Arch seat foundation pit blasting excavation structure and method

Abstract

The present invention discloses a blasting excavation structure and method for an arch abutment foundation pit. The blasting excavation structure for the arch abutment foundation pit includes an existing foundation pit slope platform, and the existing foundation pit slope platform includes a left bank arch abutment and a right bank arch abutment arranged at intervals. Blasting steps are provided on both the left bank arch abutment and the right bank arch abutment, and a plurality of blast holes are formed in the blasting steps; a plurality of charging structures, the number of the charging structures is the same as that of the blast holes and they are arranged in one-to-one correspondence, and each of the charging structures is stuffed into the corresponding blast hole; wherein, each of the blast holes is inclined in the blasting step with respect to the bottom surface of the blasting step, and the blast holes are arranged at intervals. The present invention improves the blasting excavation effect of the blast holes and the construction quality of the project by arranging blast holes on the existing foundation pit and controlling the specific formation structure of the blast holes, and provides a reference for similar construction modes.

Description

Technical Field

[0001] The present invention relates to the technical field of secondary excavation of existing foundation pits, and particularly to a blasting excavation structure and method for an arch seat foundation pit. Background Art

[0002] In the related art, since the excavation of the arch seat foundation pit belongs to secondary excavation, it is necessary to re-slope the slope of the excavated foundation pit. Moreover, the slope is relatively steep, the overburden is thin, part of the bedrock is exposed, and the working platform range is limited.

[0003] Therefore, during the process of excavating the arch seat foundation pit, the method of setting blast holes in the existing foundation pit and the specific structure of the blast holes determine the quality of the secondary excavation of the arch seat foundation pit.

[0004] However, the current blast hole layout method and blast hole formation structure cannot be directly applied to the secondary excavation of the arch seat foundation pit with a relatively steep slope, thin overburden, part of the bedrock exposed, and limited working platform range, and cannot guarantee the blasting excavation effect of the blast holes and the quality of the engineering construction. Summary of the Invention

[0005] The main purpose of the present invention is to provide a blasting excavation structure and method for an arch seat foundation pit, aiming to solve the technical problem that the current blast hole layout method and blast hole formation structure in the prior art cannot be directly applied to the secondary excavation of the arch seat foundation pit with a relatively steep slope, thin overburden, part of the bedrock exposed, and limited working platform range, and cannot guarantee the blasting excavation effect of the blast holes and the quality of the engineering construction.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a blasting excavation structure for an arch seat foundation pit, including:

[0008] An existing foundation pit slope platform, the existing foundation pit slope platform includes a left bank arch seat and a right bank arch seat arranged at intervals, and blasting steps are provided on both the left bank arch seat and the right bank arch seat, and a plurality of blast holes are opened on the blasting steps;

[0009] A plurality of charging structures, the number of the charging structures is the same as that of the blast holes and they are arranged in one-to-one correspondence, and each charging structure is stuffed into the corresponding blast hole;

[0010] Wherein, each blast hole is inclined in the blasting step with respect to the bottom surface of the blasting step, and the blast holes are arranged at intervals.

[0011] Optionally, in the above blasting excavation structure for an arch seat foundation pit, the orifice diameter of the blast hole is A, the bottom diameter of the blast hole is B, and A ≤ 2B / 3.

[0012] Optionally, in the above-mentioned blasting excavation structure of the arch abutment foundation pit, multiple said blast holes are distributed in a plum blossom pattern.

[0013] Optionally, in the above-mentioned blasting excavation structure of the arch abutment foundation pit, the blast holes are shallow blasting holes;

[0014] The charging structure includes:

[0015] A charging section, the charging section is tamped in the shallow blasting hole, and the charging section extends from the bottom of the shallow blasting hole towards the orifice of the shallow blasting hole;

[0016] A stemming section, the stemming section is tamped at the orifice of the shallow blasting hole;

[0017] An in-hole detonator, the in-hole detonator is buried in the charging section;

[0018] A detonating fuse, one end of the detonating fuse extends into the charging section and is connected to the in-hole detonator, and the other end of the detonating fuse extends out of the charging section from the orifice of the shallow blasting hole.

[0019] Optionally, in the above-mentioned blasting excavation structure of the arch abutment foundation pit, the blast holes are deep blasting holes;

[0020] The charging structure includes:

[0021] A charging section, the charging section is tamped in the deep blasting hole, and the charging section extends from the bottom of the deep blasting hole towards the orifice of the deep blasting hole;

[0022] A stemming section, the stemming section is tamped at the orifice of the deep blasting hole;

[0023] Two in-hole detonators, two in-hole detonators are buried in the charging section, the two in-hole detonators are arranged at intervals, each in-hole detonator is connected with a detonating fuse, one end of each detonating fuse extends into the charging section and is connected to the corresponding in-hole detonator, and the other end of the detonating fuse extends out of the charging section from the orifice of the deep blasting hole.

