Composite ground floor and construction method

Abstract

The invention relates to the technical field of soil control and treatment, and discloses a construction method of a composite ground floor, which comprises the following steps: in-situ modification of a deep foundation: crushing and scarifying original-state foundation soil, and doping a composite curing material for deep stirring to form a cured soil base layer with structural strength; and gradient implantation of interfacial aggregate: uniformly spreading coarse aggregate on the surface of the solidified soil base layer after the solidified soil base layer is leveled and is in a plastic rheological window period without final setting, and pressing the coarse aggregate into the soil body through mechanical pressure. According to the composite ground floor and the construction method, the technical problems that in an existing soft foundation industrial floor system, due to the fact that a physical isolation layer is arranged between a foundation and a concrete plate, the interface shear resistance is poor, and consequently a structural layer slides and disconnects in a mechanical mode under the heavy load working condition are solved.

Description

Technical Field

[0001] This invention relates to the field of soil control and remediation technology, specifically to a composite foundation slab and its construction method. Background Technology

[0002] In existing soft soil industrial flooring construction techniques, a "sandwich" construction process is typically used to block the upward transmission of underground capillary water vapor and prevent cement slurry from seeping into the soil layer during concrete pouring. This involves laying a layer of PE plastic film, geotextile, or asphalt felt as a physical isolation layer (moisture barrier) between the treated subgrade and the reinforced concrete structural layer. While this approach solves the moisture-proofing and slurry retention issues to some extent and ensures a suitable environment for the early hydration reaction of the concrete, it is not without its limitations.

[0003] However, this physical isolation layer completely severs the stress transfer path between the upper rigid concrete slab and the lower flexible foundation soil, creating a "complete slip surface" with extremely low friction at the interface. When the floor is subjected to frequent braking, steering, or dynamic load impacts from heavy vehicles, the concrete slab, lacking horizontal anchorage and shear restraint from the base layer, is prone to relative displacement on the isolation layer surface. This can induce slab warping, corner fractures, and misalignment at expansion joints, severely weakening the overall load-bearing capacity and service life of the floor system. Summary of the Invention

[0004] The purpose of this invention is to solve the technical problem in existing soft-foundation industrial flooring systems where the physical isolation layer between the foundation and the concrete slab results in a lack of interfacial shear resistance, leading to slippage and mechanical disconnection of the structural layer under heavy loads. The invention proposes a composite flooring system and its construction method.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A construction method for a composite foundation slab includes the following steps: S1. Deep foundation in-situ modification: The original foundation soil is crushed and loosened, and then mixed with composite solidification materials for deep mixing to form a solidified soil base with structural strength. S2. Gradient implantation of interfacial aggregate: During the plastic rheological window period when the solidified soil base is leveled and not yet fully set, coarse aggregate is evenly spread on its surface and mechanically pressed into the soil, so that the coarse aggregate is in a semi-embedded state with the lower part anchored to the soil and the upper part exposed to the air. After the solidified soil hardens, an interfacial shear bond is formed. S3. Interlocking pouring of structural layer: The concrete structural layer is poured directly on the shear key of the interface, and the fluidity of the concrete slurry is used to wrap the exposed part of the coarse aggregate in all directions, forming a root-like mechanical interlock between the foundation and the floor structure. S4. High-precision surface layer construction: After the concrete structure layer has cured, its surface is treated and a wear-resistant protective layer is constructed.

[0006] Based on the above technical solution, the present invention can be further improved as follows.

[0007] Furthermore, in S1, a compartmentalized interval stirring process is adopted, specifically including: The construction area is divided into several standard grid units, and construction is carried out in an interval sequence of odd-numbered grids first and even-numbered grids later. The construction interval between adjacent grids is not less than 24 hours. The volume shrinkage stabilization period of the grids constructed earlier is used as the stress release boundary of the grids constructed later.

[0008] Furthermore, in S1, for soft silty undisturbed soil, the in-situ modification solidification depth is greater than or equal to 2m, and the characteristic value of the bearing capacity of the solidified foundation is greater than or equal to 150kPa. Step S1 further includes a node reinforcement process: a floor slab platform is set at intervals in the solidified soil base layer, and an upwardly extending connecting member is pre-embedded in the floor slab platform for rigid anchoring with the concrete structural layer in subsequent steps.

[0009] Furthermore, the composite curing material is composed of silicate cement, soil curing enzyme, and hydrophobic modifying components; The hydrophobic modified component fills the micropores of the solidified soil and forms a modified membrane with hydrophobic properties, so that the impermeability grade of the solidified soil base reaches P6 or above, blocking the upward transmission path of underground capillary water vapor.

[0010] Furthermore, in S2, the coarse aggregate is selected as multi-faceted crushed stone with a Mohs hardness greater than or equal to 6 and a particle size of 20mm to 30mm. The mechanical pressure is applied to the coarse aggregate to an embedment depth of 1 / 2 to 2 / 3 of its own geometric height, and the coarse aggregate has a planar coverage of 30% to 40% on the surface of the solidified soil. The lateral squeezing between the aggregates forms a macroscopic meshing surface with a roughness Ra greater than or equal to 10 mm.

[0011] Furthermore, the plastic rheological window period refers to the period during which the penetration resistance of the solidified soil slurry is between 0.5 MPa and 1.5 MPa after initial compaction and leveling, and the soil exhibits thixotropic properties. During this window period, the soil possesses the plastic yield stress that allows the aggregate to be pressed in, as well as the cohesion to maintain the semi-suspended state of the aggregate.

[0012] Furthermore, it also includes an upper and lower alignment stress induction procedure, specifically including: During the in-situ modification stage of S1, inverted V-shaped or strip-shaped bottom guide elements are pre-embedded at the compartment joints of the solidified soil base layer. During the concrete pouring stage of S3, the three-dimensional coordinates of the bottom guide are recorded using a positioning instrument; Before S4 is implemented, a slit is cut on the surface of the concrete structure layer according to the coordinates, so that the effective induction zone of the surface slit covers the center line of the bottom induction element, forming a stress release channel that runs through the upper and lower structural layers.

