Micro-blasting grouting anchor and anchoring method suitable for tunnels with extrusive surrounding rocks

Abstract

The present invention belongs to the field of tunnel engineering technology, and particularly relates to a micro-blasting grouting anchor suitable for tunnels with extrusive surrounding rock and an anchoring method. The anchor comprises an anchor body and a fastener. The anchor body is a double-layer jacketed structure formed by a hollow inner sleeve and an outer sleeve. The anchor body comprises an inner anchor head section, a middle section, and an outer anchor head section, which are arranged in sequence. The inner anchor head section of the anchor body is flared, and the middle section outer sleeve is provided with a plum blossom hole. A baffle is radially provided between the outer end of the outer sleeve and the inner sleeve, and grouting holes are provided on the baffle. The fastener is arranged on the outer side of the outer anchor head section. The present invention can effectively improve the bonding strength between the anchor and the surrounding rock mass in the anchoring area, increase the ultimate pullout force of the anchor, and control the range of the loose zone of the extrusive surrounding rock and the deformation of the support structure.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel engineering, and in particular relates to a micro-blasting grouting anchor rod suitable for a tunnel with extrusion surrounding rock and an anchoring method. Background Art

[0002] As an important structural unit of the "anchor shotcrete support" in the "New Austrian Tunneling Method", anchor rods play an important role in the stability of the surrounding rock and support structure. The main functions of anchor rods include: (1) Suspension function: the anchor rods pass through the weak, loose, and unstable rock and soil, and anchor on the deep and stable rock and soil, providing sufficient tension to overcome the self-weight and downward force of the sliding rock and soil, and prevent the tunnel wall from sliding and collapsing; (2) Extrusion reinforcement function: after the anchor rods are subjected to force, a compression zone is formed within a certain range around them. The anchor rods are arranged in an appropriate manner so that the compression zones formed by adjacent anchor rods overlap to form a compression belt. The loose strata in the compression belt are reinforced by the anchor rods, and the integrity is enhanced and the bearing capacity is improved. (3) Composite beam (arch) function: after the anchor rods are inserted into the stratum to a certain depth, the strata are squeezed against each other under the action of the anchoring force, the interlayer friction resistance increases, and the internal stress and deflection are greatly reduced, which is equivalent to turning a simple stack of several layers of beams (arches) into a composite beam (arch). The flexural rigidity and strength of the composite beam (arch) are greatly improved, thereby enhancing the bearing capacity of the stratum. The greater the anchoring force provided by the anchor rod, the more significant the effect. Anchor-shotcrete support effectively constrains the excavated cavern, allowing a certain amount of deformation in the surrounding rock. This improves the self-bearing capacity of the surrounding rock while limiting excessive and unfavorable deformation, thus playing a significant role in the stability of the surrounding rock and support.

[0003] In compressive surrounding rock (or soft rock with high in-situ stress), anchor bolts act as a bridge and medium between the loosened zone and the undisturbed rock mass, controlling the compressive deformation of the tunnel surrounding rock, reducing the deformation rate, and minimizing the ultimate deformation of the surrounding rock. Anchor bolts can prevent excessive loosening of the surrounding rock, thus avoiding adverse conditions such as cracking of shotcrete, twisting and deformation of steel frames, and deformation intrusion and instability of the support structure. The pullout force of an anchor bolt is generally provided primarily by the bond between the anchor bolt and mortar in the anchoring zone (stable or undisturbed strata), and the bond between the mortar and the borehole wall. However, in compressive surrounding rock formations, due to high or extremely high in-situ stresses, the interlayer joints and fissures in the anchoring zone are compacted or closed, resulting in poor anchor grouting effectiveness. Since the grouting fluid has difficulty propagating through these joints and fissures, it cannot effectively bond with the borehole wall. Consequently, the bond between the grouting fluid and the borehole wall is weak, making it difficult for the anchor bolt to effectively exert its ultimate pullout force. However, due to the special high-stress soft rock characteristics of squeezing rock tunnels, anchor rods are required to provide effective pulling force to control the deformation of the loosened rock mass. This puts higher demands on anchor rod anchoring technology. However, the existing anchor rods and anchoring technologies are difficult to meet the application requirements of squeezing rock tunnels. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology in the application of anchor rods in extrusive surrounding rocks, the present application provides a micro-blasting grouting anchor rod suitable for extrusive surrounding rock tunnels, which can effectively improve the bonding force between the anchor rod in the anchoring area and the rock mass around the hole, increase the ultimate pull-out force of the anchor rod, and control the range of the loosening zone of the extrusive surrounding rock and the deformation of the support structure.

