Combined tower crane enclosure construction method

Abstract

This invention discloses a combined tower crane retaining wall construction method, comprising the following steps: S1, designing the slope support method around the tower crane and reserving space for the tower crane; S2, constructing within the tower crane's working range, calculating the lateral soil pressure on retaining walls of different depths based on the backfill depth, obtaining the retaining wall thickness corresponding to the retaining wall elevation, and then performing diameter-adjusting construction on the retaining wall; S3, simultaneously installing multi-layer internal bracing structures vertically inside the retaining wall during its construction. This invention solves the problems of large deformation, tipping risk, and large workload associated with traditional technologies through a combined tower crane retaining wall of "retaining piles + arch walls + internal bracing," ensuring the tower crane retaining wall strength meets the lateral pressure of the backfill soil. This allows for early backfilling of deep foundation pits, saving construction time, reducing construction costs, minimizing safety risks during construction, and reducing safety management pressure.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, specifically to a combined tower crane enclosure construction method. Background Technology

[0002] With social development and accelerated urbanization, basements are becoming increasingly larger and deeper, a result of the trend towards larger, higher-rise urban buildings and the full utilization of basement space. However, the larger and deeper the basement, the greater the difficulty of construction and the higher the safety management requirements. Especially during the rainy and winter construction seasons, deep foundation pit projects are consistently one of the major sources of on-site risk. To reduce on-site safety risks and alleviate safety management pressure, backfilling deep foundation pits in advance is the most effective measure. However, during on-site construction, to minimize openings in floor slabs and secondary construction, tower cranes are often placed outside the main building, i.e., inside the foundation pit. During deep foundation pit backfilling, because the above-ground buildings still require the tower crane for construction, the tower crane cannot be dismantled, and the tower crane foundation cannot be backfilled. Protective facilities must be installed to ensure that the tower crane foundation is not affected by the backfill soil, meeting the conditions for later tower crane dismantling. Using traditional square brick retaining walls or steel pipe protective walls presents significant risks of deformation and collapse due to the limited height of the protective structure, and the workload is substantial. Using traditional construction procedures, the foundation pit is backfilled after the main structure is capped. As a result, the safety hazards of the deep foundation pit on site have always existed, and the pressure of on-site safety management is great. Summary of the Invention

[0003] This invention addresses at least one technical problem in the prior art by disclosing a combined tower crane enclosure construction method. This method, employing a combination of "enclosing piles + arch walls + internal bracing," effectively protects the tower crane foundation and standard sections. Compared to traditional construction procedures, it significantly reduces worker workload, shortens construction time, allows for early backfilling of deep foundation pits, reduces the number of critical projects, minimizes safety hazards, and alleviates on-site safety management pressure. Furthermore, the variable-diameter walls allow for "on-demand design," avoiding the drawbacks of a "one-size-fits-all" approach with equal-diameter arch walls. This reduces the amount of concrete and steel reinforcement used, especially for large-span foundation pits, saving construction materials, lowering construction costs, and enabling early integration of external network operations, thus shortening the construction period.

[0004] This invention is achieved through the following technical solution:

[0005] This invention first provides a construction method for a combined tower crane enclosure, comprising the following steps:

[0006] S1. Select the tower crane model and the location of the tower crane foundation according to the design parameters of the construction drawings, and design the slope protection method around the tower crane, while reserving the tower crane location.

[0007] S2. During construction within the tower crane's working range, the lateral soil pressure of the retaining wall at different depths is calculated based on the backfill depth. The thickness of the retaining wall corresponding to the elevation of the retaining wall is determined to be: 370mm for the retaining wall at elevations of -12.8m to -4.8m, and 240mm for the retaining wall at elevations of -4.8m to +0.5m. The retaining wall is then constructed with a variable diameter.

[0008] S3. During the construction of the retaining wall, a multi-layer internal bracing structure is installed vertically inside the retaining wall.

[0009] As a further option, the slope protection method around the tower crane is a combination of slope protection piles, high-pressure jet grouting piles, and natural slope.

