Weathering-resistant steel anchorage pier and lattice beam combined supporting and retaining structure of excavation slope and construction method of weather-resistant steel anchorage pier and lattice beam combined supporting and retaining structure

Abstract

The invention relates to the technical field of excavation side slope reinforcement, in particular to an excavation side slope weathering-resistant steel anchorage pier and lattice beam combined retaining structure and a construction method thereof.The construction method comprises the following construction steps that pre-stressed anchor cables and weathering-resistant steel anchorage piers are arranged on the slope surface of a side slope in a layered mode along with side slope layered excavation, and the pre-stressed anchor cables are tensioned and locked immediately for the first time; under the protection of primary tensioning, pre-stressed anchor cable locking and weathering-resistant steel anchorage piers, excavation of the next layer is conducted, and pouring of slope lattice beams is conducted after layered excavation of the first-stage slope is completed; and after the lattice beam concrete between the weather-proof steel anchorage piers is cured, compensating and tensioning again, and locking the pre-stressed anchor cables. According to the method, rapid and safe construction of excavation side slope continuous lattice beam reinforcement can be achieved, the method is suitable for reinforcement treatment of excavation side slopes of various types, various scales and different heights, a large amount of funds can be saved, the construction period can be shortened, and the method is particularly suitable for emergency rescue and disaster relief side slope treatment engineering with the urgent requirement for time.

Description

Technical Field

[0001] The present invention relates to the technical field of cut slope reinforcement, and particularly relates to a combined retaining structure of weathering steel anchor piers and lattice girders for cut slopes and a construction method thereof. Background Art

[0002] The lattice girder slope reinforcement technology is a slope anchoring technology that uses cast-in-place reinforced concrete lattices for slope surface protection and stabilizes the slope body with anchor rods (cables). Grass or small shrubs are planted in the lattice frames of the lattice girders. This technology is widely used in the reinforcement of high-steep slopes in highway, railway, mine, water conservancy, municipal and construction projects, etc. It can achieve positive effects of being both safe and beautiful while protecting the slope.

[0003] The main function of the lattice girders set on the slope surface is to distribute the remaining sliding force or rock and soil pressure of the slope to the cables at the lattice nodes, and then transfer it to the stable stratum of the slope body through the cables, so that the slope body is in a stable state under the action of the strong anchoring force provided by the anchor rods or cables. Therefore, the combined prestressed cable lattice girder can not only meet the overall stability of the slope, but also apply a normal pressure to the slope surface to improve the stability of the local shallow rock and soil mass on the slope surface. Among them, the overall stability of the slope is mainly stabilized by the cables set at the lattice girder nodes, while the local stability of the slope surface is guaranteed by the vegetation, grouted rubble masonry, dry rubble masonry or shotcrete in the frames. The cast-in-place reinforced concrete lattice girder can provide a large anti-sliding resistance, has good integrity and can cooperate well with the prestressed cables in force, so it is widely used in the reinforcement of various types of slopes with different heights in China, especially in the reinforcement and treatment of cutting slopes mainly for excavation.

[0004] At present, the lattice beam slope anchoring technology mainly has the following disadvantages: ① Pouring lattice beam concrete on the slope surface requires a long time of curing, which is not conducive to the early stability of the slope and generally cannot be used in slope emergency projects; ② The construction site on the slope surface of the slope requires a large number of formworks and construction workers, which is not conducive to realizing rapid construction and stabilizing the slope early; ③ The construction site environment of the slope is harsh, and it is easy to have adverse conditions such as formwork sliding, displacement and concrete bleeding on the slope surface, which affect the quality of the support structure; ④ The vibration of the lattice beam concrete on the slope surface disturbs the slope greatly, and may even induce geological disasters such as large-scale landslides during construction; ⑤ There are many construction steps, and it takes a long time from the excavation to the completion of the support of the first-level slope, which is not conducive to the early closure of the slope surface. For this reason, Chinese invention patent CN2020107142795 discloses a precast anchor pier and post-cast lattice beam assembly integral construction method for slope reinforcement. This method excavates the slope in layers, installs reinforced concrete precast anchor piers in time layer by layer and initially tension and lock the prestressed anchor cables to ensure the temporary stability of the slope during construction. After the first-level slope excavation is completed, pour the concrete lattice beam between the precast anchor piers and tension and lock the prestressed anchor cables again to ensure the permanent stability of the excavated slope. However, this method has the following disadvantages: ① The self-weight of the reinforced concrete precast anchor pier is large, which is not conducive to the transportation, hoisting and slope surface installation of the precast components; ② To ensure the temporary stability of the excavated slope during construction, when it is necessary to increase the bottom area of the precast anchor pier, the self-weight of the anchor pier further increases, which is more unfavorable to the construction of the precast components; ③ After the first-level slope excavation is completed, pour the lattice beam between adjacent precast anchor piers, and a cold joint is formed between the post-cast concrete of the lattice beam and the precast concrete of the anchor pier, which is not conducive to the overall effect of the combined retaining structure. Further, Chinese utility model patent 2019208173242 discloses a slope prestressed anchor cable frame support structure, which includes anchor cables, concrete protective layers, steel anchor piers, anchor heads and lattice beams. First, set the anchor cables and install the steel anchor piers, and then pour the lattice beams on the slope surface concrete protective layer to cover the steel anchor piers and anchor heads. However, this method has the following disadvantages: ① Since there is no steel bar, it is difficult for the lattice beam concrete to be effectively connected with the steel anchor pier, and it is difficult for the lattice beam and the steel anchor pier to meet the shear or punching shear bearing capacity near the node; ② When the slope stability is poor and it is necessary to increase the size of the steel anchor pier, the cross-sectional size of the lattice beam covering the steel anchor pier should also increase accordingly, which is not conducive to controlling the economy of the project; ③ The lattice beam is a concrete structure (without steel bars inside), so it is difficult to bear the large slope rock and soil pressure and it is difficult to deal with the reinforcement and treatment of high and steep slopes. Summary of the Invention

