Prestressed reinforced concrete supporting structure and construction method thereof

Abstract

The invention provides a prestressed reinforced concrete supporting structure which comprises at least one layer of horizontal support, each layer of horizontal support at least comprises a horizontal beam, at least one horizontal beam comprises at least two structural sections, and the structural sections of the same horizontal beam are connected in sequence. The adjacent structural sections of the same horizontal beam are connected into a whole through a post-pouring main supporting beam, the post-pouring main supporting beam is constructed after prestress is applied to the adjacent structural sections, and each structural section is of a reinforced concrete structure. The invention further provides a construction method of the prestressed reinforced concrete supporting structure. The horizontal beam is divided into at least two structural sections, and the structural sections are connected into a whole after prestress is applied to the structural sections, so that the complete horizontal beam is formed. The problems that an existing reinforced concrete supporting structure can only passively resist the external soil pressure of the foundation pit and the deformation of the foundation pit is large due to the fact that no prestress exists can be smoothly solved, and the safety of foundation pit construction is improved.

Description

Technical Field

[0001] The invention relates to a prestressed reinforced concrete supporting structure and a construction method thereof. Background Art

[0002] In foundation pit construction, in order to control deformation, avoid safety accidents caused by foundation pit collapse and affect the construction progress, supports are generally set up to ensure the stability of the side walls of the foundation pit. In the foundation pit support, horizontal beams are mainly used, especially in deep foundation pit construction. The horizontal beam structure generally has two types: reinforced concrete structure and steel structure. Among them, steel structure is mainly used in small foundation pits, while reinforced concrete structure is generally used in large foundation pits. Reinforced concrete support structure has the advantages of large support stiffness, safety and reliability, simple construction, and no restrictions on the shape of the foundation pit. However, since the reinforced concrete support structure is an integral cast-in-place construction, after the construction is completed, the soil pressure outside the foundation pit changes, and it is impossible to apply prestress to the reinforced concrete support, resulting in the reinforced concrete support structure can only passively resist the soil pressure outside the foundation pit, that is, after the side wall of the foundation pit tilts inward and deforms, the reinforced concrete support structure can truly play a supporting role. However, after the side wall of the foundation pit tilts and deforms, the side wall of the foundation pit has caused a collapse trend, which poses a certain risk to the safety of the foundation pit. Therefore, it is necessary to improve the safety of the reinforced concrete support structure and control deformation. Summary of the invention

[0003] In order to solve the problem that the reinforced concrete support structure in the prior art cannot apply prestress and can only passively resist the soil pressure outside the foundation pit, which leads to large deformation of the foundation pit and is difficult to control, the present application first proposes 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 sections, the structural sections of the same horizontal beam are connected in sequence, and the adjacent structural sections of the same horizontal beam are connected as a whole through a post-cast main support beam, which is constructed after the adjacent structural sections are prestressed, and each structural section is a reinforced concrete structure. Each structural section is preferably constructed by cast-in-place.

[0004] In the present application, the horizontal beam is divided to form at least two structural sections, and then prestress is applied to each structural section. After the prestress is applied, each structural section is connected as a whole by a post-cast main support beam to form a complete horizontal beam. The present application can smoothly solve the problem that the existing reinforced concrete support structure can only passively resist the external soil pressure of the foundation pit due to the lack of prestress, and the deformation of the foundation pit is large. After the prestress is applied to the horizontal beam, the horizontal beam can actively resist the soil pressure outside the foundation pit. In the process of applying prestress to each structural section, the side wall of the foundation pit will be tilted toward the outside of the foundation pit and compressed and deformed. When the side wall of the foundation pit is tilted toward the inside of the foundation pit under the push of the external soil pressure, the horizontal deformation of the side wall of the foundation pit can be reduced due to the presence of the prestress of the horizontal beam, thereby improving the safety of the foundation pit construction.

[0005] Furthermore, in order to facilitate the jacking of each structural segment to smoothly apply prestress, in the same horizontal beam, each structural segment is provided with a loading beam on one side facing the other structural segment. When applying prestress to the structural segment, the jack is arranged between the two oppositely arranged loading beams, and the jack is used to jack the structural segment to generate prestress. The loading beam can be used to connect the main support beams constituting the horizontal beam into a whole, so that the main support beams can be evenly jacked, so that the main support beams produce relatively uniform deformation.

