Cloth bag wrapping type cloth bag pile suitable for karst area and construction method

Abstract

The invention discloses a cloth bag wrapping type cloth bag pile suitable for a karst area and a construction method, and relates to the technical field of karst area construction. The cloth bag does not need to be completely wrapped along the pile length, the cloth bag with the needed length is wrapped according to the specific position of the karst cave, and compared with a steel casing follow-up method, the material cost is low; compared with a backfilling method and a grouting method, the problems of slurry loss, pile body necking, diameter breaking and the like can be effectively solved, the construction cost is low, the pile forming quality is good, the cloth bag diameter redundancy is utilized, poured concrete slurry reaches the karst cave position to extrude the cloth bag to form a branch disc structure, the pile foundation bearing capacity can be improved, and the pile foundation construction period is shortened. And the safety of the pile foundation in the karst area is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of construction in karst areas, and in particular to a bag-wrapped pile suitable for karst areas and a construction method. Background Art

[0002] Karst is a general term for special landforms formed by the long-term dissolution, mechanical erosion and gravity of soluble rocks in surface water and groundwater. my country is one of the countries with the most extensive distribution of karst in the world, with a total karst area of ​​more than 3.4 million square kilometers, more than one-third of the land area, and concentrated in Yunnan, Guizhou, Sichuan, Guangdong and Guangxi. With the continuous and in-depth development of the national economy, a large number of buildings are inevitably built in karst areas. When pile foundation construction is carried out in areas with developed karst, bored cast-in-place piles are widely used because they are not restricted by stratum changes, do not require pile connection and pile cutting, save steel, are suitable for large-scale projects, are safe to construct, and will not cause ground subsidence caused by pumping.

[0003] However, due to the complex hydrogeological conditions in karst areas, the spatial distribution of karst caves and earth holes is intricate, which has an extremely adverse effect on the pile foundation construction of buildings (structures). Specifically, (1) the poured concrete is very easy to lose when it encounters karst caves and other connecting channels during the pile construction process, causing huge economic losses; (2) it is easy to cause problems such as necking, diameter change, and pile breakage, which seriously affect the quality of pile construction; (3) when there are multiple karst caves and earth holes on the side of the pile, the friction resistance on the side of the pile will be reduced, resulting in insufficient bearing capacity of the pile foundation and endangering the safety of the building.

[0004] At present, the main cave treatment technologies for pile foundation construction in karst areas include backfilling, grouting and steel casing follow-up. All three methods have obvious disadvantages and limitations.

[0005] The advantage of the backfill method is that the construction cost is relatively low; the disadvantage is that the backfill material takes up a lot of space and a lot of mechanical equipment; the density of the backfill hole wall cannot be controlled and tested, and the control effect on concrete loss is poor; in addition, the impact force generated during the backfill compaction process can easily cause the hole to collapse. The backfill method is suitable for small caves, poor connectivity, and no filling or semi-filling in the cave.

[0006] The advantage of grouting is that it can fill caves and prevent soil caves from collapsing; the disadvantages are that the grouting volume is uncontrollable, the construction cost is high, and the disturbance to the groundwater flow field is large. Grouting is suitable for situations where the karst rock mass is broken, cracks are developed, and there are plastic fillings in the karst cave.

[0007] The advantages of the steel casing follow-up method are less grouting loss and good pile quality; however, the steel casing cannot be recycled and the construction cost is high; the steel casing needs to be connected in sections during construction, which is difficult to construct; in addition, the casing needs to be vibrated and lowered, which will cause great disturbance to the foundation. This method is suitable for situations where the cave is large in scale and connected to surrounding caves.

[0008] Although the existing technology has made great contributions to solving the problems faced by pile foundation construction in karst areas, it still has certain problems in terms of construction cost, difficulty, time and applicability. Therefore, it is necessary to propose a new solution to the above problems. Summary of the invention

[0009] The object of the present invention is to provide a bag-wrapped pile and a construction method suitable for karst areas, so as to solve the technical problems raised in the background technology.

[0010] To achieve the above-mentioned purpose, the present invention provides the following technical scheme: a bag-wrapped bag pile suitable for karst areas, comprising a foundation, wherein the foundation comprises a soil layer and a rock layer, wherein the rock layer is located below the soil layer, and the karst cave is located inside the rock layer; and a pile foundation, wherein the pile foundation comprises a bag, a steel cage and a concrete pile body, wherein a steel cage is arranged inside the foundation, the bag is wrapped around the outside of the steel cage, and the outside of the steel cage is grouted to form a concrete pile body after being wrapped with the bag.

[0011] Furthermore, stirrups are provided at the steel cage.