[0010] As a further embodiment, the method for calculating the lateral soil pressure of retaining walls at different depths based on the backfill depth includes:

[0011] S21. The depth of backfill soil and the diameter of the retaining wall are determined according to the construction drawings. During the construction of the main structure, groundwater level is continuously lowered so that the groundwater level is always 1.5 meters below the foundation bottom. Therefore, the influence of groundwater level is not considered.

[0012] S22. Based on the thickness of the retaining wall, obtain the vertical bending moment M1, circumferential bending moment M, and circumferential axial force N of the lateral soil at different heights, and the bending strength must meet the following requirements:

[0013] M≤ftmW; (1)

[0014] Where: M is the design value of circumferential bending moment, ftm is the design value of masonry bending tensile strength, and W is the section modulus;

[0015] W=bh 2 / 6; (2)

[0016] Where b is the cross-sectional width and h is the cross-sectional thickness.

[0017] N≤φfA; (3)

[0018] Where N is the circumferential axial force; φ is the influence coefficient of the height-to-thickness ratio β and the eccentricity e of the axial force on the bearing capacity of the compression member; f is the design value of the compressive strength of the masonry; and A is the cross-sectional area.

[0019] S23. After multiple tests, the relationship between the thickness and elevation of the retaining wall was obtained.

[0020] As a further option, the internal support structure includes multiple support rods arranged in an alternating manner, and each support rod is movably connected to an adjustable support on both sides, with square timber or steel pipes installed on the support.

[0021] As a further option, the number of support rods on each floor shall be at least four, and they shall be evenly distributed along the circumference of the enclosure wall.

[0022] As a further option, the support rods are made of φ48.3×3.6mm steel pipes@1000mm. Two of the support rods are made of φ48.3×3.6mm steel pipes at both ends, which are tightly attached to the wall from bottom to top. The other two support rods are made of 40×80×1000mm square timber@1000mm, which are tightly attached to the wall.

[0023] As a further option, the method for arranging the number of layers of the internal support structure is as follows:

[0024] , (4;

[0025] Where n is the number of internal support layers, H is the height of the retaining wall, Δa is the allowable deformation of the retaining wall, and η is the sag-to-span ratio, η≥1 / 8.

[0026] As a further option, the enclosure wall is an inner circular enclosure wall that is tangent to the outside of the tower crane foundation, with a diameter consistent with the side length of the tower crane foundation.

[0027] As a further option, the construction of the retaining wall and the installation of internal bracing will be carried out simultaneously.

[0028] As a further measure, four displacement sensors are installed on the wall every 5 meters along the height direction during construction to monitor the horizontal displacement of the retaining wall in real time and transmit the data to a mobile terminal.

[0029] The features and beneficial effects of this invention are as follows:

[0030] (1) This invention uses a combined tower crane enclosure construction method of “retaining piles + arch wall + internal bracing” to effectively protect the tower crane foundation and standard section. Compared with the traditional construction process, it can significantly reduce the construction intensity of workers, shorten the construction time, realize the early backfilling of deep foundation pits, reduce the number of dangerous projects, reduce safety hazards, reduce the pressure of on-site safety management, save construction materials, reduce construction costs, realize the early interleaving of external network operations, and speed up the construction period. At the same time, the variable diameter wall set up allows the variable diameter to be “designed on demand”, avoiding the design drawbacks of the “one-size-fits-all” design of the equal diameter arch wall. It is not necessary to design the entire arch wall according to the maximum load and minimum radius to meet the local strict requirements. The radius and wall thickness of the arch ring can be adjusted according to the needs of different areas, reducing the amount of concrete and steel bars used. Especially for large-span foundation pits, the variable diameter can reduce the arch ring material consumption by about 30%, solving the problems of large deformation, collapse risk and large amount of engineering work in traditional technology.

[0031] (2) The slope protection method of the present invention is a combination of slope protection piles, high-pressure jet grouting piles and natural slope. This slope protection method is a composite support scheme that takes into account safety, economy and construction convenience. The slope protection piles play the core role of retaining soil, preventing slope slippage and collapse, and are suitable for the support around the tower crane and reserve installation space. The high-pressure jet grouting piles form a water-stop curtain to eliminate the risk of groundwater seepage and piping. The natural slope assists in unloading and further improves the overall stability of the slope. At the same time, the slope protection piles can be constructed in sections and can be carried out in conjunction with the tower crane foundation and the excavation of the foundation pit, shortening the overall construction period.

