Reinforced concrete supporting structure for applying prestress

Abstract

The reinforced concrete supporting structure comprises at least one layer of horizontal support, each layer of horizontal support at least comprises a horizontal beam with two structural sections, and each structural section at least comprises two main supporting beams which are parallel to each other and extend in the extending direction of the horizontal beam. The adjacent main supporting beams of the same structural section are connected together through straight connecting rods. The structural sections are sequentially connected and connected into a whole through the post-pouring main supporting beam, the post-pouring main supporting beam is constructed after prestress is applied to the structural sections, and each structural section is of a reinforced concrete structure. The horizontal beam is divided into at least two structural sections, the structural sections are connected into a whole after prestress is applied to the structural sections, the complete horizontal beam is formed, and the problems that an existing reinforced concrete supporting structure can only passively resist the external soil pressure of a foundation pit and the foundation pit is large in deformation due to the fact that no prestress exists are smoothly solved; and the safety of foundation pit construction is improved.

Description

Technical Field

[0001] The utility model relates to a prestressed reinforced concrete support structure. Background Art

[0002] During foundation pit construction, supports are often erected to ensure the stability of the foundation pit side walls, avoid safety accidents caused by foundation pit collapse, and affect the construction progress. The supports are mainly horizontal supports, which are generally divided into two types: reinforced concrete structures and steel structures. The steel structures are mainly used in small foundation pits. Due to the advantages of large support stiffness, safety and reliability, simple construction, and no limitation by the shape of the foundation pit, the reinforced concrete support structure is often used in large foundation pits. However, since the reinforced concrete support structure is constructed by integral in-situ casting, if the earth pressure changes outside the foundation pit after construction, prestress cannot be applied to the reinforced concrete support, resulting in that the reinforced concrete support structure can only passively resist the earth pressure outside the foundation pit. That is, after the foundation pit side wall inclines and deforms inward, the reinforced concrete support structure can really play a supporting role. However, after the foundation pit side wall inclines and deforms, a collapse trend has been generated in the foundation pit side wall, posing a certain danger to the safety of the foundation pit. Therefore, how to improve the safety of the reinforced concrete support structure becomes necessary. Summary of the Utility Model

[0003] To solve the problem in the prior art that the prestress cannot be applied to the reinforced concrete support structure, and it can only passively resist the earth pressure outside the foundation pit, resulting in large deformation of the foundation pit and being difficult to control, the present application discloses a prestressed reinforced concrete support structure, which includes at least one layer of horizontal support. Each layer of horizontal support includes at least one horizontal beam. At least one horizontal beam includes at least two structural segments. Each structural segment includes at least two main support beams that are parallel to each other and extend along the extension direction of the horizontal beam. The adjacent main support beams in the same structural segment are connected together by a straight connecting rod, and the straight connecting rod is perpendicular to the main support beam. The structural segments of the same horizontal beam are connected in sequence and connected into one body by a post-cast main support beam. The post-cast main support beam is constructed after the prestress is applied to the structural segments. Each structural segment is a reinforced concrete structure.

[0004] In this application, the horizontal beam is segmented to form at least two structural segments. After prestress is applied to each structural segment, it is then connected into one piece by the post-cast main support beam to form a complete horizontal beam. This application successfully solves the problem that the existing reinforced concrete support structure can only passively resist the external soil pressure of the foundation pit due to the absence of prestress, resulting in large deformation of the foundation pit. After prestress is applied to the horizontal beam, the horizontal beam can actively resist the external soil pressure of the foundation pit. During the process of applying prestress to each structural segment, the side wall of the foundation pit will tilt towards the outside of the foundation pit and undergo compressive deformation. When the side wall of the foundation pit tilts towards the inside of the foundation pit under the push of the external soil pressure, due to the existence of prestress, the horizontal deformation of the side wall of the foundation pit can be reduced, improving the safety of the foundation pit construction.

[0005] Furthermore, to facilitate the jacking of each structural segment to smoothly apply prestress, in the same horizontal beam, a loading cross beam is provided on one side of each structural segment facing another structural segment. The jack can be arranged between two relatively arranged loading cross beams to jack and press adjacent two structural segments, so that the structural segments generate prestress. The loading cross beam can connect each main support beam into a whole, facilitating the uniform jacking of each main support beam and enabling each main support beam to generate relatively uniform deformation.

