Construction method of circular self-locking anchor support for foundation pit

Abstract

The present invention discloses a construction method for annular self-locking anchor support in a foundation pit, comprising the steps of interlocking pile construction, first-layer earthwork excavation, ring beam construction, tensioning of slow-bonding prestressed steel strands, second-layer earthwork excavation, and installation of ceramic hanging panels. This method fully utilizes the mechanical properties of slow-bonding prestressed steel strands and the concrete ring beam, offering advantages such as reliable process, simple construction, no need for anchor cables or bolts, minimal damage to the central island soil, a short construction period, and uniform stress distribution.

Description

Technical Field

[0001] The invention belongs to the technical field of building construction, and in particular relates to a foundation pit annular self-locking anchor support construction method. Background Art

[0002] Existing foundation pit annular support technology mainly includes supporting piles, applying anchor rods and cables, hanging mesh and spraying concrete, etc. For example, patent invention number 201810951769.X discloses a large-span foundation pit support construction method with steel anchor cables. The main construction steps are constructing steel bearing columns; installing the steel bars of the first-layer annular beam, top beam, first-layer support beam and diagonal beam; tensioning steel anchor cables; installing the steel bars of the second-layer annular beam, waist beam and second-layer support beam; after the concrete strength of the second-layer annular beam, waist beam and second-layer support beam reaches 100% of the design strength, excavating the earth outside the second-layer annular beam; after the basement floor slab outside the secondary annular beam is poured, excavate the remaining earth inside the second-layer annular beam; support the steel stamps and formwork of the basement side walls and pour concrete; dismantle the support structure, and the support structure is dismantled by smooth cutting blasting; dismantling the steel anchor cables; cutting off the connection between the steel bars of the first-layer support beam or the second-layer support beam and the steel bearing column, and pulling out the steel bearing column.

[0003] Comprehensive existing technologies include patent invention number 201810951769.X, a large-span foundation pit support construction method with steel anchor cables. Anchor cables, anchor rods and other structures are required for foundation pit support. However, these construction methods are not suitable for some specific scenarios. For example, in the construction of new urban areas, there are often precious trees or other ground buildings. In order to protect these precious trees, buildings need to be relocated or retained in situ. However, these precious trees or ground buildings are retained in situ and are located in the center of the project construction area. When a basement needs to be built, this central island must be completely protected. If the existing circular foundation pit support technology is used, it is necessary to drive anchor cables and anchor rods into the soil of the central island, thereby destroying the root system of the precious trees or the foundation of the building. Summary of the Invention

[0004] In order to solve the deficiencies in the prior art, the present invention provides a foundation pit annular self-locking anchor support construction method which does not require anchor cables and anchor rods and reduces damage to the soil of the central island.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] The foundation pit annular self-locking anchor support construction method includes the following steps:

[0007] S1. Construction of interlocking piles: With the center of the central island as the center of the circle, interlocking piles are constructed at the edge of the central island for support;

[0008] S2. Excavation of the first layer of earthwork: After the construction of the interlocking piles in S1 is completed, the first layer of earthwork is excavated outside the interlocking piles until it reaches the designed elevation of the first layer of earthwork excavation;

[0009] S3. Ring beam construction: The ring beam is constructed on the outer wall of the interlocking pile and the slow-bonding prestressed steel strands are embedded in the ring beam;

[0010] S4, tensioning of slow-bonding prestressed steel strands: applying prestress to the slow-bonding prestressed steel strands embedded in S3 for tensioning and sealing the ends;

[0011] S5, second layer earthwork excavation: continue to carry out the second layer earthwork excavation outside the interlocking pile until the design elevation of the second layer earthwork excavation is reached, and then repeat steps S3 and S4 in sequence until the total support elevation is reached;

[0012] S6. Ceramic hanging board installation: Install ceramic panels on the outer wall of the interlocking piles between two adjacent ring beams.

[0013] Preferably, in step S1, the pile position is firstly laid out at the edge of the center island with the center of the center island as the center of the circle, and then the guide groove is constructed, the pipe rolling machine is moved to the construction position, and the pipe rolling machine rolls the casing and drills it. After the casing is in place, the drilling machine is used and the drill rod of the drilling machine is extended into the casing to drill a hole. After the drilling and cleaning are completed, the interlocking pile is constructed and placed, and the casing is pulled out after the placement is completed.

[0014] Preferably, in said S2, the strength quality of the interlocking piles in S1 is first checked, and then the effect of foundation pit dewatering is detected, and then the water level of the deep well dewatering in the excavation area is measured and set. After the measurement and setting are completed, the foundation pit is positioned and laid out, and the upper edge line of the excavated foundation pit is first measured, and then the position and elevation of the bottom edge line of the foundation pit are measured. When the excavator digs to a distance of 10 cm from the design elevation of the first layer of earth excavation, manual excavation is used to reach the design elevation of the first layer of earth excavation.

