CN114439015A - Construction method for improving rock-socketed depth of large-diameter cast-in-place pile - Google Patents
Construction method for improving rock-socketed depth of large-diameter cast-in-place pile Download PDFInfo
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- 238000010276 construction Methods 0.000 title claims abstract description 57
- 229910000831 Steel Inorganic materials 0.000 claims description 186
- 239000010959 steel Substances 0.000 claims description 186
- 238000004873 anchoring Methods 0.000 claims description 53
- 239000011435 rock Substances 0.000 claims description 43
- 230000002787 reinforcement Effects 0.000 claims description 40
- 239000002689 soil Substances 0.000 claims description 19
- 238000000034 method Methods 0.000 claims description 17
- 238000003466 welding Methods 0.000 claims description 15
- 239000004567 concrete Substances 0.000 claims description 13
- 238000005553 drilling Methods 0.000 claims description 7
- 238000009412 basement excavation Methods 0.000 claims description 5
- 230000003068 static effect Effects 0.000 claims description 4
- 238000007664 blowing Methods 0.000 claims description 3
- 238000005266 casting Methods 0.000 claims description 3
- -1 connecting rings Substances 0.000 claims description 2
- 230000015572 biosynthetic process Effects 0.000 claims 1
- 239000010410 layer Substances 0.000 description 13
- 230000008901 benefit Effects 0.000 description 5
- 239000011083 cement mortar Substances 0.000 description 4
- 230000000903 blocking effect Effects 0.000 description 2
- 239000004927 clay Substances 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 238000007667 floating Methods 0.000 description 2
- 238000005452 bending Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000011229 interlayer Substances 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
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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
- E02D15/00—Handling building or like materials for hydraulic engineering or foundations
- E02D15/02—Handling of bulk concrete specially for foundation or hydraulic engineering purposes
- E02D15/04—Placing concrete in mould-pipes, pile tubes, bore-holes or narrow shafts
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D15/00—Handling building or like materials for hydraulic engineering or foundations
- E02D15/08—Sinking workpieces into water or soil inasmuch as not provided for elsewhere
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D31/00—Protective arrangements for foundations or foundation structures; Ground foundation measures for protecting the soil or the subsoil water, e.g. preventing or counteracting oil pollution
- E02D31/10—Protective arrangements for foundations or foundation structures; Ground foundation measures for protecting the soil or the subsoil water, e.g. preventing or counteracting oil pollution against soil pressure or hydraulic pressure
- E02D31/12—Protective arrangements for foundations or foundation structures; Ground foundation measures for protecting the soil or the subsoil water, e.g. preventing or counteracting oil pollution against soil pressure or hydraulic pressure against upward hydraulic pressure
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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
- E02D5/34—Concrete or concrete-like piles cast in position ; Apparatus for making same
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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
- E02D5/34—Concrete or concrete-like piles cast in position ; Apparatus for making same
- E02D5/38—Concrete or concrete-like piles cast in position ; Apparatus for making same making by use of mould-pipes or other moulds
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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
- E02D5/74—Means for anchoring structural elements or bulkheads
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D7/00—Methods or apparatus for placing sheet pile bulkheads, piles, mouldpipes, or other moulds
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D2600/00—Miscellaneous
- E02D2600/30—Miscellaneous comprising anchoring details
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Abstract
The invention belongs to the technical field of geotechnical engineering foundation pit supporting and construction, and relates to a construction method for improving the rock-socketed depth of a large-diameter cast-in-place pile.
Description
Technical Field
The invention belongs to the technical field of geotechnical engineering foundation pit supporting and construction, and relates to a construction method for improving the rock-socketed depth of a large-diameter cast-in-place pile.
Background
In recent years, the miniature advanced steel pipe pile has the advantages of good site adaptability, light weight, high bearing capacity, good penetrability, flexible pile position arrangement, small construction machinery, small disturbance to a reinforced stratum, small construction vibration, strong penetrability, high construction speed and large foundation pit supporting depth, and has obvious economic benefit advantages compared with a cast-in-place pile and a traditional steel pipe pile. The large-diameter cast-in-place pile has the advantages of no vibration, no soil squeezing, low noise, suitability for dense urban building areas and the like during construction, and is widely applied to construction.