[0024] Optionally, in the above-mentioned blasting excavation structure of the arch abutment foundation pit, the two in-hole detonators are respectively a first in-hole detonator and a second in-hole detonator, the depth of the deep blasting hole is C, the embedding depth of the first in-hole detonator is C / 3, and the embedding depth of the second in-hole detonator is 2C / 3.

[0025] Optionally, in the above-mentioned blasting excavation structure of the arch abutment foundation pit, multiple said blast holes are multiple main blasting holes and multiple smooth blasting holes, multiple said main blasting holes are linearly arranged at intervals in sequence along the length direction of the blasting bench to form a first blast hole group, multiple said smooth blasting holes are linearly arranged at intervals in sequence along the length direction of the blasting bench to form a second blast hole group, and the first blast hole group and the second blast hole group are arranged at intervals in the width direction of the blasting bench.

[0026] In a second aspect, the present invention provides a method for blasting and excavating an arch seat foundation pit, which is used to form the arch seat foundation pit blasting and excavating structure as described above. The method includes:

[0027] Set a minimum resistance line at the bottom side of the blasting bench, and obtain the length of the minimum resistance line;

[0028] Set a bench upper brow line at the top side of the blasting bench, and obtain the length of the bench upper brow line;

[0029] Obtain the slope angle of the blasting bench according to the length of the minimum resistance line and the length of the bench upper brow line;

[0030] Preset the over-depth of the blast hole;

[0031] Drill holes on the surface of the blasting bench to form the blast holes according to the slope angle of the blasting bench, the height of the blasting bench, and the over-depth of the blast holes;

[0032] Obtain the charge amount according to the type of the blast hole;

[0033] Fill the charge structure into the blast hole according to the charge amount to form the arch seat foundation pit blasting and excavating structure.

[0034] Optionally, in the above method for blasting and excavating an arch seat foundation pit, the type of the blast hole is a multi-column blast hole. The multi-column blast hole includes a front row of blast holes and a second row of blast holes spaced from the front row of blast holes. The front row of blast holes is composed of a plurality of the blast holes arranged at intervals, and the second row of blast holes is composed of a plurality of the blast holes arranged at intervals;

[0035] The step of obtaining the charge amount according to the type of the blast hole includes:

[0036] Obtain the charge amount of the front row of blast holes according to the unit explosive consumption, the spacing between the blast holes in the front row of blast holes, the hole depth of the front row of blast holes, and the minimum resistance line;

[0037] Obtain the charge amount of the second row of blast holes according to the unit explosive consumption, the spacing between the blast holes in the second row of blast holes, the hole depth of the second row of blast holes, and the spacing between the second row of blast holes and the front row of blast holes.

[0038] Optionally, in the above method for blasting and excavating an arch seat foundation pit, the type of the blast hole is a smooth blasting hole;

[0039] The step of setting a minimum resistance line at the bottom side of the blasting bench and obtaining the length of the minimum resistance line includes:

[0040] Obtain the length of the minimum burden of the smooth blasting hole according to the aperture of the smooth blasting hole;

[0041] Wherein, the aperture of the smooth blasting hole is D 光 , and the length of the minimum burden of the smooth blasting hole is W 光 W 光 = β * D 光 , 15 ≤ β ≤ 25.

[0042] One or more of the above technical solutions provided by the present invention may have the following advantages or at least achieve the following technical effects:

[0043] A blasting excavation structure and method for an arch seat foundation pit proposed by the present invention, by setting blast holes on the existing foundation pit and using the blast holes to perform secondary excavation on the blasting platform of the existing foundation pit to form a secondary foundation pit that meets the construction requirements, which is conducive to the subsequent construction of the secondary arch seat foundation pit, provides construction conditions for subsequent construction steps, and improves the blasting excavation effect of the blast holes by controlling the specific formation structure of the blast holes, improves the construction quality of the project, and provides a reference for similar construction modes. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these provided drawings without creative efforts.

[0045] Figure 1 It is a layout diagram of short-hole blasting holes related to the present invention;

[0046] Figure 2 It is an element diagram of a blast hole bench related to the present invention;

[0047] Figure 3 It is a schematic diagram of a charging structure related to the present invention;

[0048] Figure 4 It is a schematic diagram of a charging structure related to the present invention;

[0049] Figure 5 It is a schematic diagram of a smooth blasting hole charging structure related to the present invention;

[0050] Figure 6 It is a schematic diagram of main smooth blasting holes and smooth blasting holes related to the present invention.

