An anchoring structure for brick-clad city wall ruins based on EBTP anchor rods

Abstract

The invention discloses a brick-clad city wall ruins anchoring structure based on EBTP anchor rods, comprising EBTP anchor rods and brick-clad walls; steel bars are inserted into bamboo pipes, the length of the steel bars is greater than the length of the bamboo pipes, the steel bars are inserted into the bamboo pipe sections and extended into the anchoring sections in the rammed earth of the city wall, the steel bars extend out of the bamboo pipe sections and extend into the anchoring sections in the brick-clad walls, the steel bars are inserted out of the outer end face of the brick-clad walls and fixed by bolts and anchor plates; the expanded anchor section is arranged in the middle section of the steel bars in the bamboo pipes, and is located between the pressure section and the tension section of the brick-clad walls. The critical anchoring length is multiplied and the ultimate pull-out bearing capacity is greatly improved through the transformation of multiple force transmission modes, and the structure can meet the anchoring requirements of large rammed earth ruins structures such as brick-clad city walls and rammed earth city walls.

Description

Technical Field

[0001] The invention belongs to the technical field of reinforcement and protection of rammed earth building ruins, and particularly relates to a brick-clad city wall ruins anchoring structure based on EBTP anchor rods, which is used to enhance the stability and earthquake resistance of large rammed earth ruins structures such as brick-clad city walls. Background Art

[0002] As a typical historical architectural relic in my country with a magnificent scale, huge reserves and wide distribution, the brick-clad city wall embodies the ancient people's superb architectural concepts and exquisite construction skills. It is a reflection of my country's brilliant historical civilization and cultural roots, and has extremely high scientific significance and social value. The brick-clad city wall is mainly composed of internal rammed earth and external bricks. Since it was mostly used for military defense in ancient times, it is usually tall. The ductility of the internal rammed earth and external brick materials is poor, and the strength of the two types of materials is quite different. The masonry time is also different, and the deformation of the two is difficult to coordinate. In addition, the structure was not designed for earthquake resistance during construction, which makes it very easy for the structure to slip, collapse and other damages under the action of external forces such as earthquakes, resulting in the permanent loss of the site relics themselves and the historical and cultural information they carry. In response to this problem, cultural relics protection workers mainly use "anchoring" technology to covertly enhance its stability based on the reinforcement principle of "safety first, minimal intervention, and no change to the original appearance". That is, drilling holes on the surface of the site and implanting anchor rods, and injecting anchoring slurry into the holes to bond the anchor rods to the site body, thereby playing the role of connecting the dangerous body and the stable body, and avoiding instability and destruction of the site.

[0003] Rammed earth building sites have the dual attributes of architecture and cultural relics. The metal anchor rods (such as steel bars, etc.) commonly used in traditional rock and soil slope anchoring projects are not suitable for anchoring rammed earth sites. Specifically: 1. Metal anchor rods are prone to react with moisture to cause rust damage, so their durability is poor, and their service life is extremely short compared to the cultural relics in the site; 2. The strength difference between metal anchor rods and rammed earth materials is large, and the deformation of the two is difficult to coordinate, and the tensile performance of metal anchor rods cannot be fully utilized; 3. The cement mortar used in conjunction with metal anchor rods is prone to chemical reaction with the rammed earth materials of the site, and the compatibility of the two is poor; 4. In order to protect cultural relics, the use of prestressed technology is strictly restricted.

[0004] In view of this, cultural heritage workers, based on the investigation of the performance of wood materials in rammed earth buildings, through long-term exploration and practice, finally reached a consensus on enhancing the seismic stability of rammed earth sites by combining bamboo and wood rods with non-prestressed anchoring technology, and developed rammed earth site anchor rods based on natural materials such as "nanmu anchor rods" and "la wood anchor rods". However, a lot of practical experience shows that although anchor rods made of natural bamboo and wood materials can effectively solve the compatibility and durability problems between the rod body and the site, they still have the following disadvantages:

[0005] (1) Ordinary bamboo and wood poles have low tensile strength, and the shear strength of the anchor slurry used in conjunction with them is generally only slightly higher than that of the rammed earth. The bonding performance of the anchor interface is poor, so it is difficult to provide a high anchoring force and cannot meet the anchoring needs of large city wall sites.