[0005] At the same time, the present application also provides an anchoring method using the above-mentioned micro-blasting grouting anchor rod suitable for extrusion rock tunnels.

[0006] The technical solutions adopted by this application to achieve the above-mentioned objectives are:

[0007] A micro-blasting grouting anchor suitable for tunnels with extrusive surrounding rocks, comprising an anchor body and a fastener. The anchor body is a double-layer jacketed structure formed by a hollow inner sleeve and an outer sleeve. The anchor body comprises an inner anchor head section, a middle section and an outer anchor head section arranged in sequence. The inner anchor head section of the anchor body is trumpet-shaped, a plum blossom hole is provided on the outer sleeve of the middle section, a baffle is radially arranged between the outer end of the outer sleeve and the inner sleeve, and a grouting hole is provided on the baffle; the fastener is arranged on the outside of the outer anchor head section.

[0008] It is further defined that the inner anchor head section of the anchor rod body is filled with a blasting core, and the blasting lead of the blasting core is led out through the interlayer between the inner sleeve and the outer sleeve; the blasting core is blocked by a sound-absorbing cotton layer.

[0009] It is further defined that the ratio of the length of the inner anchor head section of the anchor rod body to the total length of the anchor rod is 0.1 to 0.33:1.

[0010] It is further defined that the ratio of the middle section length of the anchor rod body to the total length of the anchor rod is 0.58:1.

[0011] It is further defined that a protective frame is provided on the outside of the anchor rod body, and the protective frame is connected to the fastener; the fastener includes a pad and a nut, and the nut is matched with the pad and is sleeved on the outer sleeve and threadedly connected to the outer sleeve.

[0012] It is further defined that the cavity between the inner sleeve and the outer sleeve is poured with resin slurry; and the inner cavity of the inner sleeve is poured with cement mortar.

[0013] It is further defined that the cement mortar 7 has a ratio of cement:sand:water=1:(1-1.5):(0.45-0.5).

[0014] An anchoring method suitable for squeezing surrounding rock tunnels is implemented by the above-mentioned micro-blasting grouting anchor suitable for squeezing surrounding rock tunnels, and specifically comprises the following steps:

[0015] 1) Drilling and cleaning holes;

[0016] 2) Insert the anchor head section containing the blasting core in the anchor rod body into the hole in step 1), lead the blasting lead through the interlayer between the inner sleeve and the outer sleeve, install the anchor rod body, and fasten it with fasteners;

[0017] 3) Grouting is injected into the cavity between the inner sleeve and the outer sleeve through the grouting hole. The grouting liquid seeps out through the plum blossom holes of the outer sleeve, so that the anchor body is bonded to the hole wall;

[0018] 4) After the slurry in step 3) reaches the designed strength, ignite the blasting fuse and perform micro-blasting;

[0019] 5) After the micro-blasting is completed, the inner sleeve is connected to the grouting machine, and secondary grouting is carried out through the internal cavity of the inner sleeve. Grouting is stopped when the grouting pressure at the hole mouth reaches 0.5-1.0 MPa, completing the micro-blasting grouting of the extrusion rock tunnel.

[0020] Further defined, the step 2) is specifically as follows:

[0021] 2.1) Place a core consisting of No. 2 ammonium nitrate explosive and an electric detonator into the anchor head section of the anchor bolt body. Connect the electric detonator to a blasting fuse, which is led out through the interlayer between the inner and outer sleeves. Plugging the core with sound-absorbing cotton isolates it from the cavity in the middle section of the anchor bolt body.

[0022] 2.2) Insert the inner anchor head section containing the blasting core in the anchor rod body into the hole in step 1), install the anchor rod body, and tighten it with fasteners.

[0023] It is further defined that the step 3) specifically comprises: pouring resin into the cavity between the inner sleeve and the outer sleeve through the grouting hole, and the resin slurry seeps out through the plum blossom holes on the wall of the outer sleeve, so that the anchor body is bonded to the hole wall.