[0005] To solve the above problems, the present invention provides a combined retaining structure and construction method of weathering steel anchor piers and lattice beams for excavated slopes.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A combined retaining structure of weathering steel anchor piers and lattice girders for cutting slopes, comprising a prestressed anchor cable system, weathering steel anchor piers and reinforced concrete lattice girders. The prestressed anchor cable system includes prestressed anchor cables, spiral stirrups, anchor fittings and grouting for sealing the anchor heads. The prestressed anchor cables are preferably made of steel strands. The external anchor segments thereof penetrate through the weathering steel anchor piers, are locked on the upper surfaces of the weathering steel anchor piers through the anchor fittings, and grouting for sealing the anchor heads is provided.

[0008] The weathering steel anchor piers include lower bearing plates, stiffening plates welded to the lower bearing plates, upper bearing plates, orthogonal rectangular-section empty slots arranged between multiple stiffening plates, and reserved anchor holes arranged at the central positions of the lower bearing plates and the upper bearing plates.

[0009] The lattice girders are cast-in-place reinforced concrete rectangular-section beams, which are rigidly connected orthogonally on the slope by cross beams and longitudinal beams. The cross-sectional dimensions of the cross beams and the longitudinal beams are controlled by the orthogonal rectangular-section empty slots formed between the stiffening plates, and the cross-sectional dimensions are not less than 300 mm × 350 mm.

[0010] Furthermore, the lower bearing plates are square plates, and a number of trapezoidal stiffening plates arranged orthogonally are welded on the upper surfaces. Orthogonal rectangular-section empty slots are formed between multiple stiffening plates. The upper bearing plates of the weathering steel anchor piers are square plates and are arranged above the stiffening plates and separated from the stiffening plates. Their planar dimensions are slightly smaller than those of the lower bearing plates. Reserved anchor holes are arranged near the middle positions of the lower bearing plates and the upper bearing plates.

[0011] Furthermore, the intersection points of the cross beams and the longitudinal beams are arranged at the positions of the reserved anchor holes in the middle of the weathering steel anchor piers and within the orthogonal rectangular-section empty slots between the stiffening plates below the upper bearing plates and above the lower bearing plates.

[0012] Furthermore, longitudinal stressed steel bars and stirrups are arranged inside the cross beams and the longitudinal beams of the lattice girders. The longitudinal stressed steel bars are symmetrically arranged as 2, 3, 4, etc. respectively near the top and bottom surfaces of the cross beams and the longitudinal beams. Among them, the longitudinal stressed steel bars are made of HRB400 and HRB500 grade steel bars, and the stirrups are made of HPB300 or HRB400 grade steel bars and are tied outside the longitudinal stressed steel bars. During construction, the longitudinal stressed steel bars of the cross beams and the longitudinal beams are respectively passed through the orthogonal rectangular-section empty slots formed by the stiffening plates in the weathering steel anchor piers, and stirrups are tied outside the longitudinal stressed steel bars. After formwork support, concrete is cast in place on the slope to form continuous reinforced concrete cross beams and longitudinal beams and rigidly connect them into lattice girders.

[0013] Furthermore, the lattice girders should be constructed after the initial tensioning and locking of the prestressed anchor cables for the weathering steel anchor piers on the first-level slope. The lattice girders use concrete with a strength grade not lower than C30.

[0014] Furthermore, a foundation beam and a capping beam are respectively arranged at the bottom and top of the longitudinal beam, and the foundation beam and the capping beam are cast-in-place reinforced concrete structures, and the steel bars and concrete grades used are the same as those of the crossbeams and longitudinal beams of the lattice beams.

[0015] The present invention also provides a construction method for the above-mentioned combined retaining structure of weathering steel anchor piers and lattice beams on an excavated slope, comprising the following steps: first, prestressed anchor cables are arranged in layers on the slope surface as the slope is excavated in layers, and the weathering steel anchor piers are installed in time, and the initial tensioning and locking of the prestressed anchor cables are immediately performed, and the slope surface that has been excavated in layers is protected to ensure the temporary stability of the excavated slope during construction; then, under the protection of the initial tensioning and locking of the prestressed anchor cables and the weathering steel anchor piers, the next layer is excavated and the lattice beams are cast on the slope surface after the first layer excavation of the slope is completed; finally, after the lattice beam concrete between the weathering steel anchor piers is cured, the prestressed anchor cables are compensated and locked again to ensure the long-term permanent stability of the excavated slope.

