Karst region perfusion pile construction method

Abstract

The application discloses a kind of karst area cast-in-place pile construction methods, including steps: after cast-in-place pile hole forming, the bucket-shaped plastic water bag that is matched with pile hole diameter and depth is set on pile top steel casing, and the opening of the plastic water bag is upwards, and bottom end extends into pile hole;Cement slurry is injected into the plastic water bag, so that plastic water bag is filled along the depth direction of pile hole with cement slurry and sinks, extrudes and discharges the slurry in the hole outside the bag, until cement slurry fills the plastic water bag;Reinforcing cage is lowered from the opening of the plastic water bag into the pile hole;Tubing is inserted into the bottom of the plastic water bag and poured with concrete, so that the concrete extrudes and replaces the cement slurry in the plastic water bag, and the cement slurry is discharged from the top of the plastic water bag, and the above construction method improves construction efficiency and improves pile quality.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, and in particular to a method for constructing cast-in-place piles in karst areas. Background Technology

[0002] Karst areas are characterized by complex geological structures such as caves, fissures, solution channels, and underground rivers. The strata are unstable and groundwater is frequently active. During the construction of cast-in-place piles, problems such as borehole instability, borehole collapse, grout leakage, and difficulty in controlling sediment are very likely to occur. Therefore, the construction of cast-in-place piles in karst areas has always been a key and difficult point in foundation engineering.

[0003] Current cast-in-place pile construction typically employs a mud slurry wall protection technique. This involves injecting mud slurry into the borehole during its formation, using the mud slurry pressure to balance groundwater pressure and soil lateral pressure, and forming a mud cake on the borehole wall surface to maintain stability. However, this traditional mud slurry wall protection technique has the following drawbacks in karst environments: On the one hand, the effectiveness of traditional mud wall protection is greatly affected by the properties of the mud. Parameters such as the specific gravity, viscosity, sand content and water loss of the mud are difficult to control stably. Especially in strata with developed karst fissures, the mud is prone to leakage, dilution or performance fluctuation, which leads to a decrease in the mud wall protection ability and then causes borehole wall collapse or local instability.

[0004] On the other hand, the underground caves and fissures in karst areas are highly interconnected. During the cleaning and concrete pouring process, cave bursts, mud loss, and changes in the liquid level inside the hole can easily occur, making it difficult to completely remove the sediment at the bottom of the hole. This results in mud and concrete mixing, which can easily lead to quality defects such as mud inclusion, slag inclusion, necking, and broken piles, seriously affecting the quality and bearing capacity of cast-in-place piles.

[0005] Furthermore, traditional mud-wall construction typically requires repeated hole cleaning to meet the required sediment thickness at the bottom of the hole. However, repeated cleaning not only results in long construction cycles and high costs, but also, in complex karst formations, mud disturbance can further reduce the stability of the hole wall, increasing the risk of hole collapse. Simultaneously, during concrete pouring, the mud comes into direct contact with the concrete, making it difficult to completely remove and potentially leading to the formation of mud cake layers in localized areas of the pile, thus affecting the integrity of the pile. Summary of the Invention

[0006] The purpose of this invention is to overcome the defects of the prior art and provide a method for constructing cast-in-place piles in karst areas. By isolating the piles with plastic water bags, replacing the mud with cement slurry, and replacing the cement slurry with concrete extrusion, reliable wall protection, thorough mud isolation, and stable pile quality are achieved. This method is suitable for karst areas with developed caves and unstable geology.

[0007] To achieve the above objectives, the technical solution adopted in this invention is a method for constructing cast-in-place piles in karst areas, comprising the following steps: Step 1: After the pile hole is formed, a barrel-shaped plastic water bag matching the diameter and depth of the pile hole is placed on the steel casing at the top of the pile, with the opening of the plastic water bag facing upward and the bottom end extending into the pile hole. Step 2: Inject cement slurry into the plastic water bag, causing the plastic water bag to sink along the depth of the pile hole as the cement slurry fills it, squeezing out the mud slurry outside the bag and inside the pile hole until the plastic water bag is filled with cement slurry; Step 3: Lower the steel cage into the pile hole through the opening of the plastic water bag; Step 4: Insert the conduit into the bottom of the plastic water bag and pour in concrete to squeeze and displace the cement slurry inside the plastic water bag, and allow the cement slurry to be discharged from the top of the plastic water bag.

[0008] A further improvement of the karst area cast-in-place pile construction method of the present invention is that, after performing step 2 above and before performing step 3 above, the residual mud between the plastic water bag and the pile hole wall is pumped out, so that the plastic water bag adheres tightly to the pile hole wall to form a cement slurry film to protect the wall.

[0009] A further improvement of the karst area cast-in-place pile construction method of the present invention is that, when performing step 3 above, a protective sleeve is wrapped around the bottom of the reinforcing cage, and spacers are placed at intervals around the reinforcing cage.