[0006] Specifically, in order to ensure the strength of the post-cast main support beam, the main reinforcement in the post-cast main support beam is connected with the main reinforcement in two adjacent structural sections.

[0007] Specifically, each structural segment is supported on a support column, corresponding to at least one support column, and a column hole is reserved on the structural segment. The portion of the support column that exceeds the 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 the structural segment is prestressed, the edge of the column hole has no contact with the steel column; after the prestress is applied to the structural segment, concrete is poured in the column hole to connect the steel column and the structural segment as a whole. The steel column and the structural segment are connected as a whole by using the concrete in the column hole, so that the support column and the horizontal beam are connected as a whole, so as 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, the side wall of the foundation pit will gradually tilt toward the inside of the foundation pit, exerting pressure on the horizontal beam. Under the external pressure, the horizontal beam has a tendency to bend in the vertical direction. The horizontal beam is fixed on the support column by using the concrete in the column hole, and the support column is used to improve the stability of the horizontal beam, thereby ensuring the safety of the foundation pit.

[0008] Furthermore, to ensure the strength of the opening area, when pouring concrete in the column hole, the main reinforcement in the column hole is first restored, and then the concrete is poured, and the main reinforcement in the column hole is connected to the main reinforcement in the structural section and the steel column. After the main reinforcement in the column hole is connected to the steel column, the connection strength between the steel column and the horizontal beam can be improved, ensuring the stability of the connection between the two.

[0009] Furthermore, in order to avoid the structural segment from bending upward or downward during the application of prestress, an upper limit member and a lower limit member are installed on the steel column on the upper and lower sides of the structural segment respectively, wherein 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, and the structural segment is slidably supported on the lower limit member, and there is a gap of 0-2mm between the upper limit member and the structural segment, and at least one side of the upper limit member extends outward beyond the edge of the column hole.

[0010] The upper limit piece and the lower limit piece are fixedly installed on the steel column. In order to ensure that the structural section can slide along the lower limit piece during the prestressing process, an isolation layer needs to be set on the lower limit piece before pouring the concrete of the structural section. The isolation layer can be isolation paint or isolation cloth. 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 piece can be installed before the concrete is poured on the structural section, or it can be installed after the structural section reaches the set strength and before the prestress is applied. When the upper limit piece is installed before the concrete is poured, it is necessary to apply isolation paint on the lower surface of the upper limit piece or wrap it with geotextile, plastic film and other materials as an isolation layer to avoid the bond strength between the concrete and the upper limit piece being too strong, causing the support column to tilt when the prestress is applied. Regardless of the installation method used for the upper limit piece, it is not recommended that its lower surface be attached to the structural section, and it is best to have a gap of 0.5-2mm. This is because when the upper limit piece is attached to the structural section, due to the actual construction error, the upper limit piece will sometimes be tightly pressed against the structural section, affecting the application of prestress.

[0012] Furthermore, each structural section includes at least two main support beams that are parallel to each other and extend along the extension direction of the horizontal beam. Before applying prestress, no diagonal connecting rod is arranged between two adjacent main support beams of the same structural section. The diagonal connecting rod refers to a connecting piece that is connected between two adjacent main support beams and is arranged obliquely relative to the main support beam. In the existing conventional design, a straight connecting rod and a diagonal connecting rod are arranged between the main support beams, wherein the straight connecting rod is perpendicular to the main support beam and the diagonal connecting rod is inclined to the main support beam, so that 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 the present application, after the diagonal connecting rod is arranged between the main support beams, secondary stress will be generated on the diagonal connecting rod during the application of prestress. The secondary stress will generate thrust in opposite directions on the two connected main support beams, which has a tendency to cause the horizontal beam to twist and deform, increasing the instability of the horizontal beam, and is not conducive to the safe construction of the foundation pit.