The row pile is strutted and is had advantages such as supporting construction rigidity is big, construction speed is fast, the plane is arranged in a flexible way, can arrange one row or double, combine miniature steel-pipe pile and prestressed anchorage pole (anchor rope), the compound supporting construction that the soil nail combination formed, the lateral rigidity of whole supporting system has been improved, miniature steel-pipe pile is as main atress component, both can play the bending resistance effect and can improve the soil body stress field, the displacement field, restriction foundation ditch deformation, increase the overall stability of foundation ditch, this type of novel retaining structure is in side slope reinforcement, foundation ditch support etc. aspect popularization and application gradually.
According to the requirements of the current national building pile foundation technical specification (JGJ94-2008), the depth of the full section of the embedded rock bored concrete pile embedded into the inclined complete and relatively complete rock is not less than 0.4d and not less than 0.5 m; the rock embedding depth of the medium-stroke rocks with the inclination larger than 30% is properly increased according to the inclination and the integrity of the rocks; the depth of embedding into flat, unbroken hard and harder rock is preferably not less than 0.2d and not less than 0.2 m. According to the regulations of the existing national building foundation pit supporting technical rules (JGJ120-2012), the embedding depth of the cantilever type retaining structure, the embedding depth of the anchor type retaining structure and the embedding depth of the support type retaining structure all meet the requirement of embedding stability, and the embedding depth of the cantilever type structure is not less than 0.8 h; for a single-pivot supporting and blocking type structure, the time is not less than 0.3 h; for a multi-fulcrum supporting and blocking type structure, the number of h is not less than 0.2h, and h is the depth of the foundation pit. In addition, no weak interlayer, fracture zone, cave and gap distribution should be formed in the range of the pile bottom 3d, especially in the case of a single pile with large load.
The upper fourth system of regions such as Qingdao, Wuhan, Dalian and Shenzhen has lower strength and the lower matrix has higher strength, and belongs to a typical soil-rock composite foundation; the red clay in Guangxi areas is widely distributed, and has the main characteristic that the red clay is hard at the top and soft at the bottom, and a layer of soft flowing plastic soil exists at the soil-rock junction. When adopting row pile retaining structure to the excavation supporting in the compound area of above-mentioned soil rock, the row pile should pass the soil rock interface, inlays in stabilizing the stratum, guarantees that row pile buried depth is far greater than the foundation ditch excavation depth, prevents "hanging foot stake" and appears. However, in the actual construction process of the area, the upper soil layer is fast in impact hole forming, the lower rock entering is slow in impact hole forming, site rocks are strongly developed and mostly meet half rocks, deviation is frequently corrected, and therefore hole forming efficiency is extremely low, construction is difficult, progress is delayed seriously, and construction difficulty is high.
CN109914395A discloses a rapid construction method of a large-diameter socketed pile and a structure thereof, which solve the construction problem of a hard rock large-diameter socketed pile; CN111455985A discloses a steel pipe composite rock-socketed pile foundation structure and a construction method, which reduce the construction difficulty of rock-socketed piles and shorten the construction period; but the above-mentioned technique all fails to solve the problems of accurate positioning and pile body deviation of the socketed pile, and the problems of steel reinforcement cage floating up when pressure grouting is carried out on the cast-in-place pile. Therefore, a new construction method for improving the rock-socketed depth of the large-diameter cast-in-place pile is needed.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, and seeks a construction method for improving the rock-socketed depth of a large-diameter cast-in-place pile aiming at a soil-rock-bearing combined stratum.
