Old house foundation steel pipe pile reinforcing construction method

Abstract

The invention provides an old house foundation steel pipe pile reinforcing construction method. The old house foundation steel pipe pile reinforcing construction method comprises the following steps that a steel pipe is cut in a segmented mode according to 2.8-3.0 m; the position of a pile center is measured and positioned, a small-sized water milling drilling machine is adopted for positioning and leveling, it is ensured that the perpendicularity deviation of a drilling rod is smaller than or equal to 2 cm, drilling is conducted to the designed rock entering depth, first-time hole cleaning is conducted after drilling, the sediment thickness meets the design requirement, and a pile hole is formed; a rock steel pipe and a common steel pipe are put in section by section through a drilling machine mooring rope, any two adjacent sections of steel pipes are connected through a lining pipe in a full-length welding mode, a section is put down until the pile bottom elevation is achieved, a steel pipe outer pile is formed, and the top section is kept to be reserved by 200 mm; detecting the sediment thickness after the steel pipe outer pile is formed, and replacing slurry and cleaning holes by adopting a guide pipe when the sediment thickness exceeds the standard; and a high-strength gravel concrete core is arranged in the steel pipe outer pile to form the steel pipe pile. The old house foundation steel pipe pile reinforcing construction method, the structure and the construction principle are simple, the feasibility is high, and the method can be suitable for old house foundation steel pipe pile reinforcing.

Description

Technical Field

[0001] The invention relates to the field of steel pipe pile reinforcement construction, in particular to a steel pipe pile reinforcement construction method for old building foundations. Background Art

[0002] Weathered and corroded foundations generally require reinforcement. Steel pipe piles offer the best overall cost-effectiveness based on design bearing capacity calculations. Conventional micro-steel pipe pile construction techniques are common, but limited interior floor heights make this approach difficult to apply and can hinder quality. Summary of the Invention

[0003] The main purpose of the present invention is to provide a steel pipe pile reinforcement construction method for old house foundations, so as to solve the technical problems of applicability difficulties and limited construction quality of the steel pipe pile reinforcement construction method for old house foundations in actual construction process.

[0004] To achieve the above object, the present invention provides a method for reinforcing the foundation of an old building with steel pipe piles, comprising the following steps:

[0005] The steel pipe is cut into sections of 2.8 to 3.0 m. Shear ring reinforcement is welded to the rock-entering section and a first slurry outlet with a plum blossom shape distribution is opened. A staggered second slurry outlet is opened for the ordinary section and anchor steel bars are pre-welded to the top section of the steel pipe.

[0006] Measure and locate the pile center position, use a small water-grinding drill to position and level it, ensure the vertical deviation of the drill rod is ≤2cm, drill to the designed rock penetration depth, perform the first hole cleaning after drilling, and ensure the sediment thickness meets the design requirements to form a pile hole.

[0007] Use the drilling rig cable to lower the rock steel pipe and ordinary steel pipe section by section. Any two adjacent sections of steel pipe are fully welded together through the inner liner pipe. After the weld is cooled and tested to be qualified, lower the next section until the pile bottom elevation is reached to form a steel pipe outer pile and keep 200mm reserved at the top section.

[0008] After the steel pipe outer pile is formed, the sediment thickness is checked. If it exceeds the standard, the slurry is replaced by the guide tube to clean the hole.

[0009] A high-strength crushed stone concrete core is arranged in the steel pipe outer pile to form the steel pipe pile.

[0010] According to an embodiment of the present application, the diameter of the first slurry outlet is 30-40 mm, and the spacing is 300-500 mm.

[0011] The second slurry outlets of the ordinary section steel pipe are staggered in two rows every 600 mm, and the diameter of the second slurry outlet is 20 mm.

[0012] According to the implementation mode of the present application, the specification spacing of the shear ring reinforcement is C12@150mm, and the shear ring reinforcement is firmly welded to the rock-entering section steel pipe on both sides.

[0013] According to the implementation method of the present application, the hole is opened by rotating clockwise in situ during drilling, the initial drilling pressure is controlled at 90Kpa, and mud is continuously replenished at any time during the drilling process to ensure that the water head height in the hole is always maintained at 1 to 1.5 meters above the groundwater level.

[0014] According to the implementation manner of the present application, the height of the inner lining steel pipe is not less than twice the diameter of the steel pipe, and the wall thickness of the inner lining steel pipe is not less than the wall thickness of the steel pipe pile.

