A blasting construction method for controlling vibration influence of a subway tunnel in a complex urban environment

Abstract

The application provides a blasting construction method for controlling vibration influence of a subway tunnel in a complex urban environment, comprising: determining blasting parameters based on vibration monitoring feedback; performing blast hole positioning, drilling, hole cleaning, charging and initiation network connection according to the blasting parameters; performing blasting excavation in a step-by-step excavation manner; continuously performing vibration monitoring during the blasting process, and adjusting subsequent blasting parameters or initiation delay in real time according to the monitoring data. First, the blasting parameters are optimized through trial blasting calculation and vibration monitoring, thereby solving the problem that the traditional method is difficult to determine the parameters in advance, leading to excessive vibration. Secondly, in combination with double-side-wall drift method blasting, the free surface of each blasting is controlled, the vibration and damage risk in large-section excavation are relieved, the monitoring points are arranged, the blasting parameters are dynamically optimized, the scheme is adjusted in real time to cope with the changes of the site conditions, the safety of the surrounding buildings and underground facilities is effectively protected, and the economic and social benefits of the construction are improved.

Description

Technical Field

[0001] This invention relates to the technical field of tunnel engineering, and in particular to a blasting construction method for controlling vibration in subway tunnels under complex urban environments. Background Technology

[0002] Against the backdrop of rapid urbanization, the drill-and-blast method is commonly used in the construction of subway tunnels in mountainous cities. However, urban environments are characterized by dense buildings, complex underground pipelines, and variable geological conditions. Especially when tunnels are near historical buildings, high-rise residential buildings, or important public facilities, the vibration waves generated by blasting operations can easily propagate and amplify through the soil and rock. This vibration can not only cause structural damage such as wall cracking and uneven foundation settlement in surrounding buildings, significantly increasing the cost of later repairs and maintenance, but also potentially cause a chain reaction of problems such as underground pipeline rupture and damage to transportation facilities. At the same time, repeated blasting vibrations accompanied by strong noise continuously disrupt the normal lives of residents, easily triggering public anxiety and social conflicts, leading to increased difficulty in project coordination and a higher risk of project delays. Furthermore, under special geological conditions such as weak surrounding rock or fractured strata, traditional blasting methods struggle to accurately control vibration intensity, further exacerbating the safety threat to sensitive targets. Therefore, how to achieve dynamic monitoring and adaptive control of blasting vibrations in complex urban environments has become a core challenge in ensuring the safety of subway tunnel construction and reducing social impact. Summary of the Invention

[0003] The purpose of this invention is to provide a blasting construction method for controlling vibration in subway tunnels under complex urban environments, so as to solve at least some of the above-mentioned problems.

[0004] This invention provides a blasting construction method for controlling vibration in subway tunnels under complex urban environments, comprising: S1. Determine blasting parameters based on vibration monitoring feedback, including peripheral hole smooth blasting parameters, auxiliary hole blasting parameters, and bottom hole blasting parameters; S2. Based on the blasting parameters, perform borehole positioning, drilling, hole cleaning, charging, and detonation network connection. S3. Blasting excavation is carried out using a step-by-step excavation method, wherein the step-by-step excavation method is the double-side-wall pilot tunnel method; S4. Vibration monitoring is continuously performed during the blasting process, and subsequent blasting parameters or detonation delay are adjusted in real time based on the monitoring data to form a closed-loop adaptive control.

[0005] Furthermore, step S1 includes: S11. Set preset blasting parameters; S12. Vibration monitoring points are set up in the blast source area, sensitive target area and intermediate transition area, and the surrounding rock parameters of the area to be blasted are measured. S13. Conduct test blasting using smooth blasting technology, and perform safety verification based on vibration monitoring data from the test blasting and the surrounding rock parameters. S14. If the verification result is safe, the preset blasting parameter is determined as the candidate blasting parameter; if the verification result is unsafe, the preset blasting parameter is adjusted and step S13 is repeated until the verification result is safe, and the candidate blasting parameter is obtained. S15. Optimize and adjust the candidate blasting parameters based on the vibration monitoring data and surrounding rock parameters to obtain the actual blasting parameters; S16. Perform subsequent blasting operations based on the actual blasting parameters.

[0006] Furthermore, the smooth blasting parameters for the peripheral holes include the thickness of the smooth blasting layer, the density coefficient, the blast hole depth, the charge per hole, the diameter of the peripheral holes, and the spacing between the peripheral holes; wherein, the diameter of the peripheral holes is 32-50mm, and the spacing between the peripheral holes is calculated using the following formula:

[0007] Where E is the hole spacing in meters; W1 is the minimum resistance line in meters; and m is an empirical coefficient, ranging from 0.8 to 1.2. The density coefficient of the surrounding smooth blasting zone is calculated using the following formula: K=E / W2 Where K is the density coefficient, E is the spacing between the surrounding holes, and W2 is the thickness of the light burst layer.

[0008] Furthermore, the auxiliary hole spacing in the auxiliary hole blasting parameters satisfies: In a hard, monolithic rock environment, the spacing D of the auxiliary holes satisfies: 25d≦D≦30d; In a soft, fractured rock environment, the auxiliary hole spacing D satisfies: 45d≦D≦55d; Where D is the spacing between auxiliary holes and d is the diameter of the auxiliary holes.

[0009] Furthermore, the bottom hole spacing in the bottom hole blasting parameters is 0.4m-0.7m, the bottom hole opening in the bottom hole blasting zone is 0.1m-0.2m higher than the roadway floor, and the bottom of the bottom hole in the bottom hole blasting zone is 0.1m-0.2m lower than the floor.

