Suspended anchor cable lattice beam expansive soil slope retaining structure and construction method

Abstract

The invention relates to the technical field of expansive soil side slope supporting and retaining, in particular to a suspended anchor cable lattice beam expansive soil side slope supporting and retaining structure and a construction method.The side slope supporting and retaining structure comprises anchorage piers, suspended lattice cross beams, suspended lattice longitudinal beams, pre-stressed anchor cables, a supporting and retaining structure foundation and a supporting and retaining structure top beam; the anchorage piers, the lattice cross beams and the lattice longitudinal beams are integrally formed on the slope surface of the expansive soil side slope in a cast-in-place mode through reinforced concrete at a time, the anchorage piers are arranged in notch grooves of the slope surface and make direct contact with the expansive soil side slope, and the lattice cross beams and the lattice longitudinal beams are rigidly connected to the side faces of the anchorage piers and are away from the slope surface of the expansive soil side slope by a certain suspension height. The supporting and retaining structure foundation and the supporting and retaining structure top beam are formed at the two ends of the lattice longitudinal beam through cast-in-place reinforced concrete in a later-stage multi-time pouring and tamping mode and arranged at the slope toe and the slope top of the expansive soil slope respectively. The method can be suitable for reinforcement treatment of excavation side slopes or natural side slope projects with different scales and different heights in expansive soil areas.

Description

Technical Field

[0001] The invention relates to the technical field of expansive soil slope retaining, and in particular to an expansive soil slope retaining structure of a suspended anchor cable lattice beam and a construction method. Background Art

[0002] Expansive soil is a kind of high-plastic clay rich in hydrophilic clay minerals such as kaolinite, illite and montmorillonite. It is also a kind of highly plastic clay that will undergo significant expansion and contraction deformation with the increase or decrease of water content. It has the following main engineering properties: (1) Swelling and shrinkage: After absorbing water, the volume of expansive soil expands, which will cause the buildings or structures on its surface to bulge. After losing water, the volume of expansive soil shrinks, which can easily cause the soil to crack and cause the buildings or structures on its surface to sink. At the same time, the swelling and shrinkage of expansive soil is different from that of other clays. Repeated shrinkage and swelling will lead to a decrease in the effective cohesion of the soil, resulting in a decrease in the strength of the soil. (2) Cracks: The cracks in expansive soil can be mainly divided into three types: vertical cracks, horizontal cracks and oblique cracks. These cracks divide the soil into blocks with certain geometric shapes, destroying the integrity of the soil. The failure of expansive soil slopes is mostly related to the cracks contained in the soil, and the formation of the slope sliding surface is mainly controlled by the weak structural surface of the cracks. The generation of cracks is caused by the expansion and contraction characteristics of expansive soil. Repeated water absorption and expansion, water loss and shrinkage, and repeated cyclic changes lead to loose soil structure, and the loose soil structure in turn intensifies rainwater infiltration, creating conditions for expansion and contraction. (3) Weathering characteristics: Expansive soil is affected by climatic factors and is very susceptible to weathering damage. After the slope is excavated, the soil will quickly break, peel off, and soften under the action of weathering, which will destroy the soil structure and further reduce its strength. It can be seen that the stability of slopes in expansive soil areas is extremely complex.

[0003] There are two basic principles for the treatment of expansive soil slopes: limiting the development of soil cracks and not limiting the development of soil cracks. Among them, the specific measures to limit the development of soil cracks include replacement, soil improvement and geomembrane reinforcement; while the specific measures to not limit the development of soil cracks include geobags, retaining structures and slope protection. Among the above specific measures, the use of slope retaining structures is suitable for reinforcing high, steep and unstable expansive soil slopes with native weak structural surfaces or potential sliding surfaces and has a good reinforcement effect. Therefore, it is widely used in the treatment of expansive soil slopes. Common slope retaining structures include retaining walls, anti-slide piles, soil nail walls and anchor (cable) lattice beams.

