Construction method of urban core area structure with pre-arrangement of internal support, post-removal of block and reutilization

Abstract

The application relates to the technical field of building construction, in particular to a construction method for recycling block bodies after demolishing inner supports in advance in a city core area structure, which comprises the following steps: inner support stress system conversion construction based on shear keys; structure pre-construction and inner support post-demolition construction based on a support replacement system; block body concrete technology after demolition and regeneration and truss slab floor application; the construction method for recycling block bodies after demolishing inner supports in advance in a city core area structure has the advantages that the construction efficiency can be improved, the shortage of natural sand and stone can be relieved, mass solid waste can be reduced, land can be saved, and the environment can be protected by researching the construction method for recycling block bodies after demolishing inner supports in advance in a city core area structure.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, specifically a construction method for urban core area structures where internal supports are first installed, followed by dismantling and reuse of the blocks. Background Technology

[0002] With the development and utilization of urban underground space, many deep foundation pit projects have emerged, and internal support structure systems have been widely used. However, the demolition of these systems involves many pre-construction procedures, which restricts the construction progress of basement structures. The demolition of support concrete involves large volumes, complicated processes, high costs, and low utilization rates, among other technical challenges.

[0003] In existing technologies, the traditional construction method involves removing the supports before proceeding with basement structural construction. This method is inefficient and generates a large amount of waste concrete blocks that are difficult to degrade. Currently, most of this waste is directly transported to suburban areas for landfill disposal. This approach not only occupies a large amount of land but also pollutes the soil and water, causing environmental pollution. Summary of the Invention

[0004] The purpose of this invention is to provide a construction method for reusing the structural blocks after the initial internal support of the urban core area, in order to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a construction method for reusing urban core area structures by first internally supporting them and then removing the blocks, the construction method comprising the following steps: Construction of internal support force system conversion based on shear keys; Construction based on the structural replacement system, with internal supports removed later; Post-demolition recycled block concrete technology and its application in truss slab floor decking.

[0006] Preferably, the construction of the internal support force system conversion based on shear keys includes the following steps: Construction of shear key system; Construction of rectangular shear keys; Construction of plain concrete force transfer strips.

[0007] Preferably, during construction, the shear key system is attached to the interlocking piles, force transmission bands, and raft slab. On one side of the interlocking piles, an arc-shaped shear key is formed using the natural shape of the pile body; on the other side of the raft slab, a rectangular shear key is set along with the raft slab construction; the force transmission band is set between the raft slab and the interlocking piles, located at 1 / 2 of the raft slab thickness. When constructing rectangular shear keys, rectangular shear keys are set on the periphery of 1 / 2 slab thickness of the slab at the same time as the slab construction. The width of the shear key is 300mm and the length is 250mm. The shear key is reinforced with 8C16 steel and anchored into the slab. The concrete strength grade of both the slab and the slab is C35. After the reinforcement is tied, the shear key is poured together with the slab concrete. When constructing the plain concrete force transfer strip, after the shear key and the bottom slab concrete are poured, plain concrete is first used to backfill between the support piles and the raft slab to the middle of the raft slab thickness. After the earthwork is compacted, a 400mm thick plain concrete force transfer strip with a strength grade of C40 is poured.

[0008] Preferably, the construction method based on the replacement support system, which involves structural pre-construction and internal support post-construction removal, includes the following steps: Construction of the support replacement system and dismantling of the fourth basement level; Construction of the support system on the third basement level; Construction of the support system on the second basement level; The internal support structure was removed from the interior.