[0010] Furthermore, in step S2: The first charging structure is used to charge the explosive in the peripheral hole. The first charging structure includes multiple explosive cartridges arranged at intervals along the axial direction of the peripheral hole, and a detonating cord passing through the multiple explosive cartridges, so as to achieve decoupled interval charging. A second charging structure is used to charge the explosive in the auxiliary hole and the bottom hole. The second charging structure includes explosive filling the borehole and an electronic detonator set at the bottom of the borehole. The explosive and the electronic detonator are connected by lead wires.

[0011] Furthermore, there are multiple electronic detonators, each with a different delay time, so that each borehole is detonated sequentially in a preset order.

[0012] Furthermore, in step S4: The vibration monitoring data includes the vibration velocity at the explosion source point, the vibration velocity of the sensitive target, and the vibration frequency. When the monitoring data exceeds the preset safety threshold, the delay time of the electronic detonator in the undetonated blast hole is automatically or manually adjusted, and / or the charge amount and blast hole spacing of the subsequent blasting cycle are adjusted.

[0013] Furthermore, in step S3, the step-by-step blasting excavation using the double-sidewall pilot tunnel method specifically includes: S31. First, two upper bench sidewall pilot tunnels are excavated on both sides of the tunnel arch, and then the middle pilot tunnel of the upper bench is excavated. S32. Following the same step-by-step approach as the upper step, excavate the middle step and the lower step in sequence.

[0014] Furthermore, in the distributed blasting excavation, the intermediate pilot pit of the lower bench is constructed using vertical drilling, employing the underground shallow-hole bench blasting method from top to bottom.

[0015] The beneficial effects of this plan are as follows: This proposed blasting method for controlling vibration in subway tunnels under complex urban environments firstly optimizes blasting parameters through trial blasting calculations and vibration monitoring, thus solving the problem of traditional methods' difficulty in pre-determining parameters and resulting in excessive vibration. Secondly, by combining blasting with a double-sidewall pilot tunnel method, the free face of each blast is controlled, mitigating the vibration and damage risks during large-section excavation. Furthermore, by deploying monitoring points and dynamically optimizing blasting parameters, the method is adjusted in real time to address changes in site conditions. This technical solution effectively protects the safety of surrounding buildings and underground facilities, improving both the economic and social benefits of construction.

[0016] By determining blasting parameters based on vibration monitoring, employing a double-side-wall pilot tunnel method for step-by-step excavation, and continuously monitoring and dynamically adjusting blasting parameters and detonation delay during the blasting process to form a closed-loop adaptive control, the intensity of blasting vibration can be effectively controlled. This avoids excessive vibration from damaging surrounding buildings, pipelines, and other sensitive targets, solving the problem of difficult-to-control blasting vibration in subway tunnels in complex urban environments. It has the advantages of achieving dynamic adaptive control of blasting vibration, effectively reducing the vibration impact of blasting operations on sensitive targets around the city, ensuring construction safety, and reducing engineering risks and social impact. Attached Figure Description

[0017] Figure 1 This is a flowchart of the steps of the blasting construction method for controlling vibration in subway tunnels under complex urban environments provided by the present invention.

[0018] Figure 2 This is a flowchart of the test blasting construction organization provided by the present invention.

[0019] Figure 3 This is a schematic diagram of the planar warning system for openings provided by the present invention.

[0020] Figure 4 This is a schematic diagram of the peripheral hole charging structure provided by the present invention.

[0021] Figure 5 This is a schematic diagram of the explosive charging structure provided by the present invention.

[0022] Figure 6 This is a cross-sectional view and construction sequence diagram of the main body provided by the present invention.

[0023] Figure 7 This is a schematic diagram of the station excavation sequence provided by the present invention.

[0024] Figure 8 This invention provides a main cross-section borehole design and a detonator delay time network design diagram.

[0025] Figure 9 This is a schematic diagram of the excavation method and hole layout provided by the present invention.

[0026] Figure 10 This is a schematic diagram of the drilling method and hole layout provided by the present invention.

[0027] Figure 11 This is a schematic diagram of the detonation network provided by the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0029] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "front," "rear," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention; the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance; furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "joined" should be interpreted broadly, for example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or they can refer to the internal communication of two components. For those skilled in the art, the specific meaning of the terms in this invention can be understood according to the specific circumstances.

[0030] When traditional urban subway tunnels in mountainous areas are constructed using the drill-and-blast method, the complex urban environment, especially when they are near dense buildings, causes problems such as vibration and noise during the blasting process. This not only directly leads to a high risk of damage to surrounding buildings and underground facilities and high repair and maintenance costs, but may also cause adverse social impacts such as public concern and dissatisfaction.

[0031] In response, this application proposes a blasting construction method for controlling vibration in subway tunnels under complex urban environments, comprising: S1. Determine blasting parameters based on vibration monitoring feedback. These blasting parameters include smooth blasting parameters for peripheral holes, blasting parameters for auxiliary holes, and blasting parameters for bottom holes. Before actual construction, a small-scale pre-blasting can be carried out, and preliminary vibration data can be obtained through simple vibration measurement equipment. Based on this data, the initially set blasting parameters can be adjusted to better suit the actual site conditions.

[0032] Specifically, in step S1, the method for determining blasting parameters based on vibration monitoring feedback includes the following steps: S11, Set preset blasting parameters.

[0033] Pre-set blasting parameters refer to the parameters of the blasting scheme initially determined before the formal blasting operation, based on information such as engineering design requirements, geological survey reports, sensitivity of the surrounding environment, and relevant blasting specifications. These parameters typically include, but are not limited to, single-hole charge amount, hole pattern parameters (hole spacing, row spacing), initiation method, and delay time. Their purpose is to provide an initial reference benchmark for subsequent test blasts, allowing for iterative optimization through actual monitoring and verification.