[0032] (3) The lower section of this invention is 370mm thick due to the large load, ensuring safety; the upper section is 240mm thick due to the small load. Compared with the entire section being 370mm thick, the amount of concrete used in the upper section can be reduced by about 35%, and the amount of supporting steel reinforcement can also be reduced. Especially for large-span retaining walls, the cumulative material cost savings are significant. The 240mm thickness of the upper section is thinner, which can simplify the formwork support process, reduce the amount of formwork and supports, and shorten the concrete pouring and curing time, thereby improving construction efficiency. Although the 370mm thickness of the lower section is relatively complex, it is only for the core load-bearing section. The overall construction cost can be reduced by 20% to 25% compared with the entire section of thick retaining wall, taking into account both construction convenience and economy. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a flowchart of the combined tower crane enclosure construction method described in an embodiment of the present invention;

[0035] Figure 2 This is a geometric dimension diagram showing the wall thickness of the water tank as described in an embodiment of the present invention, which is 370 mm.

[0036] Figure 3 This is a simplified load diagram for a water tank with a wall thickness of 370mm, as described in an embodiment of the present invention.

[0037] Figure 4 A screenshot of the existing specification described in the embodiments of the present invention;

[0038] Figure 5 This is a geometric dimension diagram showing the wall thickness of the water tank as described in an embodiment of the present invention, which is 240 mm.

[0039] Figure 6 This is a simplified load diagram of a water tank with a wall thickness of 240mm as described in an embodiment of the present invention;

[0040] Figure 7 This is a schematic plan view of the construction of the embodiment described in this invention;

[0041] Figure 8 for Figure 7 middle Enlarged view of the location;

[0042] Figure 9 for Figure 7 middle Enlarged view of the location;

[0043] Figure 10 As described in the embodiments of the present invention Figure 7 Sectional view along line AA;

[0044] Figure 11 As described in the embodiments of the present invention Figure 7 Elevation view.

[0045] Explanation of reference numerals in the attached figures:

[0046] 1-High-pressure jet grouting pile; 2-Slope protection pile; 3-Tower crane foundation; 4-Square timber; 5-Steel pipe; 6-Support rod; 7-Trailer. Detailed Implementation

[0047] To facilitate understanding of the present invention, a more comprehensive description of the present invention will be given below, and embodiments of the present invention will be provided, but this does not limit the scope of the present invention.

[0048] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0049] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0050] A combined tower crane enclosure construction method, such as Figures 1 to 11 As shown, it includes the following steps:

[0051] S1. Select the tower crane model and location according to the design parameters in the construction drawings, design the slope support method around the tower crane, and reserve the tower crane location.

[0052] In this application, the slopes around the tower crane are supported first, and then the tower crane position is reserved and the tower crane is installed. This can ensure the stability of the tower crane foundation and the safety of installation, and can also be put into use in advance to improve work efficiency. At the same time, it can solve problems such as small site and easy deformation of slope, and take into account safety, economy and construction period.

[0053] The slope protection method employs a combination of retaining piles, high-pressure jet grouting piles, and natural slope protection. This method is a composite support solution that balances safety, economy, and ease of construction. It combines the advantages of three support forms and is suitable for various complex working conditions (especially for slopes around tower cranes and medium-depth foundation pits with high groundwater levels). The retaining piles act as the core retaining wall, preventing slope slippage and collapse, and are compatible with tower crane perimeter support while providing installation space. The high-pressure jet grouting piles form a water-stop curtain, eliminating the risk of groundwater seepage and piping. The natural slope protection assists in unloading and further enhances the overall stability of the slope. This method is suitable for medium-depth working conditions with high groundwater levels and poor soil conditions, and is particularly suitable for slopes around tower cranes. The retaining piles can be deployed locally without affecting tower crane foundation construction, and the natural slope protection allows for flexible adjustment of the slope to adapt to site conditions. The retaining piles strictly control horizontal displacement, and the high-pressure jet grouting piles prevent soil softening and settlement, meeting the deformation requirements of Class I and Class II foundation pits and avoiding impact on surrounding facilities and the safe operation of the tower crane. Slope protection piles can be constructed in sections and can be carried out concurrently with tower crane foundations and foundation pit excavation, thus shortening the overall construction period.

