An asymmetric uncoupled tunnel smooth blasting method

Abstract

The application discloses a kind of asymmetric decoupling tunnel smooth blasting method, comprising: obtaining the surrounding rock classification data of target area and initial ground stress distribution and optimizing low-damage test blasting scheme;Based on the low-damage test blasting scheme, drilling operation is carried out, and asymmetric decoupling fine charging casing device is assembled by selecting specific pre-charging site and assembling peripheral hole pre-charging casing device;The surrounding hole is filled by the peripheral hole pre-charging casing device, and the remaining blast hole is filled by using continuous charging method, and is blocked after filling is completed;Build initiation network, ventilate after initiation and check blasting effect, and iteratively optimize test blasting scheme according to damage determination result.The application can accurately control the working direction and range of energy of explosives in the surrounding hole during blasting, thereby reducing the disturbance of blasting effect on surrounding rock, reducing the damage degree of surrounding rock blasting, ensuring construction safety, reducing the number of overbreak and underbreak, and greatly improving construction efficiency.

Description

Technical Field

[0001] This invention belongs to the field of tunnel drilling and blasting construction technology, and particularly relates to an asymmetric, uncoupled tunnel smooth blasting method. Background Technology

[0002] The rock-breaking mechanism of smooth blasting is a highly complex issue and is still under investigation. Although the theory is not yet fully mature, there is a consensus on qualitative analysis. It is generally believed that the detonation of explosives produces two effects on the rock mass: one is the work done by the expansion of the explosive gases. For example... Figure 1 As shown, smooth blasting involves the simultaneous detonation of all boreholes. The shock waves from each borehole propagate radially in all directions. When the impacts from adjacent boreholes meet, stress waves are superimposed, generating tangential tension. The maximum tension occurs at the midpoint of the line connecting the centers of adjacent boreholes. When the ultimate tensile strength of the rock mass is less than this tension, the rock mass is fractured, forming a crack along the line connecting the centers of the boreholes. Subsequently, the expansion of the explosion products causes the crack to further extend, forming a smooth blast surface.

[0003] The main advantages of smooth blasting are: by correctly selecting blasting parameters and reasonable construction methods, and by performing micro-differential blasting in sections and segments, the blasted contour line meets the design requirements, the free face is flat and regular, and the integrity of the tunnel surrounding rock as a whole is ensured, thus achieving the goal of safe and rapid construction.

[0004] Current smooth blasting technology, when applied to actual tunnel blasting construction, often encounters problems such as over-excavation and under-excavation, excessive damage to the surrounding rock, and unevenness of the rock wall after blasting. Furthermore, smooth blasting charges typically employ decoupled charge structures. In decoupled charge structures, due to the gap between the charge cartridge and the borehole, the charge cartridge contacts the bottom wall of the borehole under gravity, resulting in an eccentric decoupled charge structure. Since the explosive energy released by bottom-eccentric decoupled charge blasting is mainly concentrated at the bottom edge of the borehole, it easily leads to irregular contours in the blasted surrounding holes.

[0005] In view of this, the present invention proposes an asymmetric, uncoupled tunnel smooth blasting method based on traditional blasting methods. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes an asymmetric, uncoupled tunnel smooth-surface blasting method to solve the problems existing in the prior art.

[0007] To achieve the above objectives, the present invention provides an asymmetric, uncoupled tunnel smooth-surface blasting method, comprising:

[0008] Obtain surrounding rock classification data and initial geostress distribution in the target area, and optimize the low-damage test blasting scheme based on the surrounding rock classification data and initial geostress distribution;

[0009] Drilling operations are carried out based on the aforementioned low-damage test blasting scheme, including differentiated drilling of slotted holes, auxiliary holes, and peripheral holes.

[0010] A specific pre-loading site is selected and an asymmetric, uncoupled fine-precision loading sleeve device is assembled. Based on the asymmetric, uncoupled fine-precision loading sleeve device, a peripheral hole pre-loading sleeve device is assembled. The asymmetric, uncoupled fine-precision loading sleeve device includes an outer sleeve, an inner sleeve, an eccentric adjustment block, and a gasket structure of equal thickness.

[0011] The peripheral holes are filled using a pre-charge sleeve device, while the remaining holes are filled using a continuous charging method. After filling, the holes are plugged. An initiation network is constructed by connecting the non-electric detonator lead wire cluster in parallel to the detonating cord and then connecting it to the detonating detonator.

[0012] After detonation, ventilation is provided and the blasting effect is checked. The test blasting plan is iteratively optimized based on the damage assessment results to complete the current blasting cycle.

[0013] Optionally, the formula for determining the initial geostress distribution is as follows:

[0014]

[0015] In the formula, σ r and σ θ These represent the radial and tangential stresses of the infinitesimal element, respectively; σ h and σ p These represent the horizontal and vertical ground stresses, σ. h =λ p σ p ;σ a R represents the stress along the borehole direction. h σ is the borehole radius; r is the distance from the borehole wall and nearby infinitesimal elements to the borehole center; h and σ p These represent the horizontal and vertical ground stresses, respectively; θ is the angle between the infinitesimal element and the horizontal direction; λ p λ is the lateral pressure coefficient. p =μ / (1-μ), where μ is the static Poisson's ratio, σ r0 For radial stress, σ q0 For tangential stress, τ rθ This is shear stress.

[0016] Optionally, the parameters of the low-damage test detonation scheme include the spacing between peripheral holes, the charge amount per peripheral hole, the differential between different sections of boreholes, the decoupling coefficient of peripheral holes, the decoupling coefficient of auxiliary holes, the charge amount of auxiliary holes, the diameter of the explosive cartridge in the peripheral holes, the borehole diameter of the peripheral holes, the charge concentration of the peripheral holes, the offset distance of the explosive cartridge in the peripheral holes, and the minimum resistance line.

