Construction method of screw pile in soft stratum

Abstract

The invention belongs to the technical field of screw piles, discloses a construction method of a screw pile in a soft stratum, and aims to solve the problems of hole crossing and hole collapse when a long screw drilling machine performs drilling and hole forming on the soft stratum. The method comprises a drilling machine in-place drilling procedure, and the drilling machine in-place drilling procedure specifically comprises the steps that (1) a protection barrel is arranged and connected to the periphery of a spiral drilling rod; (2) the spiral drill rod is connected to a power head of the long spiral drilling machine; (3) the power head rotates to drive drilling to form a pile hole, and the power head synchronously and downwards extrudes the protection barrel to extrude the protection barrel into the soft stratum; and (4) concrete is injected into the pile hole for pouring, the spiral drill rod and the protection barrel are slowly lifted upwards to spirally cut the hole wall of the pile hole, and the screw pile is formed after pouring is completed. The protection barrel can basically play a role in protecting the wall of the whole pile hole, so that the problems of hole crossing and hole collapse are prevented, and finally the purpose of improving the forming quality of the screw pile is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of screw piles, and in particular relates to a construction method of screw piles in soft strata. Background Art

[0002] The full name of screw pile is semi-spiral squeezed hole pipe pump pressure concrete pile, which can also be referred to as screw pile. It refers to a variable cross-section special-shaped pile composed of a cylindrical pile body on the upper part and a threaded pile body on the lower part. The length of the upper and lower pile sections can be adjusted according to the soil conditions of the foundation. The outer diameter of the lower threaded pile body is the same as the diameter of the upper cylindrical pile body. The advantages of this type of pile are: good environmental protection effect; reliable pile body quality; simplified construction process and high efficiency; wide range of application, can be used as the pile foundation of pile foundation, and can also be used for CFG pile composite foundation and CM long and short pile composite foundation. It is suitable for silty clay, clay, silty clay, silt, sandy soil layer and pebble layer with a particle size of less than 30mm and strongly weathered rock formations.

[0003] At present, there are many methods for the construction of screw piles. For example, the patent with application number 2023111390236 discloses a construction method for improving the quality of cast-in-place screw piles in pebble formations, including the following steps: S1, positioning and laying out, the operator measures and lays out each pile position; S2, the screw cast-in-place pile driver is in place; S3, the pile driver drill rod drills to realize the screw pile hole; S4, the pile driver drill rod is lifted, and concrete is poured into the pile hole at the same time; S5, the steel cage is pressed into the concrete of the pile hole; S6, S1 to S5 are repeated to construct the next screw pile until the construction is completed. The construction method of this screw pile is also a commonly used screw pile construction step.

[0004] For another example, the patent with application number 2020106656749 discloses a combined screw pile and a method for using the same, step S1: start the machine, start the integral screw pile to rotate; step S2: drill holes, use the screw pile to drill holes in the parts where piles are required; step S3: grouting, slowly inject concrete slurry into the inner liner through the grouting pipe in the injection mechanism; step S4: stirring, start the rotating assembly to drive the inner liner to rotate, and drive the stirring assembly located in the drill bit to stir under the rotation of the inner liner; step S 5: Lifting the pile, while carrying out step S3, the screw pile is lifted so that the slurry outlet assembly in the drill bit does not block the overflow hole, so that the concrete slurry flows out of the overflow hole and forms a pile in the hole formed in step S1; step S6: Stop grouting, after injecting the concrete slurry required for the pile into the screw pile, stop grouting into the screw pile; step S7: Cleaning, when the pile lifting is completed, water is injected into the screw through the water injection pipe in the injection mechanism to clean the inside; step S8: Stop the machine, stop the rotation of the entire screw pile and the rotating motor. The method for using the screw pile can improve the molding quality of the screw pile to a certain extent.