[0013] Furthermore, a dual connection system with point-surface bonding is constructed between the concrete structural layer and the solidified soil base layer: The surface connection is a large-area physical interlock achieved through the interface shear key; The point connection is a coupling connection made by the ground foundation and the HRB500 grade or higher double-layer bidirectional high-strength steel mesh configured inside the concrete structure layer. The concrete structural layer uses C35 or higher concrete with a permeability grade greater than or equal to P6 and a thickness greater than or equal to 400mm to form a heavy-duty integral slab structure.

[0014] Furthermore, in S3, before pouring concrete, the hardened solidified soil base surface is sprayed and moistened until it is saturated and surface-dry, and no organic isolation sheet is set; during the vibration process, cement mortar is guided to fill the microscopic voids between the coarse aggregate and the solidified soil.

[0015] A composite foundation floor, comprising, from bottom to top: The deep-solidified bearing base is an in-situ solidified soil with a depth of 2m or more, and it contains an embedded floor slab platform. The gradient interlocking transition zone is a composite layer containing cross-interface anchoring aggregate; The heavy-duty structural layer is a reinforced concrete slab with a thickness of 400mm or more, and is connected to the floor slab foundation by HRB500 grade steel bars. The functional protective surface layer includes an epoxy self-leveling layer with a thickness of 3mm to 5mm and a flatness of less than or equal to 2mm / 2m, and a solvent-free ultra-wear-resistant polyurethane surface layer with a thickness of greater than or equal to 2mm, a compressive strength of greater than or equal to 80MPa, and a Taber abrasion loss of less than or equal to 30mg.

[0016] Compared with the prior art, the technical solution of this application has the following beneficial technical effects: This invention utilizes the plastic rheological properties of the solidified soil base layer before it has fully set. Coarse aggregate is semi-embedded in the foundation surface to form a stable interfacial shear bond. Using this as a medium, the concrete structural layer is directly poured, forcing the concrete slurry to completely encapsulate the exposed ends of the aggregate. This creates a root-like mechanical interlocking structure on the contact surface. This "aggregate embedding + interlocking pouring" connection method completely abandons the traditional smooth isolation interface, coupling the originally independent flexible foundation and rigid slab into a unified load-bearing whole. When the floor is subjected to heavy braking or horizontal impact, the interfacial shear bond can effectively transfer the shear stress generated by the superstructure to the deep foundation, fundamentally eliminating the risk of interlayer slippage, effectively suppressing slab warping and fracture caused by the lack of interfacial constraints, and improving the overall stability and fatigue resistance of the composite flooring system. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the overall construction process of the composite foundation pavement of this invention. Figure 2 This is a process diagram of compartmentalized interval mixing and interfacial aggregate implantation in this invention; Figure 3 This is a distribution diagram of the composite foundation pavement structure layers of the present invention; Figure 4 This is a schematic diagram illustrating the working principle of the stress-inducing system of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] This invention provides a composite foundation slab and its construction method. Addressing the technical challenges of insufficient bearing capacity, interlayer slippage, and poor wear resistance in industrial flooring systems under adverse geological conditions such as soft soil and silty soil, this solution proposes a four-layer progressive system solution: deep curing, interface interlocking, structural integration, and functional protection. The core of this technical solution lies in abandoning the traditional practice of setting physical isolation layers such as PE films and geotextiles between the foundation and concrete structure layers. While these isolation layers can block water vapor from rising and prevent concrete slurry from seeping down to some extent, their smooth surface characteristics lead to a completely slip-prone surface with extremely low friction between the upper and lower structures. Under frequent braking, steering, or dynamic load impacts from heavy vehicles, the concrete slab, lacking horizontal anchorage and shear restraint from the base layer, is prone to relative displacement on the isolation layer surface, thus inducing slab warping, corner fractures, and misalignment at expansion joints.

[0020] This invention utilizes an interfacial aggregate gradient embedding process. During a specific plastic rheological window in the solidified soil base layer, coarse aggregate is semi-embedded in the soil surface, forming interfacial shear bonds similar to a "Nylon Fastener" structure. A concrete structural layer is then directly poured, utilizing the fluidity of the concrete slurry to comprehensively encapsulate the exposed aggregate ends. This achieves chemical bonding between cement paste and aggregate at the microscopic level and mechanical interlocking between the upper and lower structures at the macroscopic level, constructing a root-like fusion system between the foundation and the floor structure. Simultaneously, by intermittently setting floor slab platforms within the solidified soil base layer and pre-embedding upward-extending connecting components, rigid anchoring them to the high-strength steel mesh within the concrete structural layer, a dual-security mechanism of "surface connection + point connection" is formed. This effectively solves the fundamental defect of mechanical disconnect between the foundation and structural layer in traditional floor systems.

[0021] The construction method of a composite foundation pavement according to the present invention can be divided into four core steps according to the construction sequence, such as... Figure 1 As shown below, the technical points, process parameters and implementation details of each step are explained in detail.

[0022] Step S1: In-situ modification of deep foundation The purpose of this step is to crush and loosen the undisturbed foundation soil, and then deeply mix it with composite solidification materials to form a solidified soil base with structural strength. During implementation, it is first necessary to determine the properties of the undisturbed soil based on the geological survey report. In particular, for special soil types such as soft, silty undisturbed soil with high water content, high compressibility, and low bearing capacity, deep treatment technology must be employed. Soft, silty undisturbed soil refers to saturated soft clay commonly found in coastal mudflats, inland lakes and marshes, and reclaimed land areas. Its natural water content often exceeds the liquid limit, and its bearing capacity characteristic value is usually below 80 kPa. Without deep reinforcement, the subsequent ground structure will inevitably experience excessive settlement or even instability.