[0017] Optionally, the decoupling coefficient of the peripheral holes and the offset distance of the explosive charge in the peripheral holes are optimized based on the asymmetric decoupled blast hole wall pressure distribution function; the asymmetric decoupled blast hole wall pressure distribution function is as follows:

[0018]

[0019] Where, η fd Where ρ is the decoupling coefficient, ρ0 is the explosive density, and D is the decoupling coefficient. v For the detonation velocity of the explosive, r c and r b These are the radius of the propellant cartridge and the radius of the borehole, respectively, σ rf and σ θf λ represents the peak pressure exerted on the borehole wall surrounding rock under radial and tangential stresses, respectively. d The dynamic lateral pressure coefficient is given by d, where d is the offset distance and P is the dynamic lateral pressure coefficient. d1 σ is the shock wave pressure per unit area of ​​the rock wall in the borehole. cd and σ td Let γ be the uniaxial dynamic compressive strength and dynamic tensile strength of the rock, and γ be the adiabatic index of the explosive. The calculation formula is: That is, the ratio of isobaric specific heat capacity to isovolumetric specific heat capacity, l e Here, B is the axial force coefficient of the charge, and B is the dynamic stress coupling coefficient, derived from the rock dynamic Poisson's ratio μ. d The calculation yields the following formula:

[0020] Optionally, the charge amount per hole in the peripheral holes and the differential pressure between different sections of the borehole are determined based on the symmetrical blasting load distribution and the asymmetrical uncoupled blasting hole wall pressure distribution function; the symmetrical blasting load distribution is as follows:

[0021]

[0022] Where, σ r1 and σ θ1 These represent the radial and tangential stresses, respectively, experienced by a spatial infinitesimal element under dynamic load. d1 σ is the shock wave pressure per unit area of ​​the rock wall in the borehole. cd and σ td Let η represent the uniaxial dynamic compressive strength and dynamic tensile strength of the rock, and η be the radial decoupling coefficient, η = r b / r c;

[0023] Optionally, based on the initial ground stress distribution formula and the symmetrical blasting load distribution, the stress distribution function of a point in the rock mass under coupled action is obtained. Based on the stress distribution function of a point in the rock mass under coupled action, the distribution characteristics of tangential stress and radial stress at any point in the surrounding rock of the borehole wall under the coupled action of initial ground stress and asymmetric blasting load are obtained. Combined with the VON-MISES failure criterion, it is determined whether the surrounding rock unit has entered the failure state. At the same time, the blasting disturbance damage variable is introduced to obtain the surrounding rock damage degree judgment formula. Based on the stress distribution function of a point in the rock mass under coupled action and the surrounding rock damage degree judgment formula, the spacing between peripheral holes, the charge concentration of peripheral holes, the decoupling coefficient of auxiliary holes, and the charge amount of auxiliary holes are determined.

[0024] Optionally, the diameter of the explosive cartridges in the peripheral holes, the borehole diameter in the peripheral holes, and the charge concentration in the peripheral holes can be optimized based on the pressure distribution function of the asymmetric uncoupled blasting hole wall, the stress distribution function of a point in the rock mass under coupling, and the formula for judging the degree of damage to the surrounding rock.

[0025] Optionally, the degree of damage to the surrounding rock after blasting is determined by the following formula:

[0026]

[0027] Where, σ ir σ iθ For the radial and tangential stresses of the infinitesimal element, σ cd and σ td The uniaxial dynamic compressive strength and dynamic tensile strength of the rock; For radial and tangential effective stresses; D1, D2...D n For each cycle, the perturbation damage is defined as 0 ≤ D1, D2...D n ≤1.

[0028] Optionally, the process of assembling the peripheral hole pre-charge sleeve device includes: binding the asymmetric uncoupled fine charge sleeve device to a PVC pipe, and connecting the asymmetric uncoupled fine charge sleeve devices of each interval charge section with a detonating cord to complete the assembly of the peripheral hole pre-charge sleeve device.

[0029] Optionally, each charging orifice can be plugged manually using water-based gun mud as the plugging material.

[0030] Compared with the prior art, the present invention has the following advantages and technical effects:

[0031] This invention can precisely control the direction and range of energy exerted during the blasting of explosives in the surrounding holes, thereby reducing the disturbance of the blasting effect on the surrounding rock, reducing the degree of damage to the surrounding rock, ensuring construction safety, reducing the frequency of over-excavation and under-excavation, and greatly improving construction efficiency.

[0032] This invention derives the distribution function of asymmetric uncoupled blasting loads. Considering the disturbance effect of multiple cyclic blasts on the surrounding rock and the initial ground stress, it establishes tensile and compressive failure criteria for rock under the combined action of asymmetric uncoupled blasting loads and initial ground stress. By establishing the asymmetric load distribution function, the directional control of the explosive offset distance on the borehole wall stress is quantified, solving the problem of uneven energy distribution caused by traditional symmetrical charges. Simultaneously, by combining disturbance damage variables and failure criteria, the accumulation mechanism and strength threshold of surrounding rock damage under cyclic blasting are clarified, providing a theoretical basis for precise control of charge parameters in optimization schemes. Attached Figure Description

[0033] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0034] Figure 1 This is a schematic diagram of the various boreholes in the background art of this invention;

[0035] Figure 2 This is a flowchart illustrating the asymmetric, uncoupled blasting construction process according to an embodiment of the present invention.

[0036] Figure 3 This is a diagram showing the initial geostress distribution of the surrounding rock of the borehole in an embodiment of the present invention.

[0037] Figure 4 This is a schematic diagram of the blasting load and boundary conditions of the surrounding rock of the borehole wall in an embodiment of the present invention;

[0038] Figure 5 This is a schematic diagram of the coupling between concentric blasting load and ground stress in an embodiment of the present invention;

[0039] Figure 6 This is a schematic diagram of the asymmetric uncoupled charge structure according to an embodiment of the present invention;

[0040] Figure 7 The present invention provides a novel pre-filled drug sleeve device, (a) is an end view of the novel pre-filled drug sleeve device, (b) is a plan view of the PVC inner sleeve, and (c) is a plan view of the PVC inner sleeve.