[0006] Specifically, to ensure the strength of the post-cast main support beam, the main reinforcement bars in the post-cast main support beam are connected to the main reinforcement bars in the adjacent two structural segments.

[0007] Specifically, each structural segment is supported on a support column. At least corresponding to one support column, a column hole is reserved on the structural segment. The part of the support column exceeding the set bottom surface of the foundation pit upwards is a steel column, and the steel column can be freely inserted into the corresponding column hole. When prestress is applied to the structural segment, there is no contact between the edge of the column hole and the steel column; after the prestress application to the structural segment is completed, concrete is poured into the column hole to connect the steel column and the structural segment into one piece. The steel column and the structural segment are connected into one piece by the concrete in the column hole, making the support column and the horizontal beam connected into a whole to ensure that the horizontal beam has strong stability during the construction of the foundation pit and the underground structure. During the construction of the foundation pit and the underground structure, under the thrust of the external soil mass, the side wall of the foundation pit will gradually tilt towards the inside of the foundation pit and apply pressure to the horizontal beam. Under the external pressure, the horizontal beam has a tendency to bend in the vertical direction. The concrete in the column hole is used to fix the horizontal beam on the support column, and the support column is used to improve the stability of the horizontal beam, thus ensuring the safety of the foundation pit.

[0008] Furthermore, to ensure the strength of the opening area, when pouring concrete into the column hole, first restore the main reinforcement bars in the column hole, and then pour the concrete. The main reinforcement bars in the column hole are connected to the main reinforcement bars in the structural section and the steel column. After connecting the main reinforcement bars in the column hole to the steel column, the connection strength between the steel column and the horizontal beam can also be improved, ensuring the stability of their connection.

[0009] Furthermore, to prevent the structural section from bending upward or downward during the prestressing process, an upper limit member and a lower limit member are fixedly installed on the steel column. The upper limit member is located on the upper side of the structural section, and the lower limit member is located on the lower side of the structural section. The structural section is slidably supported on the lower limit member. There is a gap of 0 - 2 mm between the upper limit member and the structural section, and at least one side of the upper limit member extends beyond the edge of the column hole.

[0010] To ensure that the structural section can slide along the lower limit member during the prestressing process, before pouring the concrete of the structural section, an isolation layer needs to be set on the lower limit member. The isolation layer can be isolation paint or an isolation cloth laid. The isolation cloth can be made of materials such as geotextile or plastic film.

[0011] According to the convenience of construction or other requirements, the upper limit member can be installed before pouring the concrete of the structural section, or it can be installed after the structural section reaches the set strength and before applying the prestress. When the upper limit member is installed before pouring the concrete, an isolation layer needs to be applied to the lower surface of the upper limit member by painting isolation paint or wrapping materials such as geotextile or plastic film to avoid too high a bonding strength between the concrete and the upper limit member, which may cause the support column to tilt when applying the prestress. No matter which installation method is adopted for the upper limit member, its lower surface is not recommended to be in contact with the structural section, and it is preferably provided with a gap of 0.5 - 2 mm. This is because when the upper limit member is in contact with the structural section, due to the errors in actual construction, the upper limit member sometimes presses tightly against the structural section, affecting the application of the prestress.

[0012] Furthermore, before applying the prestress, no diagonal connecting rods are provided between adjacent main support beams of the same structural section. A diagonal connecting rod refers to a connecting member that is connected between two adjacent main support beams and is inclined relative to the main support beam. In the existing conventional designs, straight connecting rods and diagonal connecting rods are provided between the main support beams. The main support beam, the straight connecting rod, and the diagonal connecting rod form a triangular frame structure to improve the structural stability of the horizontal beam. However, in this application, if diagonal connecting rods are provided, secondary stresses will be generated on the diagonal connecting rods during the prestressing process. These secondary stresses will generate thrusts in opposite directions on the two connected main support beams, having a tendency to cause the horizontal beam to twist and deform, increasing the instability of the horizontal beam and being unfavorable for the safe construction of the foundation pit.

