A construction method for drilling a screw pile by using an adjustable screw pile drill bit structure

Abstract

The present invention belongs to the technical field of screw cast-in-place piles, and discloses a construction method for drilling a screw pile with an adjustable screw pile drill bit structure, in order to solve the problem that the existing screw pile drill bit is cut in the pebble soil layer and the strongly weathered rock layer, and the hole wall cannot form a spiral screw pile, resulting in a major quality accident. The present invention comprises (1) using a screw drill to drive the drill bit to perform forward rotation drilling to form a pile hole; (2) pouring concrete into the pile hole, and extracting the drill bit upward while pouring concrete into the pile hole; when the screw drill extracts the drill bit upward, the screw drill drives the drill bit to rotate in the opposite direction, so that a spiral groove is formed on the inner wall of the pile hole by using the drill bit; (3) after the concrete pouring is completed, a steel cage is implanted in the concrete, and the concrete fills the pile hole and the groove, and the screw cast-in-place pile is formed after the concrete solidifies.

Description

Technical Field

[0001] The invention belongs to the technical field of screw cast-in-place piles, and specifically relates to a construction method for forming screw piles by drilling an adjustable screw pile drill bit structure, which is used for the construction of screw cast-in-place piles, and is particularly suitable for the construction of screw cast-in-place piles in pebble soil layers and strongly weathered rock layers. Background Art

[0002] Screw pile, also known as screw pile, is a new type of pile with high bearing capacity, low cost, convenient construction and no environmental pollution. Compared with driven prefabricated piles, it has low construction noise, no vibration, and no impact on the constructed piles; compared with cast-in-place piles with full spiral drilling and ordinary mud wall hole formation, there is no mud pollution and soil abandonment problem. Screw pile is a new type of pile with high practical value, which applies the common sense principle of "screws are stronger than nails" in pile and pile construction. The thread of the screw pile body can greatly increase the side friction resistance of the pile body, so screw piles of the same diameter can provide higher bearing capacity than ordinary rotary bored cast-in-place piles, or, when the required bearing capacity is certain, screw piles have a smaller diameter and lower cost than ordinary rotary bored cast-in-place piles.

[0003] The main construction process of screw piles is: drilling holes with a screw drill (the drill bit is not pulled out after drilling) → pouring concrete (lifting the drill bit while pouring) → hoisting in the steel cage after pouring is completed.

[0004] The screw pile construction process is suitable for silty clay, clay, silty clay, silt, sandy soil, pebble layers with a particle size of less than 30mm, and strongly weathered rock layers.

[0005] However, during the construction of screw piles (i.e., screw cast-in-place piles), there is a problem of poor pile quality due to poor geological conditions, especially in pebble soil layers and strongly weathered rock layers. Compared with clay layers, these strata are stronger, the drilling speed of the drilling rig is slower, and repeated cutting occurs when the drill bit cuts the hole wall threads, resulting in the hole wall being cut smooth (i.e., a complete thread cannot be formed). When this happens, the screw pile loses its original design intention: it cannot provide greater lateral resistance, cannot provide greater lateral resistance, cannot meet the design bearing capacity requirements, and causes major quality accidents. Summary of the invention

[0006] In order to solve the problem that the hole wall of the existing screw pile drill bit is cut in the pebble soil layer and the strongly weathered rock layer and the spiral screw pile cannot be formed, resulting in a major quality accident, the present invention provides a construction method for drilling a screw pile with an adjustable screw pile drill bit structure, which can ensure that a threaded structure is formed in the pebble soil layer and the strongly weathered rock layer, thereby ensuring the molding quality of the screw cast-in-place pile.

[0007] In order to solve the technical problem, the technical solution adopted by the present invention is:

[0008] A construction method for forming a screw pile by drilling with an adjustable screw pile drill bit structure, which is used for the construction of screw cast-in-place piles in pebble soil layers and strongly weathered rock layers, and is characterized by comprising:

[0009] (1) Use a screw drill to drive the drill bit to rotate forward to drill and form a pile hole;

[0010] (2) pouring concrete into the pile hole, and extracting the drill bit upward while pouring concrete into the pile hole; when the screw drill extracts the drill bit upward, the screw drill drives the drill bit to rotate in the opposite direction, thereby forming a spiral groove on the inner wall of the pile hole by using the drill bit;

[0011] (3) After the concrete pouring is completed, a steel cage is implanted into the concrete. The concrete fills the pile hole and groove. After the concrete solidifies, a screw cast-in-place pile is formed.

[0012] In some implementations, the drill bit has cutting teeth for cutting grooves, and the cutting teeth on the drill bit are retracted inside the drill bit when the drill bit rotates forward; and the cutting teeth on the drill bit extend out of the drill bit when the drill bit rotates reversely, thereby cutting the inner wall of the pile hole to form a spiral groove.

