NPR anchor rod energy absorption support rock burst prevention and control method

Abstract

The invention relates to the technical field of electric digital data processing, in particular to an NPR anchor rod energy absorption support rock burst prevention and control method which comprises the following steps: S1, obtaining NPR anchor rod kinetic parameters through a drop weight test; s2, determining surrounding rock stress control parameters to be selected through the rock mass rock burst excavation compensation model; s3, rock mass rock burst energy parameters are obtained through a uniaxial compression test and a true triaxial rock burst test; s4, energy parameters of the single NPR anchor rod are obtained through a dynamic impact tensile test; and S5, acquiring NPR anchor rod strength and energy coupling control parameters. The NPR anchor rod energy absorption support rock burst prevention and control method has important application value. According to the method, anchor rod configuration can be scientifically and reasonably designed based on specific geological conditions and stress states, and a supporting scheme is optimized, so that rockburst is effectively prevented and controlled, and the safety and economical efficiency of tunnel construction are improved.

Description

Technical Field

[0001] This application relates to the technical field of electrical digital data processing, and particularly to a method for preventing and controlling rock bursts by energy absorption support of NPR bolts. Background Technique

[0002] In deep-buried tunnel engineering, rock burst is a non-linear dynamic phenomenon in which a large amount of energy is instantaneously released by rock mass along the excavation unloading surface under high in-situ stress conditions, posing a great challenge to construction safety and tunnel stability. The essence of its occurrence lies in the sudden release of energy accumulated in the surrounding rock, and the key to its effective control lies in using the support system to absorb the energy released by the surrounding rock and reduce the degree of energy accumulation. Traditional rock burst control methods often have difficulty dealing with the complex geological environment of deep-buried tunnels, especially under high stress conditions. NPR (Negative Poisson's Ratio) bolts, as a new support technology, have good mechanical and energy absorption characteristics, especially for dynamic disasters caused by high in-situ stress in deep-buried tunnels. However, in practical applications, there are still difficulties in scientifically and reasonably designing NPR bolts to effectively control rock bursts.

[0003] Therefore, it is of important application value to propose a method for preventing and controlling rock bursts by energy absorption support of high-prestressed NPR bolts. This method can scientifically and reasonably design bolt configurations and optimize the support scheme based on specific geological conditions and stress states, thereby effectively preventing and controlling rock bursts and improving the safety and economy of tunnel construction. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a method for preventing and controlling rock bursts by energy absorption support of high-prestressed NPR bolts. On the basis of traditional strength support design, considering the influence of dynamic load rock bursts on support design, a strength-energy coupling secondary optimization rock burst control support design method based on dynamic characteristics is established, which can effectively reduce the risk of dynamic disasters in deep-buried tunnels, ensure construction safety, and conduct efficient prevention and control design for rock burst problems caused by dynamic loads.

[0005] This application relates to a method for preventing and controlling rock bursts by energy absorption support of NPR bolts. The improvement lies in that a method for preventing and controlling rock bursts by energy absorption support of NPR bolts is characterized in that the rock burst prevention and control method includes the following steps: Step S1, obtaining the dynamic parameters of NPR bolts through a drop hammer test; Step S2, determining the candidate stress control parameters of the surrounding rock through a rock burst excavation compensation model of the rock mass; Step S3, obtaining the rock burst energy parameters of the rock mass through uniaxial compression tests and true triaxial rock burst tests; Step S4, obtaining the energy parameters of a single NPR bolt through a dynamic impact tensile test; Step S5, obtain the NPR bolt strength and energy coupling control parameters; Step S5-1, obtain the NPR bolt strength control parameters through the stress control parameters to be selected for the surrounding rock; Step S5-2, obtain the NPR bolt energy control parameters through the rock burst energy parameters of the rock mass and the energy parameters of a single NPR bolt; Step S5-3, obtain the NPR bolt strength and energy coupling control parameters through the NPR bolt strength control parameters and the NPR bolt energy control parameters.

[0006] Preferably, step S1 includes: obtaining the NPR bolt dynamic parameters through a drop hammer test, and determining the maximum impact stress σ max of the NPR bolt, and the tensile amount L parameter of the NPR bolt, as shown in the following formula: ; ; Among them, A r is the cross-sectional area of the NPR bolt; L r is the length of the NPR bolt; H0 is the critical impact height; H is the drop height; A t is the sum of the cross-sectional areas of the fastening nut and the sleeve; is the lower limit constant resistance of the NPR bolt stick-slip movement under static load conditions; M is the mass of the drop hammer; C is the propagation speed of the stress wave in the NPR bolt rod body; ρ is the density of the NPR bolt rod body material; I A is the impact coefficient; g is the acceleration due to gravity; E is the elastic modulus of the NPR bolt; P0 is the constant resistance value of the NPR bolt.