[0004] Due to its ability to actively load and control slope deformation, anchor (cable) lattice beam slope retaining structures are increasingly being used in the reinforcement and management of various types of natural slopes and artificial slopes of different heights in expansive soil areas. For example, Chinese patent document 111945752A discloses a frame-anchor support structure suitable for adaptive deformation control of expansive soil slopes, including a waterproof geomembrane, a drainage ditch, a frame beam, an anchor rod and an adaptive deformation control module, which adapts to and controls any form of deformation of the expansive soil slope by combining the air cavity of high-pressure inert gas with the existing frame beam support structure; Chinese patent document 113026773A discloses a frame beam support system for expansive soil slopes and a construction method thereof, which uses high-strength elastic rubber sheets to produce vertical elastic parts and horizontal elastic parts in the factory and sets a "cross"-shaped elastic part as a whole at each intersection node of the anchor frame beam, relying on the elasticity of the elastic part to suppress the expansion characteristics of the expansive soil; Chinese patent document 114703871A discloses a rigid-flexible combined support structure and construction method for an expansive soil excavation slope, which sets a hook spring expansion bolt on the side of the slope frame beam and sets a hook spring expansion bolt on the frame beam. Spring anchor rods are inserted into the inner slope surface to adapt to the expansion and contraction deformation of the slope surface of the expansive soil slope; Chinese patent document 116290031A discloses an ecologically resilient lattice anchoring structure and construction method for protecting expansive soil slopes, including vegetation protection mats, lattice beams, anchor rods, U-shaped nails, intercepting / drainage ditches and slope protection vegetation. The composite whole composed of vegetation protection mats and vegetation can effectively adjust water migration, limit the cracking of the surface soil, limit the development of cracks to the deep, and prevent the atmospheric influence depth from developing to the deep soil; Chinese patent 116335167A discloses an expansive soil slope adaptive drainage and swelling reduction comprehensive treatment system and its construction method, including lattice beams, contact-type anchor rods, adaptive drainage devices, fluid swelling reduction devices and interval energy controllers, and vegetation is arranged in the lattice frame, providing an expansive soil slope adaptive drainage and swelling reduction comprehensive treatment system that takes into account reinforcement, drainage and storage, flexible swelling reduction, greening and other functions.

[0005] However, the current domestic use of lattice beams to reinforce expansive soil slopes has the following disadvantages: ① Although various ancillary facilities and devices are set up, in general, the lattice beams are still directly set on the slope surface and directly bear the strong expansion pressure of the expansive soil slope in the rainy season and the phenomenon of the bottom of the lattice beam being hollowed out due to shrinkage in the dry season; ② Ancillary facilities such as air cavities, elastic rubber sheets, expansion bolts, expansion anchors, vegetation protection mats and drainage devices are directly exposed to the harsh atmospheric environment of the slope surface. As time goes by, the above-mentioned devices are prone to aging, deterioration, rust and other phenomena, resulting in loss of their functions; ③ When using lattice beams, ordinary anchor rods (full-length bonded anchor rods) are mostly used at the intersections of the lattice beams, and no prestress is applied to the anchor rods, which is not conducive to the control of slope deformation. Summary of the invention

[0006] To solve the above problems, the present invention provides a suspended anchor cable lattice beam expansive soil slope retaining structure and a construction method, which can be applied to the reinforcement and management of excavated slopes or natural slope projects of different sizes and heights in expansive soil areas.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A suspended anchor cable lattice beam expansive soil slope retaining structure, comprising an anchor pier, a suspended lattice cross beam, a suspended lattice longitudinal beam, a prestressed anchor cable, a retaining structure foundation and a retaining structure crown beam, wherein the anchor pier, the lattice cross beam and the lattice longitudinal beam are integrally cast in situ on the expansive soil slope surface and are formed in one step, wherein the anchor pier is arranged in a groove on the slope surface and is in direct contact with the expansive soil slope and acts together with the prestressed anchor cable arranged at the center of the anchor pier to ensure the overall stability of the slope in the dry season, and the lattice cross beam and the lattice longitudinal beam are rigidly connected to the side of the anchor pier and are suspended at a certain height from the expansive soil slope to withstand rain In order to withstand the small expansion pressure of soil in the dry season, the lattice crossbeams and lattice longitudinal beams suspended rigidly connected around the anchor piers on the slope actively detach from the slope surface in the dry season and contact the raised slope surface in the rainy season to withstand the small expansion pressure of soil. Especially in the rainy season, the slope surface is allowed to deform to a certain extent to release a certain expansion pressure, while the slope surface is restricted from deforming too much to cause the instability of the expansive soil slope. The retaining structure foundation and the retaining structure cap beam are respectively cast in place reinforced concrete at the two ends of the lattice longitudinal beam in batches, and are respectively set at the foot and top of the expansive soil slope.

[0009] Furthermore, the anchor pier is rigidly connected with lattice cross beams and lattice longitudinal beams for connecting adjacent anchor piers in a symmetrical manner in the longitudinal and transverse directions. The top surfaces of the lattice cross beams and lattice longitudinal beams are flush with the top surfaces of the anchor piers. The anchor pier is arranged in a groove on the slope and its height is greater than the height of the lattice cross beams and the lattice longitudinal beams, and the bottom surfaces of the lattice cross beams and the lattice longitudinal beams are provided with a certain suspended height from the slope surface. The suspended height should be reasonably determined according to the expansibility of the expansive soil of the slope.

