Construction method of cast-in-place concrete pile in strong karst development area

Abstract

The invention discloses a construction method of a cast-in-place concrete pile in a strong karst development area, which comprises the following steps of: firstly, carrying out drilling construction at a pile position, penetrating through karst geology by adopting a slurry wall protection technology, entering a rock stratum, and carrying out primary hole cleaning; secondly, a reinforcement cage is manufactured, a glass fiber sleeve is arranged in a corresponding karst section of the reinforcement cage according to a one-pile-one-detection report, the glass fiber sleeve is implemented in multiple sections, the upper section and the lower section are connected in the mode that the upper section is inserted into the lower section by 200-300 mm, and the total length protrudes by 500 mm relative to the bottom face and the top face of the karst cave; in the manufacturing process, vertical joint connection is achieved through epoxy resin glue injection, sleeve opening, temporary fixing through a fastening belt and fastening through a stainless steel self-tapping screw, meanwhile, hook-shaped limiting stoppers are arranged on the inner wall of the sleeve at equal intervals, and position adjustment and secondary reinforcement are achieved through connection of an adjusting groove, an inner pressing plate, an outer pressing plate and a spring. And finally, after secondary hole cleaning is completed, concrete is poured through the guide pipe to form the pile.

Description

Technical Field

[0001] The present invention relates to the field of engineering construction, and particularly to a construction method for cast-in-place concrete piles in areas with strong karst development. Background Art

[0002] When conducting pile foundation construction in areas with strong karst development, complex geological conditions are often faced. In particular, the particularity of karst geology brings many challenges to construction. Traditional construction methods for pile foundations in karst geology mainly include grouting methods, clay or low-grade concrete filling methods, steel casing methods, and concrete overpouring methods, etc.

[0003] The grouting method is widely used in the construction of pile foundations in karst geology, but it has problems such as difficult accurate control of the grouting volume, uncontrollable project cost during the construction process, and difficult detection of the actual effect. These disadvantages make the grouting method unable to achieve the expected effect under certain special geological conditions, resulting in the impact on construction quality and construction progress. The clay or low-grade concrete or mortar filling and wall-building method can be used to stabilize the karst formation in some cases, but its disadvantages are that secondary hole formation is required, the construction period is long, and the overall project cost is high. Due to the poor strength and compactness of the filling material, the situation of pile foundation instability caused by improper construction is likely to occur. As a common supporting structure, the steel casing can effectively avoid hole collapse, but its recovery process is complex and the cost is high. In addition, the installation process of the steel casing requires precise docking, increasing the construction difficulty and time, resulting in an increase in the overall project cost. The concrete overpouring method is usually used to fill the hole wall in karst areas, but there is a problem that the amount of concrete is difficult to estimate, resulting in problems such as sudden sinking of the concrete pouring surface of the pile foundation and pulling out of the conduit during the construction process. Such situations not only affect the quality of the pile foundation, but also may cause quality problems such as pile breakage and difficult control of the pile top elevation. At the same time, the amount of overpoured concrete is usually large, resulting in an increase in project cost and easy waste during the construction process.

[0004] Therefore, the existing construction methods for pile foundations in karst geology have various deficiencies, and there is an urgent need for a construction method for cast-in-place concrete piles in areas with strong karst development, which is optimized based on the traditional construction plan. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above-mentioned deficiencies existing in the prior art, and to provide a construction method for cast-in-place concrete piles in areas with strong karst development.

[0006] The technical solution adopted by the present invention to solve the above problems is: a construction method for cast-in-place concrete piles in areas with strong karst development,

[0007] including the following steps:

[0008] S1: Move the drill rig to the pile position, construct the pile hole, use slurry to support the wall, penetrate the karst geology and then enter the rock and conduct primary hole cleaning once.

[0009] S2: Fabricate the steel reinforcement cage, lay out fiberglass sleeves in the corresponding karst geology sections of the steel reinforcement cage according to the one-pile-one-exploration report, and place the steel reinforcement cage into the pile hole and conduct secondary hole cleaning.

[0010] S3: After the secondary hole cleaning operation is completed, pour concrete through the conduit to form a pile.