[0013] Further, in the same horizontal beam, the main support beams of each structural segment correspond one by one, and the post-cast main support beam corresponds one by one to the main support beam of the connected structural segment. The corresponding main support beam and post-cast main support beam extend along the same straight line. This design can keep the main support beams of each structural segment extending straight, so that the external pressure can be transmitted along the main support beam to stably resist the external pressure. When the post-cast main support beam is offset relative to the main support beam, a component force will be generated at the connection point between the post-cast main support beam and the structural segment, affecting the overall stability of the horizontal beam.

[0014] The beneficial effects of this application are summarized as follows: 1. After prestress is applied, the reinforced concrete support structure has high stiffness and can effectively control the horizontal displacement of the foundation pit; 2. The prestress application is simple and efficient; 3. During the prestress application process, no secondary internal force will be generated on the support members, and the structural safety is high; 4. Compared with the traditional reinforced concrete support structure without prestress, the cross-section of the reinforced concrete support structure in this application is small, the consumption of steel bars and concrete materials is small, and the cost is saved by 10-20%.

[0015] According to the different numbers of horizontal supports, different construction methods are adopted when constructing the reinforced concrete support structure in this application. When the reinforced concrete support structure only includes one layer of horizontal support, its construction method includes the following steps:

[0016] (1) Construct a retaining wall at the set edge of the foundation pit, then construct a capping beam on the top of the retaining wall, and construct support columns in the foundation pit area. The part of the support column that extends upward beyond the set bottom surface of the foundation pit is a steel column;

[0017] (2) Construct the first layer of horizontal support: cast-in-place the structural segments of each horizontal beam of the first layer of horizontal support, and reserve column holes on the structural segments. The column holes surround the outer circumference of the steel column. When the strength of the structural segments of the same horizontal beam reaches the set strength, install jacks between adjacent structural segments of the same horizontal beam, and then jack the structural segments to make the structural segments produce prestress; after completing the jacking of the structural segments, construct a post-cast main support beam between adjacent structural segments to connect adjacent structural segments together through the post-cast main support beam; complete the construction of each horizontal beam of the first layer of horizontal support;

[0018] (3) Complete the excavation of the foundation pit.

[0019] When the reinforced concrete support structure includes at least two layers of horizontal support, its construction method includes the following steps:

[0020] (1) Construct a retaining wall at the set edge of the foundation pit, then construct a capping beam on the top of the retaining wall, and construct support columns in the foundation pit area. The part of the support column that extends upward beyond the set bottom surface of the foundation pit is a steel column;

[0021] (2) Construct the first - layer horizontal support: Cast the structural segments of each horizontal beam of the first - layer horizontal support, and reserve column holes on the structural segments. The column holes surround the outer periphery of the steel columns. When the strength of the structural segments of the same horizontal beam reaches the set strength, install jacks between two adjacent structural segments of the same horizontal beam, and then jack - press the structural segments to produce prestress in the structural segments. After completing the jack - pressing of the structural segments, construct the post - cast main support beam between two adjacent structural segments to connect the two adjacent structural segments together through the post - cast main support beam. Complete the construction of each horizontal beam of the first - layer horizontal support;

[0022] (3) Excavate the foundation pit. When reaching the construction elevation of the second - layer horizontal support, suspend the excavation of the foundation pit;

[0023] (4) Construct the second - layer horizontal support: Cast the structural segments of each horizontal beam of the second - layer horizontal support, and reserve column holes on the structural segments. The column holes surround the outer periphery of the steel columns. When the strength of the structural segments of the same horizontal beam reaches the set strength, install jacks between two adjacent structural segments of the same horizontal beam, and then jack - press the structural segments to produce prestress in the structural segments. After completing the jack - pressing of the structural segments, construct the post - cast main support beam between two adjacent structural segments to connect the two adjacent structural segments together through the post - cast main support beam. Complete the construction of each horizontal beam of the second - layer horizontal support;

[0024] (5) When only two layers of horizontal supports are included, complete the excavation of the foundation pit;

[0025] When at least three layers of horizontal supports are included, repeat steps (3) and (4) until the construction of all horizontal beams of the horizontal supports is completed, and then complete the excavation of the foundation pit.

[0026] When the same - layer horizontal support includes at least two horizontal beams, the order of applying prestress to each horizontal beam of the same - layer horizontal support is not specified as to whether it is first or second. It can be carried out synchronously or step - by - step in sequence.

