1. A pile foundation construction method is characterized by comprising the following steps:

the first step, burying an outer protective cylinder;

a second step of starting first punching, stopping the first punching until the first punching reaches a first preset position above the top of the karst cave;

thirdly, performing high-pressure jet grouting pile construction along the periphery of the pile foundation, and performing covering layer silt consolidation;

fourthly, an inner protecting cylinder is put in, and the inner protecting cylinder is arranged in the outer protecting cylinder;

fifthly, breaking the top of the karst cave by adopting a vibration hammer, enabling slurry to flow into the karst cave, and extending the inner protective cylinder to a second preset position at the bottom of the karst cave;

and step six, reconfiguring the slurry, starting punching for the second time, and stopping punching for the second time when the second punching reaches the second preset position at the bottom of the karst cave.

And seventhly, placing a reinforcement cage, and pouring reinforced concrete.

2. The pile foundation construction method according to claim 1, further comprising an eighth step after the fourth step of: and carrying out high-pressure rotary jet grouting on the pile between the outer pile casing and the inner pile casing to carry out backfill soil layer sediment consolidation.

3. The pile foundation construction method according to claim 1, further comprising a ninth step after the seventh step of: and pulling out the outer protective cylinder and reserving the inner protective cylinder.

4. The pile foundation construction method according to claim 1, wherein the first preset position is a position from the first punching to a distance of two meters from the top of the karst cave.

5. The pile foundation construction method according to claim 1, wherein the second preset position is a position where the second punching is performed to a distance of two meters from the bottom surface of the karst cave.

6. The pile foundation construction method of claim 1, wherein the wall thickness of the inner casing is 10 cm to 18 cm.

7. The pile foundation construction method according to claim 1, wherein a plurality of sets of reinforcement hoops are arranged on the outer side of the top of the inner casing, the outer side of the bottom of the inner casing and the outer side of the middle part of the inner casing.

8. The method of constructing a pile foundation of claim 7, wherein each set of said reinforcement hoops includes at least two said reinforcement hoops, the distance between the two reinforcement hoops being 80 mm, and the width of each reinforcement hoop being 10 mm.

Background

With the development of cities, building engineering technology is developed and matured day by day, but the safety performance of buildings is still a continuously pursued target in the building field.

Before the beginning of general building engineering, pile foundation construction is required to lay the foundation of a building. However, as the construction environment is more and more complex and diversified, the construction environment puts higher technical requirements on the construction technology. The common construction environment conditions are that the construction is close to residential areas, the land is soft, the geological conditions are poor, karst caves are dense and the like, so the pile foundation construction faces a severe construction problem.

In the process of constructing the pile foundation of the bridge, when the karst cave is broken down, the karst cave collapses possibly, so that the ground above the karst cave collapses, even the cracks of surrounding residential buildings collapse possibly, and serious safety threat is caused to the life of surrounding residents.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art. Therefore, the pile foundation construction method provided by the invention can enhance the strength of a soil layer around the pile foundation, reduce the hole collapse rate of the pile foundation when the pile foundation meets karst caves in a karst development area, and ensure the safety of construction machinery and bottom surface buildings.

According to the pile foundation construction method provided by the embodiment of the invention, the pile foundation construction method comprises the following steps: embedding an outer protective cylinder; the second step is as follows: starting first punching, namely, punching the first time to a first preset position above the top of the karst cave, and stopping punching the first time; the third step: carrying out high-pressure jet grouting on the pile along the periphery of the pile foundation to carry out covering layer silt consolidation; the fourth step: an inner protecting cylinder is arranged in the outer protecting cylinder; the fifth step: adopting a vibration hammer to break the top of the karst cave, enabling slurry to flow into the karst cave, and prolonging the inner protective cylinder to a second preset position at the bottom of the karst cave; a sixth step: reconfiguring the slurry, starting to punch for the second time, and stopping punching for the second time when the second time is punched to the second preset position at the bottom of the karst cave; a seventh step of: and placing a steel reinforcement cage, and pouring reinforced concrete.