In order to realize the purpose, the concrete construction process for improving the rock-socketed depth of the large-diameter cast-in-place pile comprises the following steps:
(1) determining relevant parameters of the large-diameter bored concrete pile and the miniature steel pipe pile according to the requirements of a design drawing, wherein the relevant parameters comprise the hole forming diameters of a soil layer and a rock stratum;
(2) after the construction site is leveled, positioning the pile position of the large-diameter cast-in-place pile, covering a soil layer, manually digging holes, and excavating to the elevation of the soil-rock combination layer; if the geological condition is not good, mechanical pore-forming is adopted;
(3) determining the diameter and the wall thickness of the positioning sleeve and the inner lap joint length of the miniature steel pipe pile and the positioning sleeve according to the diameter and the length of the miniature steel pipe pile;
(4) binding a steel reinforcement cage according to the designed length and the pile diameter of the large-diameter cast-in-place pile, vertically aligning a positioning sleeve with a preset position at the bottom of the inner wall of the steel reinforcement cage, binding the positioning sleeve on the large-diameter cast-in-place pile steel reinforcement cage by using at least two fixed steel bars, welding the fixed steel bars on stirrups at corresponding positions, enabling the fixed steel bars to be in direct close contact with the positioning sleeve, welding the fixed steel bars with the stirrups of the steel reinforcement cage, enabling the contact points of the positioning sleeve and the fixed steel bars to be binding fixed points, and overlapping a miniature steel pipe pile in each positioning sleeve; the embedded positions of the positioning sleeves are uniformly distributed along the inner wall of the reinforcement cage;
(5) vertically lowering the reinforcement cage provided with the positioning sleeve in the step (4);
(6) adopting a down-the-hole drill to punch a hole in the lower rock stratum, enabling a drill bit of the down-the-hole drill to extend into a positioning sleeve, vertically and accurately drilling a hole downwards from a soil-rock junction surface until the designed elevation of rock embedding of the pile tip of the miniature steel pipe pile is reached, and blowing out rock debris in hole drilling and hole forming by utilizing high-pressure air generated by the down-the-hole drill after construction is finished;
(7) the miniature steel pipe pile extends into the positioning sleeve from the top until the pile tip of the miniature steel pipe pile is embedded into a rock stratum designed elevation;
(8) after the micro steel pipe pile is placed down, ground anchoring components on two sides of the large-diameter cast-in-place pile are assembled, and the ground anchoring components are formed by assembling anchoring angle steel, connecting rings, steel wire ropes and connecting plates; one surface of the connecting plate is in full-welding connection with one end of the anchoring angle steel, the non-welding end of the anchoring angle steel is squeezed into a soil layer on the periphery of the large-diameter cast-in-place pile through the non-welding surface of the connecting plate by using mechanical static pressure or hammering, and a ground anchoring member is pressed into two sides of each large-diameter cast-in-place pile; one surface of the connecting plate is welded with anchoring angle steel, and the other surface is provided with two connecting rings which are tightly welded with the connecting plate;
(9) placing the weight I-shaped steel above the large-diameter cast-in-place pile steel reinforcement cage, wherein the end face of one side flange of the weight I-shaped steel is in direct contact with the top of the large-diameter cast-in-place pile steel reinforcement cage, two ends of the weight I-shaped steel are aligned with anchoring positions of anchoring angle steel, two ends of a steel wire rope penetrate through two connecting rings on a connecting plate, the weight I-shaped steel is firmly bound with a ground anchoring component, and two ends of the weight I-shaped steel are bound with the ground anchoring component; the weighting I-steel is matched with a ground anchoring member to obtain a pulling resistance force so as to ensure that the large-diameter cast-in-place pile reinforcement cage and the positioning sleeve do not float upwards in the subsequent pressure grouting process;
(10) a plurality of grouting holes are reserved at the bottom of the miniature steel pipe pile, commercial concrete is pumped into the large-diameter cast-in-place pile to complete casting, then a grouting pipe extends into the bottom of the miniature steel pipe pile to perform pressure grouting until the internal grouting of all the miniature steel pipe piles and the positioning sleeve is completed, and the pressure grouting process ensures that a reinforcement cage and the positioning sleeve of the large-diameter cast-in-place pile do not float upwards;
(11) after the steps are completed, the ballasting I-steel and the ground anchoring member are mechanically pulled out so as to be reused, and the construction process of improving the rock-socketed depth of the single large-diameter cast-in-place pile is completed.
Furthermore, the hole forming mode of the large-diameter cast-in-place pile is manual hole digging or mechanical hole forming, the hole forming aperture needs to be slightly larger than the designed pile diameter of the large-diameter cast-in-place pile, and the pile length and the pile diameter of the large-diameter cast-in-place pile are designed according to stratum conditions and supporting requirements.
Furthermore, the positioning sleeve is a commercially available steel pipe commonly used in engineering, the inner diameter of the positioning sleeve is larger than the outer diameter of the pile body of the miniature steel pipe pile, the length of the positioning sleeve is not smaller than the length of the pile body of the large-diameter cast-in-place pile, and the positioning sleeve is preferably a thin-wall steel pipe with the diameter of 168mm and the wall thickness of 4 mm.