[0015] During the welding process, open a 45° groove for welding, fully weld the outer edge of the joint, hf≧1.5t, the weld width is between 2 and 4mm, the weld should be full, and check the verticality of the steel pipe after completion.

[0016] According to an embodiment of the present application, a high-strength crushed stone concrete core is provided in the steel pipe outer pile, and the steps of forming the steel pipe pile include:

[0017] The grouting steel pipe is inserted into the outer pile of the steel pipe and continuously grouting is performed into the pile hole to form the grouting in one step until the cement slurry flows out of the pipe. The grouting material uses cement grade 42.5R, the water-cement ratio is controlled to be no more than 0.45, and the grouting pressure is 0.5 MPa.

[0018] Add coarse aggregate with a particle size of 20-30mm into the outer pile of the steel pipe, vibrate it to make it dense and slowly pull out the grouting pipe.

[0019] According to the implementation of the present application, the filling of coarse aggregate and the pulling out of the grouting pipe are carried out simultaneously, and the crushed stone and the cement slurry are ensured to be tightly combined by plugging or vibrating.

[0020] According to the implementation manner of the present application, the integrity of the steel pipe pile is tested by a low-strain method, and the bearing capacity of a single pile is tested by a self-balancing method using a pre-installed load box on the pile body.

[0021] According to the implementation mode of the present application, it also includes:

[0022] A cap is arranged on the steel pipe pile, and the cap steel bars of the cap are welded to the anchor steel bars.

[0023] According to the implementation manner of the present application, the welding length between the base steel bar and the anchor steel bar is ≧35d, and the welding length between the anchor steel bar and the inner wall of the top section steel pipe is 10d.

[0024] In the aforementioned steel pipe pile reinforcement construction method for old building foundations, the steel pipe piles are segmented and a small water-drilling rig is used to accommodate low-clearance construction within the building. Pre-welding the top anchor reinforcement reduces the need for later vertical welding, resulting in higher welding quality and reducing the impact of low clearance. Shear ring reinforcement is also used to enhance the shear strength of the rock-entering portion. This method for reinforcing old building foundations with steel pipe piles solves applicability issues and improves construction quality. Its structure and construction principles are simple, highly feasible, and suitable for reinforcing old building foundations with steel pipe piles. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0026] Figure 1 It is a structural schematic diagram of steel pipe piles obtained by the steel pipe pile reinforcement construction method for old building foundations according to one embodiment of the present application.

[0027] Figure 2 yes Figure 1 Schematic diagram of the AA cross-section.

[0028] Figure 3 yes Figure 1 Schematic cross-sectional view along the BB direction.

[0029] Figure 4 It is a cross-sectional diagram of steel pipe welding.

[0030] 100, rock entry section steel pipe; 110, first grouting outlet; 120, shear ring reinforcement; 200, ordinary section steel pipe; 210, top section steel pipe; 220, anchoring steel bar; 300, inner lining pipe; 230, second grouting outlet; 400, pedestal; 500, pile hole; 600, high-strength crushed stone concrete core; 10, upper section steel pipe; 20, lower section steel pipe; 30, rock entry surface.

[0031] The realization of the objectives, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0032] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] It should be noted that all directional indications (such as up, down, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0034] In addition, the terms "first," "second," and so on, used in this disclosure are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, features specified as "first" or "second" may explicitly or implicitly include at least one of these features.

[0035] Moreover, the technical solutions between the various embodiments of the present invention may be combined with each other, but this must be based on the fact that ordinary technicians in this field can implement them. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0036] The present invention provides a method for reinforcing the foundation of an old house with steel pipe piles. Figures 1 to 4 , including the following steps:

[0037] S1: Cut the steel pipe into sections of 2.8 to 3.0 m, weld shear ring reinforcement 120 to the rock-entering section steel pipe 100 and open a first slurry outlet 110 with a plum blossom shape distribution, open a staggered second slurry outlet 230 for the ordinary section steel pipe 200 and pre-weld anchor steel bars 220 to the top section steel pipe 210.

[0038] Before this step, the steel pipes can also be inspected. For example, the ends of the steel pipes must be cleaned of loose rust, oil stains, and other impurities to keep them dry. The pipe bodies must also be inspected for cracks or damage. If any damage is found, pile foundation construction must not be carried out until it has been properly treated.

