A method for reinforcing a pit type static pressure pile foundation of a brick-concrete structure without a ground ring beam

Abstract

This invention provides a method for reinforcing the foundation of brick-concrete structures without ground beams using pit-type static pressure piles. The method comprises two main phases: Phase 1 involves stiffness enhancement, including excavating a foundation trench to add a new ground beam, creating openings in the walls to accommodate shear keys and through-wall reinforcement, followed by surface cleaning, reinforcement binding, concrete grouting, and curing. This transforms the masonry structure without a ground beam into a unified load-bearing system. Phase 2 involves pit-type static pressure pile replacement. Through staged static pressure pile driving, pile splicing welding, and pile top steel plate + steel pipe replacement, the load of the upper wall is transferred to the deep static pressure piles. Reinforcement is completed after backfilling and consolidation of the pilot trench. This invention relies on shear keys and through-wall reinforcement to achieve reliable interlocking and force transfer between the new ground beam and the existing masonry. It minimizes construction disturbance, has low cost, and can simultaneously achieve foundation reinforcement, building correction, and wall crack closure. It is suitable for treating various soft foundations such as collapsible loess and silty soil, and features standardized processes, controllable quality, and high engineering application value.

Description

Technical Field

[0001] This invention belongs to the field of foundation reinforcement construction technology for brick-concrete buildings; in particular, it relates to a method for reinforcing pit-type static pressure pile foundations of brick-concrete structures without ground beams. Background Technology

[0002] Currently, urban renewal and renovation projects for old residential areas are being carried out in my country. A large number of self-built brick-concrete houses and old public houses from the last century lack ground beams and structural columns, resulting in extremely poor overall rigidity. Affected by soft foundations such as collapsible loess, silty soil, and artificial fill, uneven foundation settlement, wall cracking, and house tilting are common problems.

[0003] Existing pit-type static pressure pile reinforcement technology is suitable for cohesive soil, silt, and fill sites with low groundwater levels, offering advantages such as minimal disturbance, low cost, and reliable reinforcement. However, traditional pit-type static pressure pile construction requires a complete ground beam to evenly transfer the load from the upper wall to the static pressure piles. Without a ground beam, brick-concrete buildings lack continuous load-bearing components, and direct static pressure construction can cause localized stress concentration, crack expansion, and the risk of building collapse. Conventional reinforcement techniques cannot be directly applied in this way.

[0004] Among existing reinforcement methods, enlarging the foundation, grouting, and root piles have drawbacks such as large excavation volume, limited reinforcement depth, and high cost. For brick-concrete houses without ground beams, the industry lacks a complete set of standardized construction methods that first strengthen the overall rigidity of the house and then implement pit-type static pressure pile replacement.

[0005] In existing technologies, simply adding a new ground beam can only improve the overall integrity of the foundation, without the addition of shear keys and through-wall reinforcement to achieve force transfer between the wall and the new ground beam. Conventional pit-type static pressure piles must rely on the original ground ring beam for load-bearing. The industry has not disclosed an integrated process of "first constructing a new ground beam with shear keys and through-wall reinforcement to strengthen the overall rigidity, and then implementing static pressure pile replacement after curing to the required standards," which leaves a technological gap. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing pit-type static pressure pile technology, which cannot be directly applied to brick-concrete houses without ground beams. It solves the technical problems of insufficient integrity of masonry houses without ground beams, uneven load transfer during static pressure construction, and easy cracking and tilting of walls. At the same time, it addresses the problems of foundation settlement, wall cracks, and house tilting in old brick-concrete houses, and provides an integrated construction method of stiffness reinforcement and static pressure pile replacement.

[0007] This invention is achieved through the following technical solution:

[0008] This invention relates to a method for reinforcing the foundation of a brick-concrete structure without a ground beam using pit-type static pressure piles. The method comprises two main construction stages: the first stage involves strengthening the overall rigidity of the brick-concrete building by adding a new ground beam 1, shear keys 2, and through-wall reinforcement 4; the second stage involves the pit-type static pressure pile replacement and reinforcement construction, with the specific construction steps as follows:

[0009] Phase 1: Construction of stiffness reinforcement including the addition of 1 new ground beam, 2 shear keys, and 4 through-wall reinforcement bars.