[0016] Furthermore, the construction method of the combined retaining structure of weathering steel anchor pier and lattice beam for excavation slope described in the present invention specifically comprises the following steps:

[0017] S1. Excavate a layered slope rock and soil mass from top to bottom and trim the slope surface

[0018] According to the stability of the slope after excavation and the longitudinal spacing between the weathering steel anchor piers, the excavation height of each layer of rock and soil is controlled at 2-3m. After trimming the layered slope surface, measure and lay out the lines on the layered slope surface and mark the position of the weathering steel anchor piers;

[0019] S2, Slope Grooving

[0020] According to the position of the weathering steel anchor pier marked on the slope, the slope is grooved perpendicular to the slope. The plane size of the slope groove should be slightly larger than the plane size of the weathering steel anchor pier. The groove depth should be such that the lattice beam to be constructed later can be embedded in the slope by no less than 200mm.

[0021] S3. Prestressed anchor cable construction

[0022] According to the predetermined incident angle of the prestressed anchor cable, the weathering steel anchor pier is provided with a reserved anchor hole in the groove of the layered slope surface, and a hole is dry-drilled into the slope body by a drilling rig. After the hole is cleaned, the prestressed anchor cable is installed and grouting is performed for curing to strengthen the anchor cable;

[0023] S4. Install weathering steel anchor piers and initially tension and lock prestressed anchor cables

[0024] Pass the external anchor section of the prestressed anchor cable through the reserved anchor hole of the lower backing plate, insert the spiral reinforcement and set the spiral reinforcement at the center of the orthogonal rectangular cross-section empty groove of the weather-resistant steel anchor pier. Press the upper backing plate on the stiffening plate of the weather-resistant steel anchor pier, place the weather-resistant steel anchor pier into the groove on the slope surface, use a through-hole jack to apply prestress to the prestressed anchor cable in stages for the first time, and lock the external anchor section of the prestressed anchor cable on the surface of the upper backing plate with an anchor; the initial tension and locking value of the prestressed anchor cable should preferably be taken as 0.2 - 0.4 times the standard value of the axial force of the prestressed anchor cable, and it is advisable that the slope rock and soil body under the weather-resistant steel anchor pier does not undergo lateral extrusion and the weather-resistant steel anchor pier does not undergo excessive deformation or buckling failure;

[0025] S5. Execute steps S1 to S4 in a loop

[0026] Excavate downward in layers, set prestressed anchor cables in layers, install weather-resistant steel anchor piers in layers, and initially tension and lock the prestressed anchor cables in layers to reinforce each layer of the slope surface until the excavation and initial reinforcement of each layer of the first-level slope are completed; at this time, the slope surface of this level of cut slope is covered with a group of weather-resistant steel anchor piers arranged on the slope surface after being initially tensioned and locked with prestressed anchor cables. The height of the first-level slope should preferably be controlled within 6 - 10 m, excavated in 3 - 5 layers, and the excavation height of each layer should be controlled within 2 - 3 m;

[0027] S6. Construction of the cast-in-place continuous lattice beam

[0028] S6.1. Construction preparation: Groove the slope surface perpendicular to the groove corresponding to the orthogonal rectangular cross-section empty groove position between the weather-resistant steel anchor piers. The width of the groove should preferably be slightly larger than the width of the lattice beam, and the depth of the groove should be slightly shallower than the depth of the groove of the weather-resistant steel anchor pier;

[0029] S6.2. Steel bar work: Pass the longitudinal stressed steel bars of the cross beam and the longitudinal beam through the orthogonal rectangular cross-section empty groove between the lower backing plate and the upper backing plate of the weather-resistant steel anchor pier respectively, and tie stirrups outside the longitudinal stressed steel bars;

[0030] S6.3. Formwork and concrete work

[0031] Set formwork for the steel bar cages of the cross beam and the longitudinal beam and pour concrete to form a continuous lattice beam, and cure the lattice beam concrete until it is strong;

[0032] S7. Second-stage compensation tensioning and locking of the prestressed anchor cables at the intersection points of the combined retaining structures on the slope surface of the first-level slope

[0033] Adopt a through-hole jack to perform second-stage graded compensation tensioning and locking of the prestressed anchor cables one by one in the order from the bottom of the slope to the top of the slope to ensure the long-term and permanent stability of the cut slope during its service period. The prestress locking value of the anchor cable after the second-stage tensioning is 0.75 - 1.0 times the standard value of the axial force of the anchor cable;

[0034] S8. Other auxiliary operations

[0035] S8.1. Provide cast-in-place reinforced concrete foundation beams and coping beams at the bottom and top of the longitudinal beams of the combined retaining structure respectively;

[0036] S8.2. Cut off the redundant part of the external anchor section of the prestressed anchor cable and set anchor sealing on the surface of the upper backing plate of the weather-resistant steel anchor pier;

[0037] S8.3. Set drainage ditches and intercepting ditches at the toe and top of the first-level slope respectively, and restore the slope vegetation as needed, and plant grass or small shrubs in the lattice beams;

[0038] S9. Repeatedly cycle the above steps S1 - S8 to complete the reinforcement treatment of other graded or other segmented slopes of the entire cut slope.