[0051] Explanation of the reference numerals in the drawings:

[0052] Label Name Label Name 100 Borehole 110 Main blasting hole 120 Smooth blasting hole 101 In-hole detonator 102 Detonating fuse 103 Charging section 104 Blocking section 200 Enhanced charging section 300 Normal charging section 400 Reduced charging section 500 Detonating cord

[0053] The implementation, functional features and advantages of the present invention will be further described in conjunction with the embodiments with reference to the accompanying drawings. Detailed implementation manners

[0054] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part rather than all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0055] It should be noted that

[0056] In the embodiments of the present invention, all directional indications (such as up, down, left, right, front, back, etc.) are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0057] In the present invention, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or system including a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or system. Without further limitation, the elements defined by the statement "include..." do not exclude the existence of additional identical elements in the process, method, article or system including such element. In addition, the meaning of "and / or" appearing throughout the text includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or a solution where A and B are satisfied simultaneously.

[0058] In the present invention, unless otherwise clearly defined and limited, the terms "connect", "fix", etc. shall be understood in a broad sense. For example, "connect" can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium; it can be the communication inside two elements or the interaction relationship between two elements.

[0059] In the present invention, if there is a description involving "first", "second", etc., such description of "first", "second", etc. is only for descriptive purposes and cannot be understood as indicating or implying its relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first", "second" can expressly or implicitly include at least one such feature.

[0060] In the present invention, suffixes such as "module", "component", "part", "member" or "unit" used to represent elements are only for the convenience of explaining the present invention, and have no specific meaning in themselves. Therefore, "module", "member" or "unit" can be used interchangeably.

[0061] For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In addition, the technical solutions of each embodiment can be combined with each other, provided that those of ordinary skill in the art can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0062] The inventive concept of the present invention will be further elaborated below in conjunction with some specific embodiments.

[0063] The present invention provides an arch seat foundation pit blasting excavation structure and method.

[0064] Refer to Figures 1 to 5 , Figure 1 which is the short-hole blasting hole layout diagram related to the present invention; Figure 2 which is the hole bench element diagram related to the present invention; Figure 3 which is the schematic diagram of the charging structure related to the present invention; Figure 4 which is the schematic diagram of the charging structure related to the present invention; Figure 5 which is the schematic diagram of the smooth blasting hole charging structure related to the present invention.

[0065] In an embodiment of the present invention, as Figures 1 to 5 shown, on the first hand, the present invention provides an arch seat foundation pit blasting excavation structure, including: an existing foundation pit slope platform, the existing foundation pit slope platform includes a left bank arch seat and a right bank arch seat arranged at intervals, blasting steps to be blasted are arranged on both the left bank arch seat and the right bank arch seat, and a plurality of blast holes 100 are formed in the blasting steps to be blasted; a plurality of charging structures, the number of the charging structures is the same as that of the blast holes 100 and they are arranged in one-to-one correspondence, and each charging structure is stuffed into the corresponding blast hole 100; wherein, each blast hole 100 is inclined in the blasting step to be blasted with respect to the bottom surface of the blasting step to be blasted, and the blast holes 100 are arranged at intervals.

[0066] The technical solution of the present invention forms a secondary foundation pit that meets the construction requirements by setting blast holes on the existing foundation pit and using the blast holes to perform secondary excavation on the blasting platform of the existing foundation pit, which is beneficial to the subsequent construction of the secondary arch seat foundation pit, provides construction conditions for subsequent construction steps, and improves the blasting excavation effect of the blast holes and the construction quality of the project by controlling the specific formation structure of the blast holes, providing a reference for similar construction modes.

[0067] In one embodiment, the diameter of the orifice of the blast hole 100 is A, the diameter of the bottom of the blast hole 100 is B, and A ≤ 2B / 3.

[0068] In one embodiment, multiple blast holes 100 are distributed in a plum blossom pattern.

[0069] In one embodiment, the blast hole 100 is a shallow blasting hole; the charging structure includes: a charging section 103, the charging section 103 is packed in the shallow blasting hole, and the charging section 103 extends from the bottom of the shallow blasting hole towards the orifice of the shallow blasting hole; a plugging section 104, the plugging section 104 is packed at the orifice of the shallow blasting hole; one in-hole detonator 101, the in-hole detonator 101 is buried in the charging section 103; one detonating fuse 102, one end of the detonating fuse 102 extends into the charging section 103 and is connected to the in-hole detonator 101, and the other end of the detonating fuse 102 extends out of the charging section 103 from the orifice of the shallow blasting hole.

[0070] In one embodiment, the blast hole 100 is a deep blasting hole; the charging structure includes: a charging section 103, the charging section 103 is packed in the deep blasting hole, and the charging section 103 extends from the bottom of the deep blasting hole towards the orifice of the deep blasting hole; a plugging section 104, the plugging section 104 is packed at the orifice of the deep blasting hole; two in-hole detonators 101, the two in-hole detonators 101 are buried in the charging section 103, the two in-hole detonators 101 are arranged at intervals, each in-hole detonator 101 is connected with a detonating fuse 102, one end of each detonating fuse 102 extends into the charging section 103 and is connected to the corresponding in-hole detonator 101, and the other end of the detonating fuse 102 extends out of the charging section 103 from the orifice of the deep blasting hole.

