Controlled blasting construction method for soft rock tunnel to underpass existing old railway tunnel in close range

Abstract

The invention relates to the field of construction methods, and provides a blasting control construction method for a soft rock tunnel to underpass an existing old railway tunnel in a close range. The invention discloses a controlled blasting construction method for a soft rock tunnel to underpass an existing old railway tunnel in a close range. The method comprises the following steps: selecting a partial bench method for excavation according to surrounding rock grades; in the excavation process, the reserved deformation amount is dynamically adjusted according to the surrounding rock monitoring and measuring result; blast holes are annularly arranged according to the upper step and linearly arranged according to the middle and lower steps; designing a slotting mode according to the grade of the surrounding rock; a non-coupling charging structure is determined through numerical simulation; the blasting vibration velocity is calculated through a Sadgowski formula, and the maximum starting explosive quantity of a single section is controlled; setting a detonating sequence; lining displacement, settlement and cracks of the existing tunnel are monitored in real time, and the blasting vibration velocity is monitored during blasting. According to the blasting control construction method for the soft rock tunnel to pass through the existing old railway tunnel in the close range, the problem of vibration of the existing tunnel caused by blasting of the newly-built tunnel is solved, and the blasting vibration speed is controlled within the bearable range of the lining structure of the existing tunnel.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of construction methods, and provides a soft rock tunnel near-distance underpassing existing old railway tunnel controlled blasting construction method. BACKGROUND

[0002] In the field of railway transportation, the newly-built large-section soft rock tunnel often needs to pass through the existing old tunnel at a short distance in the design. In this case, the conventional blasting construction method may cause significant blasting vibration damage to the existing tunnel in the construction process. Such vibration not only causes damage to the lining structure of the existing tunnel, but also may cause vibration resonance of the track and vehicle, and even endanger personal safety. In recent years, with the rapid development of railway transportation, the operation safety of the existing railway has become the focus of attention of the society. Therefore, an improved blasting technology scheme is urgently needed, which can not only ensure the safety of the new tunnel construction, but also does not affect the operation of the existing tunnel. SUMMARY

[0003] The embodiment of the present application provides a soft rock tunnel near-distance underpassing existing old railway tunnel controlled blasting construction method, which is used to solve the problem of vibration of the existing tunnel caused by blasting of the newly-built tunnel in the related art.

[0004] The embodiment of the present application provides a soft rock tunnel near-distance underpassing existing old railway tunnel controlled blasting construction method, which comprises the following steps: According to the surrounding rock grade, a partial bench method is selected for excavation, a two-bench method is used for four-grade surrounding rock, the upper bench height is 6-8 meters, the bench length is 40-50 meters, and the cycle footage is 3-arch spacing, a three-bench method is used for five-grade surrounding rock, the height of each bench is about one-third of the design height, the upper bench height is 3-5 meters, the bench length is 4-6 meters, and the cycle footage is 2-arch spacing; During the excavation process, the reserved deformation is dynamically adjusted according to the surrounding rock monitoring measurement results, 8-12 cm is reserved for four-grade surrounding rock, and 12-17 cm is reserved for five-grade surrounding rock, and the excavation contour is enlarged by 5 cm compared with the design; The blast holes are arranged in a ring shape on the upper bench and in a linear arrangement on the middle and lower benches, wherein the peripheral hole spacing is 0.3-0.5 meters, the free blasting layer thickness is 1.25 times the peripheral hole spacing, the auxiliary hole resistance line is 0.6-1 meter, the blast hole spacing is 1-2 times the resistance line, when the hole depth is less than or equal to 3 meters, the outward insertion angle slope of the peripheral hole is 5 cm / m, and when the hole depth is greater than 3 meters, the outward insertion angle slope of the peripheral hole is 3 cm / m; According to the surrounding rock grade, a slotting mode is designed, a single-stage wedge slotting is used for five-grade surrounding rock, the slotting angle is 60-75 degrees, and a two-stage or complex wedge slotting is used for four-grade and above surrounding rock, and the slotting area is arranged below the excavation section; The non-coupling charge structure is determined by numerical simulation, the non-coupling coefficient of the peripheral hole is 0.60, the non-coupling coefficient of other holes is less than or equal to 0.76, the linear charge density of the peripheral hole is 0.1-0.2 kg / m, and all blast holes adopt reverse charge structure; The blasting vibration velocity is calculated by the Sadovnikov formula, and the maximum single-stage initiation explosive amount is controlled; The blast hole is cleaned by high-pressure air, and the stemming is filled after charging, the plugging length of the peripheral hole is greater than or equal to 0.3 m, and the plugging length of other holes is greater than or equal to 0.5 m; The initiation sequence is set as a cutting hole, an expansion hole, a driving hole, an inner ring hole, the peripheral hole and a floor hole, the digital electronic detonator is used for segmented initiation, the peripheral hole is fired simultaneously, the number of simultaneous firing is not less than 5 when control is needed, and the time difference of each stage initiation is less than 25 ms; the interval time of each stage blasting of the cutting hole is 50 ms, each cutting hole is initiated simultaneously, subsequent blast holes are arranged segment by segment, and the blasting interval time of the gas tunnel from initiation to the last segment is not more than 130 ms, and the interval time of the general surrounding rock segment can be delayed to 200-300 ms; A warning area is set, the initiation station is arranged at a safe position, and ventilation is performed for 15 minutes after initiation; The lining displacement, settlement and cracks of the existing tunnel are monitored in real time, and the blasting vibration velocity is monitored during blasting; The blasting parameters are continuously optimized and adjusted according to the blasting effect by trial blasting cycle, and the single-hole charge amount, blast hole spacing, blast hole number and cycle footage parameters are recorded. According to an embodiment of the present application, in the two-step method, the cycle footage of the lower step is increased by 1 arch spacing compared with that of the upper step, and in the three-step method, the cycle footage of the middle and lower steps is increased by 1 arch spacing compared with that of the upper step, and the two sides are staggered by 2-3 m.