[0013] In some embodiments, the drill bit has a drill body with a larger upper end and a smaller lower end, and the drill bit body includes an outer cylinder and an inner cylinder, the inner cylinder is sleeved inside the outer cylinder and can rotate on the outer cylinder, and cutting teeth for cutting drilling are arranged on the lower end and / or the outer side wall of the outer cylinder, and a sliding groove distributed along the radial direction of the inner cylinder is provided at the same height position on the inner cylinder, and cutting teeth are installed in the sliding groove, and the cutting teeth at different height positions on the inner cylinder form a spiral shape along the direction of rotation opposite to the drill bit; a spring is provided between the cutting teeth and the inner bottom of the sliding groove, and two knife exits are provided on the outer cylinder at the height positions corresponding to the sliding groove, and an arc groove is provided on the inner wall of the outer cylinder between the two knife exits, and the depth of the arc groove gradually deepens along the positive rotation direction of the drill bit, and the cutting teeth can extend out of the inner cylinder under the action of the spring and contact with the inner bottom of the arc groove, and pass through the knife exit that is interconnected with the deepest part of the arc groove.

[0014] In some embodiments, the outer wall of the inner cylinder and the inner wall of the outer cylinder are in contact with each other, or a friction ring is provided between the inner cylinder and the outer cylinder and the contact between the outer cylinder and the inner cylinder is achieved through the friction ring; the friction ring is provided with an annular groove corresponding to the position of the arc groove so that the friction ring will not block the arc groove, or the friction ring is arranged between the inner cylinder and the outer cylinder at intervals from top to bottom.

[0015] In some embodiments, the inner cylinder is provided with a plurality of cutting teeth along the height direction of the inner cylinder, and the plurality of cutting teeth include upper cutting teeth, middle cutting teeth and lower cutting teeth, and each cutting tooth of the middle cutting teeth can extend out of the outer cylinder to the same length and greater than the length of each cutting tooth of the upper cutting teeth and the lower cutting teeth, and the length of the upper cutting teeth that can extend out of the outer cylinder gradually increases from top to bottom, and the length of the lower cutting teeth that can extend out of the outer cylinder gradually decreases from top to bottom.

[0016] In some embodiments, the side of the knife edge close to the deepest part of the arc groove is an arc surface that facilitates the retraction of the cutting teeth.

[0017] In some embodiments, a slurry outlet is provided on the outer cylinder body, and a connecting groove interconnected with the slurry outlet is provided on the inner wall of the outer cylinder body, the length of the connecting groove is greater than the length of the arc groove, and the depth of the connecting groove gradually decreases along the direction from the slurry outlet to the two ends of the connecting groove; a grouting branch channel for interconnecting with the connecting groove is provided on the inner cylinder at a position corresponding to the connecting groove, and the grouting branch channel is interconnected with the grouting main channel provided on the inner cylinder.

[0018] In some embodiments, the outer cylinder body and the inner cylinder on the upper and lower sides of the connecting groove are in close contact with each other, or the outer cylinder body and the inner cylinder on the upper and lower sides of the connecting groove are in close contact with each other through a friction ring.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The construction method of the adjustable screw pile drill bit structure of the present invention is used to drill a screw pile. First, the screw drill is used to drive the drill bit to rotate forward, and the cutting teeth on the drill bit are used to drill a hole to form a pile hole. Then, concrete is poured into the pile hole. While pouring concrete, the screw drill is used to drive the drill bit to move upward and drive the drill bit to rotate in the opposite direction. The cutting teeth on the drill bit are used to form a spiral groove on the inner wall of the pile hole. The concrete fills the pile hole and the groove and implants the steel cage. After the concrete solidifies, a screw cast-in-place pile is directly formed. The present invention uses a special drill bit to realize that when the drill bit is rotated forward, it only plays the role of drilling the pile hole (that is, no threaded groove is formed when it rotates forward). When the drill bit rotates in the opposite direction, the cutting teeth used to cut the inner wall of the pile hole extend out of the drill bit to cut the inner wall of the pile hole to form a spiral groove. After the poured concrete solidifies, a screw cast-in-place pile can be formed. The present invention solves the problem that the spiral groove of the existing screw drill is destroyed when drilling into the pebble soil layer and the strongly weathered rock layer, and the spiral concrete cannot be formed on the periphery of the pile body. In the prior art, when the screw drill is used to drive the drill bit to drill into the pebble soil layer and the strongly weathered rock layer, due to the hard geology (slow drilling speed) and the problem of drill jumping, the spiral groove formed by the drill bit is easily destroyed (or the spiral groove cannot be formed), resulting in the inability to form a screw cast-in-place pile after concrete pouring (that is, there is no spiral concrete on the periphery of the pile body, which is called an ordinary cast-in-place pile), thereby losing the function of the screw cast-in-place pile and causing huge engineering quality problems.