[0039] In step S1, due to the limited space for indoor steel pipe pile construction, the steel pipes are divided into sections (3m) of 2.8 to 3.0m to facilitate subsequent construction. Generally, φ245 steel pipes with a wall thickness of 10mm can be used.

[0040] The rock-entering section steel pipe 100 is the bottom section steel pipe, located below the rock-entering surface 30. The other steel pipes are non-rock-entering steel pipes, i.e., ordinary section steel pipes 200. The top section steel pipe 210 is the topmost steel pipe among the ordinary steel pipes.

[0041] Based on the required rock penetration depth, shear reinforcement 120 is welded to the steel pipe within the rock penetration section. In some embodiments, the shear reinforcement 120 is spaced at a standard spacing of C12@150mm. Shear reinforcement 120 is securely welded to the rock penetration section steel pipe 100 on both sides, thereby increasing the load-bearing capacity, such as significantly enhancing the load-bearing capacity of the pile-rock interface and the pile end resistance (end bearing force).

[0042] The first slurry outlets 110 are arranged in a plum blossom pattern. The rock entry steel pipe 100 has plum blossom-shaped slurry outlets on the pile shaft. A plum blossom-shaped slurry outlet refers to slurry outlets arranged in a pattern similar to plum blossom petals. These outlets are typically staggered at certain angles and intervals, forming a layout similar to plum blossom petals. The outlets are staggered on the outer wall of the steel pipe, with the upper and lower layers of outlets positioned at different positions. After the holes are opened, they are temporarily sealed with tape.

[0043] Fabrication of the top steel pipe 210: Because later vertical welding is difficult, the top anchor rebar 220 is fabricated and welded first. The anchor length to the newly constructed cap rebar is ≥35d, and the weld length to the inner wall of the steel pipe is 10d. Pre-fabrication of the top anchor rebar 220 at the fabrication plant reduces later vertical welding and improves weld quality.

[0044] In some embodiments, reference Figure 1 The first grouting ports 110 have a diameter of 30-40 mm and a spacing of 300-500 mm. The large-aperture plum blossom-shaped arrangement ensures that during high-pressure grouting in the rock entry section, the cement slurry can fully and evenly penetrate radially, wrapping around the pile body and penetrating into the surrounding rock fissures, creating an "enlarged head" effect, greatly improving the pile's side friction and end bearing capacity.

[0045] In some embodiments, reference Figure 1 The ordinary section steel pipe 200 has two rows of second slurry outlets 230 staggered every 600 mm, and the diameter of the second slurry outlet 230 is 20 mm.

[0046] This design provides a channel for the grout to seep out of the normal soil section of the pile body, forming a uniform cement-stone mass and increasing the friction resistance around the pile. After the hole is opened, it is temporarily sealed with tape.

[0047] S2: Measure and locate the pile center position, use a small water-grinding drill to position and level it, ensure that the vertical deviation of the drill rod is ≤2cm, drill to the designed rock penetration depth, clean the hole for the first time after drilling, and ensure that the sediment thickness meets the design requirements to form a pile hole.

[0048] Before this step, the site must be leveled and cleaned before the steel pipe pile is constructed, the positioning and layout must be measured, the pile center position must be marked, the pile diameter and position must be marked with a lime circle, and then the drilling rig must be put into place.

[0049] Due to the low indoor floor height, a small water-grinding drilling rig is used. The drilling rig is placed in the designated position, leveled and centered to ensure that the drilling rig body is horizontal and the drill rod (wire rope) is vertical. The drill rod position deviation shall not exceed 2cm.

[0050] In some embodiments, the hole is opened by rotating clockwise in situ during drilling, the initial drilling pressure is controlled at 90 KPa, and mud is continuously replenished during the drilling process to ensure that the water head height in the hole is always maintained at 1 to 1.5 meters above the groundwater level.

[0051] During drilling, the drill is opened by rotating the hole clockwise in place. The weight of the drill bucket and the drill pipe plus the hydraulic pressure is used as the drilling pressure. The initial drilling pressure is controlled at around 90 kPa, and the drilling speed is slow at first and then fast. Mud should be continuously replenished during the drilling process to ensure that the water head height in the hole is always 1 to 1.5 meters above the groundwater level.

