Pile foundation hole forming process for easy-to-collapse stratum

Abstract

A pile foundation hole forming process for an easy-to-collapse stratum comprises the steps that a rotary drilling machine is used for sequentially pressing an outer pile casing and an inner pile casing of a pile head into the ground, then a sand bailing hopper with the small diameter is used for excavating a guide hole in the stratum, clay is added into the hole after the guide hole is excavated, and then an extrusion wall-fixing drill bit is replaced for rotary drilling; clay and water are stirred into slurry through the extrusion wall-fixing drill bit, then the slurry is mixed on soil on the hole wall, then the hole wall is expanded and compacted, and a clay slurry film is formed on the hole wall. By means of the hole forming technology, the pile hole which is high in compactness and provided with the high-precision retaining wall can be excavated in the unconsolidated stratum, the pile hole is high in strength and not prone to hole collapse and hole shrinkage, and concrete does not need to be poured immediately, so that all work can be arranged more orderly, more stable assembly line work is formed, and the construction efficiency is improved; extra slurrying is not needed, so that the construction cost and labor are reduced; and sediment and hole wall defects can be effectively reduced, so that the generation of concrete over-filling in the later period is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to pile foundation construction, in particular to a drill bit and a hole forming process for forming a pile foundation hole in loose collapsed stratum using a rotary drilling machine. BACKGROUND

[0002] Rotary drilling is a very common method for pile foundation construction, the drill bits used in rotary drilling include screw drill bits, barrel drill bits and rotary drill bits. For good cohesive stratum, dry drilling or clean water drilling process can be used; while for loose collapsible stratum such as sand stratum, silt stratum and fissure water-bearing stratum, static mud wall protection drilling process must be used, which requires pouring mud prepared on demand into the hole to support the hole wall. However, static mud wall protection drilling process requires mud for hole forming and hole cleaning, which requires a large amount of mud preparation, resulting in high cost and low construction efficiency. Moreover, due to the problems of floating mud and sedimentation, and the defects such as recesses and small holes in the pile hole, a large amount of over-pouring must be implemented during concrete pouring; even so, the strength of the pile hole after rotary drilling is still low, and there is a high risk of hole collapse and hole shrinkage, so immediately after hole forming, the construction of steel reinforcement cage and concrete pouring must be carried out to complete the construction before the pile hole is damaged. At the same time, this also causes tight construction period, and the pouring construction team must enter the site as soon as possible after the rotary drilling machine leaves the site, which easily causes site confusion and congestion, so the construction teams need to have high coordination and require a large transit site, which undoubtedly increases the construction difficulty. SUMMARY

[0003] The present application aims to provide an extrusion wall stabilizing drill bit and a pile foundation hole forming process for increasing the stability of pile foundation hole forming in collapsible stratum, to reduce the construction difficulty and improve the construction efficiency.

[0004] The pile foundation hole forming process in collapsible stratum according to the present application comprises the following steps: A. Installing a pile head outer casing and pressing the pile head outer casing into the ground; B. Installing an inner casing and pressing the inner casing into the ground on the inner side of the pile head outer casing; C. Drilling a pilot hole on the inner side of the inner casing, the diameter of the pilot hole being smaller than the diameter of the required pile hole, and water being injected into the hole and the water pressure in the hole being maintained during the drilling of the pilot hole; D. Enlarging the hole and stabilizing the wall, adding clay into the pilot hole, then using the rotary drilling machine to enlarge the hole by the extrusion wall stabilizing drill bit, and injecting water into the hole during the drilling; the diameter of the extrusion wall stabilizing drill bit being equal to the diameter of the required drill hole, and the clay and water being stirred into mud during the drilling of the extrusion wall stabilizing drill bit, and the soil layer being extruded inwardly to compact the mud on the hole wall.

[0005] The extruding fixed wall drill bit comprises a drill cylinder, a connecting pipe arranged at the axis of the drill cylinder, and a partition plate arranged at the bottom of the drill cylinder; a support rod is arranged between the connecting pipe and the top of the drill cylinder, the lower part of the connecting pipe is a central shaft, the bottom end of the central shaft penetrates through the partition plate and protrudes from the bottom of the drill cylinder, an inclined cutting plate is arranged between the bottom end of the central shaft and the bottom of the drill cylinder, and a plurality of cutting plates are distributed in the circumferential direction and have an inverted conical structure; a plurality of wear-resistant heads are arranged on the bottom surface of the central shaft, the bottom edge of the drill cylinder, and the cutting plates, respectively; and a plurality of extruding strips protruding outward are arranged on the outer wall of the drill cylinder.

