Tunnel construction method for transition section of integral presplitting blasting and short footage tunneling blasting

Abstract

The invention provides a transition section tunnel construction method of integral presplitting blasting and short footage tunneling blasting, and relates to the technical field of tunnel blasting excavation. The method comprises the steps that S1, a tunnel transition section CAD three-dimensional model is established, pre-splitting blasting parameters are designed, and the blasting parameters comprise the blast hole distance, the blast hole length, the single-hole explosive loading amount, the explosive loading structure and the detonation mode; s2, pre-splitting blasting is constructed, and one-time overall pre-splitting blasting is conducted on the transition section tunnel; and S3, one-truss-one-blasting short-footage tunneling blasting is carried out on the rock mass in the pre-crack, and supporting is carried out according to the tunneling footage. Wherein after the plane coordinate position of the blast hole opening on the end face of the transition section is determined, the azimuth angle, the elevation angle and the blast hole length of the hole bottom center of the blast hole in a spherical coordinate are calculated through coordinate transformation. By means of the construction method, accurate control blasting of the transition section roadway can be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel blasting excavation, and in particular provides a method for constructing a gradual section tunnel by integral pre-splitting blasting and short-footage excavation blasting. Background Art

[0002] During the construction of long-span tunnels in transitional sections, ramp steps are typically used as pilot tunnels. After the pilot tunnel is completed, the tunnel is then expanded horizontally to the designed cross-section. Existing methods for subway tunnel construction involve excavating the transition section from a small cross-section into a large one. This involves excavating the auxiliary structures from the edge of the tunnel opening outwards. Blastholes are then drilled at angles corresponding to the desired widening height, and the tunnel is then excavated using blasting.

[0003] Currently, the excavation method for transition tunnels is typically to first dig an intermediate pilot tunnel, then expand the tunnel horizontally to the designed cross-section. Full-section blasting is often used, often increasing the tunnel excavation dimensions to ensure steel frame installation, and then increasing the thickness of the shotcrete to meet the tunnel's designed cross-section requirements. Currently, there is no specific excavation method specifically designed for controlling the contour of transition tunnels, and further improvements to existing methods are needed. Summary of the Invention

[0004] In order to achieve precise controlled blasting of the gradient section tunnel, the present invention provides a gradient section tunnel construction method using integral pre-splitting blasting and short-feed excavation blasting. The specific technical solution is as follows.

[0005] A method for constructing a gradual section tunnel using integral pre-splitting blasting and short-footage excavation blasting, characterized in that the method comprises:

[0006] S1. Establish a CAD three-dimensional model of the tunnel gradient section and design pre-splitting blasting parameters, including the blasting parameters such as hole spacing, hole length, single-hole charge, charge structure, and detonation method;

[0007] S2. Pre-splitting blasting: Conduct a pre-splitting blast on the transition section of the tunnel.

[0008] S3. Carry out short-length excavation blasting of the rock mass inside the pre-cracks, one blast at a time, and provide support according to the excavation advance.

[0009] Preferably, after the plane coordinate position of the blasthole orifice on the end face of the gradient section is determined, the azimuth angle φ of the center of the blasthole bottom in the spherical coordinates is calculated by coordinate transformation:

[0010]

[0011] Among them, △x is the coordinate difference in the x-axis direction, and △y is the coordinate difference in the y-axis direction.

[0012] Preferably, after the plane coordinate position of the blasthole orifice on the end face of the gradient section is determined, the elevation angle θ of the center of the blasthole bottom in the spherical coordinates is calculated by coordinate conversion:

[0013]

[0014] Among them, △z is the coordinate difference in the z-axis direction, and r is the length of the blasthole.

[0015] Preferably, after the plane coordinate position of the blasthole opening on the end face of the gradient section is determined, the azimuth angle φ, φ, and φ of the blasthole bottom center in the spherical coordinates are calculated by coordinate conversion.

[0016] The blasthole length r is specifically:

[0017]

[0018] Among them, △x is the coordinate difference in the x-axis direction, △y is the coordinate difference in the y-axis direction, and △z is the coordinate difference in the z-axis direction.

[0019] Preferably, the two cross-sectional dimensions at both ends of the tunnel transition section are different, and the spacing between the blastholes on the two cross-sectional dimensions is different, so that the maximum hole spacing between two adjacent blastholes meets the pre-splitting blasting conditions, and the hole bottom spacing and the number of blastholes are determined according to the contour line length of the larger cross-sectional dimension; after the number of blastholes is determined, the hole mouth positions are determined on the smaller cross-sectional dimension according to the principle of uniform arrangement.

[0020] Preferably, after the blasthole spacing and blasthole length are determined, the single-hole charge amount, charge structure, and detonation method are determined according to pre-splitting blasting.

[0021] Preferably, after the pre-splitting blasting is completed, the blasthole depth is designed according to the spacing between the steel frames on both sides of the tunnel to achieve one blast per advance.