[0005] According to an embodiment of the present application, the blast hole diameter is 42 mm, the bottom of the peripheral hole and the auxiliary hole is located in the same vertical plane, and the cutting hole and the expansion hole are deepened by 10-20 cm.

[0006] According to an embodiment of the present application, in the non-coupling charge structure, the peripheral hole adopts small cartridge, interval charging and connection of detonating cord transmission, other holes adopt continuous charging, and all adopt reverse charge structure, and the positive charge structure is adopted in the gas environment.

[0007] According to an embodiment of the present application, the single-hole charge amount and the single-stage primary initiation explosive amount of the cutting hole and the auxiliary hole are determined according to the blasting vibration velocity control requirement, and the charge amount of the peripheral hole is adjusted according to the blast hole spacing, the minimum resistance line and the linear charge density.

[0008] According to an embodiment of the present application, the initiation network is a series method, the outside pipe is networked, each group of detonating pipes is not more than 20, and the initiation station is arranged at a safe position.

[0009] According to one embodiment of the present application, the post-blasting muck size is controlled at 5 to 70 centimeters, and if the size is abnormal, the blast hole spacing and single-hole charge amount are adjusted.

[0010] According to one embodiment of the present application, the pre-reserved deformation amount is dynamically adjusted according to the surrounding rock monitoring measurement results, and the excavation profile is expanded by 5 centimeters compared with the design.

[0011] According to one embodiment of the present application, the overbreak, underbreak, residual hole preservation rate and cycle length are recorded during the trial blasting process, and the blasting parameters are optimized in combination with the geological sketch data.

[0012] According to one embodiment of the present application, the blind blasting treatment includes reinitiation, parallel hole blasting, mechanical cleaning or induced blasting.

[0013] The soft rock tunnel close-range underpassing old railway tunnel controlled blasting construction method provided by the embodiment of the present application ensures the safety of blasting operation, reduces the blasting vibration influence on the old railway tunnel, and reduces the construction risk through fine construction steps and technical parameter design. Reasonable blast hole arrangement, slotting mode design and charge structure selection are helpful to achieve the expected blasting effect and improve the construction efficiency. By monitoring the displacement, settlement and crack conditions of the existing tunnel lining in real time and monitoring the blasting vibration velocity during blasting, the structural safety of the old railway tunnel is effectively protected. Controlling the maximum charge amount of a single segment and reasonably setting the initiation time difference are helpful to reduce the influence of blasting operation vibration on the surrounding environment and realize green construction. The whole construction method has clear steps and simple operation, which is helpful to improve the construction efficiency and shorten the construction period. BRIEF DESCRIPTION OF DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the present application or prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0015] Figure 1 is a schematic flow chart of the soft rock tunnel close-range underpassing old railway tunnel controlled blasting construction method provided by the present application. DETAILED DESCRIPTION

[0016] The embodiments of the present application will be further described in detail below in combination with the drawings and embodiments. The following embodiments are used to illustrate the present application, but cannot be used to limit the scope of the present application.

