Dynamic mechanical blasting analysis method for tunnel rock mass

Abstract

The invention discloses a tunnel rock mass dynamic mechanical blasting analysis method, and relates to the technical field of tunnel blasting, and the tunnel rock mass dynamic mechanical blasting analysis method comprises the following steps: obtaining the strain rate of a rock mass near a blast hole; calculating the dynamic structural strength of the rock mass in the blasting process according to the strain rate; and calculating the blasting damage range of the rock mass according to the dynamic structural strength. According to the dynamic mechanical blasting analysis method for the tunnel rock mass, the material mechanical property of the rock mass is reflected through the strain rate, and the change of the dynamic structural strength of the rock mass along with the dynamic blasting process is reflected through the dynamic structural strength; the blasting damage analysis result of the rock mass combines the material mechanical property of the rock mass and the dynamic process of blasting, so that the blasting damage process of the rock mass in analysis is more close to the dynamic process of blasting, the blasting damage range analysis result of the rock mass is more close to the actual result, and the safety in the tunnel blasting construction process is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel blasting, and particularly relates to a method for analyzing the dynamic mechanical blasting of tunnel rock masses. Background Technique

[0002] Tunnel blasting excavation construction is a common tunnel construction method. By drilling holes in rock masses and filling them with explosives for blasting, the purpose of tunnel excavation can be achieved. Conducting blasting analysis before blasting excavation construction can help construction personnel predict the damage range of the rock mass caused by blasting and optimize blasting parameters, thereby improving construction safety. However, existing blasting analysis methods mainly rely on the static mechanical parameters of the rock mass and do not fully consider the dynamic factors during the blasting process, resulting in the analysis results often being unable to accurately reflect the actual damage situation of the rock mass during the blasting process, and there being a large deviation between the analysis results and the actual situation. Summary of the Invention

[0003] The main object of the present invention is to propose a method for analyzing the dynamic mechanical blasting of tunnel rock masses, aiming to solve the technical problem in the prior art that existing blasting analysis methods mainly rely on the static mechanical parameters of the rock mass, resulting in a large deviation between the analysis results and the actual situation.

[0004] To achieve the above object, the method for analyzing the dynamic mechanical blasting of tunnel rock masses proposed by the present invention includes the steps of: obtaining the strain rate of the rock mass near the blasting hole; calculating the dynamic structural strength of the rock mass during the blasting process according to the strain rate; and calculating the blasting damage range of the rock mass according to the dynamic structural strength.

[0005] In an embodiment, the step of obtaining the strain rate of the rock mass near the blasting hole includes: determining the vibration velocity of the hole wall particles of the rock mass in the blasting hole; determining the vibration velocity of particles at any distance from the blasting hole according to the vibration velocity of the hole wall particles and the propagation velocity of the blasting shock wave in the rock mass; and determining the strain rate of the rock mass at this position according to the vibration velocity of the particles.

[0006] In an embodiment, the step of determining the vibration velocity of the hole wall particles of the rock mass in the blasting hole includes: measuring the density ρ of the rock mass in the blasting hole before blasting 0 ; determining the impact pressure P of the blasting on the rock mass in the blasting hole according to the blasting equivalent b ; the initial vibration velocity of the hole wall particles wherein, a and b are parameters related to the lithology; a is the propagation velocity of sound waves in the rock mass; b = 1 - 1.5.

[0007] In one embodiment, the step of determining the particle vibration velocity at any distance from the blast hole according to the vibration velocity of the hole wall particles and the propagation velocity of the blasting shock wave in the rock mass includes: measuring and calculating the distance x of the calculation position from the blast hole; measuring the radius r of the blast hole b ; the particle vibration velocity at the calculation position where α is the stress wave attenuation coefficient.

[0008] In one embodiment, the step of determining the strain rate of the rock mass at this position according to the particle vibration velocity includes: taking the derivative of the particle vibration velocity at the calculation position to obtain the strain rate of the rock mass at this position

[0009] In one embodiment, the step of calculating the dynamic structural strength of the rock mass during blasting according to the strain rate includes:

[0010] Calculating the dynamic compressive strength of the rock mass according to the strain rate;

[0011] Calculating the dynamic tensile strength of the rock mass according to the strain rate.