[0022] Preferably, the tunnel transition section includes two tunnels with transitional connection portions having different cross-sectional shapes or areas.

[0023] Preferably, the tunnel support steel frame matches the cross section of the tunnel being excavated.

[0024] The beneficial effects of the gradient section tunnel construction method provided by the present invention, which combines overall pre-splitting blasting and short-footage excavation blasting, are as follows: the construction method is used for the mining method construction of the gradient section of the tunnel, and proposes a construction method that combines spatial overall pre-splitting blasting with short-footage excavation blasting, which can achieve precise control blasting of the gradient section tunnel; in addition, after the excavation blasting is completed by this method, it is more convenient to erect the support steel frame, thereby speeding up the construction progress, and the method will not excessively damage the original rock environment and can ensure the stability of the overall tunnel structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1It is a top view of the transition section tunnel and a schematic diagram of the steel frame layout;

[0026] Figure 2 This is a schematic diagram of the arrangement of pre-splitting blastholes;

[0027] In the figure: 1- civil air defense section, 2- gradient section, 3- pipe shed section DETAILED DESCRIPTION

[0028] Combine Figure 1 and Figure 2 As shown, a specific implementation method of a gradual section tunnel construction method of integral pre-splitting blasting and short-footage excavation blasting provided by the present invention is described.

[0029] A method for constructing a gradual section tunnel using integral pre-splitting blasting and short-footage excavation blasting, the method comprising:

[0030] S1. Build a 3D CAD model of the tunnel transition section and design pre-splitting blasting parameters, including blasthole spacing, blasthole length, single-hole charge, charge structure, and initiation method.

[0031] When the plane coordinate position of the blasthole mouth on the end face of the gradient section is determined, the azimuth angle φ of the blasthole bottom center in the spherical coordinates is calculated by coordinate transformation:

[0032]

[0033] Among them, π is the pi, △x is the coordinate difference in the x-axis direction, and △y is the coordinate difference in the y-axis direction.

[0034] When the plane coordinate position of the blasthole mouth on the end face of the gradient section is determined, the elevation angle θ of the blasthole bottom center in the spherical coordinates is calculated by coordinate transformation:

[0035]

[0036] Among them, π is the pi, △z is the coordinate difference in the z-axis direction, and r is the length of the blasthole.

[0037] When the plane coordinate position of the blasthole mouth at the end face of the gradient section is determined, the azimuth angle φ of the blasthole bottom center in the spherical coordinates is calculated by coordinate transformation.

[0038] The blasthole length r is specifically:

[0039]

[0040] Among them, △x is the coordinate difference in the x-axis direction, △y is the coordinate difference in the y-axis direction, and △z is the coordinate difference in the z-axis direction.

[0041] The two sections at both ends of the tunnel transition section have different sizes, and the spacing between the blast holes on the two sections is different. The maximum hole spacing between two adjacent blast holes meets the pre-splitting blasting conditions, and the bottom spacing and number of blast holes are determined according to the contour line length of the larger section; after the number of blast holes is determined, the hole mouth position is determined on the smaller section according to the principle of uniform arrangement.

[0042] S2. Pre-splitting blasting: Conduct a pre-splitting blast on the transition section of the tunnel.

[0043] After the blasthole spacing and blasthole length are determined, the single-hole charge, charge structure, and detonation method are determined according to pre-splitting blasting.

[0044] S3. Carry out short-length excavation blasting of the rock mass inside the pre-cracks, one blast at a time, and provide support according to the excavation advance.

[0045] After the pre-splitting blasting is completed, the blasthole depth is designed according to the spacing between the steel frames on both sides of the tunnel to achieve one blast per unit of excavation progress.

[0046] The tunnel transition section includes two tunnels with transition connection parts of different cross-sectional shapes or areas, and the tunnel support steel frame is coordinated with the tunnel section.

[0047] The construction method of the present invention is further explained in conjunction with a specific construction case. First, overall pre-splitting blasting is carried out on the gradual transition section of the tunnel, and the excavation range is controlled by using the pre-cracks. Then, blast holes are arranged according to the extension direction of the pre-cracks, and short-feed multi-cycle blasting excavation is carried out on the rock mass in the tunnel section.

[0048] The cross-sectional dimensions of the tunnels at both ends of the transition section are different, and the spacing between the blastholes on the two sections is different. In order to ensure that the maximum spacing between two adjacent holes meets the pre-splitting blasting requirements, the spacing between the bottom of the blastholes and the number of blastholes are determined according to the length of the contour line of the large section (CC' section). After the number of blastholes is determined, the position of the orifices is determined on the small section (BB' section) of the transition section according to the principle of uniform arrangement. When the plane coordinate position of the blasthole orifice on the end face of the transition section (BB' section) is determined, the azimuth of the center of the bottom of the blasthole in the spherical coordinates is calculated by coordinate conversion. Elevation angle θ and blasthole length r. Pre-splitting holes are drilled based on the azimuth, elevation, and blasthole length of the blasthole bottom center in spherical coordinates. A single pre-splitting blast is then carried out throughout the transition section of the tunnel according to the blasting design. Following the pre-splitting blast, short-length excavation blasting, one blast per frame, is carried out within the pre-splitting cracks. Due to the different spacing between the steel frames on the left and right sides of the tunnel, the blasthole depth is designed from left to right according to the actual steel frame positions to ensure that the excavation progress is consistent with the "one blast per frame" approach.