[0010] Furthermore, the steel cage of the anchor pier is double-layered and bidirectionally reinforced, the longitudinal stress-bearing steel bars of the lattice crossbeam and the lattice longitudinal beam respectively pass through the middle of the steel cage of the anchor pier near the top horizontally and longitudinally, and the stress-bearing longitudinal bars of the lattice crossbeam and the longitudinal beam are symmetrically and evenly arranged vertically and horizontally.

[0011] Furthermore, a hole for the prestressed anchor cable to pass through is provided in the middle of the anchor pier, and the inclination angle of the hole is determined comprehensively based on the slope of the expansive soil and the incident angle of the prestressed anchor, and the diameter of the hole is controlled within a range of 50mm-100mm so as not to hinder the passage of the outer anchor section of the prestressed anchor cable.

[0012] Furthermore, a stirrup densification zone is provided for the longitudinal force-bearing steel bars of the lattice crossbeam and the longitudinal beam within a range of not less than 500mm on the side of the anchor pier, the spacing of the stirrups in the stirrup densification zone is not greater than 100mm, and the spacing of the stirrups in the non-stirrup densification zone of the lattice crossbeam and the lattice longitudinal beam is 150mm-200mm.

[0013] Furthermore, the prestressed anchor cable adopts steel strand or high-strength precision-rolled threaded steel, one end of which is anchored to the top surface of the anchor pier by an anchor, and the other end penetrates deep into the expansive soil slope; and a detachable sealing anchor is arranged on the outer anchor section of the prestressed anchor cable on the top surface of the anchor pier to prevent the outer anchor section of the prestressed anchor cable from rusting.

[0014] The present invention also provides a construction method of the above-mentioned suspended anchor cable lattice beam expansive soil slope retaining structure, comprising the following steps:

[0015] S1. Excavate the expansive soil slope rock mass within a segment, trim the slope surface, and measure and lay out;

[0016] S2. Cut grooves at the anchor pier position on the expansive soil slope: cut grooves perpendicular to the slope surface according to the anchor pier position marked on the slope surface. The groove plane on the slope surface is slightly larger than the plane size of the anchor pier, and the groove depth is not less than 200mm;

[0017] S3. Setting prestressed anchor cables: Drill holes for prestressed anchor cables at the center of the grooves of the anchor piers at a predetermined incident angle according to the construction drawing requirements. After cleaning the holes, install the prestressed anchor cables in the holes and inject mortar for curing to strengthen them.

[0018] S4. Construction of suspended lattice beams: cast anchor piers, lattice cross beams and lattice longitudinal beams in one go on the slope surface of the expansive soil slope with cast-in-place reinforced concrete. The anchor piers are set in the grooves on the slope surface and are in direct contact with the expansive soil slope. The lattice cross beams and lattice longitudinal beams are rigidly connected to the sides of the anchor piers and are suspended at a certain height from the slope surface of the expansive soil slope.

[0019] S5. Tensioning and locking of anchor cable prestress;

[0020] S6. Other auxiliary operations: (1) After the prestressed anchor cable passing through the anchor pier is tensioned and locked, the retaining structure foundation and the retaining structure crown beam are cast in batches at the foot and top of the slope respectively by using cast-in-place reinforced concrete; (2) Removable sealing anchors are set for the outer anchor sections of the prestressed anchor cable on the top surface of the anchor pier one by one; (3) A foot drainage ditch and a top intercepting ditch are set for the expansive soil slope retaining structure near the foot and top of the slope respectively; (4) Grass is planted, concrete is sprayed or mortared with stone on the expansive soil slope surface in the frame of the suspended retaining structure as needed to seal the expansive soil slope surface to prevent direct infiltration of rainwater and erosion by running water.

[0021] Furthermore, the step S4 comprises the following steps:

[0022] S41. Reinforcement engineering: The outer anchor section of the prestressed anchor cable is passed through the steel cage of the anchor pier from the bottom and the steel cage of the anchor pier is set in the groove on the slope surface. Then, the steel cage of the anchor pier is passed through the steel cage in the horizontal and longitudinal directions to set the longitudinal stress-bearing steel bars for the lattice cross beam and the lattice longitudinal beam and the stirrups are tied for the longitudinal stress-bearing steel bars.