[0007] Preferably, in step S2, determine the stress control parameters to be selected for the surrounding rock through a rock burst excavation compensation model for the rock mass, including the following steps: Step S2-1, determine the first stress, second stress, and third stress in any direction of the rock mass to be measured at the engineering site through a ground stress test method; Step S2-2, determine the maximum principal stress, intermediate principal stress, and minimum principal stress of the rock mass to be measured according to the first stress, second stress, and third stress;

[0008] Step S2-3, establish a rock burst excavation compensation model for the rock mass according to the maximum principal stress, intermediate principal stress, and minimum principal stress, including: obtaining the strength curve of the rock burst excavation compensation model based on the dynamic normal stress threshold σ Q of rock burst failure and the dynamic shear stress threshold τ Q of rock burst failure; Among them, the dynamic normal stress threshold σ Q of the rock burst failure is shown in the following formula: ; Among them, the dynamic shear stress threshold τ of the rock burst failure Q is shown in the following formula: ; Among them, σ 1d is the maximum principal stress value at the moment of rock burst occurrence, σ1 is the maximum principal stress, σ3 is the minimum principal stress, σ p is the normal stress of the static failure of the rock mass, τ p is the shear stress of the static failure of the rock mass.

[0009] Step S2-4, analyze the relationship between the strength curve and the strength envelope in the rock burst excavation compensation model of the rock mass.

[0010] Preferably, in step S2-4, analyzing the relationship between the strength curve and the strength envelope in the rock burst excavation compensation model of the rock mass includes the following steps: Step S2-4-1, set different test stress control parameters according to different NPR bolt parameters; Step S2-4-2, for each group of the test stress control parameters, input the test stress control parameters into the rock burst excavation compensation model of the rock mass to obtain the strength curve of the rock burst excavation compensation model of the rock mass; Step S2-4-3, analyze the strength curve of the rock burst excavation compensation model of the rock mass corresponding to each group of the test stress control parameters; if the strength curve in the rock burst excavation compensation model of the rock mass does not exceed the strength envelope, then determine the test stress control parameters as the stress control parameters to be selected for the surrounding rock.

[0011] Preferably, in step S3, obtain the rock burst energy parameters of the rock mass through uniaxial compression tests and true triaxial rock burst tests, including: Step S3-1, make the rock mass to be measured collected from the engineering site into the first rock mass specimen, conduct uniaxial compression tests on the first rock mass specimen, and determine the uniaxial failure peak strength corresponding to the failure strain of the first rock mass specimen; Step S3-2, draw the uniaxial compression curve of the failure strain and the uniaxial compression peak strength of the first rock mass specimen; Step S3-3, make the rock mass to be measured collected from the engineering site into the second rock mass specimen, conduct true triaxial rock burst tests on the second rock mass specimen, and obtain the maximum principal stress of the second rock mass specimen at the moment of rock burst occurrence; Step S3-4, substitute the peak strength corresponding to the failure strain of the first rock mass specimen and the maximum stress of the second rock mass specimen at the moment of rock burst occurrence into the rock burst excavation compensation model of the rock mass to determine the rock burst energy parameter E T as shown in the following formula: ; where: r is the radius of the circular tunnel, ∆H is the maximum depth of the rockburst occurrence position from its free face, σ c is the peak value of the uniaxial failure stress, ε c is the maximum strain value of uniaxial failure, and σ 1c is the maximum principal stress of the second rock mass specimen at the moment of rockburst occurrence.

[0012] Preferably, in step S4, through the dynamic impact tensile test, the energy parameters of a single NPR bolt are obtained, including: Step S4-1, through the dynamic impact tensile test of a single NPR bolt, determine the elastic deformation length, total deformation length, and impact load parameters of the single NPR bolt; Step S4-2, through the elastic deformation length, total deformation length, and impact load parameter values of the single NPR bolt, determine the total absorbed energy of the single NPR bolt; The total absorbed energy of the single NPR bolt is determined by the following formula: ; ; ;; where: P0 is the constant resistance value of the NPR bolt; U c is the elastic deformation length of the NPR bolt; U0 is the total deformation length of the NPR bolt; k is the stiffness of a single NPR bolt; E Ⅰ is the elastic energy absorbed by a single NPR bolt; E Ⅱ is the energy absorbed by the large deformation of a single NPR bolt in the structural yield stage.

