CN111236280A - Prefabricated square pile for deep foundation pit and side slope support and pile splicing method thereof - Google Patents
Prefabricated square pile for deep foundation pit and side slope support and pile splicing method thereof Download PDFInfo
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D17/00—Excavations; Bordering of excavations; Making embankments
- E02D17/20—Securing of slopes or inclines
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D17/00—Excavations; Bordering of excavations; Making embankments
- E02D17/02—Foundation pits
- E02D17/04—Bordering surfacing or stiffening the sides of foundation pits
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D17/00—Excavations; Bordering of excavations; Making embankments
- E02D17/20—Securing of slopes or inclines
- E02D17/207—Securing of slopes or inclines with means incorporating sheet piles or piles
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
- E02D5/22—Piles
- E02D5/24—Prefabricated piles
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
- E02D5/22—Piles
- E02D5/52—Piles composed of separable parts, e.g. telescopic tubes ; Piles composed of segments
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
- E02D5/22—Piles
- E02D5/52—Piles composed of separable parts, e.g. telescopic tubes ; Piles composed of segments
- E02D5/523—Piles composed of separable parts, e.g. telescopic tubes ; Piles composed of segments composed of segments
- E02D5/526—Connection means between pile segments
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- Civil Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Piles And Underground Anchors (AREA)
Abstract
The invention discloses a prefabricated square pile for supporting a deep foundation pit and a side slope and a pile splicing method thereof. The anchor cable holes are threaded holes, the inner diameter of each anchor cable hole is 180mm, and the distance between every two adjacent anchor cable holes is 2000-4000 mm. The cross section of the prefabricated square pile is square, the two ends of the prefabricated square pile are respectively provided with a hoop joint with a certain length, the end faces of the two ends of the prefabricated square pile are provided with a butt joint end steel plate and a butt joint hoop plate matched with the butt joint end steel plate and the hoop joint, and the butt joint hoop plate is coated and tightly attached to the hoop joint and the butt joint end steel plate. The cross sections of the shroud ring joint and the butt joint end steel plate are square, the butt joint end steel plate is provided with an end plate hole, and the butt joint hoop plate is formed by fixedly butting two L-shaped steel plates with the same specification. Meets the strength requirement, has low cost, safety and environmental protection.
Description
Technical Field
The invention belongs to the technical field of building engineering, and relates to a prefabricated square pile for deep foundation pit and side slope support and a pile splicing method thereof.
Background
With the rapid development of urban construction, due to the limitation of the development of upper space, the development of underground complex and large-area urban underground space in large scale has become the mainstream. Therefore, the foundation burial depth of the building engineering begins to increase continuously, the height of the side slope is increased, and the foundation pit support and the side slope support become important geotechnical engineering problems.
The problem is generally solved by adopting a cast-in-place pile, but the cast-in-place pile has long construction period, no quality guarantee, resource waste, environmental pollution and high cost. The precast pile has five advantages and is widely applied. Firstly, the advantages in the construction period are that the precast pile adopts static pressure pile sinking, so that the method has the advantages of no noise, no vibration and no impact, can realize 24-hour operation, increase the construction time and shorten the construction period, and has the advantages of less pile forming procedures, simple operation and no need of maintaining the concrete of the pile body. Secondly, the advantages of the construction quality of the pile body are that the precast pile is precast and formed in a factory in advance, and the strength of the pile body is high and can reach C80. The pile body forming process is strong in monitorability, and forming quality and strength quality are guaranteed. Thirdly, the precast pile presses the pile body to the top depth, so that the problems of over-filling, manual pile head breaking, crane transferring and transporting of the pile head and the like caused by the cast-in-place pile do not exist, and resources are saved. Fourthly, the precast pile construction process has no wet operation, no hole-forming wall protection process, no environment pollution phenomena such as construction site dust, road spreading, construction noise and the like. Fifthly, the precast pile is arranged under the wall, a strip foundation is adopted, the pile number can be greatly reduced, the precast pile is basically a strip foundation, the precast pile is comprehensively considered from the pile number, the pile length, the foundation form, the pile inspection cost and the like, and the cost is lower.
At present, the existing technical regulations and drawing sets make requirements on the manufacture and use of precast piles, and meanwhile, in order to meet deeper supporting requirements, pile splicing processes are also developed endlessly. However, the following defects are also commonly existed in the prior art:
1. with the deeper and deeper excavation depth of the foundation pit, the length of a single precast pile cannot meet the requirement of the design depth of the foundation pit.