[0023] S42, Formwork engineering: Formwork is set up for anchor piers, lattice beams and lattice longitudinal beams respectively. The bottom membrane of the lattice beams and lattice longitudinal beams adopts a foam board of a certain thickness so that after the concrete pouring is completed, the bottom surface of the lattice beams and lattice longitudinal beams has a certain suspended height from the slope surface;

[0024] S43. Concrete work: Cast in-situ concrete for a segmented expansive soil slope retaining structure within the formwork and cure it for strength.

[0025] Furthermore, in step S6, when sprayed concrete or mortared stone sheets are used to seal the expansive soil slope surface, the suspended height of the lattice cross beams and lattice longitudinal beams should be reserved in advance according to the thickness of the sprayed layer or mortared stone sheets.

[0026] Furthermore, the anchor pier, the lattice cross beam, the lattice longitudinal beam, the retaining structure foundation and the retaining structure cap beam are made of concrete with a strength grade not less than C30.

[0027] The expansive soil slope retaining structure of the present invention is a variant of the conventional cast-in-place reinforced concrete retaining structure. After years of practice, its construction process is simple and reliable, the construction quality is guaranteed, and it has the following beneficial effects:

[0028] (1) The combined slope retaining structure of the present invention mainly comprises reinforced concrete components and metal components (anchor cables and anchors), wherein the anchor cables are wrapped by mortar in the anchor holes and the anchors are sealed by sealing anchors, so that they are not prone to rust and deterioration, which is beneficial to ensuring the durability of the slope retaining structure;

[0029] (2) Setting prestressed anchor cables at the center of the anchor pier can actively load and effectively control the deformation of the slope and ensure the overall stability of the slope;

[0030] (3) The combined slope retaining structure of the present invention is both rigid and flexible. In the dry season, the prestressed anchor cables and rigid anchor piers are used to ensure the overall stability of the slope. In the rainy season, the flexible lattice cross beams and lattice longitudinal beams arranged around the anchor piers are used to withstand the small expansion pressure of the soil. This allows the slope soil to deform to a certain extent, thereby releasing a certain degree of expansion pressure, while preventing the slope soil from deforming too much.

[0031] (4) Planting grass, spraying concrete or mortaring flagstones in the frame on the slope can reduce the direct infiltration of rainwater on the slope, avoid large expansion deformation and avoid rainwater scouring on the slope;

[0032] (5) The provision of a detachable anchor seal on the outer anchor section of the prestressed anchor cable is conducive to multiple compensatory tensioning of the prestressed anchor cable to cope with the excessive relaxation of the prestress of the anchor cable under repeated expansion and contraction conditions;

[0033] (6) If grass or small shrubs are planted in the frame of the composite retaining structure after completion, it will be conducive to coordination with the surrounding environment and beneficial to environmental protection.

[0034] Therefore, the present invention can be applied to the reinforcement and management of excavation slopes or natural slope projects of different sizes and heights in expansive soil areas, and is particularly suitable for the reinforcement and management of strong expansive soil slopes with large expansion deformation. It is a suspended anchor cable lattice beam expansive soil slope retaining structure and construction method worthy of popularization and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0036] Figure 1 A three-dimensional diagram of an expansive soil slope retaining structure of a suspended anchor cable lattice beam according to an embodiment of the present invention;

[0037] Figure 2 This is a cross-sectional view of an expansive soil slope retaining structure of a suspended anchor cable lattice beam according to an embodiment of the present invention;

[0038] In the figure: 1. Suspended anchor cable lattice beam; 101. Anchor pier; 102. Lattice cross beam; 103. Lattice longitudinal beam; 104. Prestressed anchor cable; 105. Foundation; 106. Crown beam; 107. Removable sealing anchor; 2. Drainage ditch at the foot of the slope; 3. Intercepting ditch at the top of the slope. DETAILED DESCRIPTION

[0039] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0040] Embodiment 1:

[0041] A suspended anchor cable lattice beam expansive soil slope retaining structure, which is suitable for both the reinforcement and management of natural slopes in expansive soil areas and the reinforcement and management of excavated slopes. Figure 1-Figure 2As shown, the suspended anchor cable lattice beam 1 comprises: a reinforced concrete anchor pier 101; a lattice cross beam 102; a lattice longitudinal beam 103; a prestressed anchor cable 104; a retaining structure foundation 105; a retaining structure crown beam 106 and a detachable sealing anchor 107.