[0071] In one embodiment, the two in-hole detonators 101 are respectively a first in-hole detonator 101 and a second in-hole detonator 101, the depth of the deep blasting hole is C, the embedding depth of the first in-hole detonator 101 is C / 3, and the embedding depth of the second in-hole detonator 101 is 2C / 3.

[0072] In one embodiment, multiple blast holes 100 are multiple main blasting holes 110 and multiple smooth blasting holes 120, multiple main blasting holes 110 are linearly and sequentially spaced along the length direction of the bench to be blasted to form a first blast hole group, multiple smooth blasting holes 120 are linearly and sequentially spaced along the length direction of the bench to be blasted to form a second blast hole group, and the first blast hole group and the second blast hole group are spaced in the width direction of the bench to be blasted.

[0073] For the convenience of understanding, a specific implementation manner is shown here:

[0074] The excavation adopts a vertical drilling form, and the blast hole 100 is arranged in a plum blossom pattern;

[0075] According to the on-site excavation height, 2m is taken as a principle during the construction of this project, and when the bench height is large, it should be excavated in benches;

[0076] The down-the-hole drill is used for drilling. Currently, a drill bit with a diameter of Φ40mm is mostly selected, so the hole diameter D = 40mm;

[0077] It is determined by the bench height (H) and the overburden depth (h). The overburden depth of the drill hole is based on the empirical formula:

[0078] Then the hole depth L = H / Sina + h

[0079] L - length of the blast hole (m)

[0080] H - bench height (m)

[0081] a - drill hole inclination angle (°)

[0082] h - overburden depth (m) (the overburden depth formula h = (0.1 - 0.15)H, in actual situation, h = 0.3 - 0.5m)

[0083] Based on the equipment capacity, working conditions, and slope gradient requirements, a suitable drill hole inclination angle can be selected. According to the selected bench height of 2m, the actual hole depth L = 2.3 - 2.5m. During construction, the depth parameters of the blast holes should be adjusted appropriately according to the actual situation to ensure that the bottom of the hole is located on the planned bench plane;

[0084] According to the empirical formula: Wbottom = (30 - 50)D; in hard and difficult-to-blast rock masses, or when the bench height H is relatively high, a larger coefficient should be taken during calculation. During construction, generally 0.8 - 1.5m is taken;

[0085] (6) Hole spacing (a) and row spacing (b)

[0086] a = (1 - 1.5)Wbottom;

[0087] b = (0.8 - 1.0)a

[0088] In this project, a = (0.8 - 1.5)m; b = (0.6 - 1.2)m;

[0089] According to the requirements of this project, the stemming length Lstem ≥ 1.2Wbottom;

[0090] According to the properties, structures, etc. of the rocks in this project area, as well as actual experience, the q value is generally taken as 0.3 - 0.4kg / m3. According to the rock properties and structures of this project, the q value is taken as: q = 0.28 - 0.35kg / m3. However, during actual operation, necessary adjustments should be made in a timely manner according to the changes in rock properties;

[0091] The type of explosive is 2# rock emulsion explosive, and the cartridge diameter is Ф25mm;

[0092] The charge amount per hole Q: Q = qV

[0093] In the formula:

[0094] Q — Charge amount per blast hole, kg

[0095] q — Explosive consumption per unit volume of rock, kg / m3

[0096] V — Volume of rock to be blasted, m3, V = Lab

[0097] L — Hole depth

[0098] W — Resistance line

[0099] a — Hole spacing

[0100] b — Row spacing

[0101] Calculation of charge amount for multi-row blast hole blasting. The charge amount per hole in the front row is Q = qaLW; the charge amount per hole in the second row of holes is Q = qabL. Due to the uneven height of the excavation bench, the resistance line changes at any time, and the hardness of the rock is different, etc. The charge amount per single hole should be calculated according to the on-site situation to obtain a reasonable charge amount. When the unit explosive consumption q is 0.35 kg / m3, the selection of each parameter in the following table can be referred to;

[0102]

[0103] Adopt a continuous decoupled charge structure (see charge structure Figures 4 - 6 ): Before charging, the charge amount per single hole should be calculated. When charging, gently put the explosive into the blast hole. The upper part at the bottom of the blast hole is slightly larger, and the hole mouth is smaller, which is 2 / 3 of the bottom of the hole. Use stone powder or clay (the water content of clay is 10% - 30%.) as the stemming material;

[0104] As another implementation method of this embodiment:

[0105] (1) Arrangement method of blast holes 100

[0106] Adopt a vertical drilling form, and the blast holes 100 are arranged in a plum blossom pattern. The arrangement form is similar to that of short-hole blasting.

