Tunnel blasting excavation method

Abstract

The invention provides a tunnel blasting excavation method which comprises the following steps: S1, constructing a finite element simulation model of a tunnel excavation surface, and carrying out initial blasting design on the finite element simulation model; s2, carrying out influence area division on the finite element simulation model according to a safe vibration velocity threshold value VA; s3, acquiring a vibration velocity peak value Vmax, i of a blasting stress wave suffered by the finite element simulation model; s4, judging whether the vibration velocity peak value Vmax, i of the blasting stress wave is less than or equal to a safe vibration velocity threshold value VA, and if so, not carrying out blasting design adjustment; if not, adjusting the blasting design of the finite element module, and returning to the step S3; s5, blasting is conducted according to the blasting design that the vibration velocity peak value Vmax, i of the blasting stress waves is smaller than the safe vibration velocity threshold value VA; by means of the method, the influence of tunnel blasting on the primary support anchoring and shotcreting structure can be reduced.

Description

Technical Field

[0001] The invention relates to the field of tunnel blasting, and in particular to a tunnel blasting excavation method. Background Art

[0002] In recent years, highway construction in mountainous areas has faced many tunnel projects. As an underground structure that crosses mountains and ridges, tunnels often become a decisive link in the advancement of engineering projects due to their complexity of construction. Nowadays, blasting construction is mostly used for mountain tunnel excavation in China, but blasting construction will produce large vibrations, which have an adverse effect on the tunnel's own structure and the surrounding structures of the tunnel. Especially for large-scale blasting operations, the vibration effect will be more obvious. The primary support structure of the tunnel, as a supporting structure adjacent to the face, is most affected by blasting vibration. For areas with poor geological conditions, blasting construction will cause the rocks around the tunnel to break and cause large surface settlement, which may affect the stability of the primary support structure and the anchor spraying structure.

[0003] Therefore, in order to solve the above technical problems, it is urgent to propose a new technical means. Summary of the invention

[0004] In view of this, in order to avoid the primary support structure and the anchor spraying structure from being damaged by blasting, the present invention proposes a tunnel blasting excavation method.

[0005] The present invention provides a tunnel blasting excavation method, comprising the following steps:

[0006] S1. Constructing a finite element simulation model of the tunnel excavation surface and performing an initial blasting design on the finite element module;

[0007] Blasting design includes: blasting hole layout design and blasting hole detonation sequence design;

[0008] S2. Obtain the safe vibration velocity threshold V of the finite element simulation model A , and according to the safety vibration speed threshold V A Divide the influence area of ​​the finite element simulation model;

[0009] S3. Using numerical simulation method to obtain the vibration velocity peak value V of the blasting stress wave of the finite element simulation model max,i ;

[0010] Among them, V max,i represents the peak value of vibration velocity under the i-th blasting design;

[0011] S4. Determine the peak value V of the blasting stress wave max,i Is it less than or equal to the safety vibration speed threshold V AIf yes, no blasting design adjustment is performed; if no, the blasting design is adjusted and the process returns to step S3 until the vibration velocity peak value V of the blasting stress wave reaches max,i Less than or equal to the safety vibration speed threshold V A ;

[0012] S5. According to the peak value of the vibration velocity V of the blasting stress wave max,i Less than the safety speed threshold V A Blasting is carried out according to the blasting design.

[0013] Furthermore, in step S1, the tunnel excavation face is an excavation face formed by using an up-and-down step method.

[0014] Further, according to the safety vibration speed threshold V A The influence zone division of the finite element simulation model includes: A The area with a vibration velocity greater than 0.3V is divided into the strong influence area. A Less than or equal to 0.6V A The area is divided into weakly affected areas, and the vibration speed is less than or equal to 0.3V A is divided into no-impact zone.

[0015] Further, the adjustment blasting design comprises the following steps:

[0016] S41. Adjust the detonation order of the blast holes in the strongly affected area and the unaffected area in the upper step;

[0017] S42. Adjust the blasting hole arrangement in the strongly affected area and the unaffected area in the lower step.

[0018] Further, the adjustment of the detonation sequence of the blasting holes on the upper step includes:

[0019] Determining the target space includes: selecting a strong influence zone in the upper step whose vibration velocity peak value is greater than the safety vibration velocity threshold, and a non-influence zone adjacent to the strong influence zone, and judging whether the blasting sequence number of the blasting hole in the strong influence zone is before the blasting sequence number of the blasting hole in the non-influence zone; if so, connecting the center point of the strong influence zone and the center point of the non-influence zone by a line, and making a sphere with the midpoint of the connecting line as the center of the sphere and the midpoint of the connecting line to the center point of the strong influence zone as the radius, and the space inside the sphere is the target space; if not, selecting another non-influence zone adjacent to the strong influence zone for judgment until the target space is determined;

[0020] The blasting numbers of the blasting holes in the strong influence zone in the target space are correspondingly exchanged with the blasting numbers of the blasting holes in the weak influence zone in the target space in sequence from front to back.