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

[0014] Secondly, the present application also discloses a construction method of any of the above-mentioned prestressed reinforced concrete support structures. When the prestressed reinforced concrete support structure includes only one layer of horizontal support, the construction method includes the following steps:

[0015] (1) Construct a retaining wall at the set edge of the foundation pit, then construct a crown beam on the top of the retaining wall, and construct a support column in the foundation pit area. The part of the support column that exceeds the set bottom surface of the foundation pit is a steel column;

[0016] (2) Construction of the first layer of horizontal support: Cast in situ 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 periphery of the steel columns. When the strength of each structural segment of the same frame of horizontal beams reaches the set strength, install jacks between two adjacent structural segments of the same frame of horizontal beams, and then press the structural segments to produce prestress. After the pressing of the structural segments is completed, construct the post-cast main support beam between the two adjacent structural segments, so that the two adjacent structural segments are connected together through the post-cast main support beam. Complete the construction of each horizontal beam of the first layer of horizontal support;

[0017] (3) Complete the excavation of the foundation pit;

[0018] When the prestressed reinforced concrete support structure includes at least two layers of horizontal supports, the construction method includes the following steps:

[0019] (1) Construct a retaining wall at the set edge of the foundation pit, then construct a crown beam on the top of the retaining wall, and construct a support column in the foundation pit area. The part of the support column that exceeds the set bottom surface of the foundation pit is a steel column;

[0020] (2) Construction of the first layer of horizontal support: Cast in situ 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 periphery of the steel columns. When the strength of each structural segment of the same frame of horizontal beams reaches the set strength, install jacks between two adjacent structural segments of the same frame of horizontal beams, and then press the structural segments to produce prestress. After the pressing of the structural segments is completed, construct the post-cast main support beam between the two adjacent structural segments, so that the two adjacent structural segments are connected together through the post-cast main support beam. Complete the construction of each horizontal beam of the first layer of horizontal support;

[0021] (3) Excavate the foundation pit. When the construction elevation of the second-layer horizontal support is reached, suspend the excavation of the foundation pit;

[0022] (4) Construction of the second-layer horizontal support: Cast in situ 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 each structural segment of the same horizontal beam reaches the set strength, install jacks between two adjacent structural segments of the same horizontal beam, and then press the structural segment to produce prestress. After the pressing of the structural segment is completed, construct a post-cast main support beam between the two adjacent structural segments, so that the two adjacent structural segments are connected together through the post-cast main support beam. Complete the construction of each horizontal beam of the second-layer horizontal support;

[0023] (5) When only two layers of horizontal support are included, the excavation of the foundation pit is completed;

[0024] When at least three layers of horizontal supports are included, steps (3) and (4) are repeated until the construction of the horizontal beams of all horizontal supports is completed, and then the excavation of the foundation pit is completed.

[0025] When the same layer of horizontal supports includes at least two horizontal beams, the order of applying prestress to the horizontal beams of the same layer of horizontal supports is not particular, and can be carried out simultaneously or in steps.

[0026] By using this construction method, prestress can be applied to each structural segment of the horizontal beam, so that the entire horizontal beam generates internal stress, so that the horizontal beam can actively resist the soil pressure outside the foundation pit, reduce the degree of deformation caused by the external soil pressure, thereby reducing the degree of deformation of the side wall of the foundation pit, and improving the safety of the foundation pit construction. After the prestress is applied, each structural segment is connected as a whole through the post-cast main support beam, which ensures the integrity of the horizontal beam.

[0027] In order to ensure the strength of the opening area, the steel column connection step is also included, which includes restoring the main reinforcement in the column hole and pouring concrete in the column hole, and the main reinforcement in the column hole is connected to the main reinforcement in the structural section and the steel column. After the main reinforcement in the column hole is connected to the steel column, the connection strength between the steel column and the horizontal beam can be improved, and the stability of the connection between the two can be ensured.

[0028] Furthermore, in order to generate uniform prestress for each structural segment, when the same horizontal beam includes at least three structural segments, when applying prestress, the jacks between each structural segment work synchronously. 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, so that each structural segment can generate 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 limiter of the support column. During the process of applying prestress, the structural segment will inevitably produce friction with the lower limiter, thereby 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 prestressing section, the smaller its deformation. However, after the prestressing is completed, the deformation inside each structural segment will gradually equalize to achieve uniform deformation. Since some areas cannot be fully deformed during the prestressing process, the prestress will be correspondingly reduced in the subsequent equalization process, reducing the effect of prestressing.

