Deep foundation pit supporting and foundation foundation collaborative construction method suitable for soft soil foundation

Abstract

The present application relates to the technical field of building engineering, especially to a deep foundation pit supporting and foundation base collaborative construction method suitable for soft soil foundation, which comprises foundation pit enclosure structure construction, steel pipe concrete column construction, prestressed anchor cable construction, steel pipe concrete column and concrete support system perfection, inner lining wall construction, settlement supplementary adjustment layer construction, bottom plate construction, integral structure sequential construction and underground space pipeline layer construction. The present application is based on the soil mass side limit consolidation theory, soil pressure compensation principle and composite foundation mattress layer settlement adjustment theory, and proposes a new method of deep foundation pit supporting and foundation base collaborative design and construction. With the aid of the bearing capacity of the supporting structure outer wall and support lattice column, through the multi-channel convex rib embedded fixation, the new design concept and method of deep foundation pit supporting and foundation base collaborative design and construction effectively solves the problems of high foundation treatment cost and long cycle in the deep foundation pit engineering of coastal soft soil foundation.

Description

Technical Field

[0001] This invention relates to the field of building engineering technology, and in particular to a method for the coordinated construction of deep foundation pit support and foundation for soft soil foundations. Background Technology

[0002] In large and medium-sized deep foundation pit projects, most are high-rise buildings. High-rise buildings usually require the foundation to have high bearing capacity, low settlement and uniform settlement performance. In other words, the foundation is required to withstand huge vertical loads, strictly control settlement and ensure uniform settlement, prevent structural cracking and tilting, and avoid affecting use and safety.

[0003] The foundation treatment method for high-rise buildings is usually selected based on geological conditions: when the bearing layer is rock or a high-bearing-capacity stratum, a natural foundation is preferred, which is low in cost and short in construction period; in general, pile foundations are often used in Quaternary strata, which are reliable in quality but moderate in cost; while in coastal soft silt strata, because soft soil has the characteristics of low strength, high compressibility, uneven settlement, poor permeability and significant rheology, it usually causes large settlement under load, which is difficult to withstand the huge load of high-rise buildings, and is prone to foundation instability, affecting the normal use of the building.

[0004] Due to the uneven composition and structure of soft soil, the resulting differential settlement can cause structural damage; furthermore, soft soil drains and consolidates slowly, requiring a long time for settlement stabilization, which affects the construction period. Current technologies for treating coastal soft soil foundations largely rely on traditional methods such as stress dissipation techniques, composite foundations, and pipe pile foundations, which suffer from high costs and long construction periods.

[0005] Not only is foundation treatment engineering in soft soil areas difficult and expensive, but the support engineering for foundation pits is also extremely difficult, risky, and costly. The combined cost of foundation pit support and foundation treatment accounts for about one-third of the total project cost, becoming a major pain point in the project.

[0006] It is generally believed that the retaining structure mainly enhances the stability of the foundation pit, but has limited effect on improving the bearing capacity of soft soil foundations and cannot fundamentally solve its problems of low bearing capacity and high compressibility; natural soft soil foundations cannot meet the high requirements of high-rise buildings for foundations and must be reinforced. Summary of the Invention

[0007] To address the challenges of high costs and long construction periods in deep foundation pit engineering on soft soil foundations in coastal areas, this invention provides a method for the coordinated construction of deep foundation pit support and foundation for soft soil foundations.