[0017] As Figure 1As shown in the figure, this embodiment of the invention provides a controlled blasting construction method for soft rock tunnels passing close to existing old railway tunnels, including the following steps: Step 10: Select the partial bench excavation method according to the surrounding rock grade. For Grade IV surrounding rock, the two-bench method is used, with the upper bench height being 6 to 8 meters, the bench length being 40 to 50 meters, and the cycle advance being 3 arch frame spacings. For Grade V surrounding rock, the three-bench method is used, with each bench height being approximately one-third of the design height, the upper bench height being 3 to 5 meters, the bench length being 4 to 6 meters, and the cycle advance being 2 arch frame spacings. Step 20: During the excavation process, the reserved deformation amount is dynamically adjusted based on the monitoring and measurement results of the surrounding rock. The reserved amount is 8 to 12 cm for Class IV surrounding rock and 12 to 17 cm for Class V surrounding rock. At the same time, the excavation outline is expanded by 5 cm compared with the design. Step 30: Arrange the blast holes in a ring pattern on the upper step and in a linear pattern on the middle and lower steps. The spacing between the peripheral holes is 0.3 to 0.5 meters, the thickness of the light blast layer is 1.25 times the spacing between the peripheral holes, the resistance line of the auxiliary holes is 0.6 to 1 meter, the spacing between the blast holes is 1 to 2 times the resistance line, the slope of the outer insertion angle of the peripheral holes is 5 cm / m when the hole depth is less than or equal to 3 meters, and 3 cm / m when the hole depth is greater than 3 meters. Step 40: Design the excavation method according to the surrounding rock level. For Class V surrounding rock, a single-stage wedge excavation is adopted with an excavation angle of 60 to 75 degrees. For Class IV and above surrounding rock, a two-stage or compound wedge excavation is adopted. The excavation area is arranged in the middle and lower part of the excavation section. Step 50: Determine the uncoupled charge structure through numerical simulation. The uncoupled coefficient of the peripheral holes is 0.60, the uncoupled coefficient of other holes is less than or equal to 0.76, the linear charge density of the peripheral holes is 0.1 to 0.2 kg / m, and all boreholes adopt a reverse charge structure. Step 60: Calculate the blasting vibration velocity using the Sadovsky formula to control the maximum amount of explosive initiation in a single stage; Step 70: Clean the blast holes with high-pressure air, fill them with blasting mud after loading explosives, and ensure that the plugging length of the peripheral holes is greater than or equal to 0.3 meters and the plugging length of the other holes is greater than or equal to 0.5 meters. Step 80: Set the detonation sequence as follows: slotting hole, widening hole, excavation hole, inner ring hole, peripheral hole, and bottom plate hole. Use digital electronic detonators for segmented detonation. The peripheral holes are detonated simultaneously. When control is required, the number of simultaneous detonations should not be less than 5, and the detonation time difference between each segment should not be less than 25 milliseconds. The detonation interval between each level of the slotting hole is 50 milliseconds. Each level of slotting hole is detonated simultaneously, and subsequent blasting holes are arranged segment by segment. The detonation interval from the start of the gas tunnel to the last segment should not exceed 130 milliseconds. The interval for the surrounding rock section can generally be delayed to 200-300 milliseconds. Step 90: Set up a warning zone, place the detonation station in a safe location, and ventilate for 15 minutes after detonation; Step 100: Monitor the displacement, settlement and cracks of the existing tunnel lining in real time, and monitor the blasting vibration velocity during blasting; Step 110: Perform a test blasting cycle, recording the charge amount per hole, hole spacing, number of holes, and cycle advance parameters. Continuously optimize and adjust the blasting parameters based on the blasting effect.

[0018] The controlled blasting method for close-proximity tunneling under existing aging railway tunnels in soft rock, provided by embodiments of the present invention, ensures the safety of blasting operations, minimizes the impact on existing aging railway tunnels, and reduces construction risks through meticulous construction steps and technical parameter design. Reasonable borehole layout, slotting method design, and charge structure selection help achieve the expected blasting effect and improve construction efficiency. Real-time monitoring of the displacement, settlement, and cracks in the existing tunnel lining, along with monitoring blasting vibration velocity during blasting, effectively protects the structural safety of the existing aging railway tunnel. Controlling the maximum charge per section and setting a reasonable detonation time difference helps reduce the impact of blasting vibration on the surrounding environment, achieving green construction. The entire construction method has clear steps and is easy to operate, contributing to improved construction efficiency and shorter construction period.

[0019] Please continue reading Figure 1 This invention proposes a controlled blasting method for soft rock tunnels passing close to existing old railway tunnels. The core of this method lies in ensuring the safety and efficiency of the blasting operation through meticulous construction steps and technical parameter design, while minimizing the impact of blasting vibrations on the existing old railway tunnel structure.

[0020] First, selecting the appropriate bench excavation method based on the surrounding rock grade helps stabilize the tunnel excavation face and reduce surrounding rock deformation. For Grade IV surrounding rock, a two-bench method is used, with specific upper bench height, bench length, and cycle advance set; for Grade V surrounding rock, a three-bench method is used, with corresponding adjustments to the height of each bench and cycle advance.

[0021] Secondly, regarding the arrangement of blast holes, the arrangement was carried out according to the principle of upper step ring arrangement and middle and lower step linear arrangement. Key parameters such as peripheral hole spacing, light blast layer thickness, auxiliary hole resistance line, hole spacing, hole depth and external insertion angle slope were strictly set to ensure that the blasting effect meets the design requirements.

[0022] Furthermore, in terms of the design of the cutting method, a single-stage wedge cutting or a two-stage / compound large-angle wedge cutting should be selected according to the surrounding rock grade, and the location of the cutting area should be reasonably arranged to improve blasting efficiency.

[0023] Secondly, regarding the charge structure, the decoupled charge structure was determined through numerical simulation, and different decoupling coefficients and linear charge densities were set for different borehole types. All boreholes adopted a reverse charge structure to optimize the blasting effect.

[0024] Furthermore, this method also calculates the blasting vibration velocity using the Sadovsky formula to control the maximum amount of explosive initiation in a single stage, further ensuring the safety of blasting operations.

[0025] Secondly, regarding the detonation sequence and detonation time difference, by precisely setting the detonation sequence and using digital electronic detonators for segmented detonation, the detonation time difference of each segment is controlled within a reasonable range.

[0026] Furthermore, the actual construction process also includes steps such as using high-pressure air to clean the blast holes and fill them with blast mud, setting up warning zones, detonation stations and ventilation after detonation, and real-time monitoring of existing tunnel lining displacement, settlement and cracks, as well as monitoring blasting vibration velocity during blasting, to ensure construction quality and safety.

[0027] Finally, test firing cycles are conducted, recording the charge amount, borehole spacing, number of boreholes, and cycle advance parameters. The blasting parameters are continuously optimized and adjusted based on the blasting effect.