[0006] The pile foundation hole forming process for collapsible stratum utilizes a rotary excavator to press a pile head outer protection cylinder and an inner protection cylinder into the ground in sequence, then a sand bucket with a smaller diameter is used to drill a pilot hole in the stratum, clay is added into the hole after the pilot hole is drilled, and then a squeezing solid wall drill bit is replaced to perform rotary excavation, a drill rod of the rotary excavator is connected to a top of the connecting pipe to drive the squeezing solid wall drill bit to rotate; an upper part of the squeezing solid wall drill bit is a drill cylinder provided with squeezing strips, a lower part is an inverted cone composed of multiple cutting plates, and a middle part is a baffle for blocking mud; since a size of the squeezing solid wall drill bit is larger than a size of the pilot hole, in a drilling process of the squeezing solid wall drill bit, the cutting plates expand the pilot hole in diameter by exerting a lateral pressure on the pilot hole, and the rotary excavator drives the squeezing solid wall drill bit to rotate and agitates the clay and water in the hole to form mud with greater adhesion, and under the blocking action of the baffle, more mud is retained below the baffle, then with continuous rotation of the squeezing solid wall drill bit, part of the mud is mixed with the soil layer of the hole wall and expanded into a pile hole, and part of the mud is guided into a gap between the hole wall and an outer wall of the drill cylinder, and finally the mud is compressed on the surface of the hole wall by the squeezing strips outside the cylinder wall to form a tight and smooth clay slurry film; thus, the originally loose and collapsible soil layer becomes more compact and solid. By the pile foundation hole forming process for collapsible stratum, a pile hole with high tightness and high-precision protection wall can be drilled in a loose stratum, the pile hole has high strength and is not prone to hole collapse and hole shrinkage, the pile hole after rotary excavation can maintain stability for a long time, and concrete pouring construction does not need to be immediately performed, which not only reduces the cooperation requirements between different construction teams, but also reduces the site requirements, so that various work can be arranged in a more orderly manner to form a more stable assembly line operation; the pile hole after hole forming can wait for drilling of a subsequent pile hole, and then a pouring construction team simultaneously performs pouring construction on multiple pile holes to improve construction efficiency and reduce construction cost; in addition, the bottom of the inverted cone can exert a lateral pressure on the soil layer and make the bottom of the hole formed into an inverted cone structure, which can make sand, gravel or other impurities concentrate in the conical bottom of the pile hole, and these impurities can be more easily and completely cleaned up when reverse circulation hole cleaning is performed, and because the hole wall of the pile hole is tight and smooth, there is no concave hole on the hole wall, which can effectively reduce or even avoid occurrence of late-stage concrete overfilling; in addition, the squeezing solid wall drill bit can make the added clay into mud during rotary excavation, so that mud is not necessarily prepared by a mud preparation device, thereby reducing construction cost and labor.

[0007] Preferably, the baffle is provided with two or more mud inlet holes, and the mud inlet holes are circumferentially spaced apart on the baffle.

[0008] Preferably, the drill cylinder is provided with a plurality of flow-through holes communicating between the inner and outer sides.

[0009] Preferably, two or more flow-through holes are circumferentially spaced apart at different heights on the drill cylinder.

[0010] Preferably, several extrusion strips are arranged at different heights of the drill cylinder respectively and are spaced along the circumference.

[0011] Preferably, several extrusion strips are arranged at different heights of the drill cylinder respectively.

[0012] Preferably, the extrusion strips at adjacent heights are staggered.

[0013] Preferably, the wear-resistant head mounted on the cutting plate comprises angular stirring teeth and cylindrical air-blast heads.

[0014] Preferably, hard fragments such as sand and stone are added into the guide hole, and then the extrusion solid-wall drill is used to press the hard fragments and mud and soil into the hole wall.

[0015] Through the above hole-forming process, the hole wall can be further compacted and better mud can be formed, so as to improve the structural strength of the pile hole. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a structural schematic view of a pile head outer sleeve and inner sleeve.

[0017] Figure 2 , 3 is a structural schematic view of an extrusion solid-wall drill.

[0018] Figure 4 is a side structural schematic view of an extrusion solid-wall drill.

[0019] Figure 5 is a top structural schematic view of an extrusion solid-wall drill.

[0020] Figure 6 is a bottom structural schematic view of an extrusion solid-wall drill. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0022] ​It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back, top, bottom, inner, outer, vertical, horizontal, longitudinal, counterclockwise, clockwise, circumferential, radial, axial, etc.), the directional indications are only used to explain the relative positional relationship, motion condition, etc. between the components in a certain specific posture (as shown in the drawings), and if the specific posture changes, the directional indications will also change accordingly.

[0023] If the embodiments of the present application involve descriptions such as "first" or "second", the descriptions of "first" or "second" are only for description purposes and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" can explicitly or implicitly include at least one of the features. In addition, the technical solutions of various embodiments can be combined with each other, but must be based on the realization of ordinary skilled persons in the art, and when the combination of technical solutions contradicts each other or cannot be realized, it should be considered that the combination of technical solutions does not exist and is not within the protection scope required by the present application.