[0015] Preferably, in said S3, the hanging plate steel bars are first installed on the outer wall of the interlocking pile, and then the side formwork is installed on the outer side of the outer wall of the interlocking pile, and then a tension rod is added every 900 mm on the side formwork, and then the ring beam ordinary steel bars are installed in the side formwork, the ring beam ordinary steel bars use beam stirrups as support bars and are fixed by welding with binding wire or U-shaped bars, and then slow-bonding prestressed steel strands are embedded in the ring beam ordinary steel bars, and then a plastic pipe is set in the side formwork along the up and down directions, and then the concrete is transported into the side formwork by a car pump, and vibrated densely with an insert-type vibrating pump to form a ring beam.

[0016] Preferably, the slow-bonding prestressed steel strand in S3 includes several steel strands, an externally coated slow-bonding adhesive and a plastic sleeve, the several steel strands are located in the plastic sleeve and the externally coated slow-bonding adhesive is filled between the several steel strands in the plastic sleeve.

[0017] Preferably, before using the automobile pump to transport concrete to the side formwork in S3, first check whether the ring beam ordinary steel bars and slow-bonding prestressed steel strands are installed, and then remove the garbage and soil in the ring beam formwork and the oil stains on the ring beam ordinary steel bars and slow-bonding prestressed steel strands.

[0018] Preferably, the upper end of the plastic tube is higher than or equal to the upper side of the ring beam, the lower end of the plastic tube is lower than or equal to the lower side of the ring beam, and the inner hole of the plastic tube is a reserved hole for the ring beam.

[0019] Preferably, in S4, spiral ribs and steel pads are sequentially installed at both ends of the slow-bonding prestressed steel strand, the spiral ribs are welded to the steel pads, and then a clip is installed on the outside of the steel pad of the slow-bonding prestressed steel strand. Then, an oil pump and a jack are taken and one end of the jack is connected to the oil pump, and then the other end of the jack is installed on the outside of the clip on the slow-bonding prestressed steel strand to apply prestress to the slow-bonding prestressed steel strand for tensioning. The slow-bonding prestressed steel strand is tensioned symmetrically in batches at both ends, and the ends are sealed after tensioning.

[0020] Preferably, in said S6, in a bottom-up order, the ceramic plate is first mounted between the two adjacent ring beams at the bottom, and then sequentially mounted upwards until the ceramic plate is mounted between the two adjacent ring beams at the top, the front left portion and the front right portion of the ceramic plate are respectively provided with two first combination portions and two second combination portions at intervals from top to bottom, the first combination portion located above the front left portion of the ceramic plate is adapted to the second combination portion located above the front right portion of the ceramic plate, the first combination portion located below the front left portion of the ceramic plate is adapted to the second combination portion located below the front right portion of the ceramic plate, and both the first combination portion and the second combination portion are provided with sockets;

[0021] The specific steps of mounting the ceramic plate on the outer wall of the interlocking pile between two adjacent layers of ring beams in S6 are as follows: first take the first ceramic plate and the first steel bar, then align the two first combination parts of the first ceramic plate with the ring beam pre-set holes of the two ring beams respectively, and then insert the first steel bar from top to bottom into the ring beam pre-set hole of the ring beam on the upper side, the jack of the first combination part of the first ceramic plate located above, the jack of the first combination part of the first ceramic plate located below, and the ring beam pre-set hole of the ring beam on the lower side, then take the second ceramic plate and the second steel bar, and then make the two first combination parts of the second ceramic plate fit with the two second combination parts of the first ceramic plate and insert the second steel bar to fix it, and then proceed by analogy, until the two first combination parts of the last ceramic plate are aligned with the two second combination parts of the first ceramic plate. After the second combination parts of the second number of ceramic plates are assembled together, pull out the first steel bar, and then make the two first combination parts of the first ceramic plate and the two second combination parts of the last ceramic plate adapt and assemble, and make the sockets of the two first combination parts of the first ceramic plate and the sockets of the two second combination parts of the last ceramic plate correspond to the ring beam reserved holes above and below, and finally insert the first steel bar into the ring beam reserved hole of the upper ring beam, the socket of the first combination part of the first ceramic plate located above, the socket of the second combination part of the last ceramic plate located above, the socket of the first combination part of the first ceramic plate located below, the socket of the second combination part of the last ceramic plate located below and the ring beam reserved hole of the ring beam located below from top to bottom, completing the installation of the ceramic plates.

[0022] By adopting the above technical solution, the present invention has the following beneficial effects:

[0023] (1) The construction process of the present invention is suitable for construction scenarios where there are precious trees or other ground buildings on the ground. During the construction process, there is no need to drive anchor rods and cables, which will not damage the root systems of precious trees or the foundations of ground buildings, thereby reducing damage to the land of the central island;

[0024] (2) The existing foundation pit annular support technology requires anchor rods and cables and grouting. After grouting, it is necessary to wait for the grout to solidify before tensioning can be carried out, which takes a long construction period. The present invention eliminates this step, shortens the construction period, and reduces labor costs.