[0034] S12. Vibration monitoring points are set up in the blast source area, sensitive target area and intermediate transition area, and the surrounding rock parameters of the area to be blasted are measured.

[0035] The deployment of vibration monitoring points aims to comprehensively acquire the propagation characteristics and attenuation patterns of blasting vibrations in different key areas. Monitoring points in the blast source area are used to directly measure the original vibration intensity generated by the blast; monitoring points in sensitive target areas (such as buildings, underground pipelines, etc.) are used to assess the impact of the blast on surrounding structures; and monitoring points in intermediate transition areas are used to understand the propagation path and attenuation of vibrations in different media. The determination of surrounding rock parameters, such as rock strength, integrity, and joint and fracture development, is an important basis for evaluating the blasting effect and vibration propagation characteristics. These parameters can be obtained through geological surveys, borehole sampling, laboratory tests, or field tests (such as wave velocity testing). This data provides fundamental support for subsequent safety calculations and parameter optimization.

[0036] S13. Conduct test blasting using smooth blasting technology, and perform safety verification based on vibration monitoring data from the test blasting and the surrounding rock parameters.

[0037] Test blasting is a small-scale, controlled blasting experiment conducted before formal blasting. Its purpose is to verify the rationality and safety of the preset blasting parameters. Test blasting typically begins with a small amount of explosive, gradually increasing the amount to test its impact on vibration. Smooth blasting techniques are used to maintain a stable excavation profile and reduce vibration impact. Safety calculations are based on vibration monitoring data obtained from test blasting (such as peak velocity and vibration frequency) and measured surrounding rock parameters, combined with relevant blasting safety regulations and structural seismic standards, to assess whether the impact of the blasting on the surrounding environment and structure is within acceptable limits.

[0038] In S1, the safety calculation should be performed according to the relevant requirements of the "Safety Regulations for Blasting" (GB6722-2014) to calculate the permissible speed of blasting vibration and determine the safety distance of individual flying rocks and the minimum safe distance of air shock waves to personnel.

[0039] The formula for calculating the permissible velocity of blasting vibration is as follows: Equation (1); In formula (1): V is the safe allowable particle velocity at the location of the protected object (cm / s); K and a are coefficients and attenuation indexes related to the terrain and geological conditions between the blasting point and the protected object; R is the distance from the blasting point to the protected object (m); Q is the maximum charge for a single detonation (kg). The following is an example of subway tunnel construction in a certain city. The shortest straight-line distance between the main body of the station and the nearest building is 53.094m, and the upper distance is 11.46m, which gives Rmin as 61.334m. According to formula (1), the allowable velocity of blasting vibration is verified. According to the "Safety Regulations for Blasting" (GB6722-2014), K is taken as 200, a as 1.65, Rmin = 64.55m, Q = 12kg, and the data in the above formula is substituted into formula (1), resulting in V as 0.81cm / s. That is, the seismic wave vibration velocity V caused by blasting construction in the nearest blasting area is ≤0.81cm / s, which meets the relevant provisions and requirements of the "Safety Regulations for Blasting" (GB6722-2014) for general civil buildings (underground shallow hole blasting f = 60Hz~300Hz, general civil buildings V = 2.5-3.0cm / s), referring to this standard. The design blasting vibration velocity V-0.81cm / s is less than the permissible standard for blasting vibration safety in the "Blasting Safety Regulations" (GB6722-2014), so the design parameters of this scheme are relatively reasonable.

[0040] Specifically, the safety calculations for the blasting area and each protected object are shown in Table 1: Table 1 Safety Calculation Table for Each Protected Object

[0041] The safe distance for individual fly rocks during tunnel blasting can be determined using the "Safety Regulations for Blasting" (GB6722-2014). It is usually 300m for non-small hole blasting of horizontal tunnels, and usually 400m for small hole or secondary blasting. Specifically, to ensure the safety of personnel during blasting operations, a safety distance of 300m is set for individual flying rocks.

[0042] The following formula is used for calculation regarding protection against blasting shock waves: Equation (2); Calculate, in equation (2): R k Q represents the minimum safe distance for personnel from the air shockwave; Q is the charge parameter, with a second delay for blasting representing the maximum single charge and a millisecond delay for blasting representing the total charge. Simultaneously, its warning range and requirements must be consistent with the requirements for preventing flying rocks in this case.

[0043] Specifically, the maximum amount of explosive used in a single detonation in this plan is Q = 320 kg. Calculations show that: Calculations show that the blast shockwave inside the tunnel poses a hazard, and the warning range and requirements should be the same as those for rockfall prevention in this case (greater than 300m). Additionally, installing 5-7 soundproof curtains inside the tunnel, which can be lowered during blasting, can further reduce the blast shockwave and noise.

[0044] Preferably, in S1, to prevent flying rocks and impact damage, after ensuring that all machinery and personnel have evacuated outside the tunnel, a protective frame can be set up in front of the tunnel entrance to increase protection.

[0045] Specifically, since blasting takes place underground, the detonation station is usually located outside the tunnel. When the blasting site is deep, the detonation station can be set up inside the tunnel in a short, transverse tunnel or bunker to protect against flying rocks, shock waves, and dust. Before detonation, it is essential to ensure that all machinery and personnel inside the tunnel have been evacuated to a safe area. Two layers of mobile protective frames should be installed in front of the tunnel entrance, with a width and tightness 50cm greater than the entrance to effectively block flying rocks and debris. The frames need to be transported to the entrance by a loader and secured with a trolley to ensure they are tightly fitted against the entrance. Figure 3 As shown, the warning area is set at 200m directly in front of the tunnel entrance and 100m on each side. During the blasting, these areas must be cleared and no personnel or equipment are allowed to stay or operate.