[0028] According to one embodiment of the present invention, in the two-step method, the cyclic advance of the lower step is increased by the spacing of one arch frame compared to the upper step; in the three-step method, the cyclic advance of the middle and lower steps is increased by the spacing of one arch frame compared to the upper step, and the two sides are staggered by 2 to 3 meters.

[0029] In one embodiment of the present invention, for the construction of soft rock tunnels using the two-stage method and the three-stage method, the cyclic advance relationship between each stage is further refined, as well as the staggered arrangement requirements between the middle and lower stages in the three-stage method.

[0030] When using the two-stage method for construction, the cyclic advance of the upper stage is already set at a spacing of 3 arch frames based on the surrounding rock grade. According to the detailed requirements of this embodiment, the cyclic advance of the lower stage is increased by 1 arch frame spacing compared to the upper stage. This means that if the cyclic advance of the upper stage is 3 arch frame spacings, then the cyclic advance of the lower stage will be 4 arch frame spacings. This design helps to better balance construction speed and surrounding rock stability, ensuring the smooth progress of the construction process.

[0031] When using the three-stage method for construction, the cyclic advance of the upper stage is already set at a spacing of 2 arch frames based on the surrounding rock grade. According to the detailed requirements of this embodiment, the cyclic advance of the middle and lower stages is increased by 1 arch frame spacing compared to the upper stage. Therefore, the cyclic advance of the middle and lower stages will be a spacing of 3 arch frames. Furthermore, to ensure the balance and safety of the construction process, the middle and lower stages need to be staggered in the length direction, with a stagger distance set at 2 to 3 meters. This design helps reduce mutual interference during construction, improves construction efficiency, and ensures the overall stability of the tunnel structure.

[0032] By refining the cyclic advance relationships between each step, the construction process becomes more orderly and efficient. Simultaneously, the staggered arrangement of the middle and lower steps reduces interference between construction procedures, further improving efficiency. Reasonable cyclic advances and staggered arrangements help better control surrounding rock deformation and enhance the overall stability of the tunnel. This is particularly important for soft rock tunnel construction, helping to reduce the risk of safety accidents during construction. Detailed construction steps and parameter design help construction units more accurately allocate construction resources and plans, improve resource utilization efficiency, and reduce construction costs.

[0033] According to one embodiment of the present invention, the borehole diameter is 42 mm, the bottom of the peripheral holes and the auxiliary holes are located on the same vertical plane, and the slotting holes and the enlarged slotting holes are deepened by 10 to 20 cm.

[0034] In one embodiment of the present invention, in the controlled blasting construction method for soft rock tunnels passing close to existing old railway tunnels, the diameter of blast holes, the relationship between peripheral holes and auxiliary holes, and the depth of slotting holes and enlarged holes are further specified in detail.

[0035] The borehole diameter was set at 42 mm. This diameter was chosen based on a comprehensive consideration of factors such as rock hardness and blasting scale, aiming to ensure sufficient blasting force while controlling drilling difficulty and explosive usage.

[0036] The bottoms of the peripheral holes and auxiliary holes (including collapse holes) are located on the same vertical plane. This design helps ensure the smoothness of the excavation section after blasting, reduces over-excavation and under-excavation, thereby optimizing construction quality and reducing construction costs.

[0037] The cut holes and enlarged holes are 10 to 20 centimeters deeper than other blast holes. This deepening design helps to better break the rock, improve cut hole efficiency, and create more favorable conditions for subsequent blasting.

[0038] The 42mm borehole diameter allows for a larger amount of explosives, providing greater blasting force and accelerating construction. The deepened design of the cut holes and enlarged holes more effectively breaks the rock, reducing the number of blasts and the amount of explosives used, further improving blasting efficiency. The design of having the bottoms of peripheral and auxiliary holes on the same vertical plane helps ensure the smoothness of the excavation section, reducing construction errors and subsequent processing workload. Precise borehole layout and depth control help reduce over-excavation and under-excavation, protecting the structural safety of existing aging railway tunnels. By improving blasting efficiency and optimizing construction quality, the amount of explosives used, construction time, and labor costs can be reduced, thereby lowering the overall construction cost. Precise borehole layout and depth control help reduce uncertainties and risks during construction, improving construction safety.

[0039] Meanwhile, by monitoring the displacement, settlement, and cracks of existing tunnel linings in real time, and by monitoring the blasting vibration velocity during blasting, the safety and stability of the construction process can be further ensured.

[0040] According to one embodiment of the present invention, in the uncoupled charge structure, the peripheral holes are filled with small explosive cartridges, spaced charges and connected with detonating cords for detonation transmission, while other holes are filled with continuous charges. All of them adopt a reverse charge structure, and a forward charge structure is adopted in a gas environment.

[0041] In one embodiment of the invention, the decoupled charge structure has been further optimized and applied. This structure is particularly suitable for controlled blasting operations in soft rock tunnels that pass close to existing old railway tunnels.

[0042] The peripheral holes employ a spaced-out charging method, where explosives are loaded in sections within the borehole, separated from each other by drilling mud, wooden pads, or other non-explosive materials. This charging method helps reduce the direct impact of explosives on the borehole wall, minimizing damage and thus protecting the lining structure of existing aging railway tunnels.