[0012] In one embodiment, the step of calculating the dynamic compressive strength of the rock mass according to the strain rate includes: measuring the static compressive strength σ of the rock mass c ; according to the compressive dynamic growth factor and the strain rate & to calculate the dynamic compressive strength [σ cd of the rock mass; where K is the static compressive strength reduction coefficient, taking 0.4.

[0013] In one embodiment, the step of calculating the dynamic tensile strength of the rock mass according to the strain rate includes: determining the type of the rock mass; determining the characteristic strain rate & corresponding to each type of the rock mass according to the empirical formula 0 and the dynamic growth coefficient α; measuring the static tensile strength σ corresponding to each type of the rock mass t ; according to the tensile dynamic growth factor and the strain rate & to calculate the dynamic tensile strength [σ td of the rock mass.

[0014] In one embodiment, the step of calculating the blasting failure range of the rock mass according to the dynamic structural strength includes: determining the stress intensity σ at any distance from the blast hole according to the transmission law of the stress wave i ; according to the dynamic compressive strength [σ cd being equal to the stress intensity σ i to calculate the compression failure range of the rock mass Among them, B is a parameter that comprehensively reflects the dynamic response characteristics of the rock mass and the stress wave attenuation characteristics. X is the distance from the calculation position to the blasting hole; according to the dynamic tensile strength [σ td being equal to the stress intensity σ i , calculate the tensile failure range of the rock mass. Combined with the compressive failure range R c and the tensile failure range R t , determine the blasting failure range.

[0015] In one embodiment, the step of determining the stress intensity σ i at any distance from the blasting hole according to the transmission law of stress waves includes: the radial stress at the position x from the blasting hole The tangential stress σ θ at the position x from the blasting hole = -bσ ρ ; where b = v d / (1 - v d ); v d is the dynamic Poisson's ratio of the rock mass; the stress intensity

[0016] The tunnel rock mass dynamic mechanics blasting analysis method proposed by the present invention, before excavating a tunnel by blasting, preset blasting holes in the tunnel rock mass, obtain the mechanical parameters of the rock mass and the distance between the sampling position and the preset blasting holes by sampling the rock mass, obtain the strain rate of the rock mass near the blasting holes through the mechanical parameters, and then calculate the dynamic structural strength of the rock mass during blasting by using the strain rate, so as to calculate the blasting failure range of the rock mass through the dynamic structural strength of the rock mass. The material mechanical properties of the rock mass are reflected by the strain rate, and the change of the dynamic structural strength of the rock mass during the dynamic process of blasting is reflected by the dynamic structural strength, so that the blasting failure analysis result of the rock mass combines the material mechanical properties of the rock mass and the dynamic process of blasting, making the blasting failure process of the rock mass in the analysis more conform to the dynamic process of blasting, the blasting failure range analysis result of the rock mass closer to the actual result, effectively improving the accuracy of the blasting analysis result, and thus improving the safety during the tunnel blasting construction process. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0018] Figure 1 Schematic diagram of the process of an embodiment of the dynamic mechanical blasting analysis method for tunnel rock mass provided by the present invention.

[0019] The realization of the object of the present invention, its functional characteristics and advantages will be further described in conjunction with the embodiments and with reference to the accompanying drawings. Specific embodiments

[0020] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0021] It should be noted that if there are directional indications (such as up, down, left, right, front, back...) involved in the embodiments of the present invention, the directional indications are only used to explain the relative positional relationship and movement conditions between components in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0022] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, if "and / or" or "and / or" appears throughout the text, its meaning includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or a solution where A and B are satisfied simultaneously. In addition, the technical solutions between the embodiments can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0023] Existing blasting analysis methods mainly rely on the static mechanical parameters of rock masses and do not fully consider the dynamic factors during the blasting process, resulting in the analysis results often being unable to accurately reflect the actual damage situation of the rock mass during the blasting process, and there is a large deviation between the analysis results and the actual situation.