[0027] When the same horizontal beam includes at least three structural segments, the jacks between the structural segments work synchronously when prestress is applied. When the length of the horizontal beam is too long, more than three structural segments will be set so that each structural segment can generate approximately the same prestress, enabling each structural segment to produce corresponding deformation. The length of a single structural segment is controlled between 25 - 30 meters. Therefore, when the length of the horizontal beam exceeds 60 meters, more than three structural segments need to be set. This is because each structural segment needs to be supported on the lower limit member of the support column. During the prestress application process, the structural segment will inevitably generate friction with the lower limit member, affecting the uniform deformation inside the structural segment. The longer the structural segment, the worse its deformation uniformity, and the farther it is from the prestress application segment, the smaller its deformation. However, after the prestress application is completed, the deformation inside each structural segment will gradually equalize to achieve deformation uniformity. Since in the prestress application process, some areas cannot deform sufficiently, during the subsequent equalization process, the prestress will correspondingly become smaller, reducing the effect of prestress application. Brief Description of the Drawings

[0028] Figure 1 is a schematic structural diagram of an embodiment of the reinforced concrete support structure in this application.

[0029] Figure 2 is Figure 1 an enlarged view of part A in

[0030] Figure 3 is Figure 2 a view in the B - B direction in

[0031] Figure 4 is Figure 3 a schematic diagram of the column hole after pouring in the shown drawings.

[0032] Figure 5 is the first layout sketch of the main reinforcement bars in the column hole.

[0033] Figure 6 is the second layout sketch of the main reinforcement bars in the column hole.

[0034] Figure 7 is the third layout sketch of the main reinforcement bars in the column hole.

[0035] Figure 8 is the layout sketch of the main reinforcement bars in the post - cast main support beam when the post - cast main support beam adopts a reinforced concrete structure.

[0036] Figure 9 is the structural sketch when prestress is applied to the first horizontal beam.

[0037] Figure 10 is the structural sketch when prestress is applied to the second horizontal beam.

[0038] Figure 11 It is a structural schematic diagram after the foundation pit excavation is completed.

[0039] Figure 12 It is a structural schematic diagram of the horizontal support in a foundation pit.

[0040] Figure 13 It is a structural schematic diagram of the horizontal support in another foundation pit. Specific implementation manners

[0041] The prestressed reinforced concrete support structure in the present application will be described below.

[0042] Please refer to Figures 1 - 8 , Figure 1 In it, the direction pointed by the first arrow X represents the first direction, and the direction pointed by the second arrow Y represents the second direction. Both the first direction and the second direction extend along the horizontal direction and are perpendicular to each other.

[0043] The reinforced concrete support structure in this embodiment includes two layers of horizontal supports. Each layer of horizontal support only includes a horizontal beam 20 extending along the first direction. Each horizontal beam 20 includes two structural segments, and both structural segments are of reinforced concrete structure. For the convenience of description, the two structural segments are respectively called the first structural segment 201 and the second structural segment 202. Each structural segment includes three mutually parallel main support beams 21 extending along the first direction. The adjacent main support beams are connected together by straight connecting rods 22, and the straight connecting rods extend along the second direction. No diagonal connecting rods are provided between the adjacent two main support beams of the same structural segment. The diagonal connecting rod refers to a connecting support that is inclined relative to the first direction or the second direction. The structural segments of the same horizontal beam are connected in sequence along the first direction. The two ends of the horizontal beam 20 are respectively supported on the retaining wall 11 at the edge of the foundation pit. Each structural segment is an integral structure.

[0044] For the convenience of arranging the jacks 31 and also to be able to uniformly apply prestress to the main support beams of each structural segment when prestress is applied, in the same horizontal beam, a loading cross beam 23 is provided on the side of each structural segment facing the other structural segment, that is, a loading cross beam 23 is provided on the side of the first structural segment 201 facing the second structural segment 202, and at the same time a loading cross beam 23 is also provided on the side of the second structural segment 202 facing the first structural segment 201. The loading cross beam and the corresponding structural segment are of integral structure. When prestress is applied to the first structural segment and the second structural segment, the jacks 31 are arranged between the loading cross beams 23 of the first structural segment and the second structural segment. The jacks 31 are used to press against the two structural segments to enable the structural segments to generate prestress. That is, the jacks 31 are arranged between the two relatively arranged loading cross beams.

