular to the axial direction on the side of the standard cylindrical specimen, insert the stainless steel wire into it, bond it with adhesive, and pre-tighten it. The anchoring specimen is made. There must be no less than 3 top plate specimens under the same support condition; Step 2.23) Make two-side specimens. According to the two-side specimen types determined in step 2.1), determine the anchoring position and the hole adding position. Drill holes perpendicular to the axial direction on the side of the standard cylindrical specimen, insert the stainless steel wire into it, bond it with adhesive, and pre-tighten it to complete the anchoring production; then drill holes perpendicular to the axial direction on the side of the standard cylindrical specimen to complete the "anchor + hole" specimen production. The two-side specimens under the same support condition shall not be less than 3. When the two sides adopt asymmetric support, at least 3 specimens shall be made for each of the two sides; Step 2.3) Dynamic impact test and specimen energy calculation Step 2.31) Impact test: Using the Hopkinson pressure bar test system, impact tests are performed on the test pieces prepared in step 2.2) to obtain stress-strain curves during the test; Step 2.32) Calculation of specimen energy Integrate the stress-strain curve obtained from the test to find the area enclosed by the stress-strain curve and the coordinate axis, recorded as K, unit MJ / m 3 , that is, the energy that can be absorbed by the anchored surrounding rock per unit volume. The integral formula is shown in formula (1): K=∫σ1dε1 (1) The energy calculated from the integration results of the stress-strain curves of multiple specimens of the top plate is averaged and recorded as K d ; The energy calculated from the integration results of the stress-strain curves of multiple specimens in both gangs is averaged and recorded as K b ; Step 3) Energy conversion calculation of anchored bearing structure under engineering conditions The calculation result of the energy that the anchored surrounding rock per unit volume of the two sides and the top plate obtained in step 2) can bear is converted into the energy calculation of the tunnel anchor bearing structure in the on-site project. The calculation formula is as follows: The top plate is calculated according to the following formula: AND D =A×H D ×W×K d ×η (2) Where: E D is the energy that can be absorbed by the roof support structure; A is the tunnel width; H D is the equivalent thickness of the top plate (l s1 , l g1 are the lengths of the roof anchor cable and anchor rod, respectively; λ is the corresponding coefficient, which is taken as 1.5 here; L is the periodic pressure step distance of the tunnel; K d The energy that the anchored rock mass per unit volume of the roof can bear, in MJ / m 3 ; η is the conversion factor considering the difference between indoor test and on-site engineering; The two gangs are calculated according to the following formula: AND B =B×H B ×W×K b ×μ (4) Where: E B is the energy that can be absorbed by the supporting structure of the side; B is the height of the tunnel; H B is the equivalent thickness of the top plate, (l s2 , l g2 are the lengths of the top plate anchor cable and anchor rod, respectively, l k is the drilling depth, λ is the corresponding coefficient, which is taken as 1.5 here); K b It is the energy that the anchored surrounding rock per unit volume can bear, in MJ / m 3 ; η is the conversion factor considering the difference between indoor experiments and on-site engineering; The overall energy calculation formula of the anchor bearing structure is as follows: Where: E C is the total energy that the anchor bearing structure can absorb; E D E is the energy that can be absorbed by the roof support structure. B The calculated energy that the two supporting structures can absorb.