[0011] Preferably: When fabricating the fiberglass sleeves in S2, it is necessary to connect their vertical joints, which includes

[0012] S2.1: Inject epoxy resin glue into the locking groove of the sleeve.

[0013] S2.2: Expand the fiberglass sleeve and wrap the steel reinforcement cage.

[0014] S2.3: After precise positioning, temporarily fix the fiberglass sleeve with a fastening belt.

[0015] S2.4: Fasten the sleeve locking part with stainless steel self-tapping screws every 150 mm.

[0016] Preferably: During the construction of S2, the fiberglass sleeves are implemented in sections according to the height of the karst cave. For the adjacent upper and lower sections, the upper section is inserted into the lower section by 200 mm - 300 mm, and the total length of the fiberglass sleeve protrudes 500 mm from both the bottom and top surfaces of the karst cave.

[0017] Preferably: In S2, a limiter is circumferentially arranged on the fiberglass sleeve. The limiter adopts a hook-shaped structure, which includes a limit seat arranged on the fiberglass sleeve and a hook part arranged on the limit seat for grasping the spiral hoop of the steel reinforcement cage.

[0018] Preferably: In S2, the relative vertical position of the limit seat on the fiberglass sleeve is adjustable and is fixed once through a fastener, and then is secondarily reinforced with structural adhesive to the fiberglass sleeve.

[0019] Preferably: The fiberglass sleeve is provided with a vertical adjustment groove for installing the limit seat. The limit seat includes an inner pressure plate and an outer pressure plate respectively arranged on the inner and outer wall surfaces of the fiberglass sleeve. The inner pressure plate is slidably arranged on the adjustment groove, and the fastener passes through the outer pressure plate and is threadedly connected and adapted to the inner pressure plate.

[0020] Preferably: A limit post is arranged at the center position of the inner surface of the inner pressure plate. The hook part is provided with a through hole slidably connected and adapted to the limit post, and the hook part is also elastically connected to the inner pressure plate through a spring sleeved on the outer periphery of the limit post.

[0021] Preferably, the length of the inner pressing plate is greater than that of the adjusting groove, so that the adjusting groove is always in a blocked state during the up and down sliding of the inner pressing plate.

[0022] Preferably, the outer pressing plate is made of fiberglass material, and the inner pressing plate and the hook part are both made of aluminum alloy material.

[0023] Compared with the prior art, the present invention has the following advantages and effects:

[0024] By using the double protection structure of the steel reinforcement cage and the fiberglass sleeve, the present invention can effectively avoid the loss of concrete caused by the collapse of the pile wall or the action of water flow, and ensure the overall stability of the pile foundation. Compared with the traditional grouting method and overpouring method, the present invention simplifies the construction process, especially optimizes the steps such as pile hole, hole cleaning and concrete pouring, greatly shortens the construction period and improves the construction efficiency. At the same time, a limiter with a hook-shaped structure is arranged in the circumferential direction of the fiberglass sleeve. The limiter is composed of a limit seat and a hook part for grasping the spiral hoop of the steel reinforcement cage, and its up and down position is adjustable. After the initial fixation, it is secondarily reinforced with structural adhesive to ensure the firmness between the fiberglass sleeve and the steel reinforcement cage. Description of the Drawings

[0025] Figure 1 is a schematic flow chart of a construction method for a concrete cast-in-place pile in a strongly karst-developed area according to an embodiment of the present invention.

[0026] Figure 2 is Figure 1 the installation flow schematic diagram of the fiberglass sleeve in step S2.

[0027] Figure 3 is based on Figure 1 the finished product structure schematic diagram completed by the method in.

[0028] Figure 4 is the structural schematic diagram of the fiberglass sleeve according to an embodiment of the present invention.

[0029] Figure 5 is the structural schematic diagram of the preliminary fixation of the fiberglass sleeve on the steel reinforcement cage according to an embodiment of the present invention.

[0030] Figure 6 is the layout schematic diagram of the self-tapping screws fixed on the vertical joint of the fiberglass sleeve according to an embodiment of the present invention.