[0010] Step 1: Construction of trench and wall opening

[0011] Based on the design drawings, the layout and positioning are carried out, and a new foundation trench for the ground beam is excavated on both sides of the existing load-bearing wall; the excavation depth of the foundation trench is equal to the bottom elevation of the new ground beam + 0.07m, and the excavation width is equal to the cross-sectional width of the new ground beam + 0.12m, with space reserved for brick formwork construction.

[0012] Shear key 2: A 350mm×350mm square hole is drilled in the wall corresponding to the shear key 2 using a water drill. The bottom elevation of the hole is flush with the bottom elevation of the newly added ground beams on both sides. The length, width and height of the hole exceed the outer dimensions of the shear key component by 50mm.

[0013] For the through-wall reinforcement 4, a 20mm diameter circular through hole is drilled with a water drill at the corresponding position in the wall. The through hole passes through the newly added ground beams on both sides of the wall.

[0014] Step 2: Base surface cleaning and treatment

[0015] After the foundation trench and wall openings are all formed, use a high-pressure water gun to wash away the floating dust and loose soil on the surface of the original masonry and foundation soil. After cleaning, let it stand to drain, ensuring that the newly added concrete components are tightly bonded to the original masonry structure.

[0016] Step 3: Foundation compaction and rebar tying

[0017] The soil at the bottom of the foundation trench was manually leveled and compacted in layers; the main reinforcement, stirrups, and shear key 2 stirrups of the newly added ground beam 1 were tied on site. The shear key stirrups were divided into first shear key stirrups 5 and second shear key 6; the through-wall reinforcement 4 passed through both sides of the newly added ground beam 1, and the reinforcement lap joints were staggered at the pile positions of the pit-type static pressure piles 3. The spacing of the stirrups of the newly added ground beam 1 and shear key 2 strictly matched the design parameters.

[0018] Step 4: Pouring and filling with concrete and grout.

[0019] After setting up the brick formwork, commercial concrete is poured to form the new ground beam 1 and shear key 2; the 20mm through hole through which the wall reinforcement 4 passes is filled with A50 grout to form the grout filling area 10; the gap between the new ground beam and the wall is filled with plain concrete to form the plain concrete filling area 11.

[0020] Concrete vibration is performed using a small immersion vibrator (φ30 small vibrator, vibrating in a quincunx pattern, 25 seconds per point, until the concrete surface is smooth and free of air bubbles, to prevent aggregate segregation). The vibration should be performed by quick insertion and slow withdrawal, with vibrating points evenly distributed in a quincunx pattern. The spacing between insertion points should be ≤ 1.5 times the effective radius of the vibrator. The vibration time per point should be 20–30 seconds, with the standard being a smooth surface free of air bubbles. Under-vibration and over-vibration should be strictly avoided to prevent segregation.

[0021] Step 5: Concrete Moisture Curing

[0022] Immediately after the concrete and grout have initially set and there is no free water on the surface, carry out moisturizing curing for 14 consecutive days. Increase the frequency of watering during high-temperature periods to prevent the surface from drying and cracking. In normal temperature environments, cover with geotextile and water within 3 to 6 hours after pouring. In hot and windy weather, cover with film in advance to keep moist and prevent plastic shrinkage cracks.

[0023] Only after all concrete and grout have cured to their designed strength can subsequent pit-type static pressure pile construction be carried out.

[0024] Phase Two: Pit-type Static Pressure Pile Replacement and Reinforcement Construction

[0025] Step 6: Complete Construction of Pit-Type Static Pressure Piles

[0026] (1) Surveying and setting out: Mark out the positions of all pit-type static pressure piles 3;

[0027] (2) Vertical working pit excavation and support: The excavation of the pile pit forms a guide pit 14, and the pit wall is simply supported;

[0028] (3) Positioning and straightening of precast pile 7: The segmented precast reinforced concrete static pressure pile 13 is hoisted into the pit and vertically adjusted;

[0029] (4) Staged static pressure pile driving: Hydraulic equipment is used to apply pressure in stages to drive the pile body;

[0030] (5) Welding of pile joint 12: Full welding connection at the pile joint;

[0031] (6) Pressure stabilization: After reaching the final design pressure, stabilize the pressure for 10 minutes and hold the load.