[0023] To achieve effective reinforcement, the in-situ modification solidification depth must be greater than or equal to 2 meters, a depth requirement far exceeding that of conventional surface hardening treatments. In practice, a high-powered deep-soil mixing pile machine or a bidirectional multi-shaft mixer must be used, ensuring the mixing blades effectively reach and thoroughly agitate the entire soil layer within a 2-meter depth range. During the mixing process, the composite solidification material consists of silicate cement, soil solidification enzymes, and hydrophobic modifying components. For example, the silicate cement can be PO 42.5 grade or PO... The dosage of 52.5 grade ordinary Portland cement is determined based on the moisture content and organic matter content of the undisturbed soil, typically ranging from 8% to 15% of the soil's dry weight. Soil solidification enzymes are chemical reagents based on the principle of ion exchange, capable of replacing adsorbed cations on the surface of soil particles, disrupting the double electric layer structure around the soil particles, and significantly reducing the thickness of the bound water film on the surface of the soil particles. This significantly reduces the optimum moisture content of the soil and improves compaction. The dosage of these enzymes is typically 0.01% to 0.05% of the soil weight. Hydrophobic modifiers are the key material for achieving "construction without an isolation layer" in this scheme. The material can be an organosilane coupling agent, calcium stearate powder, or modified acrylic emulsion. Its mechanism of action is to fill the micropores of the solidified soil and form a modified film with hydrophobic properties, changing the water contact angle of the capillary wall from a hydrophilic state (less than 90 degrees) to a hydrophobic state (greater than 90 degrees), similar to the hydrophobic effect on the surface of a lotus leaf. This makes the impermeability grade of the solidified soil base layer reach P6 or above, which can actively block the upward transmission path of underground capillary water vapor, completely replacing the function of laying PE moisture-proof film in traditional processes, and avoiding the artificial slippage surface formed by physical isolation layer.

[0024] In large-scale construction, deeply solidified soil exhibits significant volume shrinkage during the initial hardening stage (especially in the first 24 to 48 hours). This shrinkage includes both chemical shrinkage caused by the consumption of free water during cement hydration and drying shrinkage caused by the evaporation of moisture from the solidified soil surface. If a one-time full-coverage construction method is used, the accumulated shrinkage stress has nowhere to be released, easily leading to wide and irregular through cracks in the base layer. Therefore, this invention employs a compartmentalized, intermittent mixing process, a construction technique that borrows the principle of the skip-concrete method for large-volume concrete and innovatively applies it to geotechnical engineering. In practice, the construction area is first divided into several standard grid units. The grid size can be determined based on the operating radius of the construction machinery and the dimensions of the site's column grid, typically using 6m x 6m or 9m x 9m squares. Then, construction is carried out intermittently, starting with odd-numbered squares and then moving to even-numbered squares, similar to the black and white squares of a chessboard. The key control parameter is that the construction interval between adjacent grids is no less than 24 hours. This time window is set based on the setting and hardening law of solidified soil: within 24 hours, the first odd-numbered grids of solidified soil have completed initial setting and experienced most of the early and severe shrinkage stage. Their volume gradually stabilizes and forms a solid boundary with a certain rigidity. When the subsequent even-numbered grids are constructed, the shrinkage stress of the newly poured solidified soil is rigidly constrained by the hardened odd-numbered grids. The shrinkage deformation is limited to the range of a single grid and cannot be transmitted outward. In fact, the volume shrinkage stabilization period of the first grid is used as the stress release boundary of the subsequent grid, thereby breaking down the large-area cumulative shrinkage stress into zero and effectively eliminating the hidden danger of base layer cracking.

[0025] To further enhance the overall anti-settlement and anti-warping capabilities of the floor system, step S1 also includes a node reinforcement process. While deep soil mixing is being carried out, floor piers are intermittently installed within the solidified soil base at key locations such as column grid nodes, below equipment foundations, and intersections of heavy-duty passageways. The construction methods for these floor piers are diverse. Pit pits can be pre-excavated and concrete piers poured before mixing and solidifying the soil, or high-strength, locally thickened zones can be formed during the mixing and solidification process by deepening and intensifying the mixing process and increasing the cement content. Regardless of the method used, the key technical point is that upwardly extending connecting components are pre-embedded within the floor piers. These connecting components can be in the form of pre-embedded bolts, L-shaped or U-shaped reinforcing bars, or pre-embedded steel plates. The upward extension height should be determined based on the thickness of the subsequent concrete structural layer and the thickness of the reinforcing steel protective layer to ensure effective overlap or welding with the upper reinforcing mesh. This allows for rigid anchoring with the concrete structural layer in subsequent steps, laying the physical foundation for constructing a "point-surface combined" dual connection system.

[0026] After deep mixing, the surface of the solidified soil needs to be initially leveled. This can be done using a bulldozer or grader for rough leveling, followed by initial compaction with a light roller. The purpose of initial compaction is not to achieve final density, but to create a relatively flat and dense surface, facilitating the subsequent implantation of interface aggregates. After solidification, quality testing should be conducted. A characteristic value of the solidified foundation bearing capacity greater than or equal to 150 kPa is a mandatory technical indicator for the foundation treatment effect of this invention. This bearing capacity value ensures that the solidified soil base layer can not only serve as an operating platform for subsequent heavy construction machinery such as concrete mixer trucks and laser screeds, but also participate in the overall stress distribution of the floor system as a permanent load-bearing structure, effectively reducing uneven settlement. Bearing capacity testing can be conducted using in-situ testing methods such as plate load tests or dynamic penetration tests.

[0027] Step S2: Gradient implantation of interfacial aggregate This step is the most innovative core technology of this invention. Its essence is to create a gradient transition layer that is "neither pure soil nor pure stone," transforming the traditional smooth interface into a rough, mechanically interlocked interface. The implementation process is as follows: During the plastic rheological window period after the solidified soil base layer has been leveled and is not yet fully set, coarse aggregate is evenly spread on its surface. Mechanical pressure is then used to press the coarse aggregate into the soil, resulting in a semi-embedded state where the lower part is anchored to the soil and the upper part is exposed to the air. After the solidified soil hardens, interfacial shear bonds are formed.