[0024] The present application provides an extrusion solid wall drill bit and a pile foundation hole forming process in a collapsible stratum.

[0025] The extrusion solid wall drill bit of the embodiment comprises a drill cylinder 1, a connecting pipe 2 arranged at the axis of the drill cylinder, and a partition plate 3 installed at the bottom of the drill cylinder; a support rod 4 is connected between the connecting pipe and the top of the drill cylinder, the lower part of the connecting pipe is a central shaft, the bottom end of the central shaft penetrates through the partition plate and protrudes from the bottom of the drill cylinder, an inclined cutting plate 5 is connected between the bottom end of the central shaft and the bottom of the drill cylinder, and a plurality of cutting plates are distributed in the circumferential direction and have an inverted conical structure; a plurality of wear-resistant heads are respectively arranged on the bottom surface of the central shaft, the edge of the bottom of the drill cylinder, and the cutting plates; and a plurality of extrusion strips 7 protruding outward are arranged on the outer wall of the drill cylinder.

[0026] The hole forming process of the embodiment comprises the following steps: A. Installing a pile head outer casing 10, and pressing the pile head outer casing into the ground; B. Installing an inner casing 20 on the inner side of the pile head outer casing, and pressing the inner casing into the ground; C. Drilling a pilot hole, drilling the pilot hole on the inner side of the inner casing, the diameter of the pilot hole being smaller than the diameter of the required pile hole, and injecting water into the hole and maintaining the water pressure in the hole during the drilling of the pilot hole, which can prevent the collapse of the pilot hole; D. Enlarging the hole and solidifying the wall, adding clay into the pilot hole, then using a rotary excavator to rotary excavate and enlarge the hole by using the extrusion solid wall drill bit, and injecting water into the hole during the drilling; the diameter of the extrusion solid wall drill bit is equal to the diameter of the required drill hole, the extrusion solid wall drill bit stirs the clay and water into mud slurry while drilling, and extrudes the soil layer inward to compact the mud slurry on the hole wall.

[0027] As shown in Figure 1 , the pile head outer casing and inner casing are pressed into the ground by the rotary excavator in turn, then a sand bucket with a smaller diameter is used to drill a pilot hole in the ground, after the pilot hole is drilled, clay is added into the hole, then the extrusion solid wall drill bit is replaced to carry out rotary excavation, the drill rod of the rotary excavator is connected to the top of the connecting pipe to drive the extrusion solid wall drill bit to rotate; as shown in Figures 2-6 , the upper part of the extrusion solid wall drill bit is a drill cylinder provided with extrusion strips, the lower part is a reverse cone composed of multiple cutting plates, and the middle part is a baffle to block the mud; since the size of the extrusion solid wall drill bit is larger than that of the pilot hole, in the process of drilling, the cutting plates gradually expand the diameter of the pilot hole by exerting a transverse pressure on the pilot hole, on the other hand, the rotary excavator drives the extrusion solid wall drill bit to rotate and agitates the clay and water in the hole to form mud with greater adhesion, and under the blocking action of the baffle, more of these muds remain below the baffle, then as the extrusion solid wall drill bit continues to rotate, part of the muds mix with the soil layer of the hole wall and expand into a pile hole, and part of the muds are guided into the gap between the hole wall and the outer wall of the drill cylinder, and finally are pressed tightly on the surface of the hole wall by the extrusion strips outside the cylinder wall to form a tight and smooth clay slurry film; thus the originally loose and collapsible soil layer becomes more compact and firm.

[0028] The extrusion solid wall drill bit is provided with a plurality of mud inlet holes 8 on the baffle 3 in a circumferential direction, so that the bubbles, water, mud or soil below the drill bit enter the inside of the drill cylinder through the mud inlet holes, avoiding excessive mud pressure below from damaging the pilot hole. In addition, the cylinder wall of the drill cylinder 1 is provided with a plurality of flow-through holes 9 communicating between the inside and the outside, because in the process of drilling, part of the excess soil will accumulate in the drill cylinder, when a certain amount of soil accumulates in the drill cylinder, the rotary excavator will drive the extrusion solid wall drill bit to move out of the hole, then the rotary excavator is repeatedly rotated in the forward and reverse directions to throw the soil in the cylinder out of the flow-through holes, and after the soil is cleaned, the drilling continues.

