CN108570983B - Pile foundation construction method of large karst cave without filler and pile casing thereof - Google Patents
Pile foundation construction method of large karst cave without filler and pile casing thereof Download PDFInfo
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- CN108570983B CN108570983B CN201810359219.9A CN201810359219A CN108570983B CN 108570983 B CN108570983 B CN 108570983B CN 201810359219 A CN201810359219 A CN 201810359219A CN 108570983 B CN108570983 B CN 108570983B
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- 238000010276 construction Methods 0.000 title claims abstract description 31
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 89
- 239000010959 steel Substances 0.000 claims abstract description 89
- 238000005553 drilling Methods 0.000 claims abstract description 25
- 230000002787 reinforcement Effects 0.000 claims abstract description 6
- 238000004140 cleaning Methods 0.000 claims abstract description 5
- 238000000034 method Methods 0.000 claims description 43
- 239000011435 rock Substances 0.000 claims description 24
- 239000002689 soil Substances 0.000 claims description 23
- 239000002002 slurry Substances 0.000 claims description 19
- 239000004927 clay Substances 0.000 claims description 15
- 235000019994 cava Nutrition 0.000 claims description 7
- 230000001681 protective effect Effects 0.000 claims description 7
- 239000004568 cement Substances 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 6
- 239000010454 slate Substances 0.000 claims description 2
- 239000011800 void material Substances 0.000 claims 2
- 238000004519 manufacturing process Methods 0.000 abstract description 4
- 235000017166 Bambusa arundinacea Nutrition 0.000 description 8
- 235000017491 Bambusa tulda Nutrition 0.000 description 8
- 241001330002 Bambuseae Species 0.000 description 8
- 235000015334 Phyllostachys viridis Nutrition 0.000 description 8
- 239000011425 bamboo Substances 0.000 description 8
- 238000009825 accumulation Methods 0.000 description 6
- 238000003466 welding Methods 0.000 description 3
- 239000002390 adhesive tape Substances 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 230000003116 impacting effect Effects 0.000 description 2
- 238000005086 pumping Methods 0.000 description 2
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- 230000009286 beneficial effect Effects 0.000 description 1
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- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012856 packing Methods 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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Classifications
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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
- E02D5/22—Piles
- E02D5/50—Piles comprising both precast concrete portions and concrete portions cast in situ
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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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- 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
- E02D5/665—Mould-pipes or other moulds for making piles
-
- 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
Abstract
The invention discloses a pile foundation construction method of a large karst cave without filler and a pile casing thereof, comprising the following steps: the first step is as follows: prefabricating a multi-section pile casing unit, manufacturing the multi-section pile casing unit by adopting concrete, and embedding a positioning steel pile casing; the second step is that: drilling along the inside of the positioning steel casing to form a hole; the third step: placing a pile casing unit above the hole, and centering the pile casing unit and the positioning steel pile casing to form a bottom pile casing unit; the fourth step: then, a pile casing unit is placed above the pile casing unit at the bottom end, so that the two pile casing units are centered, connected and fixed; the fifth step: the two pile casing units are placed down along the hole, gradually increased upwards and connected with the pile casing units to form a pile casing; and a sixth step: filling filler into the pile casing to make the bottom of the pile casing seamless; the seventh step: and continuously drilling along the inside of the pile casing to a preset depth, cleaning holes, putting down a reinforcement cage, and pouring underwater concrete to form a pile foundation. The invention is not limited by the height and width of the karst cave, has fast construction speed and low cost, and has higher integral strength and rigidity of the pile foundation.
Description
Technical Field
The invention belongs to the technical field of pile foundation construction, and particularly relates to a pile foundation construction method of a large karst cave without filler and a pile casing thereof.
Background
A large number of karst caves with various sizes are distributed in the underground of a strong karst area, and the filling conditions in the karst caves are divided into three types: no filler (empty cavern), full fill, and half fill. In strong karst areas, when drilling (impact) cast-in-place piles are adopted for bridge and building engineering pile foundations, different construction methods are adopted when the pile foundations meet different filling situations and karst caves with different heights under general conditions.