2. At present, a section steel waist beam commonly adopted in support engineering is used as a force transmission component of a prestressed anchor cable and a pile, and due to the limited interface and rigidity of the section steel waist beam, the overall stress of the anchor cable and a pile arrangement system is often reduced, and the stability and deformation control of a foundation pit are extremely unfavorable.
3. The existing pile splicing process comprises an end plate welding method and a mechanical connection method, but the joint strength is too low to meet the design requirement, and the end plate welding method is not environment-friendly due to welding waste gas.
Disclosure of Invention
The embodiment of the invention aims to provide a prefabricated square pile for supporting a deep foundation pit and a side slope, and aims to solve the problems that the integral stress of an anchor cable and a pile arrangement system is reduced and the stability and deformation control of the foundation pit are extremely unfavorable by using a profile steel waist beam as a force transmission component of a prestressed anchor cable and a pile at present.
Another object of the embodiments of the present invention is to provide a pile extension method for a prefabricated square pile for deep foundation pit and slope support, which is fast in construction, meets the requirement of joint strength, is low in cost, safe and environment-friendly, and solves the problems that the length of a single prefabricated pile cannot meet the requirement of the design depth of a foundation pit at present, and the existing pile extension method is low in joint strength and not environment-friendly.
In order to solve the technical problem, the technical scheme adopted by the invention is that the prefabricated square pile for supporting the deep foundation pit and the side slope comprises a solid prefabricated square pile, a plurality of anchor cable holes perpendicular to the pile body of the prefabricated square pile are formed in the length direction of the prefabricated square pile, the anchor cable holes are all located on the central line of the prefabricated square pile, and the anchor cable holes are not interfered with main ribs and winding ribs of the prefabricated square pile.
Furthermore, the anchor cable holes are threaded holes, the inner diameter of each anchor cable hole is 180mm, and the distance between every two adjacent anchor cable holes is 2000-4000 mm.
Furthermore, the cross section of the prefabricated square pile is square with the side length of Hmm, wrapping hoop joints with certain lengths are reserved at two ends of the prefabricated square pile, butt joint end steel plates and butt joint hoop plates matched with the butt joint end steel plates and the wrapping hoop joints are arranged at end faces of two ends of the prefabricated square pile, and the butt joint hoop plates are wrapped and tightly attached to the wrapping hoop joints and the butt joint end steel plates.
Further, the cross sections of the shroud ring joint and the butt end steel plate are square with the size of (H-20) mm multiplied by (H-20) mm;
the length of the butt joint hoop plate is 2 times of the sum of the thickness of the butt joint end steel plate and the length of the hoop-covered joint, the inner size of the cross section of the butt joint hoop plate is equal to the size of the cross section of the hoop-covered joint end steel plate, and the outer size of the cross section of the butt joint hoop plate is equal to the size of the cross section of the prefabricated square pile.
Furthermore, the butt joint end steel plate is provided with an end plate hole, and the thickness of the butt joint end steel plate is 20 mm.
Furthermore, the butt hoop plate is formed by butt-jointing and fixing two L-shaped steel plates with the same specification, and the thickness of the butt hoop plate is 8 mm.
Furthermore, the cross section of the prefabricated square pile is square, the main reinforcements are respectively distributed at four corners of the prefabricated square pile in an L shape, the winding reinforcements are symmetrically arranged by taking the center of the prefabricated square pile as the center, the arrangement interval of the winding reinforcements at the 13000mm length part in the middle of the prefabricated square pile is 80mm, and the arrangement interval of the winding reinforcements at the 1000mm length parts at two ends of the prefabricated square pile is 45 mm;
the main reinforcement of each corner of the prefabricated square pile is respectively formed by uniformly distributing five 1420 MPa-level ductile low-relaxation prestressed concrete spiral groove steel bars with the diameter of 12.6 mm;
the winding bars are formed by winding HRB300 steel bars with the diameter of 6.5 mm;
the concrete strength grade of the prefabricated square pile is C40, and the thickness of the protective layer is 32 mm.
