CN114875886B - Construction method of expanded diameter vibroflotation gravel pile - Google Patents
Construction method of expanded diameter vibroflotation gravel pile Download PDFInfo
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- 238000010276 construction Methods 0.000 title claims abstract description 34
- 239000004575 stone Substances 0.000 claims abstract description 47
- 239000002893 slag Substances 0.000 claims abstract description 44
- 239000007921 spray Substances 0.000 claims abstract description 38
- 238000004140 cleaning Methods 0.000 claims abstract description 4
- 230000001681 protective effect Effects 0.000 claims description 16
- 238000000034 method Methods 0.000 claims description 14
- 229910000831 Steel Inorganic materials 0.000 claims description 11
- 239000010959 steel Substances 0.000 claims description 11
- 239000000463 material Substances 0.000 claims description 9
- 239000002351 wastewater Substances 0.000 claims description 9
- 230000003014 reinforcing effect Effects 0.000 claims description 5
- 239000004744 fabric Substances 0.000 claims description 3
- 238000002347 injection Methods 0.000 claims description 3
- 239000007924 injection Substances 0.000 claims description 3
- 230000000149 penetrating effect Effects 0.000 claims description 2
- 238000003825 pressing Methods 0.000 claims 1
- 230000002787 reinforcement Effects 0.000 abstract description 4
- 239000004927 clay Substances 0.000 abstract description 3
- 239000000945 filler Substances 0.000 abstract description 3
- 210000003205 muscle Anatomy 0.000 description 10
- 230000000694 effects Effects 0.000 description 8
- 230000009471 action Effects 0.000 description 7
- 230000003993 interaction Effects 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 3
- 238000005056 compaction Methods 0.000 description 3
- 230000007774 longterm Effects 0.000 description 3
- 238000009412 basement excavation Methods 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 239000002689 soil Substances 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000001125 extrusion Methods 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000012856 packing Methods 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000013049 sediment Substances 0.000 description 1
- 238000004062 sedimentation Methods 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- 238000012876 topography Methods 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
- E02D3/00—Improving or preserving soil or rock, e.g. preserving permafrost soil
- E02D3/02—Improving by compacting
- E02D3/08—Improving by compacting by inserting stones or lost bodies, e.g. compaction piles
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D13/00—Accessories for placing or removing piles or bulkheads, e.g. noise attenuating chambers
- E02D13/08—Removing obstacles
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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
- E02D5/66—Mould-pipes or other moulds
- E02D5/68—Mould-pipes or other moulds for making bulkheads or elements thereof
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B27/00—Containers for collecting or depositing substances in boreholes or wells, e.g. bailers, baskets or buckets for collecting mud or sand; Drill bits with means for collecting substances, e.g. valve drill bits
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B7/00—Special methods or apparatus for drilling
- E21B7/18—Drilling by liquid or gas jets, with or without entrained pellets
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B7/00—Special methods or apparatus for drilling
- E21B7/20—Driving or forcing casings or pipes into boreholes, e.g. sinking; Simultaneously drilling and casing boreholes
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B7/00—Special methods or apparatus for drilling
- E21B7/28—Enlarging drilled holes, e.g. by counterboring
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- Life Sciences & Earth Sciences (AREA)
- Mining & Mineral Resources (AREA)
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- General Life Sciences & Earth Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- Structural Engineering (AREA)
- Fluid Mechanics (AREA)
- Physics & Mathematics (AREA)
- Geochemistry & Mineralogy (AREA)
- General Engineering & Computer Science (AREA)
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- Soil Sciences (AREA)
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Abstract
The invention discloses an expanded diameter vibroflotation gravel pile and a construction method thereof, which relate to the field of pile foundation engineering and solve the problems that the existing construction method is easy to collapse holes, filler is easy to be polluted and the pile forming quality is influenced, and the adopted technical scheme is as follows: the pile casing is perforated for standby; digging a pile hole, and lowering a pile casing to protect the pile hole; filling broken stone into the pile hole after hole cleaning is completed, lifting the pile casing, enabling the lower end of the pile casing to be located at the top surface of the broken stone, hammering and compacting the broken stone until the pile expanding hole of the pile casing is located at the reaming position; hanging a slag collecting barrel to the top surface of broken stone in a pile hole, hanging a spray head fixing device in the pile hole, and performing reaming construction; taking out the drain pipe, the spray head fixing device and the slag collecting barrel from the pile hole, filling broken stone into the pile hole to the upper edge of the pile expanding hole, lifting the pile casing until the lower end of the pile casing is positioned on the top surface of the broken stone, and hammering and compacting the broken stone; repeating the steps until the construction of the whole expanded-diameter vibroflotation gravel pile is completed. The invention is used for the foundation reinforcement treatment of soft clay, loam and silt.