[0054] The design parameters include the foundation pit grade, depth, geology, environment, surcharge, and soil and water pressure.

[0055] S2. Calculate the lateral soil pressure of the retaining wall at different depths based on the backfill depth. The relationship between the thickness and elevation of the retaining wall must meet the following requirements: the thickness of the retaining wall at the elevation of -12.8 meters to -4.8 meters is 370 mm, and the thickness of the retaining wall at the elevation of -4.8 meters to +0.5 meters is 240 mm. Then, the diameter of the retaining wall is adjusted accordingly.

[0056] Lower Section (-12.8m to -4.8m): This elevation is located in the lower part of the foundation pit, with a greater depth (maximum depth of 12.8m). It bears the maximum horizontal earth pressure and water pressure, and the soil depth is greater, resulting in a higher lateral pressure coefficient. This is the core load-bearing section for the retaining wall. A 370mm thick retaining wall is designed to effectively increase the section's moment of inertia and compressive bearing capacity, ensuring the retaining wall can fully withstand the ultra-large horizontal loads. This efficiently converts the load into axial pressure, preventing cracking and excessive deformation due to insufficient thickness. It also provides ample space for reinforcement, further enhancing the overall rigidity of the retaining wall and ensuring its stability. Upper Section (-4.8m to +0.5m): This elevation is close to the top of the foundation pit, with a shallower depth (minimum depth only 0.5m). The horizontal earth pressure and water pressure are significantly reduced (only 1 / 3 to 1 / 2 of the lower section). Being closer to the ground surface, the lateral soil constraint is weaker, but the load requirement is lower. The design uses a 240mm thick retaining wall. While meeting the load-bearing requirements at this elevation, excessive thickness is unnecessary to avoid material waste. Simultaneously, it ensures the proper functioning of the arch effect—the 240mm thickness meets the section stiffness requirements, ensuring the upper retaining wall can effectively transfer loads and work in tandem with the thicker lower retaining wall to form a complete load-bearing system. The lower section, due to its larger load, uses a 370mm thickness to ensure safety; the upper section, with its smaller load, uses a 240mm thickness. Compared to using 370mm thickness for the entire section, this reduces the amount of concrete used in the upper section by approximately 35%, and also reduces the amount of reinforcing steel. Especially for large-span retaining walls, the cumulative material cost savings are significant. The upper section is 240mm thicker, which simplifies the formwork support process, reduces the amount of formwork and supports used, and shortens the concrete pouring and curing time, thus improving construction efficiency. The lower section is 370mm thick, although the process is relatively more complex, it only targets the core load-bearing section. The overall construction cost can be reduced by 20% to 25% compared to the full-length thick retaining wall, taking into account both construction convenience and economy.

[0057] The method for calculating the lateral soil pressure of retaining walls at different depths based on the backfill depth includes:

[0058] S21. Based on the construction drawings, determine the depth of the backfill soil and the diameter of the retaining wall. During the construction of the main structure on site, groundwater level was continuously lowered, so that the groundwater level was always 1.5 meters below the foundation bottom. Therefore, the influence of the groundwater level is not considered.

[0059] S22. Based on the thickness of the retaining wall, obtain the vertical bending moment M1, circumferential bending moment M, and circumferential axial force N of the lateral soil at different heights, and the bending strength must meet the following requirements:

[0060] M≤ftmW; (1)

[0061] Wherein, M is the design value of circumferential bending moment, ftm is the design value of masonry bending tensile strength, and W is the section modulus.

[0062] W=bh 2 / 6; (2)

[0063] Where b is the cross-sectional width and h is the cross-sectional thickness.