[0107] (2) Bench height

[0108] According to the drawing design, the bench height is H = 10m. According to the rock conditions and the surrounding environment of the blasting area, it is designed as: H = 7m, H = 10m.

[0109] (3) Selection of the value of unit explosive consumption q

[0110] q refers to the amount of explosive consumed per unit volume (or weight) of the rock in the blasting medium. Its value is related to factors such as rock properties, explosive properties, borehole diameter, slope requirements, etc. Considering various factors comprehensively, it is selected and adjusted based on experience, tests, and data from similar projects. According to the rock hardness and fracture development of this project, the specific charge is taken as: q = 0.25 - 0.40 kg / m 3 , and it will be appropriately adjusted according to the trial blasting during the construction process.

[0111] (4) Selection of the hole diameter D and the bottom resistance line W_bottom

[0112] The diameter of the down-the-hole drill bit used in this project is Φ90. Based on past construction experience, taking 25 - 50 times the hole diameter, it is more appropriate to select W_bottom = 2.5 - 3.0 m for this project. During blasting operations, it can be appropriately adjusted according to the blasting effect of the previous blast.

[0113] (5) Hole depth L and overbreak depth h

[0114] The hole depth is determined according to the actual terrain, facilitating the formation of a bench working face for the next blasting, and the surrounding environment on site. The bench height H takes two values of 7 m and 10 m. The overbreak depth takes 8 - 12 times the hole diameter. In this project, according to the actual construction situation, h = 0.5 m is taken.

[0115] (6) Selection of the hole spacing a and the row spacing b

[0116] The hole spacing a refers to the distance between the centerlines of two adjacent holes in the same row of deep holes. Since this project is a cutting excavation, combining actual experience and the empirical formula a = mW_bottom (m is the hole density coefficient of 100, m = 0.8 - 1.4 m), when the bench height of this project is 5 m, the hole spacing a = 2.5 - 3.0 m is taken, and the row spacing b is calculated according to the formula b = (0.8 - 1.0)a, taking the row spacing b = 2.0 - 2.5 m; when the bench height is 10 m, the hole spacing a = 3.0 - 3.5 m is taken, and the row spacing b is calculated according to the formula b = (0.8 - 1.0)a, taking the row spacing b = 2.5 - 3.0 m. It can be appropriately adjusted according to different topographies and to meet the requirements of the surrounding environment on site.

[0117] (7) Explosive type

[0118] The variety of deep-hole charge is emulsion explosive (cartridge diameter is Ф70).

[0119] (8) Charge amount per hole (Q)

[0120] According to the empirical formula Q = q·a·b·H, where q is the unit consumption of standard explosive, a is the hole spacing, b is the row spacing, and H is the bench height, the charge amount per hole Q5 = 11.5 kg (taking H = 5.0 m, a = 3.0 m, b = 2.5 m, q = 0.30 kg) and Q10 = 36 kg (taking H = 10.0 m, a = 4.0 m, b = 3.0 m, q = 0.30 kg) can be calculated.

[0121] (9) Charge structure

[0122] The charge in blast hole 100 adopts a continuous columnar charge structure. For deep holes, 2 detonators are used, and the detonators are placed at the 1 / 3 and 2 / 3 positions of the charge column respectively. During the charging process, there are no sundries in the hole, and the charge is continuous to naturally compact the explosive to ensure the charge density. The backfill is sealed with stemming. During the backfill process, the blocking material should be continuous (not in an air-supported state) and naturally compacted to ensure the blocking quality.

[0123] According to the requirements of this project, the stemming length is generally 20 - 30 times the hole diameter according to experience. Depending on the on-site terrain and surrounding environment conditions, the stemming length is 3 - 4.5 m.

[0124] The specific blasting-related parameters are shown in the following table

[0125]

[0126]

[0127] The above parameters are adjusted according to the actual on-site geological conditions and the trial blasting effect. When the burden is too large, according to the design requirements, a hydraulic breaker or short-hole blasting is used to trim the burden to within the allowable value of the designed blasting parameters.

[0128] As an option in this embodiment, in the smooth blasting design:

[0129] (1) Bench height H: It is the same as the designed slope height.

[0130] (2) Borehole diameter D: Take D = 90 mm.

[0131] (3) Borehole inclination: It is determined according to the design requirements of the slope gradient.

[0132] (4) Minimum burden Ws

[0133] The minimum burden Ws of smooth blasting is a key parameter affecting the smooth blasting effect.

[0134] Ws = (15 - 25)D = 1.35 - 2.25 m, take Ws = 1.8 m.