[0024] It is further defined that step 5) is specifically as follows: after the micro-blasting is completed, the inner sleeve is connected to the grouting machine, and secondary grouting is performed through the internal cavity of the inner sleeve. The slurry for the secondary grouting is a cement mortar with a ratio of cement: sand: water = 1: (1-1.5): (0.45-0.5) and a strength of not less than M10. The secondary grouting is completed before initial setting, and the grouting is stopped when the grouting pressure at the hole mouth reaches 0.5-1.0 MPa, thereby completing the micro-blasting grouting of the extrusive surrounding rock tunnel.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] 1) The outer sleeve and the inner sleeve of the present application are arranged to form a double-layer grouting anchor structure, and resin is poured into the interlayer between the outer sleeve and the inner sleeve. A plum blossom hole is opened on the outer sleeve in the middle section of the anchor body to allow the resin to seep out, and cement mortar is poured into the inner cavity of the inner sleeve so that the entire anchor is wrapped with slurry, and the anchor is bonded to the wall of the drilled hole all around, which greatly improves the bonding force between the anchor in the anchoring area and the rock mass around the hole, and also increases the ultimate pull-out force of the anchor, effectively controlling the range of the extrusion surrounding rock loosening circle and the deformation of the support structure.

[0027] 2) The inner anchor head section of the anchor rod body of the present application is designed to be in a trumpet shape, which can effectively avoid the damage caused to the anchor head and the surrounding rock by the shock wave during micro-blasting, and can make the shock wave propagate linearly along the inner hole of the anchor rod without pushing out the entire anchor rod and affecting the anchoring effect.

[0028] 3) The anchoring method of the present application is to first perform resin grouting, then micro-blasting, and then cement mortar 7 pouring. This method has the advantages of high safety, can effectively enhance the anchoring force between the anchor rod and the rock wall, and convenient material source.

[0029] 4) The anchor rod structure of the present application is simple, the anchoring method is concise, the overall construction cost is low, and it has good engineering applicability and economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a cross-sectional view of the micro-blasting grouting anchor rod of this application.

[0031] Figure 2 for Figure 1 Schematic diagram of the AA section.

[0032] Figure 3 for Figure 1 Schematic diagram of the middle BB cross section.

[0033] Figure 4 It is a structural diagram of the middle section 22 of the anchor rod body.

[0034] Figure 5 Schematic diagram of the drug core.

[0035] Figures 6-10 This is a process diagram of the anchoring method of this application.

[0036] Figure 11 for Figure 10 Schematic diagram of the CC cross section.

[0037] Among them, 1-fastener, 11-pad, 12-nut, 2-anchor body, 21-anchor head section, 22-middle section, 23-external section, 24-baffle, 25-grouting hole, 26-plum blossom hole, 3-blasting core, 4-sound-absorbing cotton, 5-protective frame, 51-bracket, 52-steel frame, 6-resin, 7-cement mortar, 8-loose surrounding rock around the anchor. DETAILED DESCRIPTION

[0038] The technical solution of the present invention will now be further described with reference to the accompanying drawings and embodiments.

[0039] Squeezable surrounding rock is also known as soft rock under high ground stress. When the strength-stress ratio of a squeezing surrounding rock tunnel is less than 0.3-0.5, it can produce deformation more than twice that of normal tunnel excavation. Therefore, its anchoring technology requirements are much more difficult than those of ordinary tunnels.

[0040] The micro-blasting grouting anchor rod provided by the present application, which is suitable for tunnels with extrusive surrounding rocks, mainly utilizes an outer sleeve and an inner sleeve to form a double-layer grouting anchor rod structure, and injects resin 6 into the interlayer between the outer sleeve and the inner sleeve. A plum blossom hole 26 is opened on the outer sleeve of the middle section 22 of the anchor rod body 2 to allow the resin 6 to seep out, and cement mortar 7 is injected into the inner cavity of the inner sleeve so that the entire anchor rod is wrapped with slurry, and the anchor rod is bonded to the wall of the drilled hole all around, thereby greatly improving the bonding force between the anchor rod in the anchoring area and the rock mass around the hole, and improving the ultimate pull-out force of the anchor rod, effectively controlling the range of the loosening circle of the extrusive surrounding rock and the deformation of the support structure.

