Method and device for reinforcing expansive soil slope based on novel anchor rods

Abstract

The invention discloses a method and device for reinforcing an expansive soil slope based on a novel anchor rod, and relates to the technical field of geotechnical engineering.The device comprises a novel anchor rod assembly, the novel anchor rod assembly comprises an anchor rod body, an anchoring section and a free section, the surface of the anchoring section is provided with a concave-convex structure, and the surface of the free section is coated with an anti-corrosion coating; the grouting pipe is used for injecting cement mortar into the anchor hole; and the tensioning equipment comprises a hydraulic jack and a locking device, and the tensioning equipment is used for tensioning and locking the anchor rod body. The spiral or annular concave-convex structure on the surface of the anchoring section is embedded into a soil body, the contact area and frictional resistance are increased, a multistage anti-pulling mechanism is formed in combination with the segmented expansion head and the radial grooves in the surface, slippage caused by repeated expansion and shrinkage of expansive soil can be resisted, the contact area of the anchor rod and the soil body is increased through the concave-convex structure, and the anchoring force is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of geotechnical engineering, and particularly relates to a method and device for reinforcing expansive soil slopes based on a new type of anchor rod. Background Art

[0002] Expansive soil is a special soil with significant swelling and shrinkage characteristics. Its characteristics of absorbing water and swelling, and losing water and shrinking can easily lead to slope instability and threaten engineering safety. Traditional methods for reinforcing expansive soil slopes, such as gravity retaining walls and anti-slide piles, have disadvantages such as high construction difficulty, high cost, and large environmental impact.

[0003] In recent years, the anchor rod reinforcement technology has been widely used in the reinforcement of expansive soil slopes due to its advantages such as convenient construction, economy and high efficiency. However, traditional anchor rods have the following deficiencies in the expansive soil environment: insufficient anchoring force, the swelling and shrinkage characteristics of expansive soil will cause stress relaxation between the anchor rod and the soil mass, reducing the anchoring force; poor durability, chemical substances in the expansive soil will corrode the anchor rod, affecting its long-term stability; large environmental impact, noise, dust, etc. generated during the construction of traditional anchor rods will pollute the environment. Summary of the Invention

[0004] The purpose of the present invention is to provide a method and device for reinforcing expansive soil slopes based on a new type of anchor rod to solve the problems existing in the above background art.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A device for reinforcing an expansive soil slope based on a new type of anchor rod includes a new type of anchor rod assembly. The new type of anchor rod assembly includes an anchor rod body, an anchoring section, and a free section. The surface of the anchoring section is provided with a concave-convex structure, and the surface of the free section is coated with an anti-corrosion coating;

[0007] A grouting pipe for injecting cement mortar into the anchor hole;

[0008] Tensioning equipment including a hydraulic jack and a locking device for tensioning and locking the anchor rod body.

[0009] As a further scheme of the present invention: one end of the anchoring section is provided with an end partial enlarged head, and a PVC sleeve is sleeved outside the anchor rod body.

[0010] As a further scheme of the present invention: the grouting pipe extends along the anchor rod body to the bottom of the anchor hole, and grouting holes are distributed on the surface of the anchoring section.

[0011] As a further scheme of the present invention: the locking device includes a pedestal, a bearing plate, and an anchor fitting. The bearing plate is arranged perpendicular to the anchor rod body and fixed by the anchor fitting.

[0012] As a further solution of the present invention: the tensioning device is connected to the retaining structure at the end of the anchor rod body, and the rope remains in a relaxed state during the tensioning process.

[0013] As a further solution of the present invention: the anti-corrosion coating is a corrosion-resistant polymer coating and covers the entire length of the free section;

[0014] The concave-convex structures are distributed at intervals along the anchorage section to increase the contact area with the soil.