[0006] (2) The current anchoring method used for ruins is mainly full-length bonded tension type. The stress distribution at the interface of this type of anchoring system is extremely uneven. The high stress area is mainly concentrated near the hole mouth. The interface bonding strength at different anchoring depths cannot be fully utilized, resulting in a short effective anchoring length and low anchoring efficiency.

[0007] (3) Ordinary bamboo and wood anchor rods have a simple structure, and it is difficult to select suitable anchoring agents based on the performance of different anchoring materials, thereby maximizing the bonding strength of different anchoring sections. Therefore, they are not completely applicable to sites such as brick-clad city walls that contain different materials such as bricks and rammed earth.

[0008] In summary, the metal anchor rods commonly used in traditional rock and soil slope anchoring and the bamboo and wood anchor rods commonly used in the current rammed earth site anchoring cannot meet the anchoring needs of brick-clad city wall sites well. Summary of the invention

[0009] In order to solve the above defects existing in the prior art, the purpose of the present invention is to provide an anchoring structure of a brick-clad city wall ruins with an expanded bamboo reinforcement tension-compression composite anchor rod (hereinafter referred to as: EBTP anchor rod) suitable for large rammed earth ruins such as city walls (especially brick-clad city wall ruins), so as to solve the problems of poor durability and compatibility of existing metal anchor rods, low pull-out bearing capacity of natural bamboo and wood anchor rods, stress concentration at the anchoring interface, and easy to cause insufficient anchoring force of the ruins or local premature damage and destruction. Through the transformation of multiple force transmission modes, the critical anchoring length is doubled and the ultimate pull-out bearing capacity is greatly improved, and the performance advantages of different materials are fully utilized through the partition grouting technology.

[0010] The present invention is achieved through the following technical solutions.

[0011] The invention discloses an anchoring structure for a brick-clad city wall ruins based on an EBTP anchor rod, comprising an EBTP anchor rod and a brick-clad wall; the EBTP anchor rod comprises a steel bar, an anchor plate, a bamboo pipe and an expanded anchor section, the steel bar runs through the bamboo pipe, and the length of the steel bar is greater than the length of the bamboo pipe, the steel bar runs through the bamboo pipe section and extends into the anchor section in the rammed earth of the city wall, the steel bar extends out of the bamboo pipe section and extends into the anchor section in the brick-clad wall, the steel bar runs through the outer end surface of the brick-clad wall and is fixed by bolts and anchor plates; the expanded anchor section is arranged in the middle section of the steel bar in the bamboo pipe, and the expanded anchor section is located between the pressure section and the tension section of the brick-clad wall.

[0012] For the above technical solution, the present invention has a further preferred solution:

[0013] Furthermore, the anchoring section inside the brick cladding is from the hole on the outer facade of the brick cladding wall to the interface between the brick cladding wall and the rammed earth body, and the steel bars of the EBTP anchor rod are bonded to the brick cladding with cement mortar from the anchor plate to the steel bar section extending from the bamboo pipe.

[0014] The cement mortar is prepared by mixing cement and medium sand with water in a mass ratio of 15:85, and a water-cement ratio of 0.29.

[0015] Furthermore, the anchoring section in the rammed earth is from the interface between the brick-clad wall and the rammed earth body to the bottom end of the anchor hole, and the outer surface of the bamboo of the bamboo pipe section with steel bars passing through is bonded to the rammed earth body by using modified mud.

[0016] The modified mud is prepared by mixing scattered soil from the site, cement, fly ash, and glutinous rice paste with 5% silica sol, with the mass ratio of each component being 60:20:10:10 and the water-cement ratio being 0.31.

[0017] Furthermore, epoxy resin glue is poured into the tensile bamboo pipe to bond the inserted steel bars; epoxy resin glue is not poured into the pressure-bearing bamboo pipe.

[0018] Furthermore, the expanded anchor section includes a bearing plate and a triangular support body, the bearing plate is vertically welded along the radial direction of the steel bar, and the triangular support body is fixedly connected to the bearing plate and the steel bar along the axial direction of the steel bar respectively; a plurality of circular grouting holes are provided on the bearing plate.