[0025] (3) The present invention uses slow-bonding prestressed steel strands to apply pre-tensioning force to form a self-locking support structure. Compared with the existing technology, there is no need to bury corrugated pipes or grout the corrugated pipes. The process is reliable and the construction is simple.

[0026] (4) The present invention constructs a ring beam on the outer wall of the interlocking pile. After the ring beam is constructed, the slow-bonding prestressed steel strand can be tensioned, so that the ring beam clamps the interlocking pile, giving full play to the mechanical properties of the slow-bonding prestressed steel strand and the ring beam made of concrete, and the interlocking pile is evenly stressed due to the arrangement of the ring beam;

[0027] In summary, the present invention gives full play to the mechanical properties of slow-bonding prestressed steel strands and the ring beam made of concrete, and has the advantages of reliable process, simple construction, no need for anchor cables and anchor rods, little damage to the soil of the central island, short construction period, and uniform force. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a flow chart of the foundation pit annular self-locking anchor support construction method of the present invention;

[0029] Figure 2 It is a structural schematic diagram of the occlusal pile construction of the present invention;

[0030] Figure 3 It is a structural schematic diagram of the arrangement of slow-bonding prestressed steel strands of the present invention;

[0031] Figure 4 It is a structural schematic diagram of the support structure after construction of the present invention;

[0032] Figure 5 This is a schematic diagram of the structure of anchoring a slow-bonding prestressed steel strand constructed by the present invention;

[0033] Figure 6 This is a schematic diagram of the structure of anchoring another slow-bonding prestressed steel strand constructed according to the present invention;

[0034] Figure 7 yes Figure 4 Enlarged view of point P in the middle. DETAILED DESCRIPTION

[0035] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0036] The components of the embodiments of the present invention generally described and shown in the drawings herein may be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of the invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the invention.

[0037] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0038] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0039] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0040] Example 1

[0041] The present invention adopts the principle of "barrel hoops" to provide closed support for the retained central island 10.

[0042] like Figure 1 、 Figure 3 、 Figure 4 and Figure 7 As shown, in one embodiment of the present invention, the foundation pit annular self-locking anchor support construction method of the present invention includes the following steps:

[0043] S1, interlocking pile construction: with the center of the center island 10 as the center of the circle, an annular interlocking pile 20 is constructed on the edge of the center island 10 for support. Specifically, in the step S1, the pile position is firstly staked out on the edge of the center island 10 with the center of the circle as the center of the circle, and then the guide groove is constructed, that is, the guide groove is used for guidance and positioning, and then the pipe rolling machine is moved to the construction position, and the pipe rolling machine rolls the casing into the casing. After the casing is in place, that is, the casing is extended into the ground, the drilling machine is used and the drill rod of the drilling machine is extended into the casing to drill a hole. After the drilling and cleaning of the hole is completed, the interlocking pile 20 is constructed and placed. After the placement is completed, the casing is pulled out. More specifically, the interlocking pile 20 includes pile A and pile B. Figure 2The specific construction order is A1, A2, B1, A3, B2, A4, B3...AN, BN-1, until the last BN-1 pile is engaged with the A1 pile, and these A piles and B piles form a circle, ellipse, or other shape with the center of the central island 10. All A piles are plain concrete piles, that is, A1, A2, A3, A4...AN, etc. are all plain concrete piles, and all B piles are reinforced concrete piles, that is, B1, B2, B3...BN-1 are all reinforced concrete piles. During construction, the A piles are constructed first, and then the edges of the A piles on both sides of the B piles to be constructed are cut off using equipment. Then, a steel cage is placed and concrete is poured to form a reinforced concrete B pile. At this time, the B piles engage the two adjacent A piles, which are called interlocking piles 20.

[0044] S2, the first layer of earthwork excavation: after the construction of the interlocking piles 20 in S1 is completed, the foundation pit is first positioned and laid out on the outside of the interlocking piles 20 in S1, and then the foundation pit is excavated by an excavator. When the excavator excavates to a specific distance from the design elevation of the first layer of earthwork excavation, manual excavation is used to reach the design elevation of the first layer of earthwork excavation. Specifically, in S2, the strength and quality of the interlocking piles 20 in S1 are first checked to ensure the safety of earthwork excavation, and then the effect of foundation pit drainage is tested to ensure the order of earthwork excavation. It is required that the groundwater be lowered to the required depth two weeks before excavation, and then the deep well dewatering level of the excavation site is measured and set. The specific operation steps are: use a measuring rope to be placed in the pre-constructed dewatering well to measure the water level elevation, and then the foundation pit is positioned and laid out. First, the upper edge line of the excavated foundation pit is measured, and then the position and elevation of the bottom edge line of the foundation pit are measured, and then the excavator is used for excavation. Specifically, when operating the excavator, a large excavator can be used to dig and load the soil, and then the excavator can be used to dig and load the soil. When digging close to the central island 10, a small excavator is used for excavation. During the excavation process, it is strictly forbidden to touch the support structures such as the bite piles 20. When using the excavator for excavation, the excavation is carried out in sections. The length of each section can be set to 20-30m. When the excavator digs to 10cm from the design elevation of the first layer of earthwork excavation, manual excavation is used to the design elevation of the first layer of earthwork excavation to prevent soil disturbance. The design elevation of this first layer of earthwork excavation is actually the second ring beam 50 around the bite pile 20 during the actual construction process. The first ring beam 50 is arranged above the design elevation, that is, above the bite pile 20 is the crown beam 11. The construction process used by the crown beam 11 of the present invention is different from that used by the ring beam 50. No slow-bonding prestressed steel strand 40 is used for construction. After the excavation is completed, a 300mm*300mm drainage ditch is set around the top of the slope of the foundation pit, and 140mm brick membranes are laid on both sides of the drainage ditch, and 20mm thick 1:2.5 cement mortar is applied on the outside;

