Efficient foundation pit earthwork blasting construction technology

Abstract

The invention discloses an efficient foundation pit earth-rock blasting construction process which comprises the following steps that S1, a foundation pit blasting cross section is subjected to blasting partition, and the blasting intensity of the middle area is larger than that of the areas on the two sides; s2, surface earthwork is excavated, and a rock surface is trimmed; s3, fly stone protection is arranged in the blasting area; s4, the foundation pit is sectioned and layered, all the layers on the upper portion of the foundation pit are subjected to middle blasting and then subjected to two-side blasting, and all the layers on the lower portion of the foundation pit are subjected to two-side blasting and then subjected to middle blasting; and S5, stepped blasting is conducted, and S3 and S4 are repeated till foundation pit excavation is completed. According to the method, the blasting cross section of the foundation pit is partitioned, the blasting intensity of the middle area is larger than that of the areas on the two sides, on one hand, high-strength blasting in the middle can rapidly break a large amount of earth and rocks, and on the other hand, relatively low-strength blasting on the two sides is beneficial for reducing interference of vibration to the surrounding environment; and on the premise of ensuring the safety of buildings around the foundation pit, the blasting efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of blasting construction, and more specifically to a high-efficiency foundation pit earthwork blasting construction process. Background Art

[0002] In the current foundation pit excavation operations, blasting technology is a common construction method. Traditional methods often adopt a more conservative strategy, that is, first test with the minimum blasting intensity, and then reserve a safety margin on this basis to ensure the safety of surrounding buildings. Although this approach has reduced the risk of construction to the surrounding environment to a certain extent, it has also led to a significant reduction in blasting efficiency. Due to the limited amount of earth and stone blasted each time, the construction progress of the entire project is restricted. At the same time, frequent blasting operations have also greatly increased construction costs and time costs.

[0003] With the acceleration of urbanization, the foundation pit construction environment is becoming increasingly complex. How to improve blasting efficiency while ensuring safety has become a technical problem that needs to be solved urgently. Summary of the invention

[0004] In order to solve or alleviate the problem in the above-mentioned prior art on how to improve blasting efficiency while ensuring safety, the present invention provides a high-efficiency foundation pit earthwork blasting construction process.

[0005] The technical solution of the present invention is as follows:

[0006] An efficient foundation pit earthwork blasting construction process comprises the following steps:

[0007] S1. For the blasting division of the foundation pit blasting cross section, the blasting intensity in the middle area is greater than that in the areas on both sides;

[0008] S2, excavate the surface soil and trim the rock surface;

[0009] S3. Set up flying rock protection in the blasting area;

[0010] S4. Divide the foundation pit into sections and layers. First blast the middle part of each layer of the upper foundation pit, then blast the two sides. First blast the two sides of each layer of the lower foundation pit, then blast the middle part.

[0011] S5: Step blasting, repeat S3 and S4 until the foundation pit excavation is completed.

[0012] Furthermore, in S1, the blasting zones include a pyrotechnic blasting zone in the middle and static blasting zones and pre-splitting blasting zones on both sides of the pyrotechnic blasting zone. The static blasting zone is located at the upper part of the foundation pit, and the pre-splitting blasting zone is located at the lower part of the foundation pit.

[0013] Further, in S4, the pyrotechnic blasting area construction steps include:

[0014] S411, pyrotechnic blasting parameter design;

[0015] S412, level the site and mark the drilling position;

[0016] S413, drilling blastholes and cleaning waste residues;

[0017] S414, install explosives, detonators and detonating cords to block blast holes;

[0018] S415, laying out the detonation network and detonating;

[0019] S416. Safety inspection, clearing of duds.

[0020] Further, in S4, the static blasting area construction steps include:

[0021] S421, static blasting parameter design;

[0022] S422, level the site and mark the drilling position;

[0023] S423, drilling and cleaning waste residue;

[0024] S424, filling crushing agent to block the orifice;

[0025] S425, crack and clean up the waste residue.

[0026] Further, in S4, the pre-splitting blasting area construction steps include:

[0027] S431, pre-splitting blasting parameter design;

[0028] S432, level the site and mark the drilling position;

[0029] S433, drilling blastholes and cleaning waste residue;

[0030] S434, install explosives, detonators and detonating cords to block blast holes;

[0031] S435, laying out the detonation network and detonating;

[0032] S436, safety inspection, clearing of duds.