[0005] However, in the process of drilling holes in soft formations, although the drill rod will squeeze the hole wall to make it dense during the drilling process, which reduces the risk of cross-hole and hole collapse to a certain extent, for thicker soft formations, there is still the risk of cross-hole and hole collapse. Summary of the invention

[0006] In order to solve the problems of cross-hole and hole collapse when a long screw drill is used to drill holes in soft strata, the present invention provides a construction method for screw piles in soft strata, which can protect the hole wall during the drilling process, thereby reducing the risks of cross-hole and hole collapse in deep soft strata.

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

[0008] A construction method for screw piles in soft strata includes a site leveling process and a measurement and setting out process, and is characterized in that it also includes a drilling process with a drilling rig in place, and the drilling process with a drilling rig in place specifically includes the following:

[0009] (1) A protective tube is arranged and connected to the periphery of the auger rod;

[0010] (2) Connecting the auger rod equipped with a protective tube to the power head of the long auger drill;

[0011] (3) The long spiral drill drives the power head to rotate and then drives the spiral drill rod to drill downward to form a pile hole. The power head drives the spiral drill rod to drill and squeeze the protective tube downward to squeeze the protective tube into the soft formation;

[0012] (4) Concrete is injected into the pile hole to cast the pile hole. While casting the concrete, the spiral drill rod and the protective tube are slowly lifted upward. When the protective tube is lifted upward, the wall of the pile hole is spirally cut. After the casting is completed, a screw pile is formed.

[0013] In some embodiments, the screw pile includes two sections of cylindrical pile bodies and two sections of threaded pile bodies, and the cylindrical pile bodies and the threaded pile bodies are interlaced with each other.

[0014] In some embodiments, the protective cylinder includes a hollow cylinder body, a plurality of vertical slide grooves are opened on the circumference of the cylinder body, a plurality of through holes are opened on the cylinder body which are arranged at intervals up and down and are interconnected with the vertical slide grooves, a vertical slide bar is arranged in the vertical slide groove, and a plurality of cutting blocks are arranged on the vertical slide bar for passing through the through holes and extending out of the cylinder body for spiral cutting of the pile hole wall; the upper end of the vertical slide bar extends out of the vertical slide groove and is connected to a connecting cylinder for connecting to the power head of a long spiral drilling rig; when the vertical slide bar slides in the vertical slide groove, there is a distance between the bottom of the vertical slide bar and the bottom of the vertical slide groove.

[0015] During the specific implementation process, a plurality of wear-resistant elastic blocks are installed on the side of the vertical slide bar facing the perforation, and the wear-resistant elastic blocks are adapted to the perforations; a wear-resistant elastic part is provided on the other side of the vertical slide bar, and the elastic force applied by the wear-resistant elastic part to the vertical slider is greater than the force applied by the wear-resistant elastic block to the vertical slide bar.

[0016] In some embodiments, the lower end of the connecting tube is provided with a plurality of sliding grooves along the radial direction of the connecting tube, and a sliding block capable of sliding in the sliding groove is arranged in the sliding groove, and the upper end of each vertical slide bar is connected to the sliding block.

[0017] In some embodiments, the upper end of the cylinder is connected to an extension cylinder, a plurality of vertically arranged tooth grooves are arranged on the inner wall of the extension cylinder, and a plurality of gear rings matching the tooth grooves are arranged on the periphery of the connecting cylinder.

[0018] In some embodiments, the lower end of the auger rod extends out of the lower end of the protective cylinder body, the lower end of the cylinder body is formed with a tip, and cutting teeth are distributed around the periphery of the tip.