[0042] in:

[0043] The anchor pier 101 is a cast-in-place reinforced concrete solid structure, and its overall shape can be a cube, a cuboid, a cylinder, a frustum or other forms. This embodiment takes a cuboid anchor pier as an example, and its outer dimensions B×L×H are the recommended dimensions or other dimensions shown in Table 1. Among them, B, L and H are the width, length and height of the anchor pier 101 respectively.

[0044] The lattice cross beam 102 and the lattice longitudinal beam 103 are both cast-in-place reinforced concrete rectangular cross-section beams. The cross-sectional dimensions b×h of the lattice beams are designed according to the recommended parameters in Table 1 or other dimensions. The length l of the lattice cross beam 102 and the lattice longitudinal beam 103 should be determined according to the spacing of the anchor piers 101 on the slope surface. The length l can also be selected according to the recommended parameters in Table 1 or comprehensively determined according to the actual situation of the slope surface. In Table 1, b, h and l are the width, height and length of the post-cast lattice beam, respectively.

[0045] Table 1 Recommended geometric parameters of suspended lattice beams (unit: mm)

[0046] model Anchor pier cross-sectional dimensions B×L×H Cross-beam and longitudinal beam cross-sectional dimensions b×h Effective length of crossbeam and longitudinal beam l Model A 800×800×600 300×300 800 Model B 900×900×650 350×350 1200 Model C 1000×1000×700 400×400 1500 Model D 1100×1100×750 450×450 2000 Model E 1200×1200×800 500×500 2500 Model F 1500×1500×1000 600×600 3000

[0047] The anchor pier 101 is rigidly connected with lattice cross beams 102 and lattice longitudinal beams 103 for connecting adjacent anchor piers 101 symmetrically in the longitudinal and transverse directions. The top surfaces of the lattice cross beams 102 and the lattice longitudinal beams 103 are preferably flush with the top surfaces of the anchor piers 101. The anchor pier 101 is arranged in the groove of the slope surface and its height is greater than the height of the lattice cross beams 102 and the lattice longitudinal beams 103. The bottom surfaces of the lattice cross beams 102 and the lattice longitudinal beams 103 are allowed to have a certain suspended height from the slope surface. The suspended height should be reasonably determined based on the expansibility of the expansive soil of the slope, and the suspended height can also be taken as 50mm-100mm based on experience.

[0048] The steel cage of the anchor pier 101 is double-layered and bidirectionally reinforced, and the longitudinal force-bearing steel bars of the lattice crossbeam 102 and the lattice longitudinal beam 103 respectively pass through the middle of the steel cage of the anchor pier 101 near the top horizontally and longitudinally. The longitudinal force-bearing bars of the lattice crossbeam 102 and the longitudinal beam 103 are preferably symmetrically and evenly arranged to 4, 6 or 8 bars, etc.

[0049] A hole for the prestressed anchor cable 104 to pass through should be provided in the middle of the anchor pier 101. The inclination angle of the hole in the anchor pier 1 should be determined comprehensively based on the slope of the expansive soil and the incident angle of the prestressed anchor cable 104. The diameter of the hole should be such that it does not hinder the passage of the outer anchor section of the prestressed anchor cable 104, and is generally controlled at 50mm-100mm.

[0050] The anchor pier 101, the lattice cross beam 102 and the lattice longitudinal beam 103 are integrally cast in one step by cast-in-situ reinforced concrete on the slope surface of the expansive soil, and the retaining structure foundation 105 and the retaining structure cap beam 106 can be formed by cast-in-situ reinforced concrete in batches at a later time after the prestressed anchor cable 104 passing through the position of the anchor pier 101 is tensioned and locked.

[0051] The anchor pier 101, the lattice cross beam 102, the lattice longitudinal beam 103, the retaining structure foundation 105 and the retaining structure cap beam 106 should preferably be made of concrete with a strength grade not less than C30, and high-strength concrete should be used preferentially if conditions permit.

[0052] The longitudinal force-bearing steel bars of the anchor pier 101, the lattice cross beam 102, the lattice longitudinal beam 103, the retaining structure foundation 105 and the retaining structure crown beam 106 should be HRB400, HRB500, HRBF400, HRBF500 grade steel bars, and the stirrups should be HPB300 grade plain round steel bars or HRB400 grade ribbed steel bars, and the diameter of the plain round stirrups should be no less than 8 mm.

[0053] A stirrup densification zone should be set for the longitudinal force-bearing reinforcement of the lattice crossbeam 102 and the longitudinal beam 103 within a range of not less than 500mm on the side of the anchor pier 101. The spacing of the stirrups in the stirrup densification zone should not be greater than 100mm. The spacing of the stirrups in the non-stirrup densification zone of the lattice crossbeam 102 and the lattice longitudinal beam 103 should be 150mm-200mm.

