Dark support structure for limiting deformation in passive zone of substrate and construction method

Abstract

The application provides a hidden support structure for limiting deformation of a passive area of a base and a construction method, and relates to the technical field of building construction, to solve the technical problem that the deformation of the enclosure structure is too large due to the time-space effect during the excavation process of the existing foundation pit engineering in soft soil areas. The structure comprises a foundation pit supporting assembly and a support structure arranged in the foundation pit. The foundation pit supporting assembly comprises a foundation pit enclosure structure and a corbel arranged on the top of the foundation pit enclosure structure. A first groove is arranged close to the foundation pit enclosure structure, and a surrounding purlin is arranged in the first groove. A second groove is arranged close to the circumferential side of the support structure, and a ring beam is arranged in the second groove. The longitudinal stress reinforcement of the ring beam wraps the support structure. A support beam is arranged between the surrounding purlin and the ring beam. The beneficial effect of the application is that the early displacement deformation of the enclosure structure is limited by the hidden beam support, the stability of the enclosure structure of the foundation pit is improved, and a safe and reliable working environment and a harmonious surrounding environment are provided for the construction of the underground structure.

Description

Technical Field

[0001] The present invention relates to the technical field of building construction, and in particular to a concealed support structure for limiting deformation in a passive area of ​​a base and a construction method. Background Art

[0002] During the excavation process of foundation pit projects in soft soil areas, the retaining structure often deforms excessively due to time and space effects.

[0003] The main reason for this phenomenon is that the bottom of the foundation pit in the soft soil area is composed of silty and weak soil, which has low strength and large compression deformation, resulting in a serious lack of lateral resistance in the passive zone of the foundation pit. In addition, the construction and maintenance period of the foundation slab is long, and the deformation of the foundation pit retaining structure is too large, which often has a huge impact on the collapse of the foundation pit or damage to surrounding environmental facilities. In addition, the base fails to form a support body in the early stage of foundation pit excavation. The weak soil in the passive zone alone cannot resist the lateral displacement and deformation of the retaining structure. Before the foundation slab is poured, the retaining structure has already caused significant deformation. Summary of the Invention

[0004] The present invention aims to provide a concealed support structure and construction method for limiting deformation in the passive zone of a foundation, thereby resolving the prior art technical problem of excessive deformation of retaining structures during excavation in soft soil areas due to spatiotemporal effects. The various technical effects achieved by the preferred technical solution among the various technical solutions provided by the present invention are detailed below.

[0005] To achieve the above objectives, the present invention provides the following technical solutions:

[0006] The present invention provides a concealed support structure for limiting deformation in a passive area of ​​a base, comprising a foundation pit support assembly and a support structure arranged in the foundation pit, wherein:

[0007] The foundation pit support assembly includes a foundation pit retaining structure and a crown beam arranged on the top of the foundation pit retaining structure, a first groove is arranged close to the foundation pit retaining structure, and a purlin is arranged in the first groove;

[0008] A second groove is provided close to the peripheral side of the support structure, a ring beam is provided in the second groove, and longitudinal stress reinforcements of the ring beam wrap the support structure;

[0009] A top support beam is provided between the surrounding purlin and the ring beam.

[0010] Preferably, the supporting structure adopts a hollow structure, a grouting hole is set at the top of the supporting structure, and multiple slurry outlet holes are set on the circumference of the supporting structure. The multiple slurry outlet holes are arranged in a plum blossom shape along the circumference of the supporting structure at a distance of less than 500 mm from the top of the supporting structure.

[0011] Preferably, it also includes a resistance plate, which is arranged on one side of the support structure, located above the slurry outlet, and has a thickness of not less than 20 mm.

[0012] Preferably, the top elevation of the support structure is more than 200 mm lower than the base, and the multiple support structures arranged in a row are all arranged obliquely, with the inclination angle of the support structure to the vertical direction being 10°-20°.

[0013] Preferably, the top elevation of the support structure is more than 200 mm lower than the base, and the multiple support structures arranged in a row are arranged in an inclined and vertically spaced manner, and the inclination angle of the support structure to the vertical direction is 10°-20°.