[0009] Preferably, during the construction of the support replacement system and support removal for the fourth basement level, after the construction of the fourth basement level structure is completed, the exterior wall is coated with non-curing asphalt waterproof coating, modified asphalt waterproof membrane is laid, extruded polystyrene board is laid as a protective layer, stone powder is used to backfill and compact the outside of the foundation pit in layers, and then a 300mm thick C15 plain concrete force transmission strip is constructed. After the force transmission strip reaches the strength, the second inner support is removed using trestles as supports. During the construction of the support system for the third basement level, a coupler-type steel pipe scaffold is used as a support system during the reinforcement binding process of the third basement level structure. A 400×600mm horizontal support beam is installed between the lintel beam and the exterior wall at the top slab of the third basement level. Eight HRB400Φ20 main bars of the horizontal support beam are anchored into the exterior wall of the basement. At the same time, the other side of the main bars of the horizontal support is anchored into the lintel beam to ensure the formation of a reliable force transmission band. This eliminates the need for backfilling the trench in the exterior wall of the third basement level structure. During the construction of the support system on the second basement level, a coupler-type steel pipe scaffold was used as the support system during the reinforcement binding process of the third basement level structure. A 400×600mm outrigger support beam was installed between the lintel beam and the exterior wall at the top of the second basement level slab. A 200×150×6×9mm H-beam anti-overturning corbel was added to the top of the lintel beam to form a combined support system. The bottom of the outrigger was at the same elevation as the horizontal structure of the basement, and the upper part of the outrigger rested on the lintel beam. The two ends of the H-beam corbel were welded with 200×200×10mm end plates, which were tightly attached to the lintel beam and the enclosure structure. The local internal supports that collided with the columns and walls were cut off to solve the problem of structural priority. When the internal supports are removed from the interior, the replacement support system is constructed simultaneously with the structure. After the replacement support system is completed, the local internal supports that collide with the columns and walls are removed by cutting the joints. The construction of the basement floor structure is carried out until the zero level is reached. Finally, the internal supports are removed from the interior floors of the basement. This optimizes the critical path work of internal support removal, exterior wall waterproofing construction, and trench backfilling into non-critical path work, shortening the construction period of the basement structure.

[0010] Preferably, the application of post-demolition recycled block concrete technology and truss slab floor decking includes the following steps: Waste concrete crushing and screening; Magnetic sorting of recycled block concrete and recycled aggregates; Pretreatment of recycled block concrete and recycled aggregates; On-site construction of recycled concrete.

[0011] Preferably, during the crushing and screening of waste concrete, after the supporting concrete inside the foundation pit is removed, it is uniformly piled up in a designated storage area. Core samples are first taken from the waste concrete to ensure that the strength of the core sample is not lower than the original design strength. Waste concrete is initially crushed using a blasting machine, and the first screening selects recycled concrete blocks of 60-300mm. The recycled blocks are further crushed and screened a second time using an impact crusher to select coarse aggregate of 5-31.5mm. The medium-crushed and fine-crushed aggregates enter the finished product screening workshop 1, where finished coarse aggregates of 10-20mm and 20-31.5mm are screened out. Some of the finished coarse aggregates of 10-20mm and 20-31.5mm, as well as all the 5-10mm aggregates, enter the sand making conditioning stockpile. After being crushed and shaped by a vertical shaft impact crusher, they enter the finished product screening workshop 2 for screening. All aggregates larger than 10mm are returned to the sand making conditioning stockpile, forming a closed loop. Some of the excess 5-10mm aggregates are also returned to the sand making conditioning stockpile, forming a closed loop. During the magnetic separation of recycled block concrete and recycled aggregates, the recycled aggregates are subjected to both magnetic and mechanical forces when passing through the magnetic field of the magnetic separator. The magnetic force on the stronger magnetic aggregates is greater than the mechanical force, while the magnetic force on the non-magnetic aggregate particles is very small, so the mechanical force is dominant. Since the resultant forces of magnetic and mechanical forces acting on various aggregates are different, their trajectories are also different, thus achieving the final separation of aggregates. During the pretreatment of recycled block concrete and recycled aggregates, waste concrete is crushed into recycled blocks. Compared to natural aggregates, most recycled coarse aggregates have rougher surfaces and more surface mortar. Pre-treating the recycled coarse aggregates can better ensure the quality of the recycled concrete. Before construction, the processed concrete blocks are cleaned, transported to the vicinity of the formwork for the test specimen using a small material hoist or tower crane hopper, and thoroughly moistened with clean water. During on-site construction of recycled concrete, the concrete demolition components are stripped of their protective layer and reinforcing steel, and then broken into larger blocks according to project requirements, either manually or mechanically: concrete blocks for recycled mixed concrete columns with a characteristic size of 70–100 mm; concrete blocks for recycled mixed reinforced concrete beams with a characteristic size of 60–100 mm; concrete blocks for recycled mixed reinforced concrete slabs with a characteristic size of 50–60 mm; and concrete blocks for recycled mixed reinforced concrete ring beams.