[0019] Furthermore, a longitudinal sliding groove penetrating the triangular support body is provided in the middle section of the bamboo pipe.

[0020] Furthermore, the EBTP anchor rods are evenly arranged along the outer facade of the brick-clad wall, or are gradually densely arranged from bottom to top as the wall height increases.

[0021] Furthermore, the EBTP anchor rods are arranged in a plum blossom shape along the outer facade of the brick-clad wall, and adjacent rows of EBTP anchor rods are staggered by 1 / 3 to 1 / 2 of the spacing between the anchor rods.

[0022] Furthermore, the EBTP anchor rod is inserted into the brick-clad wall at an angle of 10 to 30 degrees to the horizontal plane and is inserted obliquely downward.

[0023] Furthermore, the expanded anchor sections between adjacent EBTP anchor rods are staggeredly arranged at different depths in the rammed earth body, and the axial spacing is 1 / 2 to 1 / 5 of the length of the anchoring section in the rammed earth.

[0024] The present invention adopts the above technical solution, which has the following beneficial effects:

[0025] The present invention will form an expanded bamboo reinforcement tension-compression composite anchor rod (EBTP anchor rod) with multi-layer and multi-anchoring section structural characteristics by adding steel bars and expanded anchor sections on the basis of traditional bamboo anchor rods. This anchor rod can not only ensure a higher pull-out bearing capacity of the anchoring system and a lower peak stress level of the anchoring interface, but also solve the low durability of the metal reinforcement and its compatibility with the soil.

[0026] The main technical problems that this solution can solve include:

[0027] (1) The anchoring section in the rammed earth of the present invention is divided into a shallow pressure-bearing section and a deep tension-bearing section, which can multiply the critical anchoring length, give full play to the shear resistance of the anchoring interface at different anchoring depths, greatly improve the pull-out bearing capacity of the anchor rod, and solve the problem of low strength and limited pull-out bearing capacity of bamboo and wood anchor rods.

[0028] (2) The expanded anchor section of the present invention can effectively enhance the mechanical bite force and reduce the interface slip, while improving the local interface bonding strength of adjacent anchor rods by disturbing and compacting the soil around the anchor, thereby compensating for the loss of anchoring efficiency caused by the group anchor effect and further improving the performance of the anchoring system.

[0029] (3) The use of zoned grouting (inside bricks and rammed earth) technology and multi-layer structure (rebar / bamboo) construction can not only optimize the performance of the inner anchoring section by selecting appropriate anchor slurry according to the material properties, but also ensure the deformation coordination and durability compatibility between the anchor rod and the site.

[0030] Since the EBTP anchor adopts the above structural features, combined with its working principle, it can be seen that the present invention has the following advantages:

[0031] 1) The shearing action between the modified mud and the rammed earth body in the pressure section of the rammed earth and the shearing action between the outer surface of the bamboo and the modified mud in the tension section will jointly resist the axial load of the anchor caused by the displacement of the brick-wrapped wall. Therefore, the critical anchoring length of the anchoring section in the rammed earth is the sum of the critical anchoring length of the pressure section and the critical anchoring length of the tension section. Compared with the traditional tension or pressure type anchoring system, the critical anchoring length will be doubled, which fully mobilizes the interface bonding strength at different anchoring depths, making the interface shear stress distribution more uniform and the pull-out bearing capacity higher;

[0032] 2) The embedding effect of the expanded anchor joint will increase the mechanical bite force, reduce the slippage of the anchor rod relative to the rammed earth body, and thus limit the relative displacement of the brick-clad wall and the rammed earth body, making the two firmly tied together;

[0033] 3) The movement and compaction of soil particles caused by the displacement of the expanded anchor section increases the soil pressure around the anchor rods, improves the bonding strength of the anchor interface and the ultimate pull-out bearing capacity of the anchor rods, and presents a synergistic enhancement mechanism between adjacent anchor rods, further improving the performance of the anchor system;

[0034] 4) Cement mortar and modified mud anchoring agent are used for zoning grouting in the brick wall and rammed earth respectively, which can give full play to the performance advantages of materials with different strengths;

[0035] 5) The stress transfer between the steel bars and the rammed earth is carried out through bamboo pipes. The bamboo can not only block the moisture in the rammed earth from reacting with the steel bars to cause rust damage, thus solving the problem of poor durability of the steel bars, but also gradually transfer the stress of the steel bars to the rammed earth through the bamboo and anchoring agent, avoiding the problem of deformation coordination caused by excessive strength differences between the materials, so that the stress can be evenly dissipated in the soil of the site, thereby ensuring the safety of the site itself.