[0135] (5) Blast hole 100 spacing as

[0136] The spacing of smooth blasting holes 100 can be selected according to the following formula: \(a_{smooth}=(10 - 20)D = 0.9 - 1.8m\). Take the smaller value in rocks with relatively developed joints and fissures, and the larger value in rocks with good integrity. Take \(a_{smooth}=1.5m\).

[0137] (6) Uncoupling charge coefficient \(m\): \(m = 2 - 5\), take \(2.8\) this time.

[0138] (7) Linear charge density \(q_{smooth}\)

[0139] Take \(q_{smooth}=0.3 - 0.45kg / m\), and the bottom \(q_{bottom}=(1.2 - 2.0)q_{smooth}\).

[0140] (8) Length of smooth blasting hole 120 \(L_{smooth}\): \(L_{smooth}=(H + h) / \sin\theta\), where \(\theta\) is the drilling inclination angle, take \(53^{\circ}\), \(h\) is the overbreak depth, take \(0.5m\), \((H + h) / \sin\theta = 11.0\div\sin53^{\circ}=13.6m\).

[0141] Where \(\theta\) - slope angle

[0142] (9) Charge amount of hole 100 \(Q_{smooth}=q_{smooth}L_{smooth}\)

[0143] (10) Charge structure

[0144] The smooth blasting holes 120 adopt uncoupled charging. Bind the \(\varphi32mm\) emulsion explosive cartridges to the detonating cord 500 and bamboo strips. The cartridges are close to the detonating cord 500 and are charged in three sections, namely: the weakening charge section 400 at the top \(2.0m\), the normal charge section 300 in the middle;

[0145] The strengthening charge section 200 at the bottom (\(10m\) bench) \(2m\), and the strengthening charge section 2001.2m for the \(5m\) bench;

[0146] (11) Charging and stemming

[0147] The stemming length \(L_{stem}\geq1.5m\), take \(2.0m\) this time.

[0148] Strengthen the charge at the bottom of the hole. Before charging, calculate the charging linear density and the charge amount of a single hole. Bind the explosive evenly and firmly to the detonating cord 500, and then carefully put it into the hole 100. The stemming material uses woven bags and kraft paper to be placed at the lower part of the stemming section 104, and then backfill drill cuttings or clay. The stemming length is not less than \(1.5m\).

[0149] Summary table of design parameters for smooth blasting of slopes

[0150]

[0151] The technical solution of the present invention forms a secondary excavation on the blasting platform of the existing foundation pit by setting blast holes 100 on the existing foundation pit, forming a secondary foundation pit that meets the construction requirements, which is conducive to the subsequent construction of the secondary arch seat foundation pit, provides construction conditions for subsequent construction steps, and improves the blasting excavation effect of the blast holes 100 by controlling the specific formation structure of the blast holes 100, improves the construction quality of the project, and provides a reference for similar construction modes.

[0152] Continue to refer to Figures 1 to 5 and refer to Figure 6 , Figure 6 is a schematic diagram of the main smooth blasting holes 100 and smooth blasting holes 120 involved in the present invention.

[0153] In a second aspect, in an embodiment of the present invention, as Figures 1 to 6 shown, the present invention provides a method for blasting excavation of an arch seat foundation pit for forming the blasting excavation structure of the arch seat foundation pit as described above. The method includes:

[0154] Step S100: Set the minimum burden on the bottom side of the blasting bench and obtain the length of the minimum burden;

[0155] Step S200: Set the upper bench line on the top side of the blasting bench and obtain the length of the upper bench line;

[0156] Step S300: Obtain the slope angle of the blasting bench according to the length of the minimum burden and the length of the upper bench line;

[0157] Step S400: Preset the overbreak depth of the blast holes 100;

[0158] Step S500: Drill holes on the surface of the blasting bench to form blast holes 100 according to the slope angle of the blasting bench, the height of the blasting bench, and the overbreak depth of the blast holes 100;

[0159] Step S600: Obtain the charge amount according to the type of the blast holes 100;

[0160] Step S700: Fill the charge structure into the blast holes 100 according to the charge amount to form the blasting excavation structure of the arch seat foundation pit.

[0161] In an embodiment, the type of the blast holes 100 is multi-row blast holes 100. The multi-row blast holes 100 include the front-row blast holes 100 and the second-row blast holes 100 arranged at intervals with the front-row blast holes 100. The front-row blast holes 100 are composed of multiple blast holes 100 arranged at intervals, and the second-row blast holes 100 are composed of multiple blast holes 100 arranged at intervals;

[0162] The step of obtaining the charge amount according to the type of the blast holes 100 includes:

[0163] Step B100: Obtain the charge amount of the front row of blast holes 100 according to the unit explosive consumption, the spacing between the blast holes 100 in the front row of blast holes 100, the hole depth of the front row of blast holes 100, and the minimum burden;

[0164] Step B200: Obtain the charge amount of the second row of blast holes 100 according to the unit explosive consumption, the spacing between the blast holes 100 in the second row of blast holes 100, the hole depth of the second row of blast holes 100, and the spacing between the second row of blast holes 100 and the front row of blast holes 100.