The pile foundation construction method provided by the embodiment of the invention at least has the following beneficial effects: the pile foundation construction method changes the traditional pile foundation construction method, firstly, a punching drill is adopted to punch to a position two meters above the top of the karst cave, then the inner protecting cylinder is put into the inner protecting cylinder, then high-pressure jet grouting pile construction is carried out on the periphery of the inner protecting cylinder, so that a covering layer is stabilized, then the inner protecting cylinder is sunk by the vibrating hammer to break through the karst cave and is buried at the bottom of the karst cave, and finally, a reinforcement cage is put into the inner protecting cylinder and reinforced concrete is poured. The high-pressure jet grouting pile can be used for reinforcing a soft soil layer in the covering layer, the strength of the soil layer can be enhanced, and the covering layer cannot deform greatly, so that the hole collapse rate of the pile foundation in a karst development area when encountering a karst cave is reduced, and the safety of construction machinery and surface structures can be effectively ensured.

According to some embodiments of the invention, the fourth step is followed by an eighth step: and carrying out high-pressure rotary jet grouting on the pile between the outer pile casing and the inner pile casing to carry out backfill soil layer sediment consolidation.

According to some embodiments of the invention, the seventh step is followed by a ninth step: and pulling out the outer protective cylinder and reserving the inner protective cylinder.

According to some embodiments of the invention, the first predetermined position is a position two meters away from the top of the cavern from the first punching.

According to some embodiments of the invention, the second predetermined position is a position of the second punching to a distance of two meters from the bottom surface of the cavern.

According to some embodiments of the invention, the inner casing has a wall thickness of 10 cm to 18 cm.

According to some embodiments of the invention, a plurality of sets of reinforced hoops are arranged on the outer side of the top of the inner casing, the outer side of the bottom of the inner casing and the outer side of the middle part of the inner casing.

According to some embodiments of the invention, each set of reinforcing hoops comprises at least two reinforcing hoops, the distance between the two reinforcing hoops is 80 mm, and the width of each reinforcing hoop is 10 mm.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a schematic flow chart of a pile foundation construction method according to an embodiment of the present invention;

FIG. 2 is a schematic illustration of a hole punch drill according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of a high pressure jet grouting pile operation according to an embodiment of the present invention;

FIG. 4 is a schematic view of an embodiment of the present invention deployed into an inner sheath;

FIG. 5 is a schematic view of an embodiment of the present invention with an inner sheath breaking through the top of the cavern and reaching a design position;

FIG. 6 is a schematic view of a second punching to a designed elevation according to an embodiment of the present invention;

FIG. 7 is a schematic view of the embodiment of the present invention showing the placement of a reinforcement cage, the pouring of reinforced concrete, and the removal of an outer casing;

FIG. 8 is a top view of an embodiment of the present invention as it is lowered into an inner cartridge;

FIG. 9 is an enlarged partial schematic view of A shown in FIG. 5;

fig. 10 is a schematic view of reinforcement hoops on the outer sides of the upper, middle and lower parts of the inner casing according to the embodiment of the invention.

Reference numerals:

a soil layer 1 and a karst cave 2;

the device comprises a punching drilling machine 10, an outer protective sleeve 20, slurry 30, a high-pressure rotary jet grouting pile 40, an inner protective sleeve 50, a pile foundation 60 and a reinforcement hoop 70.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are exemplary only for the purpose of explanation and should not be construed as limiting the invention.

In the description of the present invention, it should be understood that the orientation or positional relationship referred to in the description of the orientation, such as the upper, lower, front, rear, left, right, etc., is based on the orientation or positional relationship shown in the drawings, and is only for convenience of description and simplification of description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.

In the description of the present invention, the meaning of a plurality of means is one or more, the meaning of a plurality of means is two or more, and larger, smaller, larger, etc. are understood as excluding the number, and larger, smaller, inner, etc. are understood as including the number. If the first and second are described for the purpose of distinguishing technical features, they are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.

In the description of the present invention, unless otherwise explicitly limited, terms such as arrangement, installation, connection and the like should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above terms in the present invention in combination with the specific contents of the technical solutions.

An embodiment of the present invention provides a pile foundation construction method, and referring to fig. 1, the pile foundation 60 construction method includes, but is not limited to, the following steps:

referring to fig. 2, a first step: the outer casing 20 is buried. The outer casing 20 which is firstly buried is positioned at the position where the hole needs to be punched, so that the functions of pile foundation 60 positioning marking and initial protection are achieved, and the inner casing 50 and other workpieces can be conveniently and subsequently put into the pile foundation.