[0064] N≤φfA; (3)

[0065] Where N is the circumferential axial force; φ is the influence coefficient of the height-to-thickness ratio β and the eccentricity e of the axial force on the bearing capacity of the compression member; f is the design value of the compressive strength of the masonry; and A is the cross-sectional area.

[0066] S23. After multiple tests, the relationship between the thickness and elevation of the retaining wall is found to be: the thickness of the retaining wall at elevations of -12.8 meters to -4.8 meters is 370 mm, and the thickness of the retaining wall at elevations of -4.8 meters to +0.5 meters is 240 mm.

[0067] In some embodiments, taking the construction of a water tank as an example, the tank wall thickness is 370mm, the cross-sectional width is 1000mm, the on-site tower crane foundation dimensions are 6m × 6m × 1.2m, and the backfill depth is -12.8m. The calculation process is as follows:

[0068] A1. Basic Parameters: The tower crane foundation dimensions for this project are 6 meters × 6 meters × 1.2 meters, and the retaining wall is a cylindrical structure with a diameter of 6 meters. During the construction of the main structure on site, groundwater level was continuously lowered, and the groundwater level remained 1.5 meters below the foundation bottom; therefore, the influence of the groundwater level is not considered.

[0069] A2. The geometric dimensions of the pool are as follows: Figure 2 As shown: the pool wall thickness is 370mm and the pool height is 1280mm.

[0070] A3 Figure 3 This is a simplified diagram for calculating the load on the water tank. In the diagram, "soil" represents lateral soil, and "external water" represents the pressure of external water. The data obtained by measuring the lateral soil at different heights are shown in Table 1.

[0071] Table 1

[0072]

[0073] In Table 1, H represents the height of the pool wall. From Table 1, we can see that the maximum circumferential bending moment is M = 2.97 kN·m and the maximum circumferential axial force is N = 106.81 kN.

[0074] According to formula (2), we can obtain that

[0075] W=bh 2 / 6 = 1000 × 370 2 6 / 10 6 =22.82;

[0076] This project uses MU20 sand-lime bricks and M10 mortar, according to national standards, such as... Figure 4 As shown, ftm=0.24.

[0077] According to formula (1), we know that:

[0078] M=2.97<ftmW=22.82×0.24=5.48, the circumferential bending strength meets the requirements.

[0079] The compressive strength calculation is as follows:

[0080] Φ adopts a coefficient of 1.0. According to the design values ​​of compressive strength of autoclaved sand-lime brick and autoclaved fly ash brick masonry (Table 2),

[0081] Table 2

[0082]

[0083] Since MU20 sand-lime bricks and M10 mortar are used in this project, f=2.67

[0084] A = 370 × 1000 = 370000;

[0085] According to formula (3), N = 106.81 ≤ φfA = 1.0 × 2.67 × 370000 ÷ 10 3 =987.9kN, the compressive strength meets the requirements.

[0086] As can be seen from this embodiment, this embodiment satisfies all the constraints in step S2.

[0087] In another embodiment, taking the construction of a water tank as an example, the tank wall thickness is 240mm, the cross-sectional width is 1000mm, the on-site tower crane foundation dimensions are 6m × 6m × 1.2m, and the backfill depth is -12.8m. The calculation process is as follows:

[0088] B1. Basic Parameters: The tower crane foundation dimensions for this project are 6 meters × 6 meters × 1.2 meters, and the retaining wall is a cylindrical structure with a diameter of 6 meters. During the construction of the main structure on site, groundwater level was continuously lowered, and the groundwater level remained 1.5 meters below the foundation bottom; therefore, the influence of the groundwater level is not considered.

[0089] B2. The geometric dimensions of the pool are as follows: Figure 5 As shown: the pool wall thickness is 240mm, and the pool height is 4800mm.

[0090] B3 Figure 6 This is a simplified diagram for calculating the load on the water tank. In the diagram, "soil" represents lateral soil, and "external water" represents the pressure of external water. The data obtained by measuring the lateral soil at different heights are shown in Table 3.