[0015] A method for reinforcing an expansive soil slope based on a new type of anchor rod includes the following steps:

[0016] S1: Trim and clean the slope surface of the expansive soil slope. Excavating the vertical surface of the slope at the anchorage point can make the bearing plate perpendicular to the anchor rod body;

[0017] S2: Determine the drilling position by measuring and lofting with a total station. After drilling, use high-pressure air to remove the slag in the hole;

[0018] S3: Bind the anchor rod body to the grouting pipe, and drive the new type of anchor rod assembly to the bottom of the hole to ensure that the anti-corrosion coating is not damaged;

[0019] S4: Inject cement mortar from the bottom of the anchor hole until the specific gravity of the empty slurry is the same as that of the injected slurry;

[0020] S5: After the slurry solidifies, use a hydraulic jack to tension the anchor rod body and record the pulling parameters. After reaching the predetermined load, lock the anchor rod body;

[0021] S6: Carry out anti-rust treatment on the end of the anchor rod body and backfill and compact the slope surface, and cover with a geomembrane

[0022] S7: Lay a protective net on the slope surface and sow grass seeds

[0023] As a further solution of the present invention: in S2, the longitudinal and transverse direction errors of the drilling do not exceed ±300 mm, and the drill is stabilized for 1-2 minutes after drilling is completed.

[0024] As a further solution of the present invention: in S4, the cement mortar uses ordinary Portland cement with a strength grade of 42.5 MPa, the sand particle size is not greater than 2.5 mm, and the compressive strength of the slurry is not less than 15 MPa.

[0025] As a further solution of the present invention: in S6, the construction notch at the bottom of the bearing plate is backfilled and compacted with earth and stone materials, and the surface of the bearing plate is treated with anti-rust by plain concrete.

[0026] The beneficial effects of the present invention:

[0027] (1) In the present invention, the helical or annular concave-convex structure on the surface of the anchorage section is embedded in the soil body, increasing the contact area and frictional resistance. Combining with the segmented enlarged head and the radial grooves on the surface, a multi-level anti-pulling mechanism is formed, which can resist the slip caused by the repeated swelling and shrinking of expansive soil. The concave-convex structure increases the contact area between the anchor rod and the soil body, improving the anchoring force;

[0028] (2) In the present invention, the epoxy resin anti-corrosion coating covers the entire length of the free section. Cooperating with the PVC casing and butter sealing, it isolates groundwater and corrosive media, improving the anti-corrosion life, which is more than twice that of traditional anchor rods. The surface of the slip-on is treated with hard chromium plating and the serrated anti-slip grooves on the bearing plate reduce the risk of locking slip; the bottom drainage holes prevent water accumulation and corrosion, enhancing the overall life of the device. The anti-corrosion coating applied on the surface of the free section effectively prevents the corrosion of the anchor rod and enhances its durability;

[0029] (3) In the present invention, total station positioning and high-pressure hole cleaning ensure the integrity of the hole wall, reducing the rework rate; the control of grouting pressure combined with the optimization of the water-cement ratio improves the utilization rate of the grout, reducing material waste. The geomembrane covers the slope to block the intrusion of surface water. Cooperating with the three-dimensional protection net and grass seed spraying, the soil erosion rate is reduced, and the construction dust and noise pollution are reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be further described below with reference to the accompanying drawings.

[0031] Figure 1 is the structural schematic diagram of the present invention Figure 1 ;

[0032] Figure 2 is the construction flow chart of the present invention;

[0033] Figure 3 is the structural schematic diagram of the present invention Figure 2 .