[0012] Furthermore, the top and bottom ends of the cloth bag are provided with end openings, steel wires are arranged in the end openings, and the cloth bag is fixed to the stirrups through the steel wires.

[0013] Furthermore, the cloth bag is designed with double openings at the top and bottom ends, and the cloth bag is surround-molded. The cloth bag is flat before surround-molding, and both ends of the cloth bag are fixedly connected with steel plates when it is flat.

[0014] Furthermore, the steel plate and the corresponding cloth bag are both provided with a plurality of annular openings evenly distributed from top to bottom, and bolts are inserted into the inner sides of the annular openings.

[0015] Furthermore, pile holes are formed in the soil layer, rock layer and karst cave, and the pile foundation is located inside the pile hole.

[0016] Furthermore, a grouting pipe for injecting concrete slurry is placed in the pile hole, and the grouting output position of the grouting pipe is located inside the steel cage. The cloth bag at the cave position is squeezed to form a support plate during the grouting process in the steel cage.

[0017] A bag pile construction method suitable for karst areas, comprising at least the following steps:

[0018] S1: hoist the steel cage to the pile hole and lower it to the upper end of the bag, wrap the upper end of the bag around the steel cage, tie the steel wire to the stirrups of the steel cage to fix the upper end, hoist the steel cage upward to the lower end of the bag, wrap the lower end of the bag around the steel cage, and further fix it with steel wire;

[0019] S2: After the cloth bag is wrapped around the steel cage, the steel plates and the annular openings at both ends are in corresponding positions, and bolts are inserted from bottom to top in sequence. The bolts and nuts are used to press and fix the two steel plates, and then the cloth bag is wrapped around to form a shape, completing the connection between the cloth bag and the steel cage;

[0020] S3: Lower the steel cage wrapped with cloth bags to the bottom of the pile, and inject concrete slurry into the pile hole through the grouting pipe. The concrete liquid level rises to the cave and is blocked by the cloth bags to prevent the loss of concrete. At the same time, the bulge of the cloth bags is squeezed to form a support plate, and concrete is poured to the top of the pile. After the concrete slurry solidifies and hardens, a bag pile is formed;

[0021] S4: After the construction is completed, the pile formation effect is checked. If the requirements are met, the next step of construction can be carried out.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The cloth bag of the present invention does not need to be wrapped along the entire length of the pile. According to the specific location of the cave, the cloth bag of the required length is wrapped. Compared with the steel casing follow-up method, the material cost of the present invention is low; compared with the backfill method and the grouting method, the present invention can effectively solve the problems of slurry loss, pile necking and broken diameter, etc., with low construction cost and good pile quality.

[0024] 2. The present invention utilizes the redundancy of the diameter of the cloth bag. When the poured concrete slurry reaches the location of the cave, it squeezes the cloth bag to form a "branch plate" structure, which can improve the bearing capacity of the pile foundation and ensure the safety of the pile foundation in the karst area.

[0025] 3. The cloth bags and connectors of the present invention are prefabricated in the factory. The cloth bags are wrapped around the steel cage in a closed loop by "buttoning". There are few on-site construction steps and simple operation, which can effectively save construction time and project cost and improve construction efficiency.

[0026] 4. The bag material and the strength of the joints (arrangement, model, specification, etc. of steel plates, bolts and steel wires) of the present invention can be determined and adjusted according to the pile size and the location of the cave, and has strong applicability and high reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0028] Figure 1 It is a schematic diagram of the overall construction of the present invention;

[0029] Figure 2 This is a schematic diagram of the connection of the ends of the cloth bag of the present invention;

[0030] Figure 3 This is a schematic diagram of the annular connection of the cloth bag of the present invention;

[0031] Figure 4 This is a schematic diagram of the theory of the present invention.

[0032] In the figure: 1. Soil layer; 2. Rock layer; 3. Cave; 4. Cloth bag; 5. Pile hole; 6. Grouting pipe; 7. Steel cage; 8. Concrete pile body; 9. Support plate; 10. End hole; 11. Steel wire; 12. Stirrup; 13. Steel plate; 14. Annular hole; 15. Bolt. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0034] Embodiment 1:

[0035] See also Figure 1 - Figure 4 A bag-wrapped pile suitable for karst areas includes a foundation, the foundation includes a soil layer 1 and a rock layer 2, the rock layer 2 is located below the soil layer 1, and a karst cave 3 is located inside the rock layer 2. It also includes a pile foundation, the pile foundation includes a bag 4, a steel cage 7 and a concrete pile body 8. The steel cage 7 is arranged inside the foundation, the bag 4 is wrapped around the outside of the steel cage 7, and the outside of the steel cage 7 is grouted to form a concrete pile body 8 after the bag 4 is wrapped.