[0091] Table 3

[0092]

[0093] In Table 3, H represents the height of the pool wall, the maximum circumferential bending moment is M = 0.45 kN·m, and the maximum circumferential axial force is N = 30.88 kN.

[0094] According to formula (2), we can obtain that

[0095] W=bh 2 / 6 = 1000 × 370 2 6 / 10 6 =9.6;

[0096] This project uses MU20 sand-lime bricks and M10 mortar, according to national standards, such as... Figure 4 As shown, ftm=0.24.

[0097] According to formula (1), we know that:

[0098] M=0.45<ftmW=9.6×0.24=2.3, the circumferential bending strength meets the requirements.

[0099] The compressive strength calculation is as follows:

[0100] Φ uses a coefficient of 1.0. Since MU20 sand-lime bricks and M10 mortar are used in this project, f = 2.67.

[0101] A = 240 × 1000 = 240000;

[0102] According to formula (3), N = 30.88 ≤ φfA = 1.0 × 2.67 × 240000 ÷ 10 3 =640.8kN, the compressive strength meets the requirements.

[0103] Therefore, the retaining wall is designed as a 6-meter diameter cylinder, constructed using sand-lime bricks with a mortar strength grade of M10 and a brick strength grade of MU20. The retaining wall is 370mm thick at elevations of -12.8m to -4.8m, and 240mm thick at elevations of -4.8m to +0.5m. All diameter variations in this application meet compressive strength requirements, saving construction time and production resources without compromising safety standards.

[0104] S3. Add internal bracing structure to the enclosure wall.

[0105] The internal support structure includes multiple support rods 6 arranged in an alternating manner. Each support rod 6 is also movably connected to an adjustable support 7 on both sides. The support 7 is also equipped with square timber 4 or steel pipe 5.

[0106] Preferably, there are at least four support rods per layer, which are evenly distributed along the circumference of the enclosure wall.

[0107] Since the arch can withstand the soil pressure on its own without the need for internal bracing, but in order to further increase the safety redundancy of the retaining structure and reduce the occurrence of accidents, this application adds an internal bracing structure. Therefore, it is only necessary to calculate the number of layers of internal bracing.

[0108] The method for determining the number of layers of internal support is as follows:

[0109] The core of arranging the internal bracing for the retaining wall is to "assist the retaining wall in balancing loads and controlling deformation." This requires consideration of the retaining wall's rise-to-span ratio, stiffness distribution, and the shape of the foundation pit to avoid disrupting the arch effect. Specific arrangement principles are as follows:

[0110] Determining vertical layering requires satisfying the following:

[0111] , (4;

[0112] Where n is the number of internal support layers, H is the height of the retaining wall, Δa is the allowable deformation of the retaining wall, and η is the sag-to-span ratio; for example: H=15m, Δa=20mm, η=0.875, n≥2 layers.

[0113] The rise-to-span ratio is a core geometric feature and mechanical control parameter of the retaining wall. It refers to the ratio of the rise (f) of the retaining wall to the arch span (L), used to characterize the steepness of the retaining wall and directly determine the efficiency of the arch effect and the design parameters of the internal bracing. Rise (f): the vertical distance from the arch crown to the arch foot (arch axis); Arch span (L): the horizontal distance between the two arch feet of the retaining wall (the calculated span of the arch ring); The rise-to-span ratio must strictly meet ≥1 / 8, otherwise the arch effect cannot be fully utilized, which will lead to a sharp increase in unbalanced loads and a significant increase in the amount of internal bracing work (it is necessary to simultaneously increase the internal bracing cross-section and densify the internal bracing density).

[0114] In some embodiments, the steel pipes are selected with the following specifications: Q235 grade steel, 48.3mm (diameter) × 3.6mm (wall thickness), steel pipe 6 is 5m long, and steel pipe 5 is 6m long.

[0115] Square timber 4 specifications: 40mm×80mm, length 1000mm.

[0116] Support 7 specifications: Q345 carbon steel, Φ38mm×5mm hollow + 150mm×150mm×5mm support plate, total length of screw rod 600mm, load capacity ≥40kN.