[0052] When drilling to the design elevation, use a cylindrical drill with a valve to clean out the sediment. If the mud skin on the hole wall is thick, use a sweeping drill bit to sweep the hole wall back and forth. The sediment thickness must not exceed the design and specification requirements. After the initial hole cleaning is completed, the process acceptance is carried out. This is the basis for ensuring pile end resistance and the subsequent smooth lowering of the steel pipe and grouting.

[0053] S3: Use the drilling rig cable to lower the rock steel pipe and ordinary steel pipe section by section. Any two adjacent sections of steel pipe are connected by 300mm full welding of the inner liner pipe. After the weld is cooled and tested to be qualified, lower one section until the pile bottom elevation is reached to form a steel pipe outer pile and keep 200mm reserved at the top section.

[0054] The welding method of the upper steel pipe 10 and the lower steel pipe is as follows: Figure 4 For example, manually secure the first section of steel pipe to the cable atop the water-mill drill rig. Smoothly lower the bottom section into the borehole, leaving 200mm of steel pipe exposed above the ground. After clamping it on the drill rig, secure the second section of steel pipe to the cable. Next, fasten the liner 300mm between the first and second sections, fully welding them in place. Allow the weld to cool for approximately 3 minutes and pass inspection before removing the temporary fixtures on the first section of steel pipe. Install the second section below, and so on, until the pile base is reached. The final section of steel pipe should be installed 200mm above the ground, with the excess removed from the bottom of the section.

[0055] This step has the following three functions:

[0056] First, the segmented lowering and full welding of the lining: this is the core process, which adapts to low space and ensures the connection strength, rigidity and integrity of the segmented steel pipes through 300% full welding of the lining pipe to form a continuous pile.

[0057] Secondly, process control: strictly cool down and test before lowering a section to prevent thermal deformation from affecting verticality; controlling verticality is the key to ensuring bearing capacity.

[0058] Then, reserve height to facilitate subsequent operations (connecting grouting pipes, testing, etc.) and pile head processing.

[0059] In some embodiments, reference Figure 4 The height of the inner lining steel pipe is not less than twice the diameter of the steel pipe, and the wall thickness of the inner lining steel pipe is not less than the wall thickness of the steel pipe pile.

[0060] During the welding process, open a 45° groove for welding, fully weld the outer edge of the joint, hf≧1.5t, and the weld width is between 2 and 4mm. The weld should be full, and the verticality of the steel pipe should be checked after completion. A trial weld should be made before welding, such as taking 10mm and opening a 45° groove for welding.

[0061] S4: After forming the steel pipe outer pile, check the sediment thickness. If it exceeds the standard, use the guide tube to replace the slurry and clean the hole.

[0062] After the steel pipe is installed, check the thickness of the sediment at the bottom of the hole. If the sediment thickness exceeds the design or specification requirements, use the catheter to change the slurry and clean the hole again.

[0063] S5: A high-strength crushed stone concrete core 600 is arranged in the steel pipe outer pile to form the steel pipe pile.

[0064] This operation forms a pile within a pile, which is equivalent to forming a small-diameter crushed stone concrete pile core inside the steel pipe, significantly improving the stiffness and bearing capacity of the single pile.

[0065] In the aforementioned steel pipe pile reinforcement method for old building foundations, the piles are segmented and drilled using a small water-jet drill rig, making them suitable for low-clearance construction within buildings. Pre-welding the top anchor bars (220 mm) reduces the need for later vertical welding, resulting in higher weld quality and minimizing the impact of low clearance. Shear ring reinforcement (120 mm) is also used to enhance the shear strength of the rock-entry portion. This method addresses applicability issues and improves construction quality. Its simple structure and construction principles offer strong feasibility, making it suitable for steel pipe pile reinforcement of old building foundations.

[0066] In some embodiments, a high-strength crushed stone concrete core 600 is provided in the steel pipe outer pile. The steps of forming the steel pipe pile include:

[0067] S51: Continuously grouting is performed into the pile hole through a grouting steel pipe inserted into the outer pile of the steel pipe, forming the grouting in one step until the cement slurry flows out of the pipe. The grouting material uses cement grade 42.5R, the water-cement ratio is controlled to be no more than 0.45, and the grouting pressure is 0.5 MPa.