[0033] Further, in S4, the blasthole plane is arranged in a plum blossom shape or a square shape.

[0034] Further, in S4, detonation is performed row by row, each row is detonated one by one, the detonation time difference between adjacent blast holes is the first interval time, and the detonation time difference between adjacent blast rows is the second interval time.

[0035] Further, in S4, groove blasting is carried out first, and the blast holes are arranged in a square array and blasted sequentially from the inside to the outside. The innermost circle is blasted synchronously, and the time difference between the detonation of the innermost circle and the second inner circle is the third interval time, and the time difference between the detonation of adjacent blast holes from the second inner circle to the outermost circle is the fourth interval time.

[0036] Furthermore, in S4, the maximum single-shot charge quantity is calculated for blasting vibration safety:

[0037] Q max =(R(V / K) 1 / α ) 3

[0038] K: coefficient related to the medium properties of the earthquake propagation area;

[0039] α: seismic wave attenuation coefficient;

[0040] R: the shortest straight-line distance from the blasting site to the building;

[0041] V: Safe vibration velocity of surrounding buildings, V=1.0cm / s; Safe vibration velocity of buildings under construction, V=2.0cm / s.

[0042] Furthermore, in S3, flying rock protection includes shielding protection at the foundation pit entrance and covering protection of the surface of the blasting area. The shielding protection at the foundation pit entrance is a protection shed, and the covering protection of the surface of the blasting area includes sand bags at the hole opening, wire mesh sheets, and a protection shed.

[0043] The beneficial effect of the present invention according to the above scheme is that the present invention divides the foundation pit blasting cross-section into zones, and the blasting intensity in the middle zone is greater than the blasting intensity in the two side zones. On the one hand, the high-intensity blasting in the middle can quickly crush a large amount of earth and stone, and on the other hand, the relatively low-intensity blasting on the two sides helps to reduce the interference of vibration on the surrounding environment, thereby achieving a balance between blasting effect and environmental protection, and improving blasting efficiency while ensuring the safety of buildings around the foundation pit. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0045] Figure 1 It is a schematic diagram of blasting divisions of the cross section of foundation pit blasting of the present invention;

[0046] Figure 2 It is a schematic diagram of the arrangement of plum blossom-shaped blast holes of the present invention;

[0047] Figure 3 It is a cross-sectional view of the blasting drilling arrangement of the present invention;

[0048] Figure 4 It is a schematic diagram of the arrangement of the blast holes for the slot blasting of the present invention;

[0049] Figure 5 It is a cross-sectional view of the arrangement of the slotting blasting drilling of the present invention;

[0050] Figure 6 This is a schematic diagram of shielding and protecting the foundation pit opening of the present invention;

[0051] Figure 7 This is a schematic diagram of the explosion zone surface covering protection of the present invention;

[0052] Figure 8 It is a schematic diagram of the foundation pit excavation flow direction of the present invention.

[0053] Among them, the figure marks in the figure are: 1. pyrotechnic blasting area; 2. static blasting area; 3. hanging piles; 4. pre-splitting blasting area; 5. protective layer; 6. shielding and protection of foundation pit mouth; 7. Surface covering protection of blasting area; 8. crown beam or middle plate side beam; 9. sandbag; 10. wire mesh; 11. steel plate; 12. weight; 13. groove blasting area. DETAILED DESCRIPTION

[0054] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0055] It should be noted that when a component is referred to as being "fixed" or "set" or "connected" to another component, it may be located directly or indirectly on the other component. The directions or positions indicated by the terms "upper", "lower", "left", "right", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are based on the directions or positions shown in the accompanying drawings and are only for the convenience of description and should not be construed as limitations on the present technical solution. The terms "first", "second", etc. are only used for the convenience of description and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features. "Multiple" means two or more, unless otherwise clearly and specifically defined. "Several" means one or more, unless otherwise clearly and specifically defined.