[0021] When the present invention utilizes a screw drill to drill and form a pile hole, the inner wall of the pile hole is not cut. On the one hand, the cutting amount during drilling is reduced, and under the same premise (i.e., the power of the screw drill is the same and the pile hole size is the same), the pile hole forming speed can be improved; on the other hand, the present invention changes the forming method of the spiral groove (i.e., the cutting is performed only when the drill bit is pulled upward). Since the speed and difficulty of cutting and forming the spiral groove are much lower than the forming of the pile hole, the spiral groove can be formed quickly, and the drill bit will not repeatedly cut and roll the groove to damage it, so that a good threaded groove can be formed. Even in non-pebble soil layers and strongly weathered rock layers, the forming quality of the threaded groove is better than that of the drill bit in the prior art. Therefore, the present invention not only solves the problem that the drill bit in the prior art cannot form a screw cast-in-place pile in a pebble soil layer and a strongly weathered rock layer, but also improves the forming quality of the spiral groove, the formed screw cast-in-place pile has better quality, and the ability of the screw cast-in-place pile to combine with the soil body is improved, thereby improving the bearing capacity of the screw cast-in-place pile.

[0022] The drill bit of the present invention uses the cutting teeth at the lower end or the outer wall of the outer cylinder to drill the pile hole. When the drill bit (the outer cylinder and the inner cylinder) is drilling the hole, the outer cylinder and the inner cylinder are rotated forwardly through the friction ring or direct contact (that is, the outer cylinder and the inner cylinder use their own static friction). Since the outer cylinder drives the inner cylinder to rotate, there is relative sliding between the outer cylinder and the inner cylinder at the beginning (that is, the rotation speed of the outer cylinder is greater than the rotation speed of the inner cylinder, and the friction between the outer cylinder and the inner cylinder plus the friction between the cutting teeth and the arc groove is insufficient to drive the inner cylinder to rotate. The arc groove gradually deepens along the positive rotation direction of the drill bit. On the one hand, the depth of the arc groove gradually decreases, thereby increasing the friction between the cutting teeth and the arc groove. On the other hand, as the rotation speeds of the inner cylinder and the outer cylinder gradually become the same, the centrifugal force of the cutting teeth on the inner cylinder becomes larger and larger, so the friction between the cutting teeth and the arc groove also becomes larger and larger, and finally the synchronous rotation of the inner cylinder and the outer cylinder is achieved, and the cutting teeth are held in the arc groove (that is, the cutting teeth will not extend out of the outer cylinder to cut the inner wall of the pile hole). When the screw drill drives the drill bit to rotate in the opposite direction, due to the speed difference between the outer cylinder and the inner cylinder, and the depth of the arc groove gradually decreases along the rotation direction of the drill bit, the cutting teeth slide along the arc groove, and finally ejected from the exit edge interconnected with the arc groove (that is, the exit edge interconnected with the deepest part of the arc groove) to cut the hole wall of the pile hole to form a spiral groove.

[0023] The inner cylinder of the present invention is provided with a plurality of cutting teeth along the height direction of the inner cylinder, and the plurality of cutting teeth include upper cutting teeth, middle cutting teeth and lower cutting teeth, and each cutting tooth of the middle cutting teeth can extend out of the outer cylinder body by the same length and is greater than the length of each cutting tooth of the upper cutting teeth and the lower cutting teeth. Since the upper cutting teeth of the cutting teeth on the drill bit first cut the wall of the pile hole when the drill bit is extracted up and down by the screw drilling machine and driven to rotate in the opposite direction, the structural design of the upper cutting teeth, the middle cutting teeth and the lower cutting teeth facilitate the formation of spiral grooves. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A vertical cross-sectional view of an embodiment of a drill bit of the present invention;

[0025] Figure 2 A vertical cross-sectional view of another embodiment of a drill bit of the present invention;

[0026] Figure 3 It is a transverse cross-sectional view of the drill bit of the present invention at a height position. In this schematic diagram, the outer cylinder and the inner cylinder rotate in the positive direction under the driving action of the screw drill, wherein the arrow between the outer cylinder and the inner cylinder represents the movement direction of the inner cylinder relative to the outer cylinder when the outer cylinder and the inner cylinder rotate relative to each other;

[0027] Figure 4 for Figure 3 A structural diagram of the drill bit in the figure when it rotates in the opposite direction under the driving action of the screw drill, in which the cutting teeth on the inner cylinder are just aligned with the cutting edges on the outer cylinder, wherein the arrow between the outer cylinder and the inner cylinder represents the movement direction of the inner cylinder relative to the outer cylinder when the outer cylinder and the inner cylinder rotate relative to each other;