[0054] The prestressed anchor cable 104 passing through the hole at the center of the anchor pier 101 is preferably made of steel strands or high-strength precision-rolled threaded steel. One end of the prestressed anchor cable 104 is directly anchored to the top surface of the anchor pier 101 using an anchor (including a steel pad), and the other end penetrates deep into the expansive soil slope, providing a strong anchoring force for the prestressed anchor cable 104 in the stable rock and soil body that is not affected by climate.

[0055] After the prestressed anchor cable 104 is tensioned and locked, a detachable sealing anchor 107 is provided on the top surface of the anchor pier 101 for the outer anchor section of the prestressed anchor cable 104 to prevent the outer anchor section of the prestressed anchor cable 104 from rusting. The detachable sealing anchor 107 can be easily disassembled, replaced or reused to compensate for the tensioning of the prestressed anchor cable 104 to prevent the prestressed anchor cable 104 from being excessively relaxed and causing instability of the expansive soil slope.

[0056] Embodiment 2:

[0057] A construction method of a suspended anchor cable lattice beam expansive soil slope retaining structure is applicable to both the reinforcement and management of natural slopes in expansive soil areas and the reinforcement and management of excavated slopes. Taking the expansive soil excavated slope as an example, the construction process is introduced in detail. Before on-site construction, the entire expansive soil slope should be divided into several grades or sections according to the requirements of the slope height, expansion joints, settlement joints and seismic joints of the retaining structure, and then one level (or one section) is excavated and supported.

[0058] This second embodiment only introduces the construction process of a segmented expansive soil slope retaining structure. Repeating this construction process can complete the construction process of other graded or segmented expansive soil slope retaining structures. Specifically, the construction steps of a segmented expansive soil slope reinforced with a suspended anchor lattice beam are as follows:

[0059] S1: excavate the expansive soil slope rock mass in a segment, trim the slope surface, and measure and lay out. Specifically, excavate the slope rock mass according to the construction drawings, measure and lay out the expansive soil slope surface after excavation, and mark the positions of the anchor piers 101, lattice cross beams 102, and lattice longitudinal beams 103 on the slope surface.

[0060] S2: Grooving the anchor pier position on the slope surface of the expansive soil. According to the position of the anchor pier 101 marked on the slope surface, a groove is made perpendicular to the slope surface to set the anchor pier 101 on the slope surface. The plane of the slope groove should be slightly larger than the plane size of the anchor pier 101, and the groove depth should be no less than 200mm.

[0061] S3: Set up prestressed anchor cables. According to the requirements of the construction drawings, the prestressed anchor cables 104 are drilled into the slope at the center of the groove of the anchor pier 101 at a predetermined incident angle using a drilling rig. After the holes are cleaned with a high-pressure air gun, the prestressed anchor cables 104 are installed in the holes and mortar is injected for curing. Note that the outer anchor section of the prestressed anchor cables 104 should not be touched at will during the mortar curing period.

[0062] S4: Construction of suspended lattice beams. It includes the following basic operations and processes: (1) Reinforcement engineering. The outer anchor section of the prestressed anchor cable 104 is passed through the steel cage of the anchor pier 101 from the bottom and the steel cage of the anchor pier 101 is set in the groove on the slope surface. Then, the steel cage of the anchor pier 101 is passed through the steel cage in the horizontal and longitudinal directions to set the longitudinal force-bearing steel bars for the lattice cross beam 102 and the lattice longitudinal beam 103 and tie the stirrups for the longitudinal force-bearing steel bars; (2) Formwork engineering. Formworks are set for the anchor pier 101, the lattice cross beam 102 and the lattice longitudinal beam 103 respectively. Among them, the bottom membrane of the lattice cross beam 102 and the lattice longitudinal beam 103 should be made of foam board of a certain thickness so that after the concrete is poured, the bottom surface of the lattice cross beam 102 and the lattice longitudinal beam 103 has a certain suspended height from the slope surface; (3) Concrete operation. A segmented expansive soil slope retaining structure is cast in situ concrete in the formwork and cured for strength. Note: When setting up steel cages and formwork on the slope, reliable temporary reinforcement measures should be taken for the steel cages and formwork to prevent the steel cages and formwork from sliding or tipping over along the slope during construction.