The embodiment of the invention adopts another technical scheme that the pile splicing method for the prefabricated square pile for supporting the deep foundation pit and the side slope is carried out according to the following steps:
step S1, after a single prefabricated square pile is manufactured according to the size requirement, one pile is buried in the site as a lower pile, and the pile head of the pile is 0.5-1.0 m higher than the ground;
step S2, utilizing the end plate hole of the butt joint end steel plate of the embedded lower pile section to butt joint a second prefabricated square pile, namely an upper pile section, at the pile head, so that the butt joint end steel plates of the two prefabricated square piles are tightly attached, and the two prefabricated square piles are kept aligned;
step S3, welding the two close-fitting butt end steel plates, and polishing the welding seam after welding to make the surface of the welding seam smooth;
step S4, coating steel adhesive on the hoop wrapping surfaces, namely the outer side surfaces of the hoop wrapping joints of the two prefabricated square piles;
and S5, after the steel adhesive is coated, fixing the butt joint hoop plate at the hoop joint and the butt joint end steel plate of the two prefabricated square piles, enabling the butt joint hoop plate to be tightly attached to and wrap the hoop joint and the side face of the butt joint end steel plate, then welding, and polishing the welding position after welding to enable the surface of the welding line to be flat and smooth.
Further, in the step S2, a guide hoop is arranged at the pile head of the lower pile to keep the two prefabricated square piles aligned, and the misalignment deviation of the two prefabricated square piles is less than or equal to 2 mm;
step S3, welding the two close-fitting butt end steel plates by adopting a groove welding process, simultaneously adopting a carbon dioxide gas shielded welding machine, and polishing a welded junction by using an angle grinder after welding;
the thickness of the steel adhesive coated in the step S4 is 2mm, so that after the butt-joint hoop plate is welded, the cross-sectional dimensions of the butt-joint hooping (the steel plate at the butt-joint end of the two prefabricated square piles coated with the steel adhesive and covering the butt-joint hoop plate and the joint of the hooping) are equal to those of the prefabricated square pile.
Further, after the butt hoop plate is welded in the step S5, a corrosion-resistant protective material is coated on the outer side of the butt hoop plate;
before welding in the step S3, whether the joint of the prefabricated square pile is qualified or not is firstly confirmed, the surface of a steel plate at the butt joint end is cleaned, the groove is cleaned until the metallic luster is exposed, and oil stain and rust are removed; when welding, firstly, symmetrical spot welding is carried out around the groove, and after the upper section pile and the lower section pile are fixed, the guide hoop is removed and then layered symmetrical welding is carried out.
The invention has the beneficial effects that the prefabricated square pile for supporting the deep foundation pit and the side slope and the pile splicing method thereof are provided, the problem that the length of the prefabricated square pile is not enough is solved, and meanwhile, after the prefabricated square pile and the pile splicing method disclosed by the embodiment of the invention are adopted, the joint strength is high, and the anti-cracking and anti-bending performances are obviously improved. A plurality of anchor cable holes are reserved in the prefabricated square pile, the prestressed anchor cable is pulled on the prefabricated square pile, compared with the traditional mode, the use of waist beams is reduced, the shearing strength and the bending resistance and crack resistance of the pile body are obviously improved, the fulcrum rigidity is increased by hundreds of times, meanwhile, the distribution of bending moment of the pile body is optimized, the arrangement of reinforcing bars of the pile body is reduced, and therefore the stress and the performance of an anchor-pull pile supporting system are optimized. Compared with the traditional mode, pile splicing is carried out only through three steps of welding, glue brushing and hooping, pile splicing technology is simple, and construction speed is high. The steel-bonding adhesive can be made of environment-friendly materials, and waste gas and welding slag generated by the pile splicing process are few. The butt joint construction method is safe, environment-friendly, convenient and fast, strong in durability, low in cost and high in efficiency, and has wide application prospects in foundation pit supporting and slope supporting engineering. The problems that the overall stress of anchor cables and pile row systems is reduced by adopting the profile steel waist beam as a force transmission component of the prestressed anchor cables and piles at present, the stability and deformation control of a foundation pit are extremely unfavorable, the length of a single precast pile at present cannot meet the design depth requirement of the foundation pit, and the problems that the joint strength is low and the environment is not protected in the existing pile splicing method are effectively solved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic structural view of a prefabricated square pile joint part according to an embodiment of the present invention.
Fig. 2 is a schematic structural diagram of a prefabricated square pile in the embodiment of the invention.
