Pile forming method for multi-bead karst cave bridge pile foundation in karst landform karst rock development area

Abstract

The invention discloses a pile-forming method for a multi-bead karst cave bridge pile foundation in a karst landform karst rock development area. The pile-forming method comprises the following steps: forming an embedding hole to embed and fix a steel casing; a first-diameter drill bit is used for conducting pile hole operation downwards in the burying hole, and the n1th karst cave is drilled through; the second-diameter drill bit is replaced to continue to conduct pile hole operation downwards, and the n2th karst cave is drilled through; a third-diameter drill bit is replaced to continue to conduct pile hole operation downwards, and the n3 karst cave is drilled through; a fourth-diameter drill bit is replaced to continue to conduct pile hole operation downwards, the n4 karst cave is drilled through, and hammer punching is conducted repeatedly till the designed elevation is reached; wrapping the manufactured reinforcement cage with geotechnical cloth, and hoisting the reinforcement cage into the pile hole; and concrete is poured into the pile hole at a constant speed, so that pile forming of the bridge pile foundation is completed. The four drill bits with different diameters are adopted for conducting karst cave pile foundation hole forming operation, the pile holes are repeatedly filled with rubbles, clay and cement, the hole walls are stabilized, collapse is avoided, the all-steel pile casing follow-up construction technology is replaced, and the construction cost is greatly saved.

Description

TECHNICAL FIELD

[0001] The present application relates to the construction technology of pile forming process of bridge pile foundation, and particularly relates to a method for forming piles of multi-bead karst cave bridge pile foundation in karst landform karst rock development area. BACKGROUND

[0002] For the karst landform karst rock development area with large scale, the karst cave is a multi-layer (bead-shaped) karst cave, and the bridge pile foundation construction is difficult, and the geological advanced drilling can only reflect the local position geological condition of each pile and cannot completely reflect the whole pile condition. In the actual construction process, almost every bridge pile foundation encounters the phenomena of hole collapse, drilling deflection, slurry leakage, and drill pipe sticking during the driving process, and the conventional construction method adopts the measures of throwing and filling yellow mud, stone, yellow mud with stone, pouring low-grade plain concrete, following up steel casing, temporary steel casing, and stratum grouting process to prevent safety accidents caused by karst caves. At present, in order to prevent the above safety accidents, one is to use inner and outer steel casings, and the method of following up the inner steel casing for construction will cause high cost due to the permanent burying of the steel casing; the other is to fill the drilling area with concrete, but the construction method needs to wait for the concrete to solidify and have a certain strength, and the large amount of use of concrete will also increase the cost. Therefore, it is necessary to improve the construction method of bridge pile foundation pile forming in the multi-bead karst cave of karst rock development area to solve the above problems. SUMMARY

[0003] To solve the above problems, the present application provides a method for forming piles of multi-bead karst cave bridge pile foundation in karst landform karst rock development area, and the specific technical scheme is as follows: A method for forming piles of multi-bead karst cave bridge pile foundation in karst landform karst rock development area, comprising the following steps: A buried hole is opened to bury a fixed steel casing; A first diameter drill bit is used to perform pile hole operation downward in the buried hole, and drill through the nth1 karst cave; A second diameter drill bit is replaced to continue the pile hole operation downward, and drill through the nth2 karst cave; A third diameter drill bit is replaced to continue the pile hole operation downward, and drill through the nth3 karst cave; A fourth diameter drill bit is replaced to continue the pile hole operation downward, and drill through the bottom layer karst cave, and repeatedly hammer until the design elevation; The prepared steel reinforcement cage is wrapped with geotextile, and hoisted into the pile hole; The concrete is uniformly poured into the pile hole to complete the pile forming of the bridge pile foundation.

[0004] Further, the opening diameter of the buried hole is 1.45 times of the design pile diameter.

[0005] Further, the first diameter is 1.38 times of the design pile diameter, and n1 is 1 or 2.

[0006] Further, the second diameter is 1.22 times of the design pile diameter, and n2 is 3 or 4.