[0041] See also Figures 1 to 5The micro-blasting grouting anchor bolt suitable for tunnels with extrusive surrounding rock, according to the present application, comprises an anchor bolt body 22 and a fastener 11. The anchor bolt body 2 is a double-layer jacketed structure formed by a hollow inner sleeve and an outer sleeve. A radially disposed baffle 24 connects the outer end of the outer sleeve to the inner sleeve, sealing the interlayer between the outer and inner sleeves. Grouting holes 25 are provided on the baffle 24, through which grouting liquid can be injected into the interlayer between the outer and inner sleeves. The anchor bolt body 2 comprises an anchor head section 21, a middle section 22, and an outer section 23, arranged in sequence. Specifically, the inner anchor head section 21 is designed as a flared shape, which prevents the micro-blasting shock wave from damaging the anchor head and surrounding rock, and allows the shock wave to propagate along the anchor bolt's inner bore without ejecting the anchor bolt. The ratio of the anchor head section 21 length to the total anchor bolt length is preferably 0.1 to 0.33:1. The inner anchor head section 21 is filled with a blasting core 3, and the blasting wire for the blasting core 3 is led through the interlayer between the inner and outer sleeves. To isolate the blasting core 3 from the cavity of the middle section 22 of the anchor body 2, it is filled with sound-absorbing cotton 4 after the blasting core 3 is installed. The thickness of the wadding is typically 45mm-50mm. The length of the middle section 22 of the anchor rod is 0.58:1 compared to the total length of the anchor rod. A plum blossom hole 26 is provided in the outer sleeve of the middle section 22. This allows slurry injected into the interlayer between the outer and inner sleeves to seep out through the plum blossom hole 26, bonding the anchor rod to the borehole wall. A fastener 1 is mounted on the outer anchor head section 21 of the anchor rod body 2 to secure the anchor rod 2 after installation. This fastener 1 comprises a backing plate 11 and a nut 12. The nut 12 is compatible with the backing plate 11 and fits over the outer sleeve, where it is threadedly connected. The diameter of the backing plate 11 is 8 to 100 mm, and the thickness is 6 to 10 mm. The inner hole diameter of the backing plate 11 is preferably 3 to 5 mm larger than the diameter of the anchor rod.

[0042] In order to prevent the anchor rod from being ejected during micro-blasting, a protective frame 5 is provided on the outside of the anchor rod body 2. The protective frame 5 is tightly connected to the pad 11. The protective frame 5 consists of a bracket 51 and a steel frame 52. One end of the bracket 51 is welded to the steel frame 52, and the other end is fixed to the pad 11. When the micro-blasting is completed, the bracket 51 is cut off, which has a better anti-ejection effect, especially for anchor rods at the arch top or arch waist position.

[0043] The anchoring method implemented by the micro-blasting grouting anchor rod suitable for squeezing surrounding rock tunnels of the present application specifically includes the following steps:

[0044] 1) Drilling and cleaning holes;

[0045] 2) Insert the inner anchor head section 21 containing the blasting core 3 in the anchor body 2 into the hole in step 1), lead the blasting lead through the interlayer between the inner sleeve and the outer sleeve, install the anchor body 2, and fasten it with the fastener 1;

[0046] 3) Grouting is injected into the cavity between the inner sleeve and the outer sleeve through the grouting hole 25. The grouting liquid seeps out through the plum blossom hole 26 of the outer sleeve, so that the anchor body 2 is bonded to the hole wall;

[0047] 4) After the slurry in step 3) reaches the designed strength, ignite the blasting fuse and perform micro-blasting;

[0048] 5) After the micro-blasting is completed, the inner sleeve is connected to the grouting machine, and secondary grouting is carried out through the internal cavity of the inner sleeve. Grouting is stopped when the grouting pressure at the hole mouth reaches 0.5-1.0 MPa, completing the micro-blasting grouting of the extrusion rock tunnel.

[0049] The slurry for secondary grouting is cement mortar 7 with cement: sand: water = 1: (1~1.5): (0.45~0.5), and the strength is not less than M10.

[0050] Example 1

[0051] The micro-blasting grouting anchor rod of this embodiment is suitable for squeezing surrounding rock tunnels and includes an anchor rod body 2 and a fastener 1. The anchor rod body 2 is made of Q235 steel. The total length of the anchor rod is 2500 mm, the inner anchor head length is 400 mm, the exposed length of the inner sleeve of the anchor rod is 250 mm, the wall thickness of the inner and outer sleeves is 3.0 mm, the inner sleeve diameter d1 is 25 mm, and the outer sleeve diameter d2 is 35 mm.