Referring to fig. 2, a second step: and starting the first punching, and stopping the first punching to a first preset position above the top of the karst cave 2. After the outer casing 20 is positioned, the punching position is locked, the punching machine 10 can be used for punching at the punching position, and the punching can be stopped when the hole is punched to the first preset position above the top of the karst cave 2. It should be noted that the first preset position is a position that changes with the change of the construction environment, and may be two meters, three meters, or even one meter. The change of adaptability is made according to the soil property of soil layer 1 at cavern 2 top place to specific position, if the soil property is comparatively soft promptly, frictional force is less and intensity is not high, then the first distance of three meters that design for great is predetermine the position, if the soil property is comparatively hard and frictional force is great, then the first two meters that design for less of predetermineeing the position, so this embodiment does not do specific restriction to first predetermineeing the position, but when need satisfy and punch, the top of cavern 2 is not broken to drilling machine 10 that punches a hole. It should be noted that when the hole-punching drill 10 is performing the hole-punching operation, the cavity is filled with the slurry 30, the slurry 30 fills the cavity to maintain the stability of the hole, and the pressure balance is achieved with the surrounding overburden layer 1, so that the phenomenon of hole collapse of the vibrating overburden layer can be avoided when the hole-punching drill 10 punches the hole, and meanwhile, impurities broken by the drill bit in the hole can flow out of the hole through the circulation of the slurry 30 in the hole. The situation that the drill bit is blocked by impurities is avoided.

Referring to fig. 3 and 9, the third step: and (4) carrying out high-pressure jet grouting on the pile 40 along the periphery of the pile foundation 60 to carry out covering layer silt consolidation. When the punching drill 10 punches the hole to the first preset position at the top of the karst cave 2, the high-pressure rotary pile is carried out at the position of the periphery of the pile foundation 60, the solidification of the mud layer and the sand layer at the periphery of the pile position in the covering layer range is carried out, and the strength of the mud layer and the sand layer at the periphery of the pile position in the covering layer range is enhanced. When mud 30 in the subsequent top plate hole of the karst cave 2 punctured by the protective cylinder flows away, the soil layer 1 and the sand layer with enhanced strength can ensure that the peripheral covering layer does not deform and collapse along with the damage of the top plate of the karst cave 2, thereby ensuring the safety of the ground surface building of the construction peripheral site. It is worth noting that when the high-pressure jet grouting pile 40 needs to be put in, the drill bit is taken out firstly by the punching drill 10, then the high-pressure jet grouting pile 40 is carried out, the concrete jetted out in a high-pressure jet grouting mode breaks through the soil layer 1 and the sand layer of the covering layer and is mixed with the soil layer 1 and the sand layer of the covering layer into a whole, and the strength of the mud layer and the sand layer on the periphery of the pile position in the covering layer range can be enhanced after solidification, so that the purpose of enhancing the strength of the soil layer 1 and the sand layer of the covering layer is achieved. It should also be noted that the high pressure jet grouting pile 40 may be lowered to the top position of the cavern 2. In addition, it should be noted that. In the embodiment, the high-pressure rotary jet grouting pile 40 is constructed in a construction process by using high-pressure slurry, high-pressure water and compressed air, wherein the construction pressure is not less than 20MPa, and meanwhile, the pressure deviation of the high-pressure slurry for high-pressure slurry construction is not more than ± 1MPa, the pressure deviation of the high-pressure water for high-pressure water construction is not more than ± 1MPa, and the pressure deviation of the compressed air for compressed air construction is not more than ± 0.1 MPa. The high pressure jet grouting pile 40 is known to those skilled in the art as a technique described in the art, and the high pressure jet grouting pile 40 will not be further described.