[0014] Preferably, the supporting structure is made of a steel pipe with a diameter of not less than DN150, the slurry outlet hole is arranged on the side wall of the steel pipe, and the diameter of the slurry outlet hole is 3mm-5mm.

[0015] Preferably, it also includes an encapsulation structure, the supporting top beam is arranged in the encapsulation structure, and the encapsulation thickness of the encapsulation structure is not less than 100 mm.

[0016] Preferably, it further comprises a foundation cushion layer, wherein the foundation cushion layer is arranged on the top of the ring beam, the surrounding purlin and the supporting top beam, and a graded sand and gravel layer is arranged between the foundation cushion layer and the ring beam, the surrounding purlin and the supporting top beam.

[0017] A construction method of the above-mentioned hidden support structure provided in the passive area of ​​the base to limit deformation comprises the following steps:

[0018] S1: Construction of foundation pit support components, including organizing the construction of support components according to the requirements of the foundation pit support design plan, including the construction of the foundation pit retaining structure and the crown beam set on the top of the foundation pit retaining structure;

[0019] S2: Excavation of foundation pit, including organizing the setting and monitoring of foundation pit monitoring points, and carrying out foundation pit dewatering construction at the same time. When the foundation pit meets the excavation conditions, the foundation pit is excavated in layers, sections, and in a balanced and symmetrical manner;

[0020] S3: Construction of the support structure in the pit, including construction of a vertical support structure in the passive area of ​​the pit when the foundation pit excavation meets the conditions for the support structure operation. Cement slurry is injected into the interior of the support structure through grouting holes. The cement slurry can overflow from the slurry outlet holes and seep into the surrounding soil. It solidifies to form a cement slurry that reinforces the surrounding soil and improves the stiffness and friction of the support structure.

[0021] S4: concrete surrounding purlin and ring beam construction, including excavating a first trench and a second trench on both sides of the base of the foundation pit retaining structure and the support structure, and hoisting the bound surrounding purlin and ring beam into the first trench and the second trench, respectively;

[0022] S5: support structure installation, including installing a prefabricated support beam between the surrounding purlin and the ring beam, the support beam being arranged at the center position of the support beam installation embedded part, and ensuring the horizontality of both ends;

[0023] S6: prestress application, applying a pre-topping force by a jack to ensure that the support beam tightly supports the surrounding purlin and the ring beam, and then welding the support beam and the support beam installation embedded part at both ends firmly, and then removing the jack;

[0024] S7: concrete encapsulation, pouring encapsulation concrete around the support beam;

[0025] S8: graded gravel backfilling, after the completion of concrete pouring, backfilling graded gravel on the ring beam, the surrounding purlin and the upper part of the support beam, and then repeating the construction of adjacent hidden support structures in sections, and finally connecting the hidden support structures into a whole.

[0026] Preferably, step S4: concrete surrounding purlin and ring beam construction, wherein:

[0027] The cross-sectional size of the first trench and the second trench is set to 500mm x 500mm;

[0028] The cross-sectional size of the surrounding purlin and the ring beam is set to not less than 300mm x 500mm, and the spacing between the surrounding purlin and the ring beam is 3m-5m; the spacing between the support beam installation embedded parts is 2m-5m.

[0029] The present invention provides a concealed support structure for limiting deformation in the passive area of ​​the base, comprising a foundation pit support assembly and a support structure arranged in the foundation pit. A strong support structure system is formed by arranging a support structure, a purlin, a ring beam and a top support beam in the passive area of ​​the foundation pit. During the excavation stage of a deep foundation pit in a soft soil area, the soil above the base is rapidly excavated, the soil load in the pit is unloaded, the pressure on both sides of the foundation pit loses balance, and the soil in the passive area of ​​the pit is compressed. However, the elastic modulus of the soft soil in the passive area of ​​the pit is low, the compression amount is large, and it is difficult to resist the strong lateral pressure outside the pit, causing the deformation of the foundation pit retaining structure to continue to grow rapidly, bringing harm to the foundation pit and the surrounding environment. The pressure outside the pit is balanced by this concealed support structure, the deformation of the foundation pit is reduced, and the safety of the foundation pit and the surrounding environment is improved. The segmented skipping bin can be constructed simultaneously with the earthwork excavation, which does not affect the construction period of the basement structure. The construction process is simple to operate, mature and stable, safe and reliable, and can limit the deformation of the foundation pit and improve the safety of the foundation pit structure and the surrounding environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 This is a schematic structural diagram of an embodiment of a hidden support structure for limiting deformation provided in a passive area of ​​a substrate according to the present invention;