[0068] In this step, the grouting pipe is installed, conveyed via a rubber hose. The steel pipe is inserted into the outer pile of the steel pipe and grouting is injected into the pile hole. The grouting material is 42.5R cement, mixed using a dedicated machine, with a water-cement ratio of no more than 0.45. The grouting pipe must be equipped with a pressure gauge, and the grouting pressure is approximately 0.5 MPa. After grouting, the pipe is not removed, and the process continues until the grouting flows out of the pipe.

[0069] S52: Add coarse aggregate with a particle size of 20-30mm into the outer pile of the steel pipe, vibrate it to make it dense and slowly pull out the grouting pipe.

[0070] In this step, the coarse aggregate should be crushed stone with a particle size of 20mm to 30mm. The coarse aggregate should be slowly lowered from the steel pipe hole. At the same time, the coarse aggregate should be vibrated and filled densely in the steel pipe by using a grouting steel pipe or other effective methods. The grouting pipe should be slowly pulled out at the same time. At this time, the steel pipe pile reinforcement construction is completed.

[0071] In some embodiments, the filling of coarse aggregate and the pulling out of the grouting pipe are carried out simultaneously, and the crushed stone and the cement slurry are ensured to be tightly combined by plugging or vibrating.

[0072] In some embodiments, the integrity of the steel pipe pile is tested using a low-strain method, and the bearing capacity of a single pile is tested using a self-balancing method by pre-installing a load box on the pile body.

[0073] The integrity of the pile body adopts low strain, which is affected by the indoor clearance of old houses. The vertical compressive bearing capacity of a single pile is difficult to test using conventional loading method or high strain. Therefore, before construction, the test pile position is confirmed in advance with the designer and the owner, and the load box is welded and installed on the steel pipe pile. The bearing capacity is obtained using the self-balancing method to ensure compliance.

[0074] In some embodiments, after welding is completed at each welding location, the welding slag needs to be cleaned and anti-corrosion paint needs to be applied.

[0075] In some embodiments, further comprising:

[0076] A cap 400 is provided on the steel pipe pile, and the cap steel bars of the cap 400 are welded to the anchor steel bars 220 .

[0077] In some embodiments, the welding length between the cap steel bar and the anchor steel bar 220 is ≥35d, and the welding length between the anchor steel bar 220 and the inner wall of the top steel pipe 210 is 10d.

[0078] (1) The technical solution of the present application is described below using a more detailed embodiment as an example.

[0079] (2) Main construction steps of a steel pipe pile reinforcement construction method for old building foundations:

[0080] (3) Steel pipe inspection: Check the rust, oil and other dirt on the pile end, which must be removed and kept dry; check whether there are cracks or damages on the steel pipe pile body. If there are any damages, pile foundation construction shall not be carried out before reasonable treatment.

[0081] (4) Steel pipe segmentation: Steel pipe piles are operated indoors and the space is limited. The steel pipes are segmented into 3m sections to facilitate subsequent construction. Generally, φ245 steel pipes with a wall thickness of 10mm can be used.

[0082] (5) Processing and installation of lining connecting steel pipes: The height of the lining steel pipe shall not be less than twice the diameter of the steel pipe, and the wall thickness of the lining steel pipe shall not be less than the wall thickness of the steel pipe pile, which is 10 mm. A trial weld shall be conducted before welding, and a 45° groove shall be opened for welding. The outer edge of the joint shall be fully welded, with hf≧1.5t and a width between 2 and 4 mm. The weld shall be full, and the verticality of the steel pipe shall be checked after completion.

[0083] (6) Bottom section steel pipe processing: According to the design rock penetration depth requirements, shear ring reinforcement is welded to the steel pipe within the rock penetration section, with a spacing of C12 @ 150mm. The shear ring reinforcement is welded firmly to the steel pipe on both sides to increase the bearing capacity. A plum blossom-shaped grouting outlet is opened on the pile body, with a diameter of 30-40mm and a spacing of 300-500mm. In the ordinary section, the second grouting outlet is arranged in two rows every 600mm, with a diameter of 20mm. After the hole is opened, it is sealed with tape.

[0084] (7) Processing of top steel pipe: As vertical welding is not easy to perform in the later stage, the top anchor steel bars are processed and welded first. The anchor length with the newly built foundation steel bar is ≥35d, and the welding length with the inner wall of the steel pipe is 10d.

[0085] (8) Welding area treatment: After welding, the welding slag must be cleaned and anti-corrosion paint must be applied.