[0012] Preferably, the extruded polystyrene board includes an extruded polystyrene board body, an assembly groove is formed on the surface of the extruded polystyrene board body, and an assembly plate is integrally formed on the surface of the extruded polystyrene board body. The assembly groove and the assembly plate are symmetrically distributed about the center of the extruded polystyrene board body, and the dimensions of the assembly groove and the assembly plate are matched. Side grooves are formed on the two parallel side walls of the assembly groove. A rubber clamp is fixed inside the side groove. The rubber clamp has an arc-shaped plate structure and protrudes from the side groove.

[0013] Preferably, the surface of the assembly groove is fixed with multiple connecting protrusions, the top of the connecting protrusions is fixed with a rubber ball, the bottom surface of the assembly plate is provided with an inlet groove, the surface of the inlet groove is provided with a slot, the slot is a spherical groove, the diameter of the slot is larger than the opening of the inlet groove, and the size of the slot matches the size of the rubber ball, and the size of the connecting protrusion matches the size of the inlet groove.

[0014] Compared with the prior art, the beneficial effects of the present invention are: The construction method proposed in this invention, which involves first internally supporting the structure in the urban core area and then dismantling and reusing the blocks, can improve construction efficiency, alleviate the shortage of natural sand and gravel, reduce the emission of large quantities of solid waste, save land, and protect the environment. Attached Figure Description

[0015] Figure 1 This is a flowchart of the method of the present invention; Figure 2 This is a schematic diagram of the extruded polystyrene board body structure of the present invention; Figure 3 for Figure 2 Enlarged schematic diagram of the structure at point A in the middle; Figure 4 This is a schematic diagram of the bottom structure of the extruded polystyrene board body of the present invention; Figure 5 This is a schematic diagram of the half-section structure of the extruded polystyrene board body at the corner of the present invention; Figure 6 for Figure 5 Enlarged schematic diagram of the structure at point B In the diagram: 1. Extruded polystyrene board body; 2. Assembly groove; 3. Assembly board; 4. Side groove; 5. Rubber clamp block; 6. Connecting protrusion; 7. Rubber ball; 8. Inlet groove; 9. Slot. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the present invention clear and complete, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only some, not all, embodiments of the present invention, and are merely illustrative of the embodiments of the present invention. They are not intended to limit the embodiments of the present invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Example 1: Please refer to Figure 1 This invention provides a technical solution: a construction method for reusing urban core area structures by first internally supporting them and then removing the blocks. The construction method includes the following steps: Construction of internal support force system conversion based on shear keys; Construction based on the structural replacement system, with internal supports removed later; Post-demolition recycled block concrete technology and its application in truss slab floor decking.

[0018] 1. Internal support force conversion technology based on shear keys: (1) Shear key system composition: The shear key system is attached to the interlocking piles, force transmission bands, and raft slab. On the side of the interlocking piles, an arc-shaped shear key is formed by utilizing the natural shape of the pile body; on the side of the raft slab, a rectangular shear key is set along with the raft slab construction; the force transmission band is set between the raft slab and the interlocking piles, located at 1 / 2 of the raft slab thickness.

[0019] (2) Construction of rectangular shear keys During the construction of the base slab, rectangular shear keys are set around the perimeter of the base slab (1 / 2 slab thickness). The width of the shear keys is 300mm and the length is 250mm. The shear keys are reinforced with 8C16 steel and anchored into the base slab. The concrete strength grade of the shear keys is the same as that of the base slab concrete, which is C35. After the reinforcement is tied, the shear keys are poured together with the base slab concrete.

[0020] (3) Construction of plain concrete force transfer strip After the shear key and the bottom slab concrete are poured, plain concrete is first used to backfill between the support piles and the raft slab up to the middle of the raft slab thickness. After the earthwork is compacted, a 400mm thick plain concrete force transfer strip with a strength grade of C40 is poured.