[0019] In some embodiments, the auger rod extends out of the lower end surface of the cylinder less than or equal to 1m, the lowest perforation on the cylinder is greater than or equal to 1m away from the bottom of the cylinder, and the uppermost perforation on the cylinder is spaced apart from the top of the cylinder.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The construction method of screw piles in soft strata of the present invention can basically protect the entire pile hole by using the protective tube to prevent the problems of cross-hole and hole collapse. At the same time, the protective tube can be used to cut the hole wall of the pile hole to form a spiral groove and then cast to form a screw pile, ultimately achieving the purpose of improving the molding quality of the screw pile. In the prior art, concrete is poured gradually upward from the bottom of the pile hole. When the hole collapses and cross-holes occur, the fallen rock and soil will be immersed in the concrete (the unsolidified concrete is in a paste state), which leads to poor casting quality of the screw pile. Although the spiral blades on the auger rod can play a certain blocking role, they still cannot block the small particles wrapped in soil from being embedded in the poured concrete. In addition, the length of the spiral blades on the auger rod changes gradually (that is, the outer diameter of the lower end of the auger rod is smaller than the outer diameter of the upper end of the auger rod). When the hole collapse and cross-hole occur in the small-diameter section of the auger rod, the obstruction and shielding effect of the spiral blades is greatly reduced, causing the rock and soil to fall into and sink into the poured concrete, further leading to poor molding quality of the screw pile.

[0022] The invention utilizes the structural coordination of the protective tube and the spiral drill rod, and can naturally form the lowest section of the threaded pile body (the spiral drill rod section extending out of the bottom of the cylinder), the lower section of the cylindrical pile body (the section between the lowest perforation on the cylinder and the bottom of the cylinder), the upper section of the threaded pile body (the section corresponding to the uppermost perforation on the cylinder and the lowest perforation), and the top cylindrical pile body (the section between the uppermost perforation and the top of the cylinder), that is, the invention can form four sections of alternating cylindrical pile bodies and threaded pile bodies. Therefore, compared with the existing screw piles, the screw pile formed by the invention can improve the bonding force between the screw pile and the soil, thereby improving the pull-out resistance and bearing capacity of the screw pile. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic structural diagram of an embodiment of a protective tube and a spiral drill rod of the present invention;

[0024] Figure 2 for Figure 1 A schematic diagram of a partial enlarged view of the center A;

[0025] Figure 3 for Figure 1 A schematic diagram of a partial enlarged view of point B in the middle;

[0026] Figure 4 It is a structural schematic diagram of an existing screw pile;

[0027] Figure 5 A schematic diagram of the structure of a screw pile formed by the present invention;

[0028] Markings in the figure: 01, power head, 02, screw pile, 021, cylindrical pile body, 022, threaded pile body, 1, spiral drill rod, 101, spiral blade, 102, slurry outlet hole, 2, cylinder body, 201, vertical slide groove, 202, perforation, 203, cutting teeth, 3, vertical slide bar, 301, cutting block, 302, wear-resistant elastic block, 303, wear-resistant elastic part, 4, connecting cylinder, 401, sliding groove, 402, sliding block, 403, gear ring, 5, extension cylinder, 501, tooth groove. DETAILED DESCRIPTION

[0029] 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.

[0030] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions 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 directly connected or 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 according to specific circumstances.

[0031] In conjunction with the accompanying drawings, the construction method of the soft stratum screw pile of the present invention includes the process of leveling the site and the process of measuring and setting out, and also includes the process of drilling in place by a drilling rig. The process of drilling in place by the drilling rig specifically includes the following:

[0032] (1) A protective tube is arranged and connected to the periphery of the auger rod 1; wherein the periphery of the auger rod 1 is provided with a spiral blade 101 for cutting and drilling, a grouting channel is formed in the middle of the auger rod 1, and a slurry outlet hole 102 is opened at the bottom of the auger rod 1. When grouting into the pile hole, the external grouting pipe is interconnected with the auger rod 1, and the slurry in the grouting pipe enters the grouting channel and is finally discharged from the slurry outlet 102, thereby performing grouting and pouring operations on the formed pile hole from bottom to top. Among them, the structure of the auger rod 1 itself belongs to the prior art, and the technicians in this field can understand and comprehend it, so it will not be repeated here.