[0052] The outer end of the outer sleeve is connected to the inner sleeve by a radially arranged baffle 24. Grouting holes 25 with a diameter of 8 mm are provided in the baffle 24, allowing grout to be injected into the interlayer between the outer and inner sleeves. The inner anchor head section 21 is filled with a blasting core 3, which is continuously charged, 450 mm long, 24 mm in diameter, and has a blasting force of 800 mL. The blasting fuse for the blasting core 3 is led through the interlayer between the inner and outer sleeves. To isolate the blasting core 3 from the middle section 22 of the anchor body 2, the blasting core 3 is filled with sound-absorbing cotton 4 after filling, typically to a thickness of 47 mm. In the middle section 22, the outer sleeve is provided with a 9 mm diameter, 180 mm apart, pierced with a spherical pattern of holes 26. This allows slurry injected into the interlayer between the outer and inner sleeves to seep outward through the spherical pattern 26, bonding the anchor to the rock wall. A fastener 1 is installed on the outer section 23 of the anchor rod 2 to secure the anchor rod 2 after installation. The fastener 1 comprises a backing plate 11 and a nut 12. The nut 12 fits over the backing plate 11 and is threadedly attached to the outer sleeve. The backing plate 11 has a diameter of 100 mm and a thickness of 10 mm. The inner diameter of the backing plate 11 is preferably 5 mm larger than the diameter of the anchor rod.

[0053] The anchoring method implemented by the micro-blasting grouting anchor rod of the present application suitable for squeezing surrounding rock tunnels is shown in Figure 6-10 , specifically including the following steps:

[0054] 1) Use an anchor trolley or ordinary rock drill to drill a hole and use high-pressure water to clean the hole. The hole diameter should be slightly larger than the anchor diameter so that the anchor can be pushed in smoothly.

[0055] 2) A 400g charge consisting of No. 2 ammonium nitrate explosive and an electric detonator is placed inside the anchor head of the new anchor rod. The detonator is connected to a detonator leg wire, or blasting fuse, which is led to the outside of the anchor rod through the interlayer between the inner and outer sleeves. The charge is separated from the anchor rod's midsection 22 by 50mm thick polyester sound-absorbing cotton 4. The anchor rod body 2 is then installed, and the outer anchor head is tightened with a backing plate 11 and a nut 12.

[0056] 3) Resin 6 slurry is injected into the cavity between the inner sleeve and the outer sleeve through the grouting hole 25. The resin 6 slurry seeps out through the plum blossom hole 26 of the outer sleeve, so that the anchor body 2 is bonded to the hole wall;

[0057] 4) After the slurry from step 3) reaches the designed strength, ignite the blasting fuse and perform micro-blasting. During the blasting process, be careful not to stand on the end of the anchor rod. To prevent the anchor rod from being ejected during the micro-blasting process, an anti-ejection protective frame 5 is installed at the outer end of the anchor rod. The protective frame 5 is fixed to the base plate 11. Especially for anchor rods at the top or waist of the arch, the protective frame 5 includes a bracket 51 and a steel frame 52. One end of the bracket 51 is fixed to the base plate 11, and the other end is welded to the steel frame 52. After the micro-blasting is completed, the bracket 51 is cut off.

[0058] 5) After micro-blasting, connect the inner sleeve to the grouting machine and perform a secondary grouting of cement mortar 7 through the interlayer between the inner and outer sleeves. The cement: sand: water ratio is 1:1.2:0.48, and the strength is not less than M10. The grouting equipment should be in good condition, and the operating pressure should meet the grouting pressure requirements. An on-site test run should be conducted. Start the grouting equipment and grout until the orifice grouting pressure reaches 0.8 MPa. Stop grouting to prevent fracturing of the excavation surface.

[0059] Figure 11 The grouting effect diagram is shown in Figure 6, where 6 is resin 6, 7 is cement mortar 7, and 8 is loose surrounding rock 8 around the anchor rod. The entire anchor rod is wrapped in slurry, which forms a bond around the anchor rod and the borehole wall, greatly improving the bond between the anchor rod and the surrounding rock.

[0060] Example 2

[0061] The micro-blasting grouting anchor rod of this embodiment is suitable for extrusion rock tunnels and includes an anchor rod body 2 and a fastener 1. The anchor rod body 2 is made of Q235 steel. The total length of the anchor rod is 1500 mm, the inner anchor head length is 300 mm, the exposed length of the inner sleeve of the anchor rod is 150 mm, the wall thickness of the inner and outer sleeves is 2.5 mm, the inner sleeve diameter d1 is 19 mm, and the outer sleeve diameter d2 is 31 mm.