[0049] Table 1 shows the position parameters of the corresponding pre-splitting holes in spatial coordinates and spherical coordinates. Figure 2A blasthole layout designed according to this patented method for the transition section of a subway station entrance and exit. The design shows 31 pre-splitting holes, with a hole-to-hole spacing of 466mm, a hole-to-hole spacing of 540mm, and an average hole spacing of 503mm. The shallowest pre-splitting hole depth is 2290mm, and the deepest is 4921mm.

[0050] Table 1 Blast hole position parameters

[0051]

[0052] This construction method is used for mining-based construction of the transition section of a tunnel. It proposes a construction method that combines spatial integral pre-splitting blasting with short-feed excavation blasting, which can achieve precise controlled blasting of the transition section tunnel. In addition, after the excavation blasting is completed by this method, it is more convenient to erect the support steel frame, thereby speeding up the construction progress. Moreover, this method will not excessively damage the original rock environment and can ensure the stability of the overall tunnel structure.

[0053] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the scope of protection of the present invention.

Claims

1. A method for constructing a gradual section tunnel using integral pre-splitting blasting and short-footage excavation blasting, characterized in that: The construction method includes: S1. Establish a CAD three-dimensional model of the tunnel gradient section and design pre-splitting blasting parameters, including the blasting parameters such as hole spacing, hole length, single-hole charge, charge structure, and detonation method; S2. Pre-splitting blasting: Conduct a pre-splitting blast on the transition section of the tunnel. S3. Carry out short-length excavation blasting of the rock mass inside the pre-cracks, one blast at a time, and provide support according to the excavation advance.

2. The method for constructing a gradual section tunnel using integral pre-splitting blasting and short-footage excavation blasting according to claim 1 is characterized in that: When the plane coordinate position of the blasthole mouth on the end face of the gradient section is determined, the azimuth angle φ of the blasthole bottom center in the spherical coordinates is calculated by coordinate transformation: Among them, △x is the coordinate difference in the x-axis direction, and △y is the coordinate difference in the y-axis direction.

3. The method for constructing a gradual section tunnel using integral pre-splitting blasting and short-footage excavation blasting according to claim 1 is characterized in that: When the plane coordinate position of the blasthole mouth on the end face of the gradient section is determined, the elevation angle θ of the blasthole bottom center in the spherical coordinates is calculated by coordinate transformation: Among them, △z is the coordinate difference in the z-axis direction, and r is the length of the blasthole.

4. The method for constructing a gradual section tunnel using integral pre-splitting blasting and short-footage excavation blasting according to claim 1 is characterized in that: When the plane coordinate position of the blasthole mouth at the end face of the gradient section is determined, the azimuth angle φ of the blasthole bottom center in the spherical coordinates is calculated by coordinate transformation. The blasthole length r is specifically: Among them, △x is the coordinate difference in the x-axis direction, △y is the coordinate difference in the y-axis direction, and △z is the coordinate difference in the z-axis direction.

5. The method for constructing a gradual section tunnel using integral pre-splitting blasting and short-footage excavation blasting according to claim 1 is characterized in that: The two sections at both ends of the tunnel transition section have different sizes, and the spacing between the blast holes on the two sections is different, so that the maximum hole spacing between two adjacent blast holes meets the pre-splitting blasting conditions, and the bottom spacing of the blast holes and the number of blast holes are determined according to the contour line length of the larger section; after the number of blast holes is determined, the hole mouth position is determined on the smaller section according to the principle of uniform arrangement.

6. The method for constructing a gradual section tunnel using integral pre-splitting blasting and short-footage excavation blasting according to claim 1 is characterized in that: After the blasthole spacing and blasthole length are determined, the single-hole charge amount, charge structure, and detonation method are determined according to pre-splitting blasting.

7. The method for constructing a gradual section tunnel using integral pre-splitting blasting and short-footage excavation blasting according to claim 1 is characterized in that: After the pre-splitting blasting is completed, the blasthole depth is designed according to the spacing between the steel frames on both sides of the tunnel, so that one blast is performed for each advance.

8. The method for constructing a gradual section tunnel using integral pre-splitting blasting and short-footage excavation blasting according to claim 1 is characterized in that: The tunnel transition section includes two tunnels with transitional connection parts having different cross-sectional shapes or areas.

9. The method for constructing a gradual section tunnel using integral pre-splitting blasting and short-footage excavation blasting according to claim 1, characterized in that: The tunnel support steel frame is matched with the tunnel section.

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