[0032] Figure 2 yes Figure 1 Schematic diagram of the cross-sectional structure;

[0033] Figure 3 This is a schematic structural diagram of the supporting structure of the present invention, which is provided in the passive area of ​​the base to limit deformation;

[0034] Figure 4 It is a schematic top view of the supporting structure of the concealed supporting structure for limiting deformation in the passive area of ​​the base according to the present invention.

[0035] In the figure: 1. Foundation pit support assembly; 2. Support structure; 3. Purlin; 4. Ring beam; 5. Top beam; 6. Resistance plate; 7. Cement slurry; 8. Encapsulation structure; 9. Foundation cushion layer; 10. Graded sand and gravel layer; 11. Foundation pit retaining structure; 12. Crown beam; 13. Foundation; 21. Grouting hole; 22. Grouting hole. DETAILED DESCRIPTION

[0036] To make the objectives, technical solutions, and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other implementations obtained by those of ordinary skill in the art without inventive effort are within the scope of protection of the present invention.

[0037] The invention provides a concealed support structure arranged in a passive area of ​​a base to limit deformation, which is particularly suitable for support and reinforcement in a soft soil foundation pit. Figure 1 is a plan view of this embodiment, Figure 2 Schematic diagram of the cross-sectional structure of this embodiment, as shown in FIG. Figure 1 and Figure 2 As shown, it includes a foundation pit support assembly 1 and a support structure 2 arranged in the foundation pit.

[0038] Among them, the foundation pit support assembly 1 includes a foundation pit retaining structure 11 and a crown beam 12 arranged on the top of the foundation pit retaining structure 11. A first groove is arranged close to the foundation pit retaining structure 11, and a purlin 3 is arranged in the first groove, which improves the stability of the retaining structure and reliably guarantees the safety of the foundation pit support.

[0039] A second groove is provided close to the periphery of the support structure 2, within which a ring beam 4 is provided, with the longitudinal tension reinforcement of the ring beam 4 wrapping around the support structure 2; a supporting top beam 5 is provided between the surrounding purlin 3 and the ring beam 4. Based on the characteristics and patterns of foundation pit deformation, during the excavation process, the support structure 2, surrounding purlin 3, ring beam 4, and supporting top beam 5 are provided in the passive zone of the foundation pit to form a strong supporting structural system. By adding a hidden support structure to the lower part of the pit floor at an early stage, a hidden beam support structure is formed at the initial stage of sudden deformation of the foundation pit, effectively reducing the deformation rate of the foundation pit and effectively solving the problem of large early foundation pit deformation due to the lack of a supporting structure in the soft soil area.

[0040] This concealed support structure, which is located in the passive zone of the base to limit deformation, includes a foundation pit support assembly 1 and a support structure 2 located within the foundation pit. By arranging the support structure 2, purlins 3, ring beams 4, and top support beams 5 in the passive zone of the foundation pit, a strong support structure system is formed. During the excavation phase of deep foundation pits in soft soil areas, the soil above the base is rapidly excavated, the load on the soil in the pit is unloaded, and the pressure on both sides of the foundation pit loses balance. The soil in the passive zone of the pit is compressed. However, the soft soil in the passive zone of the pit has a low elastic modulus and a large compression, making it difficult to resist the strong lateral pressure outside the pit. This causes the deformation of the foundation pit retaining structure to continue to grow rapidly, posing a threat to the foundation pit and the surrounding environment. This concealed support structure balances the pressure outside the pit, reduces the deformation of the foundation pit, and improves the safety of the foundation pit and the surrounding environment. The construction process can be carried out simultaneously with the excavation of the earthwork in a segmented manner without affecting the construction period of the basement structure. The construction process is simple to operate, mature, stable, safe and reliable, and can limit the deformation of the foundation pit and improve the safety of the foundation pit structure and the surrounding environment.

