Under-reamed bit and construction method based on the under-reamed bit

Abstract

The present invention discloses an under-reaming bit and a construction method based on the under-reaming bit. The under-reaming bit includes a main shaft and a base. One or more cutting members are installed on the base and can be converted between a retracted state and an extended state by rotation. When in the retracted state, the cutting members swing radially inward to retract, and when in the extended state, the cutting members swing radially outward to open. A driving mechanism is installed on the main shaft and is driven by the rock and soil to act when the main shaft rotates forward to drive the cutting members to rotate to the extended state, and is driven by the rock and soil to act when the main shaft rotates backward to drive the cutting members to rotate to the retracted state. The construction method includes the methods of using the under-reaming bit for under-reaming drilling construction, prestressed pipe pile sinking construction, and cast-in-place pile construction. The present invention has the advantages of simple structure, convenient operation, stable and reliable work, being able to perform under-reaming drilling with upward movement, improving drilling efficiency, and reducing drilling difficulty, etc.

Description

Technical Field

[0001] The present invention relates to the technical field of drilling, and particularly relates to an under-reaming bit and a construction method based on the under-reaming bit. Background Art

[0002] During the construction of the hole-forming operation in building foundation engineering, it is often necessary to use an under-reaming bit to drill a section of the borehole with an enlarged diameter at the bottom of the borehole. The existing under-reaming bit is composed of under-reaming wings, a pressure frame, a connecting rod, a base, and a pin shaft. When drilling and under-reaming, the under-reaming bit is driven to rotate by the drilling rig, and at the same time, the drilling rig applies a downward pressure to gradually open the under-reaming wings to cut the hole wall for under-reaming. This type of under-reaming bit has a complex structure, high cost, high manufacturing difficulty, and high operation difficulty. At the same time, since the under-reaming wings are opened by the downward pressure of the drilling rig to achieve under-reaming, the opening degree of the under-reaming wings cannot be accurately controlled, resulting in the inability to accurately control the diameter of the borehole section to be under-reamed, and the demand for accurate under-reaming cannot be met. Moreover, this type of under-reaming bit can only cut the hole wall for under-reaming, and it is necessary to first drill a basic hole and then cut the hole wall of the basic hole to achieve under-reaming. It also does not have the function of taking out the soil, and it is necessary to cooperate with other bits with the function of taking soil to take out the cut soil, which is inconvenient to use and has low efficiency.

[0003] Chinese Patent with the application number 202110909701.7 discloses an under-reaming bit, which is provided with a cutting member and a driving mechanism on the barrel-shaped body of the bit. When the barrel-shaped body rotates forward to drill a hole, the driving mechanism is pushed by the soil to drive the cutting member to rotate to the extended state. When the barrel-shaped body rotates backward to drill a hole, the driving mechanism is pushed by the soil to drive the cutting member to rotate to the retracted state, so as to achieve under-reaming and recovery after under-reaming. However, this type of under-reaming bit in the form of a barrel drill uses the drilling equipment to press the barrel-shaped body downward from top to bottom for drilling, which has the disadvantages of large resistance, low drilling efficiency, and difficult slag discharge. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies existing in the prior art, and provide an under-reaming bit with a simple structure, easy operation, stable and reliable work, capable of performing under-reaming drilling in a bottom-up movement, improving the drilling efficiency, and reducing the drilling difficulty. A corresponding construction method based on the under-reaming bit is also provided.

[0005] To solve the above technical problems, the present invention adopts the following technical solutions:

[0006] An under-reaming bit, comprising a main shaft and a base provided at the lower end of the main shaft and extending radially outward along the radial direction of the main shaft. One or more cutting members are installed on the base and can be converted between a retracted state and an extended state by rotation. When in the retracted state, the cutting members swing radially inward relative to the axis of the main shaft to retract, and when in the extended state, the cutting members swing radially outward relative to the axis of the main shaft to open. A driving mechanism is installed on the main shaft and is pushed by the rock and soil during the forward rotation of the main shaft to drive the cutting members to rotate to the extended state, and is pushed by the rock and soil during the reverse rotation of the main shaft to drive the cutting members to rotate to the retracted state.

[0007] As a further improvement of the above under-reaming bit:

[0008] The driving mechanism includes a driving member and a rotating rod rotatably installed on the main shaft. The driving member is installed on the rotating rod and is located below the base, and the driving member can be pushed by the rock and soil during the forward and reverse rotations of the main shaft to drive the rotating rod to rotate relative to the main shaft accordingly. Each cutting member is connected to the rotating rod through a linkage mechanism and is driven by the rotating rod to rotate to convert between the retracted state and the extended state.

[0009] The driving member includes a first spiral installed on the rotating rod, and the first spiral lifts the rock and soil upward when rotating in the forward rotation direction of the main shaft.

[0010] One end of the rotating rod away from the base is provided with an insertion member for inserting into the rock and soil.

[0011] The insertion member is a first pick.

[0012] One end of the first spiral away from the base is provided with a second pick.

[0013] The second pick is arranged along the winding direction of the first spiral.

[0014] The driving member includes a soil collecting bucket installed on the rotating rod. The soil collecting bucket has a soil receiving cavity with an upward opening, and the bottom surface of the soil collecting bucket is provided with a pushing member for contacting the rock and soil to be pushed by the rock and soil to drive the soil collecting bucket to rotate.

[0015] The soil collecting bucket is provided with a soil discharge port for discharging the rock and soil in the soil receiving cavity and a door plate movably installed for opening and closing the soil discharge port.

[0016] The soil discharge port is provided on the bottom surface of the soil collecting bucket. The door plate is rotatably installed on the bottom surface of the soil collecting bucket and can open and close the soil discharge port by rotation. The bottom surface of the soil collecting bucket is further provided with a convex member for blocking the door plate to keep the door plate closed to the soil discharge port. The door plate and the convex member serve as the pushing member.

[0017] The convex member is a rib extending along the radial direction of the soil collecting bucket.

[0018] The driving member is detachably connected to the rotating rod through a detachable connection mechanism.

[0019] The detachable connection mechanism includes a plug hole provided at the lower end of the rotating rod, a plug head provided on the driving member and inserted into the plug hole, and a detachable connection assembly for fixing the plug head and the rotating rod.

[0020] The plug hole is a non-circular hole, and the plug head is a non-cylindrical joint that is inserted and cooperated with the non-circular hole and prevents relative rotation.

[0021] The detachable connection assembly includes a plugging positioning member, a first positioning hole provided on the rotating rod, and a second positioning hole provided on the plug head. The plugging positioning member is detachably inserted into the first positioning hole and the second positioning hole.

[0022] The main shaft is provided with a through hole that axially penetrates. The rotating rod is rotatably installed in the through hole. The rotating rod is provided with a positioning portion that abuts against the lower end of the main shaft, and the rotating rod is threadedly connected with a positioning nut that abuts against the upper end of the main shaft.

[0023] The upper end of the main shaft is connected with a connection head for connecting the drill rod of the drilling equipment. The connection head has a counterbore-shaped inner cavity for inserting and installing the drill rod, and the positioning nut is located in the counterbore-shaped inner cavity.

[0024] The connection head is provided with an observation and maintenance hole for observing the area where the positioning nut is located and inserting a tool to loosen or tighten the positioning nut.

[0025] The connection head is provided with a pin hole for inserting a locking member to connect and fasten the connection head and the drill rod.

[0026] The linkage mechanism includes a connecting rod and a swing arm connected to the rotating rod. One end of the connecting rod is hinged to the swing arm, and the other end of the connecting rod is hinged to the cutting member.

[0027] The connecting rod and the swing arm are located on the side of the base opposite to the main shaft.

[0028] A second spiral for lifting the rock and soil is provided on the main shaft when the main shaft rotates in the reverse direction.

[0029] The radial dimension of the second spiral gradually decreases in the direction from bottom to top.

[0030] The radial dimension of the upper part of the second spiral is smaller than the radial dimension of the lower part of the second spiral.

[0031] The cutting member is provided with a soil gathering portion that gathers the rock and soil towards the axis direction of the main shaft when switching from the extended state to the retracted state.

[0032] The soil gathering part includes two side plates respectively arranged on both sides of the cutting body part, and each side plate is provided with a third pick for cutting rock and soil when the cutting body part is in the extended state.