[0008] The present invention provides a method for the coordinated construction of deep foundation pit support and foundation for soft soil foundations, which adopts the following technical solution: S1. Construction of the foundation pit retaining structure, specifically including: delineating the construction area around the foundation pit, first carrying out the construction of the first trench section, and then carrying out the construction of the second trench section. S2. Construction of steel-concrete composite columns, specifically including: steel-concrete composite columns are evenly arranged within the foundation pit of the diaphragm wall, ensuring that their length is consistent with the length of the diaphragm wall, and shear studs are fully welded to the outside of the steel pipes within the excavation depth of the foundation pit. S3. Construction of prestressed anchor cables includes: during the fabrication of the diaphragm wall reinforcement cage, steel sleeves are precisely embedded inside as reserved prestressed anchor cable ducts. After the diaphragm wall is excavated to the corresponding depth, the reserved ducts are cleaned and prestressed anchor cables are constructed one by one at the joint position of each trench section. First, the anchor cable is inserted through the reserved duct, and then the tensioning operation is carried out. After tensioning to the design stress value, the duct is grouted in a timely manner. S4. The steel-concrete composite column and concrete support system are complete, specifically including: after the excavation around the steel-concrete composite column, first clean the soil on the steel pipe and shear nails, and at a position slightly lower than the basement floor slab structure, in conjunction with the reserved steel bars of the diaphragm wall, first weld them to the shear nails, then tie and weld the steel reinforcement skeleton, and then pour concrete to form a reinforced concrete support beam. After welding the steel bars of the reserved ring beam of the diaphragm wall and pouring concrete, an overall frame system is formed. S5. Construction of the inner lining wall, specifically including: On the inner side of the diaphragm wall, the inner lining wall is constructed in reverse order by excavating layer by layer, and grouting pipes, protrusions, grooves and tie bars are reserved. After the inner lining wall reaches a certain strength, the main structural wall is constructed in the direction on its inner side. The diaphragm wall and the inner lining wall are connected into a whole by using the protrusions, tie bars and the main structural column wrapped with steel pipe concrete column reserved on the inner lining wall. S6. Construction of settlement supplement and adjustment layer, specifically including: before the construction of the base slab, leveling the soil layer below the base slab and then laying geotextile, laying geogrid on top of the geotextile, and then laying sand mattress. S7. Base slab construction, specifically including: embedding the base slab into the inner lining wall through the groove reserved in the inner lining wall, and setting a waterproof structural layer at the contact position between the base slab and the steel pipe concrete column; S8. The overall structure is constructed sequentially, which specifically includes: based on the base slab, the main underground structure is constructed in accordance with the design drawings. S9. Construction of underground pipeline layer, specifically including: installing various pipelines around the underground space and within the lowest basement level according to the design location; after the pipeline installation is completed, setting up a dedicated pumping station to connect the pipelines to the municipal pipeline network.

[0009] Preferably, two prestressed anchor cable ducts are reserved in each plane, namely an outer reserved hole and an inner reserved hole, and multiple ducts are set vertically.

[0010] By adopting the above technical solutions, this construction method uses diaphragm walls, inner lining walls, anchor cables, steel-concrete composite columns, and the main structure to control the deformation of the foundation pit and bear the structural load as a whole. Combined with the bottom slab and coarse sand layer to regulate settlement, it solves the problems of low bearing capacity and uneven settlement of soft soil foundations. It is suitable for the construction of deep foundation pit projects in coastal soft and uniform strata. Compared with traditional composite foundations or pile foundations, it can significantly reduce the cost of foundation treatment. Based on the theory of lateral consolidation, it shortens the foundation treatment period. The diaphragm walls, inner lining walls, steel-concrete composite columns, prestressed anchor cables, and the main structure form an integrated structure, which, combined with the bottom slab and coarse sand layer to regulate settlement, solves the problems of low strength and uneven settlement of soft soil foundations. It is specifically designed for coastal soft soil foundation pits and specifically addresses the characteristics of soft soil such as high compressibility and low permeability.

[0011] Preferably, if the length of the diaphragm wall can exceed the thickness of the silty soil layer, then exceeding that thickness shall be the standard; if it cannot exceed that thickness, then the length must be more than three times the depth of the foundation pit.

[0012] Preferably, the distance between the steel-concrete composite column and the edge of the diaphragm wall is 1 / 2 of the spacing between the steel-concrete composite columns.

[0013] Preferably, adjacent geogrids and sand mats are laid as one layer, and a total of three layers are laid in the same laying sequence.

[0014] Preferably, a grouting pipe is installed below the lowest settlement adjustment layer and connected to the grouting pipe between the grouting pipe and the diaphragm wall to form the same system, with grouting pipes and check valves installed separately.

[0015] Preferably, the base slab is designed and constructed to be twice the thickness of a standard high-rise residential base slab. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the distribution of steel-concrete composite columns according to an embodiment of the present invention.

[0017] Figure 2 This is a plan view of the prestressed anchor cable reserved hole in the diaphragm wall reinforcement cage according to an embodiment of the present invention.

[0018] Figure 3 This is an elevation view of the prestressed anchor cable reserved hole in the diaphragm wall reinforcement cage according to an embodiment of the present invention.