Referring to fig. 4 and 9, the fourth step: and is lowered into the inner casing 50, and the inner casing 50 is disposed in the outer casing 20. After the high-pressure jet grouting pile 40 is completed around the outer side of the pile foundation 60, the inner casing 50 can be inserted into the hole, the insertion position of the inner casing 50 is between the outer side of the hole and the inner side of the outer casing 20, and the insertion depth reaches the bottom of the hole. It should be emphasized that, after the fourth step, but not limited thereto, an eighth step may be further included, in which the high-pressure jet grouting pile 40 is performed between the outer casing 20 and the inner casing 50, and the sand consolidation of the backfill soil layer 1, that is, the sand consolidation of the soil layer 1 between the inner casing 50 and the outer casing 20, is performed. The silt consolidation of soil layer 1 between the inner protective sleeve 50 and the outer protective sleeve 20 can avoid the situation that the position between the inner protective sleeve 50 and the outer protective sleeve 20 deviates due to vibration when the inner protective sleeve 50 continues to sink in the following step, so that the construction precision of the pile foundation 60 is influenced, and potential safety hazards can be generated. Therefore, the silt of the soil layer 1 between the inner casing 50 and the outer casing 20 is consolidated, so that the balance between the outer casing 20 and the inner casing 50 can be kept, and the relative position between the two casings can be kept unchanged.

Referring to fig. 5, a fifth step: and (3) breaking the top of the karst cave 2 by adopting a vibration hammer, enabling the slurry 30 to flow into the karst cave 2, and extending the inner protective cylinder 50 to a second preset position at the bottom of the karst cave 2. After the inner protecting cylinder 50 is dropped, the vibrating hammer is adopted to sink the inner protecting cylinder 50 to break the top of the karst cave 2, namely, the top of the karst cave 2 is broken from the position of the first preset position. When the inner sheath 50 breaks the top of the cavern 2, the slurry 30 in the hole immediately flows out of the gap at the top of the cavern 2 into the cavern 2. At this time, it can be understood that, since the high pressure jet grouting pile 40 is provided outside the inner casing 50, the reinforced coating layer is not likely to collapse due to the slurry 30 flowing out of the hole. Meanwhile, the inner casing 50 is extended to a second predetermined position of the bottom of the karst cave 2 by the hammering movement of the vibration hammer. It should be emphasized here that the second preset position is consistent with the above mentioned first preset position principle, i.e. in order to ensure that the pile foundation 60 is stably stressed in the bearing stratum at the bottom of the karst cave 2, the second preset position is determined according to the environmental factors such as soil quality of the soil layer 1 at the bottom of the karst cave 2 and the diameter of the pile foundation 60. The second preset position can be two meters generally, or four meters when the soil quality is soft, and the like, the second preset position is not specifically limited, but the requirement that the pile foundation 60 can continuously bear force in the bearing layer at the bottom of the karst cave 2 is met.

Referring to fig. 6, a sixth step: and (5) reconfiguring the slurry 30, starting to punch for the second time, and stopping punching for the second time until the second time reaches a second preset position at the bottom of the karst cave 2. In order to stress the pile foundation 60 on the bearing layer of the karst cave 2, the hole needs to be extended to a second preset position, after the inner casing 50 is sunken and extended to the second preset position, the slurry 30 is reconfigured between the inner casings 50, the punching machine 10 is used for continuously punching the hole in the inner casing 50, and when the hole is punched to the second preset position at the bottom of the karst cave 2, namely the designed position, the punching can be stopped.

Referring to fig. 7, a seventh step: and placing a steel reinforcement cage, and pouring reinforced concrete. After the punching of the set elevation is completed, the hole of the pile foundation 60 is drilled, a reinforcement cage which is made in advance can be placed into the hole, then the steel bar concrete is poured into the hole, after the reinforcement cage is solidified, the pile foundation 60 can be formed, and accordingly, the forming work of the pile foundation 60 is completed. However, it is understood that, the seventh step may further include, but is not limited to, a ninth step of removing the outer sheath 20 and retaining the inner sheath 50. Since the inner casing 50 is filled with the reinforced concrete, the inner casing 50 cannot be taken out, and the inner casing 50 can also protect the pile foundation 60. The pulled out outer protective sleeve 20 can be reused, and unnecessary waste is reduced.

The construction method of the pile foundation 60 provided by the embodiment changes the traditional construction method of the pile foundation 60, firstly, a punching drill 10 is adopted to punch holes to a position two meters above the top of the karst cave 2, then the inner pile casing 50 is put in, then the high-pressure jet grouting pile 40 construction is carried out on the periphery of the inner pile casing 50, so that the covering layer is stabilized, then the inner pile casing 50 is sunk by a vibration hammer to break through the karst cave 2 and is embedded into the bottom of the karst cave 2, and finally, a reinforcement cage is put in and reinforced concrete is poured. The high-pressure jet grouting pile 40 is adopted to reinforce the soft soil layer 1 in the covering layer, so that the strength of the soil layer 1 can be enhanced, the covering layer can not deform greatly, the hole collapse rate of the pile foundation 60 in the karst development area when encountering the karst cave 2 is reduced, and the safety of construction machinery and surface structures can be effectively ensured.

