Bottom expanding device, precast pile and precast pile construction method

Abstract

The invention discloses a bottom expanding device which comprises a connecting body, a first pile tip assembly and a second pile tip assembly, the first pile tip assembly comprises a first hinge plate and a first rib plate, the first rib plate is perpendicular to the first hinge plate, the second pile tip assembly comprises a second hinge plate and a second rib plate, and the second hinge plate is perpendicular to the second rib plate. The second rib plate is perpendicular to the second hinge plate; the first hinge plate and the second hinge plate are both hinged to the bottom of the connecting body, and the hinge axis of the first hinge plate and the connecting body is parallel to the hinge axis of the second hinge plate and the connecting body. The first rib plate is parallel to the second rib plate, the first rib plate is provided with a first hole, and the second rib plate is provided with a second hole corresponding to the first hole of the first rib plate. The invention further relates to a precast pile and a construction method thereof. The pile end resistance can be improved, the pile length or the number of piles can be reduced, and a large amount of construction cost and construction period are saved.

Description

Technical Field

[0001] The present invention relates to an under-reaming device, a precast pile and a construction method for a precast pile, and belongs to the technical field of precast piles. Background Art

[0002] Precast piles (represented by prestressed concrete pipe piles and hollow square piles) have obvious advantages over traditional cast-in-place piles in terms of pile integrity, construction period and economy, and are widely promoted and applied in the engineering industry. When the overburden layer on the bedrock is thin, due to the short pile length, the bearing capacity of a single pile is small and the economy is poor. Even in the case of large loads (such as high-rise buildings), it is difficult to arrange piles, resulting in the infeasibility of this pile type. Under the geological conditions of thick overburden soil layers, due to the very large thickness of the soft soil layer, it is difficult to reach the pile stopping condition (the hammer-driven pile stopping penetration or the final pile pressing force of the jacked pile required by the design) during pile driving, resulting in an excessively long pile length and high costs.

[0003] Since the cross-sectional dimensions of the mainstream pile types of precast piles are small, the bottom area of the pile tip is equal to the cross-sectional area of the pile body, and the end resistance of the pile tip is small, resulting in a small bearing capacity of a single pile. In the hilly areas in the interior of China, the strata undulate greatly, and most of the building foundations are in the geological situation of thin overburden soil layers. It is difficult to give full play to the advantage of the large bearing capacity of the precast pile body. At the same time, there are also many geological situations of thick overburden soil layers, resulting in an excessively long pile length and high costs. The main reason is that the end resistance area of the commonly used pile tips (flat-bottom cross-shaped pile tips) of existing precast piles is very small, and the contribution of the end resistance of the pile tip to the bearing capacity of the pile foundation is small. Summary of the Invention

[0004] In order to overcome the problem of small end resistance of precast piles in the prior art, the present invention provides an under-reaming device, and the specific technical solution is as follows.

[0005] An under-reaming device, characterized in that: it includes a connecting body, a first pile tip assembly and a second pile tip assembly. The first pile tip assembly includes a first hinged plate and a first rib plate, and the first rib plate is perpendicular to the first hinged plate. The second pile tip assembly includes a second hinged plate and a second rib plate, and the second rib plate is perpendicular to the second hinged plate;

[0006] Both the first hinged plate and the second hinged plate are hinged to the bottom of the connecting body, and the hinge axis of the first hinged plate and the connecting body is parallel to the hinge axis of the second hinged plate and the connecting body;

[0007] The first rib plate is parallel to the second rib plate. A first hole is provided on the first rib plate, and a second hole corresponding to the first hole on the first rib plate is provided on the second rib plate.

[0008] Furthermore, a third rib plate and a fourth rib plate parallel to the first rib plate are further arranged on the outer surface of the connecting body; when the first pile tip assembly and the second pile tip assembly are in the first state, at least part of the first rib plate and at least part of the second rib plate overlap each other, and the first hole and the second hole are aligned; when the first pile tip assembly and the second pile tip assembly are in the second state, the first hinge plate abuts against the lower edge of the third rib plate, and the second hinge plate abuts against the lower edge of the fourth rib plate.

