Solid fluidized soil for foundation pit brick blank film and construction method

Abstract

The invention relates to solid fluidized soil for a foundation pit brick blank film and a construction method, a three-dimensional space network is formed in a fluidized soil matrix by doping shear-resistant fibers with specific length and doping amount, and the crack resistance, toughness and integrity of a material are remarkably improved. According to the material, engineering waste soil or sand is used as main aggregate, the cost is low, and resource utilization is achieved; the composite curing agent and the selectable early strength agent endow the material with good early strength development ability. Compared with traditional brickwork, the material has excellent bending resistance and impact resistance, can effectively resist lateral soil pressure, fundamentally overcomes the potential safety hazard that a brick blank film is easy to crack and collapse, and meanwhile has the comprehensive advantages of being environmentally friendly and good in economical efficiency.

Description

Technical Field

[0001] This invention relates to a solid fluidized soil for use as a formwork for foundation pit bricks and a construction method thereof, belonging to the field of civil engineering construction technology. Background Technology

[0002] In deep foundation pit construction, brick formwork for foundations is widely used as a temporary support and molding structure to form the outer formwork for concrete pouring. Traditional brick formwork is generally constructed manually using clay bricks or concrete blocks. This long-standing construction method has revealed many inherent defects in practice and can no longer meet the increasingly demanding requirements of modern engineering construction for safety, efficiency, environmental protection, and cost.

[0003] First, the structural stability of traditional brick-built formwork structures is severely inadequate. Masonry structures have low shear and flexural strength, making them highly susceptible to instability, cracking, and even collapse under lateral earth pressure from the foundation pit, disturbance from construction machinery, and external loads, posing significant safety hazards. This risk increases dramatically, especially when the foundation depth is large (usually exceeding 1.5 meters) or the foundation soil is weak, often requiring complex additional support and reinforcement measures, which increases costs and restricts working space.

[0004] Secondly, construction efficiency is low and labor dependence is high. Traditional masonry techniques involve cumbersome procedures, including leveling the base, surveying and setting out, laying bricks layer by layer, and plastering both inside and outside, all of which rely entirely on manual labor by skilled workers. This not only leads to a long construction period but also impacts the project's economic benefits against the backdrop of rising labor costs.

[0005] Furthermore, from a materials and environmental perspective, traditional practices consume large quantities of fired clay bricks or cement products, which is inconsistent with current green building and sustainable development concepts. At the same time, brickwork is typically broken and demolished after its purpose is fulfilled, generating construction waste that is difficult to recycle and burdening environmental remediation.

[0006] Furthermore, traditional brick formwork has limited adaptability. For irregularly shaped foundations with complex planar shapes (such as arcs or polygons), or in situations with narrow working spaces, the masonry construction is extremely difficult, making it hard to guarantee the flatness, verticality, and overall quality of the masonry, and easily becoming a weak link in quality control.

[0007] To overcome the aforementioned problems, the industry has attempted to use cast-in-place concrete retaining walls or sheet piles as alternatives. However, these methods are often difficult to widely apply in conventional brick formwork projects due to their more complex procedures, higher material and machinery costs, and longer construction cycles. Therefore, developing a new type of brick formwork technology that integrates the functions of "formwork" and "support," enables rapid prototyping, is economical and efficient, and is environmentally friendly has become a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0008] The purpose of this invention is to provide a solid fluidized soil for use as a brick formwork in foundation pits and a construction method thereof, in order to solve the above-mentioned problems.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a solid fluidized soil for foundation pit brick formwork, wherein the solid fluidized soil comprises, by weight, 70%-85% aggregate, 8%-15% composite curing agent, 1%-3% early strength agent, and water that can adjust the aggregate, composite curing agent, and early strength agent to a set moisture content mixture, and 0.6-1.2 kg of shear-resistant fiber is added to each cubic meter of the mixture.

[0010] Furthermore, the aggregate is selected from engineering waste soil, sand or a mixture thereof, with a particle size not exceeding 5 mm.

[0011] Furthermore, the composite curing agent is a cement-based curing agent or a geopolymer-based curing agent.

[0012] Furthermore, the shear-resistant fiber is selected from at least one of polypropylene fiber, glass fiber or basalt fiber, and its length is 12mm to 24mm.