[0033] The cutting body part is provided with a forced retraction drive inclined surface for contacting with rock and soil when the under-reaming bit is lifted upward to force the cutting body part to rotate towards the retracted state.

[0034] The cutting body part is provided with a forming surface for forming a conical surface at the bottom of the hole when the cutting body part is in the extended state.

[0035] A positioning mechanism is provided between the base and the cutting body part to position the cutting body part at at least one angle when the cutting body part swings outward and opens.

[0036] The positioning mechanism includes a first positioning part and a second positioning part arranged on the cutting body part. The first positioning part contacts the base when the cutting body part swings outward and opens to the first angle to prevent the cutting body part from continuing to rotate from the retracted state to the extended state. The second positioning part is installed on the cutting body part in a manner that can be adjusted and converted between a blocking angle and a releasing angle. The second positioning part contacts the base at the blocking angle to block the cutting body part that swings outward and opens at the second angle, and the second angle is smaller than the first angle. The second positioning part allows the cutting body part to swing to the first angle at the releasing angle.

[0037] An installation hole is provided on the cutting body part. The second positioning part is connected with an adjustment shaft, and the adjustment shaft is installed on the cutting body part in a manner that can rotate and move along the center line of the installation hole. A rotation prevention protrusion is provided on the adjustment shaft, and a rotation prevention part is also provided on the cutting body part. The rotation prevention part is provided with a first rotation prevention groove for the rotation prevention protrusion to insert when the second positioning part is at the blocking angle to prevent the adjustment shaft from rotating and a second rotation prevention groove for the rotation prevention protrusion to insert when the second positioning part is at the releasing angle to prevent the adjustment shaft from rotating.

[0038] A locking part is also provided on the cutting body part for the second positioning part to be locked into when the second positioning part is at the blocking angle to prevent the adjustment shaft from rotating.

[0039] The positioning mechanism includes a third positioning part arranged on the cutting body part. The third positioning part contacts the base when the cutting body part swings outward and opens to the third angle to prevent the cutting body part from continuing to rotate from the retracted state to the extended state.

[0040] The base is provided with an earth passing channel for rock and soil to pass through and fall below the base.

[0041] The cutting body part blocks the earth passing channel when in the retracted state and opens the earth passing channel when in the extended state.

[0042] The base is provided with soil-passing channels corresponding to each cutting body member. When each cutting body member is in the retracted state, it blocks the corresponding soil-passing channel, and when each cutting body member is in the extended state, it opens the corresponding soil-passing channel.

[0043] The soil-passing channel is a through hole or a notch provided on the base.

[0044] As a general technical concept, the present invention also provides an under-reamed drilling construction method based on the above under-reaming bit. The under-reaming construction method is as follows: after drilling a basic hole in the foundation using a drilling bit, the drilling bit is taken out; then, the under-reaming bit is used to perform an under-reaming operation once, cutting the rock and soil layers of the under-reamed hole section to be constructed at one time, so as to drill an under-reamed hole section with a preset height at the bottom of the basic hole; or the rock and soil of the under-reamed hole section to be constructed is divided into multiple layers of annular rock and soil layers from the inside to the outside, and the multiple layers of annular rock and soil layers are cut in sequence from the inside to the outside until an under-reamed hole section with a preset height is drilled at the bottom of the basic hole. Each time a layer of annular rock and soil layer is cut, the under-reaming bit is used to perform an under-reaming operation once.

[0045] When using the under-reaming bit to perform each under-reaming operation, the under-reaming bit moves upward from bottom to top while rotating forward, drilling an under-reamed hole section with a preset height in the basic hole at one time; or the under-reaming bit first moves upward from bottom to top while rotating forward, and then moves up and down repeatedly until an under-reamed hole section with a preset height is drilled in the basic hole.

[0046] As a further improvement of the above under-reamed drilling construction method:

[0047] Using the under-reaming bit to perform each under-reaming operation includes the following steps:

[0048] (S11) Use a drilling device to drive the under-reaming bit with the cutting body members in the retracted state to extend into the bottom of the basic hole, so that the driving mechanism contacts the rock and soil at the bottom of the basic hole. Then, the drilling device drives the main shaft of the under-reaming bit to rotate forward, and the driving mechanism acts under the push of the rock and soil to drive the cutting body members to rotate to the extended state.

[0049] (S12) While the drilling device keeps driving the main shaft to rotate forward, lift the main shaft in the direction from bottom to top, drilling an under-reamed hole section with a preset height in the basic hole at one time; or first lift the main shaft in the direction from bottom to top, and then make the main shaft move up and down repeatedly until an under-reamed hole section with a preset height is drilled in the basic hole.

[0050] (S13) The drilling device drives the main shaft of the under-reaming bit to rotate reversely, and the driving mechanism acts under the push of the rock and soil to drive the cutting body members to rotate to the retracted state, and lift the under-reaming bit out of the basic hole.

[0051] In the step (S13), when the cutting body is rotated to the retracted state, first use the drilling equipment to drive the main shaft of the under-reaming bit to move downward so that the driving mechanism exerts pressure on the rock and soil at the lower part of the under-reamed hole section, and then drive the main shaft of the under-reaming bit to rotate in the reverse direction.

[0052] As a general technical concept, the present invention also provides a pile driving construction method for prestressed pipe piles, including the following steps:

[0053] (S21) Use the method of synchronous construction of drilling with a drilling bit and pile driving to drive the prestressed pipe pile into the foundation to a first depth, and this first depth is less than the designed pile driving depth;

[0054] (S22) Stop driving the prestressed pipe pile, and use the drilling bit to continue drilling to form a pilot hole section until it is not less than the designed pile driving depth;

[0055] (S23) Use the above under-reamed drilling construction method to drill an under-reamed hole section with a preset height at the bottom of the pilot hole section, wherein the pilot hole section serves as the basic hole;

[0056] (S24) Drive the prestressed pipe pile to the designed pile driving depth.

[0057] As a further improvement of the above pile driving construction method:

[0058] Before step (S24) and after step (S23), first fill the under-reamed hole section with concrete, and then drive the prestressed pipe pile to the designed pile driving depth.

[0059] As a general technical concept, the present invention also provides a cast-in-place pile construction method, including the following steps:

[0060] (S31) Construct a cast-in-place pile hole in the foundation. The cast-in-place pile hole is composed of multiple sub-hole sections connected in sequence along the depth direction. The sub-hole section includes a basic hole section and an under-reamed section located at the bottom of the basic hole section, and the aperture of the under-reamed section is larger than that of the basic hole section;

[0061] Construct each sub-hole section in sequence from top to bottom until the cast-in-place pile hole is obtained. Each sub-hole section is obtained by using the above under-reamed drilling construction method, wherein the basic hole section serves as the basic hole and the under-reamed section serves as the under-reamed hole section;

[0062] (S32) Clean the soil residues at the bottom of the cast-in-place pile hole;

[0063] (S33) Place a steel reinforcement cage in the cast-in-place pile hole and pour concrete to form a pile.

[0064] Compared with the prior art, the advantages of the present invention are as follows:

[0065] The under-reaming bit of the present invention uses a driving mechanism that can be actuated by rock and soil to drive the cutting member to switch between the extended state and the retracted state, without the need for other forms of driving power and driving structures. It has a simple structure, is easy to operate, works stably and reliably, and has strong practicability. Moreover, the cutting member can rotate accurately, stably and reliably to the retracted state or the extended state, without problems such as inaccurate or unstable rotation positions of the cutting member, which can ensure the accuracy of the hole diameter and at the same time ensure that the bit can be smoothly taken out, greatly improving the smoothness and efficiency of the drilling operation. More importantly, the under-reaming bit can perform under-reaming drilling at the bottom of the borehole in a bottom-to-top movement manner. And because the base extends outward in the radial direction of the main shaft, there is a space around the main shaft above the base. During the process of the cutting member switching to the extended state for under-reaming drilling, the rock and soil cut by the cutting member can not only fall downward, but also enter the space above the base, which can reduce the resistance suffered by the cutting member in cutting the rock and soil, thereby improving the drilling efficiency, reducing the drilling difficulty, and avoiding problems such as difficult drilling and inability to drill. And because only the base is provided to install the cutting member, it is convenient for the design and arrangement of the driving mechanism and the cutting member, and it can achieve a smaller size when the cutting member is in the retracted state and a larger under-reaming diameter when the cutting member is in the extended state. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 Fig. 6 is a perspective structural view of the under-reaming bit in Example 1 when the cutting member is in the retracted state.