[0013] Preferably, in step S5-1, through the stress control parameters to be selected for the surrounding rock, the strength control parameters of the NPR bolt are obtained, including: According to the formula , we get: ; ; F is the impact force of the NPR bolt drop hammer test, b1 is the spacing of a single NPR bolt in the stress control parameters, s1 is the row spacing of a single NPR bolt in the stress control parameters, and n1 is the number of NPR bolts in the stress control parameters; is the control stress of the NPR bolt; Step S5-2, through the rockburst energy parameters of the rock mass and the energy parameters of the single NPR bolt, obtain the energy control parameters of the NPR bolt, including: ; According to , then ; b2 is the spacing of a single NPR bolt in the energy control parameter, s2 is the row spacing of a single NPR bolt in the energy control parameter, and n2 is the number of NPR bolts in the energy control parameter; Step S5-3: Obtain the strength and energy coupling control parameters of the NPR bolt through the NPR bolt strength control parameter and the NPR bolt energy control parameter, including: ; ; where n is the number of NPR bolts for coupled control, taking the maximum value of n1 and n2; Take and the minimum value in.

[0014] Compared with the prior art, the beneficial effects of the present invention are: The present invention determines the stress state of the rock mass to be measured at the engineering site through the in-situ stress test method, establishes a rockburst excavation compensation model for the rock mass, and determines the candidate stress control parameters for the surrounding rock; in combination with the NPR bolt drop hammer test, determines the NPR bolt strength control; according to the surrounding rock energy theory model, determines the excess energy after the rock mass undergoes rockburst; in combination with the NPR bolt dynamic impact tension test, determines the energy that the NPR bolt can absorb; according to the NPR bolt strength and energy control, determines the secondary optimization of the strength and energy coupling NPR bolt parameters of the rock mass. It can effectively reduce the risk of rockburst occurrence and ensure construction safety. Description of the Drawings

[0015] Figure 1 is one of the flowcharts of the NPR bolt energy-absorbing support rockburst prevention and control method involved in the present invention; Figure 2 is the second flowchart of the NPR bolt energy-absorbing support rockburst prevention and control method involved in the present invention; Figure 3 is the in-situ stress test schematic diagram involved in the present invention; Figure 4-1 is the schematic diagram of simulating the original rock stress state during the rockburst loading process involved in the present invention; Figure 4-2 is the schematic diagram of the rockburst excavation compensation effect 1 involved in the present invention; Figure 4-3 is the schematic diagram of the rockburst excavation compensation effect 2 involved in the present invention; Figure 5-1 is the schematic diagram of the uniaxial compression curve involved in the present invention; Figure 5-2 is the schematic diagram of the rockburst curve involved in the present invention; Figure 6Schematic diagram of rockburst control in deep-buried tunnels related to the present invention; Among them, 1, tunnel; 2, rockburst occurrence location; 3, rockburst control area; 4, surrounding rock. Detailed implementation manners

[0016] To better understand the present invention, the content of the present invention will be further described below in conjunction with the specification drawings and examples.

[0017] As Figure 1 and Figure 2 shown, the present application relates to a method for preventing and controlling rockburst by energy absorption support of NPR bolts. The improvement lies in that the method for preventing and controlling rockburst includes the following steps: Step S1, obtaining the dynamic parameters of NPR bolts through a drop hammer test.

[0018] Step S2, determining the candidate stress control parameters of the surrounding rock through a rockburst excavation compensation model of the rock mass.

[0019] Step S3, obtaining the rockburst energy parameters of the rock mass through a uniaxial compression test and a true triaxial rockburst test.

[0020] Step S4, obtaining the energy parameters of a single NPR bolt through a dynamic impact tension test.

[0021] Step S5, obtaining the coupling control parameters of the strength and energy of NPR bolts.

[0022] Among them, the drop hammer test involved in step S1 is a test for evaluating the impact resistance of materials under dynamic loads. Start the drop hammer release device to make the drop hammer freely fall from a predetermined height and impact the specimen. At the moment when the drop hammer impacts the specimen, a huge impact force will be generated, causing the specimen to deform, crack or break, etc. After the impact test, according to the test purpose and requirements, parameters related to the impact performance of the material can be measured, such as impact absorption energy, fracture toughness, etc.

[0023] Specifically, step S1 obtains the dynamic parameters of NPR bolts through a drop hammer test to determine the maximum impact stress σ max of the NPR bolt, that is, the dynamic parameter σ max of a single NPR bolt in the drop hammer test; and the tensile amount L parameter of the NPR bolt, as shown in the following formula: ; ; where A r and L r are the cross-sectional area and length of the NPR bolt respectively; H0 is the critical impact height; H is the drop distance; A t is the sum of the cross-sectional areas of the fastening nut and the sleeve; is the lower limit constant resistance of the NPR bolt's stick-slip movement under static load conditions; M is the mass of the drop hammer; C is the propagation speed of stress waves in the NPR bolt rod; ρ is the density of the NPR bolt rod material; I A is the impact coefficient; g is the acceleration due to gravity; E is the elastic modulus of the NPR bolt.