[0013] Furthermore, the early strength agent is selected from calcium formate or sodium sulfate.

[0014] The present invention also provides a construction method for solid fluidized soil used as a formwork for foundation pit bricks, characterized in that it uses the solid fluidized soil as described in any one of claims 1 to 5, and includes the following steps: S1. Excavation and foundation treatment of the foundation pit: Excavate the foundation pit of the foundation according to the design dimensions, and reserve the construction space for the solid fluidized soil brick formwork. Level and compact the bottom of the pit. S2. Surveying and Setting Out and Template Installation: Set out the edge line of the foundation and the inner control line of the fluidized soil formwork at the bottom of the pit, and install and reinforce the inner template along the control line; S3. Mixing and transporting solid fluidized soil: Mix the components according to the proportions and mix them evenly to obtain a fluidized soil mixture with self-leveling properties, and transport it to the foundation pit working face; S4. Layered backfilling and compaction: The fluidized soil mixture is poured in layers into the gap between the formwork and the pit wall, and then moderately vibrated and compacted. S5. Curing and Demolding: Curing the formed fluidized soil formwork until its strength meets the demolding requirements, then removing the inner formwork and supports.

[0015] Furthermore, in step S2, when the depth of the foundation pit is not less than 1.2 meters, a horizontal support system is set on the outside of the inner template, with a horizontal spacing of not more than 800 mm and a vertical spacing of not more than 600 mm.

[0016] Furthermore, in step S3, a forced mixer is used for mixing, the mixing time is not less than 3 minutes, and the slump of the mixture is controlled within the range of 160mm~200mm.

[0017] Furthermore, in step S4, the thickness of each layer of backfill is controlled at 300mm~500mm, and an immersion vibrator is used for compaction.

[0018] Furthermore, in step S5, the demolding strength requirement is that the compressive strength of the solid fluidized soil test block cured under the same conditions reaches 0.8MPa~1.0MPa, the curing method includes covering and moisturizing curing, and the demolding time can be within 12-24 hours after pouring.

[0019] Compared with the prior art, the solid fluidized soil and its construction method provided by this invention bring the following significant benefits: The solid fluidized soil provided by this invention, through the incorporation of shear-resistant fibers of specific length and dosage, forms a three-dimensional spatial network within the fluidized soil matrix, significantly improving the material's crack resistance, toughness, and integrity. This material utilizes engineering waste soil or sand as the main aggregate, resulting in low cost and resource utilization; the composite curing agent and optional early-strength agent endow it with excellent early strength development capabilities. Compared to traditional masonry, this material exhibits superior bending and impact resistance, effectively resisting lateral earth pressure, fundamentally overcoming the safety hazards of easy cracking and collapse of brick formwork, while also possessing the comprehensive advantages of being green, environmentally friendly, and economical.

[0020] The construction method provided by this invention achieves rapid molding of the brick formwork and an integrated formwork-support structure through a standardized process of formwork erection, pouring, and formwork removal. This method simplifies traditional multi-stage masonry construction into mechanized operations, significantly shortening the construction period. A detachable support system is installed on the outside of the formwork to ensure safety during deep foundation pit construction; layered backfilling and vibration ensure structural compaction; and the timing of formwork removal is precisely determined based on the strength of test blocks under the same conditions, balancing efficiency and safety. This method is highly adaptable, especially suitable for irregularly shaped foundations and narrow working surfaces, offering controllable quality, low labor intensity, and a significant reduction in overall construction costs.

[0021] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0022] Figure 1This is a flowchart illustrating a construction method for solid fluidized soil used as a formwork for foundation pit bricks, as shown in one embodiment of this application. Detailed Implementation

[0023] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0024] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for 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. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0025] 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 can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] The solid fluidized soil for foundation pit brick formwork shown in one embodiment of this application comprises, by weight, 70%-85% aggregate, 8%-15% composite curing agent, 1%-3% early strength agent, and water to adjust the aggregate, composite curing agent, and early strength agent to a set moisture content mixture. 0.6-1.2 kg of shear-resistant fiber is added to each cubic meter of mixture.

[0027] In one embodiment, the aggregate is selected from engineering waste soil, sand or a mixture thereof, with a particle size not exceeding 5 mm.