[0033] (2) Connecting the auger rod 1 equipped with a protective tube to the power head 01 of the long auger drilling machine;

[0034] (3) The long spiral drill drives the power head 01 to rotate and then drives the spiral drill rod 1 to drill downward to form a pile hole. The power head 01 drives the spiral drill rod to drill and squeeze the protective tube downward to squeeze the protective tube into the soft formation;

[0035] (4) Concrete is injected into the pile hole to cast the pile hole. While casting the concrete, the spiral drill rod 1 and the protective tube are slowly lifted upward. When the protective tube is lifted upward, the wall of the pile hole is spirally cut. After the casting is completed, a screw pile 02 is formed.

[0036] In the specific implementation process, the process of leveling the site and the process of measuring and setting out belong to the existing technology. The purpose of measuring and setting out is to determine the position of the pile hole of the screw pile (screw cast-in-place pile) according to the design requirements. Those skilled in the art can understand and comprehend it, so it will not be repeated here.

[0037] The construction method of screw piles in soft strata of the present invention can basically protect the entire pile hole by using the protective tube to prevent the problems of cross-hole and hole collapse. At the same time, the protective tube can be used to cut the hole wall of the pile hole to form a spiral groove and then cast to form a screw pile, ultimately achieving the purpose of improving the molding quality of the screw pile. In the prior art, concrete is poured gradually upward from the bottom of the pile hole. When the hole collapses and cross-holes occur, the fallen rock and soil will be immersed in the concrete (the unsolidified concrete is in a paste state), which leads to poor casting quality of the screw pile. Although the spiral blades on the auger rod can play a certain blocking role, they still cannot block the small particles wrapped in soil from being embedded in the poured concrete. In addition, the length of the spiral blades on the auger rod changes gradually (that is, the outer diameter of the lower end of the auger rod is smaller than the outer diameter of the upper end of the auger rod). When the hole collapse and cross-hole occur in the small-diameter section of the auger rod, the obstruction and shielding effect of the spiral blades is greatly reduced, causing the rock and soil to fall into and sink into the poured concrete, further leading to poor molding quality of the screw pile.

[0038] In some embodiments, the protective cylinder includes a hollow cylinder 2, a plurality of vertical slide grooves 201 are provided on the circumference of the cylinder 2, a plurality of through holes 202 are provided on the cylinder 2 and are interconnected with the vertical slide grooves 201, a vertical slide bar 3 is arranged in the vertical slide groove 201, and a plurality of cutting blocks 301 are provided on the vertical slide bar 3 for passing through the through holes 202 and extending outside the cylinder 2 for spiral cutting of the pile hole wall; the upper end of the vertical slide bar 3 extends out of the vertical slide groove 201 and is connected to a connecting cylinder 4 for connecting to the power head 01 of the long spiral drilling machine; when the vertical slide bar 3 slides in the vertical slide groove 201, there is a distance between the bottom of the vertical slide bar 3 and the bottom of the vertical slide groove 201. In the specific implementation process, the spiral drill rod 1 is also directly connected to the connecting cylinder 4, and the connecting cylinder 4 is directly connected and fastened to the power head 01.

[0039] Among them, during the working process of the protective tube of the present invention, when the power head 01 of the long spiral drill drives the spiral drill rod 1 and the protective tube to drill into the soft formation, the power head synchronously squeezes the connecting tube, and the connecting tube drives the vertical slide bar to move downward. Due to the support of the rock and soil, the cylinder body of the protective tube makes the vertical slide bar move downward along the vertical slide groove, so that the bottom of the vertical slide bar contacts the bottom of the vertical slide groove, and then the downward moving vertical slide bar drives the cylinder body to move downward and squeeze the cylinder body so that the cylinder body can squeeze the cut soil into the formation, and at this time the cutting block does not extend out of the outer surface of the cylinder body. When concrete is pumped into the pile hole for pouring, the power head drives the connecting tube and the auger rod to move upward synchronously, and the connecting tube drives the vertical slide bar to move upward. Since the cylinder body is in direct contact with the hole wall of the pile hole, the friction resistance acts on the cylinder body all the time, causing the vertical slide bar to move upward relative to the cylinder body, thereby adjusting the relative position between the vertical slide bar and the vertical slide groove, so that the cutting block corresponds to the perforation on the cylinder body and extends the perforation to perform spiral cutting on the hole wall of the pile hole to form a spiral groove body. After the pouring is completed, a threaded consolidation body is formed in the spiral groove body, thereby forming a screw pile (screw cast-in-place pile). In other words, when the long auger rod drives the connecting tube to move downward, the cutting block on the vertical slide bar and the perforation on the cylinder body are staggered with each other, and when the vertical slide bar is lifted upward, the cutting block on the vertical slide bar corresponds to the position of the perforation one by one.