[0028] The so-called plastic rheological window period refers to the period after initial compaction and leveling of solidified soil slurry, when the penetration resistance value is between 0.5 MPa and 1.5 MPa, and the soil exhibits thixotropic properties. Accurately grasping this time window is crucial to the success of rock-planting. If the soil is too soft and in a fluid state, the stones will completely sink and disappear into the soil, failing to form a semi-embedded state; if the soil is too hard and close to final setting, the stones cannot be pressed in or will be crushed during the pressing process. The penetration resistance value can be quickly measured on-site using a portable penetrometer. The range of 0.5 MPa to 1.5 MPa is the optimal parameter obtained through extensive experimental verification. Thixotropic properties refer to the physical characteristic of soil that, when at rest, exhibits a certain strength and shape retention capacity as a solid, but when subjected to mechanical vibration or shearing forces such as the vibration and compaction of a road roller, its internal flocculated structure is temporarily disrupted, and its viscosity decreases instantaneously, exhibiting fluid-like properties. When the external force stops, it can quickly recover its strength. During this window period, the soil possesses the plastic yield stress necessary to allow aggregate indentation, ensuring that applied mechanical force can press the aggregate into the soil. Simultaneously, it maintains the cohesion of the aggregate in a semi-suspended state, ensuring that the indented aggregate is supported by the soil and does not continue to sink. This window typically occurs within 2 to 6 hours after mixing, but the specific timing is influenced by various factors such as temperature, cement type, cement content, and initial soil moisture content. In hot seasons, the window may appear earlier and be shorter, while in cold seasons it may appear later and be longer. During construction, the optimal timing for planting the aggregate should be determined through test sections based on actual conditions.

[0029] The coarse aggregate should be multi-faceted crushed stone with a Mohs hardness of 6 or higher and a particle size of 20mm to 30mm. The selection of materials is subject to strict technical requirements. For example, igneous hard aggregates such as basalt crushed stone, granite crushed stone, or diabase crushed stone can be used. These aggregates have high hardness, high strength, and multi-faceted characteristics, providing sufficient mechanical interlocking force. Rounded aggregates such as river pebbles are strictly prohibited because their smooth surfaces prevent the formation of effective shear bonds even when embedded in the soil. Soft aggregates such as sedimentary rocks like limestone and dolomite should also be avoided, as their Mohs hardness is typically below 6, making them prone to crushing and failure during the compaction process. The choice of particle size is also important. The optimal range of 20mm to 30mm is determined after comprehensively considering the control of embedding depth and the convenience of construction operation. If the particle size is too small, such as crushed stone below 10mm, the embedding depth is too shallow and the anchoring force is insufficient. If the particle size is too large, such as crushed stone above 50mm, the cohesion of the soil is insufficient to support the weight of the aggregate during the plastic rheological window. At the same time, the large-diameter aggregate also has a greater destructive effect on the soil structure.

[0030] The spreading of coarse aggregate should ensure uniform distribution. It can be done manually or mechanically. For large-area construction, automatic spreading machines are recommended for better control of the spreading density. Immediately after spreading, compaction should be carried out. Mechanical pressure should be applied until the embedment depth of the coarse aggregate is 1 / 2 to 2 / 3 of its geometric height—a golden ratio verified through extensive testing. This can be done using a light vibratory roller with static pressure and weak vibration, or a plate vibratory compactor. The key is to precisely control the embedment depth: if the embedment depth is less than 1 / 2, the anchorage length of the aggregate in the soil is insufficient, making it easy for it to be kicked away or floated by the impact force of the concrete slurry during subsequent concrete pouring, failing to form an effective mechanical bond; if the embedment depth is greater than 2 / 3, too little of the aggregate is exposed to air, failing to form sufficient bond strength and adhesion area with the upper concrete, also failing to achieve the interlocking effect. During compaction, the surface coverage of coarse aggregate on the solidified soil surface should be controlled at 30% to 40%. This coverage does not require covering the entire surface, but rather leaving sufficient gaps between soil particles so that the subsequently poured concrete slurry can contact the bottom solidified soil surface, achieving direct bonding between the concrete and the solidified soil. During compaction, due to the mutual compression and lateral displacement between aggregates, a macroscopic meshing surface with a roughness Ra greater than or equal to 10 mm is formed by the lateral squeezing between aggregates. This roughness far exceeds the Ra value of conventional concrete interface roughening treatment (usually only 1 to 2 mm), forming a true physical "teeth" structure.

[0031] After the above operations, the coarse aggregate is semi-embedded, with its lower part anchored to the soil and its upper part exposed to the air, similar to a nail half-driven into a wooden board. The site then needs to be protected to prevent damage from personnel and vehicles, allowing the solidified soil to harden and form interfacial shear keys. The hardening time of the solidified soil is typically 3 to 7 days, depending on temperature conditions and the formulation of the solidifying material. The hardening standard can be determined by testing the surface hardness of the solidified soil; generally, a surface rebound value of 25 MPa or higher is required before proceeding to the next step of construction.

[0032] Step S3: Interlocking Casting of Structural Layers The core technical point of this step is to directly pour a concrete structural layer onto the shear key at the interface, utilizing the fluidity of the concrete slurry to completely encapsulate the exposed parts of the coarse aggregate, forming a root-like mechanical interlock between the foundation and the slab structure. Interface pretreatment is essential before pouring; the hardened, solidified soil base surface must be spray-wetted until it reaches a saturated surface-dry state. This step is crucial but often overlooked. The so-called saturated surface-dry state, or SSD state for short, refers to a state where there is no visible water film on the surface of the porous material, but the internal pores are saturated with water. This state ensures that the interface does not absorb moisture from the freshly mixed concrete, preventing the cement at the interface from failing to fully hydrate and forming a loose layer, while also ensuring that there is no standing water on the surface to dilute the concrete slurry and affect the water-cement ratio. Spray wetting should be carried out 1 to 2 hours before pouring, using a sprayer or water truck. The standard for judgment is that the surface color darkens and there are no obvious water marks when touched. It must also be emphasized that no organic isolation sheets are used, and it is strictly forbidden to lay any form of isolation layer material such as PE film or geotextile on the solidified soil surface. This is a significant feature that distinguishes this invention from traditional processes.