Furthermore, the number of the binding fixing points is not less than two, and the distance between every two adjacent binding fixing points is not more than 1.5 m.
Furthermore, the miniature steel pipe pile is a commercially available steel pipe commonly used in engineering, preferably a thin-wall steel pipe with the diameter of 108mm and the wall thickness of 8 mm; the length of the pile body of the miniature steel pipe pile meets the rock-socketed depth required by the current specification, and the length of the lap joint of the miniature steel pipe pile and the inner wall of the positioning sleeve is not less than 3 times of the diameter of the large-diameter cast-in-place pile; the depth of the pile tip of the miniature steel pipe pile is at least 1.0m greater than the excavation depth of the foundation pit.
Furthermore, the reinforcement cage is bound and fixed with a plurality of positioning sleeves according to the designed pile diameter of the large-diameter cast-in-place pile, and when the designed pile diameter of the large-diameter cast-in-place pile is 800mm, three positioning sleeves are arranged; when the pile diameter is designed to be 1200-1400 mm, arranging four positioning sleeves; when the pile diameter is larger than 1400mm, five or six positioning sleeves are arranged, a miniature steel pipe pile is lapped in each positioning sleeve, and the fixing position is installed according to the design embedded position of the miniature steel pipe pile.
Furthermore, the hole forming mode of embedding the miniature steel pipe pile into the rock stratum adopts a down-the-hole drill to form the hole.
Furthermore, the weight-bearing I-steel is a common commercially available I-steel commonly used in engineering, the preferred specification (waist height, leg width and waist thickness) is 12# (120 × 80 × 5.5mm) or 14# (140 × 80 × 5.5mm), and the length of the weight-bearing I-steel is 3 times of the diameter of the large-diameter cast-in-place pile.
Further, the anchoring angle steel, the connecting ring, the steel wire rope and the connecting plate are all common commercial products in engineering; the selected specification of the anchoring angle steel (side width and side thickness) is 20 multiplied by 4mm, the length is selected according to the pile length of the large-diameter cast-in-place pile 1, and the length is not less than 3 m; the connecting plate is a square thick-wall steel plate, the side length is not less than 30mm, the wall thickness is not less than 15mm, the side length is greater than the width of the side of the anchoring angle steel, and the aperture of the connecting ring is greater than the diameter of the steel wire rope; the connecting ring is a circular ring or a semicircular ring, and the requirement on stress strength is met.
Compared with the prior art, the construction method is simple, the operation is convenient and safe, the 'hanging foot pile' can be prevented, the problem that the large-diameter cast-in-place pile is difficult to enter the rock can be solved, the accurate drilling and pile sinking of the rock stratum can be realized, the embedding depth is ensured, the steel reinforcement cage is prevented from floating upwards in the pressure grouting process, the upper soil layer is dug manually, the disturbance to the adjacent building around the upper soil layer is reduced, the construction is convenient and fast, and the cost is saved.
Drawings
FIG. 1 is a schematic view of the present invention after completion of construction.
FIG. 2 is a top view of the present invention after completion of construction.
Fig. 3 is a front elevation view after the construction of the present invention is completed.
FIG. 4 is a side elevational view of the present invention after completion of construction.
FIG. 5 is a schematic diagram of a connecting plate structure according to the present invention.
Fig. 6 is a cross-sectional view 1-1 of fig. 2 according to the present invention.
Fig. 7 is a cross-sectional view 2-2 of fig. 2 in accordance with the present invention.
Detailed Description
The invention is further illustrated by the following examples in conjunction with the accompanying drawings.