[0031] Figure 7 is the cross-sectional schematic diagram of the fiberglass sleeve fixed by the limiter according to an embodiment of the present invention.

[0032] Figure 8 is Figure 7 the partial enlarged schematic diagram of.

[0033] Figure 9It is a schematic cross-sectional view of the fiberglass sleeve limiter after being fixed in an embodiment of the present invention.

[0034] Reference numerals in the drawings: steel reinforcement cage 11, fiberglass sleeve 12, longitudinal steel bars 13, spiral stirrups 14, locking groove 15, epoxy resin glue 16, fastening belt 17, self-tapping screw 18, limiter 21, limit seat 22, hook portion 23, fastener 24, structural glue 25, adjustment groove 26, inner pressing plate 27, outer pressing plate 28, limit post 31, through hole 32, spring 33. Specific embodiments

[0035] The present invention will be further described in detail below with reference to the accompanying drawings and through embodiments. The following embodiments are explanations of the present invention, and the present invention is not limited to the following embodiments.

[0036] Embodiment: Refer to Figure 1 - Figure 4 , this embodiment provides a construction method for cast-in-place concrete piles in areas with strong karst development. This method is mainly applicable to areas with complex karst geological conditions, can effectively improve the construction quality of pile foundations, reduce the construction period, and reduce the project cost. The specific steps are as follows:

[0037] Step S1: Pile hole construction and primary hole cleaning

[0038] First, the construction drill is moved to the pile position, and pile hole operation begins. During drilling, the mud wall protection method is used to stabilize the hole wall and prevent the hole wall from collapsing. After the drill bit penetrates the karst geological layer, it enters the rock layer and conducts primary hole cleaning to remove the mud and debris in the hole, ensuring that the hole wall is clean and preparing for subsequent construction.

[0039] Step S2: Fabricate the steel reinforcement cage, arrange the fiberglass sleeve 12 on the corresponding karst geological section of the steel reinforcement cage according to the one-pile-one-exploration report, and place the steel reinforcement cage 11 with the fiberglass sleeve 12 already arranged. Place the conduit and conduct secondary hole cleaning.

[0040] Fabricate the steel reinforcement cage 11, and arrange the fiberglass sleeve 12 on the corresponding karst geological section of the steel reinforcement cage 11 according to the one-pile-one-exploration report. The arrangement of the fiberglass sleeve 12 needs to be implemented in sections according to the specific situation of the karst cave to ensure that it can effectively surround the steel reinforcement cage 11 and be in close contact with the hole wall during construction, avoiding the displacement and shedding of the fiberglass sleeve 12 and resulting in loss during the concrete pouring process.

[0041] Specifically, the steel reinforcement cage 11 is made of longitudinal steel bars 13 and externally wound spiral stirrups 14. After arranging the glass fiber sleeve 12, it is moved to the pile hole by means of hoisting or the like to ensure that the steel reinforcement cage 11 is completely stable in the pile hole. The glass fiber sleeve 12 in this embodiment is made by winding glass fiber material, has sufficient strength and can adapt to high-pressure environments. According to the height of the karst cave, the glass fiber sleeve 12 is divided into multiple segments, and the length of each segment depends on the depth and shape of the karst cave. Usually, when installing the adjacent upper and lower segments of the glass fiber sleeve 12, the upper segment is inserted into the lower segment by 200 mm to 300 mm. In this way, the formed group of glass fiber sleeves 12 are nested in sequence from bottom to top to ensure their stable connection. After the steel reinforcement cage 11 and the conduit with the glass fiber sleeve 12 arranged are installed, secondary hole cleaning is required. The purpose of secondary hole cleaning is to remove drilling slag and ensure that the thickness of the sediment at the bottom of the hole meets the design requirements, so as to ensure the quality of the pile foundation.

[0042] Step S3: Concrete is poured through the conduit to form a pile.