[0043] The peripheral holes of the spaced explosive charge are also connected to detonating cords for detonation transmission. Detonating cords are a highly efficient and reliable detonation transmission material that can rapidly transfer explosive energy, ensuring that the explosives detonate in a predetermined sequence and time, thereby improving the blasting effect.

[0044] Except for the peripheral holes, other blast holes (such as excavation holes and inner ring holes) adopt continuous charging. Continuous charging means that explosives are continuously loaded from the bottom of the blast hole to the opening. This charging method is simple to implement and can ensure that the explosives are evenly distributed in the blast hole, improving the continuity and uniformity of blasting.

[0045] When conducting blasting operations in a gaseous environment, a forward charging structure is used to ensure safety. Forward charging refers to a charging method where the initiating explosive cartridge is placed at the bottom of the borehole, and the passive explosive cartridges are loaded sequentially upwards. This charging method reduces the possibility of flame generation and lowers the risk of gas and coal dust explosions.

[0046] The use of spaced-charge peripheral holes and detonating cords ensures that the explosives detonate in a predetermined sequence and time, creating a smooth blasting surface and reducing over-excavation and under-excavation. Continuously charged holes ensure uniform distribution of explosives within the borehole, improving the continuity and uniformity of blasting and thus enhancing the overall blasting effect. Spaced-charge peripheral holes reduce the direct impact of explosives on the borehole walls, minimizing damage and protecting the structural safety of existing aging railway tunnels. In gas-filled environments, the use of forward-charging structures reduces the likelihood of flame generation, lowers the risk of gas and coal dust explosions, and improves construction safety. A well-designed charging structure and detonation method reduce explosive usage and construction time, lowering construction costs and optimizing resource allocation.

[0047] According to one embodiment of the present invention, the charge amount per slotted hole and auxiliary hole, and the charge amount per section for single-stage detonation are determined according to the blasting vibration velocity control requirements, while the charge amount per peripheral hole is adjusted according to the borehole spacing, minimum resistance line, and linear charge density.

[0048] In one embodiment of the present invention, the charge amount per hole is one of the key parameters in blasting operations. According to an embodiment of the present invention, the charge amount per hole is determined based on the blasting vibration velocity control value. This means that before blasting operations, detailed vibration monitoring and analysis of the blasting area are required to determine the permissible vibration level. Then, through experimental blasting or numerical simulation, a suitable charge amount that ensures the blasting effect while meeting vibration control requirements is found.

[0049] The charge amount in the peripheral holes is crucial for controlling the shape and size of the excavated cross-section after blasting. According to embodiments of the present invention, the charge amount in the peripheral holes is adjusted based on the borehole spacing, the resistance line, and the linear charge density. The borehole spacing determines the degree of interaction between adjacent boreholes, the resistance line reflects the stress state of the rock during blasting, and the linear charge density determines the amount of explosive per unit length of borehole. By comprehensively considering these factors, the charge amount in the peripheral holes can be precisely adjusted to achieve the desired blasting effect.

[0050] By precisely controlling the charge amount in the cut holes, auxiliary holes, and peripheral holes, this invention significantly reduces the impact of blasting operations on the surrounding environment and minimizes potential vibration damage to existing structures (such as old railway tunnels), thereby improving the safety of blasting operations. By rationally adjusting the charge amount in the peripheral holes, this invention ensures that the flatness of the excavated section and the degree of rock fragmentation after blasting meet design requirements, improving blasting effectiveness, reducing over-excavation and under-excavation, and lowering construction costs. Precise charge control helps reduce the number of test blasts and commissioning time, improving construction efficiency. Simultaneously, by optimizing blasting parameters, the blasting cycle can be shortened, accelerating construction progress. This invention, through strict control of blasting vibration, reduces interference and damage to the surrounding environment, embodying an environmentally friendly design philosophy. This is of great significance for protecting the ecological environment and promoting sustainable development.

[0051] According to one embodiment of the present invention, the detonation network is a series method, with external tubes connected in a network, each group of detonating cords having no more than 20 cords, and the detonation station is located in a safe position.

[0052] In one embodiment of the invention, the detonation network adopts a series method and is designed as an external pipe network.

[0053] The detonation network is connected in series. The series method has the advantages of simple operation and easy inspection, making it particularly suitable for the blasting scenario in this embodiment.

[0054] The number of detonating cords in each group shall not exceed 20. This limitation is to ensure the reliability and safety of the detonation network and to avoid excessive detonating cords leading to complex connections or increased risk of misfires. The detonating cords are connected by specialized connecting elements to ensure the smooth propagation of the detonation wave.

[0055] The detonation network is designed as an external pipe network, meaning the detonating cords are connected and arranged outside the borehole. This design facilitates construction and operation, and also helps improve the reliability of the detonation network.

[0056] The detonation station is located in a safe position. This design is intended to ensure the safety of the detonation personnel and prevent injury during the blasting process.

[0057] Connecting the detonation network in series and limiting the number of detonating cords in each group reduces connection complexity and the risk of misfires, thereby improving the reliability of the detonation network. Placing the detonation station in a safe location ensures the safety of detonation operators, preventing injury during blasting and reducing accident risks. The external pipe network design facilitates construction and operation, reducing construction difficulty and time costs. It also helps improve the efficiency and accuracy of blasting operations. The technical solution in this embodiment is applicable to various blasting scenarios and conditions, exhibiting high flexibility and adaptability. By adjusting the number and connection method of detonating cords, blasting requirements of different scales and complexities can be met.