[0046] S14. If the verification result is safe and the effect is ideal, the preset blasting parameters are determined as candidate blasting parameters. If the verification result is unsafe, the preset blasting parameters are adjusted and the test blasting and safety verification steps are repeated until the verification result is safe, and candidate blasting parameters are obtained. This step describes an iterative optimization process. If the safety verification result of the test blasting shows that the vibration level is within the safe threshold, the current preset blasting parameters are confirmed as feasible "candidate blasting parameters". Conversely, if the verification result is unsafe, the preset blasting parameters need to be adjusted, such as reducing the single-hole charge, increasing the hole spacing, optimizing the detonation sequence, or using more refined blasting techniques, and then the test blasting and safety verification are performed again until a parameter combination that meets the safety requirements is found. This iterative process ensures the initial safety of the blasting parameters.

[0047] S15. Based on this, the candidate blasting parameters are optimized and adjusted according to the vibration monitoring data and surrounding rock parameters to obtain the actual blasting parameters. After obtaining safe and reliable candidate blasting parameters, this step aims to further optimize these parameters to improve blasting efficiency and effectiveness while meeting safety requirements. The optimization and adjustment will comprehensively consider the vibration monitoring data of the test blast (not only safety, but also vibration characteristics, attenuation laws, etc.) and surrounding rock parameters, and may involve fine-tuning the charge structure, initiation network, delay time, etc., in order to achieve the best blasting effect (such as good formation, less over-excavation, and less vibration) and economy. The final determined parameters are the "actual blasting parameters" used for subsequent large-scale blasting operations.

[0048] Finally, subsequent blasting operations are performed based on the actual blasting parameters.

[0049] Through the above technical solution, this application effectively addresses the safety risks and efficiency issues caused by improper initial blasting parameter settings in subway tunnel blasting construction in complex urban environments. First, by setting preset parameters and conducting test blasts, combined with multi-area vibration monitoring and surrounding rock parameter safety calculations, the initial safety of the blasting parameters is ensured. Second, through iterative adjustments and optimizations, the final determined actual blasting parameters not only meet safety requirements but also consider blasting efficiency and effectiveness. This closed-loop parameter determination mechanism significantly improves the safety, controllability, and economy of blasting operations, avoids potential hazards caused by blind construction, and provides reliable technical support for subsequent large-scale blasting operations.

[0050] According to the geological survey results, the surrounding rock of the construction passage is classified as Class IV.

[0051] Preferably, in S1, the blasting parameters to be determined for the peripheral smooth blasting zone include the thickness of the smooth blasting layer, the density coefficient, the depth of the blast hole, the charge per hole, the hole diameter, and the hole spacing.

[0052] The borehole diameter can be determined according to the drilling tools used, and is generally selected based on site conditions, rock properties and the capabilities of construction equipment. It is generally 32-50mm. To reduce damage to the surrounding rock, a smaller borehole diameter should be selected. To achieve efficient smooth blasting construction, a 7655 type pneumatic drill with a borehole diameter of 40mm±2mm was selected.

[0053] In practice, the peripheral holes must be drilled on the design outline, slightly outward or upward at 3-5°, with the bottom of the hole located ±100mm outside the design outline to provide conditions for the next drilling step. Furthermore, the boreholes must be kept parallel, with the bottoms on the same plane.

[0054] Hole spacing empirical calculation: Where E is the hole spacing (meters); W1 is the minimum resistance line (meters), i.e., the distance from the smooth hole to the free surface; m: an empirical coefficient, generally taken as 0.8-1.2. In smooth blasting of tunnels or underground caverns, the minimum resistance line is usually taken as 0.8-1.2m. Specifically, the density coefficient K is set to 0.8-1.0, the spacing between peripheral holes is 500-800mm, the advance length is 2.4-2.6m, and the charge per hole for light blasting is q=0.15-0.3kg / m.

[0055] Preferably, in step S1, the blasting parameters of the auxiliary holes and the bottom hole should meet certain principles. The principle for determining the maximum critical spacing of the auxiliary holes is as follows: In a hard, monolithic rock environment, the spacing D of the auxiliary holes satisfies: 25d≦D≦30d; In a soft, fractured rock environment, the auxiliary hole spacing D satisfies: 45d≦D≦55d; Where D is the spacing between auxiliary holes, and d is the diameter of the auxiliary holes. 。

[0056] The spacing between bottom holes is generally 0.4-0.7m. When using dump blasting, a smaller spacing is used for the bottom holes. The opening of the bottom hole should be 0.1-0.2m higher than the floor of the roadway, but the bottom of the hole should be 0.1-0.2m lower than the floor. When using dump blasting, the depth of the blast hole should be increased by about 0.2m. The charge amount in the bottom hole is between that in the cut hole and the auxiliary hole. When using dump blasting, 1-2 additional charge cartridges are added to each hole.

[0057] S2. Based on the blasting parameters, perform borehole positioning, drilling, hole cleaning, charging, and detonation network connection; In S2, the positioning holes should be drilled manually using a hand-held pneumatic drill on a white excavation stand. After the stand is in place, the holes should be drilled manually according to the blast hole layout diagram. The drilling accuracy requirements for the cut holes and peripheral holes are higher than those for other holes, with the opening error controlled within 3cm and 5cm respectively.