[0041] As an optional implementation, Figure 3 Schematic diagram of the supporting structure in this embodiment. Figure 3 As shown, the supporting structure 2 is a micro pile with a hollow structure. A grouting hole 21 is set at the top of the supporting structure 2, and a plurality of slurry holes 22 are set on the peripheral side of the supporting structure 2. The plurality of slurry holes 22 are arranged in a plum blossom shape along the peripheral side of the supporting structure 2 below 500 mm from the top of the supporting structure 2, so as to make it easier for the cement slurry to overflow through the slurry holes 22 and infiltrate into the surrounding soil.

[0042] In this embodiment, the support structure 2 is made of a steel pipe with a diameter of not less than DN150, and the slurry outlet hole 22 is arranged on the side wall of the steel pipe. The diameter of the slurry outlet hole 22 is 3mm-5mm.

[0043] Figure 4 is a schematic diagram of the top view of the support structure in this embodiment, as shown in Figure 4 As shown, it also includes a resistance plate 6, which is arranged on one side of the support structure 2, located above the slurry outlet hole 22, and has a thickness of not less than 20 mm.

[0044] During use, cement slurry is injected into the supporting structure 2, i.e., the pile body, through the grouting holes 21 set at the top of the supporting structure 2. The cement slurry can overflow through the slurry outlet holes 22 and seep into the surrounding soil, solidifying to form cement slurry 7 to reinforce the surrounding soil. It is combined with a resistance plate 6 with a thickness of not less than 20 mm connected to the upper part of the supporting structure 2 to improve the stiffness and friction of the pile body.

[0045] As an optional embodiment, the top elevation of the support structure 2 is more than 200 mm lower than the base, and multiple support structures 2 arranged in a row are arranged at an angle, and the inclination angle of the support structure 2 to the vertical direction is 10°-20° to improve the support stability of the overall structure.

[0046] As an optional embodiment, the top elevation of the support structure 2 is more than 200 mm lower than the base, and multiple support structures 2 arranged in a row are arranged in an inclined and vertically spaced manner. The inclination angle of the inclined support structure 2 to the vertical direction is 10°-20° to improve the support stability of the overall structure.

[0047] As an optional embodiment, an encapsulation structure 8 is further included, and the supporting top beam 5 is arranged in the encapsulation structure 8. The wrapping thickness of the encapsulation structure 8 is not less than 100 mm, and the supporting top beam 5 is effectively protected by the encapsulation structure 8.

[0048] As an optional embodiment, a foundation cushion layer 9 is further included. The foundation cushion layer 9 is arranged on the top of the ring beam 4, the surrounding purlin 3 and the supporting top beam 5, and a graded sand and gravel layer 10 is arranged between the foundation cushion layer 9 and the ring beam 4, the surrounding purlin 3 and the supporting top beam 5.

[0049] The above-mentioned construction method of a concealed support structure set in the passive zone of the base to limit deformation is suitable for foundation pit projects in soft soil areas and with large base deformation. Construction can be carried out in sections and interspersed with earth excavation. Construction can be carried out as soon as possible during earth excavation to form a support structure in time and minimize the exposure time without support.

[0050] The specific steps include:

[0051] S1: Construction of the foundation pit support assembly 1, including organizing the construction of the support assembly according to the requirements of the foundation pit support design plan, including the construction of the foundation pit retaining structure 11 and the crown beam 12 set on the top of the foundation pit retaining structure 11;

[0052] S2: Excavation of foundation pit, including organizing the setting and monitoring of foundation pit monitoring points, and carrying out foundation pit dewatering construction at the same time. When the foundation pit meets the excavation conditions, the foundation pit is excavated in layers, sections, and in a balanced and symmetrical manner;

[0053] S3: Construction of the supporting structure in the pit, including the construction of the vertical supporting structure 2 in the passive area of ​​the foundation pit when the excavation of the foundation pit meets the operating conditions of the supporting structure 2. Specifically, the supporting structure 2 adopts a steel pipe with a diameter of not less than DN150, and a slurry hole 22 with a diameter of 3mm-5mm is set along the circumference of the supporting structure 2 below 500mm from the top of the supporting structure 2. The slurry holes 22 are arranged in a plum blossom shape.