[0021] 2. Construction technology based on the replacement support system: structural first, internal support later removal. (1) Construction of the support replacement system and support removal on the fourth basement level After the construction of the fourth basement level was completed, non-curing asphalt waterproof coating was applied to the exterior walls, modified asphalt waterproof membrane was laid, extruded polystyrene board was laid as a protective layer, stone powder was used to backfill and compact the outside of the foundation pit in layers, and then a 300mm thick C15 plain concrete force transmission strip was constructed. After the force transmission strip reached the required strength, the second inner support was removed using trestles as supports.

[0022] (2) Construction of the third basement level support system: During the reinforcement binding process of the third basement level structure, a coupler-type steel pipe scaffold is used as a support system. A 400×600mm horizontal support beam is installed between the lintel beam and the exterior wall at the top slab of the third basement level. The main reinforcement bars of the horizontal support beam (8 HRB400Φ20 bars) are anchored into the exterior wall of the basement. At the same time, the other side of the main reinforcement bars of the horizontal support beam is anchored into the lintel beam to ensure the formation of a reliable force transmission band. This eliminates the need for backfilling the trench in the exterior wall of the third basement level structure.

[0023] (3) Construction of the support system on the second basement level During the reinforcement binding process of the third basement level structure, a coupler-type steel pipe scaffold was used as the support system. A 400×600mm outrigger replacement beam was installed between the lintel beam and the exterior wall at the top of the second basement level. A 200×150×6×9mm H-beam anti-overturning bracket was added to the top of the lintel beam to form a combined replacement support system. The bottom of the outrigger was at the same elevation as the horizontal structure of the basement, and the upper part of the outrigger rested on the lintel beam. The two ends of the H-beam bracket were welded with end plates (200×200×10mm) and tightly attached to the lintel beam and the enclosure structure. The local internal supports that collided with the columns and walls were cut off to solve the problem of structural priority.

[0024] (4) Removal of internal supports The replacement support system is constructed simultaneously with the structure. After the replacement support system is completed, the internal supports that collide with columns and walls (especially exterior walls) are dismantled. The construction of the basement structure is carried out from the ground floor to the top floor. Finally, the internal supports are removed on the interior floors of the basement. This optimizes the critical path tasks of internal support removal, exterior wall waterproofing construction, and trench backfilling into non-critical path tasks, shortening the construction period of the basement structure.

[0025] 2. Application of recycled block concrete after demolition in reinforced truss floor slabs: (1) Crushing and screening of waste concrete After the concrete supporting the foundation pit is removed, it is uniformly piled up in the designated storage area. Core samples are first taken from the waste concrete to ensure that the core sample strength is not lower than the original design strength. The waste concrete is initially crushed using a blasting machine, and the first screening selects recycled concrete blocks of 60~300mm. The recycled blocks are then further crushed and screened a second time using an impact crusher to select coarse aggregate of 5~31.5mm.

[0026] The medium-crushed and fine-crushed aggregates enter the finished product screening workshop 1, where they are screened to separate finished coarse aggregates of 10-20mm and 20-31.5mm. A portion of the 10-20mm and 20-31.5mm finished coarse aggregates, along with all the 5-10mm aggregates, enters the sand-making conditioning stockpile. After being crushed and shaped by a vertical shaft impact crusher, the aggregates enter the finished product screening workshop 2 for further screening. All aggregates larger than 10mm are returned to the sand-making conditioning stockpile, forming a closed-loop cycle. The excess 5-10mm aggregates are also returned to the sand-making conditioning stockpile, forming a closed-loop cycle.

[0027] (2) Magnetic sorting of recycled block concrete and recycled aggregate When recycled aggregates pass through the magnetic field of a magnetic separator, they are simultaneously subjected to magnetic force and mechanical force (gravity, centrifugal force, medium resistance, friction, etc.). The magnetic force on strongly magnetic aggregates is greater than the mechanical force, while the magnetic force on non-magnetic aggregate particles is very small, so mechanical force dominates. Because the resultant forces of magnetic and mechanical forces acting on various aggregates are different, their trajectories also differ, thus achieving the final separation of the aggregates. For magnetic aggregate particles to be successfully separated, the necessary condition is that the magnetic force on each magnetic aggregate particle must be greater than the resultant force of the mechanical force acting in the opposite direction.