[0032] (7) Installation of pile top support: The pile top is covered with support steel plate 8, and the upper part is supported steel pipe 9. The support steel pipe 9 is pressed against the bottom surface of the newly added ground beam to realize the load support;

[0033] (8) Pile perimeter filling and consolidation: Concrete is poured to fill the gap between the pile body and the pilot pit 14;

[0034] (9) Backfilling of the pilot tunnel: C30 concrete was backfilled in layers in pilot tunnel 14 and compacted in layers;

[0035] Step 7: Final Acceptance Inspection

[0036] After all construction is completed, a special acceptance inspection will be carried out. The inspection content includes: final pile driving pressure, pile penetration depth, strength of precast pile test blocks, quality of pile splicing welding, pile top elevation, and pile position plane deviation. The project can be completed only after all indicators meet the design and specification requirements.

[0037] The present invention has the following advantages:

[0038] (1) By first constructing new ground beams with shear keys and through-wall reinforcement to strengthen the integrity of the building, and then driving piles after the reinforcement meets the standards, the pain point that traditional static pressure piles cannot be used in brick-concrete houses without ground ring beams is overcome.

[0039] (2) Shear keys and through-wall reinforcement form a force-transferring structure between the masonry and the newly added ground beam, which evenly distributes static pressure load and prevents stress concentration cracking of the wall during the construction stage.

[0040] (3) The whole process is suitable for various types of soft soil and low water level sites, with little construction disturbance and low cost, and simultaneously achieves multiple treatment effects such as reinforcement, correction and crack closure.

[0041] (4) Quantify construction parameters for the entire process, control the quality, and suppress uneven settlement and tilting of the building in the long term. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the foundation reinforcement plan layout;

[0043] Figure 2 This is the construction drawing for the newly added ground beam;

[0044] Figure 3 This is a diagram showing the construction of the newly added shear key;

[0045] Figure 4 This is a diagram showing the construction details of the newly added through-wall reinforcement.

[0046] Figure 5 Schematic diagram of pit-type static pressure pile construction method;

[0047] Attached diagram labels: 1-New ground beam, 2-Shear key, 3-Pit-type static pressure pile, 4-Through-wall reinforcement, 5-First shear key stirrup, 6-Second shear key stirrup, 7-Precast pile, 8-Underpinning steel plate, 9-Underpinning steel pipe, 10-Grouting filling area in the hole, 11-Plain concrete filling area, 12-Pile splice, 13-Reinforced concrete static pressure pile, 14-Pilot pit. Detailed Implementation

[0048] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are merely further illustrations of the present invention, but the scope of protection of the present invention is not limited to the following embodiments.

[0049] Example 1: Foundation reinforcement project for brick-concrete self-built houses without land beams in rural areas, see... Figures 1-5 As shown:

[0050] Project Overview: A three-story brick-concrete self-built residential house, constructed without professional design, lacking a ground beam, situated on collapsible loess soil, experiencing settlement and tilting on the south side of the house, with through cracks appearing in the longitudinal walls, and a groundwater level 6m deep. The construction method of this invention was used, completely covering all the components shown in the attached drawings. The construction process is as follows:

[0051] 1. Laying out lines, drilling holes, and excavation

[0052] Excavate the foundation trench for the new ground beam 1 along both sides of all load-bearing longitudinal and transverse walls of the building. The cross-sectional dimensions are 250mm×300mm. The excavation depth of the foundation trench is the design beam bottom elevation + 0.07m, and the excavation width is 250+120=370mm.

[0053] A shear key 2 is installed every 3m along the wall. A 350mm×350mm square hole is drilled with a water drill. The bottom elevation of the hole is flush with the bottom of the newly added ground beam 1. The length, width and height of the hole are each extended outward by 50mm.

[0054] Four through-wall steel bars are arranged in two rows on the same wall, and a water drill is used to drill through holes with a diameter of 20mm to create new ground beams on both sides of the wall.