[0056] like Figure 1 and Figure 6 As shown, an efficient foundation pit earthwork blasting construction process described in one embodiment of the present invention includes the following steps:

[0057] S1. For the blasting division of the foundation pit blasting cross section, the blasting intensity in the middle area is greater than that in the areas on both sides;

[0058] S2, excavate the surface soil and trim the rock surface;

[0059] S3. Set up flying rock protection in the blasting area;

[0060] S4. Divide the foundation pit into sections and layers. The upper layers of the foundation pit are blasted in the middle first, and then on both sides. The static crushing method is used 0.5m away from the foundation pit retaining structure, and the digital electronic detonator fine control blasting method is used in other places. The lower layers of the foundation pit are blasted on both sides first, and then in the middle; the vibration speed of the protected buildings around the foundation pit blasting area is controlled within 2.0cm / s, and the vibration speed of key protected buildings such as laboratories is controlled within 1.0cm / s. Communicate and coordinate with surrounding units to determine a reasonable detonation time. Among them, the digital electronic detonator detonation technology can effectively reduce the impact of blasting vibration compared with non-electric detonation technology. Digital electronic detonator is a new type of electric detonator that can be arbitrarily adjusted and achieves precise delayed ignition time. The delay accuracy can reach 1ms, and it has high safety.

[0061] S5: Step blasting, repeat S3 and S4 until the foundation pit excavation is completed.

[0062] When the foundation pit is excavated to the soil-rock boundary, the natural height difference terrain advantage is used to directly carry out step blasting excavation construction. If there is no natural height difference advantage, the step surface is formed by hydraulic hammer construction and then the step blasting is carried out. The longitudinal segmentation and vertical layering excavation are adopted to the base. The excavation height of the shallow hole step loose control blasting step is controlled at 1.0 to 3.0m. The large blocks, isolated rocks and foundation produced by blasting are handled by hydraulic breaker.

[0063] In this embodiment, the blasting cross-section of the foundation pit is divided into zones, and the blasting intensity in the middle area is greater than that in the two side areas. On the one hand, the high-intensity blasting in the middle can quickly crush a large amount of earth and stone, and on the other hand, the relatively low-intensity blasting on both sides helps to reduce the interference of vibration on the surrounding environment, thereby achieving a balance between blasting effect and environmental protection, and improving blasting efficiency while ensuring the safety of buildings around the foundation pit.

[0064] Secondly, by excavating the surface soil and trimming the rock surface, conditions are created for subsequent blasting operations, which helps to improve the accuracy of blasting, reduce unnecessary energy consumption and waste of blasting materials, and further improve the economy of construction.

[0065] Furthermore, the installation of flying rock protection can effectively prevent flying rocks generated during the blasting process from causing harm to construction workers and surrounding buildings, providing a solid safety guarantee for the entire construction process.

[0066] In addition, the segmented and layered blasting strategy, combined with different blasting sequences in the upper and lower parts of the foundation pit, optimizes the release of blasting energy, reduces the amount of earth and stone in a single blasting, and ensures the smooth excavation of the foundation pit. The stepped blasting strategy not only helps to control the vibration waves generated by blasting, but also enables the rapid cleaning of earth and stone.

[0067] like Figure 1 As shown, in S1, the blasting zones include a pyrotechnic blasting zone 1 located in the middle and a static blasting zone 2 and a pre-splitting blasting zone 4 located on both sides of the pyrotechnic blasting zone 1. The static blasting zone 2 is located at the upper part of the foundation pit, and the pre-splitting blasting zone 4 is located at the lower part of the foundation pit.

[0068] In this embodiment, the static blasting area 2 is located at the upper part of the foundation pit, and a static crushing agent is used to perform a vibration-free and rock-free crushing operation, which effectively reduces the disturbance to the upper soil layer and the potential impact on surrounding buildings; while the pre-splitting blasting area 4 is located at the lower part of the foundation pit, and through pre-blasting, a vibration-isolating crack is formed to isolate the blasting energy in the middle from being released to the lower soil layer, effectively controlling the interference of the blasting vibration on the bottom of the foundation pit and the surrounding strata, and facilitating the smooth removal of earth and stone. This partitioned blasting strategy can not only improve the safety and efficiency of blasting operations, but also protect the environment around the foundation pit.