[0041] Figure 8 This is a schematic diagram of the charge structure when the offset distance is d according to an embodiment of the present invention;

[0042] Figure 9This is a schematic diagram of the coupling between asymmetric blasting load and ground stress in an embodiment of the present invention;

[0043] Figure 10 This is a comparison chart of the differences between the Lagrange, Euler, and ALE algorithms in embodiments of the present invention;

[0044] Attachment markings: 1. PVC outer sleeve; 2. PVC inner sleeve; 3. Eccentric adjustment block positioning mark line; 4. Eccentric loading direction mark line; 5. Eccentric adjustment block; Detailed Implementation

[0045] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0046] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0047] Example 1

[0048] In view of the problems of non-standard operation, low charging efficiency, and inability to accurately determine the charging structure in on-site charging blasting, as well as the problems of over-excavation and under-excavation, surrounding rock damage, large blocks, and blasting disturbance in existing tunnel smooth blasting methods, this embodiment provides an asymmetric and decoupled tunnel smooth blasting method based on the principle of low-damage blasting, including:

[0049] (1) Asymmetric decoupled blasting construction process

[0050] The construction process includes: ① Using various detection methods to obtain on-site geological conditions and surrounding rock classification, clarifying the proportion and occurrence structure of each surrounding rock section, and optimizing the test blasting plan; ② Drilling operations for slotting holes, auxiliary holes, and peripheral holes according to the optimized test blasting plan. The diameter of the peripheral holes, auxiliary holes, and slotting holes is 42mm. The slotting holes adopt a wedge-shaped hole method, the auxiliary holes adopt a straight hole method, and the peripheral holes adopt a drilling method with a fixed external insertion angle; ③ Selecting an area as a specific pre-loading site according to the site layout of the inlet and outlet. According to the explosive offset distance of the peripheral holes specified in the blasting plan, adjust the PVC outer sleeve 1, PVC inner sleeve 2, eccentric adjustment block 5, and equal thickness gasket structure in the asymmetric uncoupled fine charging sleeve device. After adjusting the asymmetric sleeve device, the explosives of the peripheral holes are loaded into the inner sleeve of the sleeve device. According to the setting of the peripheral hole interval charging structure, the assembled peripheral hole pre-charged sleeves are tied to PVC pipes, and the asymmetrical sleeves of each interval charging section of the peripheral holes are connected together with detonating cords. After the connection is completed, the fabricated peripheral hole pre-charged device, explosives, and detonators are transported to the tunnel excavation trolley area for loading, while the remaining blast holes are loaded in the form of continuous charging on the tunnel face excavation trolley; ④ After the explosives in the cut holes, auxiliary holes, peripheral holes, and bottom plate holes are loaded, the openings of each charging hole are plugged manually using water cannons as the plugging material. ⑤ After the mud filling is completed, the end leads of the non-electric detonators that have been connected in each hole are tied together in a cluster to a detonating cord using the external detonation network connection method. Then, the detonating cord is tied together with a detonating detonator using black tape. At this point, the connection of the detonation network is completed. ⑥ After the detonation network is connected, the drilling rig is moved to a safe area using an excavator, and the detonation network of the section is checked again to see if any workers have not evacuated. After the inspection is completed, the blasting team leader issues the blasting order, and the detonation begins on site; ⑦ After the detonation, the ventilation fan is started. After 15 minutes of ventilation, some blasting personnel can enter the blasting site to inspect and handle misfires and loose rocks; ⑧ After the site inspection is completed, the warning is lifted, and the current blasting cycle ends; ⑨ Preparations for the next cycle begin, specifically: muck removal - erecting steel arches - laying steel mesh - initial concrete spraying using a wet spraying process. Detailed process flow is as follows: Figure 2 As shown.

[0051] The main parameters for optimizing the blasting scheme include: offset distance of explosive cartridges in peripheral holes, decoupling coefficient of peripheral holes, decoupling coefficient of auxiliary holes, charge concentration in peripheral holes, charge amount per peripheral hole, charge amount in auxiliary holes, spacing between peripheral holes, and minimum resistance line. The main optimization objectives are: ① to control the direction of work of explosive energy in peripheral holes, so that the explosive energy of the surrounding rock to be preserved is weaker than that of the surrounding rock to be blasted; ② to concentrate most of the energy in the surrounding rock to be blasted, which helps to reduce the damage to the surrounding rock to be preserved, the over-excavation and under-excavation range, concrete consumption, and blasting vibration effects, while maintaining the stability of the surrounding rock.

[0052] Expected blasting effects: ① The outline of the tunnel face after blasting is regular and the undulation is uniform; ② The blasting vibration effect is effectively controlled; ③ The bearing capacity and stability of the surrounding rock after blasting are maintained to the maximum extent; ④ Over-excavation and under-excavation meet the allowable over-excavation limits for the arch and sidewalls in the national standard "Technical Specifications for Highway Tunnel Construction"; ⑤ The half-hole trace rate is not less than 50%; ⑥ The utilization rate of explosive energy is above 90%.

[0053] (2) Mechanism of Asymmetric Uncoupled Smooth Tunnel Blasting and Surrounding Rock Damage Control

[0054] 1) Initial geostress distribution in the borehole wall surrounding rock

[0055] Assuming the rock mass is homogeneous, and since the size of the circular borehole is much smaller than its axial length, the drilling problem can be treated as a plane strain model. The stress redistribution in the surrounding rock near the circular borehole is as follows: Figure 3 As shown. After the borehole is formed, the horizontal and vertical stress distribution of the surrounding rock of the borehole wall can be calculated according to equation (1).