[0033] Concrete pouring should be continuous to avoid cold joints. During pouring, the fluidity of the concrete slurry should be used to completely encapsulate the exposed parts of the coarse aggregate. The fluidity of freshly mixed concrete allows the cement mortar to flow naturally and fill the tiny voids around the aggregate. The vibration process plays a crucial technical role in this step. During vibration, the cement mortar is guided to fill the microscopic voids between the coarse aggregate and the solidified soil. The vibrator should be inserted at an angle, with the insertion depth ensuring it does not touch the solidified soil base layer. Vibration allows the concrete slurry to penetrate downwards, completely encapsulating each semi-embedded aggregate, making each aggregate a miniature "shear pin" connecting the upper and lower structural layers. This connection method, at the microscopic level, is the chemical bonding and physical binding of the cement paste to the aggregate; at the macroscopic level, it is the mechanical interlocking of the upper and lower structures, ultimately forming a root-like mechanical interlocking between the foundation and the floor structure, as strong and reliable as the roots of a tree deeply embedded in the soil.

[0034] To address the complex stress conditions faced by heavy-duty flooring, this invention also constructs a dual connection system that combines points and surfaces. The so-called dual connection refers to the simultaneous use of both surface connection and point connection methods: Surface connection is a large-area physical interlocking achieved through the interface shear keys, namely the aforementioned stone interlocking mechanism. Its main function is to provide anti-slip capability across the entire plane, effectively resisting the horizontal braking force generated by vehicle braking and sharp turns, as well as the thermal expansion and contraction shear force of the structural layer relative to the base layer caused by temperature changes. Point connection is a coupling connection through the HRB500 grade or higher double-layer bidirectional high-strength steel mesh configured inside the concrete structural layer. Specifically, before pouring concrete, the steel bars are tied, and the double-layer bidirectional steel mesh is welded or mechanically connected to the connecting components pre-embedded in the floor slab in step S1 to form a rigid vertical anchor. Its main function is to provide strong pull-out resistance in the vertical direction, effectively resisting the corner warping of the concrete slab (this warping is caused by the reverse curvature deformation due to the temperature and humidity gradient difference between the top and bottom surfaces of the concrete slab) and the local bending moment caused by uneven settlement of the soft foundation.

[0035] The concrete structural layer uses C35 or higher concrete with a permeability grade of P6 or greater and a thickness of 400mm or greater, forming a heavy-duty integral slab structure. For example, C35, C40, or C45 grade ready-mixed concrete can be used. To achieve a permeability grade of P6 or higher, an expansion agent and a high-efficiency water-reducing agent should be added to the concrete mix design, controlling the water-cement ratio to be no greater than 0.45. A thickness of 400mm or more is typical of ultra-heavy-duty industrial floor design standards, capable of withstanding loads under extreme conditions such as port container yards and heavy machinery processing plants. The reinforcement should use hot-rolled ribbed steel bars of HRB500 grade or higher strength, arranged in a double layer and bidirectional pattern. The spacing of the steel bars can be determined based on load calculations, typically 150mm to 200mm. After the concrete pouring is completed, surface treatment should be carried out promptly. A laser screed can be used for finishing, controlling the surface flatness to within 5mm / 2m, creating conditions for subsequent surface layer construction. Concrete curing should follow standard curing specifications, including covering with film or burlap sacks and sprinkling water to keep it moist, with a curing time of no less than 14 days.

[0036] Step S4: High-precision surface layer construction The purpose of this step is to treat the surface of the concrete structure after it has cured and apply a wear-resistant protective layer. First, the concrete surface needs to be ground, using a shot blasting machine or grinder to remove surface laitance and small protrusions, exposing the solid concrete base. After grinding, it should be thoroughly cleaned, using an industrial vacuum cleaner to remove all dust, ensuring the surface is clean and dry.

[0037] The surface layer system consists of two layers: a bottom layer of epoxy self-leveling compound with a thickness of 3mm to 5mm and a flatness of ≤2mm / 2m; and an upper layer of solvent-free, ultra-wear-resistant polyurethane with a thickness of ≥2mm, a compressive strength of ≥80MPa, and a Taber abrasion loss of ≤30mg. Solvent-free epoxy self-leveling materials should be used for the epoxy self-leveling layer. These materials have extremely low viscosity and excellent leveling properties, allowing them to flow automatically under gravity and form a highly flat surface. During construction, first apply an epoxy primer to enhance adhesion to the concrete substrate. Then, pour the prepared epoxy self-leveling material onto the ground and spread it evenly with a notched squeegee. The material will automatically level itself. Use a defoaming roller to roll the surface and remove air bubbles. The flatness of the cured epoxy layer should be ≤2mm / 2m, which can be checked using a 2-meter straightedge. This flatness level meets the requirements of high-end manufacturing for flooring. In addition to providing a super-smooth bottom surface, the epoxy self-leveling layer also serves as an adhesive transition layer for the polyurethane top layer because epoxy resin and polyurethane have good compatibility and adhesion.

[0038] The polyurethane surface layer should be a solvent-free polyurethane ultra-wear-resistant coating. This type of material is a two-component system composed of polyether polyol and isocyanate. After curing, it forms an elastomer with a micro-crosslinked structure, possessing both high hardness and high toughness. Its compressive strength is greater than or equal to 80 MPa, far exceeding the approximately 50 MPa of ordinary epoxy coatings; its Taber abrasion value is less than or equal to 30 mg (test conditions: CS17 grinding wheel, 1000g load, 1000 revolutions), while the Taber abrasion value of ordinary epoxy coatings is usually between 60 and 100 mg. The wear resistance of the polyurethane surface layer of this invention is 2 to 3 times that of ordinary epoxy. During construction, components A and B should be mixed evenly according to the specified ratio and applied evenly with a trowel or scraper, with a thickness controlled at more than 2 mm. Construction should be completed within 24 hours after the epoxy self-leveling layer has cured to ensure interlayer adhesion. The polyurethane coating should be cured for at least 7 days before being put into use.