[0069] like Figure 2 and Figure 3 As shown, in S4, the construction steps of the pyrotechnic blasting area 1 include:

[0070] S411, pyrotechnic blasting parameter design;

[0071] S412, level the site and mark the drilling position;

[0072] S413, drilling blastholes and cleaning waste residues;

[0073] S414, install explosives, detonators and detonating cords to block blast holes;

[0074] S415, laying out the detonation network and detonating;

[0075] S416. Safety inspection, clearing of duds.

[0076] Specifically, the diameter of the blasting borehole should not be too large, and the number of rows should not be too many, not more than 5 rows, and 3 rows are the main ones. The closer to the protected object, the smaller the step height should be, and the step height should not exceed 3m. The blasting vibration can be reduced by controlling the charge amount of a single hole, and the digital electronic detonator detonation technology can be combined to achieve the purpose of comprehensive control of blasting vibration. The borehole diameter in the plan is selected as d=42mm. The blasting parameters are calculated according to the following formulas (H represents the step height):

[0077] The borehole diameter is Φ = 42mm. The blasthole plane is arranged in a plum blossom or square shape, and the borehole is drilled vertically. Tubular emulsion explosives are used. The calculation formula for the blasting parameters is as follows (H represents the step height):

[0078] Minimum resistance line W = 25Φ, drilling over-depth h = 0.4W, blasthole depth L = (H + h), blocking length lˊ = (1.1 ~ 1.5)W, charging length l = (L – lˊ), hole spacing a = 1.2W, row spacing b = W, single hole charge Q = q·a·b·H, explosive unit consumption q = 0.45 ~ 0.60 (unit: kg / m 3 ), the Φ42 step controlled blasting parameters calculated are listed in Table 1.

[0079] Table 1d=42mm step controlled blasting parameters

[0080] H(m) W(m) h(m) a(m) b(m) L(m) l(m) lˊ(m) Q(kg) 1.5 1.2 0.5 1.4 1.2 2.0 1.2 0.8 1.1 2.0 1.2 0.5 1.4 1.2 2.5 1.5～1.7 0.8～1.0 1.4～1.5 3.0 1.2 0.8 1.4 1.2 3.8 2.3～2.6 1.2～1.5 2.1～2.4 4.0 1.2 0.8 1.4 1.2 4.8 3.0～3.4 1.4～1.8 2.7～3.1

[0081] In S414, if blockage or stuck holes are found during the charging process, the charging should be stopped and the holes should be cleared in time. If detonators or explosive packages have been loaded, pay attention to the detonators or explosive packages during the handling process. Use a long wooden pole for handling, and it is strictly forbidden to use drilling tools, steel bars, etc. for handling.

[0082] Commonly used plugging materials are stone powder slag, and no stones should be mixed in the plugging materials. According to the scale marks on the gun stick, control the length of the plugging to meet the design requirements. Do not tamp the plugging materials that directly contact the explosive package or use the plugging materials to impact the detonating package. When plugging, pay attention to the detonator foot line, etc. to prevent it from being broken, damaged, or tightened.

[0083] In S4, the construction steps of static blasting area 2 include:

[0084] S421. Static blasting parameter design. Specific parameters are shown in Table 2.

[0085] Table 2 Main parameters of static blasting construction

[0086] Serial number parameter Quantity Description 1 Aperture d(mm) 42 2 Step height H(m) 1.0～3.0 3 Hole depth L(m) 1.1～3.3 4 <![CDATA[Bench resistance line W p (m)]]> 0.25～0.3 5 Hole and row spacing (m) 0.25～0.4 6 <![CDATA[Unit consumption kg / m 3 > 20～30 7 Ultra-deep △h(m) 0.1～0.3 8 Static crushing agent type SCA-Ι Model 9 Hole layout Square or plum blossom 10 Charge structure Continuous charge coupled charge

[0087] S422, level the site and mark the drilling position;

[0088] S423, drill holes and clean up waste residues; the diameter of the drill hole is directly related to the crushing effect. If the drill hole is too small, it is not conducive to the full effectiveness of the agent; if the drill hole is too large, it is easy to punch. Specifically, choose a Φ42mm blast hole. The remaining water and residue in the drill hole should be blown clean with high-pressure air, and the area around the hole should be kept clean and free of soil and stone residues.