[0007] Further, the third diameter is 1.11 times of the design pile diameter, and n3 is 5 or 6.

[0008] Further, the fourth diameter is 2 cm larger than the design pile diameter, and n3 is 7 or 8.

[0009] Further, the outer diameter formed by winding the geotextile is 10-15 cm larger than the outer diameter of the reinforcement cage, and the reinforcement cage is hoisted into the pile hole at one time.

[0010] Further, when the pile hole operation is performed, a mixture of clay, stone blocks and cement is poured into the pile hole in proportion.

[0011] Further, the mass ratio of the clay, stone blocks and cement poured into the pile hole is 1:0.5-1.5:0.5.

[0012] Further, when the rock saturation compressive strength of the karst cave is not higher than 14Mpa, the mass ratio of the clay, stone blocks and cement is 1:1.5:0.5, and when the rock saturation compressive strength of the karst cave is greater than 14Mpa, the mass ratio of the clay, stone blocks and cement is 1:0.5:0.5.

[0013] The present application has the following beneficial effects: (1) Four different diameter drill bits are used for pile foundation hole forming operation in karst landform limestone development area multi-bead karst cave, to eliminate possible collapse problems in the construction process, effectively pass through different size karst caves, and ensure that the formed pile diameter is not less than the design value when reaching the design elevation value of the pile bottom; (2) Multiple variable diameter drilling, repeated filling of the pile hole with stone blocks, clay and cement, stable hole wall, solve the multi-bead karst cave complex geological condition hole forming technology, replace the full steel casing following construction process, save a lot of steel, greatly save the construction cost; (3) The reinforcement cage and pouring guide pipe are hoisted integrally at one time, reducing the construction time; the geotextile is wrapped to avoid unstable hole wall, collapse into the concrete, affecting the pile foundation quality and monitoring results. DETAILED DESCRIPTION

[0014] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0015] In the description of the present application, it is to be understood that the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0016] In the description of the present application, it should be noted that unless otherwise specifically defined and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral connection, it can be mechanical connection, or electrical connection or can communicate with each other, it can be directly connected, or indirectly connected through intermediate medium, it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0017] Specifically, before the bridge pile foundation is constructed in the construction area, geological exploration work should be done first, and the number of karst caves / number of layers, the height of the karst cave, the rock saturated compressive strength and other data of the construction area should be mastered in detail to form a matching construction scheme or method.

[0018] The design depth of the pile hole of the construction area of the present application is taken as an example to reach the position between the 7th and 8th karst caves, and the distance between the 7th and 8th karst caves is greater than 5m, and the rock saturated compressive strength R c is greater than 14Mpa.

[0019] A multi-bead karst cave bridge pile foundation construction method in a karst landform karst development area, comprising the following steps: S1: setting a buried hole to bury a fixed steel casing; S2: using a first diameter drill bit to drill down in the buried hole and drill through the nth cave; S3: replacing the second diameter drill bit to continue drilling down and drilling through the n2th cave; S4: replacing the third diameter drill bit to continue drilling down and drilling through the n3th cave; S5: replacing the fourth diameter drill bit to continue drilling down and drilling through the n4th cave, and repeatedly hammering until the design elevation; S6: wrapping the prepared steel reinforcement cage with geotextile and hoisting it into the pile hole; S7: uniformly pouring concrete into the pile hole to complete the bridge pile foundation construction.

[0020] In the construction scheme, when the pile hole operation is performed, a mixture of clay, stone blocks and cement is poured into the pile hole in proportion, and the mixture is extruded by a drill bit to the inner wall of the karst cave in the pile hole to form a stable inner wall.

[0021] The mass ratio of the clay, stone blocks and cement poured into the pile hole is 1:0.5-1.5:0.5, which depends on the rock saturated compressive strength of the karst cave. In the area with lower strength, the proportion of stone blocks is preferably increased.

[0022] Preferably, the rock saturated compressive strength R of the karst cave is not higher than 14 MPa. c When the rock saturated compressive strength R of the karst cave is not higher than 14 MPa, the mass ratio of the clay, stone blocks and cement is 1:1.5:0.5. c When the rock saturated compressive strength R of the karst cave is higher than 14 MPa, the mass ratio of the clay, stone blocks and cement is 1:0.5:0.5.

