A method for extrusion pre-splitting blasting in extremely hard rock in urban complex environment

Abstract

The application discloses a kind of extrusion presplitting blasting methods in extremely hard rock in complex urban environment, and blasting area is located underwater and blasting area is adjacent to the foundation of protection, comprising the following steps: S1, first, according to the position of hard rock drilling lofting, while the surrounding pipeline is explored and protected, then high-power drilling machine is used to blast drilling, and hole position is completed to carry out blast hole inspection;S2, site is according to the parameters of blasting design to carry out segmented blasting, after blasting, drilling core is taken to verify whether hard rock block size meets not more than 30cm, after determining the blasting parameters, subsequent presplitting blasting can be implemented according to the scheme;Blasting uses digital electronic detonator combined with emulsion explosive blasting, and micro-delay is set between holes and holes;S3, sleeve valve pipe grouting is carried out in the stratum of presplitting range after blasting, and after grouting is completed, formation coring detection is carried out, particle size and compaction grouting are detected, and after passing the test, shield tunneling is carried out.The application enables shield tunneling machine to normally tunnel when it tunnels to hard rock part.

Description

Technical Field

[0001] This invention relates to the field of blasting technology. More specifically, this invention relates to a method for compression pre-splitting blasting in extremely hard rock under complex urban conditions. Background Technology

[0002] For underwater hard rock tunnels, the tunnel boring machine cannot advance normally and blasting is required. In this blasting environment, the basic charge is twice that of a typical land-based stepped blast. Without vibration reduction measures, the maximum allowable charge per explosion under the blasting vibration control standard is very small. For large-scale hard rock blasting, it is not only very difficult to operate, but also almost impossible, and it is difficult to achieve the expected blasting block size effect. Summary of the Invention

[0003] The purpose of this invention is to provide a method for compression pre-splitting blasting in extremely hard rock under complex urban conditions, enabling tunnel boring machines to excavate normally when they reach the hard rock section.

[0004] The technical solution adopted by this invention to solve this technical problem is: a method for compression pre-splitting blasting in extremely hard rock under complex urban conditions, wherein the blasting area is located underwater and adjacent to the foundation of a protective structure, comprising the following steps:

[0005] S1. First, the hard rock borehole is laid out according to the design location, and the surrounding pipelines are explored and protected. Then, a high-power drilling rig is used to blast the borehole. After the borehole is completed, the blasting inspection is carried out.

[0006] S2. On-site blasting is carried out in stages according to the blasting design parameters. After blasting, core drilling is performed to verify whether the particle size of the hard rock blocks meets the requirement of not exceeding 30cm. After determining the blasting parameters, subsequent pre-splitting blasting can be carried out according to the plan. The blasting adopts digital electronic detonators combined with emulsion explosives, and micro-delay is set between holes.

[0007] S3. After blasting, the strata within the pre-splitting area are reinforced by sleeve valve grouting. After grouting is completed, core sampling is performed on the strata to test the particle size and compaction of the grout. Only after the test is passed can the tunnel boring machine proceed.

[0008] Preferably, step S1 specifically includes:

[0009] Before drilling, the steel casing is pressed into the lake bottom until it reaches the silty clay layer, with the pipe opening 30cm above the water surface. Then, vertical drilling is used to drill the hole. After the hole is formed, a rigid PVC casing is immediately inserted to prevent the hole from collapsing. The PVC casing is 5-10cm higher than the steel casing and is fixed in place. A plug is installed at the bottom of the PVC casing to temporarily block the hole. A method of drilling multiple holes and loading a small amount of explosive is used. The explosive cartridges are processed on the ground through PVC explosive tubes and then lowered into the rigid PVC casing in the hole to form a blasting hole.

[0010] Preferably, the PVC explosive tube loading includes: continuously or intermittently loading strip-shaped emulsion explosives into the PVC explosive tube, with two digital detonators for each loading section, and filling the borehole with coarse sand up to the ground surface as counterweight. When loading intermittently, the distance between the two explosive sections is ≥50cm. The lower end of the PVC explosive tube is sealed with a plug, and two holes are drilled symmetrically at the upper end of the tube wall to insert hemp rope or nylon rope for suspending the PVC tube and slowly lowering it.

[0011] Preferably, in step S2, during the segmented blasting, the blasting proceeds from the low rock surface to the high rock surface, first blasting the front row of low rock surface blast holes, and then blasting the rear row of high rock surface blast holes one hole at a time, row by row.