[0040] In the specific implementation process, a plurality of wear-resistant elastic blocks 302 are installed on the side of the vertical slide bar 3 facing the through hole 202, and the wear-resistant elastic blocks 302 and the through hole 202 are adapted to each other; a wear-resistant elastic member 303 is provided on the other side of the vertical slide bar 3, and the elastic force applied by the wear-resistant elastic member 303 to the vertical slide bar 3 is greater than the force applied by the wear-resistant elastic block 302 to the vertical slide bar 3. When the vertical slide bar 3 drives the cylinder 2 to move downward, the wear-resistant elastic blocks 302 correspond to the through hole 202; when the vertical slide bar 3 and the protective cylinder move upward, the wear-resistant elastic blocks 302 withdraw from the through hole 202 and make the cutting block 301 correspond to the through hole 202. The function of the wear-resistant elastic block 302 is to prevent the soil of the pile hole wall from passing through the through hole 202 and entering the vertical slide groove 201.

[0041] In the specific implementation process, since the cylinder body 2 of the protection cylinder provides sufficient support to the pile hole wall and the size of the through hole 202 is relatively small compared to the outer surface area of ​​the protection cylinder, it is difficult for the soil falling off the pile hole wall to enter the through hole.

[0042] Among them, in order to facilitate the wear-resistant elastic block 302 to slide out of the through hole 202, and to facilitate the cutting block 301 to slide into the through hole 202, the through hole 202 is preferably designed to be a trapezoidal shape with one end small and the other end large (that is, the opening size of the through hole close to the vertical slide bar is larger than the size on the side away from the vertical slide bar), or a bell mouth is provided on the side of the through hole close to the vertical slide bar.

[0043] In the specific implementation process, in order to facilitate cutting and forming a threaded groove on the wall of the pile hole, the through holes 202 on the cylinder 2 are distributed in a spiral shape. Similarly, the cutting blocks 301 on the vertical slide bars 3 are also distributed in a spiral shape.

[0044] In some embodiments, the lower end of the connecting tube 4 is provided with a plurality of sliding grooves 401 along the radial direction of the connecting tube 4, and the sliding grooves 401 are provided with sliding blocks 402 that can slide in the sliding grooves 401, and the upper ends of the vertical slide bars 3 are connected to the sliding blocks 402. Thus, when the vertical slide bars move radially in the vertical slide bars, the vertical slide bars will not be hindered from moving in the perforation direction of the cylinder body due to the setting of the connecting tube.

[0045] In some embodiments, the upper end of the cylinder 2 is connected to an extension cylinder 5, and the inner wall of the extension cylinder 5 is provided with a plurality of vertically arranged tooth grooves 501, and the periphery of the connecting cylinder 4 is provided with a plurality of gear rings 403 that are mutually adapted to the tooth grooves 501. Through the structural coordination of the extension cylinder and the connecting cylinder, when the power head of the long spiral drill drives the connecting cylinder to rotate, the connecting cylinder can transmit the rotational force to the extension cylinder, and then transmit it to the cylinder body through the extension cylinder, so that the cylinder body can be rotated to cut the soil, and then the cylinder body of the protective cylinder can not only penetrate into the soil by extrusion, but also cut the soil by rotational cutting. When the vertical slide bar and the cylinder body are lifted upward, the connecting cylinder can slide along the extension cylinder so that the vertical slide bar slides along the vertical slide groove of the cylinder body, and at the same time, it can still transmit the rotational force to the cylinder body so that the cylinder body keeps rotating, so as to facilitate the pulling out of the protective cylinder from the pile hole.

