Local blasting demolition method for unqualified bridge piers

Abstract

The application discloses a method for locally blasting and demolishing an unqualified pier, and the method steps are as follows: S1, determining a blasting collapse direction according to the peripheral environment of the unqualified pier; S2, designing a blasting cut according to the collapse direction: a blasting cut with a height of h is formed upward at a pier cap of the unqualified pier away from the lower end of the unqualified pier, a blasting front end cut of the blasting cut is provided with a plurality of first cutting areas and first hole distribution areas which are distributed at intervals, and the first cutting areas penetrate through the side walls of the unqualified pier; a blasting side cut of the blasting cut is provided with second cutting areas with decreasing heights, and the second cutting areas are provided with second hole distribution areas on one side in a cutting direction; S3, designing blasting blast holes; S4, calculating the charge quantity of the blasting blast holes; and S5, designing an initiation network.The demolition method shortens the pier demolition period and reduces the demolition cost, and ensures that the pier cap and the pile foundation under the pier are not damaged.

Description

Technical Field

[0001] The invention relates to the technical field of blasting demolition, in particular to a method for local blasting demolition of unqualified bridge piers. Background Art

[0002] The piers of existing super-large bridges are mostly hollow structures with a capping platform at the bottom. Multiple piers are usually set on the top of the capping platform, and pile foundations are set at the bottom of the capping platform. When a pier needs to be demolished due to unqualified construction, it is necessary to ensure that the pier to be demolished will not affect the capping platform, pile foundation and other piers located on the capping platform during the demolition process.

[0003] The existing demolition method for this type of situation mainly involves cutting the bridge pier into several blocks using a rope saw, then hoisting the blocks to the ground using a tower crane, and then using a breaker hammer for secondary crushing. This method is not only expensive but also takes a long time to complete.

[0004] Blasting demolition is one way to shorten the pier demolition process. However, existing blasting demolition methods can easily damage the caps and pile foundations during the demolition process, making it impossible to re-build the piers using the existing caps and pile foundations. Therefore, there is an urgent need to develop a blasting demolition method that can shorten the pier demolition process and reduce demolition costs while preserving the caps and pile foundations beneath the piers. Summary of the Invention

[0005] Based on the technical problems existing in the background technology, the present invention proposes a method for local blasting demolition of unqualified bridge piers, which shortens the bridge pier demolition period and reduces the demolition cost while ensuring that the abutment and pile foundation under the bridge pier are not damaged.

[0006] The method for local blasting demolition of unqualified bridge piers proposed in the present invention comprises the following steps:

[0007] S1: Determine the blasting collapse direction based on the surrounding environment of the unqualified bridge pier;

[0008] S2: Design of blasting cuts according to collapse direction

[0009] A blasting cut with a height of h is opened upwards at a position h1 from the base of the unqualified pier, wherein the blasting cut is located at the front end of the blasting face in the collapse direction and has a plurality of first cutting areas and first hole distribution areas spaced apart from each other, wherein the first cutting area penetrates the side wall of the unqualified pier;

[0010] The blasting side cuts on both sides of the collapse direction are provided with a second cutting area with decreasing height, and the second cutting area is provided with a second hole distribution area on one side of the cutting direction;

[0011] The blasting rear end face incision of the blasting incision located at the rear end face in the collapse direction is cut by a rope saw to form a blasting incision boundary line, and the distance from the blasting incision boundary line of the blasting rear end face incision to the cap is greater than the distance from the lower end of the blasting front end face incision to the cap;

[0012] A plurality of blasting holes are opened in both the first hole arrangement area and the second hole arrangement area;

[0013] S3: Design of blasting holes;

[0014] S4: Calculation of charge for blasting holes;

[0015] S5: Design of the detonation network.