[0045] S3, construction of ring beam 50: The ring beam 50 is constructed on the outer wall of the interlocking pile 20 and the slow-bonding prestressed steel strands 40 are embedded in the ring beam 50. The construction of the ring beam 50 includes the following steps: installing the hanging plate steel bars, installing the side formwork, installing the ordinary steel bars of the ring beam, embedding the slow-bonding prestressed steel strands 40, setting the plastic pipe, and pouring concrete to form the ring beam 50;

[0046] More specifically, in S3, the hanging plate steel bars are first installed on the outer wall of the interlocking pile 20 and the hanging plate steel bars are tied. Here, the hanging plate steel bars are installed on the outer wall of the interlocking pile 20, that is, after the interlocking pile 20 is constructed and the earthwork is excavated, the outer sides of the A pile and the B pile of the interlocking pile 20 are exposed, and then waterproof screw rods are installed on the interlocking pile 20 by drilling or other methods, and then the hanging plate steel bars are tied to these waterproof screw rods. The hanging plate steel bars facilitate the subsequent installation of structures such as the side formwork and the ordinary steel bars of the ring beam;

[0047] Then install the side formwork on the outer side wall of the interlocking pile 20. Specifically, the side formwork adopts 18mm thick film-coated plywood, and the back rib adopts 100*60 wood beams, steel pipe diagonal bracing and HRB335 grade 25# steel bars for reinforcement. An external tension rod is added every 900mm on the side formwork for tightening. When tightening, do not use too much force, and tighten slowly and evenly to prevent damage to the side formwork that has been supported.

[0048] Then, ordinary steel bars of the ring beam are installed in the side formwork. The ordinary steel bars of the ring beam use beam stirrups as support bars and are welded and fixed to the hanging plate steel bars with binding wires or U-shaped bars. Then, slow-bonding prestressed steel strands 40 are embedded in the ordinary steel bars of the ring beam. Specifically, the slow-bonding prestressed steel strands 40 include several steel strands, externally coated with slow-bonding adhesive and plastic sleeves. The several steel strands are located in the plastic sleeves and the externally coated slow-bonding adhesive is filled between the several steel strands in the plastic sleeves. More specifically, in S3, when installing the slow-bonding prestressed steel strands 40, the slow-bonding prestressed steel strands 40 are first laid. The relevant calculations are set, and then the slow-bonding prestressed steel strand 40 is installed in the ordinary steel bar of the ring beam, and then a plastic tube is set in the side formwork along the up and down direction. The plastic tube can be a PVC tube, or a metal tube can be set in the side formwork along the up and down direction. The present invention is not limited to setting only plastic tubes. The purpose of setting the plastic tube is to form a ring beam 50 reserved hole in the ring beam 50 after the subsequent concrete pouring to form the ring beam 50. The ring beam 50 reserved hole in the ring beam 50 of the present invention can be set one or more, and the ring beam 50 reserved holes in the two adjacent layers of ring beams 50 are set correspondingly up and down;

[0049] Before installing the ring beam common steel bars and the slow-bonding prestressed steel strand 40, the axis of the installation and the control edge line must be accurately measured and placed. The steel bar installation can be carried out only after the ring beam 50 is marked to ensure the thickness of the steel bar protection layer and meet the requirements of the design and construction acceptance specifications. The steel strands of the slow-bonding prestressed steel strand 40 adopt high-strength relaxation steel strands with a strength of 1860MPa. The slow-bonding adhesive can slide freely during tensioning and is completely cured within 540 days. The surface of the plastic sleeve is provided with uneven indentations. The rib height of the slow-bonding prestressed steel strand 40 shall not be less than 1.6mm, and the rib groove depth shall not be less than 1.3mm. The slow-bonding prestressed steel strand 40 shall be prepared according to the actual size of the blanking. The length to be clamped by the jack is calculated, and the strands are cut with a grinding wheel. The strands are then numbered. They should be bundled into reels for transportation, with a reel diameter of no less than 2m. Slow-bonding prestressed steel strand 40 is a type of prestressed steel strand that has no condensation reinforcement before tensioning and has the effect of condensation reinforcement later. It combines the advantages of both prestressed steel strands. Its mechanism of action is to wrap the strands with a special slow-setting mortar, such as an external slow-bonding adhesive. This special mortar can withstand 30 days of non-setting under closed conditions, meeting the time requirements for on-site tensioning. It gradually hardens after 30 days and provides a gripping and protective effect on the strands inside.