[0023] The specific construction scheme is as follows: Before the S1 step, the stratum of the pile hole site and the impact drill equipment needs to be compacted or replaced to ensure the stability of the stratum of the pile hole site and the equipment. The pile hole coordinates are measured and laid out to ensure the accuracy of the pile hole site.

[0024] In the S1 step, a buried hole is formed in the shallow overburden layer, the opening diameter of the buried hole is 1.45 times the design pile diameter, and a steel casing is fixed in the buried hole to support the hole wall of the buried hole to prevent collapse during subsequent drilling operations.

[0025] In the S2 step, the first diameter of the drill bit is 1.38 times the design pile diameter, and the drill bit with the first diameter is used to form a hole to pass through the first and second karst caves under the shallow overburden layer. While drilling, a mixture of clay, stone blocks and cement is poured into the pile hole.

[0026] According to the geological exploration, the rock saturated compressive strength of the first and second karst caves is less than 14 MPa, and the mass ratio of the clay, stone blocks and cement poured into the pile hole is 1:1.5:0.5. After pouring the mixture, the pile hole is repeatedly punched to extrude the mixture to the inner wall of the karst cave in the pile hole. The mixture is stirred with the inner wall of the karst cave to form a stable state and reach a certain strength, thereby ensuring that the pile hole will not collapse.

[0027] In the S3 step, the second diameter of the replaced drill bit is 1.22 times the design pile diameter, and the drill bit with the second diameter is used to form a hole to continue to pass through the third and fourth karst caves. While drilling, a mixture of clay, stone blocks and cement is poured into the pile hole.

[0028] According to the geological exploration, the rock saturated compressive strength of the 3rd and 4th karst caves is not higher than 14Mpa, the mass ratio of clay, stone and cement poured into the pile hole is 1:1.5:0.5; after pouring the mixture, the pile hole is repeatedly punched, so that the mixture is extruded to the inner wall of the karst cave in the pile hole, the mixture is stirred with the inner wall of the karst cave to form a stable state and reach a certain strength, so as to ensure that the pile hole will not appear the phenomenon of hole collapse and the like.

[0029] In the S4 step, the third diameter of the replaced drill bit is 1.11 times the designed pile diameter, the hole forming operation is carried out with the drill bit of the diameter, and the downward passing through the 5th and 6th karst caves is continued; at the same time of the drilling operation, the mixture of clay, stone and cement is poured into the pile hole.

[0030] According to the geological exploration, the rock saturated compressive strength of the 5th and 6th karst caves is higher than 14Mpa, the mass ratio of clay, stone and cement poured into the pile hole is 1:0.5:0.5; after pouring the mixture, the pile hole is repeatedly punched, so that the mixture is extruded to the inner wall of the karst cave in the pile hole, the mixture is stirred with the inner wall of the karst cave to form a stable state and reach a certain strength, so as to ensure that the pile hole will not appear the phenomenon of hole collapse and the like.

[0031] In the S5 step, the fourth diameter of the replaced drill bit is 2cm larger than the designed pile diameter, the hole forming operation is carried out with the drill bit of the diameter, and the downward passing through the 7th karst cave is continued; at the same time of the drilling operation, the mixture of clay, stone and cement is poured into the pile hole.

[0032] According to the geological exploration, the rock saturated compressive strength of the 7th karst cave is higher than 14Mpa, the mass ratio of clay, stone and cement poured into the pile hole is 1:0.5:0.5; after pouring the mixture, the pile hole is repeatedly punched, so that the mixture is extruded to the inner wall of the karst cave in the pile hole, the mixture is stirred with the inner wall of the karst cave to form a stable state and reach a certain strength, so as to ensure that the pile hole will not appear the phenomenon of hole collapse and the like.

[0033] According to the pile hole design depth, the pile hole depth is located between the 7th and 8th karst caves, and the geological radar is used to detect that there is no karst cave in the range of 5m below the bottom (design elevation) of the pile hole.