[0024] Step S2, determine the stress control parameters to be selected for the surrounding rock through the rock burst excavation compensation model for rock masses, including the following steps: Step S2-1, determine the first stress, second stress, and third stress in any direction of the rock mass to be measured at the engineering site through the in-situ stress measurement method. Specifically, determine the first stress, second stress, and third stress in any direction of the rock mass to be measured at the engineering site through the in-situ stress measurement method. Usually, measure the three stresses in the X, Y, and Z directions to facilitate the stress analysis in the three-dimensional rectangular coordinate system. The specific measurement method can be: through the external load conditions, conduct a stress analysis, calculate the magnitude and direction of the internal force borne by the rock mass to be measured, and the stresses in the three directions in the corresponding Cartesian coordinate system can be obtained.

[0025] Step S2-2, determine the maximum principal stress, intermediate principal stress, and minimum principal stress of the rock mass to be measured according to the first stress, second stress, and third stress. Specifically, in practice, according to the first stress, second stress, and third stress, the maximum principal stress, intermediate principal stress, and minimum principal stress of the rock mass to be measured can be determined. The specific calculation method is: through the general stress in the Cartesian coordinate system, find the normal stress and tangential stress on its inclined plane. Assume that the area of the inclined plane in the rock mass to be measured is dA, and the θ angle is any angle (the inclination angle of the inclined plane). Conduct a stress analysis on the inclined plane. Since the stress multiplied by the corresponding area is equal to the force, based on the equilibrium relationship, the resultant force in each direction is 0, and then the position of the principal plane can be determined, and the maximum principal stress, intermediate principal stress, and minimum principal stress can be determined.

[0026] Specifically, as Figure 3 shown, OB is the plane in the Y direction; OA is the plane in the X direction; AB is the plane formed by the inclined plane AB. Let the area of the inclined plane SAB be dA, and the θ angle is the inclination angle of the inclined plane.

[0027] From the stress analysis, it can be known that: The area S of the OB plane OB is: ; The area S of the OA plane OA is: ; The F on the inclined section x is: ; The F on the inclined section y is: ; F on the inclined section x The stress generated P x for: ; F on the inclined section y The stress generated P y for: ; Normal stress σ generated on the inclined section θ for: ; Shear stress τ generated on the inclined section θ for: .

[0028] Among them, σ y is the normal stress in the y direction; σ x is the normal stress in the x direction; τ x is the shear stress in the x direction; τ y is the shear stress in the y direction; τ is the shear stress, τ x =τ y =τ.

[0029] Compare the normal stress σ generated on the above inclined section θ , F on the inclined section x The stress generated P x , and F on the oblique section y The stress generated P y According to the size of , select the maximum principal stress σ1, the middle principal stress σ2 and the minimum principal stress σ3.

[0030] Step S2-3, establishing a rockburst excavation compensation model according to the maximum principal stress, the intermediate principal stress and the minimum principal stress.

[0031] Specifically, the establishment of rockburst excavation compensation model includes: based on the dynamic normal stress threshold σ of rockburst damage Q and the dynamic shear stress threshold τ of rockburst failure Q Obtain strength curves in rock mass rockburst excavation compensation models.

[0032] Among them, the dynamic normal stress (normal stress) threshold σ of rock burst damage Q As shown below: ; Dynamic shear stress threshold τ of rockburst failure Q As shown below: ; Among them, σ 1d is the maximum principal stress value at the time of rock burst, σ1 is the maximum principal stress, σ3 is the minimum principal stress, and σ p is the normal stress of rock mass static failure, τ pis the shear stress of static rock mass failure.

[0033] Step S2-4, analyze the relationship between the strength curve and the strength envelope in the rockburst excavation compensation model of the rock mass, including the following steps: Step S2-4-1, set several groups of test stress control parameters according to different NPR bolt parameters. Specifically, in the specific implementation, the NPR bolt parameters may include the spacing, row spacing and quantity of NPR bolts. Technicians set several groups of NPR bolt parameters to be tested according to different support stresses. Table 1 is an example table of a group of support parameters to be tested provided by the embodiment of the present application, as shown in Table 1:

[0034] Table 1 The test stress control parameters are shown in the following formula: ; F is the impact force of the NPR bolt drop hammer test, b1 is the spacing of a single NPR bolt in the stress control parameters, s1 is the row spacing of a single NPR bolt in the stress control parameters, and n1 is the quantity of NPR bolts in the stress control parameters; the NPR bolt control stress .

[0035] Step S2-4-2, for each group of test stress control parameters, input the test stress control parameters into the rockburst excavation compensation model of the rock mass. Specifically, in the implementation, for each group of support parameters to be tested, technicians input the support parameters to be tested into the rockburst excavation compensation model of the rock mass to obtain the rockburst excavation compensation model of the rock mass as shown in Figure 4-2 , 4-3 .