[0089] S424, filling crushing agent to block the orifice;

[0090] S425, crack and clean up the waste residue.

[0091] In S424, the powdered agent is first mixed with water and stirred thoroughly. For vertical holes drilled from top to bottom, the weight ratio of water to agent is 0.34:1, and the temperature of the water should be consistent with the atmospheric temperature.

[0092] During operation, the agent should be slowly poured into the weighed water, rather than the water slowly poured into the agent. Stir continuously while pouring until the mixture of agent and water becomes a fluid paste or clay. The speed of pouring and stirring should be fast. The time from adding the agent into the water to the completion of pouring into the drilling hole should be controlled within 5-10 minutes, otherwise it is easy to punch the hole.

[0093] Before charging, the inside and the side of the borehole should be kept clean, and the remaining water and residue should be washed clean with high-pressure air. Each time the reagent is loaded, it is necessary to observe and determine whether the temperature of the rock, reagent and mixing water meets the requirements. For vertical holes, pour the mixture directly into the hole and fill the mixture densely. For horizontal holes and inclined holes, the ratio of water to reagent poured into the hole should be 0.28:1, in the form of clay. Use a steel pipe that is the same size as the hole, divide the steel pipe into two halves according to the diameter, load the clay-like mixture into the combined steel pipe, and insert it into the hole until the reaction is completed. The angle of insertion is determined by the principle that the joint seam of the steel pipe is consistent with the fracture direction of the mining object, and the steel pipe can be reused.

[0094] Since the time required from the preparation of the reagent to the sealing of the filling hole is short, multiple filling teams need to be arranged. Each team consists of two fillers, the main filler and the deputy filler. When taking the reagent and mixing it, the main filler is responsible for weighing the reagent and water, and the deputy filler is responsible for stirring the reagent. When filling, the main filler is responsible for filling into the hole, and the deputy filler is responsible for ensuring that the reagent is tamped and the hole mouth is sealed. Each team adopts the "synchronous operation, less mixing and more frequent filling" mode of operation. The number of holes that the filling team is responsible for filling in each operation cycle should not be too many. Each filling team should basically keep in sync during the weighing, mixing, filling and other processes, and try to make the maximum expansion force of the reagent in each hole appear at the same time, which is conducive to the crushing of bedrock.

[0095] The speed of the agent reaction is directly related to the temperature. The higher the temperature, the faster the reaction time, and vice versa. In actual operation, there are two ways to control the reaction time of the agent. One is to add inhibitors to the mixing water, and the other is to strictly control the temperature of the mixing water, the agent and the pre-crushed bedrock. In summer, the temperature is high. Before crushing, the crushed objects should be shielded and the agents should be stored in a low temperature place to avoid exposure. Agents that have already started chemical reactions (as shown by the beginning of gas emission and rapid temperature rise) must not be loaded into the hole.

[0096] In S4, the construction steps of the pre-splitting blasting zone 4 include:

[0097] S431, pre-splitting blasting parameter design;

[0098] S432, level the site and mark the drilling position;

[0099] S433, drilling blastholes and cleaning waste residue;

[0100] S434, install explosives, detonators and detonating cords to block blast holes;

[0101] S435, laying out the detonation network and detonating;

[0102] S436. Safety inspection, clearing of duds.

[0103] In order to ensure the integrity of the rock of the reserved protective layer 5 at the bottom of the hanging foot pile 3, pre-splitting blasting is carried out below the bottom of the hanging foot pile 3. Pre-splitting holes are set 1.0m away from the retaining structure, and the depth of each layer of pre-splitting blasting is 5-6m. Before the blasting of the foundation pit stone, the pre-splitting blasting method is used to form a pre-splitting shock-absorbing belt, which can effectively reduce the impact of the blasting vibration of the stone blasting on the retaining structure and external protection, and ensure the integrity of the reserved protective layer 5.