[0029] The beneficial effects of the present application are summarized as follows: 1. The prestressed reinforced concrete support structure has high rigidity and can effectively control the horizontal displacement of the foundation pit; 2. The application of prestress is simple and efficient; 3. During the application of prestress, no secondary internal force will be generated on the supporting components, and the structure has high safety; 4. Due to the high rigidity of the prestressed reinforced concrete support structure, compared with the traditional reinforced concrete support structure without prestress, it has a small cross-section, uses less steel and concrete materials, and saves 10-20% of the cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a structural schematic diagram of an embodiment of a prestressed reinforced concrete support structure in the present application.

[0031] Figure 2 yes Figure 1 Enlarged view of part A.

[0032] Figure 3 yes Figure 2 View from the center BB direction.

[0033] Figure 4 yes Figure 3 The schematic diagram of the column hole after pouring is shown in the accompanying drawing.

[0034] Figure 5 This is the first schematic diagram of the arrangement of the main reinforcement in the column hole.

[0035] Figure 6 This is the second schematic diagram of the arrangement of the main reinforcement in the column hole.

[0036] Figure 7 This is the third schematic diagram of the arrangement of main reinforcement in column holes.

[0037] Figure 8 This is a schematic diagram of the arrangement of the main reinforcement in the post-cast main support beam when the post-cast main support beam adopts reinforced concrete structure.

[0038] Fig. 9 This is a simplified structural diagram when prestress is applied to the first horizontal beam.

[0039] Fig.10 This is a simplified structural diagram when prestress is applied to the second horizontal beam.

[0040] Fig.11 It is a schematic diagram of the structure after the foundation pit excavation is completed.

[0041] Fig.12 It is a schematic diagram of the structure of horizontal support in a foundation pit.

[0042] Fig.13 It is a schematic diagram of the structure of horizontal support in another foundation pit. DETAILED DESCRIPTION

[0043] The following first describes the prestressed reinforced concrete support structure in the present application.

[0044] See also Figure 1-Figure 8 , Figure 1 The direction of the first arrow X in the figure indicates a first direction, and the direction of the second arrow Y indicates a second direction. Both the first direction and the second direction extend in a horizontal direction and are perpendicular to each other.

[0045] The prestressed reinforced concrete support structure in this embodiment includes two layers of horizontal support, each layer of horizontal support includes only one horizontal beam 20 extending along the first direction, each horizontal beam 20 includes two structural sections, and both structural sections are reinforced concrete structures. For the convenience of description, the two structural sections are respectively referred to as the first structural section 201 and the second structural section 202. Each structural section includes three mutually parallel main support beams 21 extending along the first direction. Adjacent main support beams are connected together by straight connecting rods 22, which extend along the second direction. No oblique connecting rods are set between two adjacent main support beams of the same structural section. The oblique connecting rod refers to a connecting support inclined relative to the first direction or the second direction. The structural sections of the same horizontal beam are connected along the first direction. The two ends of the horizontal beam 20 are respectively supported on the supporting wall 11 at the edge of the foundation pit. Each structural section is an integral structure.

[0046] In order to facilitate the arrangement of the jacks 31 and to evenly apply prestress to the main support beams of each structural segment when applying prestress, a loading beam 23 is provided on the side of each structural segment facing the other structural segment in the same horizontal beam, that is, a loading beam 23 is provided on the side of the first structural segment 201 facing the second structural segment 202, and a loading beam 23 is also provided on the side of the second structural segment 202 facing the first structural segment 201, and the loading beam and the corresponding structural segment are an integrated structure. When applying prestress to the first structural segment and the second structural segment, the jack 31 is arranged between the loading beams 23 of the first structural segment and the second structural segment, and the jack 31 is used to press the two structural segments to generate prestress in the structural segments. That is, the jack 31 is arranged between two loading beams arranged opposite to each other.

[0047] A post-cast main support beam 25 is arranged between the first structural segment and the loading beam 23 of the second structural segment of the same horizontal beam, and the two loading beams are connected as a whole through the post-cast main support beam 25, so that the adjacent structural segments are connected as a whole through the post-cast main support beam. The post-cast main support beam is constructed after the prestressing is completed on the first structural segment and the second structural segment, that is, the post-cast main support beam is constructed after the prestressing is completed on the adjacent structural segments.

[0048] In this embodiment, in the same horizontal beam, the main support beams of each structural segment correspond one to one, and the post-cast main support beams correspond one to one with the main support beams of the connected structural segment, and the corresponding main support beams and post-cast main support beams extend along the same straight line.