In some embodiments of the invention, the inner casing 50 has a wall thickness of 10 cm to 18 cm. Because the construction method of the pile foundation 60 provided by the invention is added with the construction method of the high-pressure jet grouting pile 40, the construction method of the pile foundation 60 can be used for the construction engineering with large pile diameter. It is conceivable that the diameter of the inner casing 50 changes with the change of the pile diameter, and since there is a friction force between the wall of the inner casing 50 and the soil layer 1, if the diameter is larger, the friction force is larger, and the wall thickness of the required inner casing 50 is larger, so that since a construction work with a large pile diameter can be used, the wall thickness of the inner casing 50 to be used should also change with the change of the pile diameter, and a smaller wall thickness, for example, ten centimeters, is used for the inner casing 50 with a smaller pile diameter; if the inner casing 50 with a larger pile diameter has a thicker wall thickness, the wall thickness can be eighteen centimeters. Meanwhile, the adopted wall thickness is determined according to the pile diameter, and the wall thickness mentioned in the embodiment is only taken as an example and is not specifically limited, so that the inner casing 50 is not deformed by extrusion.

Referring to fig. 8 and 10, in some embodiments of the present invention, several sets of reinforcement hoops 70 may be disposed on the outside of the top of the inner casing 50, the outside of the bottom of the inner casing 50, and the outside of the middle of the inner casing 50. The reinforcement hoop 70 can reinforce the strength of the inner casing 50, and avoid deformation caused by impact of large soil layer 1 load and a vibration hammer when the inner casing 50 sinks, which is not beneficial to the sinking of the inner casing 50.

Referring to fig. 8 and 10, in some embodiments of the present invention, each set of reinforcement hoops 70 further comprises at least two reinforcement hoops 70, the distance between the two reinforcement hoops 70 is 80 mm, and the width of each reinforcement hoop 70 is 10 mm. It is conceivable that more reinforcement hoops 70 increase the friction between the outer side of the inner casing 50 and the soil layer 1, which is not favorable for the sinking of the inner casing 50, so that the friction when the inner casing 50 is sunk is satisfied, and the number of reinforcement hoops 70 and the distance between the reinforcement hoops 70 are also considered.

In summary, referring to fig. 1, the following will further describe the construction method of the pile foundation 60 provided by the embodiment of the present invention by taking a complete construction method of the pile foundation 60 as an example: firstly, embedding the outer casing 20 for pile foundation 60 positioning; then, a punching drill 10 is used for punching for the first time, and when the first punching reaches a first preset position above the top of the karst cave 2 (the first preset position is selected according to the embodiment), the first punching is stopped; then, high-pressure jet grouting pile 40 construction is carried out along the periphery of the pile foundation 60, and the silt consolidation of the covering layer is realized; then, the inner casing 50 is arranged below the outer side of the pile foundation 60 and the inner side of the outer casing 20, and the inner casing 50 is sunk to the top of the karst cave 2; after the inner pile casing 50 is put in, the construction of the high-pressure rotary jet grouting pile 40 can be carried out in the backfill soil layer 1 between the inner pile casing 50 and the outer pile casing 20 for one time so as to realize the sand consolidation of the backfill soil layer 1; then, the inner casing 50 can be hammered into the top of the karst cave 2 by using a vibration hammer, the slurry 30 flows into the karst cave 2, and the inner casing 50 continues to sink to a second preset position (the second preset position is selected by referring to the above embodiment); then, a second punching is carried out by adopting the punching drilling machine 10, the slurry 30 needs to be reconfigured before the second punching, and the second punching is stopped when the second punching reaches a second preset position; then, a reinforcement cage which is made in advance can be placed, reinforced concrete is poured, finally, the outer casing 20 is pulled out, and the inner casing 50 is reserved. By this, the construction of the pile foundation 60 is completed.

The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present invention.