[0086] (9) Positioning and laying out: Before the construction of steel pipe piles, the site must be leveled and cleaned, the positioning and laying out must be done, and the position of the pile center must be marked. The pile diameter and position must be marked with a lime circle.

[0087] (10) Drilling rig placement: The indoor floor height is relatively low, so a small water-grinding drilling rig is used. The drilling rig is placed in the designated location, leveled and centered to ensure that the drilling rig body is horizontal and the drill rod (wire rope) is vertical. The drill rod position deviation shall not exceed 2 cm.

[0088] (11) Drilling: Drill the hole in a clockwise direction. The weight of the drill bucket and the drill rod plus the hydraulic pressure is used as the drilling pressure. The initial drilling pressure is controlled at around 90 kPa. The drilling speed is slow at first and then fast. Mud should be continuously replenished during the drilling process to ensure that the water head in the hole is always 1 to 1.5 meters above the groundwater level.

[0089] (12) Hole cleaning: When drilling to the design elevation, use a cylindrical drill with a valve to clean the sediment. When the mud skin on the hole wall is thick, use a hole sweeping drill to move up and down to sweep the hole wall. The sediment thickness should not exceed the design and specification requirements. After the first hole cleaning is completed, the process acceptance is carried out.

[0090] (13) Lowering the pipe: Manually fix the first section of steel pipe to the cable on the top of the water-mill drilling rig, and steadily lower the bottom section of steel pipe into the borehole, with the steel pipe exposed 200mm above the ground. After clamping it on the drilling rig, fix the second section of steel pipe to the cable. Then, fasten the inner lining pipe between the first and second sections of steel pipe and fully weld it. After the weld cools for about 3 minutes and passes the inspection, remove the temporary fixation of the first section of steel pipe, and then lower the second section of steel pipe. Repeat this process until the pile bottom elevation is reached. The last section of steel pipe must be exposed 200mm above the ground, and the excess part is cut off from the bottom of the section.

[0091] (14) Secondary hole cleaning: After the steel pipe is installed, check the thickness of the sediment at the bottom of the hole. If the sediment thickness exceeds the design or specification requirements, use the catheter to change the slurry and clean the hole again.

[0092] (15) Grouting: Install the grouting pipe, which is transported by a rubber tube. The grouting steel pipe is inserted into the pile hole for grouting. The grouting material is cement grade 42.5R. The cement slurry is mixed using a special machine, and the water-cement ratio is controlled to be no greater than 0.45. The grouting pipe must be equipped with a pressure gauge. The grouting pressure is approximately 0.5 MPa. After grouting, the pipe is not removed temporarily. The construction is continued and the grouting is formed in one step until the cement slurry flows out of the pipe.

[0093] (16) Lowering coarse aggregate: The coarse aggregate should be crushed stone with a particle size of 20mm to 30mm. Slowly lower the coarse aggregate from the steel pipe hole. At the same time, use the grouting steel pipe to insert it or use other effective methods to vibrate the coarse aggregate in the steel pipe to fill it tightly. At the same time, slowly pull out the grouting pipe. At this time, the steel pipe pile reinforcement construction is completed.

[0094] (17) Steel pipe pile inspection: The integrity of the pile body is tested using low strain. Due to the influence of the indoor clearance of old houses, the vertical compressive bearing capacity of a single pile is difficult to be tested using conventional loading method or high strain. Therefore, before construction, the inspection pile position is confirmed in advance with the designer and the owner. The load box is welded and installed on the steel pipe pile, and the bearing capacity is obtained using the self-balancing method to ensure compliance.

[0095] This invention effectively solves the problem of applicability of ordinary steel pipe pile reinforcement for old buildings, improves construction quality and reduces project costs. The main advantages of this method are:

[0096] (1) The structure and construction principle are simple and feasible;

[0097] (2) Steel pipe piles are divided into sections and a small water-grinding drill is used to adapt to low net height construction in houses;

[0098] (3) Welding the top anchor steel bars in advance and making them in the processing plant can reduce the need for vertical welding in the later stage and improve the welding quality;

[0099] (4) The use of spiral stirrups enhances the shear strength of the rock penetration part;

[0100] (5) Control the grouting pressure to achieve good grouting reinforcement effect;

[0101] (6) The steel pipe pile adopts the self-balancing method and pre-buried load box to ensure that the vertical bearing capacity of the single pile meets the requirements;

[0102] (7) It can be widely used in the reinforcement of indoor foundations of old buildings and has promotion value. (8)