[0036] Step S2-4-3, analyze the strength curve in the rockburst excavation compensation model of the rock mass corresponding to each group of the test stress control parameters to be tested; if the strength curve in the rockburst excavation compensation model of the rock mass does not exceed the strength envelope, determine the test stress control parameters as the stress control parameters to be selected for the surrounding rock. Specifically, the strength envelope (Mohr-coulomb failure envelope) is a line used to describe the strength characteristics of rocks in rock mechanics. By conducting a series of strength tests on rocks under different stress states (such as triaxial compression tests, etc.), the obtained failure points are connected in the stress space to form a line. The strength envelope represents the failure conditions of rock materials under different stress combinations, that is, when the stress state of the rock reaches a certain point on the strength envelope, the rock will fail. Different rocks have different strength envelopes, and their shapes and positions reflect the inherent strength characteristics of the rocks and their responses to different stress states.

[0037] In the original rock stress state diagram of rockburst loading simulation, the strength envelope can be used to judge the stability of rocks under a given original rock stress state. If the original rock stress state point is located inside the strength envelope, it indicates that the rock is in a stable state and has not reached the failure condition; while when the original rock stress state point falls on or exceeds the strength envelope, it means that the rock may be damaged and there are instability risks such as rockburst.

[0038] In implementation, the rockburst excavation compensation model for rock mass can simulate the stress changes of the rock mass to be measured. For example, Figure 4-1 as shown, the rock mass to be measured is in a stress stable state, and there is a strength curve between every two stresses. The strength curve corresponding to the largest arc does not exceed the strength envelope (the diagonal line in the figure), indicating stress stability. If no support is carried out after excavation, as Figure 4-2 shown, the strength curve may move to the left and exceed the upper strength envelope. After inputting the support parameters to be tested, it is equivalent to adding support members to the excavation surface of the rock mass to be measured. As Figure 4-3 shown, the strength curve will move to the right and return below the strength envelope, thus returning to the stress stable state.

[0039] Specifically, as Figure 4-1 shown, the original rock stress state before the occurrence of rockburst is simulated through stress loading. At this time, the rockburst loading stress curve does not exceed the upper strength envelope and is in a stress stable state. As Figure 4-2 shown, after the excavation of the chamber, the stress at the free face is unloaded, and the minimum principal stress σ 3d drops to 0 at the moment of rockburst occurrence at the free face. This process is the excavation unloading effect 1. The stress curve of the rock mass to be measured exceeds the strength envelope, which may lead to the occurrence of rockburst. However, if high prestress is applied to the free face in a timely manner after excavation (such as setting support members to carry out NPR support on the free face to avoid the occurrence of rockburst), step S2-4 can be implemented, and the corresponding test stress control parameters are set according to different NPR supports; and the test stress control parameters are input into the rockburst excavation compensation model for rock mass, the free face obtains stress compensation, and the minimum principal stress σ3 increases from 0 to σ 3d , and the minimum principal stress compensation in the direction from 0 to σ 3d is obtained. This process is called the excavation compensation effect 1. As Figure 4-3 shown, after the excavation of the chamber, the stress at the free face is unloaded, and the maximum principal stress σ 1d increases to σ 1b, this process is the excavation unloading effect 2. The stress curve of the rock mass to be measured exceeds the strength envelope, which may lead to rockburst. However, if after excavation, a high prestress is applied to the free face in a timely manner (such as setting support members to carry out NPR support on the free face), that is, corresponding test stress control parameters are set according to different NPR supports; and the stress control parameters are input into the rockburst excavation compensation model of the rock mass, the free face obtains stress compensation, and the maximum principal stress σ1 changes from σ 1b to σ 1d , and the maximum principal stress compensation in the direction from σ 1b to σ 1d is obtained. This process is called the excavation compensation effect 2. The rock mass to be measured returns to the stress stable state. At this time, the strength curve in the rockburst excavation compensation model of the rock mass does not exceed the strength envelope, then the test stress control parameters used at this time are determined as the candidate stress control parameters for the surrounding rock.

[0040] Step S3, through uniaxial compression tests and true triaxial rockburst tests, obtain the rockburst energy parameters of the rock mass, including: Step S3-1, make the rock mass to be measured collected from the engineering site into the first rock mass specimen, and conduct uniaxial compression tests on the first rock mass specimen to determine the uniaxial failure peak strength corresponding to the failure strain of the first rock mass specimen. Specifically, in implementation, technicians collect the rock mass to be measured from the engineering site and make it into the first rock mass specimen. For the uniaxial compression test, the first rock mass specimen can be made into a cylindrical specimen with a diameter of 100 mm and a height of 200 mm. The uniaxial compression test is to apply axial pressure on the first rock mass specimen and calculate the uniaxial failure stress peak σ c and the uniaxial failure maximum strain value ε c .

[0041] Step S3-2, draw the uniaxial compression curve of the failure strain and uniaxial compression peak strength of the first rock mass specimen.

[0042] Specifically, as Figure 5-1 shown, the abscissa is the strain value of the first rock mass specimen during the uniaxial compression test, and the ordinate is the stress value.