[0036] In summary, compared with natural bamboo and wood anchors and metal anchors, EBTP anchors have significant mechanical performance advantages in the reinforcement and protection of brick-clad city wall ruins. This structure can meet the anchoring needs of large rammed earth ruins structures such as brick-clad city walls and rammed earth city walls. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of the present application, and do not constitute an improper limitation of the present invention. In the drawings:

[0038] Figure 1 It is a schematic diagram of the structure of the EBTP anchor rod in the present invention;

[0039] Figure 2 It is an AA cross-sectional view of the anchor joint of the EBTP anchor rod in the present invention;

[0040] Figure 3 This is a cross-sectional view of the EBTP anchor after installation in the brick-clad wall;

[0041] Figure 4 It is the connection diagram between the expanded anchor section and the steel bar;

[0042] Figure 5 This is a schematic diagram of the grooves in the bamboo tube wall;

[0043] Figure 6 It is a schematic diagram of the connection between the two-side support type bearing plates and the support body;

[0044] Figure 7 It is a schematic diagram of the connection between a four-side support type bearing plate and a support body;

[0045] Figure 8 It is a plane view of the connection between the two-side support type bearing plates and the support body;

[0046] Fig. 9 It is a plane view of the connection between the four-side support type bearing plate and the support body;

[0047] Fig.10 This is the layout of the EBTP anchors on the outer facade of the city wall;

[0048] Fig.11 It is a schematic diagram of the relative positions of the anchor sections of each EBTP anchor rod in the city wall.

[0049] In the figure: M.EBTP anchor rod, 1. steel bar, 2. bamboo pipe, 3. bearing plate, 3-1. grouting hole, 3-2. steel bar socket, 4. triangular support body, 4-1. weld, 5. epoxy resin glue, 6. modified mud, 7. cement mortar, 8. rammed earth of city wall, 9. brick-clad wall, 10. cavity, 11. bamboo node, 12. anchor plate, 13. bolt, 14. interface between brick-clad wall and rammed earth body, 15. longitudinal sliding groove, 16. anchoring section inside brick-clad wall, 17. anchoring section inside rammed earth, 18. pressure section, 19. tension section, 20. exterior facade of brick-clad city wall. DETAILED DESCRIPTION

[0050] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. The exemplary embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0051] like Figure 1 , Figure 2 As shown, the EBTP anchor rod M is mainly composed of a steel bar 1, a bamboo tube 2, an epoxy resin glue 5, an anchor plate 12, a bolt 13 and an expanded anchor section, and the expanded anchor section includes a bearing plate 3 and a triangular support body 4. Among them: the bearing plate 3 of the expanded anchor section is perpendicular to the axial direction of the steel bar 1, and the two are fixed by welding to the two right-angled sides of the triangular support body 4 connected to the steel bar 1. Figure 2 and Figure 4 As shown, the bearing plate 3 and the triangular support body 4 are fixed vertically to each other by the weld 4-1, wherein one of the two right-angled sides of the triangular support body 4 is welded to the surface of the steel bar 1, and the other is welded to the surface of the bearing plate 3. A pair of symmetrically distributed grouting holes 3-1 are provided on the bearing plate 3 for inserting a grouting pipe to inject modified mud into the gap between the bamboo and the rammed earth at the rear of the anchor section. Figure 2 The cross section from the center of the circle outwards is steel bar 1, epoxy resin glue 5, bamboo pipe 2, and bearing plate 3.

[0052] like Figure 1 , Figure 2 and Figure 3 As shown, in the anchoring structure of the brick-clad city wall ruins, a pair of steel bars 1 are centrally inserted into the bamboo pipe 2 with bamboo nodes 11 punched through, wherein the length of the steel bars 1 is greater than the length of the bamboo pipe 2, and the steel bars 1 penetrate through the bamboo pipe 2 and extend into the brick-clad wall.