[0039] Compared with the prior art, the present invention has the following beneficial effects: ① As a steel structure of a new material, the weathering steel anchor pier has a compact and simple appearance, and can be mass-produced in a factory or shed, with high efficiency, guaranteed quality, and at the same time can achieve energy conservation and emission reduction, reducing environmental pollution; ② The weathering steel anchor pier has a simple appearance, which is convenient for mass production, handling, stacking and hoisting of precast components, and the weathering steel anchor pier has strong corrosion resistance; ③ The installation process at the slope construction site is simple and easy to operate. After the weathering steel anchor piers are installed in layers, the prestressed anchor cables can be initially tensioned and locked immediately, which is beneficial to the temporary stability of the excavated slope during construction; ④ The self-weight of the weathering steel anchor pier is small, and the use of small lifting equipment can reduce the labor force, facilitate cross-operation, speed up the installation progress, and the construction process is less affected by the weather; ⑤ After the first-level slope is excavated and temporarily reinforced in layers, concrete is poured in the empty slots of the weathering steel anchor piers and between adjacent weathering steel anchor piers to form a continuous lattice beam. Therefore, the lattice beam has good integrity and reliable force, and is suitable for the reinforcement and treatment of various types, scales and different heights of excavated slopes in combination with prestressed anchor cables, with strong applicability, especially suitable for emergency rescue slope treatment projects with urgent time requirements; ⑥ The construction of the continuous lattice beam is carried out under the condition that the excavated slope is basically stable after the initial tensioning and locking of the prestressed anchor cables, and the construction safety of the lattice beam can be guaranteed; ⑦ After the prestressed anchor cables are re-compensated and tensioned and locked, the combined retaining structure composed of the weathering steel anchor piers and the continuous lattice beam on the slope works together to further improve the overall stability of the slope; ⑧ After the lattice beam is cast-in-place on the slope, the spacing of the lattice beam can be easily adjusted temporarily according to factors such as the slope shape and slope stability to adapt to the irregular positioning of the weathering steel anchor piers with different spacings; ⑨ When the slope is high and steep and has poor stability, the spacing between the weathering steel anchor piers is reduced so that the entire slope is completely enclosed by the weathering steel anchor piers to avoid local instability of the slope during construction. After the slope construction is completed, the slope completely enclosed by the weathering steel anchor piers can also avoid the erosion of the slope by rainfall; ⑩ When the weathering steel anchor piers are arranged on the non-closed slope surface, planting grass or small shrubs in the frames of the combined retaining structure after completion can avoid the erosion of the slope surface by running water, which is beneficial to coordinating with the surrounding environment and beneficial to environmental protection.

[0040] Therefore, the present invention is applicable to the reinforcement and treatment of various types, scales and different heights of excavated slopes, can save a large amount of funds and shorten the construction period, and is especially suitable for emergency rescue slope treatment projects with urgent time requirements. It is a combined retaining structure and construction method for excavated slopes worthy of popularization and application. Description of the Drawings

[0041] Figure 1 It is a structural schematic diagram of the weathering steel anchor pier in the embodiment of the present invention;

[0042] Figure 2Profile view of the installation of weathering steel anchor piers for the initial tensioning and locking of prestressed anchor cables on the slope surface after the first-stage layered excavation in the embodiment of the present invention;

[0043] Figure 3 Front elevation view of the weathering steel anchor piers on the slope surface after the first-stage slope layered excavation and initial reinforcement in the embodiment of the present invention;

[0044] Figure 4 Front elevation view of the construction of continuous lattice beams on the first-stage slope in the embodiment of the present invention;

[0045] Figure 5 Front elevation view after the reinforcement of the first-stage slope is completed in the embodiment of the present invention;

[0046] Figure 6 Profile view after the reinforcement of the first-stage slope is completed in the embodiment of the present invention;

[0047] In the figure: 1. Prestressed anchor cable system; 101. Prestressed anchor cable, 102. Spiral reinforcement, 103. Anchor fitting, 104. Anchor sealing;

[0048] 2. Weathering steel anchor pier; 201. Lower backing plate, 202. Stiffening plate, 203. Upper backing plate, 204. Reserved anchor hole;

[0049] 3. Lattice beam, 301. Longitudinal stress-bearing steel bar, 302. Stirrup, 303. Foundation beam, 304. Coping beam;

[0050] 4. Drainage ditch;

[0051] 5. Catch ditch. Specific implementation manners

[0052] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that those of ordinary skill in the art can make several deformations and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0053] Embodiment 1: A combined retaining structure of weathering steel anchor piers and lattice beams for a cut slope.

[0054] The combined retaining structure of weathering steel anchor piers and lattice beams for a cut slope of the present invention mainly includes a prestressed anchor cable system 1, a weathering steel anchor pier 2, and a reinforced concrete lattice beam 3.

[0055] Such as Figure 2As shown, the prestressed anchor cable system 1 includes prestressed anchor cables 101, spiral reinforcement 102, anchor fittings 103 and anchor sealing 104. The prestressed anchor cables 101 are preferably made of steel strands. The external anchor section thereof penetrates through the weather-resistant steel anchor pier 2 and is locked by the anchor fittings 103. The external anchor section is provided with the anchor sealing 104, so as to prevent the external anchor section of the prestressed anchor cable 101 and the anchor fittings 103 from rusting.

[0056] As Figure 1 shown, the weather-resistant steel anchor pier 2 includes a lower backing plate 201, stiffening plates 202, an upper backing plate 203 and a reserved anchor hole 204. The lower backing plate 201 is preferably a square plate. A plurality of trapezoidal stiffening plates 202 arranged orthogonally are welded on the lower backing plate 201. An orthogonal rectangular cross-section empty groove is formed between the plurality of stiffening plates 202. A reserved anchor hole 204 is arranged near the middle of the lower backing plate 201. The diameter of the reserved anchor hole 204 should be such that the external anchor section of the prestressed anchor cable 101 can pass through smoothly when the weather-resistant steel anchor pier 2 is installed on the slope. The upper backing plate 203 of the weather-resistant steel anchor pier 2 is preferably a square plate and is arranged above the stiffening plates 202 and separated from the stiffening plates 202. Its planar dimension is slightly smaller than that of the lower backing plate 201. A reserved anchor hole 204 is also correspondingly arranged at the middle position of the upper backing plate 203 for the external anchor section of the prestressed anchor cable 101 to pass through.