Fig. 3 is a schematic structural view of a butt strap in an embodiment of the present invention.
Fig. 4 is a sectional view a-a in fig. 2.
Fig. 5 is a sectional view B-B in fig. 2.
Fig. 6 is a cross-sectional view C-C of fig. 2.
FIG. 7 is a schematic plan view of a butt end steel plate according to an embodiment of the present invention.
FIG. 8 is a schematic view of a bending test according to an embodiment of the present invention.
FIG. 9 is a mechanical schematic diagram of a bending test according to an embodiment of the present invention.
FIG. 10 is a schematic diagram of a shear test according to an embodiment of the present invention.
In the figure, 1, a prefabricated square pile, 2, a hoop-wrapping joint, 3, a main rib, 4, a winding rib, 5, an anchor cable hole, 6, a butt hoop plate, 7, a butt end steel plate and 8, an end plate hole are arranged.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
A prefabricated square pile for deep basal pit and side slope support, the structure is shown as figure 1 ~ 2, including solid prefabricated square pile 1, the cross-section of prefabricated square pile 1 is the square, and the cross-section length of side H of prefabricated square pile 1 of this embodiment is 600 mm. Both ends of the prefabricated square pile 1 are reserved with lengths L1The section of the 500mm hoop-covered joint 2 is a square with the size of (H-20) mm x (H-20) mm。
Prefabricated square pile 1 is equipped with the anchor rope hole 5 of its pile body of a plurality of perpendicular to along length direction, and a plurality of anchor rope holes 5 all are located prefabricated square pile 1's central line, and anchor rope hole 5 is the screw hole, and its internal diameter is 180 mm. Set up the anchor rope hole too few, difficult satisfying the user demand, it is too much to reserve the anchor rope hole, is difficult to guarantee prefabricated square pile rigidity, and this application sets up two adjacent anchor rope holes 2000 ~ 4000mm apart from, can enough guarantee the rigidity of prefabricated square pile 1, can satisfy the user demand again. The anchor cable holes 5 are perpendicular to the prefabricated square pile 1, so that the prestressed anchor cables can uniformly pull the prefabricated square pile 1 and are easy to control and adjust.
The length 2L of the prefabricated square pile 1 is 15000mm, wherein L is L2+L3In the embodiment, the concrete strength grade of the precast square pile 1 is C40, and the thickness of the protective layer is 32 mm. The main reinforcement 3 in the prefabricated square pile 1 adopts a 1420 MPa-level ductile low-relaxation prestressed concrete spiral groove steel bar, the winding reinforcement 4 adopts an HRB300 (I-level) steel bar, the winding reinforcement 4 is symmetrically arranged by taking the center of the prefabricated square pile 1 as the center, and the winding reinforcement is arranged in the middle of the prefabricated square pile 1, namely L in figure 23The arrangement interval at the length position is 80mm, L36500 mm; the steel bars 4 are wound on two sides of the prefabricated square pile 1, namely L in figure 22The arrangement interval at the position of the length is 450mm, L2Is 1000 mm. As shown in fig. 4 to 6, 4 Φ 12.6 means four main bars 3 with a diameter of 12.6mm, 6 Φ 12.6 means six main bars 3 with a diameter of 12.6mm, and the main bars 3 are respectively distributed in an L shape at four corners of the prefabricated square pile 1.
It means that the diameter of the winding rib 4 is 6.5mm and the winding pitch thereof is 45mm,
it means that the diameter of the winding rib 4 is 6.5mm and the winding pitch thereof is 80 mm. The arrangement of the main ribs 3 and the winding ribs 4 of the prefabricated square pile 1 is matched with the arrangement of the anchor cable holes 5, and the prefabricated square pile 1 does not interfere with the anchor cable holes 5 while the rigidity is not influenced.