[0058] According to one embodiment of the present invention, the size of the rock fragments after blasting is controlled to be between 5 and 70 centimeters. If the size is abnormal, the spacing between blast holes and the amount of explosive charge per hole are adjusted.

[0059] In one embodiment of the invention, the size of the blasted rock fragments is strictly controlled within the range of 5 to 70 centimeters. This setting is intended to meet the requirements of subsequent mechanical or manual removal of the debris, ensuring construction efficiency and safety.

[0060] If the size of the blasted rock fragments is abnormal (too large or too small), the hole spacing should be adjusted first. Hole spacing is one of the key factors affecting the blasting effect. By properly adjusting the hole spacing, the stress wave superposition effect between adjacent holes can be changed, thereby affecting the degree of rock fragmentation and the distribution of rock fragments.

[0061] Besides adjusting the spacing between blast holes, the size of the rock fragments after blasting can also be controlled by adjusting the charge per hole. The amount of charge directly affects the energy generated by the explosion and the propagation of stress waves, thus affecting the rock fragmentation effect. When the fragments are too large, the charge can be increased appropriately to improve the fragmentation effect; when the fragments are too small, the charge can be reduced to avoid over-fragmentation.

[0062] Before blasting operations, a detailed site survey and geological analysis are conducted to determine the appropriate borehole spacing and charge quantity. After blasting, the size of the rock fragments is monitored and statistically analyzed in real time, and blasting parameters are adjusted promptly based on the monitoring results to form a closed-loop control system.

[0063] By adjusting the spacing between blast holes and the charge amount per hole, the size of the blasted rock fragments can be precisely controlled, maintaining them within the range of 5 to 70 centimeters to meet the requirements of subsequent construction. Precisely controlled rock fragment size facilitates efficient mechanical or manual muck removal operations, reducing additional processing time and costs caused by fragments that are too large or too small. Reasonable blasting parameter settings and fragment size control help reduce safety risks during blasting operations, minimizing the potential threats to personnel and equipment from flyrock and shockwaves.

[0064] According to one embodiment of the present invention, the reserved deformation amount is dynamically adjusted based on the monitoring and measurement results of the surrounding rock, while the excavation profile is expanded by 5 centimeters compared to the design.

[0065] In one embodiment of the present invention, during tunnel construction, the deformation of the surrounding rock is monitored in real time using surrounding rock monitoring and measurement technology. Based on the monitoring and measurement results, the stability of the surrounding rock and the stress state of the support structure are analyzed. Based on the analysis results, the reserved deformation amount is dynamically adjusted to adapt to the actual deformation of the surrounding rock. The adjustment of the reserved deformation amount aims to ensure that the support structure neither infringes on the limits nor exceeds the limits after the deformation stabilizes.

[0066] Based on the designed excavation outline, and taking into account factors such as construction errors and surrounding rock deformation, the excavation outline is enlarged by 5 centimeters. This enlargement is intended to offset potential over-excavation and under-excavation during actual excavation, as well as layout errors, ensuring that the final tunnel cross-section meets the design requirements.

[0067] By dynamically adjusting the reserved deformation amount, the stability of the support structure can be ensured during deformation, reducing the risk of surrounding rock instability and collapse. Expanding the excavation outline helps reduce construction difficulties and safety risks caused by over-excavation and under-excavation. Dynamically adjusting the reserved deformation amount based on surrounding rock monitoring measurements allows for a more rational design of the support structure, reducing unnecessary material waste and cost.

[0068] Meanwhile, optimizing the design of the support structure can improve the overall stability and durability of the tunnel. Dynamically adjusting the allowable deformation and determining a reasonable excavation profile helps reduce the number of adjustments and rework during construction, thereby improving construction efficiency. Furthermore, real-time monitoring and analysis of surrounding rock deformation allows for the timely detection of potential safety hazards and the implementation of appropriate measures, preventing construction delays and accidents. Strict monitoring and measurement of the surrounding rock and dynamic adjustment of the allowable deformation enable precise control over tunnel construction quality. This helps ensure that the final tunnel cross-section meets design requirements, improving the overall quality and reliability of the tunnel.

[0069] According to one embodiment of the present invention, during the test blasting, the over-excavation and under-excavation, the residual hole preservation rate and the cycle time are recorded, and the blasting parameters are optimized in combination with geological sketch data.

[0070] In one embodiment of the present invention, during test blasting, the over-excavation and under-excavation after each blast are recorded in detail, and the blasting parameters are continuously optimized and adjusted based on the blasting effect. Over-excavation refers to the portion where the actual excavated cross-section is larger than the designed cross-section, while under-excavation refers to the portion where the actual excavated cross-section is smaller than the designed cross-section. Recording this data helps to evaluate the blasting effect and provides a basis for subsequent parameter adjustments.

[0071] The borehole retention rate refers to the ratio of the length of the unexploded portion remaining on the borehole wall after blasting to the total length of the borehole. It is a crucial indicator for evaluating blasting effectiveness, reflecting the efficiency of explosive energy utilization and the degree of rock fragmentation. Accurate recording of the borehole retention rate during test blasts helps assess the suitability of explosive selection and blasting parameters.