[0057] In order to better prevent the cut slope from loosening and collapsing, the present invention preferably adopts large-sized weather-resistant steel anchor piers, which can protect a larger range of slopes. For standardized production, the main geometric dimensions of the weather-resistant steel anchor piers are recommended as shown in the following table.

[0058] Table 1 Main Geometric Dimensions of Weather-Resistant Steel Anchor Piers

[0059]

[0060]

[0061] The lattice beam 3 is a cast-in-place reinforced concrete rectangular cross-section beam, which is composed of cross beams and longitudinal beams rigidly connected orthogonally on the slope. Its cross-sectional dimension is controlled by the orthogonal rectangular cross-section empty groove formed between the stiffening plates 202, and its cross-sectional dimension should not be less than 300mm×350mm. And the intersection of the cross beam and the longitudinal beam is arranged at the position of the reserved anchor hole 204 in the middle of the weather-resistant steel anchor pier 2 and in the orthogonal rectangular cross-section empty groove between the stiffening plates 202 below the upper backing plate 203 and above the lower backing plate 201.

[0062] Longitudinal stress-bearing steel bars 301 and stirrups 302 are arranged inside the cross beams and longitudinal beams of the lattice beam 3. The longitudinal stress-bearing steel bars 301 are symmetrically arranged in 2, 3, 4, etc. near the top and bottom surfaces of the cross beams and longitudinal beams respectively. Among them, the longitudinal stress-bearing steel bars 301 are preferably made of HRB400 and HRB500 grade steel bars, and the stirrups 302 are preferably made of HPB300 or HRB400 grade steel bars and are tied outside the longitudinal stress-bearing steel bars 301.

[0063] The lattice beam 3 should be constructed after the initial tensioning and locking of the prestressed anchor cables 101 on the weathering steel anchor piers 2 on the first-level slope. During construction, the longitudinal stress-bearing steel bars 301 of the cross beams and longitudinal beams of the lattice beam 3 are respectively passed through the orthogonal rectangular cross-section empty grooves formed by the stiffening plates 202 in the weathering steel anchor piers 2, and stirrups 302 are tied outside the longitudinal stress-bearing steel bars 301. After formwork support, concrete is cast in place on the slope to form continuous reinforced concrete cross beams and longitudinal beams and rigidly connect them into the lattice beam 3. The lattice beam is preferably made of concrete with a strength grade not lower than C30, and high-strength concrete is preferably used preferentially if conditions permit.

[0064] After the concrete curing of the lattice beam 3 is completed, the prestressed anchor cables 101 passing through the intersection points of the lattice beam 3 are compensated and tensioned again and locked. The prestress increment of the compensated and tensioned anchor cables is jointly borne by the weathering steel anchor piers and the lattice beams between them to ensure the long-term and permanent stability of the cut slope during the service period.

[0065] Foundation beams 303 and coping beams 304 need to be respectively arranged at the bottom and top positions of the longitudinal beams of the lattice beam 3. The foundation beams 303 and coping beams 304 adopt cast-in-place reinforced concrete structures, and the steel bars and concrete grades used are preferably the same as those of the cross beams and longitudinal beams of the lattice beam 3.

[0066] Example 2: Construction method of a combined retaining structure of weathering steel anchor piers and lattice beams for a cut slope

[0067] Before on-site construction, the entire slope should first be pre-divided into several levels and several segments according to the requirements of the cut slope height, retaining structure, setting of expansion joints, settlement joints, etc., and then excavation and support are carried out for each level and each segment respectively. In this example, only the construction process of the combined retaining structure within one segment of one graded slope is introduced, and repeating this construction process can complete the construction process of the combined retaining structure within other levels and other segments of the entire slope.

[0068] This method is applicable to the reinforcement and treatment of high-steep fractured rock masses or loose soil cut slopes. During the construction of a section of a first-level slope, first, as the slope is excavated in layers, prestressed anchor cables are timely installed in layers on the slope surface. After installing weather-resistant steel anchor piers, initial tensioning, locking of the prestressed anchor cables, and protection of the slope surface that has been excavated in layers are immediately carried out to ensure the temporary stability of the cut slope during construction. Then, under the protection of the initial tensioning, locking of the prestressed anchor cables and weather-resistant steel anchor piers, the excavation of the next layer and the casting of lattice girders on the slope surface after the completion of the layered excavation of the first-level slope are carried out. Finally, after the concrete of the lattice girders between the weather-resistant steel anchor piers has been cured, the prestressed anchor cables are compensated for tensioning and locked again, so that the combined retaining structure of the weather-resistant steel anchor piers and lattice girders works together to ensure the long-term and permanent stability of the cut slope during its service period. The specific construction steps of this method are as follows:

[0069] S1. Excavate the slope rock and soil mass of a layer from top to bottom and trim the slope surface

[0070] According to the stability of the slope after excavation and the longitudinal spacing of the weather-resistant steel anchor piers, the excavation height of each layer of rock and soil mass is controlled at 2 - 3m. After trimming the slope surface of this layer, measure and set out the lines on the slope surface of this layer and mark the positions of the weather-resistant steel anchor piers 2 on the slope surface of this layer.