[0067] Figure 2 Fig. 10 is a front structural view of the under-reaming bit in Example 1 when the cutting member is in the retracted state.

[0068] Figure 3 Fig. 14 is a bottom structural view of the under-reaming bit in Example 1 when the cutting member is in the retracted state.

[0069] Figure 4 Fig. 18 is a perspective structural view of the under-reaming bit in Example 1 when the cutting member is in the extended state.

[0070] Figure 5 Fig. 22 is a front structural view of the under-reaming bit in Example 1 when the cutting member is in the extended state.

[0071] Figure 6 Fig. 26 is a sectional structural view of the under-reaming bit in Example 1 when the cutting member is in the extended state.

[0072] Figure 7 Fig. 30 is a bottom structural view of the under-reaming bit in Example 1 when the cutting member is in the extended state.

[0073] Figure 8 Fig. 34 is a perspective structural view of the main shaft in Example 1.

[0074] Figure 9Partial top view structural schematic diagram when the cutting body is positioned by the second positioning member in Embodiment 1.

[0075] Figure 10 Partial three-dimensional structural schematic diagram when the cutting body is positioned by the second positioning member in Embodiment 1.

[0076] Figure 11 Partial three-dimensional structural schematic diagram when the cutting body is positioned by the first positioning member in Embodiment 1.

[0077] Figure 12 Three-dimensional structural schematic diagram of the under-reaming bit when the cutting body is in the extended state in Embodiment 2.

[0078] Figure 13 Front view structural schematic diagram of the under-reaming bit when the cutting body is in the extended state in Embodiment 2.

[0079] Figure 14 Cross-sectional view structural schematic diagram of the under-reaming bit when the cutting body is in the extended state in Embodiment 2.

[0080] Figure 15 Three-dimensional structural schematic diagram of the under-reaming bit when the cutting body is in the retracted state in Embodiment 2.

[0081] Figure 16 Exploded structural schematic diagram of the under-reaming bit in Embodiment 3.

[0082] Figure 17 Structural schematic diagram of drilling the basic hole in Embodiment 4.

[0083] Figure 18 Structural schematic diagram of inserting the under-reaming bit into the basic hole in Embodiment 4.

[0084] Figure 19 Structural schematic diagram of the under-reaming bit drilling the basic hole in Embodiment 4.

[0085] Figure 20 Structural schematic diagram of obtaining the under-reamed empty section during construction in Embodiment 4.

[0086] Figure 21 Structural schematic diagram of pouring the cast-in-place pile hole in Embodiment 6.

[0087] Figure 22 Structural schematic diagram of using a hole cleaning drill to clean the rock and soil in the cast-in-place pile hole in Embodiment 6.

[0088] Figure 23 Structural schematic diagram of placing the steel reinforcement cage in the cast-in-place pile hole in Embodiment 6.

[0089] Figure 24 Structural schematic diagram after pile formation in Embodiment 6.

[0090] Legend Explanation:

[0091] 1. Main shaft; 11. Through hole; 12. Connector; 121. Counterbore inner cavity; 122. Observation and maintenance hole; 123. Pin hole; 13. Second helix; 2. Base; 21. Soil-passing channel; 3. Cutting body part; 31. Soil-gathering part; 32. Third cutting tooth; 33. Forced retraction driving slope; 34. Forming surface; 35. First positioning part; 36. Second positioning part; 361. Adjusting shaft; 362. Anti-rotation projection; 37. Anti-rotation part; 371. First anti-rotation groove; 372. Second anti-rotation groove; 38. Locking part; 4. Driving mechanism; 41. Rotating rod; 411. Insertion hole; 412. Positioning part; 42. First helix; 43. First cutting tooth; 44. Second cutting tooth; 45. Soil-collecting bucket; 451. Soil-containing cavity; 452. Soil-discharging port; 453. Door panel; 454. Protruding part; 46. Connecting rod; 47. Swing arm; 301. Drilling bit; 401. Foundation; 402. Base hole; 403. Under-reamed hole section; 405. Base hole section; 406. Reaming section. Detailed Implementation Manner

[0092] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0093] Embodiment 1:

[0094] As Figures 1 to 11 shown, the under-reaming bit of this embodiment includes a main shaft 1 and a base 2 provided at the lower end of the main shaft 1. The base 2 extends outward in the radial direction of the main shaft 1. One or more cutting body parts 3 that can be rotated to switch between a retracted state and an extended state are installed on the base 2. When the cutting body parts 3 are in the retracted state, they swing radially inward relative to the axis of the main shaft 1 to retract. When the cutting body parts 3 are in the extended state, they swing radially outward relative to the axis of the main shaft 1 to open. When the cutting body parts 3 are in the extended state, there is a soil-passing hole between the base 2 and the cutting body parts 3 for soil and rock to pass through and fall below the cutting body parts 3. A driving mechanism 4 is installed on the main shaft 1, which is pushed by the soil and rock during the forward rotation of the main shaft 1 to drive the cutting body parts 3 to rotate to the extended state, and is pushed by the soil and rock during the reverse rotation of the main shaft 1 to drive the cutting body parts 3 to rotate to the retracted state.

[0095] When this under-reaming bit is used for under-reaming drilling, first rotate each cutting body part 3 to the retracted state, connect the main shaft 1 to a drilling device (drill rig), and drive it by the drill rig to extend to the depth position that needs to be under-reamed in the drilling hole, so that the driving mechanism 4 contacts the soil and rock at the bottom of the drilling hole. Then, use the drill rig to drive the main shaft 1 to rotate forward. Under the pushing action of the soil and rock, the driving mechanism 4 will drive the cutting body parts 3 to rotate to the extended state, and the cutting body parts 3 will swing radially outward relative to the axis of the main shaft 1 to open (see Figures 4 to 7), and thus under-reamed drilling can be realized; after the under-reamed drilling is completed, the drill is used to drive the main shaft 1 to rotate in the reverse direction. Under the pushing action of the rock and soil, the driving mechanism 4 will drive the cutting body 3 to rotate towards the retracted state, and the cutting body 3 will swing radially inwards relative to the axis of the main shaft 1 and retract (see Figures 1 to 3 ). At this time, the under-reamed bit can be smoothly lifted out of the borehole. The under-reamed bit of the present invention uses a driving mechanism 4 that can be actuated by rock and soil to drive the cutting body 3 to switch between the extended state and the retracted state, without the need for other forms of driving power and driving structure. It has a simple structure, is easy to operate, works stably and reliably, and has strong practicability. Moreover, the cutting body 3 can accurately, stably and reliably rotate to the retracted state or the extended state, without problems such as inaccurate or unstable rotation position of the cutting body 3, which can ensure the accuracy of the borehole diameter and at the same time ensure that the bit can be smoothly removed, greatly improving the smoothness and efficiency of the drilling operation. More importantly, the under-reamed bit can perform under-reamed drilling at the bottom of the borehole in a manner of moving from bottom to top. And because the base 2 extends outwards in the radial direction of the main shaft 1, there is a space around the main shaft 1 above the base 2. During the process of the cutting body 3 switching to the extended state for under-reamed drilling, the rock and soil cut by the cutting body 3 can not only fall downwards, but also enter the space above the base 2, which can reduce the resistance of the cutting body 3 to cutting rock and soil, thereby improving the drilling efficiency, reducing the drilling difficulty, and avoiding problems such as difficult drilling and inability to drill. And because only the base 2 is provided to install the cutting body 3, it is convenient for the design and arrangement of the driving mechanism 4 and the cutting body 3, and it can achieve a smaller size when the cutting body 3 is in the retracted state and a larger under-reamed diameter when in the extended state.

[0096] Preferably, the base 2 is a flat plate structure perpendicular to the main shaft 1, which is more conducive to the rock and soil cut by the cutting body 3 entering the space above the base 2.