[0056]

[0057] In the formula: σ r and σ θ The stress is divided into radial and tangential stresses of the infinitesimal element; σ h and σ p These represent the horizontal and vertical ground stresses, σ. h =λ p σ p ;σ a R represents the stress along the borehole direction. h σ is the borehole radius; r is the distance from the borehole wall and nearby infinitesimal elements to the borehole center; h and σ p These represent the horizontal and vertical ground stresses, respectively; θ is the angle between the infinitesimal element and the horizontal direction; λ p λ is the lateral pressure coefficient. p =μ / (1-μ), where μ is the static Poisson's ratio.

[0058] 2) Symmetrical blasting load distribution

[0059] After the explosives detonate in the borehole, a rapid and violent chemical reaction occurs in the localized explosives. During this reaction, a large amount of high-temperature, high-pressure, high-speed gas flow is released, accompanied by a continuous and rapid generation of thermal energy. When the expansive, high-energy, high-speed gas flow strongly compresses the unreacted explosives in adjacent layers, it triggers an explosive shock wave. Due to the high pressure and supersonic characteristics of the shock wave itself, the properties and parameters of the explosives undergo a step-like change after the pressure wave front passes through, accompanied by the ongoing chemical reaction. Simultaneously, the propagation of the explosive shock wave and the expansion of the explosive gases both alter the stress state of the surrounding rock in the borehole wall, causing it to break down and fail. In particular, the explosive shock wave strongly compresses the surrounding rock in the borehole wall, leading to shear failure and the formation of a crushing zone. Subsequently, under strong attenuation, the shock wave transforms into a compressive stress wave. Since the stress wave intensity is lower than the compressive strength of the surrounding rock, the surrounding rock does not undergo compressive failure. However, while experiencing radial compression, the surrounding rock is also subjected to tangential tensile stress. When the tensile strength of the surrounding rock is less than the tangential tensile stress, tensile failure occurs, forming initial fractures. After this, the tensile-compression effect of the stress wave only causes elastic deformation of the surrounding rock, without leading to rock failure. Because the explosive gas lags behind the stress wave, after the stress wave attenuates, the expansion of the explosive gas begins to promote the expansion of the initial fractures and induce the formation of secondary fractures. As the initial and secondary fractures continue to expand, the "gas wedge" effect of the explosive gas becomes increasingly pronounced, and adjacent fractures begin to connect and penetrate, ultimately leading to a dense network of fractures in the surrounding rock outside the fractured zone. In summary, the fracturing and crack propagation of the surrounding rock in the borehole are both the result of the combined effects of the blast wave and the explosive gas. Therefore, for single-hole concentric uncoupled blasting, the surrounding rock near the blast source is subjected to the compressive and shear effects of the blast stress wave, and the peak load expression is shown in equation (2):

[0060] P d1 =n s P s (2)

[0061] In the formula: P d1 n is the shock wave pressure per unit area of ​​the rock wall in the borehole; s The pressure amplification factor is the pressure amplification factor when detonation products compress and collide with the surrounding rock, and is generally taken as 8 to 10; P s The peak pressure under the action of explosive gas expansion is expressed as shown in equation (3):

[0062]

[0063] In the formula: ρ0 is the density of the explosive; D v For the detonation velocity of the explosive; γ s The thermal expansion index is the thermal expansion index. c p and c v These are the specific heat capacity at constant pressure and the specific heat capacity at constant volume, respectively; r c and r b These are the radius of the propellant cartridge and the radius of the borehole, respectively.

[0064] As the blast shock wave propagates outwards, its peak intensity decreases exponentially with increasing distance. Furthermore, after fracturing the surrounding rock in the vicinity, the shock wave gradually attenuates into an elasto-plastic stress wave. During this process, the stress state of a micro-element within the rock mass is as follows: Figure 4 As shown, its radial and tangential stress expressions are given by equation (4):

[0065]

[0066] In the formula, σ r1 and σ θ1 These represent the radial and tangential stresses experienced by a spatial infinitesimal element under dynamic load; σ θ1 And β are the wave attenuation coefficients, α = 2 + μ d / (1-μ d ), β=2-μ d / (1-μ d ), μ d λ represents the dynamic Poisson's ratio, with positive and negative signs corresponding to the shock wave region and the stress wave region, respectively. d The dynamic lateral pressure coefficient is 0.8λ; R0 and R1 are the ranges of the crushing zone and the fracture zone, respectively, and their specific expressions are shown in equation (5):

[0067]

[0068] In the formula, the radial decoupling coefficient η = r b / r c ;l e σ is the axial coefficient of the propellant charge; cd and σ td These are the uniaxial dynamic compressive strength and uniaxial dynamic tensile strength, respectively; σ R This represents the radial stress at the interface between the fractured zone and the fissure zone. b = μ d / (1-μ d ).

[0069] Substituting equation (5) into equation (4), we obtain the radial and tangential stresses of the surrounding rock in different action zones under explosive loading, as shown in equation (6):

[0070]

[0071] For the rock mass to be excavated, every point within it is constantly subjected to in-situ stress caused by gravity. After excavation, the in-situ stress redistributes within the rock mass, and the stress condition at a point in the surrounding rock of the borehole wall then conforms to the aforementioned in-situ stress occurrence conditions. Subsequently, under the action of blasting load, the initial stress state in the surrounding rock is broken, and the stress state at a point in the surrounding rock is released. From the above description, it can be seen that in the actual tunnel blasting excavation process, the surrounding rock is subjected to the dynamic action of blasting load on top of the initial in-situ stress, such as... Figure 5 As shown. Therefore, by coupling equations (1) and (6) together, we obtain the stress distribution function of a point in the rock mass under the coupling effect, as shown in equation (7).