[0063] S5: Tensioning and locking of prestressed anchor cables. After the maintenance is completed on the slope, the reinforced concrete products of the retaining structure are demoulded, and the prestressed anchor cables 104 passing through the anchor piers 101 of the retaining structure in a segment are tensioned and locked one by one in a certain order using a through-type jack. The locking value of the prestressed anchor cables should be 0.75-0.90 times the standard value of the axial force of the prestressed anchor cables.

[0064] S6: Other auxiliary operations. Specifically, the following operations are included: (1) After the prestressed anchor cable 104 passing through the anchor pier 101 is tensioned and locked, a cast-in-place retaining structure foundation 105 and a retaining structure crown beam 106 are respectively set at the foot of the slope and the top of the slope as a segmented slope retaining structure; (2) Removable sealing anchors 107 are set for the outer anchor sections of the prestressed anchor cable 104 on the top surface of the anchor pier 101 one by one; (3) A foot drainage ditch 2 and a top intercepting ditch 3 are respectively set near the foot of the slope and near the top of the slope for the expansive soil slope retaining structure; (4) Planting grass, spraying concrete or mortaring flagstones on the expansive soil slope surface in the frame of the suspended retaining structure as needed to seal the expansive soil slope surface to prevent direct rainwater infiltration and water erosion. Note: When using shotcrete or mortar-laid flagstones to seal the expansive soil slope surface, the suspended height of the lattice cross beam 102 and the lattice longitudinal beam 103 should be reserved in advance according to the thickness of the shotcrete layer or mortar-laid flagstones.

[0065] It is worth noting that the above construction work should be carried out quickly under long-term rainless weather conditions in the dry season to avoid shrinkage of the expansive soil caused by evaporation. In addition, after the expansive soil slope reinforcement is completed, as time goes by, it is necessary to timely monitor the axial force value of the prestressed anchor cable of the expansive soil slope retaining structure during service. When the prestress of the anchor cable is too relaxed, the detachable anchor 107 should be removed in time and the prestressed anchor cable 104 should be compensated for by tensioning to avoid the anchor cable prestress 104 from leaving the work in advance, thereby causing the expansive soil slope to become unstable.

[0066] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A suspended anchor cable lattice beam expansive soil slope retaining structure, characterized in that: The invention comprises anchor piers, suspended lattice cross beams, suspended lattice longitudinal beams, prestressed anchor cables, retaining structure foundations and retaining structure crown beams. The anchor piers, lattice cross beams and lattice longitudinal beams are integrally formed at one time by cast-in-situ reinforced concrete on the slope surface of an expansive soil slope. The anchor piers are arranged in a groove on the slope surface and in direct contact with the expansive soil slope. The lattice cross beams and the lattice longitudinal beams are rigidly connected to the sides of the anchor piers and are suspended at a certain height from the slope surface of the expansive soil slope. The retaining structure foundation and the retaining structure crown beam are respectively formed by cast-in-situ reinforced concrete at the two ends of the lattice longitudinal beams in batches at a later stage and are respectively arranged at the foot and top of the expansive soil slope.

2. The suspended anchor cable lattice beam expansive soil slope retaining structure according to claim 1, characterized in that: The anchor pier is rigidly connected with lattice cross beams and lattice longitudinal beams for connecting adjacent anchor piers in a symmetrical manner in the longitudinal and transverse directions. The top surfaces of the lattice cross beams and lattice longitudinal beams are flush with the top surfaces of the anchor piers. The anchor pier is arranged in the groove of the slope surface and its height is greater than the height of the lattice cross beams and the lattice longitudinal beams. The bottom surfaces of the lattice cross beams and the lattice longitudinal beams are suspended at a certain height from the slope surface.

3. The suspended anchor cable lattice beam expansive soil slope retaining structure according to claim 1, characterized in that: The steel cage of the anchor pier is double-layered and bidirectionally reinforced, and the longitudinal stress-bearing steel bars of the lattice crossbeam and the lattice longitudinal beam respectively pass through the middle of the steel cage of the anchor pier near the top horizontally and longitudinally, and the stress-bearing longitudinal bars of the lattice crossbeam and the longitudinal beam are symmetrically and evenly arranged vertically and horizontally.

4. The suspended anchor cable lattice beam expansive soil slope retaining structure according to claim 1, characterized in that: A hole for the prestressed anchor cable to pass through is provided in the middle of the anchor pier. The inclination angle of the hole is determined comprehensively according to the slope of the expansive soil slope and the incident angle of the prestressed anchor. The diameter of the hole is controlled within 50mm-100mm so as not to hinder the passage of the outer anchor section of the prestressed anchor cable.