[0071] S2. Grooving the slope surface

[0072] Groove the slope surface perpendicular to the slope surface of this layer according to the positions of the weather-resistant steel anchor piers 2 marked on the slope surface so as to install the weather-resistant steel anchor piers 2 on the slope surface of this layer. The planar dimension of the slope grooving should be slightly larger than the planar dimension of the weather-resistant steel anchor piers 2, and the grooving depth should ensure that the lattice girders constructed later are embedded in the slope surface by no less than 200mm.

[0073] S3. Construction of prestressed anchor cables

[0074] Drill holes into the slope body with a drill rig dryly according to the predetermined incident angle of the prestressed anchor cable 101 at the reserved anchor holes 204 of the lower bearing plate 201 and the upper bearing plate 203. After clearing the holes with a high-pressure air gun, install the prestressed anchor cable 101 and grout it for curing and waiting for strength. During the curing and waiting for strength of the mortar, it is prohibited to touch the external anchor section of the prestressed anchor cable 101 randomly.

[0075] S4. Install weather-resistant steel anchor piers and carry out initial tensioning and locking of prestressed anchor cables

[0076] Use a hoisting device to lift the weathering steel anchor pier 2, pass the external anchor section of the prestressed anchor cable 101 through the reserved anchor hole 204 of the lower backing plate 201, insert the spiral reinforcement 102 and set the spiral reinforcement 102 at the center of the orthogonal rectangular cross-section empty groove of the weathering steel anchor pier 2. Press the upper backing plate 203 on the stiffening plate 202 of the weathering steel anchor pier 2, and place the weathering steel anchor pier 2 in the groove of the weathering steel anchor pier 2 on this layer of slope. Use a hole-through jack to initially apply prestress to the prestressed anchor cable 101 in stages and lock the external anchor section of the prestressed anchor cable 101 on the surface of the upper backing plate 203. The initial tension locking value of the prestressed anchor cable 101 should preferably be 0.2 - 0.4 times the standard value of the axial force of the prestressed anchor cable, and it is advisable that the slope rock and soil mass below the weathering steel anchor pier 2 does not undergo lateral extrusion and the weathering steel anchor pier 2 does not undergo excessive deformation or buckling failure. See Figure 2 。

[0077] S5. Repeatedly execute steps S1 to S4

[0078] Excavate downwards in layers, set prestressed anchor cables in layers, install weathering steel anchor piers 2 in layers, and initially tension and lock the prestressed anchor cables 101 in layers to reinforce each layer of slope surface until the excavation and preliminary reinforcement of the first-level slope in layers are completed. At this time, the slope surface of this level of cut slope is covered with a group of weathering steel anchor piers arranged on the slope surface after preliminary tension and locking of the prestressed anchor cables. The height of the first-level slope should preferably be controlled within 6 - 10 m, excavated in 3 - 5 layers, and the height of each layer of excavation should be controlled within 2 - 3 m. See Figure 3 。

[0079] S6. Construction of the cast-in-place continuous lattice beam

[0080] S6.1. Construction preparation: Grooves are cut perpendicular to the slope surface at the positions corresponding to the orthogonal rectangular cross-section empty grooves between the weathering steel anchor piers 2. The width of the grooves should preferably be slightly larger than the width of the lattice beam, and the depth of the grooves should be slightly shallower than the depth of the grooves of the weathering steel anchor pier 3 to prepare for setting cross beams and longitudinal beams between the weathering steel anchor piers.

[0081] S6.2. Steel bar work: Pass continuous longitudinal stress bars 301 for the cross beams and longitudinal beams of the lattice beam 3 through the orthogonal rectangular cross-section empty groove between the lower backing plate 201 and the upper backing plate 203 of the weathering steel anchor pier 2, and tie stirrups 302 outside the longitudinal stress bars 301.

[0082] S6.3. Formwork and concrete work: Set formwork for the reinforcement cages of the cross beams and longitudinal beams of the lattice beam 3 between the weathering steel anchor piers 2 and pour concrete to form a continuous lattice beam 3, and cure the concrete until it becomes strong. It should be noted that for the concrete in the orthogonal rectangular cross-section empty groove of the weathering steel anchor pier 2, especially at the intersections of the cross beams and longitudinal beams of the lattice beam 2, the vibration should be strengthened to make the concrete densely fill the orthogonal rectangular cross-section empty groove of the weathering steel anchor pier 2. See Figure 4 。

[0083] S7. Secondary compensation tensioning and locking of the prestressed anchor cables at the intersection points of the combined retaining structures on the first-level slope surface

[0084] Adopt a through-hole jack to perform secondary step-by-step compensation tensioning and locking of the prestressed anchor cables 101 one by one in the order from the bottom to the top of the slope to ensure the long-term and permanent stability of the excavated slope during its service period. After secondary tensioning, the prestressed locking value of the anchor cable should be 0.75 - 1.0 times the standard value of the axial force of the anchor cable.

[0085] S8. Other auxiliary operations

[0086] S8.1. Cast-in-place reinforced concrete foundations 303 and capping beams 304 are respectively set at the bottom and top of the longitudinal beams of the combined retaining structure.