[0012] The blasting area is divided into 7 blasts, each with 3 rows of holes, breaking the intact bedrock into rock blocks no larger than 30cm, so that when the tunnel boring machine excavates to the hard rock section, it becomes a vertical and uniform rock surface.

[0013] Preferably, in step S1, a fracture surface is created 500mm outside the blasting range, and the depth of the fracture surface exceeds 1 meter beyond the blasting hole.

[0014] Preferably, the method for constructing the fracture surface within the blasting range of the foundation area of ​​the protected structure includes:

[0015] If the foundation of the protected object is located on one side of the blasting range, fracture surface construction shall be carried out on the side of the blasting range opposite to the protected foundation and on the adjacent two sides.

[0016] If the foundation of the protective structure is located at a corner opposite to the blasting area, fracture surface construction shall be carried out on both sides corresponding to the corner opposite to the protective foundation in the blasting area;

[0017] The construction of the fracture surface specifically includes: creating a fracture surface 500mm outside the blasting range, the fracture surface being more than 1 meter deeper than the blasting hole; placing energy dissipation components at certain intervals on the fracture surface; the energy dissipation components including: a first steel plate and a second steel plate; several springs welded between the first and second steel plates; when there is no external force, the distance between the outer wall surfaces of the first and second steel plates is less than the width of the fracture surface; the bottom surfaces of the first and second steel plates each have cutting edges, which are inserted into the bottom of the fracture surface to fix the energy dissipation components; the energy dissipation components are fixed against the outer wall surface of the fracture surface; the width of the first and second steel plates is the same, 0.3-0.8 meters.

[0018] This invention offers at least the following advantages: While the design incorporates a smaller borehole spacing, smaller diameter explosive cartridges, and a smaller single-shot charge, the maximum single-shot charge still exceeds the calculated allowable value, potentially causing vibration speeds to exceed safety limits. Therefore, technical improvements were made during fracture surface construction, effectively protecting key underwater structures. Blasting proceeds from the lower rock face to the higher rock face, utilizing the blasting of the front row of boreholes to compress the surrounding soil and create a free surface, followed by sequential detonation of the rear rows of boreholes. Pre-splitting and compressive blasting is applied to the rock sections within the tunnel section, breaking the intact bedrock into rock blocks no larger than 30cm, ensuring a vertically uniform rock surface when the tunnel boring machine reaches the hard rock section.

[0019] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the blast hole formation of the present invention;

[0021] Figure 2 This is a schematic diagram of the PVC medicine tube for adding medicine according to the present invention;

[0022] Figure 3 This is a schematic diagram of the detonation range and detonation sequence of the present invention;

[0023] Figure 4 This is a top view of the fracture surface construction of the present invention.

[0024] 1- Rigid PVC sleeve, 2- Steel sleeve, 3- Counterweight, 4- Digital detonator, 5- Strip emulsion explosive, 6- Blocking material, 7- PVC explosive tube, 8- Bridge abutment, 9- Blasting range, 10- Fracture surface, 11- First steel plate, 12- Second steel plate, 13- Spring. Detailed Implementation

[0025] The present invention will now be described in detail and completely with reference to the accompanying drawings. Those skilled in the art will be able to implement the present invention based on these descriptions. Before describing the present invention with reference to the accompanying drawings, it should be particularly noted that the technical solutions and features provided in various parts of the present invention, including the following description, can be combined with each other without conflict.

[0026] Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The specific implementation process is as follows:

[0028] The environment in which this embodiment is applied: The terrain of the section where the tunnel passes through the lake is undulating. The tunnel passes through a moderately weathered quartz sandstone structure with a quartz content of about 80%, a core sampling rate of about 75%-95%, an RDQ of 50%-75%, a standard value of saturated uniaxial compressive strength of 128-251 MPa, an average saturated compressive strength of 164.4 MPa, and a standard value of 144.4 MPa. It is a hard rock, and the hard rock part is located at the bottom of the lake. The blasting area is adjacent to the enlarged foundation of the bridge abutment.