[0039] Before step S4, the present invention can also implement an upper and lower alignment stress induction procedure, which is a precise crack control technology. Traditional floor slab cutting often only occurs on the surface, neglecting the impact of the bottom base layer joints on the superstructure, leading to crack reflection. For example... Figure 4As shown, the stress induction procedure of the present invention includes three stages: The first stage is the in-situ modification stage of S1, in which inverted V-shaped or strip-shaped bottom induction elements are pre-embedded at the compartment joints of the solidified soil base. These induction elements can be crack induction strips made of PVC plastic or wooden strips, and the pre-embedding depth is 1 / 3 to 1 / 2 of the thickness of the solidified soil layer. Their function is to artificially create a vertical weak surface at the bottom, guiding the concentrated release of shrinkage stress at this point; The second stage is the concrete pouring stage of S3, in which the three-dimensional coordinates of the bottom induction elements are recorded using a positioning instrument. A total station or RTK-GPS can be used for precise positioning and recording of coordinate data, because the bottom induction elements will be completely covered and invisible after the concrete is poured; The third stage is before the implementation of S4, in which a slit is cut on the surface of the concrete structural layer according to the coordinates. A road cutter or a special floor slit cutter is used, and the slit depth is 1 / 3 of the concrete thickness, so that the effective induction area of ​​the surface slit covers the centerline of the bottom induction element. The allowable deviation range is ±50mm, thereby forming a stress release channel that runs through the upper and lower structural layers. This top-to-bottom alignment design ensures that in the event of cracking, the crack will appear vertically and regularly along the predetermined cut position, rather than as a chaotic reflective crack, which facilitates later maintenance and repair.

[0040] The composite foundation pavement prepared according to the above construction method, such as Figure 3 As shown, its structural features consist of four functional layers from bottom to top, forming a complete floor system. The bottom layer is a deep-solidified bearing base, which is in-situ solidified soil with a depth of ≥2m and an embedded floor platform. This layer provides stable and reliable foundation support and is the foundation of the entire floor system. The second layer is a gradient interlocking transition zone, a composite layer containing interfacial anchored aggregate. This is a special interface layer combining soil, stone, and concrete. Although its thickness is only 20 to 30mm, the size of the aggregate particles, its role is the core of the entire system, providing interlayer shear resistance. The third layer is a heavy-duty structural layer, a reinforced concrete slab with a thickness of ≥400mm, connected to the floor platform by HRB500 grade steel bars. This layer is the main load-bearing unit of the floor system, bearing all service loads. The top layer is the functional protective surface layer, which is further divided into two sub-layers: the base layer is an epoxy self-leveling layer with a thickness of 3mm to 5mm and a flatness of less than or equal to 2mm / 2m, providing a super flat base surface; the surface layer is a solvent-free ultra-wear-resistant polyurethane surface layer with a thickness of greater than or equal to 2mm, a compressive strength of greater than or equal to 80MPa, and a Taber abrasion loss of less than or equal to 30mg, providing superior wear resistance, impact resistance, and chemical corrosion resistance.

[0041] To further illustrate the implementation effect and applicability of the technical solution of the present invention, three examples for different working conditions and geological conditions are provided below.

[0042] Example 1: Coastal soft soil foundation logistics and warehousing flooring project This example is applied to a warehouse flooring project in a large logistics park in the Yangtze River Delta. The project site is located on a coastal alluvial plain with challenging geological conditions. According to the geological survey report, the surface layer of the site is approximately 8 meters thick silty clay with a natural moisture content of 48% to 55%, a liquid limit of 42%, a plastic limit of 22%, and a natural void ratio of 1.2 to 1.4, classifying it as typical highly compressible soft soil. The undisturbed soil bearing capacity is only 65 kPa, and the groundwater level is relatively high at a depth of 0.8 meters. The warehouse is designed as a steel structure factory building with a span of 30 meters and a column spacing of 9 meters. The floor must withstand frequent operation by a 3-ton electric forklift, and the design service life is over 20 years.

[0043] like Figure 2 As shown, the construction plan is as follows: Step S1, in-situ foundation modification stage, uses a two-way mixing pile machine to deeply treat the original silt soil. The mixing depth is set at 2.8 meters, exceeding the design minimum by 2 meters to ensure safety. The composite curing material formula is 13% PO 42.5 silicate cement, 0.03% liquid soil curing enzyme, and 0.6% organosilane emulsion. All dosages are percentages of soil dry weight. During the mixing process, a compartmentalized interval process is adopted, dividing the 4500 square meter construction area into 56 standard grids of 9 meters by 9 meters. Construction is carried out in a checkerboard skip-compartment sequence, with a 36-hour interval between odd-numbered and even-numbered compartments. A foundation platform is set under each column, with dimensions of 1.2 meters by 1.2 meters and a depth of 1.5 meters, using C30 concrete. Four 25mm diameter HRB500 steel bars are pre-embedded in each foundation, extending upwards 600mm as connecting components. A plate load test was conducted 28 days after curing, and the measured characteristic value of the foundation bearing capacity reached 195 kPa, which meets the design requirement of greater than or equal to 150 kPa.

[0044] In step S2, the interface aggregate implantation stage, after the solidified soil was mixed and initially leveled, penetration resistance monitoring was conducted. The results showed that the penetration resistance reached 0.9 MPa approximately 5 hours after mixing, indicating significant thixotropy in the soil and confirming the entry into the plastic rheological window. Coarse aggregate was immediately spread, using basalt crushed stone with a particle size of 20-25 mm and a Mohs hardness of 7. The spreading density was controlled at approximately 75 kg per square meter to achieve a 35% coverage rate. Immediately after spreading, a 3-ton light vibratory roller was used for compaction, first with static compaction followed by a weak vibration compaction. After completion, 10 points were randomly selected for embedding depth testing. The average embedding depth of the crushed stone was measured to be 13 mm, accounting for 59% of its average particle size of 22 mm, meeting the technical requirement of 1 / 2 to 2 / 3. The surface roughness, measured by a profilometer, was Ra=12 mm, meeting the requirement of greater than or equal to 10 mm.