[0104] Specifically, the pre-splitting blasting parameters are as follows: the pre-splitting blasting borehole diameter is d = 76 mm, and the borehole is vertical. The explosive is d32 mm tubular emulsion explosive, the hole depth is 5 to 6 m, the pre-splitting blasting line charge density qˊ = 0.2 kg / m, the blocking length lˊ ≥ 1.0 m, and the initial value is 1.1 m.

[0105] The pre-splitting blasting parameters are selected according to the rock properties. For intact hard rock mass, the larger value is taken, and vice versa, the smaller value is taken. Pre-splitting blasting uses detonating cords to transmit explosions in the hole. In order to ensure the crushing effect at the bottom of the blasthole, the bottom of the hole is reinforced with explosives. The amount of the reinforced charge section is determined according to the rock properties. The length of the blasthole plugging is not less than 1m. Rolled emulsion explosives are used for continuous charging, and stone powder slag is used as the plugging material. The detonating charge is located at the bottom of the blasthole and is reversely detonated.

[0106] like Figure 2 and Figure 4 As shown, in S4, the blast holes are arranged in a plum blossom or square shape.

[0107] In S4, detonation is performed row by row, and the unobstructed row is detonated first, and each row is detonated one by one. The detonation time difference between adjacent blast holes is the first interval time, and the detonation time difference between adjacent blast rows is the second interval time. Specifically, the first interval time is 8 to 20 ms, and the second interval time is 80 to 120 ms. Preferably, the first interval time is 17 ms, and the second interval time is 111 ms.

[0108] Under the same charge, terrain, geology and other conditions, the digital electronic detonator with precise micro-difference detonation has a small peak velocity and small discreteness of blasting vibration. By reasonably setting the micro-difference time of detonation, the sub-wave phase generated by each blast hole is shifted, and the peak and valley are superimposed, thereby achieving the interference vibration reduction effect. According to the wave superposition theory, it is known that the micro-difference interval time difference between the two blastings can be reasonably selected so that the peak of the vibration wave generated by the later explosive can be generated at the same time as the trough of the vibration wave generated by the first explosive. The amplitude of the superimposed part of the vibration wave should be significantly reduced, and the destructive effect of the explosion can be minimized. At the same time, by optimizing the delay time, the blasting vibration is adjusted to a uniformly distributed high-frequency low-peak waveform, and the vibration frequency is much greater than the natural frequency of the building, avoiding "quasi-resonance" and avoiding damage to the building (structure). Reasonable detonation sequence and detonation method can control the throwing direction of flying rocks, reduce the harm of flying rocks, and also have the effect of reducing blasting vibration.

[0109] like Figure 4 , Figure 5 and Figure 8 As shown, in S4, groove blasting is first performed, and there are three groove blasting areas 13, which are located at both ends and in the middle of the foundation pit. The blast holes are arranged in a square array, and are blasted sequentially from the inside to the outside. The innermost circle is blasted synchronously, and the detonation time difference between the innermost circle and the second inner circle is the third interval time, and the detonation time difference between adjacent blast holes from the second inner circle to the outermost circle is the fourth interval time.

[0110] Hole arrangement: 16 holes in total, with a hole diameter of Φ42, arranged vertically. According to the distance from the building (structure), the hole depth is 3.0m, and the blast holes are arranged in a square, that is, the spacing a = row spacing b, which is 1.0m. Calculate the unit consumption of explosives Q j =0.45, meter charge Q l Press 1.1kg / m.

[0111] The micro-difference time of the middle 4 holes is set to 0ms, and the subsequent second sound delay time is 100ms, that is, the third interval time is 100ms, and the subsequent sequential detonation time difference is 25ms, that is, the fourth interval time is 25ms.

[0112] Single hole charge Q: When the hole depth is 3.0m, the charging length is 1.65m, the single hole charging amount Q = 1.65 × 1.1 = 1.815, take 1.8kg; the maximum charge in the same section is 7.2kg.

[0113] When the slot arrangement is 2×2, the calculated unit consumption of explosives is the larger value, and the calculated unit consumption is Q j =0.45kg / m 3 (Reverse calculation of actual unit consumption q: When the depth is 3.0m, q≈0.60kg / m 3 The actual unit consumption is calculated as q = single hole dosage / burden area × hole depth = 1.8 / 1.0 × 1.0 × 3.0).