[0049] Please also see Figure 8In 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 together with the first main reinforcement 211 in the loading beam. Since the loading beam is part of the structural segment, that is, the main reinforcement of the loading beam is part of the main reinforcement in the structural segment, the main reinforcement in the post-cast main support beam is connected with the main reinforcement in the two adjacent structural segments.

[0050] See also Figure 2-Figure 4 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 a support column 40, and a column hole is provided corresponding to each support column 40. Please also refer to Fig. 9 In this embodiment, the support column 40 includes a mixing pile 41 and a steel column 42 plugged together, the steel column is located at the upper part, and the part of the support column that exceeds the bottom surface of the foundation pit upward is the steel column, and the steel column is freely inserted into the corresponding column hole. It can be understood that in another embodiment, the entire support column can also be set as a steel column.

[0051] The position of the column hole can be arranged as needed without special requirements. It can be understood that in other embodiments, the column holes can be set only on the main support beams on both sides, and the column holes do not need to be set at the intersection of the main support beam and the straight connecting rod. The column holes can also be set on the straight connecting rod.

[0052] When prestress is applied to the structural segment, the edge of the column hole has no contact with the steel column. After the prestress is applied to the structural segment, the second main reinforcement 213 of the column hole is connected to the first main reinforcement 211 in the main support beam, and then a quick-setting grouting material is poured into the column hole to connect the steel column and the structural segment as a whole. 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.

[0053] 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, a reinforcement segment of a set length can be reserved in the column hole according to the size of the pile hole, and then bent to facilitate the insertion of the steel column. After the prestressing is completed, the bent reinforcement segment is restored and welded to the steel column.

[0054] In order to avoid reducing the strength of the main support beam due to the provision of the column hole, which affects the stability when the prestress is applied, the angle between the straight connecting rod and the main support beam adopts an oblique angle 26 transition, and the outer sides of the two main support beams located on the outside facing the column hole protrude outward to form a reinforcement block 24 to reinforce the main support beam.

[0055] It can be understood that when the structural stability of the horizontal beam can be ensured by only using the quick-setting grouting material in the column hole, the second main reinforcement in the column hole can be eliminated.

[0056] In order to smoothly support the structural segment on the support column and to avoid the structural segment from bending upward during the prestressing process, which causes deformation of the structural segment, an upper limit member 252 and a lower limit member installed on the steel column are provided on the upper and lower sides of the structural segment, respectively, wherein the upper limit member 252 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, and there is a gap of 1mm between the upper limit member and the structural segment, and at least one side of the upper limit member extends outwardly beyond the edge of the column hole. It is understood that in other embodiments, the gap between the upper limit member and the structural segment can also be 0.5mm, 1.5mm or 2mm, as well as other distances between 0.5-2mm.

[0057] 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 four sides of the flat steel plate extend outwardly beyond the edge of the column hole, so as to completely block the column hole as much as possible and reduce the leakage when pouring the fast-setting grouting material. The upper limit member is made of H-steel, and the gap between one side of the H-steel and the edge of the column hole is expanded as much as possible to facilitate the injection of fast-setting grouting material into the column hole. Observed in the vertical direction, the two ends of the upper limit member in the length direction respectively exceed the edge of the column hole. It can be understood that in another embodiment, only one end of the upper limit member can extend outward beyond the edge of the column hole. In order to prevent the flat steel plate from sticking to the concrete during pouring, an isolation paint is applied to the upper surface of the flat steel plate as an isolation layer. In other embodiments, the flat steel plate can also be wrapped with a plastic film or geotextile.

[0058] The upper limit piece is welded to the steel column after the structural segment has completely solidified. It can be understood that in other embodiments, the upper limit piece can also be welded to the steel column before pouring. In order to avoid the concrete sticking to the upper limit piece, it is necessary to set an isolation layer on the lower surface of the upper limit piece. The isolation layer can specifically be painted with isolation paint or wrapped with plastic film, geotextile and other materials.

[0059] In this embodiment, no diagonal connecting rod is provided between two adjacent main support beams of the same structural section, that is, no diagonal connecting rod is provided between adjacent main support beams before and after the prestress is applied. It can be understood that, according to different needs, diagonal connecting rods can be cast or prefabricated between adjacent main support beams after the prestress is applied. That is, no diagonal connecting rod is provided between two adjacent main support beams of the same structural section before the prestress is applied.