[0016] Preferably, the height of the blasting front face cut in S2 is:

[0017]

[0018]

[0019] Where: h is the height of the cut at the front end of the blasting; H is the vertical height from the top of the unqualified pier to the cap at its lower end; a is the width of the top of the two sides of the blasting cut in the direction of collapse; b' is the width of the bottom of the two sides of the blasting cut in the direction of collapse; Hc is the height of the center of gravity of the unqualified pier;

[0020] The width of the first cutting area of ​​the blasting gap located at the front end of the collapse direction is:

[0021] b1=b-2×b2

[0022] Wherein: b1 is the width of the first cutting area at the front end of the blasting gap in the direction of collapse; b is the width of the front end of the blasting gap in the direction of collapse; b2 is the width of the first hole arrangement area;

[0023] The width of the second cutting area on both sides of the blasting gap in the collapse direction is:

[0024] b5=b'-b3-b4-b6

[0025] Wherein: b5 is the width of the second cutting area on both sides of the blasting notch in the direction of collapse; b3 is the depth of the notch at the rear end of the blasting; b4 is the horizontal distance from the short side of the second cutting area to the boundary line of the blasting notch at the rear end of the blasting notch in the direction of collapse; b6 is the width of the second hole arrangement area;

[0026] The height of the long side of the second cutting area on both sides of the blasting notch in the direction of collapse is the same as the notch height of the front end face of the blasting notch in the direction of collapse, and the height h3 of the short side of the second cutting area on both sides of the blasting notch in the direction of collapse is greater than the vertical distance h2 from the incision of the rear end face of the blasting notch to the bottom edge of the second cutting area.

[0027] Preferably, the depth b3 of the blasting rear end face cut is the same as the horizontal distance b4 from the short side of the second cutting area to the blasting cut boundary line of the rear end face of the blasting cut in the collapse direction; the width b6 of the second hole layout area is the same as the wall thickness of the blasting front end face cut.

[0028] Preferably, the height h3 of the short side of the second cutting area on both sides of the blasting gap in the collapse direction is 1.8-2.2 times the vertical distance h2 from the rear end face cut to the bottom edge of the second cutting area.

[0029] Preferably, the width b2 of the first hole distribution area is the same as the wall thickness on both sides in the blasting direction.

[0030] Preferably, the blast holes in the first hole arrangement area and the second hole arrangement area are arranged in such a way that holes in adjacent vertical directions are staggered, and holes in the same vertical direction are distributed at equal intervals.

[0031] Preferably, the calculation method of the blasthole spacing h4 in the same vertical direction is:

[0032] h4=(1.1~1.2)W

[0033] The calculation method of the horizontal distance b7 between the center axes of adjacent vertical blastholes is:

[0034] b7=(0.5~0.8)h4

[0035] The charge Q of each blasthole is calculated as:

[0036] Q=q×v

[0037] Where: W is the resistance line, with a value range of 0.3-0.5m; q is the comprehensive explosive consumption; v is the burden area of ​​a single blasting hole.

[0038] Beneficial technical effects of the present invention:

[0039] (1) The present invention adopts a combination of rope saw cutting and blasting demolition to shorten the time and reduce the demolition cost of the partial demolition of unqualified bridge piers while ensuring that the abutments and pile foundations under the bridge piers are not damaged, thereby facilitating the subsequent reconstruction of the bridge piers.

[0040] (2) The present invention determines the height and width of the blasting cut by designing a calculation method for the blasting cut parameters. Combined with the design of the blasting hole parameters in the hole distribution area, it ensures that the pier cap and pile foundation below the pier will not be damaged while the pier is being demolished by blasting.

[0041] (3) In the present invention, the height of the short side of the second cutting area on both sides of the blasting notch in the direction of collapse is 1.8-2.2 times the vertical distance from the blasting rear end face cut to the bottom edge of the second cutting area. The depth of the blasting rear end face cut is the same as the horizontal distance from the short side of the second cutting area to the blasting notch boundary line on the rear end face of the blasting notch in the direction of collapse. This arrangement further ensures the effectiveness of blasting demolition and protects the cap and pile foundation. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a schematic diagram of the blasting cutout structure of the front end face of the unqualified bridge pier in the blasting direction proposed by the present invention;

[0043] Figure 2 This is a schematic diagram of the blasting cut structure on both sides of the blasting direction of the unqualified bridge pier proposed by the present invention;

[0044] Figure 3 This is a schematic diagram of the distribution of blasting holes proposed in the present invention;

[0045] Figure 4 This is a cross-sectional view of the remaining bridge piers after the unqualified bridge piers proposed by the present invention are demolished by blasting;

[0046] Figure 5 This is a schematic diagram of the detonation network proposed by the present invention;

[0047] Figure 6 This is a physical picture of the unqualified bridge pier proposed in the present invention after demolition by blasting.