[0165] In one embodiment, the type of the blast hole 100 is a smooth blasting hole 120;

[0166] Step C100: The steps of setting the minimum burden at the bottom side of the bench to be blasted and obtaining the length of the minimum burden include:

[0167] Step C200: Obtain the length of the minimum burden of the smooth blasting hole 120 according to the aperture of the smooth blasting hole 120;

[0168] Wherein, the aperture of the smooth blasting hole 120 is D_light, and the length of the minimum burden of the smooth blasting hole 120 is W_light, W_light = β * D_light, 15 ≤ β ≤ 25.

[0169] For easy understanding, a specific implementation manner is shown here:

[0170] Use a crawler-mounted down-the-hole drill, strictly excavate the slope ratio according to the construction drawing. After measuring and lofting the hole positions, drill the main blast holes 110 and pre-splitting holes. During the drilling process, ensure that the longitudinal and transverse errors of the hole positions do not exceed ±50 mm, and the elevation error is strictly controlled to exceed the buried depth of large-diameter boulders. Ensure that the support of the drill is firm and stable, and there should be no shaking during the hole-making process. Use an air compressor for air supply, ensure that the dry hole without water is formed to keep the drill pipe aligner intact, and the diameter of the bit used shall not be less than the designed aperture. Drill layer by layer from top to bottom, and strictly control the drilling speed, air pressure, and propulsion according to the performance of the drill and the actual situation of the underlying layer to prevent drilling distortion, diameter change, cave-in or other accidents. After the air compressor starts, start the down-the-hole drill. According to the terrain and geological conditions, adjust the drill angle of the drill before drilling. After drilling, pay attention to the control of the hole depth, and it must exceed the bottom layer of the large boulder layer by 0.5 - 1.0 m. Avoid secondary alignment drilling and fully meet the requirements of the pilot hole. Arrange a special person to be responsible for the drilling process, and make detailed records of the geological conditions, hole opening, hole formation, and hole depth. During the drilling process, timely feedback and take measures for the formation change, drilling state, groundwater, and some special situations of each hole.

[0171] In the area where the crawler drill cannot operate due to terrain reasons, use a manual air drill for drilling or use mechanical direct excavation. When using manual drilling, the depth of each excavation shall not be greater than 4 m, and the precautions are the same as those for the crawler drill.

[0172] After the hole inspection by the blasting company, a blasting plan is designed. According to the geological conditions and the blasting design plan, and considering the requirements for slope stability and environmental conditions, a reasonable blasting method is adopted to organize the blasting construction. During the blasting construction process, the charging is carried out strictly in accordance with the blasting design requirements, and the charging is controlled to ensure the slope ratio of the slope and reduce the disturbance to the foundation and slope stability. And do a good job in safety warning and safety liaison work, and strictly prohibit other personnel from entering the blasting area.

[0173] For the blasting of the second excavation slope of the left-bank downstream arch seat, the slag stones of the first three levels of slopes are successively cleared to the bottom of the downstream side arch seat foundation pit by an excavator. When the slope is excavated to the fourth level of slope, the excavator is used to uniformly discard the slag to the downstream river channel of the Jinghe River. After the excavation of the sixth level of slope is completed, the self-unloading truck is used to transport the slag to the designated slag disposal site through the Jinghe River channel.

[0174] For the blasting of the fifth and sixth levels of slopes on the river-facing side, due to topographical reasons, the excavator cannot carry out mechanical slag removal, and manual cleaning of the slag stones to the lower Jinghe River is adopted. When using manual slag cleaning, the slag cleaning personnel should strictly wear safety protection supplies such as safety helmets, anti-slip shoes, safety ropes, and safety belts in accordance with the project safety management measures.

[0175] It should be noted that the serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages and disadvantages of the embodiments. The above embodiments are only optional embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural or equivalent process transformation made by using the description and drawings of the present invention under the inventive concept of the present invention, or directly or indirectly applied to other related technical fields, are all included in the patent protection scope of the present invention.

Claims

1. A blasting excavation structure for an arch seat foundation pit, characterized in that, Comprising: An existing foundation pit slope platform, the existing foundation pit slope platform includes a left bank arch seat and a right bank arch seat arranged at intervals, blasting steps are provided on both the left bank arch seat and the right bank arch seat, and a plurality of blast holes are formed in the blasting steps; A plurality of charging structures, the number of the charging structures is the same as that of the blast holes and they are arranged in one-to-one correspondence, and each charging structure is stuffed into the corresponding blast hole; Wherein, each blast hole is inclinedly arranged in the blasting step with respect to the bottom surface of the blasting step, and the blast holes are arranged at intervals, the orifice diameter of the blast hole is A, the bottom diameter of the blast hole is B, and A ≤ 2B / 3.