[0072] Cycle time refers to the time interval between the end of one blast and the start of the next, including the time for each stage such as charging, wiring, detonation, smoke removal, muck removal, and support. Accurate recording of cycle time during test blasts helps analyze construction efficiency and provides a basis for subsequent construction planning.

[0073] During the test blasting, photographic or video recording equipment is used to record the blasting site in real time, obtain image data, and combine the image data to conduct geological sketching.

[0074] A detailed analysis of the video data was conducted to observe the rock fragmentation and the preservation of blast hole traces during the blasting process, in order to further evaluate the blasting effect.

[0075] Based on the data of over- and under-excavation, residual hole preservation rate and cycle time recorded during the test blasting, as well as the analysis results of the image data, the blasting parameters were optimized and adjusted.

[0076] Parameter optimization may include adjusting the spacing between blast holes, the depth of blast holes, the amount of explosive charge per hole, the amount of explosive charge per single detonation, and the detonation sequence, in order to improve blasting effect, reduce over-excavation and under-excavation, and improve construction efficiency and quality.

[0077] By recording and analyzing data during test blasting, problems with blasting effects can be identified in a timely manner, such as excessive over-excavation, severe under-excavation, or insufficient residual hole retention. Optimizing and adjusting blasting parameters to address these issues can significantly improve blasting effects, resulting in more uniform rock fragmentation and reducing over-excavation and under-excavation. Recording cycle times and analyzing bottlenecks in the construction process can identify key factors affecting construction efficiency. Optimizing these factors, such as improving the charge structure and optimizing the detonation sequence, can shorten cycle times and improve construction efficiency. Recording and analyzing data during test blasting, along with meticulous observation of imagery, allows for precise control of construction quality. This helps ensure that each blast achieves the expected results, reducing rework and repair work caused by poor blasting performance. The implementation of this technical solution promotes innovation and development in blasting technology. In-depth analysis of data and continuous optimization of parameters during test blasting can drive blasting technology towards greater efficiency, environmental friendliness, and safety.

[0078] According to one embodiment of the present invention, misfire treatment includes re-detonation, parallel hole blasting, mechanical cleaning, or detonation.

[0079] In one embodiment of the present invention, handling misfires is a crucial task that directly relates to the safety and efficiency of blasting operations.

[0080] If a misfire is caused by an undamaged detonation network or an unchanged minimum resistance line, a re-detonation may be chosen. Before re-detonation, ensure all personnel have been evacuated to a safe area and the perimeter is reset. Inspect the detonation network for integrity, ensuring there is no damage or breakage. Reconnect the detonation network and detonate according to standard detonation requirements.

[0081] When the location of a misfire is clearly defined and surrounding conditions permit, a parallel hole can be drilled at a distance of no less than 10 times the diameter of the borehole from the misfire opening. Explosives are loaded into the parallel hole and detonated to ignite the explosives in the misfire. The parameters for parallel hole blasting should be determined by professional blasting engineers.

[0082] In some cases, mechanical equipment (such as excavators, loaders, etc.) can be used to clear misfired explosives. Before mechanical removal, it must be ensured that the misfired explosive or the explosive has been deactivated and that there are no hazards in the surrounding area. During mechanical removal, care should be taken to avoid damaging the surrounding rocks or structures.

[0083] Detonation is achieved by placing an exposed explosive charge or other detonator near the misfire to ignite the explosive inside. Before detonation, it must be ensured that all relevant personnel have been evacuated to a safe area and the perimeter security has been reset. During detonation, the amount of explosives must be strictly controlled to avoid causing excessive damage to surrounding rocks or structures.

[0084] Misfires can be safely handled through methods such as re-detonation, parallel hole blasting, mechanical clearing, or detonation, preventing them from becoming potential safety hazards. During the handling of misfires, strict adherence to safety regulations and operating procedures is crucial to ensure the safety of personnel and equipment. Implementing misfire handling techniques ensures the smooth progress of blasting operations, avoiding downtime or rework caused by misfires. Optimizing the misfire handling process and methods can shorten handling time and improve blasting efficiency. Implementing misfire handling techniques can prevent economic losses such as equipment damage and personnel injuries caused by misfires. By rationally selecting and applying misfire handling methods, handling costs can be reduced, and economic benefits improved.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A controlled blasting construction method for soft rock tunnels passing close to existing old railway tunnels, characterized in that, Includes the following steps: The partial bench excavation method is selected according to the surrounding rock grade. For Grade IV surrounding rock, the two-bench method is used, with the upper bench height being 6 to 8 meters, the bench length being 40 to 50 meters, and the cycle advance being 3 arch frame spacings. For Grade V surrounding rock, the three-bench method is used, with each bench height being about one-third of the design height, the upper bench height being 3 to 5 meters, the bench length being 4 to 6 meters, and the cycle advance being 2 arch frame spacings. During the excavation process, the reserved deformation amount is dynamically adjusted according to the monitoring and measurement results of the surrounding rock. The reserved amount is 8 to 12 cm for Class IV surrounding rock and 12 to 17 cm for Class V surrounding rock. At the same time, the excavation outline is 5 cm larger than the design. The blast holes are arranged in a ring pattern on the upper step and linearly on the middle and lower steps. The spacing between the peripheral holes is 0.3 to 0.5 meters, the thickness of the light blast layer is 1.25 times the spacing between the peripheral holes, the resistance line of the auxiliary holes is 0.6 to 1 meter, and the spacing between the blast holes is 1 to 2 times the resistance line. When the hole depth is less than or equal to 3 meters, the slope of the external insertion angle of the peripheral holes is 5 cm / m, and when the hole depth is greater than 3 meters, it is 3 cm / m. The excavation method is designed according to the surrounding rock level. For level 5 surrounding rock, a single-stage wedge excavation is adopted with an excavation angle of 60 to 75 degrees. For level 4 and above surrounding rock, a two-stage or compound wedge excavation is adopted, and the excavation area is arranged in the middle and lower part of the excavation section. The decoupled charge structure was determined through numerical simulation. The decoupling coefficient of the peripheral holes was 0.60, and the decoupling coefficient of other holes was less than or equal to 0.