[0021] Furthermore, the adjustment of the blasting hole arrangement of the lower step includes: increasing the spacing distance between the blasting holes in the strong impact zone, and reducing the spacing distance between the blasting holes in the non-impact zone.

[0022] Furthermore, the initial blasting hole layout design includes: arranging slot holes, auxiliary holes, peripheral holes and bottom plate holes on the upper step; and arranging ground holes and peripheral holes on the lower step.

[0023] Furthermore, the initial blasting hole detonation sequence includes: the blasting holes on the upper step and the lower step are blasted simultaneously, wherein the blasting holes on the upper step are blasted in the order of groove holes, auxiliary holes, peripheral holes and bottom plate holes, and the blasting holes on the lower step are blasted in the order of horizontal holes and peripheral holes.

[0024] Beneficial effects of the present invention: The tunnel blasting design method in the present application is universal for tunnel blasting designs under various primary support structure conditions, can quickly complete the adjustment of the blasting design, avoid the primary support structure being damaged by blasting, resulting in tunnel safety accidents, effectively control blasting vibrations, and improve the safety of the tunnel blasting excavation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0026] Figure 1 It is a flow chart of the present invention.

[0027] Figure 2 Schematic diagram of the cut hole structure in this embodiment.

[0028] Figure 3 This is a distribution diagram of blasting holes in this embodiment. DETAILED DESCRIPTION

[0029] The present invention is further described below in conjunction with the accompanying drawings:

[0030] The present invention provides a tunnel blasting excavation method, comprising the following steps:

[0031] S1. Constructing a finite element simulation model of the tunnel excavation surface and performing an initial blasting design on the finite element module;

[0032] Blasting design includes: blasting hole layout design and blasting hole detonation sequence design;

[0033] S2. Obtain the safe vibration velocity threshold V of the finite element simulation model A , and according to the safety vibration speed threshold V A Divide the influence area of ​​the finite element simulation model;

[0034] S3. Using numerical simulation method to obtain the vibration velocity peak value V of the blasting stress wave of the finite element simulation model max,i ;

[0035] Among them, V max,i represents the peak value of vibration velocity under the i-th blasting design;

[0036] S4. Determine the peak value V of the blasting stress wave max,i Is it less than or equal to the safety vibration speed threshold V A If yes, no blasting design adjustment is performed; if no, the blasting design is adjusted and the process returns to step S3 until the vibration velocity peak value V of the blasting stress wave reaches max,i Less than or equal to the safety vibration speed threshold V A ;

[0037] S5. According to the peak value of the vibration velocity V of the blasting stress wave max,i Less than the safety speed threshold V A The above method can reduce the impact of tunnel blasting on the primary anchor spraying structure.

[0038] In actual engineering, when the vibration velocity of the stress wave generated by blasting is greater than the critical vibration velocity of the primary support structure, the primary support structure will be destroyed, leading to the occurrence of tunnel safety accidents. Whether the blasting vibration is effectively controlled is an important factor in determining whether the primary support structure is safe during tunnel blasting excavation. Therefore, it is urgent and necessary to study and analyze the impact of blasting vibration on the primary support structure.

[0039] In this embodiment, in step S1, a finite element simulation model of a tunnel excavation surface is constructed, and an initial blasting design is performed on the finite element module; the tunnel excavation surface is an excavation surface formed by an up-and-down step method;

[0040] Among them, the finite element simulation model in this embodiment is constructed using ANSYS software; the finite element simulation model replaces the geotechnical engineering research object with an approximately equivalent physical model composed of multiple interconnected unit bodies. Constructing a finite element simulation model of a tunnel section is an existing technology, and the construction process will not be described in detail here.