For large karst caves without filler, two construction methods of filling with rubble clay and following with steel casing are generally adopted. As shown in fig. 1 and 2, the pile foundation 2 sequentially passes through upper rock soil 4, a non-filler karst cave 5 and bottom rock soil 6, and as shown in fig. 1, the schematic diagram of the rubble clay filling method is as follows: firstly, a large amount of flaky clay 12 fillers are thrown and filled in the filler-free karst cave 5 to ensure that the whole height range of the filler-free karst cave is filled with the fillers, so that slurry leakage or water leakage cannot occur, then, a punching hammer is adopted to impact holes in the fillers, and finally, underwater concrete is poured to form the pile foundation 2. As shown in fig. 2, the steel casing follow-up method comprises the following steps: and (3) placing a steel casing 11 slightly larger than the diameter of the pile foundation 2 in the non-filler karst cave 5, and pouring underwater concrete into the steel casing 11 to form the pile foundation 2.
The above-mentioned rubble clay filling method requires a large amount of rubbles and clay, and the construction cost is high, and the filling cost increases faster the higher the cavern is, and is difficult to be realized in areas lacking rubbles or clay, and the backfill amount is too large to be realized when the height of the cavern exceeds 5 m. Although the effect of the steel pile casing follow-up method is good, the steel pile casing is made of steel plates, the manufacturing cost is high, the construction operation is complex, the requirement on the full-seam welding quality among the steel pile casings is high, the field seamless welding needs several hours, the consumed time is too long, the rigidity of the pile casing is small, the deformation is easy to generate, and the problems cause that the steel pile casing follow-up method is difficult to popularize and popularize in engineering practice.
Disclosure of Invention
In view of the above problems in the prior art, the present invention aims to provide a pile foundation construction method and pile casing for large karst caves without filler, which is not limited by the height and width of the karst caves, has the advantages of high construction speed, low cost and good overall strength and rigidity of the pile foundation.
In order to achieve the purpose, the invention adopts the technical scheme that:
the pile foundation construction method of large karst cave without filler includes the following steps
The first step is as follows: prefabricating a plurality of sections of pile casing units with different heights, wherein the pile casing units are made of concrete, and steel pile casings are buried in a construction site to be positioned;
the second step is that: drilling holes along surface rock soil inside the positioning steel casing to form holes;
the third step: placing a pile casing unit above the hole, and aligning the pile casing unit with the center line of the positioning steel pile casing to form a bottom pile casing unit;
the fourth step: placing a cylinder protecting unit above the middle-end cylinder protecting unit in the third step to align the central lines of the two cylinder protecting units, and connecting and fixing the two cylinder protecting units;
the fifth step: placing the two sections of the casing units obtained in the fourth step downwards along the hole, gradually increasing the top of the casing units upwards and connecting the casing units, positioning the connecting method and the fourth step, stopping increasing the casing units until the casing units at the bottom end contact the bottom surface of the non-filler karst cave, and forming the casing by all the casing units;
and a sixth step: backfilling the filler into the protective cylinder in the fifth step to ensure that no gap exists between the bottom end of the protective cylinder and the karst cave without the filler;
the seventh step: and continuously drilling along the inside of the pile casing to a preset depth, cleaning holes, putting down a reinforcement cage, and pouring underwater concrete to form a pile foundation.
Preferably, the cavities in the second step are not in communication with the filler-free cavities.
More preferably, in the second step, the drill is stopped and lifted by the drill until the distance between the bottom of the hole and the top surface of the filler-free cavern is 0.5m-1.5 m. Namely, the distance between the bottom of the hole and the top surface of the filling-free karst cave is 0.5m-1.5 m.
Preferably, when the cavity is not communicated with the cavity without the filler, the fifth step is specifically divided into the following three steps:
(a) when the hole is not communicated with the filling-free cavern, lowering the pile casing unit, adding a pile casing unit above the top pile casing unit, repeating the positioning and connecting method with the fourth step until the bottom of the bottom pile casing unit contacts the bottom of the hole, and the top of the top pile casing unit is not lower than the ground;
(b) breaking surface rock soil on the filler-free karst cave along the interior of the pile casing unit until the hole is communicated with the filler-free karst cave;
(c) and (3) lowering a pile casing unit, when the bottom of the bottom pile casing unit is not contacted with the bottom surface of the filler-free karst cave and the bottom of the uppermost pile casing unit is not higher than the ground, adding a pile casing unit above the uppermost pile casing unit, repeating the positioning connection method with the fourth step until the bottom of the bottom pile casing unit is contacted with the bottom surface of the filler-free karst cave and the top of the uppermost pile casing unit is not lower than the ground to form a pile casing.