[0029] The extrusion solid wall drill bit is provided with a plurality of extrusion strips 7 at different heights on the drill cylinder 1 in a circumferential direction, and the extrusion strips at adjacent heights are staggered, so as to form multiple layers and multiple compactions on the hole wall, which is beneficial to improve the construction efficiency and the quality of the hole. Similarly, the flow-through holes 9 can also be provided with more than two at different heights on the drill cylinder 1 in a circumferential direction, so as to clean the soil in the drill cylinder more quickly and thoroughly. In addition, the extrusion strips 7 can be arranged between two flow-through holes in a circumferential direction, on the one hand, the structure can be more compact, thereby reducing the volume and weight of the drill bit, on the other hand, the soil thrown out of the cylinder during drilling can be quickly pressed into the hole wall, thereby better forming a slurry film on the hole wall, ensuring the tightness and smoothness of the hole wall.

[0030] The wear-resistant head installed on the cutting plate 5 includes angular stirring teeth 61 and cylindrical air-blast heads 62, because the stirring teeth can better stir the slurry. The stirring teeth 61 are arranged at the lower part of the cutting plate 5, the air-blast heads 62 are arranged at the upper part of the cutting plate 5, and the length of the stirring teeth is greater than that of the air-blast heads. The wear-resistant head installed on the drill cylinder is an air-blast head, and the wear-resistant head installed at the bottom of the central shaft is a stirring tooth.

[0031] In the hole-forming process, besides adding clay into the hole, sand, stone and other hard fragments can also be added into the pilot hole according to the structure and characteristics of the stratum, and then the hard fragments, slurry and soil are mixed and pressed into the hole wall by the extruding solid wall drill bit, so as to improve the structural strength of the pile hole.

[0032] The above description is only the preferred embodiments of the present application, and does not limit the patent scope of the present application. Any equivalent structural transformation, direct / indirect application in other related technical fields, or the like, which is made according to the inventive concept of the present application and the content of the specification and drawings, is included in the patent protection scope of the present application.

Claims

1. A drilling process for pile foundations in easily collapsible strata, characterized in that... Includes the following steps: A. Installation of the outer casing (10) of the pile head: Press the outer casing of the pile head into the ground; B. Inner casing (20) installation: Press the inner casing into the ground inside the outer casing of the pile head; C. Drilling of pilot holes: Drill pilot holes inside the inner casing. The diameter of the pilot holes is smaller than the diameter of the required pile holes. During the drilling of pilot holes, water is injected into the holes and the water pressure inside the holes is maintained. D. Hole enlargement and wall stabilization: Clay is added into the pilot hole, and then the rotary drilling machine enlarges the pilot hole by using a wall-stabilizing extrusion drill bit, while water is injected into the hole during the drilling process; the diameter of the wall-stabilizing extrusion drill bit is equal to the diameter of the required borehole. While the wall-stabilizing extrusion drill bit is drilling, the clay and water are mixed into mud, and the soil layer is squeezed inward to compact the mud onto the hole wall.

2. The hole-forming process according to claim 1, characterized in that: The extrusion wall drill bit includes a drill barrel (1), a connecting pipe (2) located at the axis of the drill barrel, and a partition plate (3) installed at the bottom of the drill barrel; a support rod (4) is connected between the connecting pipe and the top of the drill barrel, the lower part of the connecting pipe is a central shaft, the bottom end of the central shaft passes through the partition plate and protrudes from the bottom of the drill barrel, and an inclined cutting plate (5) is connected between the bottom end of the central shaft and the bottom of the drill barrel, and several cutting plates are distributed circumferentially and have an inverted conical structure; several wear-resistant heads are respectively installed on the bottom surface of the central shaft, the bottom edge of the drill barrel, and the cutting plates, and several outwardly protruding extrusion strips (7) are installed on the outer wall of the drill barrel.

3. The hole-forming process according to claim 2, characterized in that: The partition (3) is provided with two or more slurry inlet holes (8), and the slurry inlet holes are spaced apart on the partition along the circumference.

4. The hole-forming process according to claim 1, 2 or 3, characterized in that: The cylinder wall of the drill barrel (1) is equipped with several flow holes (9) connecting the inner and outer sides.

5. The hole-forming process according to claim 4, characterized in that: Two or more flow holes (9) are provided at different heights on the drill barrel (1) along the circumferential direction.

6. The hole-forming process according to claim 5, characterized in that: Several extrusion strips (7) are arranged at different heights along the circumference on the drill barrel (1), and the extrusion strips are arranged between two flow holes (9) in the circumference direction.

7. The hole-forming process according to claim 1, 2 or 3, characterized in that: Several extrusion strips (7) are arranged at different heights along the circumference on the drill barrel (1).

8. The hole-forming process according to claim 7, characterized in that: The extrusion strips (7) at adjacent heights are staggered.

9. The hole-forming process according to claim 1, 2 or 3, characterized in that: The wear-resistant head mounted on the cutting plate (5) includes angular agitator teeth (61) and cylindrical air gun head (62).

10. The hole-forming process according to claim 1 or 2, characterized in that: Add hard materials such as sand and stones into the pilot hole, and then use a compression wall-fixing drill bit to mix these hard materials with mud and soil and press them into the hole wall.

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