[0087] S8.2. Cut off the redundant part of the external anchor section of the prestressed anchor cable 101 and set a sealing anchor 104 on the surface of the upper bearing plate 203 of the weathering steel anchor pier 2.

[0088] S8.3. Drainage ditches 4 and intercepting ditches 5 are respectively set at the toe and top of the first-level slope, and the slope vegetation is restored as needed. Grass is planted or small shrubs are planted within the lattice beam grid. See Figure 5 and Figure 6 .

[0089] Repeatedly cycle through the above steps S1 - S8 to complete the reinforcement treatment of other graded or other segmented slope surfaces of the entire excavated slope. It should be noted that during the layered excavation of the first-level slope, if the slope gradient is large and the slope surface stability is poor, the flowing water construction process can be adopted for one layer of the slope surface. That is, within one layer, the prestressed anchor cables are set in a timely manner following the excavation, the weathering steel anchor piers are installed in a timely manner, and the prestressed anchor cables are initially tensioned and locked in a timely manner to ensure the continuity of construction during the construction process of one layer and the temporary stability of the excavated slope surface.

[0090] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various deformations or modifications within the scope of the claims, which does not affect the essence of the present invention.

Claims

1. A combined retaining structure of weathering steel anchor piers and lattice girders for cutting slopes, characterized in that: It includes a prestressed anchor cable system, a weathering steel anchor pier, and a reinforced concrete lattice beam. The prestressed anchor cable system includes prestressed anchor cables, spiral stirrups, anchor fittings, and anchor sealing. The external anchor section of the prestressed anchor cable penetrates through the weathering steel anchor pier, is locked on the upper surface of the weathering steel anchor pier through the anchor fittings, and anchor sealing is set. The weathering steel anchor pier includes a lower backing plate, stiffening plates welded to the lower backing plate, an upper backing plate, orthogonal rectangular-section empty grooves formed between multiple stiffening plates, and reserved anchor holes set on the lower backing plate and the upper backing plate. The lattice beam is a cast-in-place reinforced concrete rectangular-section beam, which is composed of cross beams and longitudinal beams rigidly connected orthogonally on the slope surface. The cross-sectional dimensions of the cross beams and longitudinal beams are controlled by the orthogonal rectangular-section empty grooves formed between the stiffening plates, and the cross-sectional dimensions should not be less than 300mm×350mm.

2. The weathering steel anchor pier and lattice beam combined retaining structure for cutting slope according to claim 1, characterized in that: The lower backing plate adopts a square plate, and several trapezoidal stiffening plates arranged orthogonally are welded on the upper surface. Orthogonal rectangular-section empty grooves are formed between multiple stiffening plates. The upper backing plate of the weathering steel anchor pier adopts a square plate and is set above the stiffening plates and separated from the stiffening plates. Its plane dimension is smaller than that of the lower backing plate. Reserved anchor holes are set near the middle positions of the lower backing plate and the upper backing plate.

3. The weathering steel anchor pier and lattice beam combined retaining structure for cutting slope according to claim 1, characterized in that: The intersection of the cross beam and the longitudinal beam is set at the position of the reserved anchor hole in the middle of the weathering steel anchor pier and within the orthogonal rectangular-section empty groove between the stiffening plates below the upper backing plate and above the lower backing plate.

4. The weathering steel anchor pier and lattice beam combined retaining structure for cutting slope according to claim 1, wherein: Longitudinal stressed steel bars and stirrups are arranged inside the cross beams and longitudinal beams of the lattice beam. The longitudinal stressed steel bars are symmetrically arranged as 2, 3, or 4 respectively near the top and bottom surfaces of the cross beams and longitudinal beams. Among them, the longitudinal stressed steel bars adopt HRB400 and HRB500 grade steel bars, and the stirrups adopt HPB300 or HRB400 grade steel bars and are tied outside the longitudinal stressed steel bars. During construction, the longitudinal stressed steel bars of the cross beams and longitudinal beams are respectively passed through the orthogonal rectangular-section empty grooves formed by the stiffening plates in the weathering steel anchor pier, and stirrups are tied outside the longitudinal stressed steel bars. After formwork support, concrete is cast in place on the slope surface to form continuous reinforced concrete cross beams and longitudinal beams and rigidly connect them into a lattice beam.

5. The weathering steel anchor pier and lattice beam combined retaining structure for excavated side slope as claimed in claim 1, wherein: The lattice beam is constructed after the initial tensioning and locking of the prestressed anchor cables on the weathering steel anchor piers on the first-level slope surface. The lattice beam is cast on the slope surface with concrete of strength grade not lower than C30.

6. The weathering steel anchor pier and lattice beam combined retaining structure for cutting slope according to claim 1, wherein: Foundation beams and coping beams are respectively arranged at the bottom and top positions of the longitudinal beam. Both the foundation beams and coping beams adopt cast-in-place reinforced concrete structures, and the grades of the steel bars and concrete used are the same as those of the cross beams and longitudinal beams of the lattice beam.

7. The construction method of the combined retaining structure of weathering steel anchor piers and lattice girders for cutting slopes according to any one of claims 1-6, characterized in that: It includes the following steps: First, as the slope is excavated in layers, prestressed anchor cables are set on the slope surface of the slope in layers, the weathering steel anchor piers are installed in time, and the prestressed anchor cables are immediately subjected to initial tensioning and locking to protect the excavated slope surface, so as to ensure the temporary stability of the excavated slope during construction. Then, under the protection of the initial tensioning and locking of the prestressed anchor cables and the weathering steel anchor piers, the next layer of excavation is carried out and the lattice beam is poured on the slope surface after the first-level slope is excavated in layers. Finally, after the concrete of the lattice beam between the weathering steel anchor piers is cured, the prestressed anchor cables are compensated for tensioning and locked again.