[0058] To better control vibrations during smooth blasting, the drillers responsible for drilling must be skilled in operating rock drilling machinery, especially drilling peripheral holes, ensuring that the peripheral holes have accurate external insertion angles (according to the blasting design or a modified design), and that the step at the junction of two blasts is no less than 15cm. Simultaneously, the blast hole depth must be adjusted according to the unevenness of the rock at the hole opening location to ensure that the bottom of the blast holes is on the same plane.

[0059] Before charging, the borehole should be cleaned using a steel-reinforced hook and a small-diameter high-pressure air hose to scrape away and blow away any rock debris. Charging should be done in sections and groups, proceeding from top to bottom according to the charge amount determined in the borehole design drawing, with detonators placed precisely in their designated locations. All boreholes should be plugged with stemming material, with a plug length of at least 20cm.

[0060] Charge structure design: see Figure 4 The explosives are loaded into the peripheral holes using a first charging structure. This first charging structure includes multiple explosive cartridges spaced apart along the axial direction of the peripheral holes, and detonating cords penetrating these cartridges to achieve decoupled, spaced-out charging. Ordinary explosive cartridges are evenly dispersed and detonated using detonating cords. The borehole opening is plugged to a depth of 30-50 cm, while the remaining boreholes use a continuous charging structure. The peripheral hole charging divides the explosives into multiple cartridges, resulting in smaller amounts of explosives detonated each time, thus reducing vibration. Using appropriate borehole sealing materials can effectively reduce explosive waste and decrease vibration and flyrock phenomena.

[0061] The spaced arrangement of the first charge structure effectively reduces the peak pressure of the blast shock wave and prolongs its duration, thereby minimizing the instantaneous impact on the surrounding rock, facilitating the formation of a smooth blast profile, and significantly reducing blast vibration. The detonating cord running through these charge cartridges ensures that all cartridges can be reliably detonated in a predetermined sequence or simultaneously, guaranteeing consistent blasting results.

[0062] See Figure 5 A second charging structure is used to charge the explosives in the auxiliary holes and the bottom hole. This second charging structure includes explosives filling the borehole and an electronic detonator located at the bottom of the borehole. The explosives and the electronic detonator are connected by lead wires. Digital electronic detonators are used for delayed blasting. By setting different delay times, multiple boreholes are detonated sequentially rather than simultaneously. This avoids the superposition of blast waves, achieves a uniform blast distribution, and reduces vibration intensity.

[0063] In this configuration, explosives are filled into the borehole, typically using coupled or partially coupled charges to maximize the explosive energy's impact on the rock. An electronic detonator positioned at the bottom of the borehole provides precise detonation timing control, ensuring the explosive detonates from the bottom up, resulting in more thorough rock fragmentation and better throwing. The explosives and electronic detonator are connected via lead wires, a standard method to ensure reliable transmission of the detonation signal.

[0064] Digital electronic detonators are typically equipped with a real-time monitoring system, which allows for inspection of the detonator settings before blasting and real-time adjustments during construction. If any abnormalities or excessive vibrations are detected, the delay time or blasting sequence can be adjusted immediately to effectively control vibration.

[0065] In S2, medium- and low-velocity explosives are used to reduce the impact and vibration during blasting, because low-velocity explosives have a longer detonation time and release energy relatively slowly.

[0066] Specifically, according to geological data, the tunnels in this project traverse strata without coal seams, gas, or natural gas, thus eliminating the need for permitted blasting materials used in coal mines. To control the impact of blasting on existing structures, this design utilizes medium-to-low detonation velocity explosives, the properties of which are shown in Table 2. Table 2 Explosive Performance Indicators

[0067] In S2, after the explosive charge is loaded into the blast hole, a water hose is used between the explosive charge and the blasting mud. The water in the water hose contains a dust suppressant (water-based agent) to reduce blasting dust and vibration.

[0068] In S2, the detonation sequence is designed as follows: cut-out hole—enlarged slot hole—auxiliary hole—inner ring hole—peripheral hole—bottom plate hole. It should be noted that the cut-out hole, enlarged slot hole, auxiliary hole, and inner ring hole can be categorized as auxiliary holes.

[0069] In S2, detonating cord is used to transmit the detonation in the peripheral holes, or detonators with detonating cord are installed inside the holes (to prevent the detonating cord from breaking the network) to ensure the reliability and accuracy of the detonation.

[0070] Specifically, in the operation of a digital electronic detonator multi-hole detonation network, the charge per hole does not exceed 1.6 kg, and each section of the detonation network connects no more than 6 holes, ensuring that the maximum charge per single detonation does not exceed 9.6 kg. The number of holes detonated in a single operation is limited to 150, with a total charge not exceeding 240 kg. The detonation interval is set at 25 ms, which can be adjusted according to site conditions, with a total blasting time of approximately 625 ms. This time control ensures that the blasting operation is completed in a very short time, minimizing the impact on the environment.

[0071] Specifically, during blasting, the delay time of each detonator is set according to the value marked on the diagram. It can be increased or decreased appropriately according to the blasting site conditions, but it is necessary to ensure that the maximum charge per section is controlled within 12kg.

[0072] Multiple electronic detonators, each with a different delay time, are used to detonate the blast holes sequentially in a pre-set order. This precise timing control effectively avoids the concentrated release of blasting energy and the superposition of vibration waves caused by simultaneous detonation of all blast holes, thus significantly reducing the instantaneous peak vibration velocity generated by the blast. Simultaneously, the sequential detonation method helps optimize the utilization efficiency of blasting energy, resulting in more uniform rock fragmentation, reducing the generation of excessively large rocks, and improving the efficiency and quality of blasting excavation. Combined with the aforementioned vibration monitoring feedback and closed-loop adaptive control, this scheme can more precisely control blasting vibration, ensuring the safety and stability of subway tunnel construction in complex urban environments.