[0072]

[0073] 3) Asymmetric uncoupled blast hole wall pressure distribution function

[0074] The above describes the borehole wall pressure distribution characteristics of the fractured and fissured rock zones under concentric uncoupled charge blasting. However, most blasting in actual engineering is asymmetric uncoupled blasting. So, how should the stress distribution of the borehole wall rock under asymmetric uncoupled action be determined? First, it must be clear that both concentric and asymmetric uncoupled blasting require defining an uncoupling coefficient. The difference in pressure distribution functions between concentric and asymmetric uncoupled blasting lies in this uncoupling coefficient. The uncoupling coefficient under concentric uncoupled blasting is a constant value, while the uncoupling coefficient under asymmetric uncoupled blasting is a dynamic parameter, not a constant value, and varies with the borehole wall position coordinates, such as... Figure 6 As shown. Therefore, based on the concentric uncoupled blasting pressure distribution function as the basic blasting function, and according to the charge characteristics of asymmetric uncoupled blasting, the uncoupling coefficient of concentric uncoupled blasting is modified, thereby obtaining the pressure distribution function under asymmetric uncoupled charges.

[0075] With the borehole center O as the origin and point A as the explosive center, the space between the explosive and the borehole wall is air. Arbitrarily select a point C on the borehole wall as the analysis point. Let θ be the angle between the line connecting point C and point O and the vertical direction of the borehole. Then, the decoupling coefficient η at this point is... f The expression is shown in Equation 8:

[0076] η f =r eu / r c (8)

[0077] In the formula, r eu Let r be the distance from point A, the center of the explosive, to point C. eu It can be expressed by equation (9):

[0078]

[0079] Substituting equation (9) into equation (8), we obtain the decoupling coefficient of any point on the borehole wall rock under asymmetric decoupled blasting, as shown in equation (10):

[0080]

[0081] According to equations (6) and (10), the peak pressure on the surrounding rock of the borehole wall under asymmetric uncoupled blasting can be obtained, as shown in equation (11):

[0082]

[0083] Based on the design requirement of "how to more rationally utilize the uneven load caused by the existing eccentric charge structure," this invention designs a novel pre-charge sleeve device, the end face view and inner and outer sleeve plan views of which are shown below. Figure 7 As shown in (a), (b), and (c) of the figure, the eccentric adjustment block positioning mark line 3 and the eccentric charge direction mark line 4 are illustrated. This device can effectively improve the blasting effect on site and reduce blasting construction costs. At the same time, the pre-charged casing device can significantly improve the on-site charging efficiency and is easy to operate, requiring only the explosive to be pre-installed outside the hole. It can effectively achieve the goal of controlling asymmetric blasting load and energy.

[0084] Therefore, according to equation (11), considering the influence of the asymmetric offset distance, the improved orifice wall pressure distribution function can be obtained. Figure 8 As shown, d is the offset distance of the explosive center, then the decoupling coefficient η at point C is... fd It can be defined according to equation (12).

[0085]

[0086] 4) Damage mechanism of surrounding rock in asymmetric uncoupled blasting

[0087] In summary, for any infinitesimal element in the surrounding rock of an actual blast hole, it is simultaneously subjected to asymmetric blasting loads and in-situ stresses, such as... Figure 9 As shown, by improving equation (7), the distribution characteristics of tangential and radial stress at any point in the borehole wall surrounding rock under the coupling action of initial ground stress and asymmetric blasting load can be obtained, as shown in equation (13).

[0088]

[0089] In the formula: d eu The distance between any infinitesimal element in the rock mass and the borehole wall is given; all other parameters are the same as those mentioned above.

[0090] According to equation (13), the VON-MISES failure criterion is used to determine whether the surrounding rock unit has entered the failure state. Then, the tensile failure and compressive failure of any micro-element in the surrounding rock satisfy the inequality (14):

[0091]

[0092] In the formula σ ir σ iθ For the radial and tangential stresses of the infinitesimal element; σ cd and σ td These represent the uniaxial dynamic compressive strength and dynamic tensile strength of the rock.

[0093] Considering the repeated disturbance to the surrounding rock caused by actual tunnel cyclic blasting, the blasting disturbance damage variable D is introduced. i If i = 1, 2...n, then equation (14) can be written as equation (15):

[0094]

[0095] In the formula For radial and tangential effective stresses; D1, D2...D n For each cycle, the perturbation damage is defined as 0 ≤ D1, D2...D n ≤1;

[0096] Substituting equation (13) into equation (15), we obtain the tensile and compressive failure criteria of a point in the surrounding rock under the asymmetric uncoupled blasting cycle number, as shown in equation (16):

[0097]

[0098] 5) Gas-solid two-phase coupling and equation of state

[0099] The explosion of explosives produces explosive gases. The expansion and compression of these gases cause the surrounding rock in the borehole to fracture. In this rock-breaking process, the fluid-solid coupling between the explosive gases and the surrounding rock is the fundamental mechanism for rock fracturing.

[0100] ① Arbitrary Larange Algorithm

[0101] The solid-state algorithm adopts the Lagrangian form, that is, it selects the material coordinates and time t as independent coordinates, and observes the deformation of the object through the moving particles. The mass, momentum, and energy conservation equations of solid materials described by the Lagrangian method are shown in equation (17):

[0102]

[0103] Where: J is the volume ratio of the solid element before and after deformation; ρ is the mass density of the current state; ρ0 is the mass density of the initial state; c i e represents the force per unit mass of the material. int This represents the internal energy per unit mass of a material.

[0104] The equilibrium equations, geometric equations, and physical equations of solid materials under elastic dynamics are shown in equation (18):

[0105]

[0106] ②Air Algorithm

[0107] The air algorithm is based on the Euler algorithm, and the corresponding viscous flow process is shown in equation (19):

[0108]

[0109] ③ Coupling between solids and air

[0110] By coupling solids and air using the ALE algorithm, computational mesh points can move arbitrarily within the spatial mesh, and changes in material boundaries can be simulated more effectively. Furthermore, deformations in the material mesh can be propagated back to the spatial mesh via mass transport, such as... Figure 10 As shown.