[0045] A post-cast main support beam 25 is provided between the loading cross beams 23 of the first structural section and the second structural section of the same horizontal beam. The two loading cross beams are connected into one body through the post-cast main support beam 25, so that adjacent structural sections are connected into one body through the post-cast main support beam. The post-cast main support beam is constructed after the prestress is applied to the first structural section and the second structural section, that is, the post-cast main support beam is constructed after the prestress is applied to adjacent structural sections.

[0046] In this embodiment, in the same horizontal beam, the main support beams of each structural section correspond one by one, and the post-cast main support beam corresponds one by one to the main support beam of the connected structural section. The corresponding main support beam and post-cast main support beam extend along the same straight line.

[0047] Please refer to Figure 8 At the same time, in this embodiment, the post-cast main support beam 25 adopts a reinforced concrete structure, and the third main reinforcement 27 in the post-cast main support beam 25 is welded to the first main reinforcement 211 in the loading cross beam. Since the loading cross beam is a part of the structural section, that is, the main reinforcement of the loading cross beam is a part of the main reinforcement in the structural section, the main reinforcement in the post-cast main support beam is connected to the main reinforcement in the adjacent two structural sections.

[0048] Please refer to Figures 2 - 4 At the same time, in this embodiment, a column hole 29 is reserved at the intersection of the main support beam 21 and the straight connecting rod 22. Each structural section is supported on the support column 40, and a column hole is provided corresponding to each support column 40. Please refer to Figure 9 At the same time, in this embodiment, the support column 40 includes a mixing pile 41 and a steel column 42 inserted together. The steel column is located in the upper part, and the part of the support column exceeding the set bottom surface of the foundation pit upward is the steel column. The steel column is freely inserted into the corresponding column hole. It can be understood that in another embodiment, the whole support column can also be set as a steel column.

[0049] The position of the column hole can be arranged as needed without special requirements. It can be understood that in other embodiments, column holes can also be provided only on the main support beams on both sides, and the column holes do not need to be provided at the intersection of the main support beam and the straight connecting rod. The column holes can also be provided on the straight connecting rod.

[0050] When prestress is applied to the structural section, the edge of the column hole has no contact with the steel column. After the prestress application to the structural section is completed, the second main reinforcement 213 in the column hole is connected to the first main reinforcement 211 in the main support beam, and then quick-setting grouting material is poured into the column hole to connect the steel column and the structural section into one body. In this embodiment, the steel column 42 is specifically a steel lattice column with a square cross section, and the column hole 29 is also square.

[0051] In this embodiment, the first main reinforcement extends into the column hole to form a reserved reinforcement head 212, and the second main reinforcement 213 is welded to the reserved reinforcement head. It can be understood that in other embodiments, according to the size of the pile hole, a steel bar section with a set length can be reserved in the column hole and then bent to facilitate the insertion of the steel column. After the prestress is applied, the bent steel bar section is restored and welded to the steel column.

[0052] To avoid reducing the strength of the main support beam due to the setting of the column hole and affecting the stability during prestress application, the angles between the straight connecting rods and the main support beam all adopt an inclined angle of 26° for transition, and two main support beams on the outside protrude outward from the outer side facing the column hole to form a reinforcement block 24 to reinforce the main support beam.

[0053] It can be understood that when the rapid-setting grout in the column hole alone can ensure the structural stability of the horizontal beam, the second main reinforcement in the column hole can be cancelled.

[0054] To enable the structural section to be smoothly supported on the support column and to avoid the structural section bending upward during prestress application, resulting in deformation of the structural section, an upper limit member 252 and a lower limit member are respectively installed on the steel column on the upper side and the lower side of the structural section. Among them, the upper limit member 252 is located on the upper side of the structural section, and the lower limit member is located on the lower side of the structural section. The structural section is slidably supported on the lower limit member, and there is a 1-mm gap between the upper limit member and the structural section. At least one side of the upper limit member extends beyond the edge of the column hole. It can be understood that in other embodiments, the gap between the upper limit member and the structural section can also be 0.5 mm, 1.5 mm, 2 mm, or other distances between 0.5 - 2 mm.