[0041] Blasting design includes: blasting hole layout design and blasting hole detonation sequence design;

[0042] The initial blasting design shall be based on the actual hydrogeological conditions of the tunnel project, the lithology of the strata, and the grade of the surrounding rock, and shall be initially drawn up with reference to the tunnel blasting design and construction project plan. It shall also include the design parameters of the explosives in the blast hole, which shall be determined based on the blasting objectives and costs and according to experience;

[0043] In this embodiment, the initial blast hole layout design includes: setting slot holes, auxiliary holes, peripheral holes and bottom plate holes on the upper step; setting ground level holes and peripheral holes on the lower step;

[0044] The blasting holes are designed to be bilaterally symmetrical with the center line of the excavation surface as the symmetry axis. The slot holes are located in the middle of the tunnel and are arranged in three layers and six rows in a wedge shape. Figure 2 As shown, the bottom of the groove hole is inclined toward the tunnel contour line and extends to the tunnel bottom contour line position; the peripheral holes are distributed along the circumferential direction of the contour line of the tunnel inner wall curved surface, and the distance between the peripheral holes and the tunnel inner wall curved surface is 0.5-0.7m, and the closer the peripheral holes are to the tunnel inner wall corner, the closer they are to the tunnel inner wall curved surface; the auxiliary holes are evenly distributed between the groove holes and the peripheral holes, the direction of the auxiliary holes is perpendicular to the tunnel excavation surface, and the spacing between the auxiliary holes is 0.8-1m; the bottom plate holes are horizontally distributed on the interface between the upper step and the lower step, and the spacing between the bottom plate holes is 0.8-1m; the direction of the horizontal holes is perpendicular to the tunnel excavation surface, and they are evenly distributed in an array on the lower step, and the spacing between the horizontal holes is 0.8-1m, as shown Figure 3 (a) shown.

[0045] Compared with straight hole cuts, wedge-shaped cuts require fewer holes, resulting in less charge per cycle, and the cut cavity volume is larger, which is more conducive to expanding the free surface, thereby reducing the rock clamping force around the auxiliary hole and creating better blasting conditions for the auxiliary hole.

[0046] In this embodiment, the initial blasting hole detonation sequence includes: the blasting holes of the upper step and the lower step are blasted synchronously, wherein the blasting holes of the upper step are blasted in the order of the slot holes, the auxiliary holes, the peripheral holes and the bottom plate holes, and the blasting holes of the lower step are blasted in the order of the horizontal holes and the peripheral holes, and the detonation sequence of the horizontal holes on the left and right sides of the excavation surface of the lower step is consistent. More specifically, the initial detonation sequence of the blasting holes on the same blasting chain is from left to right, such as Figure 3 As shown in (b), taking chain 19 as an example, the blasting sequence is abcdefghij.

[0047] In this embodiment, in step S2, the safety vibration velocity threshold V of the finite element simulation model is obtained. A , and according to the safety vibration speed threshold V A Divide the influence area of ​​the finite element simulation model;

[0048] The safety vibration speed threshold V A The influence zone division of the finite element simulation model includes: A The area with a vibration velocity greater than 0.3V is divided into the strong influence area. ALess than or equal to 0.6V A The area is divided into weakly affected areas, and the vibration speed is less than or equal to 0.3V A The area is divided into no-impact areas;

[0049] The safe vibration velocity threshold can be determined based on experience. In this embodiment, the safe vibration velocity threshold is determined by the following method: the concrete grade of the primary support structure is obtained, and the vibration velocity threshold of each grade of concrete can be obtained according to the concrete tensile strength design value and elastic modulus in the concrete structure design specification. 1.2 times of the concrete vibration velocity threshold is taken as the safe vibration velocity threshold. If the value of the safe vibration velocity threshold is selected too high, it may result in that the safe vibration velocity threshold is not met no matter how the blasting design is adjusted;

[0050] Specifically, according to the concrete tensile strength design value in the concrete structure design code (GB50010-2010), the vibration velocity threshold of each grade of concrete can be obtained, as shown in Table 1 below:

[0051]

[0052] Table 1 Vibration velocity thresholds corresponding to the design values ​​of concrete tensile strength

[0053] As shown in Table 1, the safe vibration speed threshold is 1.2 times the vibration speed threshold.

[0054] By dividing different areas according to the vibration velocity value, the impact range and intensity of blasting vibration can be controlled more accurately, so as to make targeted adjustments.

[0055] In this embodiment, in step S3, a numerical simulation method is used to obtain the peak value V of the blasting stress wave received by the finite element simulation model. max,i ;

[0056] Among them, V max,i represents the peak value of vibration velocity under the i-th blasting design; when i=1, it represents the peak value of vibration velocity under the initial blasting design;

[0057] The specific numerical simulation method used is not limited here. This application gives priority to the nonlinear contact analysis simulation method in ANSYS software to obtain the vibration velocity and vibration velocity peak of the stress wave; the nonlinear contact analysis simulation method is a prior art and is not described in detail here; the use of ANSYS software can simulate various stages of tunnel excavation, taking into account the sliding of strata and the erosion between weak surfaces, and the simulation is more complex and consistent with the actual stratum distribution; and the use of nonlinear analysis method takes into account the plastic deformation of the surrounding rock, and the simulation is more consistent with the actual tunnel engineering; in addition, the contact analysis method can be used together with fluid-solid coupling analysis and the MISES criterion to complicate the simulated rock stratum distribution and other conditions, making it more comprehensive, improving the accuracy of the simulation results, and making the entire tunnel blasting process more consistent with engineering reality.