[0028] Figure 5 for Figure 4 A schematic diagram of the structure of the partial enlarged view at A in the middle;

[0029] Figure 6 for Figure 3 A schematic diagram of the structure of the cutting teeth on the inner cylinder passing through the exit of the outer cylinder;

[0030] Figure 7 is a transverse cross-sectional view of the drill bit of the present invention at another height position, in which the outer cylinder and the inner cylinder rotate in the forward direction under the driving action of the screw drill, wherein the arrow between the outer cylinder and the inner cylinder represents the movement direction of the inner cylinder relative to the outer cylinder when the outer cylinder and the inner cylinder rotate relative to each other;

[0031] Figure 8 for Figure 7 A structural diagram of the drill bit in the figure when it rotates in the opposite direction under the driving action of the screw drill, in which the cutting teeth on the inner cylinder are just aligned with the cutting edges on the outer cylinder, wherein the arrow between the outer cylinder and the inner cylinder represents the movement direction of the inner cylinder relative to the outer cylinder when the outer cylinder and the inner cylinder rotate relative to each other;

[0032] Fig. 9 is a transverse cross-sectional view of the drill bit of the invention at another height position, in which the outer cylinder and the inner cylinder rotate in the forward direction under the driving action of the screw drill, wherein the arrow between the outer cylinder and the inner cylinder represents the movement direction of the inner cylinder relative to the outer cylinder when the outer cylinder and the inner cylinder rotate relative to each other;

[0033] Fig.10 It is a schematic diagram of the outer structure of the inner cylinder of the drill bit of the present invention, and each sliding groove (each sliding groove corresponds to a cutting tooth) is distributed on the inner cylinder in a spiral shape;

[0034] Markings in the figure: 1. outer cylinder, 11. tip, 12. cutting teeth, 13. cavity, 14. slurry outlet, 15. arc groove, 16. knife edge, 161. arc surface, 2. inner cylinder, 21. grouting main channel, 221. grouting branch channel, 22. sliding groove, 23. cutting teeth, 24. spring, 25. limit block, 26. end cover, 3. friction ring. DETAILED DESCRIPTION

[0035] The present invention is further described below in conjunction with embodiments, which are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, other embodiments obtained by ordinary technicians in the field without creative work are all within the scope of protection of the present invention.

[0036] In the description of the present invention, it should be noted that the orientations or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention; the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance; in addition, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection; it can be directly connected, or it can be indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood in combination with specific circumstances.

[0037] The construction method of the adjustable screw pile drill bit structure of the present invention is particularly suitable for the construction of screw cast-in-place piles in pebble soil layers and strongly weathered rock layers, and comprises:

[0038] (1) Use a screw drill to drive the drill bit to perform forward rotation drilling to form a pile hole. Before the screw drill drives the drill bit to perform forward rotation drilling, the location of the pile hole should be determined by surveying and mapping, and then the site should be leveled so that the screw drill can work smoothly and ensure that the verticality of the drill rod and drill bit meets the requirements of the specifications.

[0039] (2) Pour concrete into the pile hole, and extract the drill bit upward while pouring concrete into the pile hole; when the screw drill extracts the drill bit upward, the screw drill drives the drill bit to rotate in the opposite direction, thereby using the drill bit to form a spiral groove on the inner wall of the pile hole.

[0040] (3) After the concrete pouring is completed, a steel cage is implanted into the concrete. The concrete fills the pile hole and groove. After the concrete solidifies, a screw cast-in-place pile is formed.

[0041] Among them, the techniques of extracting the drill bit, driving the drill bit to rotate in the opposite direction, and implanting the steel cage are all prior arts, which can be understood by those skilled in the art and will not be described in detail here. The present invention changes the forming method of the pile hole of the screw cast-in-place pile, that is, the drill bit does not form a spiral groove when drilling into the pile hole, but when the drill is lifted, the drill bit is rotated in the opposite direction to form a threaded groove on the inner wall of the pile hole. The existing drill bit forms a spiral groove at the same time as the pile hole is formed.

[0042] In the existing technology, due to the slow drilling speed of the drill bit itself, the grooves formed in the pebble soil layer and the strongly weathered rock layer are easily destroyed under the condition of repeated cutting and rolling, and under the geological conditions of the pebble soil layer and the strongly weathered rock layer itself, that is, even if the spiral grooves are formed, they are easily damaged, resulting in no spiral grooves around the hole wall of the pile hole after the pile hole is drilled, and the piles formed after pouring concrete are ordinary cast-in-place piles. Under the premise of the same diameter, since the single pile bearing capacity of the screw cast-in-place pile is better than that of the ordinary cast-in-place pile, under the same site, the position and number of the screw cast-in-place piles are different from those of the ordinary cast-in-place piles in the design, and the construction of the screw cast-in-place piles that should have been ordinary cast-in-place piles has great safety hazards.