[0053] According to the force transmission mode and force characteristics of this anchor rod, its entire length can be divided into two anchoring sections: 1) from the hole of the brick wall facade to the interface between the brick wall and the rammed earth body, it is the anchoring section inside the brick wall; 2) from the interface between the brick wall and the rammed earth body to the bottom of the anchor hole, it is the anchoring section inside the rammed earth body. Among them, the anchoring section inside the rammed earth body includes two force transmission modes, 1) from the interface 14 between the brick wall and the rammed earth body to the expanded body anchor joint is the pressure anchoring section, 2) from the expanded body anchor joint to the bottom of the anchor hole is the tension anchoring section.

[0054] The steel bar 1 penetrates through the bamboo pipe 2 and extends into the anchoring section 17 in the rammed earth of the city wall. The steel bar 1 extends out of the bamboo pipe and extends into the anchoring section 16 in the brick wrapping. The anchoring section 16 in the brick wrapping is from the hole on the facade of the brick wrapping wall to the interface between the brick wrapping wall and the rammed earth body. The steel bar 1 of the EBTP anchor rod is bonded to the brick wrapping with cement mortar 7 from the anchor plate 12 to the steel bar section extending out of the bamboo pipe. The anchoring section 17 in the rammed earth is from the interface between the brick wrapping wall 9 and the rammed earth body to the bottom of the anchor hole. The outer surface of the bamboo pipe section penetrated by the steel bar is bonded to the rammed earth body with modified mud 6. The steel bar penetrates out of the outer end face of the brick wrapping wall 9 and is fixed by bolts 13 and anchor plates 12; the expanded anchor section is set in the middle section of the steel bar in the bamboo pipe 2, and the expanded anchor section is located between the pressure section 18 and the tension section 19 of the brick wrapping wall. The steel bars 1 in the brick-wrapped anchor section 16 are not wrapped with the bamboo pipe 2, and in the rammed earth anchor section 17, there is an unbonded cavity 10 between the steel bars 1 in the front pressure-bearing section 18 and the bamboo pipe 2, and the steel bars 1 in the rear tension section 19 are bonded to the bamboo pipe 2 along their entire length with epoxy resin glue 5, and an expanded anchor section is provided at the junction of the pressure-bearing section 18 and the tension section 19.

[0055] like Figure 3 As shown, the connection relationship of the EBTP anchor rod M in the brick-clad city wall is as follows: the steel bar 1 in the anchoring section 16 in the brick-clad city wall is bonded to the wall bricks 9 by cement mortar 7, and the bamboo pipe 2 in the anchoring section 17 in the rammed earth is bonded to the wall rammed earth 8 by modified mud 6. After the EBTP anchor rod M is installed, an anchor plate 12 is installed on the outer surface of the city wall for protection, and the steel bar 1 and the anchor plate 12 are fixed with bolts 13.

[0056] like Figure 1 and Figure 5 As shown, all the bamboo nodes 11 inside the bamboo pipe 2 are opened except the last node, so that steel bars can be inserted into the center of the bamboo and glued with epoxy resin; a longitudinal sliding groove 15 is opened on the upper and lower parts of the surface of the bamboo pipe 2 at the front of the triangular support body 4 to ensure that the position of the bamboo pipe 2 in the pressure section 18 remains unchanged when the bearing body moves under tension.

[0057] like Figure 6 and Figure 8As shown, the bearing plate 3 of the expanded anchor section is vertically welded along the radial direction of the steel bar 1, and the triangular support body 4 is fixedly connected to the bearing plate 3 and the steel bar 1 along the axial direction of the steel bar 1; a plurality of circular grouting holes 3-1 are provided on the bearing plate 3. The length-to-height ratio of the triangular support body 4 is about 1:1, and the height is slightly smaller than the radius of the bearing plate 3, so as to enhance the bearing plate's anti-displacement and anti-deformation capabilities. In one embodiment, a two-side support type bearing plate 3 is vertically welded to the triangular support body 4 and fixed by a weld 4-1, a steel bar insertion hole 3-2 is provided in the middle of the bearing plate 3, and a grouting hole 3-1 is symmetrically provided on each of the bearing plates 3 on both sides of the triangular support body 4.