[0060] In this embodiment, the steel columns are steel lattice columns. It can be understood that in other embodiments, the steel columns can also be made of steel pipes, H-steel and other steel sections. Figure 6The steel column is made of a steel pipe 43. In order to facilitate the connection of the third main reinforcement in the column hole, a flange 44 is welded on the outer circumferential surface of the steel pipe 43. The third main reinforcement can be welded to the flange to improve the welding strength. Of course, the third main reinforcement can also be bent toward one end of the steel pipe and then welded to the steel pipe to increase the welding length, thereby ensuring the welding strength. Figure 7 This is a diagram showing a steel column made of H-steel. The third reinforcement cage can be directly welded to the flange of the H-steel.

[0061] The construction method of the prestressed reinforced concrete support structure is described below. The construction method includes the following steps:

[0062] (1) Please refer to Fig. 9 A retaining wall 11 is constructed at a set edge of the foundation pit. In this embodiment, the retaining wall is specifically composed of SMW piles constructed along the edge of the foundation pit. Then, a crown beam 12 is constructed on the top of the retaining wall 11, and a support column 40 is constructed in the foundation pit area.

[0063] When constructing the support column 40, a single-axis pile mixing machine is used to drill underground. Cement slurry is not sprayed in the area above the set elevation of the bottom of the foundation pit. Only the underground soil is loosened. When the drill bit reaches below the set elevation of the bottom of the foundation pit, cement slurry is started to be sprayed to form a mixing pile 41. Then, a steel column 42 is inserted downward into the mixing pile 41 to form a support column 40, so that the part of the support column that exceeds the set bottom of the foundation pit is a steel column.

[0064] (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 of horizontal supports and the second layer of horizontal supports. The first layer of horizontal supports is located on the upper side of the second layer of horizontal supports. The horizontal beams of the first layer of horizontal supports are referred to as the first horizontal beams 210, and the horizontal beams of the second layer of horizontal supports are referred to as the second horizontal beams 220.

[0065] First, the first layer of horizontal support is constructed: two structural sections of the first horizontal beam 210 are cast, and column holes 29 are reserved on the structural sections. The column holes 29 surround the outer periphery of the steel columns 42. When the strength of each structural section of the first horizontal beam reaches the set strength, a jack 31 is installed between two adjacent structural sections of the first horizontal beam, and then the structural section is pressed to produce prestress in the structural section; after the pressing of the structural section is completed, a post-cast main support beam 25 is constructed between the two adjacent structural sections, so that the two adjacent structural sections of the first horizontal beam 210 are connected together through the post-cast main support beam. The construction of each first horizontal beam of the first layer of horizontal support is completed.

[0066] When constructing the post-cast main support beam 25, firstly, the two ends of the third main reinforcement 27 are welded to the first main reinforcement 211 in the loading beam, and then the fast-setting grouting material is poured to form the post-cast main support beam 25. When the strength of the fast-setting grouting material in the post-cast main support beam reaches the set strength, the jack is removed and recycled.

[0067] After the top pressing of the structural section of the first horizontal beam is completed, a connection step of the steel column is required, which includes restoring the second main reinforcement 213 in the column hole and pouring fast-setting grouting material. The second main reinforcement 213 is connected to the first main reinforcement in the structural section and the steel column.

[0068] There is no particular order in the construction of the post-cast main support beams and the connection of the steel columns. The two can be constructed simultaneously or sequentially.

[0069] (3) Excavate the foundation pit. When the construction elevation of the second-layer horizontal support is reached, suspend the excavation of the foundation pit.

[0070] (4) Construction of the second horizontal support: Please refer to Fig.10 , construct the purlin 13 on the inner wall of the supporting wall 11, then cast the two structural sections of the second horizontal beam 220 of the second horizontal support, and reserve column holes on the structural sections, the column holes surround the outer circumference of the steel columns, when the strength of each structural section of the second horizontal beam reaches the set strength, install a jack between two adjacent structural sections of the second horizontal beam, and then press the structural section to produce prestress; after completing the pressing of the structural section, construct a post-cast main support beam between the two adjacent structural sections, so that the two adjacent structural sections 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 horizontal support. The construction of the post-cast main support beam is the same as the construction of the post-cast main support beam in step (2), and will not be repeated.