[0043] To solve this problem, the existing technology is to reconstruct the screw cast-in-place piles or make up for it by other means. This method will lead to an increase in construction costs and seriously affect the construction period.

[0044] When the present invention utilizes a screw drill to drill and form a pile hole, the inner wall of the pile hole is not cut. On the one hand, the cutting amount during drilling is reduced, and under the same premise (i.e., the power of the screw drill is the same and the pile hole size is the same), the pile hole forming speed can be improved; on the other hand, the present invention changes the forming method of the spiral groove (i.e., the cutting is performed only when the drill bit is pulled upward). Since the speed and difficulty of cutting and forming the spiral groove are much lower than the forming of the pile hole, the spiral groove can be formed quickly, and the drill bit will not repeatedly cut and roll the groove to damage it, so that a good threaded groove can be formed. Even in non-pebble soil layers and strongly weathered rock layers, the forming quality of the threaded groove is better than that of the drill bit in the prior art. Therefore, the present invention not only solves the problem that the drill bit in the prior art cannot form a screw cast-in-place pile in a pebble soil layer and a strongly weathered rock layer, but also improves the forming quality of the spiral groove, the formed screw cast-in-place pile has better quality, and the ability of the screw cast-in-place pile to combine with the soil body is improved, thereby improving the bearing capacity of the screw cast-in-place pile.

[0045] The present invention is particularly suitable for the construction of screw-cast piles in pebble soil layers and strongly weathered rock layers. It can not only increase the hole-making speed of the pile holes, but also ensure that spiral grooves are formed in the pebble soil layers and strongly weathered rock layers, thereby ensuring the quality of the screw-cast piles. Compared with the prior art, it can shorten the construction period and reduce the construction cost. Most importantly, it can ensure the quality of the screw-cast piles.

[0046] In some implementations, the drill bit has cutting teeth 23 for cutting grooves. When the drill bit rotates forward, the cutting teeth 23 on the drill bit are retracted inside the drill bit (i.e., the cutting teeth do not extend out of the drill bit); when the drill bit rotates reversely, the cutting teeth 23 on the drill bit extend out of the drill bit to cut the inner wall of the pile hole to form a spiral groove.

[0047] In conjunction with the accompanying drawings, the drill body of the drill bit of the present invention is large at the upper end and small at the lower end, and the drill body includes an outer cylinder 1 and an inner cylinder 2, wherein the lower end of the outer cylinder 1 is formed with a tip 11, and the inner cylinder 2 is sleeved inside the outer cylinder 1 and can rotate on the outer cylinder 1, and the lower end and / or the outer side wall of the outer cylinder 1 are provided with cutting teeth 12 for cutting and drilling, wherein the cutting teeth 12 are arranged at the tip part of the outer cylinder 1, and the cutting teeth are used for drilling to form a pile hole. A sliding groove 22 distributed along the radial direction of the inner cylinder 2 is provided at the same height position on the inner cylinder 2, and a cutting tooth 23 is installed in the sliding groove 22. The cutting teeth 23 at different height positions on the inner cylinder 2 form a spiral shape along the direction of rotation opposite to the drill bit; a spring 24 is provided between the cutting tooth 23 and the inner bottom of the sliding groove 22, and two knife openings 16 are provided on the outer cylinder body 1 at the height position corresponding to the sliding groove 22, and an arc groove 15 is provided on the inner wall of the outer cylinder body 1 between the two knife openings 16. The depth of the arc groove 15 gradually deepens along the direction of positive rotation of the drill bit. Under the action of the spring 24, the cutting tooth 23 can extend out of the inner cylinder 2 and contact with the inner bottom of the arc groove 15 and pass through the knife opening 16 that is interconnected with the deepest part of the arc groove 15. That is to say, when each cutting tooth slides from the arc groove to the knife edge 16, the cutting teeth at different height positions on the inner tube form a spiral shape, so that it is convenient to use the spiral cutting teeth to cut the hole wall of the pile hole and form a spiral groove.

[0048] In some embodiments, the outer wall of the inner cylinder 2 and the inner wall of the outer cylinder 1 are in contact with each other, or a friction ring 3 is provided between the inner cylinder 2 and the outer cylinder 1 and the contact between the outer cylinder 1 and the inner cylinder 2 is achieved through the friction ring 3; the friction ring 3 is provided with an annular groove corresponding to the position of the arc groove 15 so that the friction ring 15 does not block the arc groove, or the friction ring 3 is arranged between the inner cylinder 2 and the outer cylinder 1 with an interval between each other up and down.