76. The linear charge density of the peripheral holes was 0.1 to 0.2 kg / m. All boreholes adopted a reverse charge structure. The blasting vibration velocity is calculated using the Sadovsky formula to control the maximum amount of explosive initiation in a single stage. High-pressure air is used to clean the blast holes, and after charging the explosives, the blast holes are filled with blast mud. The plugging length of the peripheral holes is greater than or equal to 0.3 meters, and the plugging length of the other holes is greater than or equal to 0.5 meters. The detonation sequence is set as follows: slotting hole, widening hole, excavation hole, inner ring hole, peripheral hole, and bottom plate hole. Digital electronic detonators are used for segmented detonation. The peripheral holes are detonated simultaneously. When control is required, the number of simultaneous detonations is not less than 5, and the detonation time difference between each segment is less than 25 milliseconds. The detonation interval between each stage of the slotting hole is 50 milliseconds. Each stage of the slotting hole is detonated simultaneously, and subsequent blasting holes are arranged segment by segment. The detonation interval from the start of the gas tunnel to the last segment does not exceed 130 milliseconds. The interval for the surrounding rock section can generally be delayed to 200-300 milliseconds. Set up a warning zone, place the detonation station in a safe location, and ventilate for 15 minutes after detonation; Real-time monitoring of existing tunnel lining displacement, settlement and cracks; monitoring of blasting vibration velocity during blasting. Test blasting cycles are conducted, recording the charge amount per hole, hole spacing, number of holes, and cycle advance parameters. The blasting parameters are continuously optimized and adjusted based on the blasting effect.

2. The controlled blasting construction method for soft rock tunnels passing close to existing old railway tunnels according to claim 1, characterized in that, In the two-step method, the cyclic advance of the lower step is increased by the spacing of one arch frame compared to the upper step. In the three-step method, the cyclic advance of the middle and lower steps is increased by the spacing of one arch frame compared to the upper step, and the two sides are staggered by 2 to 3 meters.

3. The controlled blasting construction method for soft rock tunnels passing close to existing old railway tunnels according to claim 1, characterized in that, The borehole diameter is 42 mm, the bottom of the peripheral hole and the auxiliary hole are located on the same vertical plane, and the slotting hole and the enlarged slotting hole are deepened by 10 to 20 cm.

4. The controlled blasting construction method for soft rock tunnels passing close to existing old railway tunnels according to claim 1, characterized in that, In the decoupled charge structure, the peripheral holes use small explosive cartridges, are spaced out and connected to detonating cords for detonation transmission, while other holes use continuous charges. All holes use a reverse charge structure, and a forward charge structure is used in a gas environment.

5. The controlled blasting construction method for soft rock tunnels passing close to existing old railway tunnels according to claim 1, characterized in that, The charge amount per slotted hole and auxiliary hole, and the charge amount for a single-stage initiation are determined according to the blasting vibration velocity control requirements. The charge amount per peripheral hole is adjusted according to the borehole spacing, minimum resistance line, and linear charge density.

6. The controlled blasting construction method for soft rock tunnels passing close to existing old railway tunnels according to claim 1, characterized in that, The detonation network is a series method, with external tubes connected together. Each group of detonating cords has no more than 20 cords, and the detonation station is located in a safe position.

7. The controlled blasting construction method for soft rock tunnels passing close to existing old railway tunnels according to claim 1, characterized in that, The size of the blasted rock fragments is controlled between 5 and 70 centimeters. If the size is abnormal, the spacing between the blast holes and the amount of explosive charge per hole are adjusted.

8. The controlled blasting construction method for soft rock tunnels passing close to existing old railway tunnels according to claim 1, characterized in that, The reserved deformation amount is dynamically adjusted based on the monitoring and measurement results of the surrounding rock, and the excavation outline is expanded by 5 centimeters compared with the design.

9. The controlled blasting construction method for soft rock tunnels passing close to existing old railway tunnels according to claim 1, characterized in that, During the test blasting, the over-excavation and under-excavation, the residual hole preservation rate, and the cycle time were recorded, and the blasting parameters were optimized in combination with geological sketch data.

10. The controlled blasting construction method for soft rock tunnels passing close to existing old railway tunnels according to claim 1, characterized in that, The handling of misfires includes re-detonation, parallel hole blasting, mechanical cleaning, or detonation.

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