Description
Technical Field
The invention relates to the field of pile foundation engineering, in particular to a construction method of an expanded-diameter vibroflotation gravel pile.
Background
Alluvial plain is a plain topography formed by river deposition. The stratum of alluvial plain distributes a large amount of clay and silt soil stratum, and has poor geology problems such as insufficient bearing capacity, large sedimentation, liquefaction and the like. For the stratum of the alluvial plain, the main foundation treatment methods include a replacement method, a dynamic compaction method and a vibroflotation gravel pile method, wherein the vibroflotation gravel pile method has the best effect.
The traditional vibroflotation gravel pile is cylindrical, has poor combination with stratum, and has overall stability and shear strength to be enhanced. In order to improve the combination interaction degree of the vibroflotation gravel pile and the stratum, the side wall of a pile hole of the vibroflotation gravel pile is extruded to form a branch hole or a disk-shaped slotted hole, and a composite foundation with branches or disk-shaped protrusions is formed after filling materials are added. The method is used for extruding the side wall of the pile hole to form a hole, the aperture and the hole depth obtained by extrusion are generally smaller, and meanwhile, the hole wall is disturbed in the process of hammering and compacting the filler. On one hand, because the side wall of the pile hole is not provided with protective measures, the hole collapse is easy to occur, and on the other hand, the loose block on the side wall of the pile hole is fallen off due to hammering vibration, so that the packing is polluted, and the pile forming quality is influenced.
Disclosure of Invention
The invention firstly provides a construction method of an expanded-diameter vibroflotation gravel pile, which solves the problems that the existing construction method is easy to collapse holes and the filler is easy to be polluted, thereby influencing pile forming quality.
The technical scheme adopted by the invention is as follows: the construction method of the expanded-diameter vibroflotation gravel pile comprises the following steps:
s1, perforating a pile casing for standby: at least two pile-expanding holes are formed in the side wall of the pile casing and close to the lower end in the circumferential direction, and the distances from the geometric center of each pile-expanding hole to the corresponding plane of the lower end of the pile casing are equal.
Further is: the pile casing is a steel pile casing, and reinforcing ribs are further arranged at the positions where pile expansion holes are formed in the pile casing.
Further is: the number of pile-expanding holes is 2-6, the pile-expanding holes are identical in shape and size, and the geometric centers of the pile-expanding holes are arranged at equal central angles relative to the axis of the pile casing.
For example: the pile-expanding hole is a hole obtained by cutting according to a circle, the diameter of the circle is 0.2-0.4 m, and the distance between the lowest part of the pile-expanding hole and the corresponding plane of the lower end of the pile casing is 0.4-0.6 m.
S2, excavating a pile hole, and lowering a pile casing to protect the pile hole until the design depth is reached. For example: the diameter of the pile hole is 60-100 cm, and the design depth of the pile hole is within 15.0 m. The pile hole is excavated by adopting the existing excavation method, for example, a water jet method can be adopted.
S3, filling broken stone into the pile hole after hole cleaning is completed, lifting the pile casing, enabling the lower end of the pile casing to be located at the top surface of the broken stone, hammering the broken stone tightly until the pile hole of the pile casing is located at the reaming position. Wherein, the distance between the first reaming position and the pile bottom is generally 2.0-3.0 m.
Further is: in the step S3, graded broken stone is filled into the pile hole, then the pile casing is lifted up, the lower end of the pile casing is positioned at the top surface of the graded broken stone, the graded broken stone is hammered tightly, and the operation is repeated until the pile hole of the pile casing is positioned at the reaming position. For example: the single filling thickness of the graded broken stone is 0.3-0.5 m.