[0050] After the plastic pipe is installed, concrete is poured in the side formwork to form the ring beam 50. Specifically, the concrete is transported by a truck pump to the glue column concrete and vibrated and compacted by an inserted vibrating pump. Before the concrete is transported to the side formwork by the truck pump in S3, it is first checked whether the ordinary steel bars of the ring beam and the slow-bonding prestressed steel strand 40 are installed. Then, the garbage and soil in the ring beam 50 formwork and the oil stains on the ordinary steel bars and the slow-bonding prestressed steel strand 40 are removed. After the concrete is poured, the ring beam 50 is formed and a ring beam 50 reserved hole is formed in the ring beam 50. All the ring beams 50 finally formed in the present invention are evenly distributed with 8 structural columns 30.

[0051] More specifically, when performing calculations related to the laying of the slow-bonding prestressed steel strand 40, the local compressive bearing capacity of the concrete should meet the following requirements according to the Code for Design of Concrete Structures (GB50010-2010):

[0052]

[0053] in, ;

[0054] In the above formula: Fl is the design value of the local load or local pressure acting on the local pressure surface;

[0055] fc is the design value of the axial compressive strength of concrete. In the verification calculation of the tensioning stage of post-tensioned prestressed concrete members, it can be determined by linear interpolation based on the concrete cube compressive strength value at the corresponding stage in accordance with the provisions of Table 4.1.4-1 of this Code;

[0056] βc is the influence coefficient of concrete strength, which shall be determined in accordance with the provisions of Article 6.3.1 of this Code;

[0057] βl is the strength improvement coefficient of concrete when it is locally compressed;

[0058] Al is the local compression area of ​​concrete;

[0059] Aln is the net area of ​​local concrete compression. For post-tensioned components, the area of ​​the duct and groove should be deducted from the local concrete compression area.

[0060] Ab is the calculated bottom area under local pressure.

[0061] The approximate tensile force of a single strand at the anchor end is: Np=1.03σconAp

[0062] In the above formula: σcon is the tension control stress;

[0063] Ap is the cross-sectional area of ​​the prestressed tendon;

[0064] S4, tensioning of the slow-bonding prestressed steel strand 40: applying prestress to both ends of the slow-bonding prestressed steel strand 40 embedded in S3 for tensioning and sealing the ends. Specifically, in S4, spiral ribs and steel pads are respectively installed at both ends of the slow-bonding prestressed steel strand 40, and the spiral ribs are welded to the steel pads. Then, a clip is installed on the outside of the steel pad of the slow-bonding prestressed steel strand 40. Then, an oil pump and a jack are taken and one end of the jack is connected to the oil pump. The other end of the jack is then installed on the outside of the clip on the slow-bonding prestressed steel strand 40 to apply prestress to the slow-bonding prestressed steel strand 40 for tensioning. The slow-bonding prestressed steel strand 40 is tensioned symmetrically in batches at both ends. After tensioning, the ends are sealed. For details, refer to Figure 5 and Figure 6In the present invention, each ring beam 50 is provided with four groups of slow-bonding prestressed steel strands 40, and two adjacent groups are connected end to end for anchoring, and the anchoring position is located at the position of the structural column 30. Each group of slow-bonding prestressed steel strands 40 includes at least two, and the anchoring positions of the two slow-bonding prestressed steel strands 40 in each group of slow-bonding prestressed steel strands 40 are staggered by 1 / 8 of the circumference of the outer wall of the central island 10. That is, after the four slow-bonding prestressed steel strands 40 located on the upper side of a ring beam 50 are connected end to end and anchored, The four slow-bonding prestressed steel strands 40 located on the lower side of the ring beam 50 are staggered by 1 / 8 of the circumference and then connected end to end for anchoring. When anchoring, steel mesh 90 is added to both ends of the slow-bonding prestressed steel strands 40 for anchoring. The steel plate used in the present invention is a 12mm*85mm*85mm steel plate, wherein the length and width are 85mm, the thickness is 12mm, and the spiral reinforcement is 4mm in diameter. The present invention is tensioned evenly and slowly during tensioning, and the ring beam should be observed in time. 50 and center island 10 cases, calculate the theoretical elongation value of the slow-bonding prestressed steel strand 40 before tensioning, record the actual elongation value of each steel strand during tensioning, when the actual elongation value exceeds the error range, such as 6% of the theoretical elongation value, stop tensioning and relax the steel strand, find out the cause and then tension. When sealing the end, that is, when sealing the end of the slow-bonding prestressed steel strand 40, first chisel and remove the residue, rinse with water, and then pour C40 fine stone concrete with 12% cement content of expansion agent into the slow-bonding prestressed steel strand. In the template for the end of the bonded prestressed steel strand 40, the thickness of the protective layer of the steel strand end is not less than 30 mm when the end is recessed, and not less than 50 mm when the tensioned end is protruding. The present invention constructs a ring beam 50 on the outer wall of the occlusal pile 20. After the ring beam 50 is constructed, the slow-bonding prestressed steel strand 40 can be tensioned, so that the ring beam 50 tightens the occlusal pile 20, giving full play to the mechanical properties of the slow-bonding prestressed steel strand 40 and the ring beam 50 made of concrete. In addition, the occlusal pile 20 is evenly stressed due to the arrangement of the ring beam 50.