[0045] Step S3, the structural layer pouring stage, is carried out 5 days after the solidified soil has hardened. The base layer is sprayed with water the afternoon before pouring to ensure it reaches a saturated, dry state. The entire process strictly adheres to the principle of not laying any isolation layer. Reinforcing steel is tied using HRB500 grade 16mm diameter threaded steel, arranged in a double layer and bidirectional pattern with a spacing of 150mm. The reinforcing mesh is connected to the pre-embedded pile cap reinforcement using lap welding, with a welding length of not less than 10 times the steel diameter, i.e., 160mm. C40 grade P8 commercial concrete is used, with UEA expansion agent and polycarboxylate superplasticizer added to the mix design. The measured slump is 180mm. The pouring thickness is 420mm, exceeding the design minimum of 400mm. During pouring, an immersion vibrator is used for compaction, inserted at an angle without touching the bottom to ensure the cement mortar fully coats the interface aggregate. After pouring, a laser screed is used for surface finishing, with a measured flatness of 4.5mm / 2m. The concrete was cured by covering it with a membrane and sprinkling water, and the curing time was 21 days.

[0046] Step S4, the surface layer construction stage, is carried out after the concrete curing is completed. First, a shot blasting machine is used to treat the surface, removing laitance and minor protrusions, followed by cleaning with an industrial vacuum cleaner. The epoxy self-leveling layer uses a two-component solvent-free epoxy material. First, one coat of epoxy primer is applied by roller, and after drying, the epoxy self-leveling layer is applied to a thickness of 4mm. A defoaming roller is used to remove air bubbles. After curing, the flatness is checked with a 2-meter straightedge; the maximum measured deviation is 1.8mm, meeting the requirement of less than or equal to 2mm / 2m. The polyurethane ultra-wear-resistant surface layer uses a solvent-free polyurethane coating from a certain brand, mixed in a ratio of A:B=1:2, and applied with a trowel to a thickness of 2.5mm. After curing, samples are sent for testing. The measured compressive strength is 87MPa, and the measured Taber abrasion value is 26mg, both meeting technical requirements. During the test, it withstood more than 50 round trips daily by a 3-ton forklift, with no cracking, dust, or significant wear on the floor surface, maintaining good flatness, and receiving excellent customer feedback.

[0047] Example 2: Inland high groundwater level cold chain logistics flooring project This example is applied to a flooring project for a cold chain logistics center in Central China. The project is unique in that it has an extremely high groundwater level and needs to withstand the frost heave of the cold storage environment. The site's geology consists of silty clay with a groundwater level only 0.3 meters deep, making it a region rich in unconfined groundwater. The original soil bearing capacity is 80 kPa. The cold chain warehouse is designed to operate at -18 degrees Celsius, and the flooring needs to address the triple challenges of moisture control, frost heave resistance, and forklift load tolerance.

[0048] For the special conditions of high groundwater levels, the proportion of the hydrophobic modification components was optimized in step S1. Nano-modified silane powder was selected as the hydrophobic agent, and its dosage was increased to 0.8% to ensure that the micropores of the solidified soil were covered by a denser hydrophobic film. The solidification depth was set at 2.2 meters. After solidification, the measured impermeability grade reached P10, far exceeding the basic requirement of P6, effectively blocking the upward channel of capillary water. In step S2, due to the low winter temperature during construction, the plastic rheological window was delayed to about 8 hours after mixing. Stone planting was carried out when the penetration resistance monitoring reached 1.3 MPa. Granite crushed stone was selected as the coarse aggregate, and the particle size range was expanded to 25 to 30 mm to enhance the anchoring force. In step S3, the thickness of the concrete structure layer was increased to 450 mm to enhance the resistance to frost heave, and an air-entraining agent was added to the concrete mix to improve the frost resistance grade. In step S4, an epoxy sealing primer is added between the epoxy self-leveling layer and the concrete layer to further enhance the moisture-proof performance. After two complete freeze-thaw cycles, the ground showed no signs of dampness, frost heave cracking, or peeling, demonstrating significant moisture-proof and frost-proof effects.

[0049] Example 3: Overload flooring project for heavy machinery processing plant This example is applied to the flooring project of a heavy machine tool processing workshop in a large equipment manufacturing enterprise in Southwest China. The project is characterized by the need to withstand extremely heavy point loads and dynamic impact loads. The workshop houses multiple CNC gantry milling machines and floor-type boring machines, each weighing between 80 and 120 tons, generating strong vibrations during processing. The site's geological conditions consist of silty clay with a bearing capacity of 90 kPa, requiring reinforcement treatment.

[0050] For ultra-heavy-load conditions, the density of the floor piers in step S1 is increased, with piers installed around the foundation of each piece of equipment. The pier dimensions are increased to 1.5 meters by 1.5 meters, and the depth is 1.8 meters. In step S3, the thickness of the concrete structural layer is increased to 500 mm, and the reinforcement uses HRB600 grade 20 mm diameter threaded steel bars. The spacing between the two layers is reduced to 120 mm, and the concrete grade is upgraded to C45. To further enhance the impact resistance of the floor, nano-silica reinforcing agents are added to the polyurethane surface layer in step S4, resulting in a compressive strength of 92 MPa and a Taber abrasion reduction to 23 mg. This allows the floor to withstand long-term static loads and frequent dynamic impacts from heavy equipment. The floor structure remains stable, without settlement, cracking, or warping. The flatness of the ground around the equipment foundation is maintained within 2 mm / 2 m, meeting high-precision processing requirements.