[0114] The single hole charge Q is calculated based on different hole depths and the minimum spacing in the same section:

[0115] Q=L y Q L ,kg

[0116] Where L y ——Charge length, m;

[0117] Q L ——Charge quantity per meter: 1.1kg / m.

[0118] L y Calculate as follows:

[0119]

[0120] Where L t ——blocking backfill length, m;

[0121] a——minimum spacing in the same section, m;

[0122] L——blasthole depth, m;

[0123] Q j ——Calculate unit consumption and take Q j =0.45kg / m 3 .

[0124] L t Calculate as follows:

[0125]

[0126] In S4, the maximum single-shot charge is calculated for blasting vibration safety:

[0127] Q max =(R(V / K) 1 / α ) 3

[0128] K: A coefficient related to the medium properties of the earthquake propagation area, which is taken as 150;

[0129] α: seismic wave attenuation coefficient, taken as 1.8;

[0130] R: the shortest straight-line distance from the blasting site to the building;

[0131] V: Safe vibration velocity of surrounding buildings, V=1.0cm / s; Safe vibration velocity of buildings under construction, V=2.0cm / s.

[0132] Safety verification: Because a key laboratory is closest to the foundation pit and has the highest vibration control standard, its vibration verification meets the requirements, and other places can also control the blasting vibration within the safe range, so a key laboratory is taken as an example. The single-hole charge of this project is in the range of 1.1 to 3.1 kg. The closest distance from a key laboratory to the blasting area is 19.4m + 1m (enclosing structure width) + 0.5m (static crushing range) = 20.9m, and the farthest distance can exceed 20.9m + 26.1m (standard width of the foundation pit) - 0.5m × 2 = 46m. When blasting at 20.9m in the nearest area, the step height is controlled within 2m, the maximum charge of a single hole is 1.5kg, and the blasting vibration generated by theoretical calculation is 0.80cm / s, which meets the vibration speed control requirements.

[0133] like Figure 6 and Figure 7 As shown, in S3, the flying rock protection includes a foundation pit mouth shielding protection 6 and a blasting area surface covering protection 7. The foundation pit mouth shielding protection 6 is a protection shed, and the blasting area surface covering protection 7 includes a hole mouth sand bag 9, a wire mesh sheet 10, and a steel plate 11.

[0134] The shielding protection 6 of the foundation pit opening is set on the crown beam or the middle plate side beam 8, and is divided into two directions, the dominant direction and the back direction, with the blasting area as the center. The dominant direction is the angle between the straight line formed by the foot of the step blasting and the extension of the covering protection shed and the horizontal plane is not greater than 20°, that is, the horizontal distance S from the foot of the slope vertically upward to the protection shed extending outward 主 Vertical height H from the protective shed to the slope foot 主 The ratio is not less than 2.75; the angle between the line connecting the hole openings of the last row of holes blasted in steps and the extension of the protective shed and the horizontal plane is not greater than 40°, that is, the horizontal distance S from the hole openings of the last row of holes vertically upward to the extension of the protective shed outward 背 The vertical height H from the protective shed to the last row of holes 背 The ratio is not less than 1.19.

[0135] The excavation depth of the station's foundation pit is about 20m. According to the above requirements, the shielding and protection range of the foundation pit mouth is calculated as follows: the shielding range of the foundation pit mouth in the dominant direction of blasting is 55m, and the range in the opposite direction is 24m. Therefore, the total shielding length of the foundation pit mouth needs to be 80m, which can ensure that the flying rocks caused by blasting are completely controlled within the foundation pit.

[0136] The surface of the blasting area at the bottom of the foundation pit is covered with protective measures 7, that is, sand bags 9 are pressed at the hole mouth, and sand bags 9 are filled with sand and soil. Filling with stones is strictly prohibited; afterwards, the surface of the blasting area is fully covered with wire mesh sheets 10 to fix the sand bags 9, and steel plates 11 are laid on the wire mesh sheets 10, and weights 12 are placed on the steel plates 11. The extension of the steel plate 11 when laying the blasthole is not less than 1m, and the overlap width is not less than 20cm. After the charging and networking are completed, a sand bag 9 is pressed at the mouth of the blasthole, and sand bags 9 are distributed at intervals in the blasting area. The detonating cords of the detonation network are scattered in the gaps between the sand bags 9 to avoid direct contact between the steel plates 11 and the detonator foot wires during the covering process.