[0055] In this embodiment, the lower limit member includes a flat steel plate 251 and a triangular steel plate 253 for supporting the flat steel plate, and the periphery of the flat steel plate extends beyond the edge of the column hole in all directions to facilitate the complete blocking of the column hole as much as possible and reduce the leakage amount when pouring the rapid-setting grout. The upper limit member adopts an H-shaped steel, and the gap between one side of the H-shaped steel and the edge of the column hole is enlarged as much as possible to facilitate the injection of the rapid-setting grout into the column hole. When observing in the vertical direction, both ends of the upper limit member in the length direction extend beyond the edge of the column hole. It can be understood that in another embodiment, only one end of the upper limit member can extend beyond the edge of the column hole. To avoid the flat steel plate sticking to the concrete during pouring, an isolation paint is applied on the upper surface of the flat steel plate as an isolation layer. In other embodiments, a plastic film or geotextile can also be wrapped on the flat steel plate.

[0056] The upper limit member is welded to the steel column after the structure segment is solidified. It can be understood that in other embodiments, it can also be welded to the steel column through the upper limit member before pouring. To prevent concrete from adhering to the upper limit member, an isolation layer needs to be provided on the lower surface of the upper limit member. The isolation layer can specifically be an isolation paint or materials such as plastic film or geotextile wrapped around it.

[0057] In this embodiment, no diagonal connecting rod is provided between two adjacent main support beams of the same structure segment, that is, no diagonal connecting rod is provided between adjacent main support beams before and after prestress application. It can be understood that according to different needs, a diagonal connecting rod can also be cast or a precast diagonal connecting rod can be installed between adjacent main support beams after prestress application. That is, before prestress application, no diagonal connecting rod is provided between two adjacent main support beams of the same structure segment.

[0058] In this embodiment, the steel column adopts a steel lattice column. It can be understood that in other embodiments, the steel column can also adopt steel pipes, H-shaped steel and other section steels. Please refer to Figure 6 , the steel column is made of a steel pipe 43. To facilitate the connection of the third main reinforcement in the column hole, a flange 44 is welded on the outer peripheral surface of the steel pipe 43. The third main reinforcement can be welded to the flange to improve the welding strength. Of course, the end of the third main reinforcement facing the steel pipe can also be bent and then welded to the steel pipe to increase the welding length, thereby ensuring the welding strength. Figure 7 It is a drawing when the steel column is made of H-shaped steel. The third steel cage can be directly welded to the flange of the H-shaped steel.

[0059] The construction method of the above reinforced concrete support structure is described below. The construction method includes the following steps:

[0060] (1) Please refer to Figure 9 , construct a retaining wall 11 at the set edge of the foundation pit. In this embodiment, the retaining wall is specifically composed of SMW method piles constructed along the edge of the foundation pit. Then, construct a capping beam 12 on the top of the retaining wall 11 and construct support columns 40 in the foundation pit area.

[0061] When constructing the support column 40, use a single-axis mixing pile machine to drill into the ground. In the area above the set elevation of the foundation pit bottom surface, no cement slurry is sprayed, and only the underground soil is loosened. When the drill bit reaches below the set elevation of the foundation pit bottom surface, start spraying cement slurry to form a mixing pile 41, and then insert the steel column 42 downward into the mixing pile 41 to form a support column 40, so that the part of the support column above the set bottom surface of the foundation pit is the steel column.

[0062] (2) In this embodiment, two layers of horizontal supports are provided. From top to bottom, the two layers of horizontal supports are respectively referred to as the first-layer horizontal support and the second-layer horizontal support, and the first-layer horizontal support is located above the second-layer horizontal support. The horizontal beam of the first-layer horizontal support is referred to as the first horizontal beam 210, and the horizontal beam of the second-layer horizontal support is referred to as the second horizontal beam 220.