S4, hanging the slag collecting barrel to the top surface of the broken stone in the pile hole. The slag collecting barrel comprises a cylindrical barrel body, the height of the barrel body is not larger than the distance from the bottom of the pile expanding hole to the corresponding plane of the lower end of the pile casing, the outer diameter of the barrel body is matched with the inner diameter of the pile casing, and the lower end of the barrel body is in a closed shape.
Further is: the barrel of album sediment bucket is the elasticity outer lane, and the lower extreme of elasticity outer lane is sealed through flexible waterproof material, and at least two-layer spoke is connected to the inboard of elasticity outer lane, and the spoke of every layer all links to each other with same slip ring, and each spoke both ends all rotatable coupling in elasticity outer lane and slip ring, and each slip ring all is located the central axis department of elasticity outer lane, wears to establish the push rod in the slip ring.
For example, the elastic outer ring is made of rubber, the flexible waterproof material is waterproof cloth, the spokes are steel spokes, and the sliding ring is a steel ring.
In the step S4, the slag collecting barrel is firstly hung to the top of broken stone in the pile hole through the push rod, the upper end of the push rod is positioned outside the pile hole, and then the push rod is pressed down, so that the spokes are spread and kept in a spread state, and the elastic outer ring is tightly attached to the inner wall of the pile casing.
S5, hanging the nozzle fixing device into the pile hole.
Hanging a spray head fixing device provided with spray heads into the pile holes through vertical rods, wherein the upper ends of the vertical rods are positioned outside the pile holes, and the spray directions of the spray heads are opposite to the geometric centers of the pile expansion holes respectively; wherein, shower nozzle fixing device includes the montant, and the lower extreme of montant sets up the mounting bracket, each shower nozzle of fixed mounting on the mounting bracket.
Further is: the diameter of the round shape surrounded by the injection end of the nozzle is consistent with the inner diameter of the protective cylinder.
S6, reaming construction is carried out.
And placing a drain pipe into the slag collecting barrel, fixing a spray head fixing device, performing reaming construction on the pile hole through a spray head until the pile hole is reamed to a designed depth, and discharging slag-containing wastewater into the slag collecting barrel and out of the pile hole through the drain pipe.
S7, taking the drain pipe, the spray head fixing device provided with the spray head and the slag collecting barrel out of the pile hole, filling broken stone into the pile hole to the upper edge of the pile expanding hole, lifting the pile casing until the lower end of the pile casing is positioned on the top surface of the broken stone, and hammering and compacting the broken stone.
And S8, repeating the steps S4 to S7 until the construction of the whole expanded-diameter vibroflotation gravel pile is completed.
The construction method of the expanded-diameter vibroflotation gravel pile has the beneficial effects that: the side wall of the pile casing and the position close to the lower end are provided with pile holes, the stratum outside the pile holes is subjected to water injection reaming through the spray head, the pile holes with expanded diameters are formed, and the holes are not easy to collapse due to the protection effect of the pile casing. Slag-containing wastewater generated by water jet reaming is collected through a slag collecting barrel and discharged outside through a drain pipe, so that the phenomenon that the slag-containing wastewater is precipitated in pile holes to influence pile forming quality is avoided.
The barrel body of the slag collecting barrel is an elastic outer ring, the lower end of the elastic outer ring is sealed by a flexible waterproof material, the elastic outer ring is tightly attached to the inner wall of the pile casing, and slag-containing waste water is prevented from precipitating in the pile hole to the greatest extent.
The invention also provides an expanded diameter type vibroflotation gravel pile, which can be obtained by the construction method of the expanded diameter type vibroflotation gravel pile, and aims to enlarge the contact surface of the vibroflotation gravel pile and a foundation, enhance the combination interaction degree of the vibroflotation gravel pile and the foundation, improve the stress of the vibroflotation gravel pile and improve the foundation reinforcement effect. The expanded diameter vibroflotation gravel pile comprises vertically arranged pile bodies, wherein each pile body comprises at least one section of expanded diameter section, at least two protruding bodies are arranged around each expanded diameter section, and the intersection point of action lines perpendicular to the outer contours of the protruding bodies is located in the range of the pile body.
Specific: the outer contour of the protruding body is hemispherical or semi-ellipsoidal. For example, the connection part of the protruding body and the pile body is round, and the diameter is 0.2-0.4 m.