[0048] In the figure: 1-bridge pier, 11-blasting front end face cut, 111-first hole layout area, 112-first cutting area, 12-blasting side cut, 121-second hole layout area, 122-second cutting area, 13-blasting rear end face cut, 14-center of gravity, 2-cap, 3-pile foundation, 4-blasting hole. DETAILED DESCRIPTION

[0049] Example

[0050] Reference Figures 1-4 The object to be demolished is Pier 16 on the left span of a particularly large bridge. According to relevant design drawings and on-site inspections, the pier is hollow and has been constructed to the first internal bulkhead. Based on the top of the abutment, the pier is approximately 22.5 meters high. The bottom 2.0 meters high is a solid reinforced concrete structure.

[0051] The method for locally blasting and demolishing the unqualified pier 1 comprises the following steps:

[0052] S1: determining the blasting collapse direction according to the peripheral environment of the unqualified pier 1;

[0053] S2: designing the blasting cut according to the collapse direction

[0054] According to the needs, the blasting cut is opened upward at the position of the unqualified pier 1, which is h1=3.0m away from the lower end of the pier, and the height of the blasting cut is h, wherein the blasting cut is provided with a plurality of first cutting areas 112 and first drilling areas 111 which are distributed at intervals and are arranged on the blasting front end face cut 11 of the front end face of the collapse direction, and the first cutting areas 112 penetrate the side wall of the unqualified pier 1;

[0055] The blasting cut is provided with second cutting areas 122 which are arranged on one side of the cutting direction and are arranged on the blasting side cut 12 of the two side edges of the collapse direction, and the second cutting areas 122 are arranged on one side of the cutting direction and are arranged on the second drilling areas 121;

[0056] The blasting rear end face cut 13 of the blasting cut which is arranged on the rear end face of the collapse direction is cut off by a rope saw to form a blasting cut boundary line, and the distance from the blasting cut boundary line of the blasting rear end face cut 13 to the pile cap 2 is greater than the distance from the lower end of the blasting front end face cut 11 to the pile cap 2;

[0057] A plurality of blasting blast holes 4 are arranged in the first drilling areas 111 and the second drilling areas 121;

[0058] The height of the blasting front end face cut 11 in S2 is:

[0059]

[0060]

[0061] Wherein: h is the height of the blasting front end face cut 11, which is calculated to be 6m; H is the vertical height from the top of the unqualified pier 1 to the pile cap 2 at the lower end of the pier, which is 22.4m; a is the width of the two side edges of the blasting cut at the top of the collapse direction, which is 8m; b' is the width of the two side edges of the blasting cut at the bottom of the collapse direction, which is 8m; Hc is the height of the center of gravity 14 of the unqualified pier 1, which is calculated to be 11.2m. The size of the upper and lower cross sections of the pier of the present application is the same, and the blasting demolition method of the present application is also applicable to the pier with different sizes of upper and lower cross sections.

[0062] The width of the first cutting area 112 of the blasting cut which is arranged on the front end face of the collapse direction is:

[0063] b1=b-2×b2

[0064] Wherein: b1 is the width of the first cutting area 112 of the blasting cut located at the front end face of the collapse direction, which is calculated as 6.1 m; b is the width of the blasting cut located at the front end face of the collapse direction, which is taken as 8.5 m; b2 is the width of the first drilling area 111, specifically, the width b2 of the first drilling area 111 is the same as the wall thickness of the side edges of the blasting direction, since the inside of the pier is a variable cross-section, the wall thickness at the cut is taken as the equivalent value of 1.2 m, i.e. b2=b3=b6=1.2 m;

[0065] The width of the second cutting area 122 of the blasting cut located at the side edges of the collapse direction is:

[0066] b5=b'-b3-b4-b6

[0067] Wherein: b5 is the width of the second cutting area 122 of the blasting cut located at the side edges of the collapse direction, which is calculated as 4.4 m; b3 is the depth of the blasting rear end face cut 13, which is taken as 1.2 m; b4 is the horizontal distance from the short side of the second cutting area 122 to the blasting cut boundary line of the blasting cut located at the rear end face of the collapse direction, as a preferred scheme of the present application, the depth b3 of the blasting rear end face cut 13 is the same as the horizontal distance b4 from the short side of the second cutting area 122 to the blasting cut boundary line of the blasting cut located at the rear end face of the collapse direction, which is taken as 1.2 m; b6 is the width of the second drilling area 121, which is the same as the wall thickness of the blasting front end face cut 11, and is taken as 1.2 m;