[0073] S3. Blasting excavation is carried out using a step-by-step excavation method, wherein the step-by-step excavation method is the double-side-wall pilot tunnel method; In the double-sided pilot tunnel method, tunnel excavation is not carried out in one go. Instead, two pilot tunnels (i.e., double-sided pilot tunnels) are first excavated on both sides of the tunnel, followed by the gradual excavation of the upper bench, middle bench, and lower bench. Specifically, this can be divided into nine excavation steps. (See...) Figure 6 As shown.

[0074] Specifically, the total blasting length of this project is 221m, with an excavation outline width of approximately 27.74m and a height of approximately 22.66m. The detailed station excavation sequence diagram is as follows: Figure 6 As shown in the figure, 1-9 represent steps 1-9 of the excavation sequence.

[0075] Preferably, in step S3, in the double-sided pilot tunnel method, the pilot tunnel excavation is usually carried out before the main tunnel. The pilot tunnel excavated first plays a shielding and buffering role during the blasting process. The rock mass between the pilot tunnels has an isolation effect, which can effectively absorb and disperse the vibration energy generated by the blasting.

[0076] Preferably, in step S3, the double-side-wall pilot tunnel method reduces the free face of each blast during tunnel excavation by gradually excavating the pilot tunnel and the main tunnel. The larger the free face, the more vibration and flyrock are generated by the blast. By controlling the size and shape of the free face, the direction of blast energy release can be effectively guided, thereby reducing the propagation of blast vibration in unnecessary directions.

[0077] Preferably, in S3, for large-section tunnels, such as... Figure 7 As shown, the upper part (parts 1, 2, and 3) was constructed using mechanical blasting with a small amount of explosives to loosen the blasting, while the middle part (parts 4, 5, and 6) and the lower part (parts 7, 8, and 9) were constructed using controlled blasting.

[0078] Specifically, in the design of blasting boreholes and detonator delay time network for blasting operations, such as Figure 8 As shown, steps 4 and 5 are symmetrical, and steps 7 and 8 are symmetrical. The complete calculation table of blasting parameters for each step is shown in Table 3, including all auxiliary holes. The total usage per cycle for steps 4-9 is 490.2 kg of explosives, 362 detonators, and 325.5 m of detonating cord. The technical and economic indicators for each cross-section are shown in Table 4.

[0079] Table 3 Calculation table of blasting parameters for each step

[0080] Table 4 Technical and economic indicators for each step

[0081] Preferably, in step S3, considering the large number of existing buildings and structures in the vicinity of the city, in order to effectively control the energy release of the explosive, reduce damage to areas outside the design outline, and reduce the risk of blasting vibration and flying rocks, in step 9, vertical drilling can be adopted to carry out the underground shallow hole bench blasting method from top to bottom, depending on the specific site conditions.

[0082] When using the underground shallow-hole bench blasting method, the holes are arranged in a quincunx pattern to effectively disperse the blasting energy and reduce the vibration impact on the surrounding environment.

[0083] Specifically, the excavation method is: a top-down, shallow-hole bench blasting method.

[0084] The area to be blasted each time shall not exceed: length 20.9m, width 11.84m, and height 2.3m; that is, a maximum of 19 rows of blast holes shall be arranged on the long side, and a maximum of 8 blast holes shall be arranged on the wide side, with a step height not exceeding 2.3m; the volume of each blast shall not exceed 569m³. 3 Excavation method and hole layout as follows: Figure 9 , Figure 10 As shown.

[0085] Specifically, using a handheld drill with a diameter of 40mm, the drilling parameters for shallow holes are as follows: (1) Hole diameter: d = 40 mm; (2) Blasting bench height: H = 1.0-2.3m, over-depth h = 0.2m; (3) Hole depth: L = H + h; (4) Chassis resistance line: W = (0.4 - 1)H; (5) Hole spacing: a = (1-2)W; (6) Hole spacing: b=0.86a (7) Sandstone q=0.5kg / m, shale q=0.45kg / m. Adjustments shall be made according to the actual situation during blasting construction and with the written consent of the scheme designer.

[0086] (8) The blockage length L is filled in as (20-30)d (9) Calculation of single-hole charge amount: Q = q × a × b × H Table 5. Parameters for Shallow Hole Step Loosening Blasting in Handheld Drilling Rigs

[0087] Preferably, in step S3, during the construction of the underground shallow-hole bench blasting method, a digital electronic detonator multi-hole initiation network is also used to further reduce vibration.

[0088] Specifically, the blasting network for underground shallow-hole bench blasting construction is as follows: Figure 11 As shown.

[0089] Preferably, in S3, all blasting parameters are not fixed. On-site blasting technicians should continuously optimize the blasting parameters based on the blasting effect and blasting vibration detection data to ensure that the blasting vibration meets safety requirements.

[0090] Preferably, in step S3, the blasting process should meet the quality inspection standards for smooth blasting.

[0091] Among these requirements: Over-excavation and under-excavation: The surrounding rock surface after blasting must be smooth and flat; No under-excavation: Over-excavation must be controlled within the design specifications. Residual blast hole traces: Must be evenly distributed on the excavation surface. The blast hole trace retention rate must be no less than 50%.

[0092] The rock surface between two adjacent holes should be flat, and there should be no obvious blasting cracks in the hole wall.

[0093] The step error between two adjacent holes shall not exceed 150mm.

[0094] In S3, the bottom over- and under-dig control can be achieved by using an I-beam clamped between the platform and the ground (the platform can be pushed forward and unloaded onto the ground with a crossbeam and secured with sleepers; when drilling the bottom plate hole, the pneumatic drill is placed flat on the ground, and the driller only needs to adjust the air volume to make the drilling smooth and ensure good bottom formation).