The end faces of the two ends of the prefabricated square pile 1 are provided with butt joint end steel plates 7 and butt joint hoop plates 6 matched with the butt joint end steel plates 7, and the butt joint end steel plates 7 are thick in the embodimentThe length is 20mm, the end face shape of the butt end steel plate 7 is a square with the length multiplied by the width (H-20) mm multiplied by (H-20) mm, the butt hoop plate 6 of the embodiment is formed by butt joint of two L-shaped steel plates with the same specification, as shown in figure 3, the inner side length H of the cross section of the butt hoop plate 6 is 580mm (H-20mm), the side length of the cross section of the butt hoop plate 6 is the same as the side length of the cross section of the shroud ring joint 2, and the length of the butt hoop plate is 1040mm (2 (L-20 mm1+20) mm, namely the sum of the length of the hoop-covered joint 2 of the two butted prefabricated square piles 1 and the thickness of the butt-joint end steel plate 7), the thickness is 8mm, the outer side length is 588mm (namely the sum of the inner side length h and the thickness), and the butt-joint hoop plate 6 is welded and sleeved at the hoop-covered joint 2 and the butt-joint end steel plate 7 through a groove welding process. The butt hoop plate 6 is made of a Q235 common hot rolled steel plate, and as shown in FIG. 7, an end plate hole 8 is formed in the butt end steel plate 7 and is used for butt joint with the butt end steel plate 7 on the other prefabricated square pile 1.
The pile splicing method of the prefabricated square pile for supporting the deep foundation pit and the side slope is carried out according to the following steps:
and step S1, after the single prefabricated square pile 1 is manufactured according to the size requirement, firstly burying a prefabricated square pile 1 as a lower pile on site, and enabling the pile head to be 0.5-1.0 m higher than the ground.
And step S2, utilizing the end plate hole 8 of the butt joint end steel plate 7 of the embedded lower pile section to butt joint a second prefabricated square pile 1, namely an upper pile section, at the pile head, enabling the two butt joint end steel plates 7 which are butted to be tightly attached, and keeping the two prefabricated square piles 1 aligned.
At the moment, the pile head of the lower pile can be provided with a guide hoop so as to facilitate the upper pile to be in place and be in butt joint with the lower pile, ensure that the upper pile and the lower pile are aligned, and the dislocation deviation is not more than 2 mm.
And step S3, welding the two close-fitting butt end steel plates 7 by adopting a groove welding process, and polishing a welded junction by using an angle grinder after welding by adopting a carbon dioxide gas shielded welding machine to ensure that the surface of the welded junction is smooth.
Before welding, whether the joint of the prefabricated square pile 1 is qualified or not is firstly confirmed, the surface of the butt joint end steel plate 7 is cleaned, the groove is cleaned until the metallic luster is exposed, and oil stain and iron rust are removed. When welding, firstly, symmetrical spot welding is carried out around the groove, after the upper section pile and the lower section pile are fixed, the guide hoop is removed, and then layered welding is carried out, and the welding is carried out symmetrically. The manual welding or the carbon dioxide arc welding is adopted, the number of welding layers is preferably three, the outer layer can be welded after the inner layer welding slag is cleaned up, the welding line is full and continuous, and the root part is welded thoroughly.
Step S4, coating steel adhesive on the outer side surfaces of the hoop-covered joint 2 and the butt-joint end steel plate 7 of the two prefabricated square piles 1, and controlling the thickness of the coated steel adhesive within 2mm, because the side length difference of the cross sections of the hoop-covered joint 2 and the prefabricated square pile 1 is 20mm, the total thickness of the butt-joint hoop plates 6 on the two sides of the hoop-covered joint 2 is 16mm, in order to ensure that the butt-joint hoop-covered joint part is smoothly connected with the surface of the prefabricated square pile 1 after the hoop-covered joint is finished, the thickness of the steel adhesive must be controlled within 2mm, namely the thickness of the double-layer steel adhesive is controlled within 4 mm.
Step S5, after the steel adhesive is coated, fixing the butt-joint hoop plate 6 at the positions of the hoop wrapping joints 2 and the butt-joint end steel plates 7 of the two prefabricated square piles 1, enabling the butt-joint hoop plate 6 to be tightly attached to and wrap the side faces of the hoop wrapping joints 2 and the side faces of the butt-joint end steel plates 7, then welding the butt-joint hoop plate 6 by adopting a groove welding process and a carbon dioxide gas shielded welding machine, polishing the welding position by using an angle grinder after welding is finished, enabling the surface of a welding line to be flat and smooth, and ensuring that the butt-joint hoop wrapping joints are smoothly connected with the prefabricated square piles 1; and then, the outer side of the butt-joint hoop plate 6 is coated with a corrosion-resistant protective material, so that when the prefabricated square pile 1 is used in an area containing corrosive media in soil, corrosion caused by electrochemical reaction at a pile connecting position is avoided, and the corrosion resistance and durability of the prefabricated square pile are ensured. The pile can be continuously sunk after the welding part is naturally cooled, the cooling time is not less than 8min, and the pile is not strictly cooled by water or sunk immediately after the welding.