Example (b):
the concrete construction process for improving the rock-socketed depth of the large-diameter cast-in-place pile comprises the following steps:
(1) determining relevant parameters of the large-diameter bored concrete pile 1 and the miniature steel pipe pile 6 according to the requirements of a design drawing, wherein the relevant parameters comprise the hole forming diameters of a soil layer and a rock stratum and the like;
(2) after the construction site is leveled, the pile position of the large-diameter cast-in-place pile 1 is firstly positioned, the upper soil layer is covered with a manual hole digging mode, and the soil-rock combination layer is excavated to the elevation position; if the geological condition is not good, mechanical hole forming is adopted;
(3) according to the diameter and the length of the miniature steel pipe pile 6, the diameter and the wall thickness of the positioning sleeve 3 and the inner lap joint length of the miniature steel pipe pile 6 and the positioning sleeve 3 are determined, in the embodiment, the miniature steel pipe pile 6 is a thin-wall steel pipe with the diameter of 108mm and the wall thickness of 8mm, and the positioning sleeve 3 is a thin-wall steel pipe with the diameter of 168mm and the wall thickness of 4 mm; the inner lap length of the miniature steel pipe pile 6 and the positioning sleeve 3 is three times of the designed pile diameter of the large-diameter cast-in-place pile 1; the inner diameter of the positioning sleeve 3 must be larger than the outer diameter of the miniature steel pipe pile 6 and the diameter of a drill bit of a down-the-hole drill used, the length is not smaller than the pile length of the large-diameter cast-in-place pile 1, and the positioning sleeve is reasonably selected to facilitate the operation of a down-the-hole drill bit and the hoisting and lowering of the miniature steel pipe pile 6;
(4) binding a steel reinforcement cage 2 according to the designed length and the pile diameter of a large-diameter cast-in-place pile 1, vertically aligning a positioning sleeve 3 with a preset position at the bottom of the inner wall of the steel reinforcement cage 2, binding the positioning sleeve 3 to the large-diameter cast-in-place pile steel reinforcement cage 2 by using at least two fixed steel bars 4, welding the fixed steel bars 4 on stirrups at corresponding positions, enabling the fixed steel bars 4 to be directly and closely contacted with the positioning sleeve 3, welding the fixed steel bars 4 with the stirrups of the steel reinforcement cage 2, enabling the contact point of the positioning sleeve 3 and the fixed steel bars 4 to be binding fixed points 5, and enabling the distance between every two adjacent binding fixed points 5 to be not more than 1.5 m; the number of the positioning sleeves 3 is adjusted according to the designed pile diameter of the large-diameter cast-in-place pile 1, and when the designed pile diameter of the large-diameter cast-in-place pile 1 is 800mm, 3 positioning sleeves 3 are arranged; designing the pile diameter to be 1200-1400 mm, and arranging 4 positioning sleeves 3; when the pile diameter is larger than 1400mm, arranging 5-6 positioning sleeves 3; a miniature steel pipe pile 6 is lapped in each positioning sleeve 3; the embedded positions of the positioning sleeves 3 are uniformly distributed along the inner wall of the reinforcement cage 2;
(5) completing the steps, and lowering the reinforcement cage 2 provided with the positioning sleeve 3 in the step (4), wherein the perpendicularity required by construction is ensured during the lowering;
(6) adopting a down-the-hole drill to punch a hole in the lower rock stratum, enabling a drill bit of the down-the-hole drill to extend into the positioning sleeve 3, vertically and accurately drilling a hole downwards from the soil-rock junction surface until the designed elevation of rock socketed at the pile tip of the miniature steel pipe pile 6 meets the current standard requirement and the inner lap length of the miniature steel pipe pile 6 and the positioning sleeve 3 is met; the hole diameter of the drill hole is smaller than the inner diameter of the positioning sleeve 3 and larger than the outer diameter of the miniature steel pipe pile 6, so that construction is facilitated; after the construction is finished, blowing out rock debris in the hole drilling and forming process by utilizing high-pressure air generated by a down-the-hole drill;
(7) the method comprises the following steps that a miniature steel pipe pile 6 extends into a positioning sleeve 3 from the top until the pile tip of the miniature steel pipe pile 6 is embedded into a rock stratum to form a designed elevation, the depth of the miniature steel pipe pile 6 embedded into rock is at least 0.2 time of the diameter of the miniature steel pipe pile 6, the depth of the pile tip of the miniature steel pipe pile 6 is at least 1m greater than the excavation depth of a foundation pit, and the concrete parameters need to refer to the current specifications according to the actual engineering conditions; ensuring that the micro steel pipe pile 6 and the positioning sleeve 3 partially meet the inner lap joint length;