2. The blasting excavation structure of the arch seat foundation pit according to claim 1, wherein, The plurality of blast holes are distributed in a plum blossom shape.

3. The arch seat foundation pit blasting excavation structure according to claim 1 or 2, characterized in that, The blast holes are shallow blasting holes; The charging structure includes: A charging section, the charging section is stuffed into the shallow blasting hole, and the charging section extends from the bottom of the shallow blasting hole towards the orifice of the shallow blasting hole; A plugging section, the plugging section is stuffed at the orifice of the shallow blasting hole; One in-hole detonator, the in-hole detonator is buried in the charging section; One detonating fuse, one end of the detonating fuse extends into the charging section and is connected to the in-hole detonator, and the other end of the detonating fuse extends out of the charging section from the orifice of the shallow blasting hole.

4. The arch seat foundation pit blasting excavation structure according to claim 1 or 2, characterized in that, The blast holes are deep blasting holes; The charging structure includes: A charging section, the charging section is stuffed into the deep blasting hole, and the charging section extends from the bottom of the deep blasting hole towards the orifice of the deep blasting hole; A plugging section, the plugging section is stuffed at the orifice of the deep blasting hole; Two in-hole detonators, the two in-hole detonators are buried in the charging section, the two in-hole detonators are arranged at intervals, each in-hole detonator is connected with a detonating fuse, one end of each detonating fuse extends into the charging section and is connected to the corresponding in-hole detonator, and the other end of the detonating fuse extends out of the charging section from the orifice of the deep blasting hole.

5. The blasting excavation structure of the arch seat foundation pit according to claim 4, characterized in that, The two in-hole detonators are respectively a first in-hole detonator and a second in-hole detonator, the hole depth of the deep blasting hole is C, the embedding depth of the first in-hole detonator is C / 3, and the embedding depth of the second in-hole detonator is 2C / 3.

6. The blasting excavation structure of the arch seat foundation pit according to claim 1, characterized in that, The plurality of blast holes are a plurality of main blast holes and a plurality of smooth blasting holes, the plurality of main blast holes are linearly arranged at intervals in sequence along the length direction of the blasting step to form a first blast hole group, the plurality of smooth blasting holes are linearly arranged at intervals in sequence along the length direction of the blasting step to form a second blast hole group, and the first blast hole group and the second blast hole group are arranged at intervals in the width direction of the blasting step.

7. A method for blasting excavation of an arch abutment foundation pit, characterized in that, For forming the arch seat foundation pit blasting excavation structure according to any one of claims 1 to 6, the method includes: Setting a minimum resistance line at the bottom side of the blasting step and obtaining the length of the minimum resistance line; Setting a step upper brow line at the top side of the blasting step and obtaining the length of the step upper brow line; Obtaining the slope angle of the blasting step according to the length of the minimum resistance line and the length of the step upper brow line; Presetting the over-depth of the blast hole; Drilling the blast holes on the surface of the blasting step according to the slope angle of the blasting step, the height of the blasting step and the over-depth of the blast hole. Obtain the charge amount according to the type of the blast hole; Fill the blast hole with the charging structure according to the charge amount to form the blasting excavation structure of the arch seat foundation pit.

8. The method for blasting excavation of the arch seat foundation pit according to claim 7, characterized in that, The type of the blast hole is a multi-row blast hole. The multi-row blast hole includes a front row blast hole and a second row blast hole arranged at intervals with the front row blast hole. The front row blast hole is composed of a plurality of the blast holes arranged at intervals, and the second row blast hole is composed of a plurality of the blast holes arranged at intervals; The step of obtaining the charge amount according to the type of the blast hole includes: Obtain the charge amount of the front row blast hole according to the unit explosive consumption, the spacing between the blast holes in the front row blast hole, the hole depth of the front row blast hole, and the minimum burden; Obtain the charge amount of the second row blast hole according to the unit explosive consumption, the spacing between the blast holes in the second row blast hole, the hole depth of the second row blast hole, and the spacing between the second row blast hole and the front row blast hole.

9. The method for blasting excavation of the arch seat foundation pit according to claim 7, characterized in that, The type of the blast hole is a smooth blasting hole; The step of setting a minimum burden at the bottom side of the bench to be blasted and obtaining the length of the minimum burden includes: Obtain the length of the minimum burden of the smooth blasting hole according to the hole diameter of the smooth blasting hole; Among them, the aperture of the smooth blasting hole is D 光 , and the length of the minimum burden of the smooth blasting hole is W 光 , W 光 = β * D 光 , where 15 ≤ β ≤ 25.

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