[0055] 2. Base surface cleaning

[0056] High-pressure water guns were used to thoroughly rinse the foundation trench, the inner walls of the wall holes, and loose bricks. After cleaning, the surface was allowed to drain naturally for 2 hours.

[0057] 3. Foundation compaction and reinforcement binding

[0058] The soil at the bottom of the trench was leveled manually and compacted in 20cm layers; the main reinforcement and closed stirrups of the newly added ground beam 1 were tied on site; the first shear key stirrup 5 and the second shear key 6 were tied inside the shear key 2; the through-wall reinforcement 4 passed through the newly added ground beams on both sides, and all reinforcement lap joints avoided the pile positions of the pit-type static pressure pile 3, and there were no reinforcement lap joints at the pile positions.

[0059] 4. Pouring and grouting

[0060] The brick formwork was constructed, and C30 commercial concrete was poured to form the new ground beam 1 and shear key 2. A50 grout was injected into the 20mm through holes of the wall through-wall reinforcement 4 to form the grout filling area 10 in the hole. Plain concrete was used to fill the gap between the new ground beam 1 and the masonry wall to form the plain concrete filling area 11.

[0061] Use a φ30 small vibrator, vibrate in a quincunx pattern, and vibrate each point for 25 seconds until the concrete surface is smooth and free of air bubbles, thus preventing aggregate from settling and segregating.

[0062] 5. Concrete curing

[0063] Four hours after pouring, cover with geotextile and spray water to keep it moist and maintain its moisture. Continue this maintenance for 14 days. Increase the frequency of watering during periods of high temperature to prevent the surface from drying out and cracking.

[0064] 6. Construction of pit-type static pressure piles

[0065] (1) Measure and mark the positions of all pit-type static pressure piles;

[0066] (2) Excavate vertical guide pit 14, and lay wooden planks for simple support on the pit wall;

[0067] (3) The segmented precast pile 7 is hoisted into the pilot pit 14 and its verticality is adjusted;

[0068] (4) Hydraulic equipment for staged static pressure driving of reinforced concrete static pressure piles 13;

[0069] (5) Full welding of the pile joint 12 is carried out at the pile joint position;

[0070] (6) Pressurize to the design final pressure and stabilize for 10 minutes;

[0071] (7) Place the replacement steel plate 8 on the top of the pile, and erect the replacement steel pipe 9 on the top of the replacement steel plate 8. The top of the replacement steel pipe 9 is pressed against the bottom surface of the newly added ground beam 1 to complete the replacement of the upper wall load.

[0072] (8) The gap between the pile body and the pilot pit 14 was filled and consolidated with concrete;

[0073] (9) Backfill C30 concrete in layers in pilot tunnel 14 and compact each layer.

[0074] 7. Acceptance Inspection

[0075] The final pressure and penetration depth of each pile were tested, the strength of the precast pile 7 test blocks under the same conditions was tested, the appearance and flaw detection of the weld of the pile splice 12 were tested, and the pile top elevation and pile position deviation were tested. After all indicators met the specifications, the final acceptance was completed.

[0076] After completion, this embodiment was continuously monitored for 6 months. The settlement rate of the building was stable at ≤0.02mm / d, and the original cracks in the wall did not expand and were partially closed. In the case of the same type of building without ground beams that was directly constructed by static pressure without this method, the wall developed new through cracks of 0.2 to 0.5mm and the tilt continued to increase.

[0077] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for reinforcing pit-type static pressure pile foundations in brick-concrete structures without ground beams, characterized in that, It includes the stiffness reinforcement construction stage and the pit-type static pressure pile replacement construction stage; The stiffness reinforcement construction stage includes, in sequence, the steps of opening holes in the foundation trench and wall, cleaning the foundation surface, compacting the foundation and tying the reinforcing bars, pouring concrete grout, and curing concrete. The construction phase of the pit-type static pressure pile replacement includes the following steps in sequence: pile position layout, excavation and support of the working pit, positioning and straightening of precast piles, staged static pressure pile driving, pile splicing and welding, pressure stabilization and pressure adjustment, pile top replacement, pile perimeter filling, pilot pit backfilling, and final acceptance. The stiffness reinforcement construction stage includes the addition of ground beams (1), shear keys (2), and through-wall reinforcement (4), while the pit-type static pressure pile replacement construction stage includes the arrangement of pit-type static pressure piles (3). After all the procedures in the stiffness reinforcement construction stage are completed and the concrete reaches the design strength, the pit-type static pressure pile replacement construction stage begins.