[0028] (3) Pretreatment of recycled block concrete and recycled aggregate Waste concrete is broken down into recycled blocks. Compared to natural aggregates, most recycled coarse aggregates have rougher surfaces and more surface mortar. During the mechanical extrusion of waste concrete, varying degrees of damage occur to the aggregates, resulting in numerous micro-cracks and small pores within the recycled aggregates. This detailed damage to the recycled blocks is extremely detrimental to the mix design of recycled concrete. To improve the quality of recycled concrete, pretreatment of the recycled aggregates is essential. Pretreatment of recycled aggregates can be achieved through two main methods: wetting and slurry impregnation. Wetting involves saturating the recycled aggregates with water, allowing them to surface dry naturally, and then mixing them with the designed mix proportions or pouring them with new concrete, followed by vibration and pouring. Slurry impregnation involves coating the recycled aggregates with a cement paste of equal water-cement ratio to repair damaged areas of the recycled blocks. Pre-treating the recycled coarse aggregates ensures better quality control of the recycled concrete. Before construction, clean the processed concrete blocks, transport them to the vicinity of the template to be poured using a small material hoist or tower crane hopper, and thoroughly wet them with clean water.

[0029] (4) On-site construction of recycled concrete The concrete demolition components are stripped of their protective layer and reinforcing steel, and then broken into larger blocks as required by the project, either manually or mechanically: concrete blocks for recycled mixed concrete columns (characteristic size 70–100 mm); concrete blocks for recycled mixed reinforced concrete beams (characteristic size 60–100 mm); concrete blocks for recycled mixed reinforced concrete slabs (characteristic size 50–60 mm); and concrete blocks for recycled mixed reinforced concrete ring beams (characteristic size 60–80 mm).

[0030] 1) When pouring the beam, first pour a layer of 20-30 mm new concrete at the bottom of the beam formwork. Then, evenly pour half of the total replacement concrete volume into the formwork, pour an appropriate amount of new concrete, so that the beam pouring height is about 350 mm. Use a vibrator to mechanically vibrate the mixture of new and old concrete. Then, evenly pour the other half of the concrete block into the formwork, pour new concrete to the design height of the beam, and mechanically vibrate the mixture of new and old concrete to ensure the compactness of the recycled reinforced concrete beam.

[0031] 2) For the construction of truss floor decks, simply place the pre-allocated recycled concrete blocks for the floor decks evenly inside the formwork of the truss floor decks. The pouring of the floor decks is the same as the normal pouring method, but vibration must be strengthened to ensure that the waste concrete blocks and new concrete are fully mixed.

[0032] 3) When pouring the column, first pour a 20-30 mm thick layer of cast-in-place concrete at the bottom of the column formwork. Then, alternately pour the new and old concrete into the formwork and vibrate it thoroughly. Each filling height should be controlled at 400-500 mm until the design elevation is reached.

[0033] 4) The ring beam is constructed using recycled concrete blocks. The stirrups and longitudinal bars within the ring beam are tied into a reinforcing cage. Waste concrete blocks are placed inside the reinforcing cage, and ordinary concrete is used to encase both the waste concrete blocks and the reinforcing cage. The method for constructing the recycled concrete block segments is as follows: first, the longitudinal bars and stirrups are tied to form a reinforcing cage. The reinforcing cage is placed inside the formwork. Then, recycled concrete blocks are placed inside the reinforcing cage according to the recycled block replacement rate, and finally, recycled concrete is poured.

[0034] This invention employs a "combined support system" technical measure to achieve structural pre-construction followed by demolition, providing a new approach for various deep foundation pit projects both domestically and internationally. Through the application of innovative technologies, the basement construction period was shortened by about 35 days. At the same time, through the implementation of key technologies for recycled block concrete in the project's support beams, recycled block concrete has the advantage of lower production costs compared to recycled aggregate concrete. According to surveys, energy consumption can be saved by 40% to 60% during the crushing of waste concrete, and cement consumption can be saved by 30% when preparing concrete.