[0071] (5) Please refer to Fig.11 Since only two layers of horizontal supports are included in this embodiment, after the construction of the two layers of horizontal supports is completed, the excavation of the foundation pit is continued until the excavation of the foundation pit is completed, and then the underground structure 15 is constructed.

[0072] When the prestressed reinforced concrete support structure includes at least three layers of horizontal supports, after completing step (4), steps (3) and (4) are repeated until the construction of the horizontal beams of all horizontal supports is completed, and then the excavation of the foundation pit is completed.

[0073] When pressing the structural section, the jacks need to work synchronously.

[0074] When a horizontal beam includes at least three structural sections, the jacks between the structural sections work synchronously when prestressing is applied.

[0075] 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 continue and the excavation of the foundation pit can be completed.

[0076] In this embodiment, only Figure 1 The structure of a horizontal beam is shown as an example, and each structural section has only three rows of main beams and two rows of straight connecting rods, see Fig.12 In the embodiment shown, the foundation pit is rectangular, and each layer of horizontal support includes a main support A310 and angle supports A320 located at four corners. The main support A310 includes only one horizontal beam A311. The horizontal beam A311 has a similar structure to the horizontal beam 20 described above, and also includes two structural sections. Each structural section also includes three rows of main support beams, but each structural section includes five rows of straight connecting rods. There are two angle supports A at each corner, and each angle support A includes two structural sections, but each structural section only includes two rows of main support beams.

[0077] Please see again Fig.13 In the embodiment shown, the foundation pit is rectangular, and each layer of horizontal support includes a main support B410 and angle supports B420 located at four corners. The main support B410 only includes a horizontal beam B411. The horizontal beam B411 is similar to the structure of the above-mentioned horizontal beam 20, but includes three structural sections. Each structural section includes three rows of main support beams. The structural section in the middle has six rows of straight connecting rods, and the two structural sections on both sides have two rows of straight connecting rods. There are two angle supports B at each corner, and each angle support A includes two structural sections, but each structural section only includes two rows of main support beams.

[0078] exist Fig.12 In the embodiment shown, two diagonal braces A312 are respectively arranged at both ends of the horizontal beam A311 in the length direction, and the two diagonal braces A311 at the same end are respectively arranged at both sides of the horizontal beam A311 in the width direction and are symmetrically arranged. Fig.13 In the embodiment shown, two diagonal braces B412 are respectively provided at both ends of the horizontal beam B411 in the length direction, and the two diagonal braces B411 located 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 brace A311 and diagonal brace B411 are different from the diagonal connecting rods mentioned above. The diagonal brace A311 and diagonal brace B411 are respectively connected between the main support beam and the crown beam, or between the main support beam and the surrounding purlin. The purpose is to improve the stability between the main support beam and the surrounding purlin or the crown beam. The installation position and function are different from the diagonal connecting rods. During the process of applying prestress, the diagonal brace A311 and the diagonal brace B411 will generate secondary stress. However, since two symmetrically arranged diagonal braces A312 and diagonal brace B412 are respectively arranged at both ends of the horizontal beam A311 and the horizontal beam B411, the secondary stresses generated by the diagonal brace A312 and the diagonal brace B412 are balanced, and there is no tendency to cause the horizontal beam A311 or the horizontal beam B411 to twist.

Claims

1. A prestressed reinforced concrete support structure, characterized in that: It 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 sections, the structural sections of the same horizontal beam are connected in sequence, and the adjacent structural sections of the same horizontal beam are connected as a whole through a post-cast main support beam. The post-cast main support beam is constructed after the adjacent structural sections are prestressed, and each structural section is a reinforced concrete structure.

2. The prestressed reinforced concrete support structure according to claim 1, characterized in that: In the same horizontal beam, a loading beam is provided on the side of each structural segment facing the other structural segment. When prestress is applied to the structural segment, a jack is arranged between two oppositely arranged loading beams. The jack is used to press the structural segment to generate prestress in the structural segment.

3. The prestressed reinforced concrete support structure according to claim 1, characterized in that: The main reinforcement in the post-cast main support beam is connected with the main reinforcement in the two adjacent structural sections.

4. The prestressed reinforced concrete support structure according to claim 1, characterized in that: Each structural segment is supported on a supporting column, corresponding to at least one supporting column. A column hole is reserved on the structural segment. The part of the supporting column that exceeds the set bottom surface of the foundation pit upward is a steel column. 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 is applied to the structural segment, concrete is poured in the column hole to connect the steel column and the structural segment as one.