[0065] Specifically, during construction, the slow-bonding prestressed steel strand 40 of the present invention needs to first check whether the plastic sleeve of the slow-bonding prestressed steel strand 40 is damaged. If damaged, it needs to be repaired with adhesive tape. Small area damage is repaired with adhesive tape, and large area damage needs to be replaced. If the steel strand is burned by electric welding or oxyacetylene gas, it also needs to be replaced. The slow-bonding prestressed steel strand 40 of the present invention needs to be kept perpendicular to the steel base plate. If it is not perpendicular, the steel base plate needs to be corrected. The slow-bonding prestressed steel strand 40 needs to be kept straight when installed in the ring beam 50 template;

[0066] When pouring the concrete of the ring beam 50 of the present invention, it is strictly forbidden to use a vibrating rod to hit the slow-bonding prestressed steel strand 40, spiral reinforcement and steel pad, etc., to prevent the plastic sleeve of the slow-bonding prestressed steel strand 40 from being scratched and the slow-bonding state of the slow-bonding prestressed steel strand 40 from being destroyed. The jack and its matching oil gauge are calibrated and a calibration report is provided. When tensioning, it is necessary to determine the oil gauge reading corresponding to the tensioning force. 24 hours after pouring the concrete of the ring beam 50, the formwork at the tensioning end of the slow-bonding prestressed steel strand 40 is removed, the steel pad and the debris on the exposed surface of the steel strand are cleared, and the excess plastic sleeve is cut off. The tensioning control stress of this application is σcon=0.75fptk, and the tensioning control force of a single steel strand Np=σconAp. When tensioning, compare the theoretical elongation value with the actual elongation value to check for abnormalities.

[0067] The tensioning procedure of the present invention is: 0→10%σcon (i.e., initial reading value)→100%σcon (i.e., reading value)→103%σcon (i.e., final reading value after holding load for 2 minutes)→0 unloading to complete automatic anchoring;

[0068] S5, second layer earthwork excavation: after the slow-bonding prestressed steel strands 40 are tensioned in S4, the excavator is used to continue excavating the foundation pit in S2 until the excavator excavates to a specific distance from the design elevation of the second layer earthwork excavation, and then manual excavation is used again to the design elevation of the second layer earthwork excavation, and then steps S3 and S4 are repeated in sequence until the total support elevation. Specifically, the ring beam 50 of the present invention is provided with multiple, that is, multiple ring beams 50 are set and cast after repeating steps S3 and S4 and repeating earthwork excavation to increase the protection of the center island 10, thereby achieving the support effect of the center island 10. During construction, the present invention can provide a circle of intercepting ditch 70 in the center island 10, and the bottom surface of the intercepting ditch 70 is lower than the top surface of the soil layer of the center island 10. When casting the center wall, multiple drainage pipes 80 can be provided to pass through the interlocking piles 20 and extend into the bottom of the intercepting ditch 70 in the center island 10 for drainage. The other end of the drainage pipe 80 does not need to be drained during subsequent construction and is therefore covered by the subsequently installed ceramic plate 13;

[0069] S6, installation of ceramic hanging panels: installing ceramic panels 13 on the outer walls of the bite piles 20 between two adjacent layers of ring beams 50. Specifically, in the S6, the ceramic panels 13 are first mounted between the two adjacent ring beams 50 at the bottom, and then mounted upwards in sequence until the ceramic panels 13 are mounted between the two adjacent ring beams 50 at the top. The front left and front right portions of the ceramic panels 13 are respectively provided with two first combination portions and two second combination portions at intervals from top to bottom. The upper first combination portion of the front left portion of the ceramic panel 13 is adapted to the upper second combination portion of the front right portion of the ceramic panel 13. The lower first combination portion of the front left portion of the ceramic panel 13 is adapted to the lower second combination portion of the front right portion of the ceramic panel 13. Plug holes are provided in the first and second combination portions. The ceramic panel 13 used in the present invention is an arc-shaped structure with a thickness of 25 mm and a height lower than the height of 10 mm between two adjacent layers of ring beams 50 for the convenience of subsequent mounting. Its width is the distance between the outermost points of adjacent bite piles 20.