The embodiment of the invention solves the problem of insufficient length of the precast pile, and simultaneously, the strength of the butt joint of the precast square pile and the pile splicing method is effectively improved, the joint strength is high, and the shearing resistance and the bending resistance are obviously improved.
Bending resistance test:
the vertical upward loading is adopted, and the test sketch is shown in figures 8-9.
1. Test loading
1) The pre-loading is carried out before the test, and the pre-loaded load is maintained for 5 min. The pre-loading should be controlled to be stressed within the elastic range, and no cracks or other forms of loading residual values are generated.
2) Loading from zero to 80 percent of the anti-cracking bending moment according to the grade difference of 20 percent of the anti-cracking bending moment, and lasting for 3min for each grade of load; and then continuously loading to 100 percent of the anti-cracking bending moment according to the grade difference of 10 percent of the anti-cracking bending moment, wherein the duration time of each grade of load is 3 min. And (5) observing whether cracks appear in the test process, and recording the distribution and development of the cracks.
3) If no crack appears when the crack resistance bending moment is 100%, continuing loading according to the grade difference of 10% of the crack resistance bending moment, and continuing the loading for 3min until the crack appears.
4) And continuously loading the test pile to the limit state according to the grade difference of 10% of the anti-cracking bending moment, wherein the duration of each grade of load is 3min, and observing and recording each reading.
2. Indication of extreme conditions
1) The width of a stressed crack of the concrete in the tension area reaches 1.5 mm;
2) the tensioned steel bar is broken;
3) the weld breaks or breaks;
4) concrete damage of the compression zone;
5) it is impossible to apply load or maintain a stable load.
3. Method for determining anti-crack load and ultimate load
1) Determination of the anti-cracking load
a. When a crack appears for the first time in the loading process, taking the previous stage load value as an actual measured value of the crack resistance load;
b. when the crack appears for the first time within the specified load duration, taking the average value of the load value of the current level and the load value of the previous level as the actual measured value of the crack resistance load;
c. when a crack occurs for the first time after the specified load duration is over, the load value of this level should be taken as the actual measured value of the crack resistance load.
2) Determination of the ultimate load
a. When one of the conditions listed in the sign of the limit state appears in the loading process, taking the previous stage load value as the limit load measured value;
b. when one of the conditions listed in the sign of the limit state appears in the specified load duration, taking the average value of the load value of the current level and the load value of the previous level as the actual measured value of the limit load;
c. when one of the conditions listed as the limit state flag occurs after the end of the predetermined load duration, the load value at that time is taken as the actual limit load measurement value.
And (3) calculating a bending moment:
when load is vertically upwards applied, the bending moment calculation formula is as follows:
in the formula, M is bending moment (kN M), W is prefabricated square pile weight (kN), P is load (kN), and L is prefabricated square pile length (M).
The bending test data of the joints obtained by measurement are shown in table 1, and as can be seen from table 1, the cracking resistance and the bending resistance are excellent, the joint connection strength is not less than the prefabricated square pile strength, and the reliability of the pile splicing process of the prefabricated concrete square pile is verified.
TABLE 1 bending strength test data of prefabricated square pile
| Serial number | Pile shape | Anti-cracking bending moment (kN. m) | Ultimate bending moment (kN. m) |
| 1 | 500 pile extension | 302.7 | 459.5 |
| 2 | 500 pile splicing is not required | 257.9 | 454.7 |
| 3 | 600 pile extension | 424.4 | 807.5 |
| 4 | 600 pile without connection | 353.0 | 785.4 |
Shear performance test:
the prefabricated square pile test piece of the embodiment is loaded by using a YAW-10000F type microcomputer control electro-hydraulic servo multifunctional testing machine, as shown in FIG. 10. And (3) carrying out graded encryption on the load near a theoretical calculation value of the cracking load, and converting the loading mode into displacement loading after the width of the main inclined crack of the bending shear section reaches 1.5mm until the test piece is completely destroyed. And a digital displacement meter is adopted for measuring the deformation of the test piece. The strain measuring point arrangement and the number are shown in the numbers 1-6 of FIG. 10 in detail, the strain measuring point arrangement number on the side face is arranged in brackets, a 50mm multiplied by 3mm type resistance strain gauge is adopted for strain observation, and a DH3816 static strain testing system is used for a data acquisition device. The width of the crack is measured and read by a DJCK-2 type crack width measuring instrument, and the distribution and development records of the crack are recorded by a digital camera device. The measured shear strength test data are shown in table 2, and the table 2 shows that the shear resistance is excellent, and the reliability of the precast concrete square pile splicing process is verified.