[0046] In some embodiments, the lower end of the auger rod 1 extends out of the lower end of the protective cylinder body 2, and the lower end of the cylinder body 2 is formed with a tip, and the outer periphery of the tip is distributed with cutting teeth 203; thereby, when a long auger drill is used to drill a pile hole, the central area of ​​the pile hole is first drilled using the auger rod, and then the cutting teeth at the tip of the cylinder are used to cut and drill, so that during the entire drilling and hole-forming process, the main cutting is still completed by the auger rod, and the cutting amount of the protective cylinder is relatively small.

[0047] In some embodiments, the distance that the auger rod 1 extends out of the lower end face of the barrel 2 is less than or equal to 1m, the distance between the lowest perforation 202 on the barrel 2 and the bottom of the barrel 2 is greater than or equal to 1m, and the highest perforation 202 on the barrel 2 is spaced from the top of the barrel 2. There is also a technology in the existing screw piles that uses a section of steel cylinder to protect the formed pile hole, but the length of the steel cylinder used in the prior art is much lower than the depth of the pile hole, and for deep and weak formations, the pile hole in the lower section still has the risk of cross-hole and collapse. The length of the protective cylinder in the invention is only slightly shorter than the length of the auger rod, so it can basically protect the entire pile hole, thereby reducing the risk of cross-hole and collapse; more importantly, the protective cylinder of the present invention can also cut the wall of the pile hole through the cutting block, thereby forming a spiral groove body formed on the wall of the pile hole, and a screw pile with threads can be formed after casting. At the same time, the lowest perforation on the protective tube of the present invention is spaced apart from the bottom of the cylinder body, so that the lower section of the screw pile can form a cylindrical pile body (i.e., the section between the bottom of the cylinder body and the lowest perforation forms a cylindrical pile body due to the absence of cutting by a cutting block), and the lowest short section extending out of the protective tube forms a spiral pile body, the area between the perforations of the cylinder body forms a threaded pile body, and the section at the uppermost end of the perforation also forms a cylindrical pile body.

[0048] However, in the prior art, the pile body of the screw pile 02 is composed of two sections, an upper cylindrical pile body 021 and a lower threaded pile body 022. The length of the cylindrical pile body 021 and the length of the threaded pile body 022 can be adjusted according to actual conditions, for example, the length of the cylindrical pile body in the upper section accounts for 15% of the entire pile hole length, and the threaded pile body in the lower section accounts for 85% of the entire pile hole length. However, no matter how the ratio of the cylindrical pile body and the threaded pile body is adjusted, it is impossible to change the fact that the upper section is a cylindrical pile body and the lower section is a threaded pile body (i.e., the entire screw pile is divided into two sections, upper and lower). The invention utilizes the structural coordination of the protective tube and the spiral drill rod, and can naturally form the lowest section of the threaded pile body 022 (the section of the spiral drill rod 1 extending out of the bottom of the cylinder 2), the lower section of the cylindrical pile body 021 (the section between the lowest through hole 202 on the cylinder 2 and the bottom of the cylinder 2), the upper section of the threaded pile body 022 (the corresponding section between the uppermost through hole 202 and the lowest through hole 202 on the cylinder 2), and the top cylindrical pile body 021 (the section between the uppermost through hole 202 and the top of the cylinder 2), that is, the invention can form four sections of alternating cylindrical pile bodies 021 and threaded pile bodies 022. Therefore, compared with the existing screw piles, the screw pile formed by the invention can improve the bonding force between the screw pile and the soil, thereby improving the pull-out resistance and bearing capacity of the screw pile.