[0104] The above technical solutions of the present invention are only preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made by using the contents of the present invention's description and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for reinforcing the foundation of an old house with steel pipe piles, characterized in that: The following steps are involved: Cut the steel pipe into sections of 2.8 to 3.0 m, weld shear ring reinforcement to the rock section and open the first grouting outlet in a plum blossom pattern, open the second staggered grouting outlet for the ordinary section and pre-weld anchor steel bars to the top section; Measure and locate the pile core position, use a small water-grinding drill to position and level it, ensure the vertical deviation of the drill rod is ≤2cm, drill to the designed rock penetration depth, perform the first hole cleaning after drilling, and ensure the sediment thickness meets the design requirements to form the pile hole; Use the drilling rig cable to lower the rock steel pipe and ordinary steel pipe section by section. Any two adjacent sections of steel pipe are fully welded together through the inner liner pipe. After the weld cooling test is qualified, lower the next section until the pile bottom elevation is reached to form the steel pipe outer pile and keep 200mm reserved at the top section; After forming the steel pipe outer pile, the sediment thickness is tested. If it exceeds the standard, the pipe is used to replace the slurry and clean the hole; A high-strength crushed stone concrete core is arranged in the steel pipe outer pile to form the steel pipe pile.

2. The method for reinforcing the old building foundation with steel pipe piles according to claim 1, characterized in that: The diameter of the first slurry outlet is 30-40 mm, and the spacing is 300-500 mm; The second slurry outlets of the ordinary section steel pipe are staggered in two rows every 600 mm, and the diameter of the second slurry outlet is 20 mm.

3. The steel pipe pile reinforcement construction method for old building foundation according to claim 2 is characterized in that: The specification spacing of the shear ring reinforcement is C12@150mm, and the shear ring reinforcement is firmly welded to the rock-entering section steel pipe on both sides.

4. The method for reinforcing the old building foundation with steel pipe piles according to claim 1, characterized in that: When drilling, rotate clockwise in place to open the hole. The initial drilling pressure is controlled at 90Kpa, and mud must be continuously replenished during the drilling process to ensure that the water head height in the hole is always maintained at 1 to 1.5 meters above the groundwater level.

5. The method for reinforcing the old building foundation with steel pipe piles according to claim 2, characterized in that: The height of the inner lining steel pipe is not less than twice the diameter of the steel pipe, and the wall thickness of the inner lining steel pipe is not less than the wall thickness of the steel pipe pile; During the welding process, open a 45° groove for welding, fully weld the outer edge of the joint, hf≧1.5t, the weld width is between 2 and 4mm, the weld should be full, and check the verticality of the steel pipe after completion.

6. The steel pipe pile reinforcement construction method for old building foundation according to claim 5 is characterized in that: A high-strength crushed stone concrete core is provided in the steel pipe outer pile. The steps of forming the steel pipe pile include: Through the grouting steel pipe inserted into the steel pipe outer pile to continuously grouting into the pile hole, forming it in one step until the cement slurry flows out of the pipe, wherein the grouting material uses cement grade 42.5R, the water-cement ratio is controlled to be no more than 0.45, and the grouting pressure is 0.5Mpa; Add coarse aggregate with a particle size of 20-30mm into the outer pile of the steel pipe, vibrate it to make it dense and slowly pull out the grouting pipe.

7. The method for reinforcing the old building foundation with steel pipe piles according to claim 6, characterized in that: The filling of coarse aggregate and the pulling out of the grouting pipe are carried out simultaneously, and the crushed stone and cement slurry are ensured to be tightly combined by plugging or vibrating.

8. The method for reinforcing old building foundation steel pipe piles according to claim 1, characterized in that: The integrity of the steel pipe pile is tested by a low strain method, and the bearing capacity of a single pile is tested by a self-balancing method using a load box pre-installed on the pile body.

9. The steel pipe pile reinforcement construction method for old building foundation according to any one of claims 1 to 8, characterized in that: Also includes: A cap is arranged on the steel pipe pile, and the cap steel bars of the cap are welded to the anchor steel bars.

10. The method for reinforcing old building foundation steel pipe piles according to claim 9, characterized in that: The welding length between the base steel bar and the anchor steel bar is ≥35d, and the welding length between the anchor steel bar and the inner wall of the top section steel pipe is 10d.

Images