[0068] The long side height of the second cutting area 122 of the blasting cut located at the side edges of the collapse direction is the same as the cut height of the blasting cut located at the front end face of the collapse direction, and the short side height h3 of the second cutting area 122 of the blasting cut located at the side edges of the collapse direction is greater than the vertical distance h2 from the blasting rear end face cut 13 to the bottom edge of the second cutting area 122; specifically, the short side height h3 of the second cutting area 122 of the blasting cut located at the side edges of the collapse direction is 1.8-2.2 times the vertical distance h2 from the blasting rear end face cut 13 to the bottom edge of the second cutting area 122, and the present application takes h3=2h2=2.4 m, wherein the vertical distance h2 from the blasting rear end face cut 13 to the bottom edge of the second cutting area 122 is the same as the depth b3 of the blasting rear end face cut 13, both of which are 1.2 m.

[0069] S3: Design of the blasting hole 4

[0070] The arrangement mode of the blasting hole 4 in the first drilling area 111 and the second drilling area 121 is both staggered arrangement of adjacent vertical holes, and the holes in the same vertical direction are distributed at equal intervals, and the present scheme designs 2 rows of holes.

[0071] The calculation mode of the hole spacing h4 in the same vertical direction is:

[0072] h4=(1.1~1.2)W

[0073] The calculation method of the horizontal distance b7 between the center axes of adjacent vertical blastholes is:

[0074] b7=(0.5~0.8)h4.

[0075] Where: W is the resistance line, with a range of 0.3-0.5m. In this solution, the value is 0.45m. After calculation, the spacing h4 between blastholes in the same vertical direction is 0.5m, and the horizontal distance b7 between the center axes of adjacent blastholes in the vertical direction is 0.3m. The specific blasthole parameters are shown in Table 1.

[0076] Table 1 Blasting hole arrangement parameters

[0077]

[0078] S4: Calculation of blast hole charge

[0079] The charge Q of each blasthole is calculated as:

[0080] Q=q×v

[0081] Where: q is the comprehensive explosive consumption, which is 1.2kg / m 3 v is the burden area of ​​a single blast hole, which is 0.36m 3 , after calculation, the charge Q of each blasthole is 432g. The specific charge parameters are shown in Table 2.

[0082] Table 2 Charge quantity of blasting holes

[0083]

[0084] S5: Design of the detonation network.

[0085] The explosives used in this blasting are emulsion explosives, and the detonators are millisecond delay detonator detonators. To ensure smooth detonation, the detonator sections in each blast hole are shown in Table 3. The detonation network diagram is shown in Figure 5 shown.

[0086] Table 3 Blasting network design summary

[0087]

[0088]

[0089] In addition, in order to further protect the piers, pile foundations and surrounding buildings during the blasting and demolition process, a protective design was also carried out. In order to prevent flying rocks from blasting, in addition to the protection of the surrounding protected piers, the blasting area must be strictly protected. The protection method is to cover the protective hanging palm mats (processed with iron wire) or flexible protective materials such as earthen cloth and wire mesh. In each blasting area, a protection method of covering with 3 layers of flexible protective materials such as palm mats or earthen cloth and one layer of wire mesh is adopted to ensure strict control of flying rocks; flexible protective materials such as hanging bamboo fences or quilts, geotextiles, etc. are used for safety protection in the range of the blasting incision height corresponding to the adjacent piers and within the range of 2.0m above and below the blasting incision height.

[0090] Reference Figure 6 , which is a real picture of the unqualified bridge piers after demolition by blasting using the method of the present invention. It can be seen from the figure that the method of the present invention has a good demolition effect and will not damage the abutment and pile foundation.