[0028] In one embodiment, the composite curing agent is a cement-based curing agent or a geopolymer-based curing agent.

[0029] In one embodiment, the shear-resistant fiber is selected from at least one of polypropylene fiber, glass fiber or basalt fiber, and has a length of 12 mm to 24 mm.

[0030] In one embodiment, the early strength agent is selected from calcium formate or sodium sulfate.

[0031] Please refer to Figure 1The present invention also provides a construction method for solid fluidized soil used in foundation pit brick formwork, characterized in that it uses solid fluidized soil according to any one of claims 1 to 5, and includes the following steps: S1. Excavation and foundation treatment of the foundation pit: Excavate the foundation pit of the foundation according to the design dimensions, and reserve the construction space for the solid fluidized soil brick formwork. Level and compact the bottom of the pit. S2. Surveying and Setting Out and Template Installation: Set out the edge line of the foundation and the inner control line of the fluidized soil formwork at the bottom of the pit, and install and reinforce the inner template along the control line; S3. Mixing and transporting solid fluidized soil: Mix the components according to the proportions and mix them evenly to obtain a fluidized soil mixture with self-leveling properties, and transport it to the foundation pit working face; S4. Layered backfilling and compaction: The fluidized soil mixture is poured in layers into the gap between the formwork and the pit wall, and then moderately vibrated and compacted. S5. Curing and Demolding: Curing the formed fluidized soil formwork until its strength meets the demolding requirements, then removing the inner formwork and supports.

[0032] In one embodiment, in step S2, when the depth of the foundation pit is not less than 1.2 meters, a horizontal support system is set on the outside of the inner template, with the horizontal spacing of the supports not greater than 800 mm and the vertical spacing not greater than 600 mm.

[0033] In one embodiment, in step S3, a forced mixer is used for mixing, the mixing time is not less than 3 minutes, and the slump of the mixture is controlled within the range of 160mm~200mm.

[0034] In one embodiment, in step S4, the thickness of each layer of backfill is controlled at 300mm~500mm, and an immersion vibrator is used for compaction.

[0035] In one embodiment, in step S5, the demolding strength requirement is that the compressive strength of the solid fluidized soil test block cured under the same conditions reaches 0.8MPa~1.0MPa, the curing method includes covering and moisturizing curing, and the demolding time can be within 12-24 hours after pouring.

[0036] Example 1: Construction of foundation cap for deep soft soil pits: Project Background: An office building project located in a coastal soft soil area has two underground floors. The core tube area has a foundation depth of 2.2 meters. The soil is fluid plastic silty clay with high water content and low bearing capacity. Traditional brick formwork construction carries extremely high risks.

[0037] Material Design: Based on earth pressure calculations, the design thickness of the fluidized soil formwork is determined to be 0.9 meters (approximately 0.41H). Solid fluidized soil mix proportions (per cubic meter): Aggregate: Waste silty clay excavated from local foundation pits, dried, crushed, and sieved through a 5mm sieve, 780 kg (dry weight). Composite curing agent: P.O42.5 ordinary Portland cement, 120 kg. Shear-resistant fiber: Bundle-shaped monofilament polypropylene fiber, 18 mm in length, 0.9 kg. Early-strength agent: Calcium formate, 2% of the cement weight, i.e., 2.4 kg. Water: The optimal moisture content was determined based on field tests; an appropriate amount of water was added to achieve a slump of approximately 180 mm in the mixture.

[0038] Construction process: S1: During the excavation of the foundation pit, each side is extended 0.9 meters beyond the structural dimensions. After excavation to the bottom, a thin layer of sand is laid and compacted and leveled. Lightweight wellpoint dewatering is used to lower the groundwater level to 0.5 meters below the bottom of the pit.

[0039] S2: Accurately measure and lay out the lines. Install 15mm thick high-strength film-coated plywood as the inner template (3). Since the depth is >1.2m, set Φ48×3.0mm steel pipes as a support system on the outside of the template at @750mm (horizontal) × @550mm (vertical) and tighten them with the surrounding formwork set at the pit opening.

[0040] S3: A centralized mixing point is set up on-site, using a JS500 forced mixer. First, add soil, cement, and calcium formate and dry mix for 30 seconds. Then add water and polypropylene fiber, with a total mixing time of 4 minutes. The mixture should be homogeneous and fluid with a slump of 190mm. Transport the mixture to the pit edge using a small motorized dump truck and pour it into the formwork via a chute.