[0043] After the hole cleaning operation is completed, concrete pouring through the conduit begins. According to the design requirements of the pile foundation, a suitable concrete mix ratio is selected, and the concrete is sent into the hole through the conduit. During the pouring process, the stability and continuity of the pouring are maintained to avoid phenomena such as conduit blockage or concrete stratification. During the pouring process, the concrete should evenly fill the gap between the glass fiber sleeve 12 and the steel reinforcement cage 11 and gradually form a pile body. When the concrete is poured to the design elevation, the pouring is stopped in time, and necessary settlement observations are carried out to ensure the quality and stability of the pile foundation.

[0044] By using the double protection structure of the steel reinforcement cage 11 and the glass fiber sleeve 12, the present invention can effectively avoid the loss of concrete caused by pile wall collapse or water flow action, and ensure the overall stability of the pile foundation. Compared with the traditional grouting method and overpouring method, the present invention simplifies the construction process, especially optimizes the steps such as pile hole, hole cleaning and concrete pouring, greatly shortens the construction period and improves the construction efficiency.

[0045] In this embodiment, the design of the glass fiber sleeve 12 has certain particularities to ensure the structural stability and safety during the construction process. The specific construction details are as follows:

[0046] 1. Fractional section implementation: According to the complexity of the karst geology, the glass fiber sleeve 12 adopts a fractional section structure, and the length and diameter of each section are designed according to specific geological conditions. For example, in the case of relatively complex karst caves (large changes in karst cave morphology, irregular hole diameters, multiple branches, loose rock formations or water flow and air flow phenomena), such as the presence of fissures in the hole wall, the length of each section of the glass fiber sleeve 12 needs to be shortened to cope with the internal environment of the pile hole. The upper and lower joint parts of each section of the glass fiber sleeve 12 are connected by a plug-in design, and the connection part should be kept firm to prevent falling off or slipping during the construction process.

[0047] 2. Protrusion length of the fiberglass sleeve 12: The total length of the fiberglass sleeve 12 is adjusted according to the depth of the karst cave. The lower end of the fiberglass sleeve 12 should protrude at least 500 mm from the bottom surface of the karst cave to ensure that the concrete can completely fill the bottom area; the upper end also needs to protrude at least 500 mm from the top surface of the karst cave to prevent the upper concrete from overflowing or flowing out and ensure the stability of the pile top.

[0048] 3. Installation and fixation between the fiberglass sleeve 12 and the steel reinforcement cage 11:

[0049] See Figure 5 and Figure 6 When manufacturing the fiberglass sleeve 12 in S2, its vertical joints need to be connected, which includes

[0050] S2.1: The fiberglass sleeve 12 is formed by winding fiberglass sheets. A locking groove 15 is provided at the butt joint of the sleeve. Epoxy resin glue 16 needs to be injected into the locking groove 15 of the sleeve before connection;

[0051] S2.2: Expand the fiberglass sleeve 12 and wrap it outside the steel reinforcement cage 11. Holes can be drilled in the fiberglass sleeve 12 and fixed to the steel reinforcement cage 11 by on-site binding;

[0052] S2.3: Accurately position the fiberglass sleeve 12 and temporarily fix the fiberglass sleeve 12 with a fastening belt 17;

[0053] S2.4: Fasten the locking groove 15 of the fiberglass sleeve 12 with stainless steel self-tapping screws 18 every 150 mm. The fastening belt 17 can be removed after the installation of all fiberglass sleeves 12 is completed.

[0054] See Figures 7 - 9 In S2 of this embodiment, the position between the fiberglass sleeve 12 and the steel reinforcement cage 11 can also be fixed by a position limiter 21. The fiberglass sleeve 12 is circumferentially provided with a position limiter 21. The position limiter 21 adopts a hook-shaped structure, and its structure includes a position-limiting seat 22 provided on the fiberglass sleeve 12 and a hook portion 23 provided on the position-limiting seat 22 for grasping the spiral hoop 14 of the steel reinforcement cage 11. After the fiberglass sleeve 12 wraps the steel reinforcement cage 11, the spiral hoop 14 of the steel reinforcement cage 11 is firmly grasped by the hook portion 23, thereby restricting the relative slip of the fiberglass sleeve 12 and ensuring the stable position of the steel reinforcement cage 11 during concrete pouring.