Preferably, in the above step (b): and (3) impacting the surface rock soil by using a hammer impact for 50-80 cm of small stroke, when the distance from the bottom of the hole to the top surface of the filler-free karst cave is 30-70 cm, pumping out slurry in the hole, breaking the surface rock soil by using 30-50 cm of small stroke, communicating the hole with the filler-free karst cave, and finally lifting the hammer impact from the hole.
The segmented impact hammer impact method can timely pump out the slurry in the hole, so that the bottom surface of the filler-free karst cave below the penetrated hole is basically free of slurry accumulation, and stable placement of a subsequent pile casing is facilitated. If the hole is directly communicated by a drilling machine, the slurry originally positioned in the hole area falls to the bottom surface of the filler-free karst cave below the hole to form slurry accumulation, the accumulation is soft and unstable, and the pile casing can be unstable when placed on the pile casing. In addition, the pumped mud can be used for drilling of the ground rock.
Preferably, the uppermost end of the positioning steel casing in the first step is not lower than 50cm above the ground.
Preferably, the diameter of the hole in the second step is 15-20 cm larger than the diameter of the preset pile foundation.
Preferably, in the third step, two I-shaped steel plates are erected on the top of the positioning steel casing, and the casing unit is placed on the I-shaped steel plates by using a truck crane and is centered with the positioning steel casing. The center lines of the pile casing unit and the positioning steel pile casing are aligned, and the pile casing unit is a bottom pile casing unit, namely a pile casing unit positioned at the bottommost part of the pile casing.
Preferably, after the pile casing unit and the positioning steel pile casing are centered and positioned, in the fifth step, two pile casing units are lifted by using a truck crane, I-shaped steel padded below the bottom pile casing unit is drawn out, the pile casing unit is slowly lowered along the hole, and the central position and the verticality of the pile casing unit are checked at any time in the lowering process. So as to ensure that the central lines of the two sections of casing units are aligned with the central line of the pile foundation.
Preferably, in the fourth step, if a small amount of gaps occur at the connecting parts of the adjacent casing units, a water-stopping adhesive tape can be attached to the gap parts to prevent slurry in the holes from leaking.
And in the process of connecting and fixing the adjacent pile casing units and after the connection and the fixation are finished, the central position and the verticality of the pile casing units need to be checked, and if the deviation between the central line of the pile casing units and the central line of the positioning steel pile casing exceeds a set range, the central position and the verticality are adjusted until the central position and the verticality meet the requirements.
More preferably, the error between the central position of the pile casing unit and the central position of the positioning steel pile casing unit is less than 30mm, and the error of perpendicularity is less than 1%.
Preferably, in the sixth step, the filler backfilled in the casing is a mixture formed by the rubble, the clay and the cement, and the mixture is repeatedly punched by a punch hammer to completely block the gap between the bottom casing unit and the bottom surface of the karst cave.
More preferably, the mass ratio of the slate, the clay and the cement is 10:5: 1.
The truck crane cannot be loosened, and the gap between the bottom of the bottom pile casing unit and the bottom surface of the karst cave must be completely blocked so as to prevent slurry in holes from leaking out when drilling holes in the lower rock soil.
Preferably, in the seventh step, slurry is poured into the pile casing, then drilling is continuously performed along the inside of the pile casing by adopting a conventional drilling method, after drilling to a preset depth, hole cleaning is performed, a reinforcement cage is lowered, and underwater concrete is poured to form the pile foundation.
Preferably, the casing unit is lowered slowly by hammering the top end of the casing unit located at the top with a gasoline hammer if the casing unit encounters an obstacle during lowering.
The pile casing unit is prefabricated in a factory, the quality is strictly controlled during manufacturing, and the dimension error of each part needs to be less than 5 mm.
The protective cylinder for the large-sized karst cave without the filler is characterized by comprising at least two protective cylinder units which are sequentially connected, wherein the protective cylinder units are made of concrete.
Preferably, the casing is internally provided with steel bars, and the concrete mark is higher than C40, so that enough rigidity and strength are ensured to prevent the casing from deforming and cracking in the using process.