[0097] In this embodiment, the driving mechanism 4 includes a driving member and a rotating rod 41 rotatably mounted on the main shaft 1. The driving member is mounted on the rotating rod 41 and is located below the base 2. When the main shaft 1 rotates forward and backward, the driving member can be pushed by the rock and soil to drive the rotating rod 41 to rotate relative to the main shaft 1 accordingly. Each cutting member 3 is connected to the rotating rod 41 through a linkage mechanism and is driven by the rotating rod 41 to rotate to switch between the retracted state and the extended state. When the main shaft 1 rotates forward, the driving member contacts the rock and soil and is pushed by the rock and soil, causing the rotating rod 41 to rotate relative to the main shaft 1, and the rotating direction of the rotating rod 41 is opposite to the forward rotation direction of the main shaft 1. Thus, the cutting member 3 is driven to rotate towards the extended state through the linkage mechanism. When the main shaft 1 rotates backward, the driving member contacts the rock and soil and is pushed by the rock and soil, causing the rotating rod 41 to rotate relative to the main shaft 1, and the rotating direction of the rotating rod 41 is opposite to the backward rotation direction of the main shaft 1. Thus, the cutting member 3 is driven to rotate towards the retracted state through the linkage mechanism. This driving mechanism 4 has the advantages of simple and compact structure, stable and reliable operation, and provides a larger space for accommodating rock and soil below the cutting member 3.

[0098] In this embodiment, the driving member includes a first screw 42 mounted on the rotating rod 41. When the first screw 42 rotates along the forward rotation direction of the main shaft 1, it lifts the rock and soil upward. On the one hand, when the main shaft 1 rotates forward and backward, the first screw 42 can be pushed by the rock and soil to drive the rotating rod 41 to rotate relative to the main shaft 1 accordingly. On the other hand, after the cutting member 3 rotates completely to the extended state, it will rotate along with the forward rotation of the main shaft 1, that is, along the forward rotation direction of the main shaft 1. At this time, it plays a role in lifting the rock and soil upward, which can provide more space for accommodating rock and soil below the cutting member 3, and avoid the rock and soil cut during the under-reaming drilling process from not being able to fall below the cutting member 3, further reducing the resistance. In addition, using the first screw 42 as the driving member, it has a simple and compact structure and low cost.

[0099] In this embodiment, an insertion member for inserting into the rock and soil is provided at one end of the rotating rod 41 away from the base 2. Preferably, the insertion member is a first pick 43. The first pick 43 can insert into the rock and soil, providing a reliable acting force for driving the rotation of the rotating rod 41. In cooperation with the first screw 42, it can ensure that the rotating rod 41 rotates relative to the main shaft 1 stably and reliably, thereby ensuring that the cutting member 3 stably and reliably switches between the retracted state and the extended state. In other embodiments, the insertion member can also adopt other structural members that can insert into the rock and soil, such as bumps, etc.

[0100] In this embodiment, a second pick 44 is provided at one end of the first helix 42 away from the base 2. The second pick 44 is beneficial for the first helix 42 to lift the rock and soil, and at the same time provides a more reliable acting force to drive the rotating rod 41 to rotate so that the cutting member 3 moves to the extended state. Preferably, the second pick 44 is arranged along the winding direction of the first helix 42, and the effect of lifting the rock and soil and providing the acting force to drive the rotating rod 41 to rotate is better.

[0101] In this embodiment, the main shaft 1 is provided with a through hole 11 that penetrates axially. The rotating rod 41 is rotatably installed in the through hole 11. The rotating rod 41 is provided with a positioning portion 412 that abuts against the lower end of the main shaft 1. The rotating rod 41 is threadedly connected with a positioning nut (not shown in the figure) that abuts against the upper end of the main shaft 1. This installation structure and method have the advantages of simple and compact structure, stable and reliable connection, convenient manufacturing and assembly maintenance, and can save the space below the cutting member 3.

[0102] In this embodiment, a connecting head 12 for connecting the drill pipe of the drilling equipment is connected to the upper end of the main shaft 1. The connecting head 12 has a counterbore inner cavity 121 for inserting and installing the drill pipe. The positioning nut is located in the counterbore inner cavity 121. The setting of the connecting head 12 facilitates the connection of the drill pipe of the drilling equipment, and the positioning nut located in the counterbore inner cavity 121 can further improve the structural compactness and play a protective role for the positioning nut, and can avoid problems such as wear and loosening of the positioning nut.

[0103] In this embodiment, the connecting head 12 is provided with an observation and maintenance hole 122 for observing the area where the positioning nut is located and inserting a tool to tighten or loosen the positioning nut. Through the observation and maintenance hole 122, it is not only convenient to observe the structure of the positioning nut and the nearby area, but also convenient to insert a tool to tighten or loosen the positioning nut and perform maintenance.

[0104] In this embodiment, the connecting head 12 is provided with a pin hole 123 for inserting a locking member to connect and fasten the connecting head 12 and the drill pipe, which is convenient for inserting locking members such as pins or screws to connect and fasten the connecting head 12 and the drill pipe, and improves the convenience of loading and unloading the connecting head 12 and the drill pipe.

[0105] In this embodiment, as Figure 4 shown, the linkage mechanism includes a connecting rod 46 and a swing arm 47 connected to the rotating rod 41. One end of the connecting rod 46 is hinged to the swing arm 47, and the other end of the connecting rod 46 is hinged to the cutting member 3. When the rotating rod 41 rotates, it drives the swing arm 47 to rotate synchronously. The swing arm 47 drives the cutting member 3 to rotate correspondingly through the connecting rod 46. This linkage mechanism adopts the combination of the swing arm 47 and the connecting rod 46, and has the advantages of simple structure, low cost, easy manufacturing and assembly, and good stress performance.

[0106] In this embodiment, the connecting rod 46 and the swing arm 47 are located on the side of the base 2 opposite to the main shaft 1. During the process of under-reaming drilling, the connecting rod 46 and the swing arm 47 will not be squeezed by the rock and soil, which can avoid deformation and damage and ensure stable and reliable operation. Of course, in other embodiments, the connecting rod 46, the swing arm 47 and the main shaft 1 can also be located on the same side of the base 2. Preferably, the above swing arm 47 also serves as the positioning portion 412 at the same time, making the structure simpler, more compact and with lower cost.

[0107] In this embodiment, a second helix 13 for lifting the rock and soil is provided on the main shaft 1 when the main shaft 1 rotates in the reverse direction. When the main shaft 1 rotates in the reverse direction to make the cutting body 3 rotate towards the retracted state, the second helix 13 synchronously plays the role of lifting the rock and soil, and can lift and accommodate as much rock and soil generated by the under-reaming drilling as possible, reducing the residue of the rock and soil.

[0108] In this embodiment, the radial dimension of the second helix 13 gradually decreases in the direction from bottom to top. During the process of under-reaming drilling while moving from bottom to top, it can avoid the second helix 13 from scraping against the hole wall of the original hole and prevent hindering the upward movement. In other embodiments, it can also be that the radial dimension of the upper part of the second helix 13 is smaller than that of the lower part of the second helix 13, which can also avoid the second helix 13 from scraping against the hole wall of the original hole and prevent hindering the upward movement.

[0109] In this embodiment, the cutting body 3 is provided with a soil gathering portion 31 for gathering the rock and soil towards the axis direction of the main shaft 1 when switching from the extended state to the retracted state. When the cutting body 3 switches from the extended state to the retracted state, the soil gathering portion 31 gathers the rock and soil towards the middle of the hole, facilitating the subsequent cleaning of the rock and soil. When the second helix 13 is cooperatively provided, the soil gathering portion 31 also makes the rock and soil rise upwards during the process of gathering the rock and soil, facilitating the rock and soil to be lifted by the second helix 13, thereby further reducing the residue of the rock and soil.

[0110] In this embodiment, the soil gathering portion 31 includes two side plates respectively arranged on both sides of the cutting body 3, and each side plate is provided with a third pick 32 for cutting the rock and soil when the cutting body 3 is in the extended state. The soil gathering portion 31 adopts the form of two side plates respectively arranged on both sides of the cutting body 3, which not only has a simple structure, good effect of gathering the rock and soil, but also has good mechanical properties. After the cutting body 3 opens at a certain angle towards the extended state, the two side plates can also better contact with the rock and soil to provide the acting force for driving the cutting body 3 to open subsequently, ensuring stable opening. The side plates are provided with third picks 32, which can be inserted into the rock and soil to provide reliable driving force.