2. The method for calculating tunnel impact resistance considering the coupling effect of support-pressure relief-surrounding rock according to claim 1 is characterized in that: In step 2.11), the method for judging the tunnel surrounding rock strength, specimen strength and sand-cement ratio is as follows: 1) First, the strength of the intact rock, the core quality index RQD / % and the spacing between discontinuous surfaces are scored: 1) The strength of the intact rock block is expressed as its uniaxial compressive strength / MPa. When the uniaxial compressive strength / MPa>250, the score is 50; when the uniaxial compressive strength / MPa is 100-250, the score is 40; when the uniaxial compressive strength / MPa is 50-100, the score is 30; when the uniaxial compressive strength / MPa is 25-50, the score is 20; when the uniaxial compressive strength / MPa is 5-25, the score is 10; when the uniaxial compressive strength / MPa is 1-5, the score is 5; when the uniaxial compressive strength / MPa<1, the score is 0; 2) Core quality index RQD / %, when the percentage is 90-100, the score is 30; when the percentage is 75-90, the score is 25; when the percentage is 50-75, the score is 20; when the percentage is 25-50, the score is 15; when the percentage is less than 25, the score is 10; 3) Discontinuous surface spacing: when the spacing is greater than 2m, the score is 20; when the spacing is 0.6 to 2m, the score is 15; when the spacing is 200 to 600mm, the score is 10; when the spacing is 60 to 200mm, the score is 8; Spacing < 60 mm, the score is 5; 2) Add the corresponding scores of intact rock strength, core quality index RQD / % and discontinuous surface spacing, score the tunnel roof and two sides respectively, and determine the strength of the tunnel surrounding rock, as well as the specimen strength and sand-binder ratio: 1) The sum of the intact rock strength + core quality index RQD / % + the fraction of the spacing between discontinuous surfaces is 100-81, the surrounding rock strength grade is Grade I, the specimen strength is extremely high, and the sand-binder ratio is 4:1; 2) When the sum of the intact rock strength + core quality index RQD / % + the fraction of the spacing between discontinuous surfaces is 80-61, the surrounding rock strength grade is grade II, the specimen strength is high strength, and the sand-binder ratio is 5:1; 3) When the sum of the intact rock strength + core quality index RQD / % + the fraction of the spacing between discontinuous surfaces is 60-41, the surrounding rock strength grade is grade III, the specimen strength is medium strength, and the sand-binder ratio is 6:1; 4) When the sum of the intact rock strength + core quality index RQD / % + the fraction of the spacing between discontinuous surfaces is 40-21, the surrounding rock strength grade is grade IV, the specimen strength is general strength, and the sand-binder ratio is 7:1; 5) When the sum of the strength of the intact rock block + the core quality index RQD / % + the fraction of the spacing between discontinuous surfaces is <20, the surrounding rock strength grade is grade V, the specimen strength is low strength, and the sand-cement ratio is 8:

1.

3. The tunnel impact resistance calculation method considering the coupling effect of support-pressure relief-surrounding rock according to claim 1 is characterized in that: Step 2.12) The method for determining the specimen type of the top plate is to determine the support level and the corresponding specimen type based on the top plate support parameters: when the length of the anchor rod is less than 1.8m, the diameter is less than 18mm, the spacing is greater than 1.2m, and the row spacing is greater than 1.2m, there is no anchor cable, the support level is A, and the corresponding specimen type is single anchor; When the length of the anchor rod is 1.8-2.0m, the diameter is 18-22mm, the spacing is 0.8-1.2m, and the row spacing is 0.8-1.2m; the length of the anchor cable is less than 6.2m, the diameter is 18-22mm, the spacing is greater than 1.6m, and the row spacing is greater than 1.6m, the support level is B, and the corresponding specimen type is double anchor; When the length of the anchor rod is 2.2-2.4m, the diameter is ≥22mm, the spacing is <1.0m, and the row spacing is <1.0m; the length of the anchor cable is ≥6.2m, the diameter is ≥22mm, the spacing is ≤1.6m, and the row spacing is ≤1.6m, the support level is C, and the corresponding specimen type is three-anchor.