[0055] In addition, in step S2, the vertical position of the limiting seat 22 relative to the glass fiber sleeve 12 is adjustable and is fixed once by a fastener 24. After the first fixation, it is further reinforced with a structural adhesive 25 and the glass fiber sleeve 12. The glass fiber sleeve 12 is provided with a vertical adjustment groove 26 for installing the limiting seat 22. The limiting seat 22 includes an inner pressing plate 27 and an outer pressing plate 28 respectively arranged on the inner and outer wall surfaces of the glass fiber sleeve 12. The inner pressing plate 27 is slidably arranged on the adjustment groove 26. The fastener 24 passes through the outer pressing plate 28 and is threadedly connected and adapted to the inner pressing plate 27. In this embodiment, a bolt can be used as the fastener 24.

[0056] Since the spiral stirrup 14 is spirally wound on the overall reinforcement cage 11 and its elevations at various circumferences are different, when the glass fiber sleeve 12 is hung, the height position of the position limiter 21 relative to the glass fiber sleeve 12 also needs to be adapted to the height of the spiral stirrup 14 on the grasping side. Therefore, the vertical position of the limiting seat 22 relative to the glass fiber sleeve 12 in this embodiment is adjustable. After the adjustment, the position of the limiting seat 22 needs to be fixed. In this embodiment, it needs to be fixed once and further reinforced twice. The specific operations are as follows:

[0057] a. Position adjustment: In this embodiment, the fastener 24 is a bolt. Before hanging, loosen the fastener 24 so that the limiting seat 22 can slide up and down along the adjustment groove 26. When hanging, fit the glass fiber sleeve 12 with the reinforcement cage 11 so that the position limiter 21 engages with the spiral stirrup 14 of the reinforcement cage 11. At this time, the height position of the glass fiber sleeve 12 can be finely adjusted along the adjustment groove 26.

[0058] b. First fixation: After the position of the glass fiber sleeve 12 is determined, tighten the fastener 24 so that the inner pressing plate 27 and the outer pressing plate 28 approach each other and press against the glass fiber sleeve 12 to achieve the preliminary fixation between the position limiter 21 and the glass fiber sleeve 12.

[0059] c. Second reinforcement: After the first fixation is completed, further reinforce the contact surface between the limiting seat 22 and the glass fiber sleeve 12 with an epoxy structural adhesive 25. The structural adhesive 25 needs to cover the entire adjustment groove 26.

[0060] During the construction of the steel reinforcement cage 11 (diameter size) and the production and processing of the fiberglass sleeve 12 (the opening position of the adjustment groove 26), errors are inevitable. Therefore, a length is reserved in advance when winding the fiberglass sleeve 12 with the fiberglass board, so that the fiberglass sleeve 12 can completely wrap the steel reinforcement cage 11. In addition, due to the upper-large and lower-small structural design of the fiberglass sleeve 12, the gap between its inner wall and the outer wall of the steel reinforcement cage 11 also changes. Therefore, the thickness of the limiter 21 also needs to be adjusted at any time according to the installation situation. In this embodiment, the thickness of the limiter 21 can be adaptively and elastically adjusted according to the gap between the two. Specifically, a limit post 31 is provided at the center position of the inner surface of the inner pressing plate 27, and the hook part 23 is provided with a through hole 32 adapted to be slidably connected to the limit post 31. Moreover, the hook part 23 and the inner pressing plate 27 are also elastically connected by a spring 33 sleeved on the outer periphery of the limit post 31. When the fiberglass sleeve 12 is wrapped around the steel reinforcement cage 11, the limiter 21 is located between the steel reinforcement cage 11 and the fiberglass sleeve 12. Under the extrusion action, the spring 33 between the hook part 23 and the inner pressing plate 27 contracts, so that the distance between the hook part 23 and the inner pressing plate 27 can be compressed, thereby realizing the adaptive adjustment of the thickness of the limiter 21 according to the gap between the fiberglass sleeve 12 and the steel reinforcement cage 11. The original length (when not extruded) of the spring 33 in this embodiment should be greater than 50 mm.