[0041] S4: Layered pouring, each layer approximately 400mm thick. Use a Φ30 immersion vibrator, inserting it at approximately 400mm intervals, vibrating for about 15-20 seconds at each point, until the surface is covered with slurry and no large air bubbles emerge. Smooth the top surface with a wooden trowel.

[0042] S5: Immediately after pouring, cover with plastic film. Leave test blocks on site for curing under the same conditions. Ambient temperature: approximately 15℃. After 18 hours of curing, the test blocks were sent for testing and the compressive strength was found to be 0.92MPa. Then, the steel pipe supports and inner formwork were systematically removed. After demolding, the surface of the formwork was smooth and dense, with no visible cracks, only a small number of evenly distributed fine pores.

[0043] Implementation Results: Throughout the entire process of reinforcing steel reinforcement and concrete pouring for the foundation, the fluidized soil formwork showed no signs of deformation, displacement, or cracking, demonstrating excellent stability. The construction of this foundation formwork (from formwork erection to demolding) took approximately 24 hours, representing an efficiency improvement of over 400% compared to the originally planned 240mm thick brick formwork (estimated to require 5-6 days of masonry and plastering, and additional reinforcement). It utilized a large amount of waste soil from the project itself, saving on all brick purchase costs and waste soil transportation fees. Although cement and fiber costs increased, labor costs were reduced by over 60%, resulting in an overall cost reduction of approximately 25%. It also reduced the consumption of approximately 20 cubic meters of clay bricks and corresponding construction waste.

[0044] Example 2: Construction of irregularly shaped foundation in a narrow space: Project Background: The equipment foundation platform for a renovation project is located between an existing building and underground pipelines, with a narrow working space and an irregular polygonal plan. Traditional masonry methods cannot guarantee the quality of masonry work in such a confined space.

[0045] Material design: Foundation depth 1.0 meter, fluidized soil membrane thickness 0.35 meters.

[0046] Solid fluidized soil mix proportions (per cubic meter): Aggregate: 800 kg of a mixture of medium-coarse sand and fine crushed stone (2:1). Composite curing agent: 100 kg of slag-based polymer (powder). Shear fiber: 0.7 kg of alkali-resistant glass fiber with a length of 12 mm. Water: Adjusted to a slump of 170 mm.

[0047] Construction process: S1 / S2: After precise excavation, small steel formwork was precisely erected according to the irregular shape. Since the depth did not exceed 1.2 meters, the calculated lateral pressure was relatively small, so no additional dense support was set up, and only local reinforcement was carried out at the key corners.

[0048] S3 / S4: Mixed on-site using a small mobile mixer. Utilizing the excellent fluidity of the fluidized soil, it easily fills all irregular corners, requiring only wooden sticks for auxiliary flow guidance and light tamping.

[0049] S5: Film covering and curing. After 20 hours, the mold is removed, and the irregularly shaped membrane has a clear outline, sharp edges, and straight lines.

[0050] Implementation results: It perfectly solved the problem of constructing a formwork in narrow and irregularly shaped spaces. The forming quality is far superior to the unevenness that may occur in masonry. The construction speed is fast and no special technicians are required.

[0051] Example 3: Emergency Construction Project in Water-Rich Strata: Project Background: A municipal project along a river has a high groundwater level and a tight schedule, requiring the next process to begin as soon as possible after the foundation membrane is constructed.

[0052] Material design: The foundation depth is 1.5 meters, and the design membrane thickness is 0.6 meters.

[0053] Solid fluidized soil mix design (per cubic meter): Aggregate: River sand, 750 kg (moisture content approximately 3%). Composite curing agent: Rapid-hardening sulfoaluminate cement, 130 kg. Shear fiber: Basalt fiber, 24 mm in length, 1.1 kg. Early strength agent: Sodium sulfate, 2.5% of cement weight, i.e., 3.25 kg. Water: Controlled low water-cement ratio, slump 160 mm.

[0054] Construction process: A curtain wall was used for waterproofing around the foundation pit. Necessary supports were installed outside the formwork. Early strength monitoring was a key focus.