[0036] Stirrups 12 are provided at the reinforcement cage 7 .

[0037] The cloth bag 4 has end openings 10 at the top and bottom ends thereof. Steel wires 11 are arranged in the end openings 10 , and the cloth bag 4 is fixed to the stirrups 12 via the steel wires 11 .

[0038] The cloth bag 4 is designed with double openings at the top and bottom, and the cloth bag 4 is formed in a surrounding manner. The cloth bag 4 is flat before the surrounding formation, and both ends of the cloth bag 4 are fixedly connected with steel plates 13 when the cloth bag 4 is flat.

[0039] The steel plate 13 and the corresponding cloth bag 4 are both provided with a plurality of annular openings 14 evenly distributed from top to bottom, and bolts 15 are inserted into the inner sides of the annular openings 14 .

[0040] Pile holes 5 are initially formed in the soil layer 1 , the rock layer 2 and the karst cave 3 , and the pile foundation is located inside the pile hole 5 .

[0041] A grouting pipe 6 for injecting concrete slurry is also placed in the pile hole 5. The grouting output position of the grouting pipe 6 is located inside the steel cage 7. The cloth bag 4 at the position of the cave 3 is squeezed to form a support plate 9 during the grouting process in the steel cage 7.

[0042] Embodiment 2:

[0043] See also Figure 1 - Figure 4 A bag pile construction method suitable for karst areas, used in the above embodiment 1, at least comprises the following steps:

[0044] S1: hoist the steel cage 7 to the pile hole 5 and lower it to the upper end of the bag 4, wrap the upper end of the bag 4 around the steel cage 7, tie the steel wire 11 to the stirrup 12 of the steel cage 7 to fix the upper end, hoist the steel cage 7 upward to the lower end of the bag 4, wrap the lower end of the bag 4 around the steel cage 7, and further fix it with the steel wire 11;

[0045] S2: After the cloth bag 4 surrounds the steel cage 7, the steel plates 13 and the annular opening 14 at both ends are in corresponding positions, and the bolts 15 are inserted from bottom to top in sequence. The bolts 15 and nuts are used to press and fix the two steel plates 13, and then the cloth bag 4 is formed around, completing the connection between the cloth bag 4 and the steel cage 7;

[0046] S3: lower the steel cage 7 wrapped with the bag 4 to the bottom of the pile, and inject concrete slurry into the pile hole 5 through the grouting pipe 6. The concrete liquid level rises to the cave 3 and is blocked by the bag 4 to prevent the loss of concrete. At the same time, the bag 4 is squeezed to form a support plate 9, and concrete is poured to the top of the pile. After the concrete slurry solidifies and hardens, a bag pile is formed;

[0047] S4: After the construction is completed, the pile formation effect is checked. If the requirements are met, the next step of construction can be carried out.

[0048] Based on the above embodiments, the following experimental description is proposed:

[0049] The pile foundation of a proposed bridge on a highway in Guizhou Province is constructed with bored cast-in-place piles. The project is located in a karst development and coal mining area. The goafs are interconnected and filled with groundwater, which makes it difficult to handle with traditional technologies. Three boreholes of different types and with increasing difficulty in handling (named No. 1, 2, and 3 respectively) were selected to carry out field tests using the technology of the present invention. The test pile parameters are shown in Table 1. The reliability and advancement of the technology of the present invention were verified by comparing the results of the treatment with the traditional technology used in the same period of the project.

[0050] Table 1 Test pile parameters

[0051] Test pile Pile length, pile diameter Location of cave / mined area Bag wrapping position Pile No. 1 25m, 2m 12.3～14.9m 10～17m Pile No. 2 35m, 2m 22～25m 18～28m Pile No. 3 43m、2m 10~16m、29.8~33.5m 7~19m、25~37m

[0052] As shown in Table 2, the use of bag pile technology in this project saved 92% of construction time and 48% of concrete usage, which can significantly improve construction efficiency and save construction costs.

[0053] Table 2 Comparison of traditional technology and bag pile technology

[0054] Technology Construction time Filling coefficient Construction costs Traditional Technology 48 hours 2.1 30,000 yuan Bag pile technology 4 hours 1.1 8000 NTD

[0055] Note: The filling coefficient is the ratio of the actual volume of concrete poured to the theoretical volume calculated based on the outer diameter of the pile.