[0029] This invention provides a method for compression pre-splitting blasting in extremely hard rock under complex urban conditions, wherein the blasting area is located underwater and adjacent to the foundation of a protective structure (e.g., a bridge abutment 8), and includes the following steps:

[0030] S1. Underwater construction will be carried out using steel pontoons as working platforms. First, the hard rock boreholes will be laid out according to the design location. At the same time, the surrounding pipelines will be explored and protected. Then, high-power drilling rigs will be used for blasting drilling. After the boreholes are completed, blasting inspection will be carried out. The spacing between boreholes is 0.5m×0.5m. The borehole depth exceeds the bottom elevation of the tunnel by 1m. The blasting range 9 exceeds the width of the hard rock by 0.5m on each side.

[0031] S2. On-site blasting is carried out in stages according to the blasting design parameters. After blasting, core drilling is performed to verify whether the particle size of the hard rock blocks meets the requirement of not exceeding 30cm. After determining the blasting parameters, subsequent pre-splitting blasting can be carried out according to the plan. The blasting adopts digital electronic detonators combined with emulsion explosives. Micro-delay is set between holes to reduce the blasting vibration effect.

[0032] S3. After blasting, the pre-splitting area of ​​the strata is reinforced by sleeve valve grouting. The grouting hole spacing is 1.2m*1.5m, and 1:1 cement grout is used. The grouting pressure is 1.0~1.5MPa. After grouting, core sampling of the strata is carried out to test the particle size and compaction reinforcement grouting. Only after the test is qualified can the shield tunneling proceed. If abnormal parameters such as no penetration, increased thrust or torque, or increased slag temperature occur during shield tunneling in hard rock sections, the machine is immediately stopped and the tunnel chamber is opened to check the stability of the working face and the wear of the cutters. If the wear exceeds the limit or the cutters break, the cutters are replaced in time. After replacement, the tunnel chamber is closed and the advance is resumed.

[0033] In the aforementioned technical solution, the tunnel top is buried at a depth of approximately 12 meters, and the thickest layer to be blasted is 8.2 meters, making blasting and fracturing quite difficult. To facilitate construction and ensure the blasting and fracturing effect, the first row of holes is blasted. Then, the blasting of the first row of holes is used to compress the surrounding soil to create a free surface, and the subsequent rows of holes are blasted sequentially. Due to the complex environment of surrounding buildings, structures, and pipelines, an interval charging structure must be adopted to control the maximum single-explosive charge and reduce blasting vibration.

[0034] In this embodiment, the borehole diameter in S1 is 100mm, the diameter of the PVC sleeve for loading the drug is 63mm (finished product, no customization required), and the diameter of the drug roll is 32mm and 50mm.

[0035] Step S1 specifically includes:

[0036] like Figure 1 As shown, before drilling, a 125mm diameter steel casing 2 is pressed into the lake bottom until it reaches the silty clay layer, with the casing opening 30cm above the water surface to prevent the silt from clogging the blast hole. The diameter of the steel casing 2 is larger than the diameter of the borehole. Then, drilling is carried out using a vertical drilling method. After the hole is formed, a 75mm diameter rigid PVC casing 1 is immediately inserted to prevent the hole from collapsing. The rigid PVC casing is 25-10cm higher than the steel casing and is fixed. The bottom of the rigid PVC casing is fitted with a plug, and the hole opening is covered or temporarily blocked with a snakeskin bag to prevent foreign objects from falling into and clogging the blast hole. A method of drilling multiple holes and loading a small amount of explosive is adopted. The explosive diameter is Φ32mm and / or Φ50mm. After the explosive cartridge is processed on the ground through a 63mm diameter PVC explosive tube 7, it is lowered into the 75mm rigid PVC casing 1 in one go to form a blasting hole.

[0037] This technical solution may also include the following technical details to better achieve the technical effect: such as Figure 2 As shown, the charging of the PVC explosive tube 7 includes: continuously or intermittently charging the PVC explosive tube 7 with strip-shaped emulsion explosive 5 in the shape of Φ32mm (or in combination with Φ50mm), with two digital detonators 4 for each charging section, and filling the borehole with coarse sand to the ground surface as a counterweight 3. When charging intermittently, the distance between the two explosive sections is ≥50cm, and they are separated by a plug 6, which is coarse sand. The lower end of the PVC explosive tube 7 is sealed with a plug, and two holes are drilled symmetrically at the upper end of the tube wall to insert hemp rope or nylon rope to suspend the PVC tube and lower it slowly.