[0111] Figure 10 In the ALE algorithm space, there are Lagrangian and Eulerian meshes. Since the velocities of the two meshes differ, we define the material velocity and the fluid mesh velocity v separately. l and u e And introduce a relative velocity w, where w = v l +u e The material derivatives of each material's physical quantities are shown in equation (20):

[0112]

[0113] Based on equation (20), the control equation for ALE is derived from the Euler control equation:

[0114] The continuity equation is shown in equation (21):

[0115] ρ t[x] +ρ i w i +ρv i,i =0 (21)

[0116] The momentum conservation equation is shown in equation (22):

[0117] ρv i,t[x] +ρvi,j w i -σ ij,j -ρc i =0 (22)

[0118] The energy conservation equation is shown in equation (23):

[0119] ρE t[x] +ρw i E j -σ ij v ij -ρc i v i =0 (23)

[0120] Based on the elucidation of the fundamental governing equations of ALE, fluid-structure interaction simulation is achieved by setting up different PART groups. Furthermore, fluid-structure interaction is realized between different PARTs by defining relevant keywords. The main keywords are:

[0121] 1) Fluid and solid element algorithms

[0122] *SECTION_SOLID, *SECTION_SOLID_ALE

[0123] 2) Definition of multi-substance group

[0124] *ALE_MULTI_MATERIAL_GROUP

[0125] 3) Coupling Algorithm

[0126] *CONSTRAINED_LAGRANGE_IN_SOLID

[0127] 4) ALE algorithm control

[0128] *CONTROL_ALE, *ALE_SMOOTHING

[0129] In the blasting model, only the explosive and air require equations of state to describe the relationship between material pressure and volume. The corresponding equations of state for the explosive and air are as follows:

[0130] a. Equations for explosive materials

[0131] To accurately reflect the actual explosive detonation process, this invention selects a high-explosive material model to describe the combustion and damage behavior of explosives. For high-explosive materials, the combustion fraction F is first defined, and its product with the explosive's equation of state reflects the explosive energy released during the chemical reaction. Then, the explosive pressure transmitted into the rock mass at a certain moment during the explosive detonation process is shown in equation (24):

[0132] p burn=FP eos (V,E z ) (twenty four)

[0133] In the formula, F is the combustion fraction of the explosive, 0 <F≤1;P eos For the equation of state of explosives, there are three types in LS-DYNA: JWL, propellant combustion equation and JWLB equation. Since JWLB involves more parameters, the JWLB equation is chosen as the main equation of state, as shown in equation (25):

[0134]

[0135] In the formula A J B J R1, R2, and w are the parameters of the explosive; V r For specific volume, V r =V / V o V is the current volume of the explosive. o E represents the initial explosive volume. z It is the thermodynamic energy per unit volume of explosive.

[0136] For the explosive mass fraction F, there are two forms, and the maximum value is generally selected, as shown in equation (26):

[0137] F = max(F1, F2) (26)

[0138]

[0139] In the formula t l The time it takes for the center of the explosive to reach the nearest detonation point; A e,max V represents the maximum surface area of ​​the unit cell. CJ The volume is the Chapman-Jouuguet volume. The JWL parameters of the explosive are shown in Table 1.

[0140] Table 1

[0141]

[0142] b. Gas Material Equations

[0143] In actual blasting drilling, decoupled charges are generally used, meaning there is a certain gap between the explosive charge and the borehole wall. The surrounding rock mass also contains a certain amount of pores and fractures. Therefore, in order to correspond to the actual blasting situation, an air model is generally established in the model. In LS-DYNA, the material equations for the air model are generally selected as the empty matter material equation *MAT NULL and the linear polynomial state equation (*EOS LINEAR POLYNOMIAL), as shown in equation (28-30).

[0144]

[0145] P A =C0+C1μ+C2μ 2 +C3μ 3 +C4E k +C5μE k +C6μ 2 E k (29)

[0146]

[0147] In the formula P A E is the expansion pressure generated by the compression of air. k ρ is the internal energy per unit volume, which is taken as 0.25 N / mm² in this invention; ρ / ρ₀ is the relative density ratio, with the initial density of air being 1.293 g / mm³; v / v₀ is the ratio of the current volume to the initial volume; C₀ to C₆ are all constants, and in this invention, C₀ = C₁ = C₂ = C₃ = C₄ = C₅ = C₆ = 0, C₄ = C₅ = γ. a -1, γ a is the adiabatic index. Since a linear polynomial can usually be represented as an ideal gas that conforms to the Gramma quantile, equation (29) can be rewritten as equation (31):

[0148]

[0149] Example 2

[0150] This invention provides an asymmetric, uncoupled tunnel smooth-surface blasting method, comprising:

[0151] Obtain surrounding rock classification data and initial geostress distribution in the target area, and optimize the low-damage test blasting scheme based on the surrounding rock classification data and initial geostress distribution;

[0152] Drilling operations were conducted based on a low-damage test blasting scheme, including differentiated drilling of slotted holes, auxiliary holes, and peripheral holes.

[0153] A specific pre-loading site is selected and an asymmetric uncoupled fine-loading sleeve device is assembled. Based on the asymmetric uncoupled fine-loading sleeve device, a peripheral hole pre-loading sleeve device is assembled. The asymmetric uncoupled fine-loading sleeve device includes an outer sleeve, an inner sleeve, an eccentric adjustment block, and a gasket structure of equal thickness.

[0154] The peripheral holes are filled using a pre-charge sleeve device, while the remaining holes are filled using a continuous charging method. After filling, the holes are plugged. An initiation network is constructed by connecting the non-electric detonator lead wire cluster in parallel to the detonating cord and then connecting it to the detonating detonator.

[0155] After detonation, ventilation is provided and the blasting effect is checked. The test blasting plan is iteratively optimized based on the damage assessment results to complete the current blasting cycle.