[0024] The present invention proposes a dynamic mechanical blasting analysis method for tunnel rock mass, including the steps of:

[0025] S10: Obtain the strain rate of the rock mass near the blast hole;

[0026] S20: Calculate the dynamic structural strength of the rock mass during the blasting process according to the strain rate;

[0027] S30: Calculate the blasting failure range of the rock mass according to the dynamic structural strength.

[0028] Please refer to Figure 1 , the dynamic mechanical blasting analysis method for tunnel rock mass proposed by the present invention, before tunneling by blasting method, preset blasting holes in the tunnel rock mass, obtain the mechanical parameters of the rock mass and the distance between the sampling position and the preset blasting holes by sampling the rock mass, obtain the strain rate of the rock mass near the blasting holes through the mechanical parameters, and then calculate the dynamic structural strength of the rock mass during the blasting process by using the strain rate, so as to calculate the blasting failure range of the rock mass through the dynamic structural strength of the rock mass. The material mechanical properties of the rock mass are reflected by the strain rate, and the change of the dynamic structural strength of the rock mass during the dynamic process of blasting is reflected by the dynamic structural strength, so that the blasting failure analysis result of the rock mass combines the material mechanical properties of the rock mass and the dynamic process of blasting, so that the blasting failure process of the rock mass in the analysis is more in line with the dynamic process of blasting, and the analysis result of the blasting failure range of the rock mass is closer to the actual result, effectively improving the accuracy of the blasting analysis result, and thus improving the safety during the tunnel blasting construction process.

[0029] In one embodiment, step S10 includes:

[0030] S11: Determine the vibration velocity of the hole wall particles of the rock mass in the blasting hole;

[0031] S12: Determine the vibration velocity of the particles at any distance from the blasting hole according to the vibration velocity of the hole wall particles and the propagation velocity of the blasting shock wave in the rock mass;

[0032] S13: Determine the strain rate of the rock mass at this position according to the vibration velocity of the particles.

[0033] In one embodiment, step S11 includes:

[0034] S111: Measure the density ρ of the rock mass in the blasting hole before blasting 0 ;

[0035] S112: Determine the impact pressure P of the blasting on the rock mass in the blasting hole according to the blasting equivalent b ;

[0036] S113: The initial vibration velocity of the hole wall particles where a and b are parameters related to the lithology; a is the propagation velocity of sound waves in the rock mass; b = 1 - 1.5.

[0037] In one embodiment, step S12 includes:

[0038] S121: Measure the distance x between the calculation position and the blasting hole;

[0039] S122: Measure the radius r of the blasting hole b ;

[0040] S123: The particle vibration velocity at the calculated position where α is the stress wave attenuation coefficient.

[0041] In one embodiment, step S13 includes:

[0042] S131: Take the derivative of the particle vibration velocity at the calculated position to obtain the strain rate of the rock mass at this position

[0043] It can be explained that the traditional rock mass strain rate is mainly obtained directly through the experimental method. However, due to the difficulty in measuring the rock mass strain rate near the blasting hole, the results obtained by the experimental method may vary greatly, resulting in inaccurate strain rate results. The tunnel rock mass dynamic mechanics blasting analysis method proposed by the present invention measures the density ρ of the rock mass 0 , and obtains the blasting equivalent to be used in the blasting. Through the calculation software, the blasting equivalent to be used is analyzed to obtain the impact pressure P of the blasting on the rock mass in the blasting hole b , so as to obtain the initial vibration velocity in the blasting hole, and then obtain the particle vibration velocity at the calculated position according to the distance x between the calculated position and the blasting hole. The strain rate & is calculated through the particle vibration velocity, thus overcoming the difficulty of measuring the strain rate near the blasting hole by the traditional experimental method and making the acquisition of the strain rate more accurate.

[0044] In one embodiment, step S20 includes:

[0045] S21: Calculate the dynamic compressive strength of the rock mass according to the strain rate;

[0046] S22: Calculate the dynamic tensile strength of the rock mass according to the strain rate.

[0047] In one embodiment, step S21 includes:

[0048] S211: Measure the static compressive strength σ of the rock mass c ;

[0049] S212: Calculate the dynamic compressive strength [σ of the rock mass according to the compressive dynamic growth factor cd and the strain rate &; where K is the static compressive strength reduction coefficient, taking 0.4.