[0058] like Figure 7 and Fig. 9 As shown, in another embodiment, a four-sided support type bearing plate 3 is vertically welded to a triangular support body 4 and fixed by a weld 4-1. A steel bar insertion hole 3-2 is provided in the middle of the bearing plate 3, and a grouting hole 3-1 is provided in each of the four quadrants separated by the triangular support body 4 on the bearing plate 3.

[0059] like Fig.10 As shown, EBTP anchor rods M are arranged in a plum blossom shape on the outer facade of the brick-clad city wall 20. The positions of each row of EBTP anchor rods are staggered. The longitudinal spacing of each row is 10 times the diameter D of the bearing plate, that is, 10D. The horizontal spacing of adjacent longitudinal columns of anchor rods is 5 times the diameter D of the bearing plate, that is, 5D.

[0060] like Fig.11 As shown, when the EBTP anchor rod M is installed in the brick-clad city wall, it needs to pass through the brick-clad wall 9, and the bearing plate 3 is located deeper inside the rammed earth 8 of the city wall. If the length of the anchoring section 17 in the rammed earth of the city wall is L0, the bearing plates 3 of the two adjacent EBTP anchor rods M need to be staggered by 1 / 3L0 length along the axial direction of the anchor rod; when the EBTP anchor rod M is installed in the brick-clad city wall, it is inserted obliquely downward at an angle of 10° to the horizontal plane.

[0061] The position of the expanded anchor section can be dynamically adjusted according to the different installation locations in the brick-clad wall of the site. The expanded anchor sections between adjacent EBTP anchor rods should be staggered at different depths in the rammed earth, and the axial spacing should be 1 / 2 to 1 / 5 of the length of the anchor section in the rammed earth.

[0062] Furthermore, the diameter of the steel bar 1 should be slightly smaller than the inner wall diameter of the bamboo pipe 2, and it is appropriate to use Φ18-Φ28 threaded steel bars, which can also be replaced by steel strands.

[0063] The bamboo pipe 2 is preferably made of natural bamboo that is straight throughout and has no obvious damage. All bamboo nodes 11 inside the bamboo except the last node are drilled or split and hollowed out. After the bamboo nodes are opened by splitting, they should be restored to their original circular cross-section by pasting and wrapping carbon fiber cloth or tying steel wire.

[0064] Epoxy resin glue 5 should be high-strength weather-resistant glue for construction, with a tensile strength of not less than 65MPa, and no brittle failure should occur. Epoxy resin glue 5 should have excellent bonding strength and weather resistance, and its normal service life should not be less than the benchmark repair period of the city wall ruins.

[0065] The plane shape of the anchor plate 12 can be circular or square, and its diameter or side length is 3-6 times the diameter of the bearing plate 3. After installation, the anchor plate and the nut are covered with old to ensure its appearance is consistent with the original wall.

[0066] The modified mud 6 can be made by mixing the scattered soil of the ruins, cement, fly ash, and glutinous rice paste with 5% silica sol, with the mass ratio of each component being 60:20:10:10, and the water-cement ratio being 0.31, which can also be adjusted according to the strength of the rammed earth of the ruins. Its strength should be slightly higher than the shear strength of the rammed earth to ensure that the strength difference between the anchoring materials is within a small range, so that the deformation and stress transfer of the anchoring system are more reasonable.

[0067] Cement mortar 7 can be made by mixing cement and medium sand with water in a mass ratio of 15:85, with a water-cement ratio of 0.29. The strength and workability of the mortar can also be improved by increasing the amount of cement and adjusting the water-cement ratio, but the strength of the mortar after curing should not be lower than the M7.5 standard. Its strength should be slightly higher than the shear strength of the bricks in the brick-clad wall to ensure a higher bonding strength and a smaller relative amount of slip at the anchoring interface in the brick-clad wall.