8. The construction method of the combined retaining structure of weathering steel anchor piers and lattice girders for cutting slopes according to claim 7, characterized in that: Specifically, it includes the following steps: S1. Excavate a layered slope rock and soil body from top to bottom and trim the slope surface According to the stability of the slope after excavation and the longitudinal spacing between weathering steel anchor piers, the excavation height of each layer of rock and soil is controlled at 2 - 3m. After trimming the slope surface of this layer, measure and set out the positions of the weathering steel anchor piers on the slope surface of this layer; S2. Grooving the slope surface Groove the slope surface perpendicular to the slope surface of this layer according to the positions of the weathering steel anchor piers marked on the slope surface. The planar dimension of the slope surface groove should be slightly larger than the planar dimension of the weathering steel anchor pier, and the grooving depth should ensure that the later constructed lattice beam is embedded in the slope surface by no less than 200mm; S3. Construction of prestressed anchor cables Drill dry into the slope body with a drill at the reserved anchor hole position of the weathering steel anchor pier in the groove of the slope surface of this layer according to the predetermined incident angle of the prestressed anchor cable. After clearing the hole, install the prestressed anchor cable and grout it for curing until it gains strength; S4. Install the weathering steel anchor pier and initially tension and lock the prestressed anchor cable Pass the external anchor section of the prestressed anchor cable through the reserved anchor hole of the lower bearing plate of the weathering steel anchor pier, insert the spiral reinforcement and set the spiral reinforcement at the center of the rectangular cross-section empty groove of the weathering steel anchor pier. Press the upper bearing plate on the stiffening plate of the weathering steel anchor pier, and place the weathering steel anchor pier into the groove of the slope surface. Use a through-hole jack to clamp the external anchor section of the prestressed anchor cable to initially apply prestress to the prestressed anchor cable in stages and lock the external anchor section of the prestressed anchor cable on the outer surface of the upper bearing plate with an anchor; The initial tension and locking value of the prestressed anchor cable is taken as 0.2 - 0.4 times the standard value of the axial force of the prestressed anchor cable, and ensure that the slope rock and soil body under the weathering steel anchor pier does not undergo lateral extrusion and the weathering steel anchor pier does not undergo excessive deformation or buckling failure; S5. Repeat steps S1 to S4 in a cycle Excavate downwards in layers, set prestressed anchor cables in layers, install weathering steel anchor piers in layers, and initially tension and lock the prestressed anchor cables in layers to reinforce each layer of slope surface until the excavation and initial reinforcement of each layer of the first-level slope are completed; At this time, the slope surface of this level of excavated slope is covered with a group of weathering steel anchor piers arranged on the slope surface after the prestressed anchor cables are initially tensioned and locked; S6. Construction of cast-in-place continuous lattice beam S6.

1. Construction preparation: Groove the slope surface perpendicular to the groove of the slope surface corresponding to the rectangular cross-section empty groove position between the weathering steel anchor piers. The groove width should be slightly larger than the width of the lattice beam, and the grooving depth should be slightly shallower than the grooving depth of the weathering steel anchor pier; S6.

2. Steel bar work: Pass the longitudinal stressed steel bars of the cross beam and longitudinal beam through the orthogonal rectangular cross-section empty groove formed by the stiffening plates between the lower bearing plate and the upper bearing plate of the weathering steel anchor pier respectively, and bind stirrups to the longitudinal stressed steel bars of the cross beam and longitudinal beam; S6.

3. Formwork and concrete work Set formwork for the steel bar cages of the cross beam and longitudinal beam and pour concrete to form a continuous lattice beam, and cure the concrete until it gains strength; S7. Secondary compensatory tension and lock the prestressed anchor cables at the intersection points of the combined retaining structure on the slope surface of the first-level slope Adopt a through-hole jack to perform secondary staged compensatory tension and lock the prestressed anchor cables one by one in the order from the bottom of the slope to the top of the slope to ensure the long-term and permanent stability of the excavated slope during its service period. After the secondary tension, the prestress locking value of the anchor cable is 0.75 - 1.0 times the standard value of the axial force of the anchor cable; S8. Other auxiliary operations S8.

1. Set cast-in-place reinforced concrete foundation beams and coping beams at the bottom and top of the longitudinal beam of the combined retaining structure respectively; S8.2 Cut the redundant part of the external anchor section of the prestressed anchor cable and set the anchor sealing on the surface of the upper backing plate of the weathering steel anchor pier; S8.3 Set drainage ditches and intercepting ditches at the toe and top of the first-level slope respectively, and restore the slope vegetation as needed, plant grass or small shrubs in the grid beams; S9 Repeatedly cycle the above steps S1-S8 to complete the excavation and reinforcement treatment of other graded or other segmented slopes of the entire cut slope.

9. The construction method of the combined retaining structure of weathering steel anchor piers and lattice girders for cutting slopes as claimed in claim 7, characterized in that: The height of the first-level slope should be controlled at 6-10m, excavated in 3-5 layers, and the height of each excavation layer should be controlled at 2-3m.

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