Preferably, the inner diameter of the casing unit is equal to the diameter of a preset pile foundation, the wall thickness of the casing unit is 8-10 cm, and the height of each section of the casing unit is 1.5-2.0 m. The wall thickness of the pile casing is 8-10 cm, the thickness of the steel pile casing used in the steel pile casing follow-up method is only 1cm, the rigidity of the pile casing is far greater than that of the steel pile casing, and the construction process cannot generate obvious deformation.
The pile casing still includes connection steel sheet, connection steel sheet is equipped with two, and adjacent pile casing unit adopts connecting bolt and connection steel sheet to connect fixedly.
The heights of the casing units are not completely the same.
And the upper end and/or the lower end of the cylinder wall of the cylinder protection unit are/is uniformly provided with eight bolt holes along the radial direction, and the distance between each bolt hole and the top end or the bottom end of the cylinder protection unit is 5-15 cm.
More preferably, the bolt holes of the casing units positioned at the uppermost end of the casing are arranged 5-15 cm above the bottom of the casing units, the bolt holes of the casing units positioned at the lowermost end of the casing are arranged 5-15 cm below the top of the casing units, and the bolt holes of the other casing units are arranged at positions 5-15 cm away from the top and the bottom respectively.
Protect a unit top and be equipped with sunken mouthful and/or the bottom is equipped with the bulge mouth with sunken mouthful matched with, adjacent protect a unit and pass through sunken mouthful and bulge mouthful clamping location.
Preferably, the bottom that is located the section of thick bamboo unit that protects of protecting a section of thick bamboo the top is equipped with protruding export, and all the other section of thick bamboo units that protect are the top and are equipped with sunken mouthful, and the bottom is equipped with protruding export, and the design is convenient for adjacent the connection location between a section of thick bamboo unit.
Preferably, three semicircular steel bar hanging rings are uniformly embedded on the inner wall of each pile casing unit at a distance of 15-25 cm from the top end along the radial direction.
Preferably, the connecting bolt is made of high-strength steel and comprises a countersunk head, a screw and a nut, the length of the connecting bolt is 15-17 cm, and the diameter of the connecting bolt is 25-28 mm.
Preferably, the connecting steel plate is made of high-strength steel, the length of the connecting steel plate is 26cm, the width of the connecting steel plate is 6cm, and round holes with the diameter of 28-30 mm are formed in the two ends of the connecting steel plate.
The connecting bolt and the connecting steel plate are made of high-strength steel, so that deformation and fracture cannot occur in the process of lowering the casing protecting unit.
Compared with the prior art, the invention has the beneficial effects that: the method is not limited by the height and width of the karst cave, and when the karst cave is larger, the economic applicability of the method is far better than that of a rubble clay filling method; the pile casing not only can be used as a component of the pile foundation to improve the integral strength and rigidity of the pile foundation, but also can not expand and shrink when underwater concrete is poured in the pile casing, so that the quantity and quality of the concrete can be easily controlled and ensured; other welding equipment is not needed, the construction speed is high, and the cost is low; the pile casings are prefabricated in batches in a factory, the construction quality is easy to guarantee, and the price of the pile casings is only 1/3-1/5 of the price of steel pile casings of the same specification.
Drawings
FIG. 1 is a schematic illustration of a platelet clay packing process;
FIG. 2 is a schematic illustration of a steel casing follow-up process;
FIG. 3 is a schematic view of a pile foundation construction scheme of the present invention;
FIG. 4 is a schematic view of the connection of the casing unit of the present invention;
FIG. 5 is a top view of the casing unit of the present invention;
FIG. 6 is a pictorial view of a connecting bolt of the present invention;
FIG. 7 is a schematic view of a connecting steel plate according to the present invention.
Reference numerals
1. The method comprises the following steps of pile casing, 2, pile foundation, 3, positioning steel casing, 4, surface rock soil, 5, no-filler karst cave, 6, bottom rock soil, 7, connecting bolts, 8, connecting steel plate, 9, bolt holes, 10, hanging rings, 11, steel casing, 12 and flaky clay.
Detailed Description
The construction method of pile foundation without filler and large karst cave and its casing provided by the present invention will be further fully described in detail with reference to the following embodiments. The following examples are illustrative only and are not to be construed as limiting the invention.
As shown in fig. 3, non-filler caverns 5 are distributed around a preset position of the karst region, the rock soil above the non-filler caverns 5 is called surface rock soil 4, and the rock soil below the non-filler caverns 5 is called bottom rock soil 6.