5. The prestressed reinforced concrete support structure according to claim 4, characterized in that: When pouring concrete in the column hole, the main reinforcement in the column hole is restored first, and then the concrete is poured, and the main reinforcement in the column hole is connected with the main reinforcement in the structural section and the steel column.

6. The prestressed reinforced concrete support structure according to claim 4, characterized in that: An upper limit piece and a lower limit piece are respectively provided on the upper and lower sides of the structural segment, wherein the upper limit piece is located on the upper side of the structural segment, and the lower limit piece is located on the lower side of the structural segment, and the structural segment is slidably supported on the lower limit piece, and there is a gap of 0-2mm between the upper limit piece and the structural segment, and at least one side of the upper limit piece extends outwardly beyond the edge of the column hole.

7. The prestressed reinforced concrete support structure according to claim 1, characterized in that: Each structural section includes at least two main support beams which are parallel to each other and extend along the extension direction of the horizontal beam. Before applying prestress, no diagonal connecting rod is arranged between two adjacent main support beams of the same structural section.

8. The prestressed reinforced concrete support structure according to claim 7, characterized in that: In the same horizontal beam, the main supporting beams of each structural segment correspond one to one, and the post-cast main supporting beams correspond one to one with the main supporting beams of the connected structural segment, and the corresponding main supporting beams and post-cast main supporting beams extend along the same straight line.

9. The construction method of the prestressed reinforced concrete support structure according to any one of claims 1 to 8, characterized in that: When the prestressed reinforced concrete support structure includes only one layer of horizontal support, the construction method includes the following steps: (1) Construct a retaining wall at the set edge of the foundation pit, then construct a crown beam on the top of the retaining wall, and construct a support column in the foundation pit area. The part of the support column that exceeds the set bottom surface of the foundation pit is a steel column; (2) Construction of the first layer of horizontal support: Cast in situ 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 periphery of the steel columns. When the strength of each structural segment of the same frame of horizontal beams reaches the set strength, install jacks between two adjacent structural segments of the same frame of horizontal beams, and then press the structural segments to produce prestress. After the pressing of the structural segments is completed, construct the post-cast main support beam between the two adjacent structural segments, so that the two adjacent structural segments are connected together through the post-cast main support beam. Complete the construction of each horizontal beam of the first layer of horizontal support; (3) Complete the excavation of the foundation pit; When the prestressed reinforced concrete support structure includes at least two layers of horizontal supports, the construction method includes the following steps: (1) Construct a retaining wall at the set edge of the foundation pit, then construct a crown beam on the top of the retaining wall, and construct a support column in the foundation pit area. The part of the support column that exceeds the set bottom surface of the foundation pit is a steel column; (2) Construction of the first layer of horizontal support: Cast in situ 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 periphery of the steel columns. When the strength of each structural segment of the same frame of horizontal beams reaches the set strength, install jacks between two adjacent structural segments of the same frame of horizontal beams, and then press the structural segments to produce prestress. After the pressing of the structural segments is completed, construct the post-cast main support beam between the two adjacent structural segments, so that the two adjacent structural segments are connected together through the post-cast main support beam. Complete the construction of each horizontal beam of the first layer of horizontal support; (3) Excavate the foundation pit. When the construction elevation of the second-layer horizontal support is reached, suspend the excavation of the foundation pit; (4) Construction of the second-layer horizontal support: Cast in situ 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 each structural segment of the same horizontal beam reaches the set strength, install jacks between two adjacent structural segments of the same horizontal beam, and then press the structural segment to produce prestress. After the pressing of the structural segment is completed, construct a post-cast main support beam between the two adjacent structural segments, so that the two adjacent structural segments are connected together through the post-cast main support beam. Complete the construction of each horizontal beam of the second-layer horizontal support; (5) When only two layers of horizontal support are included, the excavation of the foundation pit is completed; When at least three layers of horizontal supports are included, steps (3) and (4) are repeated until the construction of the horizontal beams of all horizontal supports is completed, and then the excavation of the foundation pit is completed.

10. The construction method according to claim 9, characterized in that: When the same horizontal beam includes at least three structural sections, the jacks between the structural sections work synchronously when prestressing is applied.

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