[0038] The total length of the PVC explosive tube 7 and the rope should be greater than the hole depth by 2m. Based on the borehole inspection, determine the total drilling depth L1. Then, accurately measure the sum of the lengths of the PVC explosive tube and the rope, L2, so that L1 + 2 = L2. Mark the rope with a small red ribbon or other easily visible marker. The distance from this marker to the bottom of the PVC explosive tube is equal to the total borehole depth (overburden thickness + rock borehole depth). After the PVC explosive tube 7 is in place, fix the rope to the casing wall to prevent it from moving.

[0039] This technical solution may also include the following technical details to better achieve the technical effect: In step S2, when blasting in stages, blasting is carried out from the low rock surface to the high rock surface. First, the blast holes of the front row of low rock surfaces are blasted, and the blasting of the front row of holes is used to squeeze the surrounding soil layer to create a free surface. Then, the holes of the rear row of high rock surfaces are blasted one by one, row by row.

[0040] like Figure 3 As shown, a test blasting zone consisting of 10 holes was selected before the first formal blast. The test blasting zone was divided into sections with varying initiation ranges and timings. The zone was divided into 7 blasts, each with 3 rows of holes, breaking the intact bedrock into rock fragments no larger than 30cm, ensuring a vertical and uniform rock surface when the tunnel boring machine reaches the hard rock section. The advantages of this method are: 1) Smaller explosive charge per section, controlling blasting vibration; 2) Creating a free surface for subsequent blasts by detonating the first hole; 3) Explosive stress waves are fully reflected by the free surface, enhancing rock fragmentation, and the collision and compression between adjacent blast holes further strengthens secondary rock fragmentation; 4) The use of digital detonators (4-stage detonation) provides high blasting delay accuracy, which helps control blasting vibration and simplifies the connection and detection of the detonation network.

[0041] This technical solution may also include the following technical details to better achieve the technical effect: In step S1, a fracture surface 10 is created 500mm away from the blasting range 9, and the depth of the fracture surface 10 exceeds 1 meter of the blasting hole. The fracture surface 10 can avoid the blasting from squeezing the underground rock, causing bottom heave, lateral displacement, and lateral squeezing of the foundation of the protected object. Pre-splitting blasting can reduce the peak vibration acceleration by 30%-60% compared to traditional blasting. However, during construction, it was found that near the abutment 8, even though traditional pre-splitting construction can reduce the peak vibration acceleration by 60% compared to traditional blasting, and combined with multiple drillings and less explosive charge, with the maximum explosive charge, the particle size of the hard rock blocks after blasting is greater than 30cm.

[0042] This technical solution may also include the following technical details to better achieve the technical effect: In order to solve the above problems, the construction of the fracture surface 10 has been improved, so that the pre-splitting blasting can reduce the peak vibration acceleration by 75% compared with the traditional blasting. The construction method of the fracture surface 10 in the blasting range 9 of the protective foundation area includes:

[0043] If the foundation of the protective structure is located on one side of the blasting range 9, the fracture surface 10 shall be constructed on the side of the blasting range 9 opposite to the protective foundation and on the adjacent sides.

[0044] like Figure 4 As shown, if the foundation abutment 8 of the protected structure is located at a corner opposite to the blasting range 9, the fracture surface 10 is constructed on both sides corresponding to the corner opposite to the protected foundation of the blasting range 9.

[0045] The construction of fracture surface 10 specifically includes: creating fracture surface 10 500mm away from the blasting range 9, the depth of fracture surface 10 exceeding the blasting hole by 1 meter, the width of fracture surface 10 being 1 meter, and placing energy dissipation components at certain intervals on fracture surface 10, the interval of which is set according to the actual construction situation. The energy dissipation components include: a first steel plate 11 and a second steel plate 12, with several springs 13 welded between the first steel plate 11 and the second steel plate 12. When there is no external force, the distance between the outer wall surface of the first steel plate 11 and the outer wall surface of the second steel plate 12 is less than the width of fracture surface 10. The bottom surfaces of the first steel plate 11 and the second steel plate 12 are both equipped with cutting edges, which are inserted into the bottom of fracture surface 10 to fix the energy dissipation components. The energy dissipation components are fixed against the outer wall surface of fracture surface 10. The width of the first steel plate 11 and the second steel plate 12 is the same, ranging from 0.3 to 0.8 meters. By improving the construction of the fracture surface 10, blasting vibration can be significantly reduced and the amount of blasting explosives can be increased, so that the particle size of the hard rock blocks after blasting is less than 30cm, ensuring the smooth excavation of the tunnel boring machine.