[0095] S4. Vibration monitoring is continuously performed during the blasting process, and subsequent blasting parameters or detonation delay are adjusted in real time based on the monitoring data to form a closed-loop adaptive control.

[0096] The vibration monitoring data includes the blast source velocity, the vibration velocity of sensitive targets, and the vibration frequency. The blast source velocity refers to the particle vibration velocity measured near the blast hole or blast center within the blasting operation area. Monitoring the blast source velocity directly reflects the intensity of blast energy release and the blasting effect, serving as a crucial basis for evaluating the rationality of blasting parameters. By monitoring the blast source velocity, it is possible to promptly detect whether the blast energy is too high or too low, providing direct feedback for subsequent adjustments to blasting parameters. The sensitive target velocity refers to the particle vibration velocity measured at vibration-sensitive target locations such as buildings, structures, or underground pipelines around the tunnel. Monitoring the sensitive target velocity is a key indicator for ensuring the safety of the surrounding environment, as its value directly relates to the potential damage to surrounding structures caused by the blast. Real-time monitoring of the sensitive target velocity ensures that blasting vibration is controlled within safe limits, preventing damage to surrounding facilities. The vibration frequency refers to the frequency characteristics of the blasting vibration wave. Different vibration frequencies have varying degrees of impact on different structures. For example, low-frequency vibrations may produce a resonance effect on large structures, while high-frequency vibrations may affect small components or precision equipment. Monitoring vibration frequencies helps to more comprehensively assess the hazards of blasting vibrations and provides a scientific basis for taking targeted vibration reduction measures.

[0097] When the monitored data exceeds the preset safety threshold, the system will automatically or manually adjust the delay time of the electronic detonators in the undetonated blast holes, and / or adjust the charge amount and blast hole spacing in subsequent blasting cycles. The preset safety threshold refers to the maximum allowable value of blasting vibration pre-set based on engineering geological conditions, sensitivity of the surrounding environment, relevant standards and specifications, and safety assessment results. This threshold typically includes the upper limit of particle velocity (PPV) and / or vibration frequency. Once the monitored data exceeds this threshold, it indicates that the blasting vibration may pose a potential risk to the surrounding environment, requiring immediate intervention. Automatic or manual adjustment means the system has two operating modes. Automatic adjustment typically uses preset control logic and algorithms to automatically calculate and issue adjustment commands when the monitored data exceeds the limit. Manual adjustment, on the other hand, involves on-site technicians manually modifying the blasting parameters based on experience and judgment when automatic adjustment fails to meet requirements or manual intervention is needed. The combination of these two modes ensures the flexibility and reliability of control. Adjusting the delay time of the electronic detonators in the undetonated blast holes utilizes the precisely adjustable delay function of the electronic detonators. When vibration exceeds limits, the detonation interval between adjacent boreholes can be altered by extending or shortening the delay time of undetonated boreholes, thereby avoiding the superposition effect of vibration waves, reducing the instantaneous maximum explosive charge, and effectively reducing the intensity of blasting vibration. For example, the delay time can be increased to disperse energy, or the delay sequence can be adjusted to optimize the vibration waveform. Adjusting the charge amount in subsequent blasting cycles is an effective means of directly reducing blasting energy release and thus reducing vibration intensity. This can be achieved by reducing the amount of explosive or using low-power explosives. Adjusting the borehole spacing in subsequent blasting cycles affects the distribution and coupling efficiency of blasting energy in the rock mass. When vibration exceeds limits, the borehole spacing can be appropriately increased to reduce the charge density per unit volume of rock mass, thereby reducing blasting vibration.

[0098] By collecting and analyzing three key vibration monitoring data points in real time—the vibration velocity at the blast source point, the vibration velocity of sensitive targets, and the vibration frequency—this application can more comprehensively and accurately grasp the propagation characteristics of blasting vibrations in different areas and their impact on the surrounding environment. When the monitoring data exceeds the preset safety threshold, the system can respond promptly, flexibly adjusting the delay time of the electronic detonators in the undetonated blast holes, as well as the charge amount and blast hole spacing in subsequent blasting cycles, either automatically or manually. This refined parameter adjustment strategy can effectively avoid the superposition effect of vibration waves, reduce the instantaneous maximum detonation charge, and optimize the release and distribution of blasting energy, thereby significantly reducing the intensity of blasting vibrations and ensuring the safety of sensitive targets. Compared to schemes that rely solely on general vibration monitoring and simple parameter adjustments, this application, by introducing vibration frequency, can gain a deeper understanding of the impact mechanism of vibration on different structures, and thus take more targeted vibration reduction measures. This greatly improves the safety, controllability, and adaptability of subway tunnel blasting construction in complex urban environments, achieving more precise and efficient closed-loop adaptive vibration control.

[0099] In summary, this invention, through the implementation of the above technical solutions, achieves the goal of effectively controlling blasting vibration in large-section urban subway tunnels. Firstly, by optimizing blasting parameters through test blasting calculations and vibration monitoring, it solves the problem of excessive vibration caused by the difficulty in pre-determining parameters using traditional methods. Secondly, the use of medium- and low-velocity explosives and a digital electronic detonator delayed blasting structure effectively controls vibration and noise, resolving the problems of vibration and flyrock caused by concentrated energy release. Combining the double-side-wall pilot tunnel method with the underground shallow-hole bench blasting method controls the free surface of each blast, mitigating the vibration and damage risks during large-section excavation. Smooth blasting technology further reduces vibration and ensures accurate excavation contours. By deploying monitoring points and dynamically optimizing blasting parameters, the plan is adjusted in real time to cope with changes in site conditions. Furthermore, the rational design of borehole parameters and detonation sequence ensures uniform energy release, solving the problems caused by unreasonable traditional blasting parameter design. In summary, this invention effectively protects the safety of surrounding buildings and underground facilities, improving the economic and social benefits of construction.