The casing 1 used for pile foundation construction comprises at least two casing units which are sequentially connected, and as shown in fig. 4, the adjacent casing units are connected together through connecting bolts 7 and connecting steel plates 8.
The pile casing 1 is internally provided with steel bars, and the grade of concrete is higher than C40, so that sufficient rigidity and strength are ensured to prevent the pile casing 1 from deforming and cracking in the use process. The inner diameter of the pile casing unit is equal to the diameter of a preset pile foundation, the thickness of the pile casing unit is 8-10 cm, and the height of each section of the pile casing unit is 1.5-2.0 m. The wall thickness of the pile casing 1 is 8-10 cm, the thickness of the steel pile casing used in the steel pile casing follow-up method is only 1cm, the rigidity of the pile casing 1 is far greater than that of the steel pile casing, and the construction process cannot generate obvious deformation.
As shown in fig. 5, eight bolt holes 9 are uniformly arranged on the inner wall of the casing unit along the radial direction, and the distance between the bolt hole 9 and the top end and/or the bottom end of the casing unit is 10 cm: the bolt holes 9 of the casing unit located at the uppermost end of the casing 1 are arranged 10cm above the bottom, the bolt holes 9 of the casing unit located at the lowermost end of the casing 1 are arranged 10cm below the top, and the bolt holes 9 of the remaining casing units are arranged 10cm away from the top and the bottom respectively. In addition, the bottom that is located the section of thick bamboo unit that protects of 1 top of a section of thick bamboo is equipped with protruding export, and all the other section of thick bamboo units that protect all are the top and are equipped with sunken mouthful, and the bottom is equipped with protruding export, so design be convenient for adjacent protect the connection location between a unit. As shown in fig. 5, three semicircular steel bar hanging rings 10 are uniformly embedded on the inner wall of each pile casing unit at a distance of 20cm from the top end along the radial direction.
As shown in FIG. 6, the connecting bolt 7 is made of high-strength steel and comprises a countersunk head, a screw rod and a nut, the length of the connecting bolt is 15-17 cm, and the diameter of the connecting bolt is 25-28 mm.
As shown in FIG. 7, the connecting steel plate 8 is made of high-strength steel, the length of the connecting steel plate 8 is 26cm, the width of the connecting steel plate is 6cm, and round holes with the diameter of 28-30 mm are formed in the two ends of the connecting steel plate.
Connecting bolt 7 and connecting steel plate 8 all adopt high strength steel, guarantee to transfer the in-process at a protecting section of thick bamboo unit and can not warp and fracture.
The pile foundation construction method for the large-scale karst cave without filler by using the casing 1 is characterized by comprising the following steps:
the first step is as follows: and prefabricating a plurality of sections of pile casing units with different heights, wherein the pile casing units are made of concrete, and the steel pile casings 3 are buried in the construction site to be positioned. As shown in fig. 3, the positioning steel casing 3 is buried in the ground, the uppermost end of the positioning steel casing 3 is not lower than the ground, and the uppermost end of the positioning steel casing is not lower than 50cm above the ground. The pile casing unit is prefabricated in a factory, the quality is strictly controlled during manufacturing, and the dimension error of each part needs to be less than 5 mm.
The second step is that: and drilling holes along the surface rock soil 4 inside the positioning steel casing 3 to form holes. And (3) drilling the surface rock soil 4 of the drilled hole above the filler-free karst cave 5 according to a conventional drilling method. And (3) drilling by using a drilling machine until the bottom of the hole is 1m away from the top surface of the filler-free cavern 5, stopping and taking out the drill bit, namely the top surface of the filler-free cavern 5 is 1m away from the bottom of the hole, and the hole is not communicated with the filler-free cavern 5. The diameter of the hole is larger than the diameter of the preset pile foundation by 15-20 cm.
The third step: and placing a cylinder protecting unit on the hole, and aligning the center line of the cylinder protecting unit and the center line of the positioning steel cylinder 3, wherein the cylinder protecting unit is a bottom cylinder protecting unit. The method for placing a casing unit on the hole comprises the following steps: two I-shaped steel plates are erected at the top of the positioning steel casing 3, the casing unit is placed on the I-shaped steel plates and centered and in place with the positioning steel casing 3 by using a truck crane, the center lines of the casing unit and the positioning steel casing 3 are aligned, and the casing unit is a bottom casing unit, namely a casing unit located at the bottommost part of the casing 1.