[0055] Implementation Results: With the synergistic effect of adding an early-strength agent and using rapid-hardening cement, the fluidized soil formwork exhibited rapid strength development. Only 14 hours after pouring, the strength of the test blocks under the same conditions reached 0.88 MPa, allowing for immediate demolding and saving valuable time for the project. The formwork also demonstrated stability in water-rich environments.

[0056] Performance comparison test: To quantitatively demonstrate the superiority of the present invention, a performance comparison test was conducted on the solid fluidized soil of the present invention (using the mix proportion of Example 1) and a 240mm thick brick masonry (Mu10 standard brick) constructed with traditional M7.5 cement mortar under standard laboratory conditions. The results are summarized in the table below.

[0057] As can be clearly seen from the table above, this invention surpasses traditional brick masonry formwork technology in all aspects, including the mechanical properties of materials, structural stability, construction efficiency, economy, and environmental friendliness.

[0058] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0059] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A solid fluidized soil for a foundation pit brick membrane, characterized by, The solid-state fluidized soil comprises, by weight, 70-85% of aggregate, 8-15% of composite curing agent, 1-3% of early strength agent, and water for adjusting the aggregate, composite curing agent, and early strength agent into a mixture with a set moisture content, and 0.6-1.2 Kg of shear-resistant fibers per cubic meter of the mixture.

2. The solid fluidized soil for a foundation pit brick membrane according to claim 1, wherein, The aggregate is selected from engineering waste soil, sand, or a mixture thereof, and has a particle size of not more than 5 mm.

3. The solid fluidized soil for a foundation pit brick membrane according to claim 1, wherein The composite curing agent is a cement-based curing agent or a geopolymer-based curing agent.

4. The solid fluidized soil for a foundation pit brick membrane according to claim 1, wherein The shear-resistant fibers are selected from at least one of polypropylene fibers, glass fibers, or basalt fibers, and have a length of 12-24 mm.

5. The solid fluidized soil for a foundation pit brick membrane according to claim 1, wherein The early strength agent is selected from calcium formate or sodium sulfate.

6. A construction method for a solid-fluidized soil of a foundation pit brick membrane, characterized by, The solid-state fluidized soil of any one of claims 1-5 is used, and comprises the following steps: S1. Foundation pit excavation and base treatment: excavate a pile cap foundation pit according to the design size, and reserve a construction space for the solid-state fluidized soil brick mold membrane, and level and tamp the pit bottom; S2. Measurement and template installation: place the pile cap boundary line and the fluidized soil mold membrane inside control line on the pit bottom, install the inside template along the control line, and reinforce it; S3. Mixing and transportation of the solid-state fluidized soil: mix and uniformly mix the components according to the proportioning, obtain the fluidized soil mixture with self-leveling property, and transport it to the foundation pit working surface; S4. Layered backfilling and compaction: layer the fluidized soil mixture in the gap between the template and the pit wall, and perform moderate vibration and compaction; S5. Curing and form removal: cure the formed fluidized soil mold membrane, and remove the inside template and support after the strength reaches the form removal requirement.

7. The method for constructing a solid-fluidized soil for a foundation pit brick membrane according to claim 6, wherein In step S2, when the foundation pit depth is not less than 1.2 meters, a horizontal support system is arranged outside the inside template, the horizontal spacing of the support is not more than 800 mm, and the vertical spacing is not more than 600 mm.

8. The method for constructing a solid-fluidized soil for a foundation pit brick membrane according to claim 6, wherein, In step S3, a forced mixer is used for mixing, the mixing time is not less than 3 minutes, and the slump of the mixture is controlled in the range of 160-200 mm.

9. The method for constructing a solid-fluidized soil for a foundation pit brick membrane according to claim 6, wherein, In step S4, the thickness of each layer of the layered backfilling is controlled in the range of 300-500 mm, and a plug-in vibrator is used for vibration.

10. The method for constructing a solid-fluidized soil for a foundation pit brick membrane according to claim 6, wherein, In step S5, the form removal strength requirement is that the compressive strength of the solid-state fluidized soil curing test block under the same conditions reaches 0.8-1.0 MPa, the curing method includes covering and moisturizing curing, and the form removal time can be within 12-24 hours after pouring.

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