2. The method for reinforcing pit-type static pressure pile foundations of brick-concrete structures without ground beams as described in claim 1, characterized in that, During the process of opening the trench and the wall, the trench for the new ground beam (1) is excavated on both sides of the original load-bearing wall. The trench excavation depth is the design bottom elevation of the new ground beam + 0.07m, and the excavation width is the cross-sectional width of the new ground beam (1) + 0.12m. The shear key (2) is drilled with a water drill to make a 350mm×350mm square hole in the wall. The bottom elevation of the hole is flush with the bottom of the new ground beam (1) on both sides. The through-wall reinforcement (4) is drilled with a through hole with a diameter of 20mm in the wall.

3. The method for reinforcing pit-type static pressure pile foundations of brick-concrete structures without ground beams as described in claim 1, characterized in that, During the process of tamping the foundation reinforcement, the first shear key stirrup (5) and the second shear key stirrup (6) are tied inside the shear key (2); the through wall reinforcement (4) is transversely connected to the newly added ground beam (1) on both sides, and the reinforcement lap joints are staggered with the pile positions of the pit-type static pressure pile (3).

4. The method for reinforcing pit-type static pressure pile foundations of brick-concrete structures without ground beams as described in claim 1, characterized in that, During the pouring of the concrete grout, the through hole of the wall through the wall reinforcement (4) is filled with A50 grout to form a grout filling area (10) in the hole; the gap between the newly added ground beam (1) and the original masonry wall is filled with plain concrete to form a plain concrete filling area (11); a small vibrator is used for plum blossom-shaped vibration, and the vibration time at a single point is 20-30s.

5. The method for reinforcing pit-type static pressure pile foundations of brick-concrete structures without ground beams as described in claim 1, characterized in that, During the concrete curing process, moisturizing curing shall be initiated within 3 to 6 hours after the concrete and grout have initially set and no free water remains. Apply a protective film in advance to prevent plastic cracks from forming under high temperature and strong wind conditions.

6. The method for reinforcing pit-type static pressure pile foundations of brick-concrete structures without ground beams as described in claim 1, characterized in that, The pit-type static pressure pile includes precast piles (7) and reinforced concrete static pressure piles (13); a joint (12) is provided at the pile section joint, and the joint (12) is fully welded.

7. The method for reinforcing pit-type static pressure pile foundations of brick-concrete structures without ground beams as described in claim 1, characterized in that, During the process of pile top replacement, a replacement steel plate (8) is laid on the top of the reinforced concrete static pressure pile (13), and a replacement steel pipe (9) is erected on the upper part of the replacement steel plate (8). The top of the replacement steel pipe (9) is pressed against the bottom surface of the newly added ground beam (1) to realize the wall load replacement.

8. The method for reinforcing pit-type static pressure pile foundations of brick-concrete structures without ground beams as described in claim 1, characterized in that, During the excavation and support of the working pit, a guide pit (14) is formed; C30 concrete is backfilled in layers in the guide pit (14) and compacted in layers.

9. The method for reinforcing pit-type static pressure pile foundations of brick-concrete structures without ground beams as described in claim 1, characterized in that, This method is applicable to old brick-concrete self-built houses and old masonry houses in old residential areas without ground beams or professional structural design. It is suitable for sites with foundations containing silt, silty soil, cohesive soil, silty loess, collapsible loess, artificial fill, and low groundwater levels.

10. The method for reinforcing pit-type static pressure pile foundations of brick-concrete structures without ground beams as described in claim 1, characterized in that, The inspection indicators during the completion and acceptance process include: final pressure and penetration depth of pit static pressure piles (3), strength of test blocks of precast piles (7), welding quality of splicing piles (12), pile top elevation, and pile position plane deviation. The project is completed after all inspection indicators meet the design and specification requirements.

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