[0043] Step S3-3, make the rock mass to be measured collected from the engineering site into the second rock mass specimen, and conduct true triaxial rockburst tests on the second rock mass specimen to obtain the maximum stress σ 1c. Specifically, during implementation, technicians collected the rock mass to be tested from the engineering site and made a cuboid specimen with side lengths of 100mm×100mm×200mm as the second rock mass specimen for the true triaxial rockburst test. The second rock mass specimen was placed under the first stress, the second stress, and the third stress states to simulate the excavation effect of the rock mass in actual engineering and the excavation compensation effect after adding support members.

[0044] As Figure 5-2 shown, the abscissa is the strain of the second rock mass specimen during the true triaxial rockburst test, and the ordinate is the stress.

[0045] During implementation, since the failure strain of the uniaxial compression test is easily measured, but the rockburst strain during the true triaxial rockburst test is affected by the strains in three stress directions, the determined stress-strain curve cannot be represented in a plane coordinate system. Therefore, in the embodiments of the present application, it is assumed that the failure strain of the first rock mass specimen is equal to the rockburst strain of the second rock mass specimen, and the rockburst strain value of the second rock mass specimen can be obtained. At the same time, based on the maximum stress value of the second rock mass specimen at the moment of rockburst obtained in the true triaxial rockburst test, a rockburst curve passing through the origin of the coordinates as Figure 5-2 shown can be obtained. The abscissa is the rockburst strain value of the second rock mass specimen, that is, the failure strain value of the first rock mass specimen; the ordinate is the maximum stress value of the second rock mass specimen obtained during the true triaxial rockburst test.

[0046] Step S3-4: Substitute the peak strength corresponding to the failure strain of the first rock mass specimen determined above and the maximum stress at the moment of rockburst of the second rock mass specimen into the rockburst excavation compensation model of the rock mass to determine the rockburst energy parameter of the rock mass.

[0047] Specifically, as Figure 6 shown in the schematic diagram of deep-buried tunnel rockburst control, let the radius of tunnel 1 be r, and the distance between the rockburst occurrence position 2 and the tunnel wall be ∆H, that is, the maximum depth of the rockburst occurrence position from the free face; then the depth of the rockburst control area 3 is 1.5 times the maximum depth of the rockburst occurrence position from its free face. Outside the rockburst control area 3 is the surrounding rock 4.

[0048] The rockburst energy parameter of the rock mass is: ; In the formula: r is the radius of the circular tunnel, ∆H is the maximum depth of the rockburst occurrence position from the free face, σ c is the peak value of the uniaxial failure stress, ε c is the maximum uniaxial failure strain value, and σ 1c is the maximum principal stress of the second rock mass specimen at the moment of rockburst.

[0049] Step S4. Obtain the energy parameters of a single NPR bolt through a dynamic impact tension test, including: Step S4-1. Determine the elastic deformation length, total deformation length, and impact load parameters of a single NPR bolt through a dynamic impact tension test on the single NPR bolt. Step S4-2. Determine the total absorbed energy of a single NPR bolt based on the elastic deformation length, total deformation length, and impact load parameter values of the single NPR bolt. The total absorbed energy of the single NPR bolt is determined by the following formula: ; ; ; where: P0 is the constant resistance value of the NPR bolt; U c is the elastic deformation length of the NPR bolt; U0 is the total deformation length of the NPR bolt; k is the stiffness of the NPR bolt; E Ⅰ is the elastic energy absorbed by the NPR bolt; E Ⅱ is the energy absorbed by the large deformation of the NPR bolt in the structural yield stage.

[0050] Preferably, in the above steps, steps S1 to S4 can be regarded as the first-level optimization, specifically referring to the initial selection of the strength control parameters and energy control parameters of the NPR bolt in controlling rockburst.

[0051] Step S5. Obtain the strength and energy coupling control parameters of the NPR bolt, including: Step S5-1. Obtain the strength control parameters of the NPR bolt through the stress control parameters to be selected for the surrounding rock, including: According to the formula , we get: ; ; F is the impact force of the drop hammer test of the NPR bolt, b1 is the spacing of a single NPR bolt in the stress control parameters, s1 is the row spacing of a single NPR bolt in the stress control parameters, and n1 is the number of NPR bolts in the stress control parameters; Step S5-2. Obtain the energy control parameters of the NPR bolt through the rockburst energy parameters of the rock mass and the energy parameters of the single NPR bolt, including: ; According to , then ; b2 is the spacing of a single NPR bolt in the energy control parameters, s2 is the row spacing of a single NPR bolt in the energy control parameters, and n2 is the number of NPR bolts in the energy control parameters; Preferably, steps S5-1 and S5-2 can be regarded as secondary optimization, specifically referring to the optimization of NPR bolt strength and energy coupling control parameters. In step S5-3, the NPR bolt strength and energy coupling control parameters are obtained through the NPR bolt strength control parameters obtained in step S5-1 and the NPR bolt energy control parameters obtained in step S5-2, including: ; ; Among them, n is the number of NPR bolts for coupling control, taking the maximum value of n1 and n2; Take and the minimum value in.