[0034] In the S6 step, the outer diameter of the geotextile wound is 10-15cm larger than the outer diameter of the steel reinforcement cage, the geotextile is tightly wrapped on the steel reinforcement cage and is fixed with a binding wire.

[0035] In order to prevent the collapse of the pile hole wall, the full-length (the design depth of the pile hole) steel reinforcement cage and the pouring guide pipe are integrally hoisted into the pile hole at one time. It is measured and inspected that the pile hole wall is stable and has no collapse, the underwater concrete pouring operation is carried out at a uniform speed, and the concrete loss phenomenon is monitored at any time.

[0036] It should be noted that when the number of karst caves and the number of layers of the construction area and the height of the karst caves are different, the number of karst caves drilled by the four diameters of drill bits can be appropriately adjusted and distributed; when the rock saturated compressive strength of the adjacent two karst caves is obviously segmented (the upper layer R c ≤14Mpa, and the lower layer R c >14Mpa), different diameter drill holes should be used for hole forming operation in the upper and lower karst caves of the segment; when the upper part of the rock saturated compressive strength of a single karst cave R c ≤14Mpa, and the lower part R c >14Mpa, the mass ratio of clay, sheet stone and cement poured into the pile hole is 1:1:0.5, so that the inner wall of the karst cave in the pile hole can reach a certain strength, and the pile hole will not appear the phenomenon of hole collapse.

[0037] Although the embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made thereto without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for constructing bridge pile foundations for multi-bead karst caves in karst landform areas, characterized in that, Includes the following steps: Drill holes to embed and fix the steel casing; Using a drill bit of the first diameter, the pile hole is drilled downwards in the buried hole, and the n1th karst cave is drilled through. Replace with a second diameter drill bit and continue drilling downwards to create a pile hole, and drill through the n2th karst cave; Replace with a third diameter drill bit and continue drilling downwards to create a pile hole, and drill through the n3rd karst cave; Replace with the fourth diameter drill bit and continue drilling downwards to drill through the n4th karst cave, repeatedly hammering the drill until the design elevation is reached; Wrap the fabricated steel cage with geotextile and hoist it into the pile hole; Concrete is poured into the pile hole at a uniform speed to complete the bridge pile foundation.

2. The bridge pile foundation pile formation method according to claim 1, characterized in that, The diameter of the buried hole is 1.45 times the designed pile diameter.

3. The bridge pile foundation pile formation method according to claim 1, characterized in that, The first diameter is 1.38 times the designed pile diameter, and n1 is 1 or 2.

4. The bridge pile foundation pile formation method according to claim 1, characterized in that, The second diameter is 1.22 times the designed pile diameter, and n2 is 3 or 4.

5. The method for constructing bridge pile foundations according to claim 1, characterized in that, The third diameter is 1.11 times the designed pile diameter, and n3 is 5 or 6.

6. The method for constructing bridge pile foundations according to claim 1, characterized in that, The fourth diameter is 2cm larger than the designed pile diameter, and n4 is 7 or 8.

7. The method for constructing bridge pile foundations according to claim 1, characterized in that, The outer diameter formed by the geotextile winding is 10-15cm larger than the outer diameter of the steel cage, and the steel cage is hoisted into the pile hole in one go.

8. The method for constructing bridge pile foundations according to any one of claims 1 to 7, characterized in that, When drilling pile holes, a mixture of clay, rubble, and cement is poured into the pile hole in a specific ratio.

9. The method for constructing bridge pile foundations according to claim 8, characterized in that, The mass ratio of clay, rubble, and cement poured into the pile hole is 1:0.5 to 1.5:0.

5.

10. The method for constructing bridge pile foundations according to claim 9, characterized in that, When the saturated compressive strength of the rock in the karst cave is not higher than 14 MPa, the mass ratio of clay, boulders and cement is 1:1.5:0.

5. When the saturated compressive strength of the rock in the karst cave is greater than 14 MPa, the mass ratio of clay, boulders and cement is 1:0.5:0.5.