[0111] In this embodiment, the cutting member 3 is provided with a forced retraction driving inclined surface 33 for contacting the rock and soil when the under-reaming bit is lifted upward to force the cutting member 3 to rotate towards the retracted state. When the driving mechanism 4 jams or the force that hinders the cutting member 3 from rotating towards the retracted state due to the rock and soil is too large, resulting in the cutting member 3 being unable to completely rotate to the retracted state, during the process of lifting the under-reaming bit upward, the forced retraction driving inclined surface 33 will contact the upper rock and soil, and under the action of the rock and soil, force the cutting member 3 to rotate towards the retracted state, ensuring that the under-reaming bit can be smoothly withdrawn. Especially when lifting while cooperating with the rotation of the main shaft 1, it can more effectively and reliably force the cutting member 3 to rotate towards the retracted state.

[0112] In this embodiment, the cutting member 3 is provided with a forming surface 34 for forming a conical surface at the bottom of the hole when the cutting member 3 is in the extended state. By forming a conical surface at the bottom of the hole through the forming surface 34, it is convenient for the rock and soil generated during the under-reaming drilling when lifting upward to slide down to the middle position of the hole, facilitating the subsequent cleaning of the rock and soil.

[0113] In this embodiment, a positioning mechanism is provided between the base 2 and the cutting member 3 to position the cutting member 3 at at least one angle when the cutting member 3 swings outward and opens. Through the positioning mechanism, it is ensured that the cutting member 3 is stably in the extended state, guaranteeing the accuracy of under-reaming drilling.

[0114] In this embodiment, referring to Figure 1 、 Figures 9 to 11 , the positioning mechanism includes a first positioning member 35 and a second positioning member 36 provided on the cutting member 3. The first positioning member 35 contacts the base 2 when the cutting member 3 swings outward and opens to the first angle to prevent the cutting member 3 from continuing to rotate from the retracted state to the extended state; the second positioning member 36 is installed on the cutting member 3 in a manner that can be adjusted and switched between a blocking angle and a releasing angle. The second positioning member 36 contacts the base 2 at the blocking angle to block the cutting member 3 that swings outward and opens at the second angle, and the second angle is smaller than the first angle. The second positioning member 36 allows the cutting member 3 to swing towards the first angle at the releasing angle. By adjusting and switching the second positioning member 36 to the blocking angle, the second positioning member 36 can contact the base 2 to block and position the cutting member 3 that swings outward and opens at the second angle. By adjusting and switching the second positioning member 36 to the releasing angle, the second positioning member 36 allows the cutting member 3 to swing through the second angle towards the first angle, so as to utilize the contact between the first positioning member 35 and the base 2 to block and position the cutting member 3 that swings outward and opens at the first angle. Therefore, positioning at different angles in the extended state of the cutting member 3 can be achieved to meet the requirements of under-reaming drilling with different hole diameters, and its structure is simple and the operation is convenient.

[0115] In this embodiment, the cutting body member 3 is provided with a mounting hole. The second positioning member 36 is connected with an adjusting shaft 361. The adjusting shaft 361 is mounted on the cutting body member 3 in a manner that it can rotate and move along the center line of the mounting hole. A rotation-preventing protrusion 362 is provided on the adjusting shaft 361. The cutting body member 3 is further provided with a rotation-preventing member 37. The rotation-preventing member 37 is provided with a first rotation-preventing groove 371 for the rotation-preventing protrusion 362 to insert into when the second positioning member 36 is at the blocking angle to prevent the adjusting shaft 361 from rotating, and a second rotation-preventing groove 372 for the rotation-preventing protrusion 362 to insert into when the second positioning member 36 is at the releasing angle to prevent the adjusting shaft 361 from rotating. This mounting structure and method of the second positioning member 36 have the advantages of simple and compact structure, easy manufacturing, convenient operation, and stable and reliable positioning.

[0116] In this embodiment, the cutting body member 3 is further provided with a locking member 38 for the second positioning member 36 to be clamped into when the second positioning member 36 is at the blocking angle to prevent the adjusting shaft 361 from rotating. This can enhance the positioning effect on the second positioning member 36 and improve the stability and reliability of positioning.

[0117] In other embodiments, the positioning mechanism may also only include a third positioning member provided on the cutting body member 3. The third positioning member contacts the base 2 when the cutting body member 3 swings outwards and opens to the third angle to prevent the cutting body member 3 from continuing to rotate from the retracted state to the extended state. This positioning mechanism can only position the cutting body member 3 in the extended state at the third angle. In other embodiments, more detachable or adjustable positioning members can also be provided so that the cutting body member 3 can be positioned in the extended state at more angles.

[0118] Preferably, the first positioning member 35 and the third positioning member are the aforementioned soil gathering parts 31. There is no need to set up separate structures and components, which is beneficial to improving the simplicity and compactness of the structure, reducing costs, and having stable and reliable positioning.

[0119] In this embodiment, the base 2 is provided with a soil passing channel 21 for the rock and soil to pass through and fall below the base 2. The rock and soil entering the space above the base 2 can pass through the soil channel 21 and fall into the enlarged hole section below the cutting body member 3, which can avoid excessive accumulation of the rock and soil entering the space above the base 2 and subsequent entry of the rock and soil, and further reduce the drilling resistance. Moreover, in cooperation with the cutting body member 3 having the soil gathering part 31 and the second helix 13, when the cutting body member 3 gathers the rock and soil towards the middle of the hole during the process of switching from the extended state to the retracted state, the soil below the base 2 can also move upwards through the soil passing channel 21 to the space above the base 2. Thus, it can avoid the soil below the base 2 from hindering the retraction action of the cutting body member 3, resulting in the cutting body member 3 being unable to be fully retracted. At the same time, the soil below the base 2 moving upwards through the soil passing channel 21 to the space above the base 2 also facilitates the lifting of the rock and soil by the second helix 13, thereby further reducing the residue of the rock and soil.

[0120] In this embodiment, when the cutting body 3 is in the retracted state, it blocks the soil-passing channel 21, and when the cutting body 3 is in the extended state, it opens the soil-passing channel 21. When the cutting body 3 is in the extended state, it opens the soil-passing channel 21, facilitating the falling of the rock and soil below the cutting body 3. When the cutting body 3 is in the retracted state, it blocks the soil-passing channel 21, playing a role in accommodating and carrying out the rock and soil, and reducing the residue of the rock and soil in the hole.

[0121] In this embodiment, the base 2 is provided with a soil-passing channel 21 corresponding to each cutting body 3. When each cutting body 3 is in the retracted state, it blocks the corresponding soil-passing channel 21, and when each cutting body 3 is in the extended state, it opens the corresponding soil-passing channel 21.

[0122] In this embodiment, the soil-passing channel 21 is a notch provided on the base 2. It has a simple structure, is easy to process and manufacture, and has a good soil-passing effect. In other embodiments, through holes can also be provided on the base 2, which can also achieve the falling of the rock and soil in the vertical direction and passing through the base 2.

[0123] Embodiment 2:

[0124] The under-reaming bit of this embodiment is basically the same as that of Embodiment 1. The main difference is that, as Figures 12 to 15 shown, in this embodiment, the driving member includes a soil collecting bucket 45 installed on the rotating rod 41. The soil collecting bucket 45 has a soil-containing cavity 451 with an upward opening. The bottom surface of the soil collecting bucket 45 is provided with a pushing member for contacting the rock and soil to be pushed by the rock and soil to drive the soil collecting bucket 45 to rotate. The driving member adopts the structural form of the soil collecting bucket 45. The soil collecting bucket 45 can receive and accommodate the rock and soil cut during the under-reaming drilling from bottom to top, and then facilitate the bringing out of the rock and soil, reducing the work of cleaning the residual rock and soil subsequently.

[0125] In this embodiment, the soil collecting bucket 45 is provided with a soil discharge port 452 for discharging the rock and soil in the soil-containing cavity 451 and a door plate 453 movably installed for opening and closing the soil discharge port 452. It is convenient to bring out the rock and soil, and it is convenient to control the door plate 453 to discharge the rock and soil in the soil-containing cavity 451 after bringing out the rock and soil.