[0054] Multiple support structures 2 arranged in a row are arranged in an inclined manner (with an inclination angle of 10°-20°), or in a combination of vertical and inclined arrangements, with the top elevation of the support structure at least 200mm below the base. A resistance plate 6 with a thickness of at least 20mm is connected to the upper portion of the micropile steel pipe.

[0055] Cement slurry is injected into the interior of the support structure 2 through the grouting holes 21. The cement slurry can overflow from the slurry outlet holes 22 and penetrate into the surrounding soil. It solidifies to form cement slurry 7 to reinforce the surrounding soil and improve the rigidity and friction of the support structure.

[0056] S4: Construction of concrete purlins and ring beams, including excavating the first trench and the second trench in sections at the base close to the foundation pit retaining structure 11 and the supporting structure 2 on both sides, and hoisting the bound purlins 3 and ring beams 4 into the first trench and the second trench respectively; installing embedded parts of the top beams on the side of the ring beam 4, and the embedded parts of the top beams correspond to the positions of the top beams 5, and then pouring concrete, and concrete with high early strength can be used.

[0057] S5: Installation of the supporting structure, including installing a prefabricated supporting beam 5 between the purlin 3 and the ring beam 4. The supporting beam 5 is arranged at the center of the supporting beam installation embedded parts to ensure that both ends are level;

[0058] S6: Apply prestressing force by using a jack to ensure that the top beam 5 presses the purlin 3 and the ring beam 4 tightly, and weld the top beam 5 to the embedded parts of the top beam at both ends firmly, and then remove the jack;

[0059] S7: Concrete encapsulation: pour encapsulating concrete around the top beam 5, with the thickness of the concrete encapsulation on each side not less than 100 mm;

[0060] S8: After the graded sand and gravel are backfilled and the concrete pouring is completed, the graded sand and gravel are backfilled on the ring beam 4, the surrounding purlin 3 and the supporting top beam 5. The top surface of the graded sand and gravel reaches the bottom of the foundation cushion layer 9. Then the construction is repeated in sections near the hidden support structure, and finally the hidden support structure is connected as a whole.

[0061] The construction method of the concealed support structure set in the passive zone of the base to limit deformation, on the one hand, limits the early displacement and deformation of the retaining structure through the method of concealed beam support, improves the stability of the retaining structure of the foundation pit, and provides a safe and reliable working environment and a harmonious surrounding environment for the construction of the underground structure; on the other hand, the use of concealed beam support at the bottom of the pit to reduce the deformation of the foundation pit can reduce the embedding depth of the retaining piles to a certain extent, which not only limits the early deformation of the foundation pit but also reduces the project investment.

[0062] As an optional implementation method, step S4: during the construction of the concrete purlin and ring beam, the cross-sectional dimensions of the first groove and the second groove are set to 500mm×500mm; the cross-sectional dimensions of the purlin 3 and the ring beam 4 are both set to not less than 300mm×500mm, and the spacing between the purlin 3 and the ring beam 4 is 3m~5m; the spacing between the embedded parts of the supporting top beam 5 is 2m~5m.

[0063] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A concealed support structure provided in the passive area of ​​a substrate to limit deformation, characterized in that: It includes a foundation pit support assembly and a support structure arranged in the foundation pit, wherein: The foundation pit support assembly includes a foundation pit retaining structure and a crown beam arranged on the top of the foundation pit retaining structure, a first groove is arranged close to the foundation pit retaining structure, and a purlin is arranged in the first groove; A second groove is provided close to the peripheral side of the support structure, a ring beam is provided in the second groove, and longitudinal stress reinforcements of the ring beam wrap the support structure; A supporting top beam is provided between the surrounding purlin and the ring beam; The top elevation of the support structure is more than 200 mm lower than the base, and the multiple support structures arranged in a row are arranged obliquely or arranged in an oblique, vertically spaced arrangement, and the inclination angle of the support structure to the vertical direction is 10°-20°; It also includes an encapsulation structure, wherein the supporting top beam is arranged in the encapsulation structure, and the encapsulation thickness of the encapsulation structure is not less than 100 mm; Also includes a foundation cushion, which: The foundation cushion layer is arranged on the top of the ring beam, the surrounding purlin and the supporting top beam, and a graded sand and gravel layer is arranged between the foundation cushion layer and the ring beam, the surrounding purlin and the supporting top beam.