[0051] The three embodiments described above address three typical working conditions: soft soil, high groundwater level, and heavy load, respectively, fully verifying the applicability, reliability, and superiority of the technical solution of this invention. All three projects achieved integrated synergistic stress distribution among the foundation, structure, and surface layer, effectively solving technical problems such as interlayer slippage, moisture-proof failure, and poor wear resistance inherent in traditional flooring systems. Compared to traditional pile-raft foundation schemes, the overall cost is reduced by 15% to 25%, and the construction period is shortened by 25% to 35%, resulting in significant economic and social benefits.

Claims

1. A construction method for a composite foundation slab, characterized in that, Includes the following steps: S1. Deep foundation in-situ modification: The original foundation soil is crushed and loosened, and then mixed with composite solidification materials for deep mixing to form a solidified soil base with structural strength. S2. Gradient implantation of interfacial aggregate: During the plastic rheological window period when the solidified soil base is leveled and not yet fully set, coarse aggregate is evenly spread on its surface and mechanically pressed into the soil, so that the coarse aggregate is in a semi-embedded state with the lower part anchored to the soil and the upper part exposed to the air. After the solidified soil hardens, an interfacial shear bond is formed. S3. Interlocking pouring of structural layer: The concrete structural layer is poured directly on the shear key of the interface, and the fluidity of the concrete slurry is used to wrap the exposed part of the coarse aggregate in all directions, forming a root-like mechanical interlock between the foundation and the floor structure. S4. High-precision surface layer construction: After the concrete structure layer has cured, its surface is treated and a wear-resistant protective layer is constructed.

2. The construction method of a composite foundation slab according to claim 1, characterized in that, In step S1, a compartmentalized, intermittent stirring process is employed, specifically including: The construction area is divided into several standard grid units, and construction is carried out in an interval sequence of odd-numbered grids first and even-numbered grids later. The construction interval between adjacent grids is not less than 24 hours. The volume shrinkage stabilization period of the grids constructed earlier is used as the stress release boundary of the grids constructed later.

3. The construction method of a composite foundation slab according to claim 1, characterized in that, In S1, for soft silty undisturbed soil, the solidification depth of the in-situ modification is greater than or equal to 2m, and the characteristic value of the bearing capacity of the solidified foundation is greater than or equal to 150kPa. Step S1 further includes a node reinforcement process: a floor slab platform is set at intervals in the solidified soil base layer, and an upwardly extending connecting member is pre-embedded in the floor slab platform for rigid anchoring with the concrete structural layer in subsequent steps.

4. The construction method of a composite foundation slab according to claim 3, characterized in that, The composite curing material is composed of silicate cement, soil curing enzyme, and hydrophobic modifying components; The hydrophobic modified component fills the micropores of the solidified soil and forms a modified membrane with hydrophobic properties, so that the impermeability grade of the solidified soil base reaches P6 or above, blocking the upward transmission path of underground capillary water vapor.

5. The construction method of a composite foundation slab according to claim 1, characterized in that, In S2, the coarse aggregate is selected as multi-faceted crushed stone with a Mohs hardness greater than or equal to 6 and a particle size of 20mm to 30mm. The mechanical pressure is applied to the coarse aggregate to an embedment depth of 1 / 2 to 2 / 3 of its own geometric height, and the coarse aggregate has a planar coverage of 30% to 40% on the surface of the solidified soil. The lateral squeezing between the aggregates forms a macroscopic meshing surface with a roughness Ra greater than or equal to 10 mm.

6. The construction method of a composite foundation slab according to claim 5, characterized in that, The plastic rheological window period refers to the period during which the penetration resistance of the solidified soil slurry is between 0.5 MPa and 1.5 MPa after initial compaction and leveling, and the soil exhibits thixotropic properties. During this window period, the soil possesses the plastic yield stress that allows the aggregate to be pressed in, as well as the cohesion to maintain the semi-suspended state of the aggregate.

7. The construction method of a composite foundation slab according to claim 1, characterized in that, It also includes an upper and lower alignment stress induction program, specifically including: During the in-situ modification stage of S1, inverted V-shaped or strip-shaped bottom guide elements are pre-embedded at the compartment joints of the solidified soil base layer. During the concrete pouring stage of S3, the three-dimensional coordinates of the bottom guide are recorded using a positioning instrument; Before S4 is implemented, a slit is cut on the surface of the concrete structure layer according to the coordinates, so that the effective induction zone of the surface slit covers the center line of the bottom induction element, forming a stress release channel that runs through the upper and lower structural layers.

8. The construction method of a composite foundation slab according to claim 3, characterized in that, A dual connection system with point-surface integration is constructed between the concrete structural layer and the solidified soil base layer: The surface connection is a large-area physical interlock achieved through the interface shear key; The point connection is a coupling connection made by the ground foundation and the HRB500 grade or higher double-layer bidirectional high-strength steel mesh configured inside the concrete structure layer. The concrete structural layer uses C35 or higher concrete with a permeability grade greater than or equal to P6 and a thickness greater than or equal to 400mm to form a heavy-duty integral slab structure.

9. The construction method of a composite foundation slab according to claim 1, characterized in that, In S3, before pouring concrete, the hardened solidified soil base surface is sprayed and moistened until it is saturated and dry, and no organic isolation sheet is set; during the vibration process, cement mortar is guided to fill the micro-voids between the coarse aggregate and the solidified soil.

10. A composite foundation slab prepared based on the construction method according to any one of claims 1 to 9, characterized in that, The ground surface, from bottom to top, includes: The deep-solidified bearing base is an in-situ solidified soil with a depth of 2m or more, and it contains an embedded floor slab platform. The gradient interlocking transition zone is a composite layer containing cross-interface anchoring aggregate; The heavy-duty structural layer is a reinforced concrete slab with a thickness of 400mm or more, and is connected to the floor slab foundation by HRB500 grade steel bars. The functional protective surface layer includes an epoxy self-leveling layer with a thickness of 3mm to 5mm and a flatness of less than or equal to 2mm / 2m, and a solvent-free ultra-wear-resistant polyurethane surface layer with a thickness of greater than or equal to 2mm, a compressive strength of greater than or equal to 80MPa, and a Taber abrasion loss of less than or equal to 30mg.

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