[0010] A further improvement of the karst area cast-in-place pile construction method of the present invention is that, before performing step 4 above and after performing step 3 above, a pressing structure is set at the steel casing at the top of the pile to press the top of the plastic water bag tightly against the steel casing, so as to seal the gap between the top of the plastic water bag and the pile hole wall.

[0011] A further improvement of the karst area cast-in-place pile construction method of the present invention is that, when performing step 2 above, the density of the cement slurry is made greater than that of the mud slurry, and when performing step 4 above, the density of the concrete is made greater than that of the cement slurry.

[0012] Compared with the prior art, the advantages of the present invention are: 1. Reliable wall protection, preventing collapse and gushing: The cement slurry and mud are separated by a barrel-shaped plastic water bag. The cement slurry fills and sinks, squeezing out the mud outside the bag. After the mud is pumped out of the gap, a continuous cement slurry film is formed to protect the wall. The double isolation prevents the mud from flowing into the cave and the collapse of the hole wall, which is suitable for complex geology in karst areas.

[0013] 2. Thorough mud isolation and high pile quality: The plastic water bag blocks the mud outside the bag. When the concrete is poured, the density difference is used to squeeze and replace the cement slurry in the bag from bottom to top and discharge it from the top. There is no mud residue in the pile body, avoiding problems such as mud inclusion, broken piles and excessive sediment.

[0014] 3. High construction efficiency and strong applicability: No need for long-term mud circulation and repeated hole cleaning, simplifying procedures and shortening construction period; the bottom of the steel cage is equipped with a protective sleeve and the surrounding area is equipped with pads, and the top of the bag is pressed tightly and sealed, which effectively avoids water bag damage and mud backflow, and the construction stability is good. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a cross-sectional view of the karst area cast-in-place pile construction of the present invention.

[0017] Figure 2 This is a top view of the karst area cast-in-place pile construction of the present invention.

[0018] In the diagram: 1. Pit wall; 2. Plastic water bag; 3. Reinforcing cage; 4. Cement grout; 5. Drainage hole; 6. Steel casing; 7. Pumping pipe. Detailed Implementation

[0019] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0020] The construction method of cast-in-place piles in karst areas according to the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] Please see Figures 1-2 As shown, the construction method for cast-in-place piles in karst areas includes the following steps: Step 1: After the pile hole is formed, a barrel-shaped plastic water bag 2 that matches the diameter and depth of the pile hole is placed on the steel casing 6 at the top of the pile, with the opening of the plastic water bag 2 facing upward and the bottom end extending into the pile hole. Step 2: Inject cement slurry 4 into the plastic water bag 2, so that the plastic water bag 2 sinks along the depth direction of the pile hole as it is filled with cement slurry 4, squeezing out the mud in the pile hole outside the bag until the cement slurry 4 fills the plastic water bag 2. Step 3: Lower the steel cage 3 into the pile hole through the opening of the plastic water bag 2; Step 4: Insert the conduit into the bottom of the plastic water bag 2 and pour in concrete so that the concrete squeezes and displaces the cement slurry 4 inside the plastic water bag 2, and the cement slurry 4 is discharged from the top of the plastic water bag 2.

[0022] Specifically, a drainage hole 5 is provided on one side of the top of the pile hole, and the drainage hole 5 is connected to the sewage tank.

[0023] By setting a drainage hole 5 at the top of the pile hole that connects to the sewage tank, a discharge channel is provided for the mud squeezed out by the plastic water bag 2, thereby improving the replacement efficiency of the mud in the pile hole and reducing the impact of mud retention on the adhesion of the plastic water bag 2 to the pile hole wall 1.

[0024] Specifically, the plastic water bag 2 is made of polyethylene with a thickness of 0.3mm. It is tough, has good impermeability, and is not easily punctured by cement slurry 4 or steel cage 3.

[0025] Specifically, when performing step 2 above, the grouting pipe of the cement slurry 4 is inserted into the bottom of the plastic water bag 2 for grouting.

[0026] By inserting the grouting pipe of cement grout 4 into the bottom of the plastic water bag 2 for grouting, the risk of cement grout 4 falling from a height and causing impact damage to the plastic water bag 2 is reduced, and the squeezing and replacement effect of the mud outside the bag is improved.

[0027] Preferably, after performing step 2 above and before performing step 3 above, the residual mud between the plastic water bag 2 and the pile hole wall 1 is pumped out, so that the plastic water bag 2 adheres tightly to the pile hole wall 1 to form a cement slurry 4 film to protect the wall.

[0028] Specifically, after performing step 2 above, the residual mud between the plastic water bag 2 and the pile hole wall 1 is pumped out by the water pumping pipe 7 pre-embedded in the pile hole in conjunction with the suction device, so that the plastic water bag 2 adheres to the pile hole wall 1 under negative pressure to form a continuous cement slurry 4 film to protect the wall.