[0061] The length of the inner pressing plate 27 is greater than the length of the adjustment groove 26, so that the adjustment groove 26 is always in a blocked state during the up-and-down sliding of the inner pressing plate 27. The blocking of the adjustment groove 26 makes a closed environment formed inside the fiberglass sleeve 12 to prevent leakage from the adjustment groove 26 during subsequent concrete pouring. The outer pressing plate 28 is made of fiberglass material, and the inner pressing plate 27 and the hook part 23 are both made of aluminum alloy material.

[0062] The above content described in this specification is only an example of the present invention. Those skilled in the technical field to which the present invention pertains can make various modifications or supplements to the described specific embodiments or use similar methods to replace them, as long as they do not deviate from the content of this specification of the present invention or exceed the scope defined by this claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for constructing concrete bored piles in areas with strong karst development, characterized in that: The steps include: S1: The drilling rig moves to the pile position, constructs the pile hole, uses mud to protect the wall, penetrates the karst geology, enters the rock and cleans the hole once; S2: Make a steel cage, lay out the glass fiber sleeve on the corresponding karst geological section of the steel cage according to the pile-by-pile exploration report, put the steel cage into the pile hole and clean the hole twice; S3: After the secondary hole cleaning operation is completed, the conduit is poured with concrete to form a pile.

2. The method for constructing concrete bored piles in areas with strong karst development according to claim 1, characterized in that: During the S2 construction, the fiberglass sleeve was implemented in several sections depending on the height of the cave. The adjacent upper and lower sections were treated by inserting the upper section into the lower section by 200mm to 300mm. The total length of the fiberglass sleeve protruded 500mm relative to the bottom and top surfaces of the cave.

3. The method for constructing concrete bored piles in areas with strong karst development according to claim 1, characterized in that: When making the fiberglass sleeve in S2, its vertical joints need to be connected, which includes S2.1: Inject epoxy resin glue into the locking groove of the sleeve; S2.2: Expand the fiberglass sleeve and wrap the steel cage; S2.3: After accurate positioning, temporarily fix the fiberglass sleeve with a fastening tape; S2.4: Use stainless steel self-tapping screws to tighten the sleeve lock every 150mm.

4. The method for constructing concrete cast-in-place piles in areas with strong karst development according to claim 1, characterized in that: In S2, the fiberglass sleeve is circumferentially provided with a limiter, which is a hook-shaped structure, including a limit seat provided on the fiberglass sleeve and a hook portion provided on the limit seat for grabbing the spiral hoop of the steel cage.

5. The method for constructing concrete cast-in-place piles in areas with strong karst development according to claim 4, characterized in that: In S2, the upper and lower positions of the limit seat relative to the glass fiber sleeve are adjustable and fixed once by fasteners, and then reinforced twice by structural adhesive and the glass fiber sleeve after the first fixation.

6. The method for constructing concrete bored piles in areas with strong karst development according to claim 5, characterized in that: The fiberglass sleeve is provided with a vertical adjustment groove for installing a limit seat. The limit seat includes an inner pressure plate and an outer pressure plate respectively arranged on the inner and outer walls of the fiberglass sleeve. The inner pressure plate is slidably arranged on the adjustment groove, and the fastener passes through the outer pressure plate and is threadedly connected and adapted with the inner pressure plate.

7. The method for constructing concrete bored piles in areas with strong karst development according to claim 6, characterized in that: A limiting column is arranged at the center of the inner surface of the inner pressure plate, the hook is provided with a through hole adapted for sliding connection with the limiting column, and the hook and the inner pressure plate are also elastically connected via a spring sleeved on the outer periphery of the limiting column.

8. The method for constructing concrete bored piles in areas with strong karst development according to claim 6, characterized in that: The length of the inner pressure plate is greater than the length of the adjustment slot, so that the adjustment slot is always in a shielded state during the upward and downward sliding process of the inner pressure plate.

9. The method for constructing concrete bored piles in areas with strong karst development according to claim 6, characterized in that: The outer pressure plate is made of glass fiber material, and the inner pressure plate and the hook are made of aluminum alloy material.

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