[0070] The specific steps of mounting the ceramic plate 13 on the outer wall of the interlocking pile 20 between the two adjacent layers of ring beams 50 in S6 are as follows: first take the first ceramic plate 13 and the first steel bar, and then align the sockets on the two first combination parts of the first ceramic plate 13 with the ring beam 50 reserved holes of the two ring beams 50 respectively, and then insert the first steel bar from top to bottom into the ring beam 50 reserved hole of the upper ring beam 50, the socket of the first combination part of the first ceramic plate 13 located above, the socket of the first combination part of the first ceramic plate 13 located below, and the ring beam 50 reserved hole of the ring beam 50 located below, then take the second ceramic plate 13 and the second steel bar, and then make the two first combination parts of the second ceramic plate 13 fit with the two second combination parts of the first ceramic plate 13 and insert the second steel bar to fix it, and then proceed in this way until the two first combination parts of the last ceramic plate 13 are assembled with the second combination part of the penultimate ceramic plate 13 After they are together, the first steel bar is pulled out, and then the two first combination parts of the first ceramic plate 13 are adapted and assembled with the two second combination parts of the last ceramic plate 13, and the sockets of the two first combination parts of the first ceramic plate 13 and the two second combination parts of the last ceramic plate 13 are all arranged correspondingly to the reserved holes of the ring beam 50. Finally, the first steel bar is inserted into the reserved holes of the ring beam 50 on the upper side, the sockets of the first combination part of the first ceramic plate 13 located above, the sockets of the second combination part of the last ceramic plate 13 located above, the sockets of the first combination part of the first ceramic plate 13 located below, the sockets of the second combination part of the last ceramic plate 13 located below, and the reserved holes of the ring beam 50 on the lower side from top to bottom, completing the installation of the ceramic plate 13. According to the present invention, the height of the first steel bar among all the steel bars is higher than that of all the other steel bars when installing the ceramic plate 13.

[0071] Specifically, the upper first combination portion of the two first combination portions and the two second combination portions of each ceramic plate 13 can be higher than the upper second combination portion, or the lower first combination portion of the two first combination portions and the two second combination portions of each ceramic plate 13 can be higher than the lower second combination portion. The ceramic plates 13 designed in this way are convenient for sequentially connecting end to end.

[0072] Similarly, the two first combination parts and the upper first combination part of the two second combination parts of each ceramic plate 13 can be lower than the upper second combination part, or the two first combination parts and the lower first combination part of the two second combination parts of each ceramic plate 13 can be lower than the lower second combination part. The ceramic plates 13 designed in this way are convenient to be connected end to end in sequence. The present invention does not limit the specific structure of the first combination part and the second combination part of each ceramic plate 13. Any adapted first combination part and second combination part should be covered within the protection scope of the present invention. The present invention adopts the chain principle to connect multiple ceramic plates 13 arranged around the bite pile 20 end to end in sequence and then install them between the two ring beams 50, which plays a certain degree of decorative effect on the bite pile 20.

[0073] Example 2

[0074] The difference between this embodiment and embodiment 1 is that in S3, it is not necessary to install hanging plate steel bars on the outer wall of the interlocking pile 20, and the outer bottom surface of the outer wall of the interlocking pile 20 is directly used as the bottom plate. Then, a side formwork is directly assumed on the outer side of the outer wall of the interlocking pile 20, and then ordinary ring beam steel bars and pre-buried slow-bonding prestressed steel strands 40 are installed around the outer wall of the interlocking pile 20. Then, concrete is poured to form a ring beam 50. After the slow-bonding prestressed steel strands 40 are tensioned, the ring beam 50 is firmly clamped on the interlocking pile 20 and will not fall off.

[0075] This embodiment does not impose any formal restrictions on the shape, material, structure, etc. of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are within the scope of protection of the technical solution of the present invention.