[0035] Example 2: Refer to Appendix Figures 2 to 6 The extruded polystyrene board includes an extruded polystyrene board body 1, an assembly groove 2 on the surface of the extruded polystyrene board body 1, and an assembly plate 3 integrally formed on the surface of the extruded polystyrene board body 1. The assembly groove 2 and the assembly plate 3 are symmetrically distributed about the center of the extruded polystyrene board body 1, and the dimensions of the assembly groove 2 and the assembly plate 3 are matched. Side grooves 4 are provided on the two parallel side walls of the assembly groove 2. Rubber clamps 5 are fixed inside the side grooves 4. The rubber clamps 5 have an arc-shaped plate structure and protrude from the side grooves 4. Multiple connecting protrusions 6 are fixed on the surface of the assembly groove 2. Rubber retaining balls 7 are fixed on the top of the connecting protrusions 6. An inlet groove 8 is provided on the bottom surface of the assembly plate 3. A retaining groove 9 is provided on the surface of the inlet groove 8. The retaining groove 9 is a spherical groove. The diameter of the retaining groove 9 is larger than the diameter of the inlet groove 8, and the size of the retaining groove 9 matches the size of the rubber retaining balls 7. The size of the connecting protrusions 6 matches the size of the inlet groove 8. When assembling two extruded polystyrene board bodies 1, the two sets of extruded polystyrene board bodies 1 are assembled by pushing the assembly plate 3 into the assembly groove 2. During this process, the rubber ball 7 passes through the guide groove 8 and is pushed into the slot 9, and the rubber clamp 5 is squeezed between the assembly groove 2 and the assembly plate 3, thus preventing the assembly plate 3 from falling off the assembly groove 2.

[0036] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A construction method for urban core area structures involving initial internal bracing followed by dismantling and reuse of the blocks, characterized in that... The construction method includes the following steps: Construction of internal support force system conversion based on shear keys; Construction based on the structural replacement system, with internal supports removed later; Post-demolition recycled block concrete technology and its application in truss slab floor decking; The construction of the internal support system transformation based on shear keys includes the following steps: Construction of shear key system; Construction of rectangular shear keys; Construction of plain concrete force transfer strips; During construction, the shear key system is attached to the interlocking piles, force transmission bands, and raft slab. On one side of the interlocking piles, an arc-shaped shear key is formed using the natural shape of the pile. On the other side of the raft slab, a rectangular shear key is installed along with the raft slab construction. The force transmission band is set between the raft slab and the interlocking piles, located at 1 / 2 of the raft slab thickness. When constructing rectangular shear keys, rectangular shear keys are set on the periphery of 1 / 2 slab thickness of the slab at the same time as the slab construction. The width of the shear key is 300mm and the length is 250mm. The shear key is reinforced with 8C16 steel and anchored into the slab. The concrete strength grade of both the slab and the slab is C35. After the reinforcement is tied, the shear key is poured together with the slab concrete. When constructing the plain concrete force transfer strip, after the shear key and the bottom slab concrete are poured, plain concrete is first used to backfill between the support piles and the raft slab to the middle of the raft slab thickness. After the earthwork is compacted, a 400mm thick plain concrete force transfer strip with a strength grade of C40 is poured. The construction method based on the replacement support system, which involves structural pre-construction and internal support post-removal, includes the following steps: Construction of the support replacement system and dismantling of the fourth basement level; Construction of the support system on the third basement level; Construction of the support system on the second basement level; The internal support structure was removed from the interior. During the construction of the support replacement system and support removal on the fourth basement level, after the construction of the fourth basement level structure is completed, apply non-curing asphalt waterproof coating to the exterior wall, lay modified asphalt waterproof membrane, lay extruded polystyrene board as a protective layer, backfill and compact the outside of the foundation pit in layers with stone powder, and then construct a 300mm thick C15 plain concrete force transmission strip. After the force transmission strip reaches the strength, use trestles as supports to remove the second inner support. During the construction of the support system for the third basement level, a coupler-type steel pipe scaffold is used as a support system during the reinforcement binding process of the third basement level structure. A 400×600mm horizontal support beam is installed between the lintel beam and the exterior wall at the top slab of the third basement level. Eight HRB400Φ20 main bars of the horizontal support beam are anchored into the exterior wall of the basement. At the same time, the other side of the main bars of the horizontal support is anchored into the lintel beam to ensure the formation of a reliable force transmission band. This eliminates the need for backfilling the trench in the exterior wall of the third basement level structure. During the construction of the support system on the second basement level, a coupler-type steel pipe scaffold was used as the support system during the reinforcement binding process of the third basement level structure. A 400×600mm outrigger support beam was installed between the lintel beam and the exterior wall at the top of the second basement level slab. A 200×150×6×9mm H-beam anti-overturning corbel was added to the top of the lintel beam to form a combined support system. The bottom of the outrigger was at the same elevation as the horizontal structure of the basement, and the upper part of the outrigger rested on the lintel beam. The two ends of the H-beam corbel were welded with 200×200×10mm end plates, which were tightly attached to the lintel beam and the enclosure structure. The local internal supports that collided with the columns and walls were cut off to solve the problem of structural priority. When the internal supports are removed from the interior, the replacement support system is constructed simultaneously with the structure. After the replacement support system is completed, the local internal supports that collide with the columns and walls are removed by cutting the joints. The construction of the basement floor structure is carried out until the zero level is reached. Finally, the internal supports are removed from the interior floors of the basement. This optimizes the critical path work of internal support removal, exterior wall waterproofing construction, and trench backfilling into non-critical path work, shortening the construction period of the basement structure.