[0068] The steel bar 1 should be inserted into the bamboo pipe 2 until the last bamboo node 11. The length of the steel bar 1 not wrapped by the bamboo pipe 2 should be the same as the thickness of the brick wall 9, and 5-15 cm should be left to connect and fix with the anchor plate 12 and bolts 13.

[0069] The longitudinal sliding groove of the bamboo pipe 2 is 50-100 mm long and its width is slightly larger than the thickness of the support body.

[0070] The connection method between the bearing plate 3 and the support body 4 can be a two-side support type or a four-side support type. The bearing plate 3 and the support body 4 are connected in a relationship in which their planes are perpendicular to each other. A grouting hole is arranged between each adjacent support body 4, and its diameter is larger than the diameter of the grouting pipe and smaller than 1 / 2 of the distance between the outer diameter of the bearing plate 3 and the outer diameter of the bamboo pipe 2.

[0071] The EBTP anchor rods M are arranged in a plum blossom shape on the outer facade 20 of the city wall, with adjacent rows of anchor rods staggered by 1 / 3 to 1 / 2 of the spacing; according to the existing form of the city wall ruins, they can be evenly arranged along the wall surface, or gradually densely arranged as the wall height increases, and no anchor rods are required within the 1 / 4H range at the bottom of the wall. The spacing of EBTP anchor rods should be 8 to 16 times the diameter of the expanded anchor section to ensure that the disturbance and compaction influence of the expanded anchor section on the soil can cover its adjacent anchor rods, increase the soil pressure around the adjacent anchor rods and the bond strength of the tensile section interface, thereby improving the ultimate pull-out bearing capacity of the anchor rods.

[0072] When the EBTP anchor rod M is installed in the city wall, the bearing plate 3 should be located within the rear 2 / 3L0 length of the anchor section 17 in the rammed earth. The bearing plate positions of adjacent anchor rods should be staggered by 1 / 2 to 1 / 5L0 along the axial direction of the anchor rod, and the projection of the bearing plate 3 at a deeper position in the normal direction of the anchor rod must be located within the tension section 19 of its adjacent anchor rod.

[0073] The working principle of the present invention is as follows:

[0074] When the rammed earth wall site encounters external loads such as horizontal earthquakes, the brick-clad wall has a relative displacement relative to the internal rammed earth due to the large difference in material properties between the brick-clad wall and the rammed earth, and there is no reliable connection between the two. Since the strength of the steel bars, cement mortar, and bricks in the anchoring section of the brick-clad wall and the bond strength of the interface are all high, the relative slip of the anchoring interface is much smaller than that of the anchoring section in the rammed earth, so it can be regarded as a whole that deforms together. At this time, the anchor rods in the rammed earth body will bear the axial load caused by the displacement of the brick-clad wall. Since the steel bars in the pressure section are not bonded to the bamboo, the load will be directly transferred from the steel bars to the expanded anchor joint, and the expanded anchor joint will be pulled and displaced toward the hole mouth. The modified mud on the pressure section side of the expanded anchor joint will be under pressure, and the interface between the modified mud and the rammed earth body will be under shear stress, which will be gradually transmitted from the anchor joint to the hole mouth. The force mode of this section is similar to that of the traditional pressure-type anchor rods. Due to the forward movement of the expanded anchor joint, the anchor rods in the tension section at the rear also have a displacement trend toward the hole mouth. However, since the steel bars in the tension section are bonded to the inner surface of the bamboo by epoxy resin glue, its strength is much higher than the bonding strength between the outer surface of the bamboo and the rammed earth interface. Therefore, the shear slip in this section will mainly occur at the interface between the outer surface of the bamboo and the rammed earth, and the interface shear stress will be gradually transmitted from the anchor joint to the bottom. Its force mode is similar to that of the full-length bonded tension-type anchor system.

[0075] In addition, the shear expansion effect caused by the displacement of the expanded anchor section will disturb the soil around the anchor within a certain range, causing the movement and compaction of soil particles, enhancing the soil pressure around the anchors of adjacent anchor rods, and increasing the bonding strength of the anchoring interface of adjacent anchor rods. The anchor rods will work together to resist the relative displacement and deformation of the brick-clad wall, further improving the anchoring effect.