(8) after the micro steel pipe pile 6 is placed, ground anchoring components on two sides of the large-diameter cast-in-place pile 1 are assembled, and the ground anchoring components are formed by assembling anchoring angle steel 8, a connecting ring 9, a steel wire rope 10 and a connecting plate 11; the width of the edge of the anchoring angle steel 8 is multiplied by the thickness of the edge of the anchoring angle steel 8 and is 20 multiplied by 4mm, one surface of the connecting plate 11 is in full-welding connection with one end of the anchoring angle steel 8, and the length of the anchoring angle steel 8 is determined according to soil layer conditions and relevant parameters of the large-diameter cast-in-place pile 1 and is not less than 3 m; extruding the non-welding end of the anchoring angle steel 8 into a soil layer at the periphery of the large-diameter cast-in-place pile 1 by mechanical static pressure or hammering through the non-welding surface of the connecting plate 11, and pressing a ground anchoring member into two sides of each large-diameter cast-in-place pile 1; the connecting plate 11 is a square thick-wall steel plate, one surface of the connecting plate is welded with an anchoring angle steel 8, the other surface of the connecting plate is provided with two connecting rings 9 which are generally semicircular, the connecting rings 9 are tightly welded with the connecting plate 11 to meet the requirement of stress strength, and the aperture of each connecting ring 9 is larger than the diameter of the steel wire rope 10; the side length and the thickness of the connecting plate 11 are convenient for mechanical static pressure or hammering, the side length is not less than 30mm, and the thickness is not less than 15 mm;
(9) placing the weight I-steel 7 above the large-diameter cast-in-place pile reinforcement cage 2, wherein the specification (waist height, leg width and waist thickness) of the weight I-steel 7 is 12# (120 x 80 x 5.5mm) or 14# (140 x 80 x 5.5mm), the length of the weight I-steel is three times of the pile diameter of the large-diameter cast-in-place pile 1, the flange end face of one side of the weight I-steel is directly contacted with the top of the large-diameter cast-in-place pile reinforcement cage 2, the two ends of the weight I-steel are aligned with the anchoring positions of the anchoring angle steel 8, then the two ends of the steel wire rope 10 penetrate into the two connecting rings 9 on the connecting plate 11, the weight I-steel 7 is firmly bound with the ground anchoring component, and the two ends of the weight I-steel 7 are bound with the ground anchoring component; the ballast I-shaped steel 7 is matched with a ground anchoring component to obtain a pulling resistance force so as to ensure that the large-diameter cast-in-place pile reinforcement cage 2 and the positioning sleeve 3 do not float upwards in the subsequent pressure grouting process;
(10) a plurality of grouting holes 12 are reserved at the bottom of the miniature steel pipe pile 6, commercial concrete 13 is pumped into the large-diameter cast-in-place pile 1 to complete casting, then a grouting pipe extends into the bottom of the miniature steel pipe pile 6 to perform pressure grouting until the internal grouting of all the miniature steel pipe piles 6 and the positioning sleeve 3 is completed, and the pressure grouting process ensures that the large-diameter cast-in-place pile reinforcement cage 2 and the positioning sleeve 3 do not float upwards;
(11) after the steps are completed, the ground anchoring member comprising the ballast I-steel 7, the anchoring angle steel 8, the connecting ring 9, the steel wire rope 10 and the connecting plate 11 is mechanically pulled out so as to be repeatedly used, and the construction process of improving the rock-socketed depth of the single large-diameter cast-in-place pile 1 is completed.
After the construction of the embodiment is completed, the construction method comprises the steps of filling a large-diameter cast-in-place pile 1, a reinforcement cage 2, a positioning sleeve 3, a fixed reinforcement 4, a binding fixed point 5, a miniature steel pipe pile 6, a ballast I-steel 7, an anchoring angle steel 8, a connecting ring 9, a steel wire rope 10, a connecting plate 11, a grouting hole 12, commercial concrete 13 and cement mortar 14; a steel reinforcement cage 2 is installed on the inner side wall of a large-diameter cast-in-place pile 1, a positioning sleeve 3 is bound and fixed on the inner side wall of the steel reinforcement cage 2 through a fixed steel bar 4, the direct contact point of the positioning sleeve 3 and the fixed steel bar 4 is a binding fixed point 5, a miniature steel pipe pile 6 is lapped in the positioning sleeve 3, a plurality of grouting holes 12 are formed in the bottom of the miniature steel pipe pile 6, the end face of one side flange of a pressure-weighted I-shaped steel 7 is in direct contact with the top of the steel reinforcement cage 2, an anchoring angle steel 8, connecting rings 9, a steel wire rope 10 and a connecting plate 11 form a ground anchoring component, ground anchoring components are arranged at two ends of the pressure-weighted I-shaped steel 7, one side of the connecting plate 11 is in full-weld connection with the end face of one side of the anchoring angle steel 8, two connecting rings 9 are symmetrically welded on the other side, and the steel wire rope 10 passes through the two connecting rings 9 to be bound and fixed with the pressure-weighted I-shaped steel 7; cement mortar 14 is poured into the interior of the body of the miniature steel pipe pile 6, the rock-socketed part of the miniature steel pipe pile 6 is tightly bonded with pore-forming rock through the cement mortar 14, and the inner wall part of the lap joint positioning sleeve 3 of the miniature steel pipe pile 6 is bonded through the cement mortar 14; the outer wall of the positioning sleeve 3 is cast with the large-diameter cast-in-place pile 1 into a whole through commercial concrete 13.