[0019] Figure 4 This is an elevation view of the diaphragm wall and the steel-concrete composite column according to an embodiment of the present invention.

[0020] Figure 5 This is an elevation view of the main structure and base plate of an embodiment of the present invention.

[0021] Figure 6 This is a plan view of the intersection of the support beam and the steel-concrete composite column according to an embodiment of the present invention.

[0022] Explanation of reference numerals in the attached drawings: 1. First trench section; 2. Second trench section; 3. Diaphragm wall; 4. Diaphragm wall reinforcement cage; 5. Outer reserved hole; 6. Inner reserved hole; 7. Crown beam; 8. Steel pipe concrete column; 9. Shear stud; 10. Ring beam; 11. Support beam; 12. Inner lining wall; 13. Protruding rib; 14. Grouting pipe; 15. Groove; 16. Geogrid; 17. Sand mattress; 18. Base plate; 19. Main structural wall; 20. Main structural column. Detailed Implementation

[0023] The following combination Figures 1-6 The present invention will be described in further detail below.

[0024] This invention discloses a method for the coordinated construction of deep foundation pit support and foundation for soft soil foundations, comprising the following: S1. Construction of the foundation pit retaining structure, specifically including: demarcating the construction area around the foundation pit, constructing the diaphragm wall 3 using construction equipment, and accurately measuring the thickness of the silty soil layer and the depth of the foundation pit before construction to ensure that the length of the diaphragm wall 3 meets the following requirements: if it can exceed the thickness of the silty soil layer, then exceeding that thickness shall be the standard; if it cannot exceed it, then the length must be more than three times the depth of the foundation pit; first, construct the first trench section 1, and then construct the second trench section 2. The corner trench section is one of the second trench sections 2; during construction, strictly control the verticality of the wall and the quality of concrete pouring to form a reliable lateral support system for the foundation pit, providing safety assurance for subsequent construction, and constructing the capping beam 7 at the top of the diaphragm wall 3.

[0025] S2. Construction of steel-concrete composite columns 8 specifically includes: Immediately after the completion and sufficient strength of the diaphragm wall 3, construction of the steel-concrete composite columns 8 shall commence. The steel-concrete composite columns 8 shall be evenly distributed within the foundation pit area of ​​the diaphragm wall 3, with the distance from the edge of the diaphragm wall 3 being 1 / 2 of the spacing between the steel-concrete composite columns 8. According to the design location, the steel-concrete composite columns 8 shall be fixed using drilling or pre-embedding methods. The diameter of the steel-concrete composite columns 8 shall not be less than 1.2m, and the wall thickness of the steel pipe shall not be less than 12mm, ensuring their verticality and stability. During the construction of the steel-concrete composite columns 8, their length shall be consistent with the length of the diaphragm wall 3. Within the excavation depth of the foundation pit, the outer side of the steel pipe shall be fully welded with shear nails 9, each 100mm long, 16mm in diameter, and spaced 150mm apart. The entire pipe shall be filled with concrete of the same strength as the main structure of the basement to ensure its load-bearing capacity.

[0026] S3. Prestressed anchor cable construction specifically includes: During the fabrication stage of the diaphragm wall reinforcement cage 4, steel sleeves with a diameter of 100mm are precisely pre-embedded inside the diaphragm wall reinforcement cage 4 within the excavation area of ​​the foundation pit as reserved prestressed anchor cable ducts, according to design requirements; two are reserved in each plane, namely the outer reserved hole 5 and the inner reserved hole 6, with a vertical spacing of about 2m; after the diaphragm wall 3 is excavated to the corresponding depth, the reserved ducts are cleaned and prestressed anchor cables are constructed one by one at the joint position of each trench segment; the anchor cables are first inserted through the reserved ducts, and then tensioning is carried out. After tensioning to the design stress value, the ducts are grouted in a timely manner; the prestressed anchor cables and grouting not only enable the diaphragm wall 3 to form an integral load-bearing structure, enhance the lateral connection between the walls, and further improve the stability of the foundation pit, but also enhance the cleaning of mud skin between trench segments, increase the friction between trench segments, and improve the seepage prevention performance.