2. The hidden support structure for limiting deformation provided in the passive area of ​​the substrate according to claim 1, characterized in that: The support structure adopts a hollow structure, a grouting hole is set at the top of the support structure, and multiple slurry outlet holes are set on the circumference of the support structure. The multiple slurry outlet holes are arranged in a plum blossom shape along the circumference of the support structure at a distance of less than 500 mm from the top of the support structure.

3. The hidden support structure for limiting deformation provided in the passive area of ​​the substrate according to claim 2, characterized in that: It also includes a resistance plate, which is arranged on one side of the support structure, located above the slurry outlet, and has a thickness of not less than 20 mm.

4. The hidden support structure for limiting deformation provided in the passive area of ​​the substrate according to claim 2 or 3, characterized in that: The supporting structure is made of a steel pipe with a diameter of not less than DN150, and the slurry outlet hole is arranged on the side wall of the steel pipe. The diameter of the slurry outlet hole is 3mm-5mm.

5. A construction method for a hidden support structure for limiting deformation in a passive area of ​​a base according to any one of claims 1 to 4, characterized in that: The steps include: S1: Construction of foundation pit support components, including organizing the construction of support components according to the requirements of the foundation pit support design plan, including the construction of the foundation pit retaining structure and the crown beam set on the top of the foundation pit retaining structure; S2: Excavation of foundation pit, including organizing the setting and monitoring of foundation pit monitoring points, and carrying out foundation pit dewatering construction at the same time. When the foundation pit meets the excavation conditions, the foundation pit is excavated in layers, sections, and in a balanced and symmetrical manner; S3: Construction of the support structure in the pit, including construction of a vertical support structure in the passive area of ​​the pit when the foundation pit excavation meets the conditions for the support structure operation. Cement slurry is injected into the interior of the support structure through grouting holes. The cement slurry can overflow from the slurry outlet holes and seep into the surrounding soil. It solidifies to form a cement slurry that reinforces the surrounding soil and improves the stiffness and friction of the support structure. S4: Construction of concrete perimeter purlins and ring beams, including excavating a first trench and a second trench in sections close to the base of the foundation pit retaining structure and the supporting structure on both sides, and hoisting the bound perimeter purlins and ring beams into the first trench and the second trench, respectively; installing embedded mounting parts for the top beams on the sides of the ring beams, with the embedded mounting parts for the top beams corresponding to the positions of the top beams, and then pouring concrete; S5: Installing the supporting structure, including installing the prefabricated supporting beam between the purlin and the ring beam, the supporting beam being arranged at the center of the supporting beam installation embedded part to ensure that both ends are level; S6: applying prestress, applying pre-stressing force by means of a jack, ensuring that the supporting top beam presses the surrounding purlin and the ring beam tightly, and firmly welding the supporting top beam to the supporting top beam mounting embedded parts at both ends, and then withdrawing the jack; S7: Concrete encapsulation, pouring encapsulation concrete around the top beam; S8: After the graded sand and gravel are backfilled and the concrete pouring is completed, the graded sand and gravel are backfilled on the upper part of the ring beam, the surrounding purlin and the supporting top beam. The top surface of the graded sand and gravel reaches the bottom of the foundation cushion layer, and then the construction is repeated in sections near the hidden support structure, and finally the hidden support structure is connected as a whole.

6. The construction method of the hidden support structure for limiting deformation provided in the passive area of ​​the base according to claim 5, characterized in that: Step S4: Construction of concrete purlins and ring beams, wherein: The cross-sectional dimensions of the first groove and the second groove are set to 500 mm×500 mm; The cross-sectional dimensions of the surrounding purlin and the ring beam are both set to be no less than 300mm×500mm, and the spacing between the surrounding purlin and the ring beam is 3m to 5m; the spacing between the embedded parts of the supporting top beam is 2m to 5m.

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