[0052] After the design is completed, a rockburst prevention and control design plan for deep-buried tunnel engineering is formed for on-site application, and after the application, on-site monitoring and evaluation feedback are carried out on the engineering site. Among them, the monitoring and evaluation feedback includes surrounding rock deformation evaluation, structural stress evaluation, energy change evaluation, and explosion pit depth evaluation.

[0053] The surrounding rock deformation evaluation is to divide the surrounding rock into zones of fragmentation through borehole peeping and radar detection, and measure the range of the loosened circle of the surrounding rock after support.

[0054] The structural stress evaluation is to install bolt load cells on the NPR bolts used for support, monitor the stress of the NPR bolts during and after construction, and compare and evaluate it with the ultimate load of the bolts.

[0055] The energy change evaluation is to evaluate the control of on-site energy change by NPR bolts through microseismic monitoring equipment during tunnel excavation.

[0056] The explosion pit depth evaluation is based on the area of the tunnel wall damaged by rockburst and the volume of the rock mass that has fallen off to evaluate the scale of the rockburst disaster and then evaluate the prevention and control effect of NPR bolts.

[0057] In this embodiment, the rockburst prevention and control design method for deep-buried tunnel engineering is feedback-optimized through the results of various monitoring and evaluations.

[0058] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memory, CD-ROM, optical memory, etc.) that contain computer-usable program code.

[0059] The present application is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram can be implemented by computer program instructions, and the combination of the flows and / or blocks in the flowchart and / or block diagram can also be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate means for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0060] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured article including instruction means, and the instruction means implements the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0061] These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0062] The above are only embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention pending approval.

Claims

1. A method for preventing and controlling rock bursts by energy absorption support of NPR bolts, characterized in that, The rockburst prevention and control method includes the following steps: Step S1, obtaining the dynamic parameters of NPR bolts through a drop hammer test; Step S2, determining the candidate stress control parameters of the surrounding rock through a rockburst excavation compensation model of the rock mass; Step S3, obtaining the rockburst energy parameters of the rock mass through uniaxial compression tests and true triaxial rockburst tests; Step S4, obtaining the energy parameters of a single NPR bolt through a dynamic impact tension test; Step S5, obtaining the strength and energy coupling control parameters of NPR bolts; Step S5-1, obtaining the strength control parameters of NPR bolts through the candidate stress control parameters of the surrounding rock; Step S5-2, obtaining the energy control parameters of NPR bolts through the rockburst energy parameters of the rock mass and the energy parameters of a single NPR bolt; Step S5-3, obtaining the strength and energy coupling control parameters of NPR bolts through the strength control parameters and energy control parameters of NPR bolts.

2. The NPR bolt energy absorption support method for rock burst prevention and control according to claim 1, wherein Step S1 includes: obtaining the dynamic parameters of the NPR bolt through a drop hammer test to determine the maximum impact stress σ of the NPR bolt max , and the tensile amount L parameter of the NPR bolt, as shown in the following formula: ； ； Among them, A r is the cross-sectional area of the NPR bolt; L r is the length of the NPR bolt; H0 is the critical impact height; H is the drop height; A t is the sum of the cross-sectional areas of the fastening nut and the sleeve; is the lower limit constant resistance of the stick-slip movement of the NPR bolt under static load conditions; M is the mass of the drop hammer; C is the propagation speed of the stress wave in the NPR bolt rod; ρ is the density of the NPR bolt rod material; I A is the impact coefficient; g is the acceleration due to gravity; E is the elastic modulus of the NPR bolt; P0 is the constant resistance value of the NPR bolt.

3. The NPR bolt energy absorption support method for preventing and controlling rock bursts according to claim 1, characterized in that, Step S2, determining the candidate stress control parameters of the surrounding rock through a rockburst excavation compensation model of the rock mass, including the following steps: Step S2-1, determining the first stress, second stress, and third stress in any direction of the rock mass to be measured at the engineering site through a ground stress test method; Step S2-2, determining the maximum principal stress, intermediate principal stress, and minimum principal stress of the rock mass to be measured according to the first stress, second stress, and third stress; Step S2-3, establish a rockburst excavation compensation model for rock mass according to the maximum principal stress, intermediate principal stress and minimum principal stress, including: based on the dynamic normal stress threshold σ Q of rockburst failure and the dynamic shear stress threshold τ Q of rockburst failure, obtain the strength curve of the rockburst excavation compensation model for rock mass; Among them, the dynamic normal stress threshold σ of the rockburst failure Q is shown as follows: ； Among them, the dynamic shear stress threshold τ of the rockburst failure Q is shown as follows: ； Among them, σ 1d is the maximum principal stress value at the time of rock burst occurrence, σ1 is the maximum principal stress, σ3 is the minimum principal stress, and σ p is the normal stress of static rock mass failure, and τ p is the shear stress of static rock mass failure; Step S2-4, analyzing the relationship between the strength curve and the strength envelope in the rockburst excavation compensation model of the rock mass.