[0029] By pumping out the residual mud between the plastic water bag 2 and the pile hole wall 1, the plastic water bag 2 and the pile hole wall 1 are made to fit tightly together, thereby enhancing the support effect on the pile hole wall 1 and reducing the risk of hole collapse and cavern inrush in the karst fissure area.

[0030] Preferably, when performing step 3 above, a protective sleeve is wrapped around the bottom of the reinforcing cage 3, and spacers are placed around the reinforcing cage 3 at intervals.

[0031] Specifically, the protective sleeve covers the sharp part at the bottom of the steel cage 3 to reduce the risk of the steel cage 3 scratching or puncturing the plastic water bag 2 during the lowering process; the pads are arranged at intervals around the circumference of the steel cage 3 to maintain a distance between the steel cage 3 and the plastic water bag 2.

[0032] By covering the bottom of the steel cage 3 with a protective sleeve and setting pads around the steel cage 3, the risk of the plastic water bag 2 being damaged during the lowering of the steel cage 3 is reduced, and the situation of the steel cage 3 being damaged due to direct collision with the pile hole wall 1 is reduced.

[0033] Preferably, before performing step 4 above and after performing step 3 above, a pressing structure is set at the steel casing 6 at the top of the pile to press the top of the plastic water bag 2 against the steel casing 6 to seal the gap between the top of the plastic water bag 2 and the pile hole wall 1.

[0034] By setting up a compression structure to seal the top of the plastic water bag 2, the risk of backflow of cement slurry 4 inside the plastic water bag 2 through the gap between the plastic water bag 2 and the pile hole wall 1 during concrete pouring is reduced, so as to ensure that the cement slurry 4 is discharged along the top of the plastic water bag 2 and maintain the stable support effect of the plastic water bag 2 on the pile hole wall 1.

[0035] Specifically, the clamping structure includes a telescopic rod and arc-shaped pressure plates connected to both ends of the telescopic rod. The arc-shaped pressure plates are adapted to the steel casing 6. By extending the telescopic rod, the two arc-shaped pressure plates abut against the inner walls of the opposite sides of the steel casing 6, and the top of the plastic water bag 2 is clamped between the arc-shaped pressure plates and the steel casing 6.

[0036] Preferably, when performing step 2 above, the density of the cement slurry 4 is greater than that of the mud slurry, and when performing step 4 above, the density of the concrete is greater than that of the cement slurry 4.

[0037] By controlling the density relationship between cement slurry 4, mud slurry and concrete, the density difference is used to achieve the step-by-step replacement of mud slurry 4 and concrete, thereby improving the replacement efficiency and reducing the probability of mixing between different media.

[0038] It should be noted that the structures, proportions, sizes, etc., illustrated in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to facilitate understanding and reading. They are not intended to limit the scope of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and purpose of the invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for constructing cast-in-place piles in karst areas, characterized in that, Including the following steps: Step 1: After the pile hole is formed, a barrel-shaped plastic water bag matching the diameter and depth of the pile hole is placed on the steel casing at the top of the pile, with the opening of the plastic water bag facing upward and the bottom end extending into the pile hole. Step 2: Inject cement slurry into the plastic water bag, causing the plastic water bag to sink along the depth of the pile hole as the cement slurry fills it, squeezing out the mud slurry outside the bag and inside the pile hole until the plastic water bag is filled with cement slurry; Step 3: Lower the steel cage into the pile hole through the opening of the plastic water bag; Step 4: Insert the conduit into the bottom of the plastic water bag and pour in concrete to squeeze and displace the cement slurry inside the plastic water bag, and allow the cement slurry to be discharged from the top of the plastic water bag.

2. The method for constructing cast-in-place piles in karst areas as described in claim 1, characterized in that, After performing step 2 above and before performing step 3 above, the residual mud between the plastic water bag and the pile hole wall is pumped out, so that the plastic water bag adheres tightly to the pile hole wall to form a cement slurry film to protect the wall.

3. The method for constructing cast-in-place piles in karst areas as described in claim 1, characterized in that, When performing step 3 above, a protective sleeve is wrapped around the bottom of the reinforcing cage, and spacers are placed around the reinforcing cage at intervals.

4. The method for constructing cast-in-place piles in karst areas as described in claim 1, characterized in that, Before performing step 4 above, and after performing step 3 above, a pressing structure is set at the steel casing at the top of the pile to press the top of the plastic water bag against the steel casing, so as to seal the gap between the top of the plastic water bag and the pile hole wall.

5. The method for constructing cast-in-place piles in karst areas as described in claim 1, characterized in that, When performing step 2 above, the density of the cement slurry is made greater than that of the mud slurry. When performing step 4 above, the density of the concrete is made greater than that of the cement slurry.

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