[0027] S4. The steel-concrete composite column 8 and the concrete support system are complete, specifically including: After excavation around the steel-concrete composite column 8, the soil on the steel pipes and shear nails 9 is first cleaned. At a position slightly lower than the basement floor slab structure, in conjunction with the reserved reinforcing bars of the diaphragm wall 3, the shear nails 9 are first welded, then the reinforcing bar skeleton is tied and welded, and then concrete is poured to form a reinforced concrete support beam 11. After welding the reinforcing bars of the reserved ring beam 10 of the diaphragm wall 3 and pouring concrete, an overall frame system is formed. The steel-concrete composite column 8, the support beam 11, and the diaphragm wall 3 together form an overall frame system, which is prepared for the stress support after the foundation pit is excavated and for bearing the vertical load of the main structure. In subsequent construction, the shear nails 9 on the outside of the steel pipe will be welded to the reinforcing bars of the main frame structure of the basement to bear the load, so that the two form a solid whole. At the contact position between the steel-concrete composite column 8 and the base slab 18, a waterproof structural layer, such as waterproof membrane or waterproof coating, is laid according to the waterproof design requirements to prevent groundwater from seeping through the contact gaps.

[0028] S5. Construction of the inner lining wall 12 includes: constructing the inner lining wall 12 in reverse order, using a layer-by-layer excavation method inside the diaphragm wall 3, simultaneously with the excavation progress; during construction, strictly adhering to the design dimensions for binding the reinforcing steel of the inner lining wall 12, and pre-reserving grouting pipes 14, protruding ribs 13, grooves 15, and tie bars; the protruding ribs 13 are approximately 150mm thick, approximately 200mm high, and spaced every 3m; pouring concrete to form the inner lining wall 12, approximately 500mm thick, tightly integrating it with the diaphragm wall 3 to form an integral structure. The grouting pipe 14 is reserved in 12 to solve the leakage and reinforcement problems between the two walls in the future; the construction of the inner lining wall 12 and the construction of the supporting beam 11 are coordinated with each other and form an integral structure through steel reinforcement connection and other methods; after the inner lining wall 12 reaches a certain strength, the main structural wall 19 is constructed on its inner side. The ground diaphragm wall 3 and the inner lining wall 12 are connected into a whole by the pre-reserved protrusions 13, tie bars and the main structural column 20 wrapped by the steel pipe concrete column 8, and finally form a "three-wall integrated" structure to improve the stability and integrity of the overall structure.

[0029] S6. Construction of the settlement supplement and adjustment layer specifically includes: before the construction of the base slab 18, leveling the soil layer below the base slab 18; firstly, laying a layer of geotextile to ensure that it covers the entire area of ​​the base slab 18 and that the overlap meets the specifications; laying a layer of geogrid 16 on top of the geotextile and filling the gaps between the geogrids with medium-coarse sand; then laying a sand mattress 17, which is made of geotextile and has a specification of 2m×2m×0.2m, filled with medium-coarse sand, ensuring that the sand mattress 17 is tightly squeezed together during laying; laying three layers in the same order to form an overall settlement supplement and adjustment layer; below the bottom settlement adjustment layer, installing grouting pipes 14 according to the design requirements and connecting them to the grouting pipes 14 between the bottom and the diaphragm wall 3 to form the same system, and installing grouting pipelines and check valves respectively to prepare for later settlement adjustment.

[0030] S7. Construction of the base slab 18 includes: the base slab 18 is designed and constructed to be twice the thickness of a typical high-rise residential base slab; first, the reinforcing bars of the base slab 18 are tied to ensure that the spacing of the reinforcing bars and the thickness of the protective layer meet the requirements; then, the base slab 18 is embedded into the inner lining wall 12 through the groove 15 reserved in the inner lining wall 12 to make the two tightly connected; a waterproof structural layer is set at the contact position between the base slab 18 and the steel pipe concrete column 8 to prevent leakage; finally, concrete is poured, vibrated to compact, and cured to the design strength. The increased rigidity of the base slab 18 and the earth pressure compensation principle formed by the deep basement are used to reduce and balance the settlement caused by additional stress.