[0049] Combined with Figure 1 The inner cylinder 2 is provided with a main grouting channel 21, the tip 11 of the outer cylinder 1 is provided with a cavity 13 interconnected with the main grouting channel 21, and the tip 11 is provided with a grouting outlet 14 interconnected with the cavity 13. After the pile hole is formed, the screw drill drives the drill bit (outer cylinder and inner cylinder) to rotate in the opposite direction. During the reverse rotation, the main grouting channel 21 is interconnected with the grouting pipe, so that the concrete in the grouting pipe is ejected through the main grouting channel 21, the cavity 13 and the grouting outlet 14 in sequence for grouting. Figure 1 In the illustrated embodiment, the outer cylinder 1 and the inner cylinder 2 are in direct contact with each other.

[0050] Combined with Figure 2 A friction ring 3 is provided between the inner cylinder 2 and the outer cylinder 1, and the contact between the inner cylinder and the outer cylinder 1 is achieved through the friction ring 3, wherein the friction ring can be installed on the outer wall of the inner cylinder, and the friction ring 3 can also be installed on the inner wall of the outer cylinder. A main grouting channel 21 is provided on the inner cylinder in the vertical direction, and a grouting branch channel 211 which is interconnected with the main grouting channel 21 is also provided at the lower end of the inner cylinder 2, and a grouting outlet 14 is provided on the outer cylinder 1 at a position corresponding to the grouting branch channel 211. After the pile hole is formed, the screw drill drives the drill bit (outer cylinder and inner cylinder) to rotate in the opposite direction. During the reverse rotation, the main grouting channel 21 is interconnected with the grouting pipe, so that the concrete in the grouting pipe is ejected through the main grouting channel 21, the grouting branch channel 211 and the grouting outlet 14 in turn for grouting. In the attached Figure 2 In the illustrated embodiment, the friction ring 3 is disposed between the outer cylinder and the inner cylinder at intervals, and the friction ring 3 does not block the arc groove 15 .

[0051] In the attached Figure 2 In the embodiment shown, since the outer cylinder 1 and the inner cylinder 2 rotate relative to each other, a connecting groove connected to the slurry outlet 14 is provided on the inner wall of the outer cylinder, and the arc length of the connecting groove is greater than the arc length of the arc groove, that is, when the outer cylinder and the inner cylinder rotate relative to each other, the grouting branch channel 211 can always be connected to the connecting groove, and finally the slurry is discharged through the slurry outlet 14. The upper and lower ends of the connecting groove should be sealed by means of sealing rings, etc., to prevent concrete from jumping out from between the outer cylinder and the inner cylinder.

[0052] During the sealing process, the inner cylinder and the outer cylinder can be directly sealed by close contact, or the friction ring can be used to seal the upper and lower ends of the connecting groove. In the specific implementation process, the following technical methods can be adopted: the outer cylinder on the upper and lower sides of the connecting groove is in close contact with the inner cylinder, or the outer cylinder on the upper and lower sides of the connecting groove is in close contact with the inner cylinder through the friction ring.

[0053] In the attached Figure 1 and attached Figure 2In the embodiment shown, Figure 1 The grouting method shown (grouting main channel, cavity, grouting outlet) is different from the attached Figure 2 The grouting method shown (grouting main channel, grouting branch channel, grouting outlet) is easier to control and manufacture, so it is preferred to use the attached Figure 1 The grouting method shown.

[0054] In some embodiments, in order to improve the stability between the inner cylinder 2 and the outer cylinder 1, the lower end of the inner cylinder is provided with a truncated cone-shaped structure with a large upper end and a small lower end, and the inner top of the outer cylinder 1 is provided with a cavity (for example, an attached Figure 1 The cavity 13 shown in FIG. 1 is adapted to the truncated cone structure and the cavity, so that when the outer cylinder and the inner cylinder rotate relative to each other, the inner cylinder can automatically align. When the lower end of the inner cylinder is provided with a truncated cone structure and the grouting method adopts the attached Figure 1 When the grouting method is shown, the main grouting channel 21 runs through the truncated cone structure.

[0055] In some embodiments, the inner cylinder 2 is provided with a plurality of cutting teeth along the height direction of the inner cylinder, and the plurality of cutting teeth include upper cutting teeth, middle cutting teeth and lower cutting teeth, and the length of each cutting tooth of the middle cutting teeth that can extend out of the outer cylinder body is the same and greater than the length of each cutting tooth of the upper cutting teeth and the lower cutting teeth, and the length of the upper cutting teeth that can extend out of the outer cylinder body gradually increases from top to bottom, and the length of the lower cutting teeth that can extend out of the outer cylinder body gradually decreases from top to bottom. That is to say, each cutting tooth is distributed in a truncated cone shape on the inner cylinder 2, and the length of each cutting tooth gradually increases from top to bottom. When the length of the cutting tooth increases to a certain length, the length is maintained, and then gradually decreased. This facilitates each cutting tooth 23 to perform cutting.