[0137] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An efficient foundation pit earthwork blasting construction process, characterized in that: The following steps are involved: S1. For the blasting division of the foundation pit blasting cross section, the blasting intensity in the middle area is greater than that in the areas on both sides; S2, excavate the surface soil and trim the rock surface; S3. Set up flying rock protection in the blasting area; S4. Divide the foundation pit into sections and layers. First blast the middle part of each layer of the upper foundation pit, then blast the two sides. First blast the two sides of each layer of the lower foundation pit, then blast the middle part. S5: Step blasting, repeat S3 and S4 until the foundation pit excavation is completed.

2. According to the high-efficiency foundation pit earthwork blasting construction process described in claim 1, it is characterized in that: In S1, the blasting zones include a pyrotechnic blasting zone in the middle and static blasting zones and pre-splitting blasting zones on both sides of the pyrotechnic blasting zone. The static blasting zone is located at the upper part of the foundation pit, and the pre-splitting blasting zone is located at the lower part of the foundation pit.

3. According to the high-efficiency foundation pit earthwork blasting construction process described in claim 1, it is characterized in that: In S4, the construction steps of the pyrotechnic blasting area include: S411, pyrotechnic blasting parameter design; S412, level the site and mark the drilling position; S413, drilling blastholes and cleaning waste residues; S414, install explosives, detonators and detonating cords to block blast holes; S415, laying out the detonation network and detonating; S416. Safety inspection, clearing of duds.

4. According to the high-efficiency foundation pit earthwork blasting construction process described in claim 1, it is characterized in that: In S4, the static blasting area construction steps include: S421, static blasting parameter design; S422, level the site and mark the drilling position; S423, drilling and cleaning waste residue; S424, filling a crushing agent to block the orifice; S425, crack and clean up the waste residue.

5. According to the high-efficiency foundation pit earthwork blasting construction process described in claim 1, it is characterized in that: In S4, the construction steps of the pre-splitting blasting area include: S431, pre-splitting blasting parameter design; S432, level the site and mark the drilling position; S433, drilling blastholes and cleaning waste residue; S434, install explosives, detonators and detonating cords to block blast holes; S435, laying out the detonation network and detonating; S436. Safety inspection, clearing of duds.

6. A high-efficiency foundation pit earthwork blasting construction process according to claim 1, characterized in that: In S4, the blastholes are arranged in a plum blossom or square shape.

7. According to the high-efficiency foundation pit earthwork blasting construction process described in claim 1, it is characterized in that: In S4, detonation is performed row by row, each row is detonated one by one, the detonation time difference between adjacent blast holes is the first interval time, and the detonation time difference between adjacent gun rows is the second interval time.

8. The high-efficiency foundation pit earthwork blasting construction process according to claim 1 is characterized in that: In S4, groove blasting is carried out first, and the blast holes are arranged in a square array and blasted sequentially from the inside to the outside. The innermost circle is blasted synchronously. The time difference between the detonation of the innermost circle and the second inner circle is the third interval time, and the time difference between the detonation of adjacent blast holes from the second inner circle to the outermost circle is the fourth interval time.

9. The high-efficiency foundation pit earthwork blasting construction process according to claim 1, characterized in that: In S4, the maximum single-shot charge is calculated for blasting vibration safety: Q max =(R ( VK) 1 / α ) 3 K: coefficient related to the medium properties of the earthquake propagation area; α: seismic wave attenuation coefficient; R: the shortest straight-line distance from the blasting site to the building; V: Safe vibration velocity of surrounding buildings, V=1.0cm / s; Safe vibration velocity of buildings under construction, V=2.0cm / s.

10. The high-efficiency foundation pit earthwork blasting construction process according to claim 1, characterized in that: In S3, flying rock protection includes shielding protection at the foundation pit entrance and covering protection of the blasting area surface. The shielding protection at the foundation pit entrance is a protective shed, and the covering protection of the blasting area surface includes sand bags at the hole, wire mesh sheets, and protective sheds.

Images