[0126] In this embodiment, the soil discharge port 452 is provided on the bottom surface of the soil collecting bucket 45. The door plate 453 is rotatably installed on the bottom surface of the soil collecting bucket 45 and can open and close the soil discharge port 452 by rotation. The bottom surface of the soil collecting bucket 45 is further provided with a convex member 454 for blocking the door plate 453 to keep the door plate 453 closed to the soil discharge port 452. The door plate 453 and the convex member 454 serve as the pushing member. Using the door plate 453 and the convex member 454 as the pushing member can simplify the structure, improve the compactness, and reduce the cost.

[0127] In this embodiment, the protruding member 454 is a rib extending in the radial direction of the soil collecting bucket 45. It not only has a good blocking and positioning effect on the door plate 453, but also can be better pushed by the rock and soil to drive the soil collecting bucket 45 to rotate, thereby ensuring the stable conversion of the cutting member 3 to the extended state. In other embodiments, the protruding member 454 can also be a pick, a plurality of spaced convex blocks, etc.

[0128] Embodiment 3:

[0129] The under-reaming bit of this embodiment is basically the same as that of Embodiment 1. The main difference is that, on the basis of Embodiment 1, the under-reaming bit of this embodiment is also equipped with the soil collecting bucket 45 of Embodiment 2. And, in this embodiment, the driving member is detachably connected to the rotating rod 41 through a detachable connection mechanism. In this way, it is convenient to replace the first helix 42 of Embodiment 1 or the soil collecting bucket 45 of Embodiment 2 according to needs.

[0130] In this embodiment, as Figure 16 shown, the detachable connection mechanism includes a socket hole 411 provided at the lower end of the rotating rod 41, a plug head provided on the driving member and inserted into the socket hole 411, and a detachable connection component for fixing the plug head and the rotating rod 41. This detachable connection mechanism has the advantages of simple and compact structure, convenient loading and unloading, stable and reliable connection, and easy manufacturing. Figure 16 The driving member shown is the first helix 42.

[0131] In this embodiment, the socket hole 411 is a non-circular hole, the plug head is a non-cylindrical joint that is inserted and cooperates with the non-circular hole and is relatively anti-rotation. The cooperation between the plug head and the non-circular hole realizes the relative anti-rotation of the driving member and the rotating rod 41, which can ensure the stable and reliable connection between the two, and is conducive to simplifying the detachable connection component.

[0132] In this embodiment, the detachable connection component includes a plugging positioning member, a first positioning hole provided on the rotating rod 41, and a second positioning hole provided on the plug head. The plugging positioning member is detachably inserted into the first positioning hole and the second positioning hole. This detachable connection component has the advantages of simple and compact structure, convenient disassembly and assembly, and stable and reliable connection. Preferably, the above plugging positioning member is a pin or a bolt. In other embodiments, the detachable connection component can also adopt other existing mechanisms that can achieve detachable connection, such as a clamping mechanism or a threaded connection mechanism, etc.

[0133] Embodiment 4:

[0134] An under-reaming drilling construction method based on the under-reaming bit in Embodiment 1 or Embodiment 2, as Figures 17 to 20As shown, the construction method for the enlarged bottom is as follows: after drilling a basic hole 402 in the foundation 401 with a drilling bit 301 and then taking out the drilling bit 301, an enlarged hole operation is performed with an enlarged bottom bit to cut the rock and soil layers of the enlarged bottom hole section 403 to be constructed at one time, so as to drill an enlarged bottom hole section 403 with a preset height at the bottom of the basic hole 402; or the rock and soil of the enlarged bottom hole section 403 to be constructed is divided into multiple layers of annular rock and soil layers from inside to outside, and the multiple layers of annular rock and soil layers are cut in sequence from inside to outside until an enlarged bottom hole section 403 with a preset height is drilled at the bottom of the basic hole 402, and an enlarged hole operation is performed with the enlarged bottom bit for cutting each layer of annular rock and soil layer.

[0135] When performing each enlarged hole operation with the enlarged bottom bit, the enlarged bottom bit moves upward from bottom to top while rotating forward to drill an enlarged bottom hole section 403 with a preset height in the basic hole 402 at one time; or the enlarged bottom bit first moves upward from bottom to top while rotating forward and then moves up and down repeatedly until an enlarged bottom hole section 403 with a preset height is drilled in the basic hole 402.

[0136] In this enlarged bottom drilling construction method, the enlarged bottom bit can perform enlarged bottom drilling at the bottom of the basic hole 402 in a way of moving upward from bottom to top. The rock and soil cut by the cutting body part 3 will fall through the soil hole into the enlarged hole section below the cutting body part 3, so that the enlarged bottom bit is only subject to the resistance of cutting the rock and soil required for the enlarged bottom drilling during the enlarged bottom drilling process, and the resistance received is greatly reduced, which can greatly improve the drilling efficiency and avoid the problems of difficult drilling and inability to drill.

[0137] In this embodiment, performing each enlarged hole operation with the enlarged bottom bit includes the following steps:

[0138] (S11) Use the drilling equipment to drive the enlarged bottom bit with the cutting body part 3 in the retracted state to extend into the bottom of the basic hole 402, make the driving mechanism 4 contact the rock and soil at the bottom of the basic hole 402, and then the drilling equipment drives the main shaft 1 of the enlarged bottom bit to rotate forward, and the driving mechanism 4 acts under the push of the rock and soil to drive the cutting body part 3 to rotate to the extended state;

[0139] (S12) While the drilling equipment keeps driving the main shaft 1 to rotate forward, lift the main shaft 1 in the direction from bottom to top to drill an enlarged bottom hole section 403 with a preset height in the basic hole 402 at one time; or first lift the main shaft 1 in the direction from bottom to top and then make the main shaft 1 move up and down repeatedly until an enlarged bottom hole section 403 with a preset height is drilled in the basic hole 402;

[0140] (S13) The drilling equipment drives the main shaft 1 of the enlarged bottom bit to rotate reversely, and the driving mechanism 4 acts under the push of the rock and soil to drive the cutting body part 3 to rotate to the retracted state, and lift the enlarged bottom bit out of the basic hole 402.

[0141] In this embodiment, in step (S13), when the cutting member 3 is rotated to the retracted state, first, the drilling equipment is used to drive the main shaft 1 of the under-reaming bit downward so that the driving mechanism 4 exerts pressure on the rock and soil below the under-reamed hole section 403, and then the main shaft 1 of the under-reaming bit is rotated in the reverse direction. This can ensure that the driving member is in full contact with the rock and soil, generating a large enough driving force to drive the cutting member 3 to rotate to the retracted state.

[0142] In this embodiment, the drilling bit 301 can adopt existing conventional short auger bits, pick-up barrel drills, etc.

[0143] Embodiment 5:

[0144] The pile driving construction method of the prestressed pipe pile in this embodiment includes the following steps:

[0145] (S21) The prestressed pipe pile is driven into the foundation 401 to a first depth by using the drilling bit 301 to drill holes and driving the pile simultaneously, and this first depth is less than the designed pile driving depth;

[0146] (S22) Stop driving the prestressed pipe pile, and use the drilling bit 301 to continue drilling to form a pilot hole section until it is not less than the designed pile driving depth;

[0147] (S23) Use the under-reaming drilling construction method of Embodiment 4 to drill an under-reamed hole section 403 with a preset height at the bottom of the pilot hole section, where the pilot hole section serves as the basic hole 402;

[0148] (S24) Drive the prestressed pipe pile to the designed pile driving depth.

[0149] In this embodiment, after step (S23) and before step (S24), first fill the under-reamed hole section 403 with concrete, and then drive the prestressed pipe pile to the designed pile driving depth.

[0150] In addition to the advantages of using the drilling bit 301 and the under-reaming bit to cooperate in the pile driving construction of the prestressed pipe pile, the pile driving construction method of this prestressed pipe pile has high construction efficiency and low construction difficulty due to the adoption of the under-reaming bit of the present invention.