Further is: the heights of the opposite pile body lower ends of the protruding bodies on the same expansion section are equal. Further, it is: the geometric centers of the convex bodies are arranged at equal central angles relative to the axis of the pile body.
Specific: the shape and the size of each protruding body are the same.
Specific: the diameter of the non-expanded section of the pile body is 60-100 cm, and the height of the pile body is within 15.0 m.
Specific: the distance between the lower edge of the protruding body at the bottommost part of the pile body and the pile bottom is 2.0-3.0 m.
Specific: the number of the convex bodies of the same expansion section is 2-6.
The expanded-diameter vibroflotation gravel pile has the beneficial effects that: the expanding section of the expanding-diameter vibroflotation gravel pile is provided with the protruding body, so that the contact area between the vibroflotation gravel pile and the stratum is enlarged, and the combination interaction degree of the vibroflotation gravel pile and the stratum is enhanced. The intersection point of the action lines perpendicular to the outer contour of the bulge is positioned in the range of the pile body, namely the intersection point of the external force applied to the bulge is positioned in the range of the pile body, which is equivalent to the compaction effect on the pile body, is beneficial to the long-term stability of the pile body, and improves the bearing capacity of the vibroflotation gravel pile. The outer contour of the protruding body is hemispherical or semi-ellipsoidal, so that the construction of the pile body is facilitated.
Drawings
Fig. 1 is a schematic view of a construction method of an expanded diameter vibroflotation gravel pile according to the present invention.
Fig. 2 is a schematic view of the lower end of the casing of fig. 1.
Fig. 3 is a schematic structural view of the slag collecting bucket of fig. 1.
Fig. 4 is a schematic structural view of a nozzle fixing device in the construction method of the expanded diameter vibroflotation gravel pile of the present invention.
Figure 5 is a schematic representation of a cross-section of an expanded diameter vibroflotation gravel pile of the present invention along the geometric center of the protrusion.
Fig. 6 and 7 are schematic views of the forces of two different expanded diameter vibroflotation gravel piles in the expanded diameter section.
Reference numerals: pile casing 1, pile expanding hole 11, slag collecting barrel 2, elastic outer ring 21, flexible waterproof material 22, spoke 23, sliding ring 24, push rod 25, nozzle fixing device 3, vertical rod 31, mounting frame 32, pile body 4 and protruding body 41.
Detailed Description
The expanded diameter vibroflotation gravel pile and the construction method thereof are suitable for the foundation reinforcement treatment of soft clay, loam and silt with the depth of 15m or less, and the pile diameter of a non-expanded diameter section is generally 60-100 cm. The invention is further described below with reference to the accompanying drawings.
Referring to fig. 1, the construction method of the expanded diameter vibroflotation gravel pile of the invention comprises the following steps:
s1, perforating the pile casing 1 for standby.
At least two pile-expanding holes 11 are formed in the side wall of the pile casing 1 and near the lower end in the circumferential direction, and the pile-expanding holes 11 are used for expanding the vibroflotation gravel pile. The pile casing 1 is usually made of steel, and the pile hole 11 can be opened by cutting. The pile enlarging holes 11 can be through holes with any polygon or round shape, preferably the pile enlarging holes 11 are formed according to the round shape, and the pile enlarging holes 11 are identical in shape and size. For example, the pile hole 11 is a hole cut in a circular shape, and the diameter of the circular shape is 0.2 to 0.4m.
The number of pile-expanding holes 11 is at least two, for example, 2 to 6. In order to facilitate the stress balance of reaming construction and improve the stress of the pile body, the pile-enlarging holes 11 are identical in shape and size, and the distances from the geometric centers of the pile-enlarging holes 11 to the corresponding plane at the lower end of the pile casing 1 are equal. For example, the distance between the lowest part of the pile hole 11 and the corresponding plane of the lower end of the pile casing 1 is 0.4-0.6 m. Wherein, the corresponding plane of the lower end of the protective barrel 1 is vertical to the axis of the protective barrel 1. In the embodiment shown in fig. 1 and 2, the pile-enlarging holes 11 are provided with 3 pile-enlarging holes 11 which are identical in shape and size, and the three pile-enlarging holes 11 are all cut and perforated in a circular shape.