[0034] In the figure: 1, end part segmented enlarged head; 2, PVC casing; 3, grouting hole; 4, retaining structure; 5, anchor rod body; 6, pedestal; 7, bearing plate; 8, anchor; 9, cement mortar; 10, grouting pipe; 11, tensioning equipment; 12, anchorage section; 13, free section; 14, concave-convex structure; 16, anti-corrosion coating. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0036] Embodiment 1

[0037] Please refer to Figure 1 - Figure 3 As shown, the present invention is a device for reinforcing expansive soil slopes based on a new type of anchor rod, including a new type of anchor rod assembly. The new type of anchor rod assembly includes an anchor rod body 5, an anchorage section 12 and a free section 13. The surface of the anchorage section 12 is provided with a concave-convex structure 14, and the surface of the free section 13 is coated with an anti-corrosion coating 16;

[0038] A grouting pipe 10, which is used to inject cement mortar 9 into the anchor hole;

[0039] A tensioning device 11, which includes a hydraulic jack and a locking device, and is used to tension and lock the anchor rod body 5.

[0040] It should be noted that the height of the concave-convex structure 14 is 2-5 mm, and the spacing is 80-150 mm. By increasing the contact area and mechanical biting force between the anchor rod and the surrounding soil, the anchoring force is significantly improved. During the swelling and shrinking process of the expansive soil, the concave-convex structure can be embedded in the soil to resist the slip of the anchor rod.

[0041] In the present invention, preferably, the anchorage section 12 is provided with an end partial enlarged head 1, and the diameter of the end partial enlarged head 1 increases from the end of the anchorage section 12 towards the free section, with an increasing rate of 10% - 15%. And the surface of the end partial enlarged head 1 is provided with a radial groove (the groove depth is 1-2 mm, and the width is 3-5 mm) to further increase the bonding area with the grouting body; the thickness of the PVC sleeve 2 sleeved outside the anchor rod body 5 is 2-3 mm, and both ends of the PVC sleeve 2 are treated with heat shrinkage sealing to prevent the slurry from seeping into the free section.

[0042] It should be noted that the diameter of the end of the anchorage section 12 is enlarged in segments at an increasing rate of 10% - 15%. The surface of the enlarged head is provided with a radial groove (depth 1-2 mm, width 3-5 mm), which further increases the bonding area with the grouting body, forms multi-level anti-pulling resistance, and enhances the stability of the anchor rod under the repeated deformation of the expansive soil;

[0043] The free section 13 is sleeved with a PVC sleeve 2 with a thickness of 2-3 mm. Both ends of the sleeve are treated with heat shrinkage sealing, and butter is filled between the sleeve and the rod body to form a double waterproof barrier to prevent the grouting liquid from seeping into the free section and interfering with the prestress transfer.

[0044] In the present invention, preferably, the grouting pipe 10 extends along the anchor rod body 5 to the bottom of the anchor hole. The grouting holes 3 are obliquely distributed at 45° on the surface of the anchorage section 12, with a hole diameter of 5-8 mm, and the spacing of the grouting holes 3 is 100-150 mm;

[0045] The end of the grouting pipe 10 is provided with an annular diffuser, and the outer diameter of the diffuser is 80% - 90% of the borehole diameter, so as to ensure that the grout uniformly penetrates along the circumferential direction of the anchorage section 12 and fills the hole wall gap, ensuring that the grout uniformly penetrates along the circumferential direction of the anchorage section, fills the soil fissures and the hole wall gap, and forms a continuous and dense grouted body.

[0046] In the present invention, preferably, the locking device includes a pedestal 6, a bearing plate 7 and an anchor 8. The bearing plate 7 is arranged perpendicular to the anchor rod body 5 and fixed by the anchor 8; the contact surface between the bearing plate 7 and the slope surface is provided with serrated anti-slip grooves (groove depth 2 - 3 mm, groove spacing 10 - 15 mm), and a drain hole (hole diameter 5 - 10 mm) is provided at the bottom of the bearing plate 7 to prevent the corrosion of the bearing plate 7 caused by accumulated water;

[0047] The anchor 8 is internally embedded with a wedge, the surface of the wedge is provided with anti-slip lines (line depth 0.5 - 1 mm), and the contact surface between the wedge and the anchor rod is treated with hard chromium plating to enhance the locking stability and anti-slip performance.