[0151] Embodiment 6:

[0152] The cast-in-place pile construction method of this embodiment includes the following steps:

[0153] (S31) Construct a cast-in-place pile hole in the foundation 401. The cast-in-place pile hole is composed of multiple sub-hole sections connected in sequence along the depth direction. The sub-hole section includes a basic hole section 405 and an enlarged hole section 406 located at the bottom of the basic hole section 405, and the aperture of the enlarged hole section 406 is larger than that of the basic hole section 405;

[0154] The construction is carried out in sequence from top to bottom to obtain each sub-hole section until the bored pile hole is obtained. Each sub-hole section is obtained by using the under-reamed drilling construction method of Embodiment 4. Among them, the basic hole section 405 serves as the basic hole 402, and the under-reamed section 406 serves as the under-reamed hole section 403. See Figure 21 ;

[0155] (S32) Clean the soil residue at the bottom of the bored pile hole. See Figure 22 ;

[0156] (S33) Place the steel reinforcement cage in the bored pile hole and pour concrete to form a pile. See Figure 23 and Figure 24 .

[0157] In this bored pile construction method, since the bored pile hole is composed of multiple sub-hole sections connected in sequence along the depth direction, and the sub-hole section includes the basic hole section 405 and the under-reamed section 406 located at the bottom of the basic hole section 405, a convex ring structure is formed at the position of each under-reamed section 406 after the pile is formed, which can greatly improve the anti-pulling performance and bearing performance of the pile. Under the condition of bearing the same load, the number of piles can be reduced and the cost can be lowered. Moreover, since the under-reamed hole section 403 is constructed by using the under-reaming bit of the present invention, the rock and soil cut by the cutting body 3 will fall through the soil hole into the hole section that has been under-reamed below the cutting body 3, so that the under-reaming bit only receives the resistance of cutting the rock and soil required for under-reaming during the under-reaming drilling process, and the resistance received is greatly reduced, which can greatly improve the construction efficiency and avoid the problems of difficult drilling and impossible drilling.

[0158] The above is only the preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. For those skilled in the art of this technology, the improvements and transformations obtained without departing from the technical concept of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. An under-reaming bit, characterized in that: it includes a main shaft (1) and a base (2) provided at the lower end of the main shaft (1) and extending outward in the radial direction of the main shaft (1). One or more cutting members (3) capable of being converted between a retracted state and an extended state by rotation are installed on the base (2). When in the retracted state, the cutting member (3) swings radially inward relative to the axis of the main shaft (1) to retract, and when in the extended state, the cutting member (3) swings radially outward relative to the axis of the main shaft (1) to open. A driving mechanism (4) is installed on the main shaft (1), which is driven by the soil and rock to drive the cutting member (3) to rotate to the extended state when the main shaft (1) rotates forward, and is driven by the soil and rock to drive the cutting member (3) to rotate to the retracted state when the main shaft (1) rotates reversely; a positioning mechanism is provided between the base (2) and the cutting member (3) to position the cutting member (3) at at least one angle when the cutting member (3) swings outward to open. The positioning mechanism includes a first positioning member (35) and a second positioning member (36) provided on the cutting member (3). The first positioning member (35) contacts the base (2) when the cutting member (3) swings outward to the first angle to prevent the cutting member (3) from continuing to rotate from the retracted state to the extended state. The second positioning member (36) is installed on the cutting member (3) in a manner that can be adjusted and converted between a blocking angle and a releasing angle. The second positioning member (36) contacts the base (2) at the blocking angle to block the cutting member (3) that swings outward to open at the second angle, and the second angle is smaller than the first angle. The second positioning member (36) allows the cutting member (3) to swing to the first angle at the releasing angle. A second helix (13) for lifting the soil and rock is provided on the main shaft (1) when the main shaft (1) rotates reversely.

2. The under-reaming bit according to claim 1, characterized in that: the driving mechanism (4) includes a driving member and a rotating rod (41) rotatably installed on the main shaft (1). The driving member is installed on the rotating rod (41) and is located below the base (2), and the driving member can be driven by the soil and rock to drive the rotating rod (41) to rotate relative to the main shaft (1) when the main shaft (1) rotates forward and reversely. Each cutting member (3) is connected to the rotating rod (41) through a linkage mechanism and is driven by the rotating rod (41) to rotate to be converted between the retracted state and the extended state.

3. The under-reaming bit according to claim 2, characterized in that: the driving member includes a first helix (42) installed on the rotating rod (41), and the first helix (42) lifts the soil and rock upward when rotating in the forward rotation direction of the main shaft (1).

4. The under-reaming bit according to claim 3, characterized in that: one end of the rotating rod (41) away from the base (2) is provided with an insertion member for inserting into the soil and rock.

5. The under-reaming bit according to claim 4, characterized in that: the insertion member is a first pick (43).

6. The under-reaming bit according to claim 3, characterized in that: One end of the first helix (42) far from the base (2) is provided with a second pick (44).

7. The under-reaming bit according to claim 6, characterized in that: the second pick (44) is arranged to extend along the winding direction of the first helix (42).

8. The under-reaming bit according to claim 2, characterized in that: the driving member includes a soil collecting bucket (45) installed on the rotating rod (41), the soil collecting bucket (45) has a soil receiving cavity (451) with an upward opening, and the bottom surface of the soil collecting bucket (45) is provided with a pushing member for contacting the rock and soil to be pushed by the rock and soil to drive the soil collecting bucket (45) to rotate.

9. The under-reaming bit according to claim 8, characterized in that: the soil collecting bucket (45) is provided with a soil discharge port (452) for discharging the rock and soil in the soil receiving cavity (451) and a door plate (453) movably installed for opening and closing the soil discharge port (452).

10. The under-reaming bit according to claim 9, characterized in that: the soil discharge port (452) is arranged on the bottom surface of the soil collecting bucket (45), the door plate (453) is rotatably installed on the bottom surface of the soil collecting bucket (45) and can open and close the soil discharge port (452) by rotation, and the bottom surface of the soil collecting bucket (45) is further provided with a convex member (454) for blocking the door plate (453) to keep the door plate (453) closed to the soil discharge port (452), and the door plate (453) and the convex member (454) serve as the pushing member.

11. The under-reaming bit according to claim 10, characterized in that: the convex member (454) is a rib extending in the radial direction of the soil collecting bucket (45).

12. The under-reaming bit according to claim 2, characterized in that: the driving member is detachably connected to the rotating rod (41) by a detachable connection mechanism.

13. The under-reaming bit according to claim 12, characterized in that: the detachable connection mechanism includes a plugging hole (411) provided at the lower end of the rotating rod (41), a plug connector provided on the driving member and inserted into the plugging hole (411), and a detachable connection assembly for fixing the plug connector and the rotating rod (41).

14. The under-reaming bit according to claim 13, characterized in that: the plugging hole (411) is a non-circular hole, and the plug connector is a non-cylindrical connector that is plugged and matched with the non-circular hole and relatively stops rotation.

15. The under-reaming bit according to claim 14, characterized in that: the detachable connection assembly includes a plugging positioning member, a first positioning hole provided on the rotating rod (41), and a second positioning hole provided on the plug connector, and the plugging positioning member is detachably inserted into the first positioning hole and the second positioning hole.

16. The under-reaming bit according to claim 2, characterized in that: the main shaft (1) is provided with an axially penetrating through hole (11), the rotating rod (41) is rotatably installed in the through hole (11), the rotating rod (41) is provided with a positioning portion (412) abutting against the lower end of the main shaft (1), and the rotating rod (41) is threadedly connected with a positioning nut abutting against the upper end of the main shaft (1).

17. The under-reaming bit according to claim 16, characterized in that: a connecting head (12) for connecting a drill pipe of a drilling device is connected to the upper end of the main shaft (1), the connecting head (12) has a counterbore-type inner cavity (121) for inserting and installing the drill pipe, and the positioning nut is located in the counterbore-type inner cavity (121).

18. The under-reaming bit according to claim 17, characterized in that: the connecting head (12) is provided with an observation and maintenance hole (122) for observing the area where the positioning nut is located and for inserting a tool to tighten or loosen the positioning nut.

19. The under-reaming bit according to claim 17, characterized in that: the connecting head (12) is provided with a pin hole (123) for inserting a locking member to connect and fasten the connecting head (12) and the drill pipe.

20. The under-reaming bit according to claim 2, characterized in that: the linkage mechanism includes a connecting rod (46) and a swing arm (47) connected to the rotating rod (41), one end of the connecting rod (46) is hinged to the swing arm (47), and the other end of the connecting rod (46) is hinged to the cutting body member (3).

21. The under-reaming bit according to claim 20, characterized in that: the connecting rod (46) and the swing arm (47) are located on a side of the base (2) opposite to the main shaft (1).