[0050] In one embodiment, step S22 includes:

[0051] S221: Determine the type of the rock mass;

[0052] S222: Determine the characteristic strain rate & corresponding to each type of the rock mass according to the empirical formula 0 and the dynamic growth coefficient α;

[0053] S223: Measure the static tensile strength σ of each type of the rock mass t ;

[0054] S224: Calculate the dynamic tensile strength [σ of the rock mass according to the tensile dynamic growth factor and the strain rate & td .

[0055] It should be explained and noted that the strain rate in the vicinity of the blasting caused by the explosion of the explosive decays with the increase of the distance, so the dynamic response of the rock mass is also distance-dependent. For the change of the dynamic strength of the rock mass in the vicinity of the blasting, an empirical method can be adopted, using the dynamic growth factor (DIF) as the strength characteristic quantity, which is defined as the ratio of the dynamic strength to the static strength and is used to evaluate the rate dependence of the rock mass material. The dynamic strength of the rock mass can be directly estimated according to the static rock mass strength and the strain rate. The failure of the rock mass in the vicinity of the blasting is mainly divided into the crushed zone formed by compressive failure and the crack zone formed by tensile failure. For the dynamic compressive strength, within the range where the strain rate is higher than 30 s -1 the dynamic growth factor is expressed as For the dynamic tensile strength, the dynamic growth factor is expressed as The characteristic strain rate & of different rock masses 0 is different and can be obtained by referring to the empirical method. Thus, according to the differences between the crushed zone formed by compressive failure and the crack zone formed by tensile failure, the dynamic compressive strength and the dynamic tensile strength can be obtained respectively according to the static compressive strength and the static tensile strength of the rock mass

[0056] In one embodiment, step S30 includes:

[0057] S31: Determine the stress intensity σ at any distance from the blasting hole according to the transmission law of the stress wave i ;

[0058] S32: Calculate the compressive failure range of the rock mass according to the equality of the dynamic compressive strength [σ cd and the stress intensity σ i where B is a parameter that comprehensively reflects the dynamic response characteristics and the stress wave attenuation characteristics of the rock mass and X is the distance from the calculation position to the blasting hole;

[0059]

[0059] S33: According to the dynamic tensile strength [σ tdequal to the stress intensity σ i calculate the tensile failure range of the rock mass

[0060] S34: Combine the compressive failure range R c and the tensile failure range R t to determine the blasting failure range

[0061] In one embodiment, step S31 includes:

[0062] S311: The radial stress at the position x from the blasting hole

[0063] S312: The tangential stress σ at the position x from the blasting hole θ =-bσ ρ ; where b = v d / (1 - v d ); v d is the dynamic Poisson's ratio of the rock mass

[0064] S313: The stress intensity at any distance from the blasting hole

[0065]

[0066] It can be explained that by transforming the propagation of stress waves in the rock mass into a plane strain problem, at the moment of rock mass failure, the stress intensity at any point in the rock mass under the triaxial stress state is equal to the dynamic structural strength when the blasting occurs and causes failure. Therefore, according to the different dynamic structural strengths of the crushed zone formed by compressive failure and the crack zone formed by tensile failure, the compressive failure range R c of the crushed zone and the tensile failure range R t of the crack zone are calculated respectively. Combine R c and R t to obtain the entire blasting failure range, making the analysis result of the blasting failure range of the rock mass closer to the actual result, effectively improving the accuracy of the blasting analysis result, and thus improving the safety during the tunnel blasting construction process

[0067] The above is only an exemplary embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structural transformation made under the technical concept of the present invention by using the content of the specification and drawings of the present invention, or directly / indirectly applied in other related technical fields, is included in the patent protection scope of the present invention

Claims

1. A tunnel rock mass dynamic mechanical blasting analysis method, characterized in that: Includes steps: Obtain the strain rate of the rock mass near the blasting hole; Calculating the dynamic structural strength of the rock mass during the blasting process according to the strain rate; The blasting damage range of the rock mass is calculated according to the dynamic structural strength.