[0062] The outer end of the outer sleeve is connected to the inner sleeve by a radially arranged baffle 24. Grouting holes 25 with a diameter of 8 mm are provided in baffle 24, through which grouting liquid can be injected into the interlayer between the outer sleeve and the inner sleeve. The inner anchor head section 21 is filled with a blasting core 3, which is continuously charged, has a length of 400 mm, a diameter of 18 mm, and a blasting force of 640 mL. The blasting fuse of the blasting core 3 is led out through the interlayer between the inner and outer sleeves. To isolate the blasting core 3 from the middle section 22 of the anchor body 2, the blasting core 3 is filled with sound-absorbing cotton 4 after filling, typically to a thickness of 45 mm. The outer sleeve in the middle section 22 is provided with 8mm diameter, 150mm apart, and with a quincunx hole 26. This allows slurry injected into the interlayer between the outer and inner sleeves to seep outward through the quincunx holes 26, bonding the anchor bolt to the rock wall. A fastener 1 is mounted on the outer section 23 of the anchor bolt body 2 to secure the bolt body 2 after installation. This fastener 1 comprises a backing plate 11 and a nut 12. The nut 12 is mated to the backing plate 11 and fits over the outer sleeve, where it is threadedly connected.

[0063] The anchoring method implemented by the micro-blasting grouting anchor rod suitable for squeezing surrounding rock tunnels of the present application specifically includes the following steps:

[0064] 1) Use an anchor trolley or ordinary rock drill to drill a hole, and use high-pressure water to clean the hole. The hole diameter should be slightly larger than the anchor diameter, preferably 37mm, so that the anchor can be pushed in smoothly.

[0065] 2) A 300g charge consisting of No. 2 ammonium nitrate explosive and an electric detonator is placed at the anchor head of the new anchor bolt. The detonator is connected to a detonator leg wire, or blasting fuse, which is led to the outside of the anchor bolt through the interlayer between the inner and outer sleeves. The charge is separated from the anchor bolt's middle section 22 by a 45mm thick polyester sound-absorbing cotton 4. The anchor bolt body 2 is then installed, and the outer anchor head is tightened with a backing plate 11 and a nut 12. The backing plate 11 has an 80mm diameter and a thickness of 6mm. The inner diameter of the backing plate 11 is 3mm larger than the diameter of the anchor bolt. The inner anchor head is designed in a bell-shaped configuration, with a ratio of the smaller end diameter to the larger end diameter of 1:1.15 to 1.20. This design prevents shock wave damage to the anchor head and surrounding rock. It also allows shock waves to propagate along the anchor bolt's inner bore without dislodging the entire bolt.

[0066] 3) Grouting is injected into the cavity between the inner sleeve and the outer sleeve through the grouting holes 25. The grouting liquid seeps out through the plum blossom holes 26 on the wall of the outer sleeve, so that the anchor body 2 is bonded to the rock wall.

[0067] 4) After the slurry in step 3) reaches the designed strength, ignite the blasting fuse and perform micro-blasting.

[0068] 5) After micro-blasting, connect the inner sleeve to the grouting machine and perform a secondary grouting of cement mortar 7 through the interlayer 8 between the inner and outer sleeves. The cement mortar 7 should have a strength of no less than M10 and a cement:sand:water ratio of 1:1:0.45. The grouting equipment should be in good condition and the operating pressure should meet the grouting pressure requirements. An on-site test run should be conducted. Start the grouting equipment and grout until the orifice grouting pressure reaches 0.5 MPa. Stop grouting to prevent fracturing of the excavation surface.

[0069] Example 3

[0070] The micro-blasting grouting anchor rod of this embodiment is suitable for squeezing surrounding rock tunnels and includes an anchor rod body 2 and a fastener 1. The anchor rod body 2 is made of Q235 steel. The total length of the anchor rod is 3000 mm, the inner anchor head length is 500 mm, the exposed length of the inner sleeve of the anchor rod is 300 mm, the wall thickness of the inner and outer sleeves is 3.0 mm, the inner sleeve diameter d1 is 27 mm, and the outer sleeve diameter d2 is 39 mm.