Claims

1. A construction method for screw piles in soft strata, comprising a site leveling process and a surveying and setting out process, characterized in that: The process of drilling with a drilling rig in place is also included, and the process of drilling with a drilling rig in place specifically includes the following: (1) a protective tube is arranged and connected to the periphery of the auger rod (1); (2) Connecting the auger rod equipped with a protective tube to the power head (01) of the long auger drilling machine; (3) The long spiral drill drives the power head (01) to rotate and then drives the spiral drill rod (1) to drill downward to form a pile hole. The power head (01) drives the spiral drill rod to drill and simultaneously squeezes the protective tube downward to squeeze the protective tube into the soft formation; (4) Concrete is injected into the pile hole to cast the pile hole. While casting the concrete, the spiral drill rod (1) and the protective tube are slowly lifted upward. When the protective tube is lifted upward, the wall of the pile hole is spirally cut. After the casting is completed, a screw pile (02) is formed.

2. The construction method of screw piles in soft strata according to claim 1, characterized in that: The screw pile (02) comprises two sections of cylindrical pile bodies (021) and two sections of threaded pile bodies (022), and the cylindrical pile bodies (021) and the threaded pile bodies (022) are interlaced with each other.

3. The construction method of screw piles in soft strata according to claim 2, characterized in that: The protective cylinder comprises a hollow cylinder (2), a plurality of vertical slide grooves (201) are provided on the circumference of the cylinder (2), a plurality of through holes (202) are provided on the cylinder (2) and are spaced apart from each other and are interconnected with the vertical slide grooves (201), a vertical slide bar (3) is arranged in the vertical slide groove (201), and a plurality of cutting blocks (301) are arranged on the vertical slide bar (3) for passing through the through holes (202) and extending outside the cylinder (2) for spiral cutting the wall of the pile hole; the upper end of the vertical slide bar (3) extends out of the vertical slide groove (201) and is connected to a connecting cylinder (4) for connecting to a power head (01) of a long spiral drilling machine; when the vertical slide bar (3) slides in the vertical slide groove (201), a distance can be provided between the bottom of the vertical slide bar (3) and the bottom of the vertical slide groove (201).

4. The construction method of screw piles in soft strata according to claim 3, characterized in that: A plurality of wear-resistant elastic blocks (302) are installed on the side of the vertical slide bar (3) facing the through hole (202), and the wear-resistant elastic blocks (302) are adapted to the through hole (202); a wear-resistant elastic member (303) is arranged on the other side of the vertical slide bar (3), and the elastic force applied by the wear-resistant elastic member (303) to the vertical slide bar (3) is greater than the force applied by the wear-resistant elastic block (302) to the vertical slide bar (3).

5. The construction method of screw piles in soft strata according to claim 4, characterized in that: The lower end of the connecting tube (4) is provided with a plurality of sliding grooves (401) along the radial direction of the connecting tube (4), and a sliding block (402) capable of sliding in the sliding groove is arranged in the sliding groove (401), and the upper end of each vertical sliding strip (3) is connected to the sliding block (402).

6. The construction method of screw piles in soft strata according to claim 5, characterized in that: The upper end of the cylinder (2) is connected to an extension cylinder (5), the inner wall of the extension cylinder (5) is provided with a plurality of vertically arranged tooth grooves (501), and the periphery of the connecting cylinder (4) is provided with a plurality of tooth rings (403) that are adapted to the tooth grooves (501).

7. The construction method of screw piles in soft strata according to any one of claims 2 to 6, characterized in that: The lower end of the spiral drill rod (1) extends out of the lower end of the protective cylinder body (2), and the lower end of the cylinder body (2) is formed with a tip, and cutting teeth (203) are distributed around the outer periphery of the tip.

8. The construction method of screw piles in soft strata according to claim 7, characterized in that: The distance that the auger rod (1) extends out of the lower end surface of the cylinder (2) is less than or equal to 1 m, the distance between the lowest through hole (202) on the cylinder (2) and the bottom of the cylinder (2) is greater than or equal to 1 m, and the highest through hole (202) on the cylinder (2) has a distance from the top of the cylinder (2).

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