2. The construction method for the urban core area structure of which involves initial internal support followed by dismantling and reuse of the blocks, as described in claim 1, is characterized in that: The application of post-demolition recycled block concrete technology and truss slab floor decking includes the following steps: Waste concrete crushing and screening; Magnetic sorting of recycled block concrete and recycled aggregates; Pretreatment of recycled block concrete and recycled aggregates; On-site construction of recycled concrete.

3. The construction method for the urban core area structure of which involves initial internal support followed by dismantling and reuse of the blocks, as described in claim 2, is characterized in that: During the crushing and screening of waste concrete, after the concrete supporting the foundation pit is removed, it is uniformly piled up in the designated storage area. Core samples are first taken from the waste concrete to ensure that the core sample strength is not lower than the original design strength. The waste concrete is initially crushed using a blasting machine and screened for the first time to select recycled block concrete of 60~300mm. The recycled blocks are further crushed and screened a second time using an impact crusher to select coarse aggregate of 5~31.5mm. The medium-crushed aggregate and the fine-crushed aggregate enter the finished product 1 screening workshop to screen out finished coarse aggregate of 10~20mm and 20~31.5mm. Some of the finished coarse aggregate of 10~20mm and 20~31.5mm and all of the 5~10mm aggregate enter the sand making and conditioning stockpile. After being crushed and shaped by a vertical shaft impact crusher, it enters the finished product 2 screening workshop for screening. All aggregate larger than 10mm is returned to the sand making and conditioning stockpile to form a closed loop. Some of the excess 5~10mm aggregate is returned to the sand making and conditioning stockpile to form a closed loop. During the magnetic separation of recycled block concrete and recycled aggregates, the recycled aggregates are subjected to both magnetic and mechanical forces when passing through the magnetic field of the magnetic separator. The magnetic force on the stronger magnetic aggregates is greater than the mechanical force, while the magnetic force on the non-magnetic aggregate particles is very small, so the mechanical force is dominant. Since the resultant forces of magnetic and mechanical forces acting on various aggregates are different, their trajectories are also different, thus achieving the final separation of aggregates. During the pretreatment of recycled block concrete and recycled aggregates, waste concrete is crushed into recycled blocks. Compared with natural aggregates, most recycled coarse aggregates have a rougher surface and more surface mortar. By pretreating the recycled coarse aggregates, the quality of recycled concrete can be better guaranteed. Before construction, the processed concrete blocks are cleaned and transported to the vicinity of the template to be poured using a small material hoist or tower crane bucket, and then thoroughly moistened with clean water. During on-site construction of recycled concrete, the concrete demolition components are stripped of their protective layer and reinforcing steel, and then broken into larger blocks according to project requirements, either manually or mechanically: concrete blocks for recycled mixed concrete columns with a characteristic size of 70–100 mm; concrete blocks for recycled mixed reinforced concrete beams with a characteristic size of 60–100 mm; concrete blocks for recycled mixed reinforced concrete slabs with a characteristic size of 50–60 mm; and concrete blocks for recycled mixed reinforced concrete ring beams.

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