[0058] In this embodiment, in step S4, the peak value V of the vibration velocity of the blasting stress wave is determined. max,i Is it less than or equal to the safety vibration speed threshold V A If yes, no blasting design adjustment is performed; if no, the blasting design is adjusted and the process returns to step S3 until the vibration velocity peak value V of the blasting stress wave reaches max,i Less than or equal to the safety vibration speed threshold V A ;

[0059] The method of adjusting the blasting design in the present application is aimed at ensuring that the overall blasting equivalent remains unchanged. In this case, the peak value of the vibration velocity of the blasting stress wave is reduced by transferring the blasting stress wave from the strong impact zone to the adjacent unaffected zone; that is, while ensuring the explosion effect, avoiding exceeding the safe vibration velocity threshold, thereby reducing the impact on the primary anchor spraying structure.

[0060] The adjustment blasting design comprises the following steps:

[0061] S41. Adjust the detonation order of the blast holes in the strongly affected area and the unaffected area in the upper step;

[0062] The detonation sequence of adjusting the blasting holes on the upper step includes:

[0063] Determining the target space includes: selecting a strong influence zone in the upper step whose vibration velocity peak value is greater than the safety vibration velocity threshold, and a non-influence zone adjacent to the strong influence zone, and judging whether the blasting sequence number of the blasting hole in the strong influence zone is before the blasting sequence number of the blasting hole in the non-influence zone; if so, connecting the center point of the strong influence zone and the center point of the non-influence zone by a line, and making a sphere with the midpoint of the connecting line as the center of the sphere and the midpoint of the connecting line to the center point of the strong influence zone as the radius, and the space inside the sphere is the target space; if not, selecting another non-influence zone adjacent to the strong influence zone for judgment until the target space is determined;

[0064] Among them, the non-influenced area adjacent to the strong influence area means that there is at most one weak influence area between it and the strong influence area;

[0065] The blasting numbers of the blasting holes in the strong influence area in the target space are correspondingly exchanged with the blasting numbers of the blasting holes in the weak influence area in the target space in order from front to back;

[0066] Specific as Figure 3 As shown in (b), taking chain 19 as an example, the initial blasting sequence is abcdefghij;

[0067] Among them, blasting holes b, c and d are located in the strong influence zone, blasting holes e, f, g and h are located in the weak influence zone, and blasting holes i and j are located in the non-influence zone. The target space includes blasting holes c and d in the strong influence zone, and blasting holes i and j in the non-influence zone. If the stress wave in the strong influence zone is transferred to the weak influence zone, it may cause the stress wave vibration velocity in the weak influence zone to exceed the safe vibration velocity threshold. Therefore, the strong influence zone and the non-influence zone should be adjusted. According to the above adjustment method, the blasting sequence c and the blasting sequence j are interchanged, and the blasting sequence d and the blasting sequence i are interchanged to obtain the adjusted blasting sequence; the above adjustment method can reduce the range of the strong influence zone or reduce the threshold amplitude exceeded by the vibration velocity peak of the blasting stress wave; if there is still a vibration velocity peak of the blasting stress wave exceeding the safe vibration velocity threshold, the next target space can be found to adjust the detonation sequence. According to a large number of engineering experiments, the blasting sequence adjustment of the strong influence zone and the non-influence zone in the target space is performed at most twice to achieve the required blasting stress wave impact transfer amount.

[0068] S42. Adjust the blasting hole arrangement in the strongly affected area and the unaffected area of ​​the lower step;

[0069] The adjustment of the blasting hole arrangement of the lower step includes: increasing the spacing between the blasting holes in the strong influence zone and reducing the spacing between the blasting holes in the uninfluence zone, so as to realize the transfer of the blasting stress wave from the strong influence zone to the adjacent uninfluence zone.

[0070] Through the above method, not only can the adjustment be carried out quickly and effectively, but also the influence of the blasting stress wave on the primary anchor spraying structure can be reduced while ensuring the blasting effect.

[0071] In this embodiment, in step S5, according to the peak value V of the blasting stress wave, max,i Less than the safety speed threshold V A The blasting design is used for blasting. In this embodiment, smooth blasting and digital electronic detonators are preferably used. The smooth blasting technology is a prior art and will not be described in detail here.