4. The method for calculating tunnel impact resistance considering the coupling effect of support-pressure relief-surrounding rock according to claim 1 is characterized in that: Step 2.12) The method for determining the specimen type of the two sides of the tunnel is to determine the support level and the pressure relief level respectively according to the support parameters and pressure relief parameters of the two sides of the tunnel, and combine the support level and the pressure relief level to determine the specimen type: 1) Determine the support level and the corresponding specimen type. When the length of the anchor rod is less than 1.8m, the diameter is less than 18mm, the spacing is greater than 1.2m, the row spacing is greater than 1.2m, and there is no anchor cable, the support level is A, and the corresponding specimen type is single anchor; When the length of the anchor rod is 1.8-2.0m, the diameter is 18-22mm, the spacing is 0.8-1.2m, and the row spacing is 0.8-1.2m; the length of the anchor cable is less than 6.2m, the diameter is 18-22mm, the spacing is greater than 1.6m, and the row spacing is greater than 1.6m, the support level is B, and the corresponding specimen type is double anchor; When the length of the anchor rod is 2.2-2.4m, the diameter is ≥22mm, the spacing is <1.0m, and the row spacing is <1.0m; the length of the anchor cable is ≥6.2m, the diameter is ≥22mm, the spacing is ≤1.6m, and the row spacing is ≤1.6m, the support level is C, and the corresponding specimen type is three anchors; 2) Determine the pressure relief level and the corresponding test piece type. When there is no pressure relief measure, the pressure relief level is I and the test piece type is no hole; when the spacing is 2.0-2.5m, the hole depth is 20-30m, and the hole diameter is ≥150mm, the pressure relief level is II and the test piece type is single hole; when the spacing is 1.5m-2.0m, the hole depth is ≥30m, and the hole diameter is ≥150mm, the pressure relief level is III and the test piece type is double hole; 3) Combine the support level with the pressure relief level to determine the specimen type of anchor + hole: single anchor + single hole, single anchor + double holes, double anchors + single hole, double anchors + double holes, three anchors + single hole or three anchors + double holes.

5. The method for calculating tunnel impact resistance considering the coupling effect of support-pressure relief-surrounding rock according to claim 1 is characterized in that: The method for making the standard cylindrical specimen in step 2.2) is as follows: mix similar raw materials evenly, put them into a mold with dimethyl silicone oil applied on the inside for filling, tamping, demolding, and drying. After curing for 15 days, the surface of the sample is smoothed, and the standard cylindrical specimen is completed.

6. The tunnel impact resistance calculation method considering the coupling effect of support-pressure relief-surrounding rock according to claim 1 is characterized in that: In step 2.2), the standard cylindrical specimen uses a standard cylindrical mold with a geometric size of 50 mm × 100 mm and a height-to-diameter ratio of 2.

0.

7. The method for calculating tunnel impact resistance considering the coupling effect of support-pressure relief-surrounding rock according to claim 1 is characterized in that: The sand-to-cement ratio described in step 2.21) is the ratio of the total weight of quartz sand to water, calcium carbonate, gypsum and cement.

8. The method for calculating tunnel impact resistance considering the coupling effect of support-pressure relief-surrounding rock according to claim 1 is characterized in that: In step 2.2), a hole is drilled at the anchoring position using a drill with a diameter of 5 mm, and the diameter of the stainless steel wire is 3 mm.

9. The method for calculating tunnel impact resistance considering the coupling effect of support-pressure relief-surrounding rock according to claim 1, characterized in that: Step 2.2) Use a 3mm diameter drill to drill holes at the added hole locations.

10. The tunnel impact resistance calculation method considering the coupling effect of support-pressure relief-surrounding rock according to claim 1 is characterized in that: Step 2.2) The binder is a mixture of barite powder and rosin alcohol solution.

11. The tunnel impact resistance calculation method considering the coupling effect of support-pressure relief-surrounding rock according to claim 1 is characterized in that: In step 2.31), the specific steps of the Hopkinson pressure bar test are: ① Test device: The incident rod, transmission rod and absorption rod are made of Φ50mm steel rod with elastic modulus of 210GPa, the yield strength of the incident rod and transmission rod is greater than 800MPa, the compression rod material is 48CrMoA, the length of the incident rod and transmission rod is 3000mm, and the length of the absorption rod is 1500mm; ②Test conditions: The longitudinal wave velocity is 5190m / s, and the impact loading is carried out using cylindrical bullets of Φ50mm, lengths of 500mm and 700mm, and rectangular wave loading is carried out for a certain length of time; ③Test result processing: Use PC to export the stress-strain curve during the test.

Images