[0156] Specifically, the formula for determining the initial geostress distribution is as follows:

[0157]

[0158] In the formula, σ r and σ θ These represent the radial and tangential stresses of the infinitesimal element, respectively; σ h and σ p These represent the horizontal and vertical ground stresses, σ. h =λ p σ p ;σ a R represents the stress along the borehole direction. h σ is the borehole radius; r is the distance from the borehole wall and nearby infinitesimal elements to the borehole center; h and σ p These represent the horizontal and vertical ground stresses, respectively; θ is the angle between the infinitesimal element and the horizontal direction; λ p λ is the lateral pressure coefficient. p =μ / (1-μ), where μ is the static Poisson's ratio, σ r0 For radial stress, σ q0 For tangential stress, τ rθ This is shear stress.

[0159] Specifically, the parameters of the low-damage test blast scheme include the spacing between peripheral holes, the charge amount per peripheral hole, the differential between different sections of boreholes, the decoupling coefficient of peripheral holes, the decoupling coefficient of auxiliary holes, the charge amount of auxiliary holes, the diameter of the explosive cartridge in the peripheral holes, the borehole diameter of the peripheral holes, the charge concentration of the peripheral holes, the offset distance of the explosive cartridge in the peripheral holes, and the minimum resistance line.

[0160] Specifically, the decoupling coefficient of the peripheral holes and the offset distance of the explosive charge in the peripheral holes are optimized based on the asymmetric decoupled blast hole wall pressure distribution function; the asymmetric decoupled blast hole wall pressure distribution function is as follows:

[0161]

[0162] Where, η fd Where ρ is the decoupling coefficient, ρ0 is the explosive density, and D is the decoupling coefficient. v For the detonation velocity of the explosive, r c and r b These are the radius of the propellant cartridge and the radius of the borehole, respectively, σ rf and σ θf λ represents the peak pressure exerted on the borehole wall surrounding rock under radial and tangential stresses, respectively. dThe dynamic lateral pressure coefficient is given by d, where d is the offset distance and P is the dynamic lateral pressure coefficient. d1 σ is the shock wave pressure per unit area of ​​the rock wall in the borehole. cd and σ td Let γ be the uniaxial dynamic compressive strength and dynamic tensile strength of the rock, and γ be the adiabatic index of the explosive. The calculation formula is: That is, the ratio of isobaric specific heat capacity to isovolumetric specific heat capacity, l e Here, B is the axial force coefficient of the charge, and B is the dynamic stress coupling coefficient, derived from the rock dynamic Poisson's ratio μ. d The calculation yields the following formula:

[0163] Specifically, the charge amount per hole in the peripheral holes and the differential pressure between different sections of the borehole are determined based on the symmetrical blasting load distribution and the asymmetrical uncoupled blasting hole wall pressure distribution function; the symmetrical blasting load distribution is as follows:

[0164]

[0165] Where, σ r1 and σ θ1 These represent the radial and tangential stresses, respectively, experienced by a spatial infinitesimal element under dynamic load. d1 σ is the shock wave pressure per unit area of ​​the rock wall in the borehole. cd and σ td Let η represent the uniaxial dynamic compressive strength and dynamic tensile strength of the rock, and η be the radial decoupling coefficient, η = r b / r c ;

[0166] Specifically, based on the initial ground stress distribution formula and the symmetrical blasting load distribution, the stress distribution function of a point in the rock mass under coupled action is obtained. Based on the stress distribution function of a point in the rock mass under coupled action, the distribution characteristics of tangential and radial stresses at any point in the surrounding rock of the borehole wall under the coupled action of initial ground stress and asymmetric blasting load are obtained. Combined with the VON-MISES failure criterion, it is determined whether the surrounding rock unit has entered the failure state. At the same time, the blasting disturbance damage variable is introduced to obtain the formula for judging the degree of damage to the surrounding rock. Based on the stress distribution function of a point in the rock mass under coupled action and the formula for judging the degree of damage to the surrounding rock, the spacing between peripheral holes, the charge concentration of peripheral holes, the decoupling coefficient of auxiliary holes, and the charge amount of auxiliary holes are determined.

[0167] Specifically, the diameter of the explosive cartridges in the peripheral holes, the borehole diameter in the peripheral holes, and the charge concentration in the peripheral holes are optimized based on the pressure distribution function of the asymmetric uncoupled blasting hole wall, the stress distribution function of a point in the rock mass under coupling, and the formula for judging the degree of damage to the surrounding rock.

[0168] Specifically, the degree of damage to the surrounding rock after blasting is determined by the following formula:

[0169]

[0170] Where, σ ir σ iθ For the radial and tangential stresses of the infinitesimal element, σ cd and σ td The uniaxial dynamic compressive strength and dynamic tensile strength of the rock; For radial and tangential effective stresses; D1, D2...D n For each cycle, the perturbation damage is defined as 0 ≤ D1, D2...D n ≤1.

[0171] Specifically, the process of assembling the peripheral hole pre-charge sleeve device includes: binding the asymmetric uncoupled fine charge sleeve device to the PVC pipe, and connecting the asymmetric uncoupled fine charge sleeve devices of each interval charge section with detonating cord to complete the assembly of the peripheral hole pre-charge sleeve device.

[0172] Specifically, each charging orifice is plugged manually using water-based gun mud as the plugging material.