[0076] The present invention is not limited to the above-mentioned embodiments. On the basis of the technical solution disclosed in the present invention, technicians in this field can make some substitutions and deformations to some technical features therein according to the disclosed technical content without creative labor, and these substitutions and deformations are all within the protection scope of the present invention.

Claims

1. An anchoring structure for brick-clad city wall ruins based on EBTP anchor rods, characterized in that: It comprises an EBTP anchor rod and a brick-clad wall; the EBTP anchor rod comprises a steel bar, an anchor plate, a bamboo pipe and an expanded anchor section, the steel bar runs through the bamboo pipe, and the length of the steel bar is greater than the length of the bamboo pipe, the steel bar runs through the bamboo pipe section and extends into the anchor section in the rammed earth of the wall, the steel bar extends out of the bamboo pipe section and extends into the anchor section in the brick-clad wall, the steel bar runs through the outer end surface of the brick-clad wall and is fixed by bolts and anchor plates; the expanded anchor section is arranged in the middle section of the steel bar in the bamboo pipe, and the expanded anchor section is located between the pressure section and the tension section of the brick-clad wall; The anchoring section in the brick wrapping is from the hole on the facade of the brick wrapping wall to the interface between the brick wrapping wall and the rammed earth body. The brick wrapping wall and the rammed earth body are grouted by cement mortar and modified mud anchor respectively. The steel bars of the EBTP anchor rod are bonded to the brick wrapping by cement mortar from the anchor plate to the steel bar section extending from the bamboo pipe. The cement mortar is prepared by mixing cement and medium sand with water in a mass ratio of 15:85, and a water-cement ratio of 0.

29.

2. The brick-clad city wall ruins anchoring structure based on EBTP anchor rods according to claim 1 is characterized in that: The anchoring section in the rammed earth is from the interface between the brick wall and the rammed earth body to the bottom end of the anchor hole, and the outer surface of the bamboo pipe section with steel bars passing through is bonded to the rammed earth body by using modified mud; The modified mud is prepared by mixing scattered soil from the site, cement, fly ash, and glutinous rice paste with 5% silica sol, with the mass ratio of each component being 60:20:10:10 and the water-cement ratio being 0.

31.

3. The brick-clad city wall ruins anchoring structure based on EBTP anchor rod according to claim 1, characterized in that: Epoxy resin glue is poured into the bamboo pipe in the tension section to bond the inserted steel bars; epoxy resin glue is not poured into the bamboo pipe in the pressure section.

4. The brick-clad city wall ruins anchoring structure based on EBTP anchor rod according to claim 1, characterized in that: The expanded anchor section includes a bearing plate and a triangular support body. The bearing plate is vertically welded along the radial direction of the steel bar. The triangular support body is fixedly connected to the bearing plate and the steel bar along the axial direction of the steel bar. A plurality of circular grouting holes are arranged on the bearing plate.

5. The brick-clad city wall ruins anchoring structure based on EBTP anchor rod according to claim 1, characterized in that: A longitudinal sliding groove penetrating through the triangular support body is provided in the middle section of the bamboo pipe.

6. The brick-clad city wall ruins anchoring structure based on EBTP anchor rods according to claim 1, characterized in that: The EBTP anchor rods are evenly arranged along the outer facade of the brick-clad wall, or are gradually densely arranged from bottom to top as the wall height increases.

7. The brick-clad city wall ruins anchoring structure based on EBTP anchor rod according to claim 1, characterized in that: The EBTP anchor rods are arranged in a plum blossom shape along the outer facade of the brick-clad wall, and adjacent rows of EBTP anchor rods are staggered by 1 / 3 to 1 / 2 of the spacing between the anchor rods.

8. The brick-clad city wall ruins anchoring structure based on EBTP anchor rods according to claim 1, characterized in that: The EBTP anchor rod penetrates into the brick-clad wall at an angle of 10 to 30 degrees to the horizontal plane and is inserted obliquely downward.

9. The brick-clad city wall ruins anchoring structure based on EBTP anchor rods according to claim 1, characterized in that: The expanded anchor sections between adjacent EBTP anchor rods are staggeredly arranged at different depths in the rammed earth body, and the axial spacing is 1 / 2 to 1 / 5 of the length of the anchoring section in the rammed earth.

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