[0048] In the present invention, preferably, the tensioning device 11 is connected to the retaining structure 4 at the end of the anchor rod body 5, and the rope remains in a relaxed state during the tensioning process.

[0049] In the present invention, preferably, the anti-corrosion coating 16 is a corrosion-resistant polymer coating and covers the entire length of the free section 13;

[0050] The concave-convex structure 14 is distributed at intervals along the anchorage section 12 to increase the contact area with the soil.

[0051] It should be noted that the tensioning device 11 is connected to the retaining structure 4 at the end of the anchor rod body 5, and the rope remains in a relaxed state during the tensioning process; the retaining structure 4 is made of high-strength alloy steel, and its surface is coated with a wear-resistant coating (thickness 0.2 - 0.3 mm) to extend the service life and isolate the erosion of groundwater and corrosive media.

[0052] Embodiment 2

[0053] A method for reinforcing an expansive soil slope based on a new type of anchor rod includes the following steps:

[0054] S1: Trim and clean the slope surface of the expansive soil slope. Excavating the vertical surface of the slope at the anchoring point can make the bearing plate 7 perpendicular to the anchor rod body 5;

[0055] S2: Determine the drilling position by total station measurement and lofting. After drilling, use high-pressure air to remove the slag in the hole;

[0056] S3: Bind the anchor rod body 5 to the grouting pipe 10, and drive the new type of anchor rod assembly to the bottom of the hole to ensure that the anti-corrosion coating 16 is not damaged;

[0057] S4: Inject cement mortar 9 from the bottom of the anchor hole until the specific gravity of the empty grout is the same as that of the injected grout;

[0058] After the grout solidifies, use a hydraulic jack to tension the anchor rod body 5 and record the pulling parameters. After reaching the predetermined load, lock the anchor rod body 5.

[0059] S6: Perform anti-rust treatment on the end of the anchor rod body 5 and compact the slope surface backfill, covering it with a geomembrane.

[0060] S7: Lay a protective net on the slope surface and sow grass seeds.

[0061] In the present invention, preferably, the longitudinal and transverse direction errors of the drilling in S2 do not exceed ±300 mm, and after the drilling is completed, the drill is stabilized for 1 - 2 minutes.

[0062] In the present invention, preferably, the ordinary Portland cement with a strength grade of 42.5 MPa is used for the cement mortar 9 in S4, the sand particle size is not greater than 2.5 mm, and the compressive strength of the grout is not less than 15 MPa.

[0063] In the present invention, preferably, the construction notch at the bottom of the bearing plate 7 in S6 is backfilled and compacted with earth and stone materials, and the surface of the bearing plate 7 is treated with plain concrete for anti-rust.

[0064] Implementation process:

[0065] S1: Slope trimming, trim the expansive soil slope, and clean the weeds and other obstacles on the slope surface to make it meet the requirements of the design slope and slope surface flatness. Excavate a vertical surface in the anchoring direction on the slope surface at the anchoring point to ensure that the bearing plate 7 is perpendicular to the anchor rod body 5.

[0066] S2: Drilling, before placing the drill rig, use a total station to measure and set out according to the construction design drawings to determine the hole position and the azimuth angle of the anchor hole. Accurately measure and mark the anchor hole position on the slope surface. The longitudinal and transverse direction errors of the hole position on the slope surface shall not exceed ±300 mm. The drilling hole diameter and hole depth requirements shall not be less than the design values. According to the size of the anchor head, the drilling hole diameter is about 110 - 130 mm, and the actual drill bit diameter used shall not be less than the design diameter. To ensure the anchor hole depth, it is required that the actual drilling depth is more than 200 mm deeper than the design depth. After drilling to the design depth, do not stop the drill immediately. It is required to stabilize the drill for 1 - 2 min. There shall be no dust residue and water body adhesion on the hole wall of the drilling, and it must be cleaned thoroughly. After the drilling is completed, the rock powder, soil slag and water body in the hole can be removed to the outside of the hole by using high-pressure air (wind pressure about 0.3 MPa).