[0046] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A method for pre-splitting blasting in extremely hard rock under complex urban conditions, wherein the blasting area is located underwater and adjacent to the foundation of a protective structure, characterized in that... Includes the following steps: S1. First, lay out the hard rock borehole according to the design location, and at the same time explore and protect the surrounding pipelines. Then, use a high-power drilling machine to blast the borehole. After the borehole is completed, blast the borehole for inspection. Create a fracture surface 500mm away from the blasting range. The depth of the fracture surface exceeds the blasting hole by 1 meter. Place energy dissipation components in the fracture surface. The energy dissipation component includes: a first steel plate and a second steel plate, with several springs welded between the first steel plate and the second steel plate. When there is no external force, the distance between the outer wall surface of the first steel plate and the outer wall surface of the second steel plate is less than the width of the fracture surface. The bottom surfaces of the first steel plate and the second steel plate are both equipped with cutting edges, which are inserted into the bottom of the fracture surface to fix the energy dissipation component. The energy dissipation component is fixed in contact with the outer wall surface of the fracture surface. S2. On-site blasting is carried out in stages according to the blasting design parameters. After blasting, core drilling is performed to verify whether the particle size of the hard rock blocks meets the requirement of not exceeding 30cm. After determining the blasting parameters, subsequent pre-splitting blasting can be carried out according to the plan. The blasting adopts digital electronic detonators combined with emulsion explosives, and micro-delay is set between holes. S3. After blasting, the strata within the pre-splitting area are reinforced by sleeve valve grouting. After the grouting is completed, core sampling is performed on the strata to test the particle size and compaction of the grout. Only after the test is qualified can the tunnel boring machine proceed.

2. The method for compression pre-splitting blasting in extremely hard rock under complex urban environments as described in claim 1, characterized in that, Step S1 specifically includes: Before drilling, the steel casing is pressed into the lake bottom until it reaches the silty clay layer, with the casing opening 30cm above the water surface. Then, vertical drilling is carried out. After the hole is formed, a rigid PVC casing is immediately inserted to prevent the hole from collapsing. The rigid PVC casing is 5-10cm higher than the steel casing and is fixed in place. A plug is installed at the bottom of the rigid PVC casing to temporarily block the hole. A method of drilling multiple holes and loading a small amount of explosive is adopted. The explosive cartridges are processed on the ground through PVC explosive tubes and then lowered into the rigid PVC casing in the hole to form a blasting hole.

3. The method for compression pre-splitting blasting in extremely hard rock under complex urban environments as described in claim 2, characterized in that, The PVC explosive tube loading process includes: continuously or intermittently loading strip-shaped emulsion explosives into the PVC explosive tube, with two digital detonators used for each loading section, and the boreholes filled with coarse sand up to the ground surface as counterweight. When loading explosives intermittently, the distance between the two explosive sections should be ≥50cm. The lower end of the PVC explosive tube is sealed with a plug, and two holes are drilled symmetrically at the upper end of the tube wall to insert hemp rope or nylon rope, which is used to suspend the PVC tube and lower it slowly.

4. The method for compression pre-splitting blasting in extremely hard rock under complex urban environments as described in claim 1, characterized in that, In step S2, during the segmented blasting, blasting is carried out from the low rock surface to the high rock surface. First, the blast holes of the low rock surface in the front row are blasted, and then the blast holes of the high rock surface in the back row are blasted one hole at a time. The blasting area is divided into 7 blasts, each with 3 rows of holes, breaking the intact bedrock into rock blocks no larger than 30cm, so that when the tunnel boring machine excavates to the hard rock section, it becomes a vertical and uniform rock surface.

5. The method for compression pre-splitting blasting in extremely hard rock under complex urban environments as described in claim 1, characterized in that, The methods for constructing the fracture surface within the blasting range of the foundation area of ​​the protected structure include: If the foundation of the protective structure is located on one side of the blasting area, fracture surface construction shall be carried out on the side of the blasting area opposite to the protective foundation and on the adjacent two sides. If the foundation of the protective structure is located at a corner opposite to the blasting area, fracture surface construction shall be carried out on both sides corresponding to the corner opposite to the protective foundation in the blasting area; The width of the first steel plate and the second steel plate is the same, ranging from 0.3 to 0.8 meters.

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