The fourth step: and then placing a cylinder protecting unit above the bottom cylinder protecting unit in the third step to align the central lines of the two cylinder protecting units, and connecting and fixing the two cylinder protecting units. Two adjacent pile casing units are fixedly connected through a connecting bolt 7 and a connecting steel plate 8, the central position and the verticality of the pile casing unit need to be checked in the process of fixing and connecting, and if the deviation between the central line of the pile casing unit and the central line of the positioning steel pile casing 3 exceeds a set range, the pile casing unit is adjusted until the pile casing unit meets the requirements.
The fifth step: and (5) putting the two sections of the pile casing units obtained in the fourth step down along the holes, gradually increasing the pile casing units upwards and connecting the pile casing units, and positioning and connecting the pile casing units. The method for lowering the casing protection unit comprises the following steps: and lifting the two pile casing units by using a truck crane, drawing out the I-shaped steel padded below the bottom pile casing unit, slowly lowering the pile casing in the hole, and checking the central position and the verticality of the pile casing unit at any time in the lowering process so as to ensure that the central lines of the two pile casing units are aligned with the central line of the positioning steel pile casing 3. The error between the central position of the pile casing unit and the center of the positioning steel pile casing 3 is less than 30mm and the error of perpendicularity is less than 1 percent in the lowering process.
And a sixth step: and (4) after the section of the pile casing unit is placed, connecting the section of the pile casing unit on the ground, repeating the fourth step and the fifth step until the bottom of the bottom pile casing unit contacts the bottom of the hole, and the top of the uppermost pile casing unit is not lower than the ground.
The seventh step: and (3) impacting the surface rock soil 4 below the hole and on the filler-free karst cave 5 by using a punch hammer with a small stroke of 50-80 cm along the interior of the pile casing unit, pumping out slurry in the hole when the distance from the bottom of the hole to the top surface of the filler-free karst cave 5 is 0.5m, then continuously breaking the surface rock soil 4 below the hole and on the filler-free karst cave 5 by using a small stroke of 30-50 cm, and finally lifting the punch hammer from the hole.
The segmented impact hammer impact method can timely pump out the slurry in the hole, so that the bottom surface of the filler-free karst cave below the through hole is basically free of slurry accumulation, and stable placement of a subsequent pile casing is facilitated. If the hole is directly communicated by a drilling machine, the slurry originally positioned in the hole area falls to the bottom surface of the filler-free karst cave below the hole to form slurry accumulation, the accumulation is soft and unstable, and the pile casing can be unstable when placed on the pile casing. In addition, the extracted mud can be used for drilling of the underlying rock soil 6.
Eighth step: and after the holes are communicated, continuing to put down the fixed pile casing units, when the bottoms of the bottom pile casing units are not contacted with the bottom surface of the filler-free karst cave and the bottoms of the uppermost pile casing units are not higher than the ground, adding a pile casing unit above the uppermost pile casing unit, and repeating the positioning connection method in the same step as the fourth step until the bottoms of the bottom pile casing units are contacted with the bottom surface of the filler-free karst cave and the tops of the uppermost pile casing units are not lower than the ground, so that the pile casing units are sequentially connected and penetrate through the holes and the filler-free karst cave 5 to form a pile casing 1.
The ninth step: and (5) filling filler into the pile casing 1 obtained in the eighth step to completely block the gap between the bottom end of the pile casing 1 and the bottom surface of the filler-free karst cave 5. The backfilled filler is a mixture of rubbles, clay and cement, the proportion of the rubbles, the clay and the cement is 10:5:1, and the mixture is repeatedly punched by a punch hammer to completely block a gap between the bottom end of the casing 1 and the bottom surface of the filler-free cavern 5.
The tenth step: and (3) pouring slurry into the pile casing 1, then continuously drilling by adopting a conventional drilling method, cleaning the hole after continuously drilling to a preset depth, lowering a reinforcement cage, and pouring underwater concrete to form a pile foundation 2.
In the above steps, if a small amount of gaps appear at the connecting parts of the adjacent casing units, a water-stopping adhesive tape can be stuck at the gap parts to prevent slurry in the holes from leaking.