In order to supplement the strength reduction caused by the hole opening at the lower end of the pile casing 1, the pile casing 1 is provided with a pile expansion hole 11 and a reinforcing rib. The strengthening rib sets up around expanding stake hole 11, and for example the strengthening rib includes ring muscle and straight muscle, expands stake hole 11 upper and lower part and sets up a ring muscle respectively, and the ring muscle is circular and the plane that the ring muscle is located is perpendicular with the axis of pile casing 1, links to each other through straight muscle between the ring muscle, welded connection between ring muscle and the straight muscle, sets up at least one straight muscle between two adjacent expanding stake holes 11, as shown in fig. 2. The reinforcing ribs are arranged in the pile expansion holes 11 and play a role in increasing the strength of the pile casing 1. The reinforcing ribs can be steel bars and are welded and fixed on the protective cylinder 1. The ribs are preferably fixed to the inside of the casing 1 to avoid affecting the sinking and lifting of the casing in the hole.
S2, excavating a pile hole, and lowering a pile casing 1 to protect the pile hole until the design depth is reached. For example, pile hole excavation is performed by adopting a water jet method, a vibroflotation device is aligned with a pile position, a hoist of a construction vehicle or a crane is started, and a vibrator is sunk in a soil layer at a speed of 1-2 m/min. As the pile hole depth increases, the pile hole side wall is protected by lowering the casing 1 until the designed depth is reached. The diameter of the pile hole can be 60-100 cm, and the design depth of the pile hole is within 15.0 m.
S3, filling broken stone into the pile hole after hole cleaning is completed, lifting the pile casing 1, enabling the lower end of the pile casing 1 to be located at the top surface of the broken stone, hammering the broken stone to be compact, and enabling the pile hole 11 of the pile casing 1 to be located at the reaming position.
The step can be completed once or multiple times, and is determined by the distance between the diameter expansion section at the lowest position and the pile bottom. Wherein, the distance between the first reaming position and the pile bottom is generally 2.0-3.0 m. Specifically, after the hole is cleared, gravels are filled into the pile hole, and then the protective cylinder 1 is lifted up, so that the lower end of the protective cylinder 1 is positioned at the top surface of the gravels, namely the lifting degree of the protective cylinder 1 is consistent with the filling thickness of the gravels; filling the broken stone, and lifting the protective cylinder 1 until the lower end of the protective cylinder 1 is positioned at the top surface of the broken stone; finally, the operation is repeated until the pile hole 11 of the casing 1 is located at the reaming position. In order to control the compactness, the single filling thickness of the crushed stone is 0.3-0.5 m, and the crushed stone is graded crushed stone.
S4, hanging the slag collecting barrel 2 to the top surface of the broken stone in the pile hole.
The slag collecting barrel 2 is used for being placed at the bottom of the pile casing 1 to collect slag-containing wastewater generated by reaming. The slag collecting barrel 2 comprises a cylindrical barrel body, the height of the barrel body is not larger than the distance from the bottom of the pile expansion hole 11 to the corresponding plane of the lower end of the pile casing 1, and slag-containing wastewater can flow into the slag collecting barrel 2. The outer diameter of the cylinder body is matched with the inner diameter of the protective cylinder 1, and the lower end of the cylinder body is in a closed shape, so that slag-containing wastewater is prevented from leaking downwards from a gap between the outer side of the slag collecting barrel 2 and the inner wall of the protective cylinder 1 as much as possible, and the slag collecting barrel 2 is ensured to be smoothly placed in the bottom of the protective cylinder 1 and taken out from the interior of the protective cylinder 1.