TABLE 2 shear strength test data of prefabricated square pile
| Serial number | Pile shape | Shear strength (kN) |
| 1 | 500 pile extension | 495.1 |
| 2 | 500 pile splicing is not required | 470.0 |
| 3 | 600 pile extension | 600.9 |
| 4 | 600 pile without connection | 576.8 |
In tables 1 and 2, 500 pile splicing indicates a square pile formed by butting prefabricated square piles, with the side length of the cross section of the prefabricated square pile 1 being 500mm, which are used for deep foundation pit and slope support, and 500 pile splicing does not indicate a prefabricated square pile, with the side length of the cross section of the prefabricated square pile 1 being 500mm, which is used for deep foundation pit and slope support; the 600 pile splicing means a square pile formed by butting the prefabricated square piles with the side length of the cross section of the prefabricated square pile 1 being 600mm and used for deep foundation pit and slope support, and the 600 pile splicing means a prefabricated square pile with the side length of the cross section of the prefabricated square pile 1 being 600mm and used for deep foundation pit and slope support.
Compared with the traditional mode, the anchor cable holes are reserved, the prestressed anchor cable is pulled on the pile body, the use of waist beams is reduced, the anti-cracking, anti-bending and anti-shearing strength of the pile body is obviously increased, the fulcrum rigidity is increased by one hundred times, meanwhile, the bending moment distribution of the pile body is optimized, the reinforcing bars of the pile body are reduced, and therefore the stress and the exertion of an anchor-pull pile supporting system are optimized. Compared with the traditional mode, the method only needs to butt joint the pile in three steps of welding, brushing glue and wrapping hoops, and is simple in pile joint process and high in construction speed. The steel-bonding adhesive can be made of environment-friendly materials, and waste gas and welding slag generated by the pile splicing process are few. The butt joint construction method is safe, environment-friendly, convenient and fast, strong in durability, low in cost and high in efficiency, and has wide application prospects in foundation pit supporting and slope supporting engineering.
The above description is only for the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.
Claims (10)
1. A prefabricated square pile for deep basal pit and side slope support, its characterized in that, including solid prefabricated square pile (1), prefabricated square pile (1) is equipped with anchor rope hole (5) of its pile body of a plurality of perpendicular to along its length direction, and a plurality of anchor rope holes (5) all are located the central line of prefabricated square pile (1), anchor rope hole (5) do not interfere with main muscle (3) of prefabricated square pile (1) and around muscle (4).
2. The prefabricated square pile for deep foundation pit and slope support according to claim 1, wherein the anchor cable holes (5) are threaded holes with an inner diameter of 180mm, and the distance between two adjacent anchor cable holes (5) is 2000-4000 mm.
3. The prefabricated square pile for deep foundation pit and slope support according to claim 1, wherein the cross section of the prefabricated square pile (1) is square with the side length of Hmm, the two ends of the prefabricated square pile are respectively provided with a wrapping hoop joint (2) with a certain length, the end faces of the two ends of the prefabricated square pile (1) are provided with a butt end steel plate (7) and a butt hoop plate (6) matched with the butt end steel plate (7) and the wrapping hoop joint (2), and the butt hoop plate (6) is wrapped and tightly attached to the wrapping hoop joint (2) and the butt end steel plate (7).
4. The prefabricated square pile for deep foundation pit and side slope support according to claim 3, wherein the cross section of the hoop-covered joint (2) and the butt end steel plate (7) is square with the size of (H-20) mm x (H-20) mm;
the length of the butt joint hoop plate (6) is 2 times of the sum of the thickness of the butt joint end steel plate (7) and the length of the hoop-wrapping joint (2), the inner size of the cross section of the butt joint hoop plate (6) is equal to the cross section sizes of the hoop-wrapping joint (2) and the butt joint end steel plate (7), and the outer size of the cross section of the butt joint hoop plate (6) is equal to the cross section size of the prefabricated square pile (1).