[0056] Combined with Figure 3 , Attachment Figure 7 and attached Fig. 9 The cutting teeth 23 at different height positions on the inner cylinder are arranged in different directions, and the cutting teeth 23 at different height positions on the inner cylinder form a spiral shape, so that the cutting teeth 23 at each height position cut the wall of the pile hole together to form a spiral groove.

[0057] Combined with Figure 3 and attached Figure 7 , when the screw drill drives the drill bit to rotate forward (attached Figure 3 and attached Figure 7When the drill bit rotates in the direction indicated by the outermost arrow), since the outer cylinder 1 drives the inner cylinder to rotate (that is, the outer cylinder is directly connected to the drill rod of the screw drill), there is relative sliding between the outer cylinder and the inner cylinder at the beginning (that is, the rotation speed of the outer cylinder is greater than the rotation speed of the inner cylinder, and the friction between the outer cylinder and the inner cylinder plus the friction between the cutting teeth and the arc groove is insufficient to drive the inner cylinder to rotate), and the depth of the arc groove gradually deepens along the positive rotation direction of the drill bit. On the one hand, as the depth of the arc groove gradually decreases, the friction between the cutting teeth and the arc groove is increased. On the other hand, as the rotation speeds of the inner cylinder and the outer cylinder are gradually the same, the centrifugal force of the cutting teeth on the inner cylinder becomes larger and larger, so the friction between the cutting teeth and the arc groove also becomes larger and larger, and finally the synchronous rotation of the inner cylinder and the outer cylinder is achieved, and the cutting teeth are held in the arc groove (that is, the cutting teeth will not extend out of the outer cylinder to cut the inner wall of the pile hole).

[0058] Combined with Figure 4 , Attachment Figure 8 and attached Fig. 9 When the screw drill drives the drill bit to rotate in the opposite direction, due to the speed difference between the outer cylinder and the inner cylinder, and the depth of the arc groove gradually decreases along the rotation direction of the drill bit, the cutting teeth slide along the arc groove, and finally eject from the exit edge interconnected with the arc groove (that is, the exit edge interconnected with the deepest part of the arc groove) to cut the hole wall of the pile hole, thereby forming a spiral groove (combined with the attached Figure 6 The cutting teeth 23 extend out of the blade edge 16 to cut the hole wall of the pile hole to form a spiral groove.

[0059] Preferably, the direction of the cutting edge of the cutting tooth 23 is opposite to the direction of reverse rotation of the drill bit, that is, the direction of the cutting edge is the same as the forward rotation direction of the drill bit, so that the cutting edge of the cutting tooth 23 can contact the soil for cutting earlier than other parts of the cutting tooth 23.

[0060] Combined with Figure 5 In some embodiments, the side of the knife edge 16 close to the deepest part of the arc groove 15 is an arc surface 161 for facilitating the retraction of the cutting teeth 23 .

[0061] In order to facilitate the installation of the spring 24 and the cutting tooth 23, an end cover 26 is provided at the inner cylinder corresponding to the end of the sliding groove 23. When the spring and the cutting tooth 23 need to be assembled, the end cover 26 can be opened for installation; similarly, when the cutting tooth 23 and the spring need to be replaced, the end cover 26 is opened to take out the cutting tooth 23 or spring to be replaced, and then the new spring and cutting tooth can be assembled. In addition, in order to prevent the cutting tooth 23 from falling off, the cutting tooth is also provided with a limit block 25.

[0062] In the specific implementation process, the end cover 26 can be directly used to limit the limit block 25. Figure 1To Attachment Figure 8 The sliding groove may also be set as a stepped groove, and the position of the cutting tooth 23 may be limited by the combined effect of the stepped groove and the end cover to prevent the cutting tooth 23 from detaching from the inner tube.

[0063] The structural design of the cutting teeth 23 and the spring 24 in the present invention is that when the cutting teeth 23 cannot cut a rock mass when encountering a pebble soil layer and a strongly weathered rock layer when cutting the wall of the pile hole, the cutting teeth can be squeezed and retracted into the outer cylinder (i.e., not extending out of the outer cylinder), so that the rock mass is not cut. This structural design, on the one hand, avoids the problem of groove collapse caused by forcibly cutting the rock mass (due to the structural characteristics of the pebble soil layer and the strongly weathered rock layer, although the rock mass cannot be cut off by hard cutting, it is very likely to drive the rock mass and the surrounding soil to fall off together, thereby destroying the groove; in the prior art, the spiral groove is destroyed and there is also hard cutting of a certain rock mass, which causes the rock mass to fall off together with the surrounding soil mass and then destroys the spiral groove on a large scale), on the other hand, there are a small number of discontinuous areas in the entire spiral groove, which does not affect the bearing capacity of the screw cast-in-place pile. Therefore, the structural design of the cutting teeth of the present invention can reduce or reduce the damage to the spiral groove as much as possible, thereby further ensuring the pile quality of the screw cast-in-place pile.