A preferred solution for the slag collection bath 2 is given below. As shown in fig. 3, the barrel body of the slag collecting barrel 2 is an elastic outer ring 21, the elastic outer ring 21 is preferably made of rubber, the lower end of the elastic outer ring 21 is closed by a flexible waterproof material 22, and for example, the flexible waterproof material 22 is waterproof cloth. At least two layers of spokes 23 are provided on the inside of the resilient outer ring 21, such as two layers of spokes 23 in the embodiment shown in fig. 2. The connecting positions of each layer of spokes 23 on the elastic outer ring 21 are equal in height, at least three spokes 23 on each layer are arranged, each spoke 23 can be a steel spoke, the length of each spoke 23 is equal, two ends of each spoke 23 are rotatably connected with the elastic outer ring 21 and the sliding ring 24, the sliding ring 24 is preferably a steel ring, each spoke 23 on each layer is connected with the same sliding ring 24, and each sliding ring 24 is located at the central axis of the elastic outer ring 21. A push rod 25 is arranged in the sliding ring 24 in a penetrating way, and the push rod 25 is preferably fixedly connected with the sliding ring 24. The slag collecting barrel 2 is lifted up through the push rod 25, under the dead weight effect of the slag collecting barrel 2, the spokes 23 are folded relatively to a certain extent, the elastic outer ring 21 is in a contracted and extruded state, the diameter of the slag collecting barrel 2 is smaller than the inner diameter of the pile casing 1, and the slag collecting barrel 2 can be lifted to the top of broken stone in a pile hole through the push rod 25. The length of the push rod 25 is not lower than the depth of the pile hole, so that the upper end of the push rod 25 is always positioned outside the pile hole, and the slag collecting barrel 2 is convenient to operate. After the slag collecting barrel 2 is hung at the bottom of the pile hole, the push rod 25 is pressed down, the spokes 23 are spread and maintain the spread state, and the elastic outer ring 21 is tightly attached to the inner wall of the pile casing 1. When the push rod 25 is pressed down, the spokes 23 prop open the elastic outer ring 21, so that the elastic outer ring 21 is tightly attached to the inner wall of the casing 1. The spokes 23 can be kept in a spread state relative to the fixed push rod 25, and the elastic outer ring 21 is kept in a state of being clung to the inner wall of the casing 1; or, after the sliding ring 24 is pressed down to a certain degree, the spokes 23 are self-locked, the spokes 23 automatically maintain the open state, the sliding ring 24 is lifted up by the push rod 25, the self-locking function of the sliding ring 24 is disabled, and the spokes 23 are folded.
S5, hanging the nozzle fixing device 3 into the pile hole.
The nozzle fixing device 3 is used for installing a nozzle and assisting in reaming. As shown in fig. 4, the spray head fixing device 3 comprises a vertical rod 31, a mounting frame 32 is arranged at the lower end of the vertical rod 31, and each spray head is fixedly mounted on the mounting frame 32. The stem 31 and the mounting bracket 32 are preferably not of metal, such as steel. The length of the vertical rod 31 should be sufficient to perform reaming outside the pile hole. Each spray head on the mounting frame 32 is respectively in one-to-one correspondence with the pile expansion holes 11 at the lower end of the pile casing 1. The diameter of the circle defined by the spray ends of the individual spray heads preferably corresponds to the inner diameter of the casing 1.
The spray head fixing device 3 is hung in the pile hole, the spray head fixing device 3 provided with spray heads is firstly hung in the pile hole through the vertical rods 31, the upper ends of the vertical rods 31 are positioned outside the pile hole, and the spray directions of the spray heads are respectively opposite to the geometric centers of the pile expansion holes 11.
S6, reaming construction is carried out.
Placing a drain pipe into the slag collecting barrel 2, fixing a spray head fixing device 3, ensuring that the spray directions of all spray heads are respectively opposite to the geometric centers of all pile enlarging holes 11 and are relatively fixed, and carrying out reaming construction on the pile enlarging holes 11 through the spray heads until the depth reaches the design depth, wherein slag-containing wastewater enters the slag collecting barrel 2 and is discharged out of the pile holes through the drain pipe.
S7, taking the drain pipe, the spray head fixing device 3 provided with the spray head and the slag collecting barrel 2 out of the pile hole, and filling broken stone into the pile hole, wherein the broken stone is preferably graded broken stone, can be filled in at one time, and can be filled in a plurality of times and be compacted by preliminary hammering. After the broken stone is filled to the upper edge of the pile expansion hole 11, the pile casing 1 is lifted until the lower end of the pile casing 1 is positioned on the top surface of the broken stone, and the broken stone is hammered tightly.
And S8, repeating the steps S4 to S7 until the construction of the whole expanded-diameter vibroflotation gravel pile is completed.