2. The tunnel rock mass dynamic mechanical blasting analysis method according to claim 1, characterized in that: The step of obtaining the strain rate of the rock mass near the blast hole comprises: Determining the vibration velocity of the hole wall particles of the rock mass in the blast hole; Determine the vibration velocity of the particle at any distance from the blast hole according to the vibration velocity of the particle on the hole wall and the propagation velocity of the blasting shock wave in the rock mass; The strain rate of the rock mass at the position is determined according to the particle vibration velocity.

3. The tunnel rock mass dynamic mechanical blasting analysis method according to claim 2, characterized in that: The step of determining the vibration velocity of the hole wall particles of the rock mass in the blast hole comprises: Measuring the density ρ0 of the rock mass in the blasting hole before blasting; Determine the impact pressure P of the blasting on the rock mass in the blasting hole according to the blasting equivalent b ; The initial particle vibration velocity of the hole wall Among them, a and b are parameters related to rock properties; a is the propagation speed of sound waves in the rock mass; b = 1-1.

5.

4. The tunnel rock mass dynamic mechanical blasting analysis method according to claim 3, characterized in that: The step of determining the vibration velocity of a particle at any distance from the blast hole according to the vibration velocity of the particle on the hole wall and the propagation velocity of the blast shock wave in the rock mass comprises: Measure and calculate the distance x between the position and the blast hole; Measure the radius r of the blast hole b ; The particle vibration velocity at the calculated position Among them, α is the stress wave Attenuation coefficient.

5. The tunnel rock mass dynamic mechanical blasting analysis method according to claim 4, characterized in that: The step of determining the strain rate of the rock mass at the position according to the particle vibration velocity comprises: The particle vibration velocity at the calculated position is derived to obtain the strain rate of the rock mass at that position.

6. The tunnel rock mass dynamic mechanical blasting analysis method according to claim 5, characterized in that: The step of calculating the dynamic structural strength of the rock mass during the blasting process according to the strain rate comprises: Calculating the dynamic compressive strength of the rock mass according to the strain rate; The dynamic tensile strength of the rock mass is calculated according to the strain rate.

7. The tunnel rock mass dynamic mechanical blasting analysis method according to claim 6, characterized in that: The step of calculating the dynamic compressive strength of the rock mass according to the strain rate comprises: Measure the static compressive strength σ of the rock mass c ; According to the stress resistance growth factor and the strain rate & calculate the dynamic compressive strength of the rock mass [σ cd ]; where K is the static compressive strength reduction coefficient, which is taken as 0.

4.

8. The tunnel rock mass dynamic mechanical blasting analysis method according to claim 7, characterized in that: The step of calculating the dynamic tensile strength of the rock mass according to the strain rate comprises: determining the type of the rock mass; Determine the characteristic strain rate &0 and dynamic growth coefficient α corresponding to each type of rock mass according to the empirical formula; Measure the static tensile strength σ of each type of rock mass t ; According to the tensile strength growth factor and the strain rate & calculate the dynamic tensile strength of the rock mass [σ td ].

9. The tunnel rock mass dynamic mechanical blasting analysis method according to claim 8, characterized in that: The step of calculating the blasting damage range of the rock mass according to the dynamic structural strength comprises: According to the transmission law of stress wave, the stress intensity σ at any distance from the blast hole is determined i ; According to the dynamic compressive strength [σ cd ] and the stress intensity σ i Equal, calculate the compressive failure range of the rock mass Among them, B is a parameter that combines the dynamic response characteristics of rock mass and the attenuation characteristics of stress waves. X is the distance from the calculated position to the blast hole; According to the dynamic tensile strength [σ td ] and the stress intensity σ i Equal, calculate the tensile failure range of the rock mass Combined with the pressure damage range R c and the tensile failure range R t , determine the scope of blasting damage.

10. The tunnel rock mass dynamic mechanical blasting analysis method according to claim 9, characterized in that: According to the transmission law of stress wave, the stress intensity σ at any distance from the blast hole is determined. i The steps include: Radial stress at position x from the blast hole The tangential stress σ at the position x from the blast hole θ =-bσ ρ ;in, b=v d / (1-v d );v d is the dynamic Poisson's ratio of the rock mass; Stress intensity at any distance from the blast hole

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