[0071] The outer end of the outer sleeve is connected to the inner sleeve by a radially arranged baffle 24. This baffle 24 has a 10mm diameter plum blossom hole 26, through which grout can be poured into the interlayer between the outer and inner sleeves. The inner anchor head section 21 is filled with a blasting core 3, which is continuously charged, has a length of 500mm, a diameter of 26mm, and a blasting force of 960mL. The blasting fuse of the blasting core 3 is led through the interlayer between the inner and outer sleeves. To isolate the blasting core 3 from the middle section 22 of the anchor body 2, it is filled with sound-absorbing cotton 4 after the blasting core 3 is filled, typically to a thickness of 50mm. The outer sleeve in the middle section 22 is provided with 10mm diameter, 200mm-spaced, quincunx holes 26. This allows slurry injected into the interlayer between the outer sleeve and the inner sleeve to seep outward along the quincunx holes 26, bonding the anchor rod to the rock wall of the hole. A fastener 1 is mounted on the outer section 23 of the anchor rod body 2 to secure the anchor rod body 2 after installation. The fastener 1 comprises a backing plate 11 and a nut 12. The nut 12 is mated with the backing plate 11 and fits over the outer sleeve, where it is threadedly connected. The backing plate 11 has a diameter of 100mm and a thickness of 10mm. The inner diameter of the backing plate 11 is preferably 5mm larger than the diameter of the anchor rod.

[0072] The anchoring method implemented by the micro-blasting grouting anchor rod suitable for squeezing surrounding rock tunnels of the present application specifically includes the following steps:

[0073] 1) Use an anchor trolley or ordinary rock drill to drill a hole, and use high-pressure water to clean the hole. The hole diameter should be slightly larger than the anchor diameter, preferably 45mm, so that the anchor can be pushed in smoothly.

[0074] 2) A 450g charge consisting of No. 2 ammonium nitrate explosive and an electric detonator is placed at the anchor head within the new anchor bolt. The detonator is connected to a detonator leg wire, or blasting fuse, which is led to the outside of the anchor bolt through the interlayer between the inner and outer sleeves. The charge is separated from the anchor bolt's midsection 22 by 50mm thick polyester sound-absorbing cotton 4. The anchor bolt body 2 is then installed, and the outer anchor head is tightened with a backing plate 11 and a nut 12. The inner anchor head is designed in a bell-shaped configuration, with a ratio of the smaller end diameter to the larger end diameter of 1:1.15-1.20. This prevents shock wave damage to the anchor head and surrounding rock. Furthermore, this design allows shock waves to propagate along the anchor bolt's inner bore without dislodging the entire bolt.

[0075] 3) Grouting is injected into the cavity between the inner sleeve and the outer sleeve through the grouting holes 25. The grouting liquid seeps out through the plum blossom holes 26 on the wall of the outer sleeve, so that the anchor body 2 is bonded to the rock wall.

[0076] 4) After the slurry in step 3) reaches the designed strength, ignite the blasting fuse and perform micro-blasting; during the blasting process, be careful not to stand at the end of the anchor rod.

[0077] 5) After micro-blasting, connect the inner sleeve to the grouting machine and perform a secondary grouting of cement mortar 7 through the interlayer between the inner and outer sleeves. The cement mortar 7 should have a ratio of cement: sand: water = 1:1.5:0.5 and a strength of no less than M10. The grouting equipment should be in good condition and the operating pressure should meet the grouting pressure requirements. An on-site test run should be conducted. Start the grouting equipment and grout until the orifice grouting pressure reaches 1.0 MPa. Stop grouting to prevent fracturing of the excavation surface.

[0078] The resin 6 used in the primary grouting described in the above embodiment can also be replaced with polyurethane, and the cement-sand-water ratio used in the secondary grouting can be adjusted within the range described in the above embodiment, depending on the surrounding rock quality. The specific liquid agent used in the blasting core 3 can also be replaced with other blasting agents.

[0079] The above content is a further detailed description of the present invention in conjunction with specific preferred embodiments and is not intended to limit the present invention. For those skilled in the art, several simple deductions or replacements can be made without departing from the concept of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be deemed to fall within the scope of patent protection of the present invention as determined by the submitted claims.

Claims

1. A micro-blasting grouting anchor suitable for tunnels with extrusive surrounding rocks, characterized in that: The invention comprises an anchor rod body (2) and a fastener (1), wherein the anchor rod body (2) is a double-layer jacketed structure formed by sleeves of a hollow inner sleeve and an outer sleeve, and the anchor rod body (2) comprises an inner anchor head section (21), a middle section (22) and an outer section (23) arranged in sequence, the inner anchor head section (21) of the anchor rod body (2) being in a trumpet shape, a plum blossom hole (26) being provided on the outer sleeve of the middle section (22), a baffle (24) being provided radially between the outer end of the outer sleeve and the inner sleeve, and a grouting hole (25) being provided on the baffle (24); the fastener (1) being provided on the outer side of the outer section (23); a blasting core (3) being filled in the inner anchor head section (21) of the anchor rod body (2), a blasting lead of the blasting core (3) being led out through the interlayer between the inner sleeve and the outer sleeve; a sound-absorbing cotton layer being provided at the outer end of the blasting core (3) for blocking; Resin (6) slurry is poured into the cavity between the inner sleeve and the outer sleeve; and cement mortar (7) is poured into the inner cavity of the inner sleeve.