5. The prefabricated square pile for deep foundation pit and slope support according to claim 3, wherein the butt end steel plate (7) is provided with an end plate hole (8), and the thickness of the butt end steel plate (7) is 20 mm.
6. The precast square pile for deep foundation pit and slope support according to claim 3, wherein the butt hoop plate (6) is formed by butt-fixing two L-shaped steel plates with the same specification, and the thickness of the butt hoop plate is 8 mm.
7. The prefabricated square pile for deep foundation pit and side slope support according to any one of claims 1 to 6, wherein the cross section of the prefabricated square pile (1) is square, the main reinforcements (3) are respectively distributed at four corners of the prefabricated square pile (1) in an L shape, the winding reinforcements (4) are symmetrically arranged by taking the center of the prefabricated square pile (1) as the center, the arrangement interval of the winding reinforcements (4) at 13000mm length in the middle of the prefabricated square pile (1) is 80mm, and the arrangement interval of the winding reinforcements (4) at 1000mm length at two ends of the prefabricated square pile (1) is 45 mm;
the main reinforcement (3) of each corner of the prefabricated square pile (1) is respectively formed by uniformly distributing five 1420 MPa-level ductile low-relaxation prestressed concrete spiral groove steel rods with the diameter of 12.6 mm;
the winding rib (4) is formed by winding HRB300 steel bars with the diameter of 6.5 mm;
the concrete strength grade of the prefabricated square pile (1) is C40, and the thickness of the protective layer is 32 mm.
8. A pile extension method of a prefabricated square pile for deep foundation pit and side slope support according to claim 7, which is carried out according to the following steps:
step S1, after a single prefabricated square pile (1) is manufactured according to the size requirement, burying a pile serving as a lower pile on site, and enabling the pile head to be 0.5-1.0 m higher than the ground;
s2, butting a second prefabricated square pile (1), namely an upper pile, at the pile head by using an end plate hole (8) of a butt joint end steel plate (7) of the embedded lower pile, so that the butt joint end steel plates (7) of the two prefabricated square piles (1) are tightly attached, and the two prefabricated square piles (1) are kept aligned;
step S3, welding the two close-fitting butt end steel plates (7), and polishing the welding seam after welding to make the surface of the welding seam smooth;
step S4, uniformly brushing steel adhesive on the hooping surface, namely the outer side surface of the hooping joint (2) of the two prefabricated square piles (1);
s5, after the steel adhesive is coated, fixing the butt joint hoop plate (6) at the hoop wrapping joints (2) and the butt joint end steel plates (7) of the two prefabricated square piles (1), enabling the butt joint hoop plate (6) to be tightly attached to and wrap the hoop wrapping joints (2) and the side faces of the butt joint end steel plates (7), then welding, and polishing the welding positions after welding to enable the surfaces of welding seams to be flat and smooth.
9. The pile extension method of the prefabricated square pile for deep foundation pit and side slope support according to claim 8, wherein the step S2 is to arrange a guide hoop at the pile head of the lower pile to keep the two prefabricated square piles (1) aligned, and the misalignment deviation of the two prefabricated square piles (1) is less than or equal to 2 mm;
in the step S3, a groove welding process is adopted to weld the two close-fitting butt end steel plates (7), a carbon dioxide gas shielded welding machine is adopted, and an angle grinder is used for grinding a welded junction after welding;
the thickness of the steel adhesive coated in the step S4 is 2mm, so that after the butt joint hoop plate (6) is welded, the size of the cross section of the butt joint hoop is equal to that of the cross section of the prefabricated square pile (1).
10. The pile extension method of the prefabricated square pile for deep foundation pit and slope support according to claim 9, wherein after the welding of the butt hoop plate (6) of the step S5 is completed, a corrosion-resistant protective material is coated on the outer side of the butt hoop plate (6);
before welding in the step S3, whether the joint of the prefabricated square pile (1) is qualified or not is firstly confirmed, the surface of the butt joint end steel plate (7) is cleaned, the groove is cleaned until the metallic luster is exposed, and oil stain and iron rust are removed; when welding, firstly, symmetrical spot welding is carried out around the groove, and after the upper section pile and the lower section pile are fixed, the guide hoop is removed and then layered symmetrical welding is carried out.
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