[0173] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An asymmetric, uncoupled tunnel smooth-surface blasting method, characterized in that, Includes the following steps: Obtain surrounding rock classification data and initial geostress distribution in the target area, and optimize the low-damage test blasting scheme based on the surrounding rock classification data and initial geostress distribution; Drilling operations are carried out based on the aforementioned low-damage test blasting scheme, including differentiated drilling of slotted holes, auxiliary holes, and peripheral holes. A pre-loading site is selected and an asymmetric, uncoupled fine-precision loading sleeve device is assembled. Based on the asymmetric, uncoupled fine-precision loading sleeve device, a peripheral hole pre-loading sleeve device is assembled. The asymmetric, uncoupled fine-precision loading sleeve device includes an outer sleeve, an inner sleeve, an eccentric adjustment block, and a gasket structure of equal thickness. The peripheral holes are filled using a pre-charge sleeve device, while the remaining holes are filled using a continuous charging method. After filling, the holes are plugged. An initiation network is constructed by connecting the non-electric detonator lead wire cluster in parallel to the detonating cord and then connecting it to the detonating detonator. After detonation, ventilation is provided and the blasting effect is checked. Based on the damage assessment results, the test blasting plan is iteratively optimized to complete the current blasting cycle. The degree of damage to the surrounding rock after blasting is determined by the following formula: in, and These represent the radial and tangential stresses of the infinitesimal element, respectively. and These are the horizontal and vertical stresses, respectively. ; r is the borehole radius; r is the distance from the borehole wall and the nearby infinitesimal elements to the borehole center. The angle between the infinitesimal element and the horizontal direction; For the density of the explosive, For the detonation velocity of the explosive, and These are the radius of the propellant cartridge and the radius of the borehole, respectively. The dynamic lateral pressure coefficient is given by d, where d is the offset distance. This represents the shock wave pressure per unit area of ​​the rock wall in the borehole. The thermal index of the explosive is calculated using the following formula: That is, the ratio of specific heat capacity at constant pressure to specific heat capacity at constant volume. This is the axial coefficient of the propellant charge. B The dynamic stress coupling coefficient is derived from the rock dynamic Poisson's ratio. The calculation yields the following formula: ; , The radial and tangential stresses of the infinitesimal element are... and The uniaxial dynamic compressive strength and dynamic tensile strength of the rock; , Effective stresses are radial and tangential; , ... For the disturbance damage corresponding to each cycle, , ... ; This represents the radial stress at the interface between the fractured zone and the fissure zone.

2. The asymmetric, uncoupled tunnel smooth blasting method according to claim 1, characterized in that, The parameters of the low-damage test detonation scheme include the spacing between peripheral holes, the charge amount per peripheral hole, the differential between different sections of boreholes, the decoupling coefficient of peripheral holes, the decoupling coefficient of auxiliary holes, the charge amount of auxiliary holes, the diameter of the explosive cartridge in the peripheral holes, the borehole diameter of the peripheral holes, the charge concentration of the peripheral holes, the offset distance of the explosive cartridge in the peripheral holes, and the minimum resistance line.

3. The asymmetric, uncoupled tunnel smooth blasting method according to claim 2, characterized in that, The decoupling coefficient of the peripheral holes and the offset distance of the explosive charge in the peripheral holes are optimized based on the pressure distribution function of the asymmetric decoupled blasting hole wall; the asymmetric decoupled blasting hole wall pressure distribution function is as follows: ； in, These are the decoupling coefficients. For the density of the explosive, For the detonation velocity of the explosive, and These are the radius of the propellant cartridge and the radius of the borehole, respectively. and These represent the peak pressures exerted on the borehole wall surrounding rock under radial and tangential stresses, respectively. The dynamic lateral pressure coefficient is given by d, where d is the offset distance. This represents the shock wave pressure per unit area of ​​the rock wall in the borehole. and For the uniaxial dynamic compressive strength and dynamic tensile strength of rock, The thermal index of the explosive is calculated using the following formula: That is, the ratio of specific heat capacity at constant pressure to specific heat capacity at constant volume. This is the axial coefficient of the propellant charge. B The dynamic stress coupling coefficient is derived from the rock dynamic Poisson's ratio. The calculation yields the following formula: .

4. The asymmetric, uncoupled tunnel smooth blasting method according to claim 3, characterized in that, The single-hole charge amount in the peripheral holes and the micro-difference between each section of the borehole are determined based on the symmetrical blasting load distribution and the asymmetrical uncoupled blasting hole wall pressure distribution function; the symmetrical blasting load distribution is as follows: ； in, and These represent the radial stress and tangential stress experienced by a spatial infinitesimal element under dynamic load. This represents the shock wave pressure per unit area of ​​the rock wall in the borehole. and For the uniaxial dynamic compressive strength and dynamic tensile strength of rock, The radial decoupling coefficient is... ; .

5. The asymmetric, uncoupled tunnel smooth blasting method according to claim 4, characterized in that, Based on the initial ground stress distribution formula and the symmetrical blasting load distribution, the stress distribution function of a point in the rock mass under coupled action is obtained. Based on the stress distribution function of a point in the rock mass under coupled action, the distribution characteristics of tangential and radial stress at any point in the surrounding rock of the borehole wall under the coupled action of initial ground stress and asymmetric blasting load are obtained. Combined with the VON-MISES failure criterion, it is determined whether the surrounding rock unit has entered the failure state. At the same time, the blasting disturbance damage variable is introduced to obtain the formula for judging the degree of damage to the surrounding rock. Based on the stress distribution function of a point in the rock mass under coupled action and the formula for judging the degree of damage to the surrounding rock, the spacing between peripheral holes, the charge concentration of peripheral holes, the decoupling coefficient of auxiliary holes, and the charge amount of auxiliary holes are determined.

6. The asymmetric, uncoupled tunnel smooth blasting method according to claim 5, characterized in that, Based on the pressure distribution function of the asymmetric uncoupled blasting borehole wall, the stress distribution function of a point in the rock mass under coupling, and the formula for judging the degree of damage to the surrounding rock, the diameter of the explosive cartridge in the peripheral holes, the borehole diameter in the peripheral holes, and the charging concentration in the peripheral holes are optimized.

7. The asymmetric, uncoupled tunnel smooth blasting method according to claim 1, characterized in that, The process of assembling the peripheral hole pre-charged casing device includes: binding the asymmetric uncoupled fine charge casing device to a PVC pipe, and connecting the asymmetric uncoupled fine charge casing devices of each interval charge section with detonating cord to complete the assembly of the peripheral hole pre-charged casing device.

8. The asymmetric, uncoupled tunnel smooth blasting method according to claim 1, characterized in that, Each charging orifice was plugged manually using water-based gun mud as the plugging material.

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