2. The micro-blasting grouting anchor suitable for squeezing surrounding rock tunnels according to claim 1 is characterized in that: The ratio of the length of the inner anchor head section (21) of the anchor rod body (2) to the total length of the anchor rod is 0.1-0.33:

1.

3. The micro-blasting grouting anchor suitable for squeezing surrounding rock tunnels according to claim 2 is characterized in that: The ratio of the length of the middle section (22) of the anchor rod body (2) to the total length of the anchor rod is 0.58:

1.

4. The micro-blasting grouting anchor suitable for squeezing surrounding rock tunnels according to claim 3 is characterized by: A protective frame (5) is provided outside the anchor rod body (2), and the protective frame (5) is connected to the fastener (1); the fastener (1) comprises a backing plate (11) and a nut (12), and the nut (12) is matched with the backing plate (11) and is sleeved on the outer sleeve and threadedly connected to the outer sleeve.

5. The micro-blasting grouting anchor suitable for squeezing surrounding rock tunnels according to claim 4 is characterized in that: The cement mortar (7) has a ratio of cement: sand: water = 1: (1-1.5): (0.45-0.5).

6. An anchoring method suitable for tunnels with extrusive surrounding rock, characterized by: The micro-blasting grouting anchor bolt suitable for a tunnel with extrudable surrounding rock according to any one of claims 2 to 4 is implemented, specifically comprising the following steps: 1) Drilling and cleaning holes; 2) Insert the flared inner anchor head section (21) containing the blasting core (3) in the anchor rod body (2) into the hole in step 1), lead the blasting lead through the interlayer between the inner sleeve and the outer sleeve, install the anchor rod body (2), and fasten it with the fastener (1); 3) Grouting is injected into the cavity between the inner sleeve and the outer sleeve through the grouting hole (25), and the grouting liquid seeps out through the plum blossom hole (26) of the outer sleeve, so that the anchor rod body (2) is bonded to the hole wall; 4) After the slurry in step 3) reaches the designed strength, ignite the blasting fuse and perform micro-blasting; 5) After the micro-blasting is completed, the inner sleeve is connected to the grouting machine, and secondary grouting is carried out through the internal cavity of the inner sleeve. Grouting is stopped when the grouting pressure at the hole mouth reaches 0.5~1.0MPa, completing the micro-blasting grouting of the extrusion rock tunnel.

7. The anchoring method for a tunnel with extrudable surrounding rock according to claim 6, characterized in that: The step 2) is specifically as follows: 2.1) A blasting core (3) consisting of No. 2 ammonium nitrate explosive and an electric detonator is placed in the anchor head section (21) of the anchor rod body (2). The electric detonator is connected to a blasting lead, which is led out through the interlayer between the inner sleeve and the outer sleeve. A sound-absorbing cotton layer is provided at the outer end of the blasting core (3) for blocking; 2.2) Insert the inner anchor head section (21) containing the blasting core (3) in the anchor rod body (2) into the hole in step 1), install the anchor rod body (2), and fasten it with the fastener (1) so that the blasting shock wave propagates inward along the anchor rod body (2).

8. The anchoring method for a tunnel with extrudable surrounding rock according to claim 6, characterized in that: The step 3) specifically comprises: pouring resin (6) into the cavity between the inner sleeve and the outer sleeve through the grouting hole (25); the resin (6) slurry seeps out through the plum blossom holes (26) on the wall of the outer sleeve, so that the anchor rod body (2) is bonded to the hole wall.

9. The anchoring method for a tunnel with extrudable surrounding rock according to claim 6, characterized in that: The step 5) is specifically as follows: after the micro-blasting is completed, the inner sleeve is connected to the grouting machine, and secondary grouting is performed through the internal cavity of the inner sleeve. The slurry for the secondary grouting is a cement mortar (7) with a ratio of cement: sand: water = 1: (1-1.5): (0.45-0.5), and the strength is not less than M10. The secondary grouting is completed before the initial setting, and the grouting is stopped when the grouting pressure at the hole mouth reaches 0.5-1.0 MPa, thereby completing the micro-blasting grouting of the extrusion surrounding rock tunnel.

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