The invention also provides an expanded diameter type vibroflotation gravel pile, which can be obtained by the construction method of the expanded diameter type vibroflotation gravel pile. Referring to fig. 5, the expanded-diameter vibroflotation gravel pile comprises a pile body 4 vertically arranged, the pile body 4 comprises at least one expanded-diameter section, at least two protruding bodies 41 are arranged around the expanded-diameter section, the number of protruding bodies 41 of the same expanded-diameter section is 2-6, for example, in the embodiment shown in fig. 5, the number of protruding bodies 41 is 3. The protrusions 41 are preferably identical in shape and size. The shape of the portion where the protruding body 41 is connected to the pile body 4 is the same as the shape of the pile hole 11, and for example, the protruding body is substantially circular, and the diameter of the circular shape is 0.2 to 0.4m. The heights of the opposite lower ends of the pile bodies 4 of the protrusions 41 on the same expanded diameter section are preferably equal, that is, the heights of the protrusions 41 on the expanded diameter section are preferably uniform. The geometric centers of the projections 41 on the same expanded section are preferably arranged at an isocentric angle with respect to the axis of the pile body 4, i.e. the projections 41 are preferably evenly distributed around the expanded section. The diameter of the non-expanded section of the pile body 4 is 60-100 cm, and the height of the pile body 4 is within 15.0 m. The distance between the lower edge of the protruding body 41 at the bottommost part of the pile body 4 and the pile bottom is generally 2.0-3.0 m.
The outer contour of the protrusion 41 is: the intersection point of the action lines perpendicular to the outer contour of the protrusion 41 is located within the range of the pile body 4. For example, the outer contour of the protrusion 41 is hemispherical or semi-ellipsoidal. The action lines perpendicular to the outer contour of the protruding body 41 have intersection points, that is, the intersection points exist when the external force is applied to the protruding body 41, the intersection points are located in the range of the pile body 4, the external force applied to the protruding body 41 is concentrated in the range of the pile body 4, which is equivalent to forming compaction action on the pile body 4, and the long-term stability of the pile body 4 is facilitated, as shown in fig. 6. As a comparative example, referring to fig. 7, the diameter-expanding section of the pile body is disposed on a branch or a disc-shaped protrusion having a triangular longitudinal section, and from the perspective of stress, the composite foundation with the branch and the disc-shaped protrusion has a poor stress state, and has a thin structure, and the line of action of external force applied to the branch and the disc-shaped protrusion is outside the pile body, and because the line of action of external force is not concentrated in the range of the pile body, the branch or the disc-shaped protrusion is easy to deform or destroy, which is unfavorable for long-term stability of the pile body under the stress condition.
The expanded section of the expanded diameter type vibroflotation gravel pile is expanded in a semicircular drum shape, so that the contact surface of the gravel pile and the foundation is enlarged, the combination interaction degree of the gravel pile and the foundation is enhanced, the reinforcement effect is enhanced under the condition that the stress meets the design requirement, and the effect of improving the poor foundation treatment effect of the vibroflotation gravel pile is achieved.
Claims (9)
1. The construction method of the expanded-diameter vibroflotation gravel pile is characterized by comprising the following steps of: the method comprises the following steps:
s1, perforating a protective cylinder (1) for standby: at least two pile expansion holes (11) are formed in the side wall of the pile casing (1) and close to the lower end in the circumferential direction, and the distances from the geometric center of each pile expansion hole (11) to the corresponding plane of the lower end of the pile casing (1) are equal;
s2, excavating a pile hole, and lowering a pile casing (1) to protect the pile hole until the design depth is reached;
s3, filling broken stone into the pile hole after hole cleaning is completed, lifting the pile casing (1), enabling the lower end of the pile casing (1) to be located at the top surface of the broken stone, hammering and compacting the broken stone until a pile expanding hole (11) of the pile casing (1) is located at a reaming position;