[0056] In summary:

[0057] In order to solve the problems of high cost, long time, great difficulty and low reliability of pile construction in karst areas, inspired by the branch pile and steel casing follow-up method, the caves in karst areas are transformed from traditional "blocking and filling" to "turning waste into treasure", and flexible cloth bags are used instead of steel casings to solve the problem of concrete loss in piles, reduce construction difficulty and material costs; utilizing the caves in karst areas, the cloth bags are squeezed and expanded by slurry in the caves to realize "support plates", thereby improving the bearing capacity of pile foundations.

[0058] The length of the cloth bag used in the present invention can be reasonably arranged according to the location of the cave, and does not need to be arranged along the entire length of the pile, which can save material usage and construction costs; the cloth bag material and the strength of the connection are determined according to the force on the cloth bag calculated according to the pile size and the location of the cave, and have strong applicability and high reliability; the cloth bag construction method innovatively proposed by the present invention is simple to construct and can effectively save construction time.

[0059] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A bag-wrapped pile suitable for use in karst areas, comprising a foundation, wherein the foundation comprises a soil layer (1) and a rock layer (2), wherein the rock layer (2) is located below the soil layer (1), and the karst cave (3) is located inside the rock layer (2), characterized in that: It also comprises a pile foundation, which comprises a cloth bag (4), a steel cage (7) and a concrete pile body (8); the steel cage (7) is arranged on the inner side of the foundation, the cloth bag (4) is wrapped on the outer side of the steel cage (7), and the concrete pile body (8) is formed by grouting on the outer side of the steel cage (7) after the cloth bag (4) is wrapped.

2. The bag-wrapped pile suitable for karst areas according to claim 1, characterized in that: The steel cage (7) is provided with stirrups (12).

3. The bag-wrapped pile suitable for karst areas according to claim 2, characterized in that: The cloth bag (4) has end openings (10) at the top and bottom ends thereof, and steel wires (11) are arranged in the end openings (10). The cloth bag (4) is fixed to the stirrups (12) via the steel wires (11).

4. The bag-wrapped pile suitable for karst areas according to claim 1, characterized in that: The cloth bag (4) is designed with double openings at the top and bottom ends, and the cloth bag (4) is surround-molded. The cloth bag (4) is flat before surround-molding, and both ends of the cloth bag (4) are fixedly connected to steel plates (13) when it is flat.

5. The bag-wrapped pile suitable for karst areas according to claim 4, characterized in that: The steel plate (13) and the corresponding cloth bag (4) are both provided with a plurality of annular openings (14) evenly distributed from top to bottom, and bolts (15) are inserted into the inner sides of the annular openings (14).

6. The bag-wrapped pile suitable for karst areas according to claim 1, characterized in that: Pile holes (5) are initially formed in the soil layer (1), rock layer (2) and karst cave (3), and the pile foundation is located inside the pile hole (5).

7. The bag-wrapped pile suitable for karst areas according to claim 6, characterized in that: A grouting pipe (6) for injecting concrete slurry is also placed in the pile hole (5), and the grouting output position of the grouting pipe (6) is located inside the steel cage (7). The cloth bag (4) located at the position of the cave (3) is squeezed to form a support plate (9) during the grouting process in the steel cage (7).

8. A method for constructing bag piles of bag-wrapped type suitable for karst areas, used for the bag piles of bag-wrapped type suitable for karst areas as claimed in any one of claims 1 to 7, characterized in that: At least the following steps are included: S1: hoisting the steel cage (7) to the pile hole (5) and lowering it to the upper end of the cloth bag (4), wrapping the upper end of the cloth bag (4) around the steel cage (7), tying the steel wire (11) to the stirrup (12) of the steel cage (7) to fix the upper end, hoisting the steel cage (7) upward to the lower end of the cloth bag (4), wrapping the lower end of the cloth bag (4) around the steel cage (7), and further fixing it with the steel wire (11); S2: After the cloth bag (4) is wrapped around the steel cage (7), the steel plates (13) and the annular opening (14) at both ends are in corresponding positions, and the bolts (15) are inserted from bottom to top in sequence, and the two steel plates (13) are pressed and fixed by the combination of the bolts (15) and nuts, and the cloth bag (4) is then wrapped around to form a connection between the cloth bag (4) and the steel cage (7); S3: lowering the steel cage (7) wrapped with the cloth bag (4) to the bottom of the pile, injecting concrete slurry into the pile hole (5) through the grouting pipe (6), and the concrete liquid level rising to the cave (3) will be blocked by the cloth bag (4), so as to prevent the loss of concrete. At the same time, the cloth bag (4) will be squeezed to form a convex support plate (9), and concrete will be poured to the top of the pile. After the concrete slurry solidifies and hardens, a bag pile is formed; S4: After the construction is completed, the pile formation effect is checked. If the requirements are met, the next step of construction can be carried out.

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