[0100] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A blasting construction method for controlling vibration in subway tunnels under complex urban environments, characterized in that, include: S1. Determine blasting parameters based on vibration monitoring feedback, including peripheral hole smooth blasting parameters, auxiliary hole blasting parameters, and bottom hole blasting parameters; S2. Based on the blasting parameters, perform borehole positioning, drilling, hole cleaning, charging, and detonation network connection. S3. Blasting excavation is carried out using a step-by-step excavation method, wherein the step-by-step excavation method is the double-side-wall pilot tunnel method; S4. Vibration monitoring is continuously performed during the blasting process, and subsequent blasting parameters or detonation delay are adjusted in real time based on the monitoring data to form a closed-loop adaptive control.

2. The blasting construction method for controlling vibration in subway tunnels under complex urban environments according to claim 1, characterized in that, Step S1 includes: S11. Set preset blasting parameters; S12. Vibration monitoring points are set up in the blast source area, sensitive target area and intermediate transition area, and the surrounding rock parameters of the area to be blasted are measured. S13. Conduct test blasting using smooth blasting technology, and perform safety verification based on vibration monitoring data from the test blasting and the surrounding rock parameters. S14. If the verification result is safe, the preset blasting parameter is determined as the candidate blasting parameter; if the verification result is unsafe, the preset blasting parameter is adjusted and step S13 is repeated until the verification result is safe, and the candidate blasting parameter is obtained. S15. Optimize and adjust the candidate blasting parameters based on the vibration monitoring data and surrounding rock parameters to obtain the actual blasting parameters; S16. Perform subsequent blasting operations based on the actual blasting parameters.

3. The blasting construction method for controlling vibration in subway tunnels under complex urban environments according to claim 1, characterized in that, The smooth blasting parameters for the peripheral holes include the thickness of the smooth blasting layer, the density coefficient, the blast hole depth, the charge per hole, the diameter of the peripheral holes, and the spacing between the peripheral holes; wherein, the diameter of the peripheral holes is 32-50mm, and the spacing between the peripheral holes is calculated using the following formula: Where E is the hole spacing in meters; W1 is the minimum resistance line in meters; and m is an empirical coefficient, ranging from 0.8 to 1.

2. The density coefficient of the surrounding smooth blasting zone is calculated using the following formula: K=E / W2 Where K is the density coefficient, E is the spacing between the surrounding holes, and W2 is the thickness of the light burst layer.

4. The blasting construction method for controlling vibration in subway tunnels under complex urban environments according to claim 1, characterized in that, The auxiliary hole spacing in the auxiliary hole blasting parameters satisfies: In a hard, monolithic rock environment, the spacing D of the auxiliary holes satisfies: 25d≦D≦30d; In a soft, fractured rock environment, the auxiliary hole spacing D satisfies: 45d≦D≦55d; Where D is the spacing between auxiliary holes and d is the diameter of the auxiliary holes.

5. The blasting construction method for controlling vibration in subway tunnels under complex urban environments according to claim 1, characterized in that, The bottom hole spacing in the bottom hole blasting parameters is 0.4m-0.7m, the bottom hole opening in the bottom hole blasting zone is 0.1m-0.2m higher than the roadway floor, and the bottom of the bottom hole in the bottom hole blasting zone is 0.1m-0.2m lower than the floor.

6. The blasting construction method for controlling vibration in subway tunnels under complex urban environments according to claim 1, characterized in that, In step S2, The first charging structure is used to charge the explosive in the peripheral hole. The first charging structure includes multiple explosive cartridges arranged at intervals along the axial direction of the peripheral hole, and a detonating cord passing through the multiple explosive cartridges, so as to achieve decoupled interval charging. A second charging structure is used to charge the explosive in the auxiliary hole and the bottom hole. The second charging structure includes explosive filling the borehole and an electronic detonator set at the bottom of the borehole. The explosive and the electronic detonator are connected by lead wires.

7. The blasting construction method for controlling vibration in subway tunnels under complex urban environments according to claim 6, characterized in that, The electronic detonators are multiple, each with a different delay time, so that each blast hole is detonated sequentially in a preset order.

8. The blasting construction method for controlling vibration in subway tunnels under complex urban environments according to claim 7, characterized in that, In step S4: The vibration monitoring data includes the vibration velocity at the explosion source point, the vibration velocity of the sensitive target, and the vibration frequency. When the monitoring data exceeds the preset safety threshold, the delay time of the electronic detonator in the undetonated blast hole is automatically or manually adjusted, and / or the charge amount and blast hole spacing of the subsequent blasting cycle are adjusted.

9. The blasting construction method for controlling vibration in subway tunnels under complex urban environments according to claim 1, characterized in that, Step S3, the step-by-step blasting excavation using the double-sidewall pilot tunnel method, specifically includes: S31. First, two upper bench sidewall pilot tunnels are excavated on both sides of the tunnel arch, and then the middle pilot tunnel of the upper bench is excavated. S32. Following the same step-by-step approach as the upper step, excavate the middle step and the lower step in sequence.

10. The blasting construction method for controlling vibration in subway tunnels under complex urban environments according to claim 9, characterized in that, In distributed blasting excavation, the intermediate pilot pit of the lower bench is constructed using vertical drilling, employing the underground shallow-hole bench blasting method from top to bottom.

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