[0117] This application utilizes a combined tower crane enclosure construction method consisting of "retaining piles + retaining walls + internal bracing" to effectively protect the tower crane foundation and standard sections. Compared to traditional construction procedures, this method significantly reduces worker workload, shortens construction time, enables early backfilling of deep foundation pits, reduces the number of critical and large-scale projects, minimizes safety hazards, alleviates on-site safety management pressure, saves construction materials, lowers construction costs, allows for early interleaving of external network operations, and accelerates the construction period.

[0118] Example

[0119] like Figures 7 to 11 As shown, taking the construction of a water tank as an example, the wall thickness of the water tank is 370mm, the cross-sectional width is 1000mm, the dimensions of the tower crane foundation on site are 6m×6m×1.2m, and the backfill depth is -12.8m.

[0120] Step 1: Construction of retaining piles.

[0121] According to the drawings, the foundation pit was excavated and slope protection was constructed. The excavation depth of the foundation pit was 12.8 meters, and the support was installed before excavation. The tower crane installation location was communicated with the design institute in advance. The deep foundation pit design directly arranged retaining piles around the tower crane location. The slope protection piles 2 were constructed first, followed by the high-pressure cast-in-place piles. The high-pressure cast-in-place piles 1 and 2 of the tower crane foundation 3 were designed to be the same, both being φ600C30 piles. The slope protection piles were spaced 1500mm apart, and the high-pressure cast-in-place piles interlocked with the slope protection piles by 100mm.

[0122] The parameters for supporting the slopes around the tower crane are as follows:

[0123] Retaining piles: Slope protection piles are used for elevations from -14m to -4.2m.

[0124] Slope protection pile 2: Diameter 600, concrete strength grade: C30, pile spacing 1500mm, embedment depth 8m, cantilever end 9.2m.

[0125] High-pressure jet grouting pile 1: Diameter 600, concrete strength grade: C30, interlocking 100mm, embedment depth 7m, cantilever end 9.2m.

[0126] Natural slope is adopted for elevations above -4.2m.

[0127] Step 2: Tower Crane Foundation Construction

[0128] Prepare a tower crane foundation construction plan according to the tower crane instruction manual, and strictly follow the plan and instruction manual requirements for foundation positioning and layout, rebar tying, formwork erection and concrete pouring.

[0129] Step 3: Tower Crane Installation

[0130] A special construction plan for tower crane installation was prepared based on the tower crane instruction manual and construction drawings, and the tower crane was installed, attached, and lifted in strict accordance with the plan requirements.

[0131] Step 4: Construction of retaining wall + internal bracing reinforcement

[0132] The retaining wall is designed as a 6-meter diameter cylinder, constructed with sand-lime bricks, with horizontal mortar joints 10mm wide and vertical mortar joints 12mm wide. The mortar strength grade is M10, and the sand-lime brick strength grade is MU20. The retaining wall is 370mm thick at elevations of -12.8m to -4.8m, and 240mm thick at elevations of -4.8m to +0.5m.

[0133] The site retaining wall is constructed using gray sand bricks. An inscribed circular retaining wall is built along the outer edge of the tower crane foundation (i.e., the diameter of the retaining wall is the same as the side length of the tower crane foundation). Before construction, a water pump is placed at the bottom of the foundation to remove accumulated water in a timely manner. The verticality of the wall is ensured during the construction process.

[0134] Internal supports were erected every 1.2 meters of masonry work. A total of four horizontal internal supports were designed and installed on site, using φ48.3×3.6mm steel pipes at 1000mm intervals, with adjustable supports at both ends. Two of these supports used φ48.3×3.6mm steel pipes running the entire length of the retaining wall from bottom to top, while the other two supports used 40×80×1000mm square timber at 1000mm intervals, tightly attached to the retaining wall, within their adjustable supports at both ends.

[0135] During the construction process, four displacement sensors are installed on the wall every 5 meters along the vertical direction to monitor the horizontal displacement of the retaining wall in real time and transmit the data to a mobile terminal. Alarm values ​​are set for the sensors in advance, and designated personnel are assigned to manage the sensors and collect data.