After the bottom of the bottom pile casing unit is supported on the bottom surface of the filling-free karst cave 5, the truck crane cannot be loosened, and the gap between the bottom of the bottom pile casing unit and the bottom surface of the filling-free karst cave 5 must be completely blocked to prevent slurry in holes from leaking out when drilling holes in the lower rock soil.
If the cylinder protecting unit is blocked in the lowering process, a gasoline hammer is adopted to beat the top end of the uppermost cylinder protecting unit to enable the uppermost cylinder protecting unit to slowly sink.
Finally, it must be said here that: the above embodiments are only used for further detailed description of the technical solutions of the present invention, and should not be understood as limiting the scope of the present invention, and the insubstantial modifications and adaptations made by those skilled in the art according to the above descriptions of the present invention are within the scope of the present invention.
Claims (12)
1. The construction method of the pile foundation of the large karst cave without the filler is characterized by comprising the following steps:
the first step is as follows: prefabricating a plurality of sections of pile casing units with different heights, wherein the pile casing units are made of concrete and are positioned by burying a set steel pile casing (3) in a construction site;
the inner diameter of the pile casing unit is equal to the diameter of a preset pile foundation, the wall thickness of the pile casing unit is 8-10 cm, and the height of each pile casing unit is 1.5-2.0 m;
the second step is that: drilling along the surface rock soil (4) inside the positioning steel casing (3) to form a hole;
the holes in the second step are not communicated with the filling-free karst caves (5);
the third step: placing a pile casing unit above the hole, and aligning the pile casing unit with the center line of the positioning steel pile casing (3) to form a bottom pile casing unit;
thirdly, two I-shaped steel plates are erected on the top of the positioning steel casing (3), and the casing unit is placed on the I-shaped steel plate and is centered with the positioning steel casing (3) in position by using a truck crane;
the fourth step: placing a cylinder protecting unit above the middle-end cylinder protecting unit in the third step to align the central lines of the two cylinder protecting units, and connecting and fixing the two cylinder protecting units;
the pile casing (1) comprises two connecting steel plates (8), and the adjacent pile casing units are connected and fixed by connecting bolts (7) and the connecting steel plates (8); the top of each pile casing unit is provided with a concave opening and/or the bottom of each pile casing unit is provided with a convex opening matched with the concave opening, and the adjacent pile casing units are clamped and positioned through the concave openings and the convex openings; eight bolt holes (9) are uniformly formed in the upper end and/or the lower end of the cylinder wall of the cylinder protection unit along the radial direction, the distance between each bolt hole (9) and the top end or the bottom end of the cylinder protection unit is 5-15 cm, and three semicircular steel bar hanging rings (10) are uniformly embedded in the inner wall of each cylinder protection unit along the radial direction at a position 15-25 cm away from the top end;
the fifth step: the two sections of the casing units obtained in the fourth step are placed downwards along the holes, the top of each casing unit is gradually increased upwards and connected with the casing units, the connection method is positioned in the fourth step, the casing units are stopped to be increased until the casing units at the bottom end contact the bottom surface of the non-filler karst cave (5), and all the casing units form a casing (1);
the fifth step is specifically divided into the following three steps:
(a) when the hole is not communicated with the filler-free karst cave (5), lowering the pile casing unit, adding a pile casing unit above the top pile casing unit, repeating the positioning and connecting method with the fourth step until the bottom of the bottom pile casing unit is contacted with the bottom of the hole and the top of the top pile casing unit is not lower than the ground;
(b) breaking surface rock soil (4) on the non-filler karst cave (5) along the interior of the pile casing unit until the hole is communicated with the non-filler karst cave (5);
(c) lowering a pile casing unit, when the bottom of the bottom pile casing unit is not contacted with the bottom surface of the filler-free karst cave (5) and the bottom of the top pile casing unit is not higher than the ground, adding a pile casing unit above the top pile casing unit, and positioning and connecting the method with the fourth step, repeating the steps until the bottom of the bottom pile casing unit is contacted with the bottom surface of the filler-free karst cave (5) and the top of the top pile casing unit is not lower than the ground to form a pile casing (1);
and a sixth step: backfilling fillers into the protective cylinder (1) in the fifth step to ensure that no gap exists between the bottom end of the protective cylinder (1) and the filler-free karst cave (5);
the seventh step: and continuously drilling along the inside of the pile casing (1) to a preset depth, cleaning holes, putting down a reinforcement cage, and pouring underwater concrete to form a pile foundation (2).