[0072] Acoustic detection data show that when using smooth blasting technology, the relaxation range of the surrounding rock is only 1 / 2 to 1 / 3 of that of ordinary blasting methods, and no or fewer blasting cracks are produced, which effectively maintains the integrity of the surrounding rock and reduces the reduction in the bearing capacity of the surrounding rock, providing a favorable basis for anchor spraying support. The close combination of smooth blasting and anchor spraying technology further enhances the role of anchor spraying support. The safety factor of the tunnel using digital electronic detonators is improved compared to that using ordinary detonating cord detonators.

[0073] This application can also strengthen monitoring measures and reinforce supports to avoid damage to the primary support structure due to blasting.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A tunnel blasting excavation method, characterized in that: The following steps are involved: S1. Constructing a finite element simulation model of the tunnel excavation surface and performing an initial blasting design on the finite element module; Blasting design includes: blasting hole layout design and blasting hole detonation sequence design; S2. Obtain the safe vibration velocity threshold V of the finite element simulation model A , and according to the safety vibration speed threshold V A Divide the influence area of ​​the finite element simulation model; S3. Using numerical simulation method to obtain the vibration velocity peak value V of the blasting stress wave of the finite element simulation model max,i ; Among them, V max,i represents the peak value of vibration velocity under the i-th blasting design; S4. Determine the peak value V of the blasting stress wave max,i Is it less than or equal to the safety vibration speed threshold V A If yes, then the blasting design is not adjusted and the process goes to step S5; if no, then the blasting design is adjusted and the process goes back to step S3 until the peak value V of the blasting stress wave reaches max,i Less than or equal to the safety vibration speed threshold V A ; S5. According to the peak value of the vibration velocity V of the blasting stress wave max,i Less than the safety speed threshold V A Blasting is carried out according to the blasting design.

2. The tunnel blasting excavation method according to claim 1, characterized in that: In step S1, the tunnel excavation face is an excavation face formed by using an up-and-down step method.

3. The tunnel blasting excavation method according to claim 2, characterized in that: The safety vibration speed threshold V A The influence zone division of the finite element simulation model includes: A The area with a vibration velocity greater than 0.3V is divided into the strong influence area. A Less than or equal to 0.6V A The area is divided into weakly affected areas, and the vibration speed is less than or equal to 0.3V A is divided into no-impact zone.

4. The tunnel blasting excavation method according to claim 3, characterized in that: The adjustment blasting design comprises the following steps: S41. Adjust the detonation order of the blast holes in the strongly affected area and the unaffected area in the upper step; S42. Adjust the blasting hole arrangement in the strongly affected area and the unaffected area in the lower step.

5. The tunnel blasting excavation method according to claim 4, characterized in that: The detonation sequence of adjusting the blasting holes on the upper step includes: Determining the target space includes: selecting a strong influence zone in the upper step whose vibration velocity peak value is greater than the safety vibration velocity threshold, and a non-influence zone adjacent to the strong influence zone, and judging whether the blasting sequence number of the blasting hole in the strong influence zone is before the blasting sequence number of the blasting hole in the non-influence zone; if so, connecting the center point of the strong influence zone and the center point of the non-influence zone by a line, and making a sphere with the midpoint of the connecting line as the center of the sphere and the midpoint of the connecting line to the center point of the strong influence zone as the radius, and the space inside the sphere is the target space; if not, selecting another non-influence zone adjacent to the strong influence zone for judgment until the target space is determined; The blasting numbers of the blasting holes in the strong influence zone in the target space are correspondingly exchanged with the blasting numbers of the blasting holes in the weak influence zone in the target space in sequence from front to back.

6. The tunnel blasting excavation method according to claim 4, characterized in that: The adjustment of the blasting hole arrangement of the lower step includes: increasing the spacing distance between the blasting holes in the strong impact zone, and reducing the spacing distance between the blasting holes in the non-impact zone.

7. The tunnel blasting excavation method according to claim 2, characterized in that: The initial blasting hole arrangement design includes: arranging slot holes, auxiliary holes, peripheral holes and bottom plate holes on the upper step; and arranging ground holes and peripheral holes on the lower step.

8. The tunnel blasting excavation method according to claim 7, characterized in that: The initial blasting hole detonation sequence includes: the blasting holes of the upper step and the lower step are blasted simultaneously, wherein the blasting holes of the upper step are blasted in the order of the groove holes, the auxiliary holes, the peripheral holes and the bottom plate holes, and the blasting holes of the lower step are blasted in the order of the horizontal holes and the peripheral holes.

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