[0136] The final height of the retaining wall should be at least 500mm higher than the final finished surface of the backfill soil. After the wall is built, the opening should be covered with a cover plate in a timely manner.

[0137] The above data may be adjusted according to actual circumstances and is not fixed. However, all data must be used only after safe calculations have been performed.

[0138] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A combined tower crane enclosure construction method, characterized by: Includes the following steps: S1. Select the tower crane model and the location of the tower crane foundation according to the design parameters of the construction drawings, and design the slope protection method around the tower crane, while reserving the tower crane location. S2. During construction within the tower crane's working range, the lateral soil pressure of the retaining wall at different depths is calculated based on the backfill depth. The thickness of the retaining wall corresponding to the elevation of the retaining wall is determined to be: 370mm for the retaining wall at elevations of -12.8m to -4.8m, and 240mm for the retaining wall at elevations of -4.8m to +0.5m. The retaining wall is then constructed with a variable diameter. S3. During the construction of the retaining wall, a multi-layer internal support structure is vertically installed inside it.

2. The construction method for a combined tower crane enclosure according to claim 1, characterized in that: The slope protection method around the tower crane is a combination of slope protection piles, high-pressure jet grouting piles, and natural slope.

3. The construction method for a combined tower crane enclosure according to claim 3, characterized in that: The method for calculating the lateral soil pressure of retaining walls at different depths based on the backfill depth includes: S21. The depth of backfill soil and the diameter of the retaining wall are determined according to the construction drawings. During the construction of the main structure, groundwater level is continuously lowered so that the groundwater level is always 1.5 meters below the foundation bottom. Therefore, the influence of groundwater level is not considered. S22. Based on the thickness of the retaining wall, obtain the vertical bending moment M1, circumferential bending moment M, and circumferential axial force N of the lateral soil at different heights, and the bending strength must meet the following requirements: M≤ftmW; (1) Where: M is the design value of circumferential bending moment, ftm is the design value of masonry bending tensile strength, and W is the section modulus; W = bh 2 / 6; (2) Where b is the cross-sectional width and h is the cross-sectional thickness. N≤φfA; (3) Where N is the circumferential axial force; φ is the influence coefficient of the height-to-thickness ratio β and the eccentricity e of the axial force on the bearing capacity of the compression member; f is the design value of the compressive strength of the masonry; and A is the cross-sectional area. S23. After multiple tests, the relationship between the thickness and elevation of the retaining wall was obtained.

4. The construction method for a combined tower crane enclosure according to claim 1, characterized in that: The internal support structure includes multiple support rods arranged in an alternating manner, and each support rod is movably connected to an adjustable support on both sides, with square timber or steel pipes installed on the support.

5. The construction method for a combined tower crane enclosure according to claim 4, characterized in that: The minimum number of support rods per floor is 4, and they are evenly distributed along the circumference of the enclosure wall.

6. The construction method for a combined tower crane enclosure according to claim 5, characterized in that: The support rods are made of φ48.3×3.6mm steel pipes@1000mm. Two of the support rods are made of φ48.3×3.6mm steel pipes at both ends, which are tightly attached to the wall from bottom to top. The other two support rods are made of 40×80×1000mm square timber@1000mm, which are tightly attached to the wall.

7. The construction method for a combined tower crane enclosure according to claim 1, characterized in that: The method for arranging the number of layers of the internal support structure is as follows: ， （4）； Where n is the number of internal support layers, H is the height of the retaining wall, Δa is the allowable deformation of the retaining wall, and η is the sag-to-span ratio, η≥1 / 8.

8. The construction method for a combined tower crane enclosure according to claim 1, characterized in that: The retaining wall is an inner circle enclosing the outside of the tower crane foundation, with a diameter consistent with the side length of the tower crane foundation.

9. The construction method for a combined tower crane enclosure according to claim 1, characterized in that: The construction of the retaining wall and the installation of the internal bracing were carried out simultaneously.

10. A construction method for a combined tower crane enclosure according to claim 9, characterized in that: During construction, four displacement sensors are installed on the wall every 5 meters along the height direction to monitor the horizontal displacement of the retaining wall in real time and transmit the data to a mobile terminal.

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