In the embodiment, undescribed parts are referred to according to the current national building pile foundation technical specification JGJ94-2008 and the building foundation pit support technical specification (JGJ120-2012), and undescribed construction steps are preferred according to the current construction method.
Claims (9)
1. A construction method for improving the rock-socketed depth of a large-diameter cast-in-place pile is characterized by comprising the following concrete construction processes:
(1) determining relevant parameters of the large-diameter bored concrete pile and the miniature steel pipe pile according to the requirements of a design drawing, wherein the relevant parameters comprise the hole forming diameters of a soil layer and a rock stratum;
(2) after the construction site is leveled, positioning the pile position of the large-diameter cast-in-place pile, covering a soil layer, manually digging holes, and excavating to the elevation of the soil-rock combination layer; if the geological condition is not good, mechanical pore-forming is adopted;
(3) determining the diameter and the wall thickness of the positioning sleeve and the inner lap joint length of the miniature steel pipe pile and the positioning sleeve according to the diameter and the length of the miniature steel pipe pile;
(4) binding a steel reinforcement cage according to the designed length and the pile diameter of the large-diameter cast-in-place pile, vertically aligning a positioning sleeve with a preset position at the bottom of the inner wall of the steel reinforcement cage, binding the positioning sleeve on the large-diameter cast-in-place pile steel reinforcement cage by using at least two fixed steel bars, welding the fixed steel bars on stirrups at corresponding positions, enabling the fixed steel bars to be in direct close contact with the positioning sleeve, welding the fixed steel bars with the stirrups of the steel reinforcement cage, enabling the contact points of the positioning sleeve and the fixed steel bars to be binding fixed points, and overlapping a miniature steel pipe pile in each positioning sleeve; the embedded positions of the positioning sleeves are uniformly distributed along the inner wall of the reinforcement cage;
(5) vertically lowering the reinforcement cage provided with the positioning sleeve in the step (4);
(6) adopting a down-the-hole drill to carry out impact hole forming on a lower rock stratum, enabling a drill bit of the down-the-hole drill to extend into a positioning sleeve, carrying out vertical accurate downward drilling from a soil-rock junction surface, drilling to a designed elevation of rock embedding at the pile tip of the miniature steel pipe pile, and blowing out rock debris in hole forming of the drilled hole by utilizing high-pressure air generated by the down-the-hole drill after construction is finished;
(7) the miniature steel pipe pile extends into the positioning sleeve from the top until the pile tip of the miniature steel pipe pile is embedded into a rock stratum designed elevation;
(8) after the micro steel pipe pile is placed down, ground anchoring components on two sides of the large-diameter cast-in-place pile are assembled, and the ground anchoring components are formed by assembling anchoring angle steel, connecting rings, steel wire ropes and connecting plates; one surface of the connecting plate is in full-welding connection with one end of the anchoring angle steel, the non-welding end of the anchoring angle steel is squeezed into a soil layer on the periphery of the large-diameter cast-in-place pile through the non-welding surface of the connecting plate by using mechanical static pressure or hammering, and a ground anchoring member is pressed into two sides of each large-diameter cast-in-place pile; one surface of the connecting plate is welded with anchoring angle steel, and the other surface is provided with two connecting rings which are tightly welded with the connecting plate;
(9) placing the weight I-shaped steel above the large-diameter cast-in-place pile steel reinforcement cage, wherein the end face of one side flange of the weight I-shaped steel is in direct contact with the top of the large-diameter cast-in-place pile steel reinforcement cage, two ends of the weight I-shaped steel are aligned with anchoring positions of anchoring angle steel, two ends of a steel wire rope penetrate through two connecting rings on a connecting plate, the weight I-shaped steel is firmly bound with a ground anchoring component, and two ends of the weight I-shaped steel are bound with the ground anchoring component; the weighting I-steel is matched with a ground anchoring member to obtain a pulling resistance force so as to ensure that the large-diameter cast-in-place pile reinforcement cage and the positioning sleeve do not float upwards in the subsequent pressure grouting process;