[0067] S3: Anchor installation, tie the grouting pipe 10 on the anchor rod body 5, put the anchor head at the bottom of the hole. Before lowering the anchor, check the length dimensions and processing quality of the anchor head and connecting rod parts of the anchor rod to ensure that they meet the design requirements. Manually drive the anchor head to reach the bottom of the hole. During the driving process, prevent torsion, compression and bending, and at the same time, do not damage the anti-corrosion layer of the anchor rod, and do not knock randomly after lowering the anchor.

[0068] S4: Grouting. Pressurized grouting is adopted to grout all the anchor holes from bottom to top to form a complete grouted body. The grouting pipe is placed at the bottom of the anchor body 5, and after the new-type anchor is placed in the designated position, cement mortar 9 is injected. The cement mortar 9 is preferably ordinary Portland cement with a strength grade of 42.5 MPa. The quality of the mixing water, and the admixtures in the slurry should not contain substances that are corrosive to the anchor. The sand used for mixing is natural sand with a hard texture, its particle size should not be greater than 2.5 mm, and the fineness modulus should not be greater than 2.0. The compressive strength of the grouting liquid should not be lower than 15 MPa, and the water-cement ratio of the slurry should be controlled within the range of 0.35 - 0.5. The slurry should be stirred evenly and have good fluidity. The slurry should be used immediately. The grouting pressure is determined according to experiments and generally should not exceed 0.25 MPa. When the specific gravity of the slurry discharged from the hole mouth is the same as that of the injected slurry, the grouting can be stopped.

[0069] S5: Tensioning and locking. After the slurry has solidified, a hydraulic jack is used at the 3 grouting holes to tension the new-type anchor. During the tensioning process, the pulling force, the upward displacement of the anchor body 5, the pulling load, and the holding time should all meet the requirements. When the tensioning reaches the predetermined load and the displacement is stable, the tensioning can be stopped. During this process, the rope connecting the anchor plate of the winch should be kept in a slack state. When the anchor plate has opened during the pulling process and provides the required anchoring force for the project and the displacement is stable, the anchor body 5 can be locked at the 3 grouting holes to ensure that the new-type anchor provides the required anchoring force for strengthening the slope. The prestress locking value of the new-type anchor should be determined according to the specific slope conditions of the project. It is necessary to pre-place the locking device, and the locking jaws are embedded in the socket to complete the tensioning and locking of the new-type anchor.

[0070] S6: End protection. After the grouting and the tensioning and locking of the anchor body 5 are completed, necessary anti-rust and compaction treatment measures need to be taken for the end of the anchor body 5. The upper surface of the bearing plate 7 needs to be poured with plain concrete for anti-rust treatment. If the slope angle is not perpendicular to the embedding angle of the anchor, it is necessary to excavate and adjust the slope angle of the lower surface of the bearing plate 7. After the construction is completed, a construction notch will be formed at the bottom of the bearing plate 7. At this time, the backfilling method with earth and stone materials can be used for supplementary compaction, and at the same time, the slope surface is covered with a geomembrane to prevent surface stones from invading the slope.

[0071] S7: Slope protection. A protective net is laid on the slope surface and grass seeds are sown (sowing at a standard of 25 g per square meter) to prevent the slope surface from weathering and peeling, and improve the stability of the slope and the soil and water conservation capacity.

[0072] The above has described a specific embodiment of the present invention in detail, but the content described is only the preferred embodiment of the present invention and cannot be considered as limiting the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of the application of the present invention should still fall within the scope covered by the patent of the present invention.