[0063] First, construct the first-layer horizontal support: Pour the two structural segments of the first horizontal beam 210, and reserve column holes 29 on the structural segments. The column holes 29 surround the outer periphery of the steel column 42. When the strength of each structural segment of the first horizontal beam reaches the set strength, install a jack 31 between two adjacent structural segments of the first horizontal beam, and then apply jacking pressure to the structural segments to make the structural segments generate prestress; after completing the jacking pressure on the structural segments, construct the post-cast main support beam 25 between two adjacent structural segments, so that two adjacent structural segments of the first horizontal beam 210 are connected together through the post-cast main support beam. Complete the construction of each first horizontal beam of the first-layer horizontal support.

[0064] When constructing the post-cast main support beam 25, first weld the two ends of the third main reinforcement 27 to the first main reinforcement 211 in the loading cross beam, and then pour the quick-setting grouting material to form the post-cast main support beam 25. When the strength of the quick-setting grouting material in the post-cast main support beam reaches the set strength, remove the jack for recycling.

[0065] After completing the jacking pressure on the structural segments of the first horizontal beam, a connection step of the steel column is also required. This connection step includes restoring the second main reinforcement 213 in the column hole and pouring the quick-setting grouting material. The second main reinforcement 213 is connected to the first main reinforcement in the structural segment and the steel column.

[0066] The construction of the post-cast main support beam and the connection step of the steel column are not in sequence, and the two can be constructed synchronously or sequentially.

[0067] (3) Excavate the foundation pit. When reaching the construction elevation of the second-layer horizontal support, suspend the excavation of the foundation pit.

[0068] (4) Construct the second-layer horizontal support: Please refer to Figure 10, construct the waling beam 13 on the inner wall of the retaining wall 11, then pour the two structural segments of the second horizontal beam 220 of the second layer of horizontal support, and reserve column holes on the structural segments. The column holes surround the outer periphery of the steel column. When the strength of each structural segment of the second horizontal beam reaches the set strength, install jacks between the adjacent two structural segments of the second horizontal beam, and then apply jacking pressure to the structural segments to generate prestress in the structural segments; after completing the jacking pressure on the structural segments, construct the post-cast main support beam between the adjacent two structural segments, so that the adjacent two structural segments of the second horizontal beam 220 are connected together through the post-cast main support beam. Complete the construction of each second horizontal beam of the second layer of horizontal support. The construction of the post-cast main support beam is the same as that of the post-cast main support beam in step (2) and will not be repeated here.

[0069] (5) Please refer to Figure 11 , in this embodiment, since only two layers of horizontal support are included, after completing the construction of the two layers of horizontal support, continue to excavate the foundation pit until the excavation of the foundation pit is completed, and then construct the underground structure 15.

[0070] When the reinforced concrete support structure includes at least three layers of horizontal support, after completing step (4), repeat step (3) and step (4) until the construction of all the horizontal beams of the horizontal support is completed, and then complete the excavation of the foundation pit.

[0071] When applying jacking pressure to the structural segments, each jack needs to work synchronously.

[0072] When a horizontal beam includes at least three structural segments, when applying prestress, the jacks between the structural segments work synchronously.

[0073] It can be understood that when only one layer of horizontal support is included, after completing step (2), the excavation of the foundation pit can be continued and the excavation of the foundation pit can be completed.

[0074] In this embodiment, only Figure 1 exemplarily shows the structure of a horizontal beam, and each structural segment has only three rows of main support beams and two columns of straight connecting rods. Please refer to Figure 12 the shown embodiment. In this embodiment, the foundation pit is rectangular. Each layer of horizontal support includes the main support A310 and the corner supports A320 at the four corners. The main support A310 only includes a horizontal beam A311, and the structure of this horizontal beam A311 is similar to that of the above-mentioned horizontal beam 20. It also includes two structural segments, and each structural segment also includes three rows of main support beams, but each structural segment includes five columns of straight connecting rods. There are two corner supports A at each corner, and each corner support A includes two structural segments, but each structural segment only includes two rows of main support beams.

[0075] Please refer to again Figure 13In the illustrated embodiment, the foundation pit is rectangular. Each layer of horizontal support includes a main support B410 and corner supports B420 at the four corners. The main support B410 includes only one horizontal beam B411, which is similar in structure to the above-mentioned horizontal beam 20, but includes three structural segments. Each structural segment includes three rows of main support beams. The middle structural segment has six columns of straight connecting rods, and the two structural segments on both sides each have two columns of straight connecting rods. There are two corner supports B at each corner. Each corner support A includes two structural segments, but each structural segment only includes two rows of main support beams.