(10) a plurality of grouting holes are reserved at the bottom of the miniature steel pipe pile, commercial concrete is pumped into the large-diameter cast-in-place pile to complete casting, then a grouting pipe extends into the bottom of the miniature steel pipe pile to perform pressure grouting until the internal grouting of all the miniature steel pipe piles and the positioning sleeve is completed, and the pressure grouting process ensures that a reinforcement cage and the positioning sleeve of the large-diameter cast-in-place pile do not float upwards;
(11) after the steps are completed, the ballasting I-steel and the ground anchoring member are mechanically pulled out so as to be reused, and the construction process of improving the rock-socketed depth of the single large-diameter cast-in-place pile is completed.
2. The construction method for improving the rock-socketed depth of the large-diameter cast-in-place pile as claimed in claim 1, wherein the aperture of the hole formed by the large-diameter cast-in-place pile is larger than the diameter of the large-diameter cast-in-place pile, and the length and diameter of the large-diameter cast-in-place pile are designed according to the formation conditions and the supporting requirements.
3. The construction method for improving the rock-socketed depth of the large-diameter cast-in-place pile as claimed in claim 1, wherein the inner diameter of the positioning sleeve is larger than the outer diameter of the pile body of the micro steel pipe pile, and the length of the positioning sleeve is not smaller than the length of the pile body of the large-diameter cast-in-place pile.
4. The construction method for improving the rock-socketed depth of the large-diameter cast-in-place pile as claimed in claim 1, wherein the number of the binding fixing points is not less than two, and the distance between adjacent binding fixing points is not more than 1.5 m.
5. The construction method for improving the rock-socketed depth of the large-diameter cast-in-place pile according to claim 1, wherein the pile body length of the miniature steel pipe pile meets the rock-socketed depth required by current specifications, and the length of the lap joint of the miniature steel pipe pile and the inner wall of the positioning sleeve is not less than 3 times of the diameter of the large-diameter cast-in-place pile; the depth of the pile tip of the miniature steel pipe pile is at least 1.0m greater than the excavation depth of the foundation pit.
6. The construction method for improving the rock-socketed depth of the large-diameter cast-in-place pile according to claim 1, wherein the reinforcement cage is bound and fixed with a plurality of positioning sleeves according to the designed pile diameter of the large-diameter cast-in-place pile, and when the designed pile diameter of the large-diameter cast-in-place pile is 800mm, three positioning sleeves are arranged; when the pile diameter is designed to be 1200-1400 mm, arranging four positioning sleeves; when the diameter of the pile is larger than 1400mm, five or six positioning sleeves are arranged, one miniature steel pipe pile is lapped in each positioning sleeve, and the fixing position is installed according to the design embedded position of the miniature steel pipe pile.
7. The construction method for improving the rock-socketed depth of the large-diameter bored pile according to claim 1, wherein the hole is formed by a down-the-hole drill in a manner that the micro steel pipe pile is embedded in a rock stratum.
8. The construction method for improving the rock-socketed depth of the large-diameter cast-in-place pile according to claim 1, wherein the length of the ballast I-steel is 3 times of the diameter of the large-diameter cast-in-place pile.
9. The construction method for improving the depth of socketed rock of the large-diameter cast-in-place pile as claimed in claim 1, wherein the width of the edge of the anchoring angle steel is 20 x 4mm, the thickness of the edge is not less than 3 m; the connecting plate is a square thick-wall steel plate, the side length is not less than 30mm, the wall thickness is not less than 15mm, and the side length is greater than the width of the anchoring angle steel; the connecting ring is a circular ring or a semicircular ring, and the aperture of the connecting ring is larger than the diameter of the steel wire rope.
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