s4, hanging the slag collecting barrel (2) to the top surface of broken stone in the pile hole, wherein the slag collecting barrel (2) comprises a cylindrical barrel body, the barrel body is an elastic outer ring (21), the lower end of the elastic outer ring (21) is sealed by a flexible waterproof material (22), at least two layers of spokes (23) are connected to the inner side of the elastic outer ring (21), the spokes (23) of each layer are connected with the same sliding ring (24), the two ends of each spoke (23) are rotatably connected to the elastic outer ring (21) and the sliding rings (24), each sliding ring (24) is positioned at the central axis of the elastic outer ring (21), a push rod (25) is arranged in the sliding ring (24) in a penetrating manner, the height of the barrel body is not greater than the distance from the bottom of the pile expanding hole (11) to the corresponding plane of the lower end of the pile casing (1), the outer diameter of the barrel body is matched with the inner diameter of the pile casing (1), and the lower end of the barrel body is in a sealed shape;
firstly, hanging the slag collecting barrel (2) to the top of broken stone in a pile hole through a push rod (25), pressing the push rod (25) downwards after the upper end of the push rod (25) is positioned outside the pile hole, so that spokes (23) are spread and maintain a spread state, and an elastic outer ring (21) is tightly attached to the inner wall of the pile casing (1);
s5, hanging the spray head fixing device (3) into the pile hole: lifting a spray head fixing device (3) provided with spray heads into pile holes through vertical rods (31), wherein the upper ends of the vertical rods (31) are positioned outside the pile holes, and the spray directions of the spray heads are opposite to the geometric centers of the pile expansion holes (11) respectively; the spray head fixing device (3) comprises a vertical rod (31), a mounting frame (32) is arranged at the lower end of the vertical rod (31), and each spray head is fixedly mounted on the mounting frame (32);
s6, reaming construction: placing a drain pipe into the slag collecting barrel (2), fixing a spray head fixing device (3), reaming the pile hole (11) through a spray head until the pile hole is reamed to a designed depth, and allowing slag-containing wastewater to enter the slag collecting barrel (2) and be discharged out of the pile hole through the drain pipe;
s7, taking the drain pipe, the spray head fixing device (3) provided with the spray head and the slag collecting barrel (2) out of the pile hole, filling broken stone into the pile hole to the upper edge of the pile expanding hole (11), lifting the pile casing (1) until the lower end of the pile casing (1) is positioned on the top surface of the broken stone, and hammering and compacting the broken stone;
and S8, repeating the steps S4 to S7 until the construction of the whole expanded-diameter vibroflotation gravel pile is completed.
2. The construction method of the expanded diameter type vibroflotation gravel pile according to claim 1, which is characterized in that: in the step S1, the pile casing (1) is a steel pile casing, and reinforcing ribs are arranged at positions where pile expansion holes (11) are arranged in the pile casing (1).
3. The construction method of the expanded diameter type vibroflotation gravel pile according to claim 1, which is characterized in that: in the step S1, the number of the pile expansion holes (11) is 2-6, the pile expansion holes (11) are identical in shape and size, and the geometric centers of the pile expansion holes (11) are arranged at an isocenter angle relative to the axis of the pile casing (1).
4. A method of constructing an expanded diameter vibroflotation gravel pile according to claim 3, wherein: in the step S1, the pile expansion hole (11) is a hole obtained by cutting according to a circle, the diameter of the circle is 0.2-0.4 m, and the distance between the lowest part of the pile expansion hole (11) and the corresponding plane of the lower end of the pile casing (1) is 0.4-0.6 m.
5. The construction method of the expanded diameter type vibroflotation gravel pile according to claim 1, which is characterized in that: in the step S2, the diameter of the pile hole is 60-100 cm, and the design depth of the pile hole is within 15.0 m; in the step S3, the distance between the first reaming position and the pile bottom is 2.0-3.0 m.
6. The construction method of the expanded diameter type vibroflotation gravel pile according to claim 1, which is characterized in that: in step S5, the diameter of the circle surrounded by the injection end of the nozzle is consistent with the inner diameter of the protective cylinder (1).
7. A method of constructing an expanded diameter vibroflotation gravel pile according to any one of claims 1 to 6, characterized in that: in the step S3, graded broken stone is filled into the pile hole, then the pile casing (1) is lifted up, the lower end of the pile casing (1) is positioned at the top surface of the graded broken stone, the graded broken stone is hammered tightly, and the operation is repeated until the pile expansion hole (11) of the pile casing (1) is positioned at the reaming position.
8. The construction method of the expanded diameter type vibroflotation gravel pile according to claim 7, characterized in that: the single filling thickness of the graded broken stone is 0.3-0.5 m.
9. A method of constructing an expanded diameter vibroflotation gravel pile according to any one of claims 1 to 6, characterized in that: the elastic outer ring (21) is made of rubber, the flexible waterproof material (22) is waterproof cloth, the spokes (23) are steel spokes, and the sliding ring (24) is a steel ring.
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