5. The suspended anchor cable lattice beam expansive soil slope retaining structure according to claim 1, characterized in that: A stirrup densification zone is provided for the longitudinal force-bearing reinforcement of the lattice crossbeam and the longitudinal beam within a range of not less than 500mm on the side of the anchor pier, the spacing of the stirrups in the stirrup densification zone is not greater than 100mm, and the spacing of the stirrups in the non-stirrup densification zone of the lattice crossbeam and the lattice longitudinal beam is 150mm-200mm.

6. The suspended anchor cable lattice beam expansive soil slope retaining structure according to claim 1, characterized in that: The prestressed anchor cable is made of steel strand or high-strength precision-rolled threaded steel, one end of which is anchored on the top surface of the anchor pier with an anchor, and the other end extends deep into the expansive soil slope; and a detachable sealing anchor is provided on the outer anchor section of the prestressed anchor cable on the top surface of the anchor pier.

7. A construction method for a suspended anchor cable lattice beam expansive soil slope retaining structure according to any one of claims 1 to 6, characterized in that: The steps include: S1. Excavate the expansive soil slope rock mass within a segment, trim the slope surface, and measure and lay out; S2. Cut grooves at the anchor pier position on the expansive soil slope: cut grooves perpendicular to the slope surface according to the anchor pier position marked on the slope surface. The plane of the slope groove is larger than the plane size of the anchor pier, and the groove depth is not less than 200mm; S3. Setting prestressed anchor cables: Drill holes for prestressed anchor cables at the center of the grooves of the anchor piers at a predetermined incident angle according to the construction drawing requirements. After cleaning the holes, install the prestressed anchor cables in the holes and inject mortar for curing to strengthen them. S4. Construction of suspended lattice beams: cast anchor piers, lattice cross beams and lattice longitudinal beams in one go on the slope surface of the expansive soil slope with cast-in-place reinforced concrete. The anchor piers are set in the grooves on the slope surface and are in direct contact with the expansive soil slope. The lattice cross beams and lattice longitudinal beams are rigidly connected to the sides of the anchor piers and are suspended at a certain height from the slope surface of the expansive soil slope. S5. Tensioning and locking of anchor cable prestress; S6. Other auxiliary operations: (1) After the prestressed anchor cable passing through the anchor pier is tensioned and locked, the retaining structure foundation and the retaining structure crown beam are cast in batches at the foot and top of the slope respectively by using cast-in-place reinforced concrete; (2) Removable sealing anchors are set for the outer anchor sections of the prestressed anchor cable on the top surface of the anchor pier one by one; (3) Drainage ditches at the foot of the slope and intercepting ditches at the top of the slope are set near the foot of the slope and near the top of the slope respectively; (4) Grass is planted, concrete is sprayed or mortared with stone slabs on the expansive soil slope surface in the frame of the suspended retaining structure as needed to seal the expansive soil slope surface to prevent direct rainwater infiltration and water erosion.

8. The construction method of the suspended anchor cable lattice beam expansive soil slope retaining structure according to claim 7, characterized in that: The step S4 comprises the following steps: S41. Reinforcement engineering: The outer anchor section of the prestressed anchor cable is passed through the steel cage of the anchor pier from the bottom and the steel cage of the anchor pier is set in the groove on the slope surface. Then, the steel cage of the anchor pier is passed through the steel cage in the horizontal and longitudinal directions to set the longitudinal stress-bearing steel bars for the lattice cross beam and the lattice longitudinal beam and the stirrups are tied for the longitudinal stress-bearing steel bars. S42, Formwork engineering: Formwork is set up for anchor piers, lattice beams and lattice longitudinal beams respectively. The bottom membrane of the lattice beams and lattice longitudinal beams adopts a foam board of a certain thickness so that after the concrete pouring is completed, the bottom surface of the lattice beams and lattice longitudinal beams has a certain suspended height from the slope surface; S43. Concrete work: Cast in-situ concrete for a segmented expansive soil slope retaining structure within the formwork and cure it for strength.

9. The construction method of a suspended anchor cable lattice beam expansive soil slope retaining structure according to claim 7, characterized in that: In step S6, when sprayed concrete or mortared stone sheets are used to seal the expansive soil slope surface, the suspended height of the lattice cross beams and the lattice longitudinal beams needs to be reserved in advance according to the thickness of the sprayed layer or mortared stone sheets.

10. The construction method of the suspended anchor cable lattice beam expansive soil slope retaining structure according to claim 7, characterized in that: The anchor pier, the lattice cross beam, the lattice longitudinal beam, the retaining structure foundation and the retaining structure crown beam are made of concrete with a strength grade not lower than C30.

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