[0076] In Figure 12 In the illustrated embodiment, two diagonal braces A312 are respectively arranged at both ends of the horizontal beam A311 in the length direction. The two diagonal braces A311 at the same end are respectively located on both sides of the horizontal beam A311 in the width direction and are symmetrically arranged. In Figure 13 In the illustrated embodiment, two diagonal braces B412 are respectively arranged at both ends of the horizontal beam B411 in the length direction. The two diagonal braces B411 at the same end are respectively located on both sides of the horizontal beam B411 in the width direction and are symmetrically arranged. The above-mentioned diagonal braces A311 and diagonal braces B411 are different from the diagonal connecting rods mentioned above. The diagonal braces A311 and diagonal braces B411 are respectively connected between the main support beam and the capping beam, or connected between the main support beam and the waling beam, in order to improve the stability between the main support beam and the waling beam or capping beam. Their installation positions and functions are different from those of the diagonal connecting rods. During the prestressing process, secondary stresses will be generated in both the diagonal braces A311 and diagonal braces B411. However, since two symmetrically arranged diagonal braces A312 and diagonal braces B412 are respectively arranged at both ends of the horizontal beam A311 and horizontal beam B411, the secondary stresses generated by the diagonal braces A312 and diagonal braces B412 reach equilibrium and do not have the tendency to distort the horizontal beam A311 or horizontal beam B411.

Claims

1. A prestressed reinforced concrete support structure, characterized in that, Comprising at least one layer of horizontal supports, each layer of horizontal supports comprising at least one horizontal beam, at least one horizontal beam comprising at least two structural segments, each structural segment comprising at least two main support beams that are parallel to each other and extend along the extension direction of the horizontal beam, adjacent main support beams of the same structural segment being connected together by straight connecting rods that are perpendicular to the main support beams; the structural segments of the same horizontal beam are sequentially connected and connected into one body by post-cast main support beams, the post-cast main support beams being constructed after the prestress is applied to the structural segments, and each structural segment is a reinforced concrete structure.

2. The reinforced concrete support structure according to claim 1, wherein, In the same horizontal beam, a loading cross beam is provided on one side of each structural segment facing another structural segment, and a jack can be arranged between two relatively arranged loading cross beams to jack-press adjacent two structural segments to cause the structural segments to generate prestress.

3. The reinforced concrete support structure according to claim 1, characterized in that, The main reinforcement bars in the post-cast main support beam are connected to the main reinforcement bars in the adjacent two structural segments.

4. The reinforced concrete support structure according to claim 1, characterized in that, Each structural segment is supported on a support column, and at least corresponding to one support column, a column hole is reserved on the structural segment. The part of the support column exceeding the set bottom surface of the foundation pit upward is a steel column, and the steel column can be freely inserted into the corresponding column hole. When prestress is applied to the structural segment, the edge of the column hole has no contact with the steel column; after the prestress application to the structural segment is completed, concrete is poured into the column hole to connect the steel column and the structural segment into one body.

5. The reinforced concrete support structure according to claim 4, characterized in that, When pouring concrete into the column hole, first restore the main reinforcement bars in the column hole, and then pour concrete, and the main reinforcement bars in the column hole are connected to the main reinforcement bars in the structural segment and the steel column.

6. The reinforced concrete support structure according to claim 4, wherein An upper limit member and a lower limit member are fixedly installed on the steel column. The upper limit member is located on the upper side of the structural segment, and the lower limit member is located on the lower side of the structural segment. The structural segment is slidably supported on the lower limit member. There is a gap of 0-2 mm between the upper limit member and the structural segment, and at least one side of the upper limit member extends beyond the edge of the column hole.

7. The reinforced concrete support structure according to claim 1, wherein Before applying prestress, no diagonal connecting rod is provided between adjacent main support beams of the same structural segment.

8. The reinforced concrete support structure according to claim 1, wherein In the same horizontal beam, the main support beams of each structural segment correspond one by one, and the post-cast main support beam and the main support beam of the connected structural segment correspond one by one, and the corresponding main support beam and post-cast main support beam extend along the same straight line.

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