[0031] S8. The overall structure is constructed in sequence, specifically including: after the base plate 18 reaches the design strength, the main underground structure is constructed according to the design drawings based on the base plate 18; during the construction process, it is ensured that the underground structure and the inner lining wall 12 are effectively connected through the reserved protruding ribs 13 and tie bars, and the construction is carried out layer by layer upward in a sequential manner until the pouring and curing of the main underground structure is completed, so as to ensure the integrity and stability of the underground structure.

[0032] S9. Construction of underground space pipeline layer, specifically including: planning and organizing the area around the underground space after the completion of the main underground structure construction; installing various pipelines in the area around the underground space and the lowest basement according to the design location; setting up a dedicated pumping station after the pipeline installation is completed, and connecting the pipelines to the municipal pipeline network through the pumping station to realize the independent operation and management of underground space pipelines and make reasonable use of underground space resources.

[0033] The method for deep foundation pit support and foundation construction in conjunction with soft soil foundations according to embodiments of the present invention has the following advantages: 1. System Design Based on Multi-Theory Synergy: This method is based on the theory of lateral consolidation of soil, the principle of earth pressure compensation, the settlement regulation theory of composite foundation cushion layer, and the settlement regulation theory. It innovatively integrates multiple theories into a foundation treatment system, proposing a new method for the coordinated design and construction of deep foundation pit support and foundation. By leveraging the bearing capacity of the external wall of the support structure and the steel-concrete composite column 8, and through the embedded reinforcement of multiple convex ribs 13 to share the self-weight of the structure, a new design concept and method for the coordinated design and construction of deep foundation pit support and foundation is proposed. Through the synergistic effect of various theories, the problems of low bearing capacity and uneven settlement of soft soil foundation are solved from different angles, rather than the application of a single theory, forming a system-level optimization scheme, breaking through the limitation of the single theoretical application of traditional foundation treatment methods. 2. Actively controlled foundation pit retaining structure: The main function of traditional retaining structures is to ensure the safety of foundation pit construction, with limited improvement on the characteristics of soft soil foundations. In this method, the design length of the diaphragm wall 3 is subject to strict requirements, and it is combined with the setting of prestressed anchor cables. Anchor cable ducts are reserved when the diaphragm wall steel cage 4 is made. After excavation, the anchor cables are installed, tensioned, and grouted, so that the diaphragm wall 3 forms an integral structural force system. This method of strengthening the connection between the trench sections of the diaphragm wall 3 not only enhances the stability of the foundation pit, but also improves the bearing capacity of the soft soil foundation. 3. Rigid-Flexible Co-construction System: The "three-wall integration" structure formed by the steel-concrete composite column 8, the concrete support system, the inner lining wall 12, and the diaphragm wall 3 embodies the design concept of rigid-flexible coordination. The steel-concrete composite column 8 uses steel pipes with shear studs 9 welded to the outside, forming an integral frame system with the support beam 11 and the pre-reserved reinforcement in the diaphragm wall 3, enhancing the rigidity of the structure. The inner lining wall 12 is constructed using the reverse construction method, forming an integral whole with the support beam 11, and is connected to the main structural wall 19 through pre-reserved protrusions 13, tie bars, and the main structural column 20, forming a flexible connection. This rigid-flexible system can better adapt to the deformation characteristics of soft soil foundations, improving the overall structure's adaptability to soft soil foundations, which is different from traditional single-structure foundation treatment methods. 4. Dynamically Adjustable Settlement Control: A settlement adjustment layer is set up, consisting of geotextile, geogrid 16, and sand mattress 17, with a total of three layers laid. It is laid before the construction of the base slab 18. The bottom layer is equipped with grouting pipe 14, which is in the same system as the wall grouting pipe 14. Grouting pipelines and check valves are set separately. This design allows for dynamic adjustment through grouting and other methods based on actual settlement differences in the later stages. It changes the problem of traditional foundation treatment being a one-time design that is difficult to adjust flexibly according to actual settlement conditions, and provides an effective solution for long-term settlement control of soft soil foundations.