Claims

1. A construction method for forming screw piles by drilling with an adjustable screw pile drill bit structure, which is used for the construction of screw cast-in-place piles in pebble soil layers and strongly weathered rock layers, characterized in that: include: (1) Using a screw drill to drive the drill bit to perform forward rotation drilling to form a pile hole; (2) pouring concrete into the pile hole, and pulling the drill bit upward while pouring concrete into the pile hole; when the screw drill pulls the drill bit upward, the screw drill drives the drill bit to rotate in the opposite direction, thereby forming a spiral groove on the inner wall of the pile hole by using the drill bit; (3) After the concrete pouring is completed, a steel cage is implanted into the concrete, and the concrete fills the pile hole and the groove. After the concrete solidifies, a screw cast-in-place pile is formed; The drill bit is provided with cutting teeth for cutting grooves, and the cutting teeth on the drill bit are contracted inside the drill bit when the drill bit rotates forward; the cutting teeth on the drill bit are extended out of the drill bit when the drill bit rotates reversely, thereby cutting the inner wall of the pile hole to form a spiral groove; the drill bit body is large at the upper end and small at the lower end, and the drill bit body comprises an outer cylinder and an inner cylinder, the inner cylinder is sleeved inside the outer cylinder and can rotate on the outer cylinder, the lower end and / or the outer side wall of the outer cylinder are provided with cutting teeth for cutting and drilling, and the inner cylinder is provided with a plurality of A sliding groove distributed along the radial direction of the inner cylinder, wherein a cutting tooth is installed in the sliding groove, and the cutting teeth at different height positions on the inner cylinder form a spiral shape along the direction of rotation opposite to the drill bit; a spring is arranged between the cutting tooth and the inner bottom of the sliding groove, and two knife exits are arranged on the outer cylinder body at the height position corresponding to the sliding groove, and an arc groove is arranged on the inner wall of the outer cylinder body between the two knife exits, and the depth of the arc groove gradually deepens along the direction of positive rotation of the drill bit, and the cutting tooth can extend out of the inner cylinder under the action of the spring and contact with the inner bottom of the arc groove, and pass through the knife exit that is interconnected with the deepest part of the arc groove; The inner cylinder is provided with a plurality of cutting teeth along the height direction of the inner cylinder, and the plurality of cutting teeth include upper cutting teeth, middle cutting teeth and lower cutting teeth, and each cutting tooth of the middle cutting teeth can extend out of the outer cylinder to the same length and is greater than the length of each cutting tooth of the upper cutting teeth and the lower cutting teeth, and the length of the upper cutting teeth that can extend out of the outer cylinder gradually increases from top to bottom, and the length of the lower cutting teeth that can extend out of the outer cylinder gradually decreases from top to bottom.

2. The construction method for drilling a screw pile using the adjustable screw pile drill bit structure according to claim 1, characterized in that: The outer wall of the inner cylinder is in contact with the inner wall of the outer cylinder, or a friction ring is provided between the inner cylinder and the outer cylinder and the contact between the outer cylinder and the inner cylinder is achieved through the friction ring; the friction ring is provided with an annular groove corresponding to the position of the arc groove so that the friction ring does not block the arc groove, or the friction ring is arranged between the inner cylinder and the outer cylinder at an interval from top to bottom.

3. The construction method for drilling a screw pile using the adjustable screw pile drill bit structure according to claim 1, characterized in that: The side of the knife exit close to the deepest part of the arc groove is an arc surface for facilitating the retraction of the cutting teeth.

4. A construction method for forming a screw pile by drilling with an adjustable screw pile drill bit structure according to any one of claims 1 to 3, characterized in that: A slurry outlet is provided on the outer cylinder body, and a connecting groove interconnected with the slurry outlet is provided on the inner wall of the outer cylinder body, the length of the connecting groove is greater than the length of the arc-shaped groove, and the depth of the connecting groove gradually decreases along the direction from the slurry outlet to the two ends of the connecting groove; a grouting branch channel for interconnecting with the connecting groove is provided on the inner cylinder at a position corresponding to the connecting groove, and the grouting branch channel is interconnected with the grouting main channel provided on the inner cylinder.

5. The construction method for forming a screw pile by drilling with an adjustable screw pile drill bit structure according to claim 4, characterized in that: The outer cylinder body located at the upper and lower sides of the connecting groove is in close contact with the inner cylinder, or the outer cylinder body located at the upper and lower sides of the connecting groove is in close contact with the inner cylinder through the friction ring.

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