Claims

1. The foundation pit annular self-locking anchor support construction method is characterized by , including the following steps: S1. Construction of interlocking piles: With the center of the central island as the center of the circle, interlocking piles are constructed at the edge of the central island for support; S2. Excavation of the first layer of earthwork: After the construction of the interlocking piles in S1 is completed, the first layer of earthwork is excavated outside the interlocking piles until it reaches the designed elevation of the first layer of earthwork excavation; S3. Ring beam construction: The ring beam is constructed on the outer wall of the interlocking pile and the slow-bonding prestressed steel strands are embedded in the ring beam; S4, tensioning of slow-bonding prestressed steel strands: applying prestress to the slow-bonding prestressed steel strands embedded in S3 for tensioning and sealing the ends; S5, second layer earthwork excavation: continue to carry out the second layer earthwork excavation outside the interlocking pile until the design elevation of the second layer earthwork excavation is reached, and then repeat steps S3 and S4 in sequence until the total support elevation is reached; S6. Ceramic panel installation: Install ceramic panels on the outer wall of the interlocking piles between two adjacent ring beams; In step S1, the pile position is firstly staked out at the edge of the center island with the center of the center island as the center of the circle, and then the guide groove is constructed. The pipe rolling machine is moved to the construction position, and the pipe rolling machine rolls the casing into the casing. After the casing is in place, the drilling machine is used and the drill rod of the drilling machine is inserted into the casing to drill a hole. After the drilling and cleaning of the hole is completed, the occlusal pile construction is carried out and the casing is pulled out after the placement is completed. In S2, the strength and quality of the interlocking piles in S1 are first checked, and then the effect of foundation pit dewatering is tested. Then, the water level of the deep well in the excavation area is measured and set. After the measurement and setting is completed, the foundation pit is positioned and laid out. First, the upper edge of the excavated foundation pit is measured, and then the position and elevation of the bottom edge of the foundation pit are measured. The excavator digs to a point 10 cm away from the design elevation of the first layer of earthwork excavation, and then manual excavation is used to reach the design elevation of the first layer of earthwork excavation. In the S3, the hanging plate steel bars are first installed on the outer wall of the occlusal pile, and then the side formwork is installed on the outer side of the outer wall of the occlusal pile. Then, a tension rod is added every 900 mm on the side formwork, and then the ring beam ordinary steel bars are installed in the side formwork. The ring beam ordinary steel bars use beam stirrups as support bars and are welded and fixed with binding wires or U-shaped bars. Then, slow-bonding prestressed steel strands are embedded in the ring beam ordinary steel bars. Then, a plastic pipe is set in the side formwork in the up and down direction. Then, concrete is transferred to the side formwork by a car pump and vibrated densely with an inserted vibrating pump to form a ring beam. The slow-bonding prestressed steel strand in S3 comprises a plurality of steel strands, an externally coated slow-bonding adhesive and a plastic sleeve, wherein the plurality of steel strands are located in the plastic sleeve and the externally coated slow-bonding adhesive is filled between the plurality of steel strands in the plastic sleeve; Before using the truck pump to transfer concrete to the side formwork in S3, first check whether the ring beam ordinary steel bars and slow-bonding prestressed steel strands are installed, and then remove the garbage and dirt in the ring beam formwork and the oil stains on the ring beam ordinary steel bars and slow-bonding prestressed steel strands; The upper end of the plastic tube is higher than or equal to the upper side of the ring beam, the lower end of the plastic tube is lower than or equal to the lower side of the ring beam, and the inner hole of the plastic tube is a reserved hole for the ring beam; In the S4, spiral reinforcement and steel plates are sequentially installed at both ends of the slow-bonding prestressed steel strand, the spiral reinforcement and the steel plates are welded, and then a clip is installed on the outer side of the steel plate of the slow-bonding prestressed steel strand. Then, an oil pump and a jack are taken and one end of the jack is connected to the oil pump. Then, the other end of the jack is installed on the outer side of the clip of the slow-bonding prestressed steel strand to apply prestress to the slow-bonding prestressed steel strand for tensioning. The slow-bonding prestressed steel strand is tensioned symmetrically at both ends in batches, and the ends are sealed after tensioning is completed. In said S6, in a bottom-up order, the ceramic plate is first mounted between the two adjacent ring beams at the bottom, and then mounted upwards in sequence until the ceramic plate is mounted between the two adjacent ring beams at the top. The front left portion and the front right portion of the ceramic plate are respectively provided with two first combination parts and two second combination parts at intervals from top to bottom. The upper first combination part of the front left portion of the ceramic plate is adapted to the upper second combination part of the front right portion of the ceramic plate, and the lower first combination part of the front left portion of the ceramic plate is adapted to the lower second combination part of the front right portion of the ceramic plate, and both the first combination part and the second combination part are provided with sockets. The specific steps of mounting the ceramic plate on the outer wall of the interlocking pile between two adjacent layers of ring beams in S6 are as follows: first take the first ceramic plate and the first steel bar, then align the two first combination parts of the first ceramic plate with the ring beam pre-set holes of the two ring beams respectively, and then insert the first steel bar from top to bottom into the ring beam pre-set hole of the ring beam on the upper side, the jack of the first combination part of the first ceramic plate located above, the jack of the first combination part of the first ceramic plate located below, and the ring beam pre-set hole of the ring beam on the lower side, then take the second ceramic plate and the second steel bar, and then make the two first combination parts of the second ceramic plate fit with the two second combination parts of the first ceramic plate and insert the second steel bar to fix it, and then proceed by analogy, until the two first combination parts of the last ceramic plate are aligned with the two second combination parts of the first ceramic plate. After the second combination parts of the second number of ceramic plates are assembled together, pull out the first steel bar, and then make the two first combination parts of the first ceramic plate and the two second combination parts of the last ceramic plate adapt and assemble, and make the sockets of the two first combination parts of the first ceramic plate and the sockets of the two second combination parts of the last ceramic plate correspond to the ring beam reserved holes above and below, and finally insert the first steel bar into the ring beam reserved hole of the upper ring beam, the socket of the first combination part of the first ceramic plate located above, the socket of the second combination part of the last ceramic plate located above, the socket of the first combination part of the first ceramic plate located below, the socket of the second combination part of the last ceramic plate located below and the ring beam reserved hole of the ring beam located below from top to bottom, completing the installation of the ceramic plates.

Images