[0091] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. The method of local blasting demolition of unqualified bridge piers is characterized by: The steps are as follows: S1: Determine the blasting collapse direction based on the surrounding environment of the unqualified bridge pier; S2: Design of blasting cuts according to collapse direction A blasting cut with a height of h is opened upwards at a position h1 from the base of the unqualified pier, wherein the blasting cut is located at the front end of the blasting face in the collapse direction and has a plurality of first cutting areas and first hole distribution areas spaced apart from each other, wherein the first cutting area penetrates the side wall of the unqualified pier; The blasting side cuts on both sides of the collapse direction are provided with a second cutting area with decreasing height, and the second cutting area is provided with a second hole distribution area on one side of the cutting direction; The blasting rear end face incision of the blasting incision located at the rear end face in the collapse direction is cut by a rope saw to form a blasting incision boundary line, and the distance from the blasting incision boundary line of the blasting rear end face incision to the cap is greater than the distance from the lower end of the blasting front end face incision to the cap; A plurality of blasting holes are opened in both the first hole arrangement area and the second hole arrangement area; S3: Design of blasting holes; S4: Calculation of charge for blasting holes; S5: Design of the detonation network; The height of the cut at the front end of the blasting in S2 is: Where: h is the height of the front face cut at the blasting front; H is the vertical height from the top of the unqualified pier to the pedestal at its lower end; a is the width of the top of the two sides of the blasting cut in the direction of collapse; b' is the width of the bottom of the two sides of the blasting cut in the direction of collapse; Hc is the height of the center of gravity of the unqualified pier.

2. The method for local demolition of unqualified bridge piers by blasting according to claim 1, characterized in that: The width of the first cutting area of ​​the blasting gap in S2, located at the front face of the collapse direction, is: b1=b-2×b2 Wherein: b1 is the width of the first cutting area at the front end of the blasting gap in the direction of collapse; b is the width of the front end of the blasting gap in the direction of collapse; b2 is the width of the first hole arrangement area; The width of the second cutting area on both sides of the blasting gap in the collapse direction is: b5=b'-b3-b4-b6 Wherein: b5 is the width of the second cutting area on both sides of the blasting notch in the direction of collapse; b3 is the depth of the notch at the rear end of the blasting; b4 is the horizontal distance from the short side of the second cutting area to the boundary line of the blasting notch at the rear end of the blasting notch in the direction of collapse; b6 is the width of the second hole arrangement area; The height of the long side of the second cutting area on both sides of the blasting notch in the direction of collapse is the same as the notch height of the front end face of the blasting notch in the direction of collapse, and the height h3 of the short side of the second cutting area on both sides of the blasting notch in the direction of collapse is greater than the vertical distance h2 from the incision of the rear end face of the blasting notch to the bottom edge of the second cutting area.

3. The method for local demolition of unqualified bridge piers according to claim 2, characterized in that: The depth b3 of the blasting rear end face cut is the same as the horizontal distance b4 from the short side of the second cutting area to the blasting cut boundary line of the rear end face of the blasting cut in the collapse direction; the width b6 of the second hole distribution area is the same as the wall thickness of the blasting front end face cut.

4. The method for local demolition of unqualified bridge piers according to claim 2, characterized in that: The height h3 of the short side of the second cutting area on both sides of the blasting gap in the collapse direction is 1.8-2.2 times the vertical distance h2 from the rear end face cut to the bottom edge of the second cutting area.

5. The method for local demolition of unqualified bridge piers by blasting according to claim 2, characterized in that: The width b2 of the first hole distribution area is the same as the wall thickness on both sides in the blasting direction.

6. The method for local demolition of unqualified bridge piers by blasting according to claim 1, characterized in that: The arrangement of the blasting holes in the first hole arrangement area and the second hole arrangement area is that the holes in adjacent vertical directions are staggered, and the holes in the same vertical direction are distributed at equal intervals.

7. The method for local demolition of unqualified bridge piers by blasting according to claim 6, characterized in that: The calculation method of the blasthole spacing h4 in the same vertical direction is: h4=(1.1~1.2)W The horizontal distance b7 between the center axes of adjacent vertical blastholes is calculated as follows: b7=(0.5~0.8)h4 The charge Q of each blasthole is calculated as: Q=q×v Where: W is the resistance line, with a value range of 0.3-0.5m; q is the comprehensive explosive consumption; v is the burden area of ​​a single blasting hole.

Images