Claims

1. An apparatus for reinforcing an expansive soil slope based on a new type of anchor rod, characterized in that Including a new type of anchor rod assembly, the new type of anchor rod assembly includes an anchor rod body (5), an anchoring section (12) and a free section (13). The surface of the anchoring section (12) is provided with a concavo-convex structure (14), and the surface of the free section (13) is coated with an anti-corrosion coating (16); A grouting pipe (10), which is used to inject cement mortar (9) into the anchor hole; Tensioning equipment (11), the tensioning equipment (11) includes a hydraulic jack and a locking device, and the tensioning equipment (11) is used to tension and lock the anchor rod body (5).

2. The device for reinforcing an expansive soil slope based on a new type of anchor rod according to claim 1, wherein One end of the anchoring section (12) is provided with an end partial expansion head (1), and a PVC casing (2) is sleeved outside the anchor rod body (5).

3. The device for reinforcing an expansive soil slope based on a new type of anchor rod according to claim 1, characterized in that, The grouting pipe (10) extends along the anchor rod body (5) to the bottom of the anchor hole, and grouting holes (3) are distributed on the surface of the anchoring section (12).

4. The device for reinforcing an expansive soil slope based on a new type of anchor rod according to claim 1, wherein, The locking device includes a pedestal (6), a bearing plate (7) and an anchor (8), and the bearing plate (7) is arranged perpendicular to the anchor rod body (5) and fixed by the anchor (8).

5. The device for reinforcing an expansive soil slope based on a new type of anchor rod according to claim 1, characterized in that, The tensioning equipment (11) is connected to the retaining structure (4) at the end of the anchor rod body (5), and the rope remains in a slack state during the tensioning process.

6. The device for reinforcing an expansive soil slope based on a new type of anchor rod according to claim 1, characterized in that, The anti-corrosion coating (16) is a corrosion-resistant polymer coating and covers the entire length of the free section (13); The concavo-convex structure (14) is distributed at intervals along the anchoring section (12) to increase the contact area with the soil body.

7. Method for reinforcing expansive soil slope based on new type anchor rod, characterized in that, An apparatus for reinforcing an expansive soil slope based on a new type of anchor rod according to any one of claims 1-6, comprising the following steps: S1: Trim and clean the slope surface of the expansive soil slope. Excavating the vertical surface of the anchoring point slope surface can make the bearing plate (7) perpendicular to the anchor rod body (5); S2: Determine the drilling position by total station measurement and layout. After drilling, use high-pressure air to remove the slag in the hole; S3: Tie the anchor rod body (5) to the grouting pipe (10), and drive the new type of anchor rod assembly into the bottom of the hole to ensure that the anti-corrosion coating (16) is not damaged; S4: Inject cement mortar (9) from the bottom of the anchor hole until the specific gravity of the empty slurry is the same as that of the injected slurry; S5: After the slurry solidifies, use a hydraulic jack to tension the anchor rod body (5) and record the pulling parameters. After reaching the predetermined load, lock the anchor rod body (5); S6: Perform rust prevention treatment on the end of the anchor rod body (5) and backfill and compact the slope surface, and cover with a geomembrane S7: Lay a protective net on the slope surface and sow grass seeds.

8. The method for reinforcing an expansive soil slope based on a new type of anchor rod according to claim 7, characterized in that, In S2, the longitudinal and transverse direction errors of the drilling do not exceed ±300 mm, and the drill is stabilized for 1-2 minutes after drilling is completed.

9. The method for reinforcing an expansive soil slope based on a new type of anchor rod according to claim 7, characterized in that, In S4, the cement mortar (9) uses ordinary Portland cement with a strength grade of 42.5 MPa, the sand particle size is not greater than 2.5 mm, and the compressive strength of the slurry is not less than 15 MPa.

10. The method for reinforcing an expansive soil slope based on a new type of anchor rod according to claim 7, characterized in that, In S6, the construction notch at the bottom of the bearing plate (7) is backfilled and compacted with earth and stone materials, and the surface of the bearing plate (7) is treated with rust prevention by plain concrete.

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