2. The pile foundation construction method of the large-sized void without filler according to claim 1, wherein in the second step, the drilling is stopped and the drill bit is lifted up until the distance between the bottom of the hole and the top surface of the void without filler (5) is 0.5m to 1.5 m.
3. The pile foundation construction method of the large-scale unfilled karst cave according to claim 1, wherein in the step (b), the hammer is used to impact the surface rock soil (4) with a small stroke of 50-80 cm, when the distance from the bottom of the hole to the top surface of the large-scale unfilled karst cave (5) is 30-70 cm, the slurry in the hole is pumped out, then the surface rock soil (4) is broken with a small stroke of 30-50 cm, the hole and the large-scale unfilled karst cave (5) are communicated, and the hammer is lifted out of the hole.
4. The pile foundation construction method of the large-scale karst cave without filler according to claim 1, characterized in that the uppermost end of the positioning steel casing (3) in the first step is not lower than the ground.
5. The pile foundation construction method of the large-scale karst cave without filler according to claim 4, characterized in that the uppermost end of the positioning steel casing (3) is not lower than 50cm above the ground.
6. The pile foundation construction method of the large-scale karst cave without filler according to claim 1, wherein the diameter of the hole in the second step is 15-20 cm larger than the preset pile foundation diameter.
7. The method for constructing a pile foundation of a large-sized karst cave without filler according to claim 1, wherein in the fifth step, two pile casing units are lifted by a truck crane, i-beams padded under the bottom pile casing unit are drawn out, the pile casing units are slowly lowered along the hole, and the central position and the verticality of the pile casing units are checked at any time during the lowering.
8. The method for constructing the pile foundation of the large-scale karst cave without filler according to claim 1, wherein in the sixth step, the filler backfilled into the casing (1) is a mixture formed by rubbles, clay and cement, and the mixture is repeatedly punched by a punch hammer until the gap between the bottom end of the casing and the bottom surface of the karst cave without filler (5) is completely blocked.
9. The method for constructing a pile foundation of a large-sized karst cave without fillers according to claim 8, wherein the mass ratio of the slate, the clay and the cement is 10:5: 1.
10. The method for constructing the pile foundation of the large-scale karst cave without filler according to claim 1, wherein in the seventh step, slurry is poured into the casing (1), then the hole is continuously drilled along the inside of the casing (1) to a preset depth, the hole is cleaned, a reinforcement cage is put down, and underwater concrete is poured to form the pile foundation (2).
11. The pile casing for the large-scale karst cave without filler is characterized by being used for the pile foundation construction method of any one of claims 1 to 10, wherein the pile casing (1) comprises at least two pile casing units which are connected in sequence, and the pile casing units are made of concrete.
12. A casing unit according to claim 11, wherein the height of each casing unit is not exactly the same.
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| CN109371962A (en) * | 2018-10-31 | 2019-02-22 | 浙江华东建设工程有限公司 | Pile In Karst Area protective device |
| CN109868810A (en) * | 2019-02-27 | 2019-06-11 | 中建一局集团第一建筑有限公司 | One kind passing through buried major diameter discarded pipe and does operation pile making method |
| CN109797740A (en) * | 2019-03-27 | 2019-05-24 | 湖北中南岩土工程有限公司 | A kind of cast-in-situ bored pile and its construction method across underground civil defence structure |
| CN112855029B (en) * | 2021-04-26 | 2021-07-20 | 中铁九局集团第七工程有限公司 | Goaf drilling external pipe expansion construction method |
| CN113404049A (en) * | 2021-08-03 | 2021-09-17 | 中国港湾工程有限责任公司 | Offshore platform pile foundation construction method |
| CN115198753B (en) * | 2022-06-20 | 2023-07-04 | 上海工程技术大学 | Structure, manufacturing mold and application thereof |
| CN115450204B (en) * | 2022-10-17 | 2023-11-21 | 上海宝冶集团有限公司 | Construction method for rotary digging and pore forming of karst cave geological concrete recharging matched with steel casing |
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| JPH11269874A (en) * | 1998-03-24 | 1999-10-05 | Seiji Matsushita | Pile construction method for foundation pile |
| CN103195058B (en) * | 2013-04-03 | 2015-08-19 | 四川川交路桥有限责任公司 | Be convenient to solution cavity and grow the method that regional bridge pier adopts many casings to construct |
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