22. The under-reaming bit according to claim 1, characterized in that: the radial dimension of the second helix (13) gradually decreases in the direction from bottom to top.

23. The under-reaming bit according to claim 1, characterized in that: the radial dimension of the upper part of the second helix (13) is smaller than the radial dimension of the lower part of the second helix (13).

24. The under-reaming bit according to claim 1, characterized in that: the cutting body member (3) is provided with a soil gathering portion (31) for gathering soil and rock towards the axis direction of the main shaft (1) when switching from the extended state to the retracted state.

25. The under-reaming bit according to claim 24, characterized in that: the soil gathering portion (31) includes two side plates respectively arranged on two sides of the cutting body member (3), and each side plate is provided with a third pick (32) for cutting soil and rock when the cutting body member (3) is in the extended state.

26. The under-reaming bit according to claim 1, characterized in that: the cutting body member (3) is provided with a forced retraction driving inclined surface (33) for contacting with soil and rock when the under-reaming bit is lifted upward to force the cutting body member (3) to rotate towards the retracted state.

27. The under-reaming bit according to claim 1, characterized in that: the cutting body member (3) is provided with a forming surface (34) for forming a conical surface at the bottom of the hole when the cutting body member (3) is in the extended state.

28. The under-reaming bit according to claim 1, characterized in that: The cutting body member (3) is provided with mounting holes. The second positioning member (36) is connected with an adjusting shaft (361). The adjusting shaft (361) is mounted on the cutting body member (3) in a manner that it can rotate and move along the center line of the mounting hole. A rotation-preventing protrusion (362) is provided on the adjusting shaft (361). A rotation-preventing member (37) is further provided on the cutting body member (3). The rotation-preventing member (37) is provided with a first rotation-preventing groove (371) for the rotation-preventing protrusion (362) to insert when the second positioning member (36) is at a blocking angle to prevent the adjusting shaft (361) from rotating, and a second rotation-preventing groove (372) for the rotation-preventing protrusion (362) to insert when the second positioning member (36) is at a releasing angle to prevent the adjusting shaft (361) from rotating.

29. The under-reaming bit according to claim 28, characterized in that: The cutting body member (3) is further provided with a locking member (38) for the second positioning member (36) to snap into when the second positioning member (36) is at a blocking angle to prevent the adjusting shaft (361) from rotating.

30. The under-reaming bit according to claim 1, characterized in that: The positioning mechanism includes a third positioning member provided on the cutting body member (3). The third positioning member contacts the base (2) when the cutting body member (3) swings outwards and opens to a third angle to prevent the cutting body member (3) from continuing to rotate from the retracted state to the extended state.

31. The under-reaming bit according to any one of claims 1 to 30, characterized in that: The base (2) is provided with an earth-passing channel (21) for the soil and rock to pass through and fall below the base (2).

32. The under-reaming bit according to claim 31, characterized in that: The cutting body member (3) blocks the earth-passing channel (21) in the retracted state, and the cutting body member (3) opens the earth-passing channel (21) in the extended state.

33. The under-reaming bit according to claim 32, characterized in that: The base (2) is provided with an earth-passing channel (21) corresponding to each cutting body member (3). Each cutting body member (3) blocks the corresponding earth-passing channel (21) in the retracted state, and each cutting body member (3) opens the corresponding earth-passing channel (21) in the extended state.

34. The under-reaming bit according to claim 32, characterized in that: The earth-passing channel (21) is a through hole or a notch provided on the base (2).

35. An under-reaming drilling construction method based on the under-reaming bit according to any one of claims 1 to 34, characterized in that: The construction method of the under-reamed bored pile is as follows: after a basic hole (402) is drilled in the foundation (401) by using a drilling bit (301), the drilling bit (301) is taken out; then, the under-reaming bit is used to perform an under-reaming operation to cut the rock and soil layers of the under-reamed hole section (403) to be constructed at one time, so as to drill an under-reamed hole section (403) with a preset height at the bottom of the basic hole (402); or the rock and soil of the under-reamed hole section (403) to be constructed is divided into multiple layers of annular rock and soil layers from the inside to the outside, and the multiple layers of annular rock and soil layers are cut in sequence from the inside to the outside until an under-reamed hole section (403) with a preset height is drilled at the bottom of the basic hole (402), and each time an annular rock and soil layer is cut, an under-reaming operation is performed by using the under-reaming bit. When performing each under-reaming operation by using the under-reaming bit, the under-reaming bit moves upward from bottom to top while rotating forward, and an under-reamed hole section (403) with a preset height is drilled in the basic hole (402) at one time; or the under-reaming bit first moves upward from bottom to top while rotating forward, and then moves up and down repeatedly for multiple times until an under-reamed hole section (403) with a preset height is drilled in the basic hole (402).

36. The construction method of the under-reamed bored pile according to claim 35, characterized in that: Performing each under-reaming operation by using the under-reaming bit includes the following steps: (S11) Using a drilling device to drive the under-reaming bit with the cutting member (3) in the retracted state to extend into the bottom of the basic hole (402), so that the driving mechanism (4) contacts the rock and soil at the bottom of the basic hole (402), and then the drilling device drives the main shaft (1) of the under-reaming bit to rotate forward, and the driving mechanism (4) acts under the push of the rock and soil to drive the cutting member (3) to rotate to the extended state; (S12) While the drilling device keeps driving the main shaft (1) to rotate forward, the main shaft (1) is lifted in the direction from bottom to top, and an under-reamed hole section (403) with a preset height is drilled in the basic hole (402) at one time; or the main shaft (1) is first lifted in the direction from bottom to top, and then the main shaft (1) moves up and down repeatedly for multiple times until an under-reamed hole section (403) with a preset height is drilled in the basic hole (402); (S13) The drilling device drives the main shaft (1) of the under-reaming bit to rotate reversely, and the driving mechanism (4) acts under the push of the rock and soil to drive the cutting member (3) to rotate to the retracted state, and the under-reaming bit is lifted out of the basic hole (402).

37. The construction method of the under-reamed bored pile according to claim 36, characterized in that: In the step (S13), when the cutting member (3) is rotated to the retracted state, first use the drilling device to drive the main shaft (1) of the under-reaming bit to move downward so that the driving mechanism (4) forms a pressure on the rock and soil at the lower part of the under-reamed hole section (403), and then drive the main shaft (1) of the under-reaming bit to rotate reversely.

38. A pile driving construction method for prestressed pipe piles, characterized in that: It includes the following steps: (S21) The prestressed pipe pile is driven into the foundation (401) to a first depth by using a drilling bit (301) to drill holes and driving the pile simultaneously, and the first depth is less than the designed pile driving depth; (S22) Stop the driven prestressed pipe pile, and continue drilling with a drilling bit (301) to form a pilot hole section until it reaches not less than the designed pile driving depth; (S23) Use the under-reamed drilling construction method described in claim 37 to drill an under-reamed hole section (403) with a preset height at the bottom of the pilot hole section, wherein the pilot hole section serves as the basic hole (402); (S24) Drive the prestressed pipe pile to the designed pile driving depth.

39. The pile driving construction method of a prestressed pipe pile according to claim 38, characterized in that: After step (S23) and before step (S24), first fill the under-reamed hole section (403) with concrete, and then drive the prestressed pipe pile to the designed pile driving depth.

40. A construction method for cast-in-place piles, characterized in that: It includes the following steps: (S31) Construct a cast-in-place pile hole in the foundation (401), the cast-in-place pile hole is composed of multiple segmented hole sections connected in sequence along the depth direction, the segmented hole section includes a basic hole section (405) and an under-reamed hole section (406) located at the bottom of the basic hole section (405), and the aperture of the under-reamed hole section (406) is larger than that of the basic hole section (405); Each segmented hole section is constructed in sequence from top to bottom until the cast-in-place pile hole is obtained, and each segmented hole section is obtained by using the under-reamed drilling construction method described in claim 37, wherein the basic hole section (405) serves as the basic hole (402), and the under-reamed hole section (406) serves as the under-reamed hole section (403); (S32) Clean the soil residues at the bottom of the cast-in-place pile hole; (S33) Place a steel reinforcement cage in the cast-in-place pile hole and pour concrete to form a pile.

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