[0034] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for coordinated construction of deep foundation pit support and foundation for soft soil foundations, characterized in that, Includes the following: S1. Construction of the foundation pit retaining structure, specifically including: delineating the construction area around the foundation pit, first carrying out the construction of the first trench section (1), and then carrying out the construction of the second trench section (2); S2, Construction of steel pipe concrete column (8), specifically including: steel pipe concrete column (8) is evenly arranged within the foundation pit of diaphragm wall (3) to ensure that its length is consistent with the length of diaphragm wall (3), and shear nails (9) are fully welded to the outside of the steel pipe within the excavation depth of the foundation pit. S3. Construction of prestressed anchor cables, specifically including: during the fabrication stage of the diaphragm wall steel cage (4), a steel sleeve is precisely embedded inside as a reserved prestressed anchor cable channel. After the diaphragm wall (3) is excavated to the corresponding depth, the reserved channel is cleaned and the prestressed anchor cable is constructed one by one at each joint position of each trench section. First, the anchor cable is inserted through the reserved channel, and then the tensioning operation is carried out. After tensioning to the design stress value, the channel is grouted in time. S4. The steel pipe concrete column (8) and concrete support system are complete, specifically including: after the excavation around the steel pipe concrete column (8), first clean the soil on the steel pipe and shear nail (9), and at a position slightly lower than the basement floor structure, in conjunction with the reserved steel bars of the diaphragm wall (3), first weld them to the shear nail (9), then tie and weld the steel bar skeleton, and then pour concrete to form a reinforced concrete support beam (11), and after welding the steel bars of the reserved ring beam (10) of the diaphragm wall (3) and pouring concrete, an overall frame system is formed. S5. Construction of the inner lining wall (12) includes: on the inner side of the diaphragm wall (3), the inner lining wall (12) is constructed in reverse order by excavating layer by layer, and grouting pipes (14), protrusions (13), grooves (15) and tie bars are reserved; after the inner lining wall (12) reaches a certain strength, the main structural wall (19) is constructed in the direction of its inner side, and the diaphragm wall (3) and the inner lining wall (12) are connected into a whole by using the protrusions (13), tie bars and the main structural column (20) wrapped by the steel pipe concrete column (8) reserved on the inner lining wall (12); S6. Construction of settlement supplement and adjustment layer, specifically including: before the construction of the bottom plate (18), the soil layer below the bottom plate (18) is leveled and then geotextile is laid, geogrid (16) is laid on top of the geotextile, and then sand mattress (17) is laid. S7. Construction of the base plate (18) includes: embedding the base plate (18) into the inner lining wall (12) through the groove (15) reserved in the inner lining wall (12), and setting a waterproof structural layer at the contact position between the base plate (18) and the steel pipe concrete column (8). S8. The overall structure is constructed in sequence, which specifically includes: based on the base plate (18), the main underground structure is constructed in accordance with the design drawings; S9. Construction of underground pipeline layer, specifically including: installing various pipelines according to the design location around the underground space and within the lowest basement level. After the pipeline installation is completed, a pumping station is set up to connect the pipelines to the municipal pipeline network.

2. The method for coordinated construction of deep foundation pit support and foundation for soft soil foundations according to claim 1, characterized in that: Two prestressed anchor cable ducts are reserved in each plane, namely an outer reserved hole (5) and an inner reserved hole (6), and multiple ducts are set vertically.

3. The method for coordinated construction of deep foundation pit support and foundation for soft soil foundations according to claim 1, characterized in that: If the length of the diaphragm wall (3) can exceed the thickness of the silty soil layer, then the standard is to exceed the thickness. If it cannot exceed the thickness, then the length must be more than three times the depth of the foundation pit.

4. The method for coordinated construction of deep foundation pit support and foundation for soft soil foundations according to claim 1, characterized in that: The distance between the steel-concrete composite column (8) and the edge of the diaphragm wall (3) is 1 / 2 of the spacing between the steel-concrete composite columns (8).

5. The method for coordinated construction of deep foundation pit support and foundation for soft soil foundations according to claim 1, characterized in that: Adjacent geogrids (16) and sand mattresses (17) are laid as one layer, and three layers are laid in the same laying sequence.

6. The method for coordinated construction of deep foundation pit support and foundation for soft soil foundations according to claim 1, characterized in that: A grouting pipe (14) is installed below the lowest settlement adjustment layer and connected to the grouting pipe (14) between the ground wall (3) to form the same system. A grouting pipe (14) and a check valve are installed respectively.

7. The method for coordinated construction of deep foundation pit support and foundation for soft soil foundations according to claim 1, characterized in that: The base slab (18) is designed and constructed with a thickness twice that of a typical high-rise residential base slab.

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