4. The NPR bolt energy absorption support method for rockburst prevention and control according to claim 3, characterized in that, Step S2-4, analyzing the relationship between the strength curve and the strength envelope in the rockburst excavation compensation model of the rock mass, including the following steps: Step S2-4-1, setting different test stress control parameters according to different NPR bolt parameters; Step S2-4-2, for each group of the test stress control parameters, inputting the test stress control parameters into the rockburst excavation compensation model of the rock mass to obtain the strength curve of the rockburst excavation compensation model of the rock mass; Step S2-4-3, analyzing the strength curve of the rockburst excavation compensation model of the rock mass corresponding to each group of the test stress control parameters; if the strength curve in the rockburst excavation compensation model of the rock mass does not exceed the strength envelope, determining the test stress control parameters as the candidate stress control parameters of the surrounding rock.

5. The NPR bolt energy absorption support method for rock burst prevention and control according to claim 1, characterized in that, Step S3, obtaining the rockburst energy parameters of the rock mass through uniaxial compression tests and true triaxial rockburst tests, including: Step S3-1, making the rock mass to be measured collected from the engineering site into a first rock mass specimen, conducting a uniaxial compression test on the first rock mass specimen, and determining the uniaxial failure peak strength corresponding to the failure strain of the first rock mass specimen; Step S3-2, plotting the uniaxial compression curve of the failure strain and the uniaxial compression peak strength of the first rock mass specimen; Step S3-3, making the rock mass to be measured collected from the engineering site into a second rock mass specimen, conducting a true triaxial rockburst test on the second rock mass specimen, and obtaining the maximum principal stress of the second rock mass specimen at the moment of rockburst occurrence; Step S3-4: Substitute the peak strength corresponding to the failure strain of the first rock mass specimen and the maximum stress of the second rock mass specimen at the moment of rockburst into the rockburst excavation compensation model for rock mass to determine the rockburst energy parameter E of the rock mass T , as shown in the following formula: ； where: r is the radius of the circular tunnel, ∆H is the maximum depth from the rockburst occurrence position to its free face, σ c is the peak value of the uniaxial failure stress, ε c is the maximum strain value of the uniaxial failure, and σ 1c is the maximum principal stress of the second rock mass specimen at the moment of rockburst occurrence.

6. The NPR bolt energy absorption support method for rock burst prevention and control according to claim 1, wherein Step S4, obtaining the energy parameters of a single NPR bolt through a dynamic impact tension test, including: Step S4-1: Determine the elastic deformation length, total deformation length, and impact load parameters of a single NPR bolt through the dynamic impact tensile test of a single NPR bolt. Step S4-2: Determine the total absorbed energy of a single NPR bolt based on the elastic deformation length, total deformation length, and impact load parameter values of the single NPR bolt. The total absorbed energy of the single NPR bolt is determined by the following formula: ； ； ； Where: P0 is the constant resistance value of the NPR bolt; U c is the elastic deformation length of the NPR bolt; U0 is the total deformation length of the NPR bolt; k is the stiffness of a single NPR bolt; E Ⅰ is the elastic energy absorbed by a single NPR bolt; E Ⅱ is the energy absorbed by the large deformation of a single NPR bolt in the structural yield stage.

7. The NPR bolt energy absorption support method for rock burst prevention and control according to claim 1, characterized in that, Step S5-1: Obtain the strength control parameters of the NPR bolt through the stress control parameters to be selected for the surrounding rock, including: According to the formula , we get: ； ； F is the impact force of the drop hammer test of the NPR bolt, b1 is the spacing of a single NPR bolt in the stress control parameters, s1 is the row spacing of a single NPR bolt in the stress control parameters, and n1 is the number of NPR bolts in the stress control parameters; is the control stress of the NPR bolt; Step S5-2: Obtain the energy control parameters of the NPR bolt through the rockburst energy parameters of the rock mass and the energy parameters of the single NPR bolt, including: ； According to , then ; b2 is the spacing of a single NPR bolt in the energy control parameters, s2 is the row spacing of a single NPR bolt in the energy control parameters, and n2 is the number of NPR bolts in the energy control parameters. Step S5-3: Obtain the strength and energy coupling control parameters of the NPR bolt through the strength control parameters and energy control parameters of the NPR bolt, including: ； ； Among them, n is the number of NPR bolts for coupling control, taking the maximum value of n1 and n2; Take and the minimum value in.

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