[0009] With the above technical solution, the first rib plate and the second rib plate are correspondingly provided with a first hole and a second hole, and the locking mechanism can be installed by using the first hole and the second hole. When the first pile tip assembly and the second pile tip assembly are in the first state, the locking mechanism locks the relative positions between the first pile tip assembly and the second pile tip assembly, and the first pile tip assembly and the second pile tip assembly cannot rotate relative to the connecting body; when the locking mechanism is unlocked, the first pile tip assembly and the second pile tip assembly can rotate relative to the connecting body and rotate from the first state to the second state; when the first pile tip assembly and the second pile tip assembly are in the second state, the bearing area at the bottom of the precast pile is enlarged, and the end bearing resistance is significantly increased. Among them, the first rib plate and the second rib plate play a role in enhancing the structural strength of the first hinge plate and the second hinge plate on the one hand, and provide an installation position for the locking mechanism on the other hand, achieving the purpose of reliably locking the relative positions of the first pile tip assembly and the second pile tip assembly. Furthermore, when in the first state, the upper ends of the first rib plate and the second rib plate are tightly abutted against the bottom of the connecting body and are held together by the locking mechanism, which is beneficial to preventing the overall left-right rotation and skew of the pile tip assembly in the first stage of the pile driving process, so as not to cause the skew of the precast pile body during the pile driving process. In addition, the third rib plate and the fourth rib plate provide a reliable supporting effect for the first pile tip assembly and the second pile tip assembly, avoiding the first pile tip assembly and the second pile tip assembly in the second state from becoming an unstable cantilever structure relative to the connecting body.

[0010] Furthermore, grooves are provided on both side surfaces at the lower ends of the third rib plate and the fourth rib plate. A claw is provided on the side of the first hinge plate facing away from the first rib plate, and a claw is also provided on the side of the second hinge plate facing away from the second rib plate. The claws are arranged corresponding to the grooves. When the first pile tip assembly and the second pile tip assembly are in the second state, the claws can be inserted into the grooves, thereby fixing the first pile tip assembly to the third rib plate and fixing the second pile tip assembly to the fourth rib plate, improving the uplift bearing capacity of the precast pile. By providing the third rib plate and the fourth rib plate, not only the compressive bearing capacity of the precast pile is improved, but also the uplift bearing capacity of the precast pile is improved. Preferably, the groove is a tooth-shaped groove extending in the vertical direction, and the claw is a tooth-shaped claw. The advantage of setting the tooth-shaped groove is that even if affected by muck, etc., not all the teeth of the tooth-shaped claw can be inserted into the tooth-shaped groove, at least some teeth can be inserted into the corresponding tooth-shaped groove, improving the reliability and fault tolerance of the whole device.

[0011] Furthermore, the connecting body is in a cylindrical structure or a cuboid structure. The lower end of the connecting body is a bottom plate, and the first hinge plate and the second hinge plate are both hinged to the bottom plate. The connecting body can be a solid structure or a hollow structure. When the connecting body is a hollow structure, a number of reinforcing rib plates are provided inside the hollow structure.

[0012] Furthermore, a locking mechanism is further included. The locking mechanism has a rope passing through the first hole and the second hole; or the locking mechanism has a control rope and a bolt inserted into the first hole and the second hole. When the bolt or the rope straddles the first hole and the second hole at the same time, the relative position between the first pile tip assembly and the second pile tip assembly is locked. When unlocking is required, only by withdrawing the bolt or the rope from the first hole and / or the second hole can the relative position between the first pile tip assembly and the second pile tip assembly be unlocked.

[0013] Furthermore, the locking mechanism includes a bolt, a fluid chamber and a control rope. The bolt is inserted into the first hole and the second hole. The first hole and / or the bolt has a wedge-shaped surface for applying a thrust to withdraw the bolt from the first hole. The fluid chamber is provided on the second rib plate. One end of the bolt is located in the fluid chamber. The bolt is in sealing cooperation with the second hole. The fluid chamber has a pressure relief valve, and the pressure relief valve is connected to the control rope.

[0014] Further, the locking mechanism includes a bolt, a stop block and a control rope. The stop block is fixed to the second rib plate. The bolt is inserted into the first hole and the second hole, and both ends of the bolt abut against the stop block and the first hole respectively. The first hole and / or the bolt has a wedge-shaped surface. One end of the bolt abutting against the stop block has an avoidance notch. When the bolt rotates by a certain angle under the action of the control rope, the avoidance notch corresponds to the stop block. At this time, under the rotation drive of the first pile tip assembly and the second pile tip assembly, the wedge-shaped surface is used to apply a thrust to the bolt to withdraw it from the first hole.

[0015] Based on the same inventive concept, the present invention also relates to a precast pile, which is characterized in that it includes a precast pile body and the above-mentioned bottom-expanded device, and the connecting body of the bottom-expanded device is fixed to the lower end of the precast pile body.

[0016] Further, the bottom-expanded device further includes a locking mechanism. The locking mechanism has a rope passing through the first hole and the second hole; or the locking mechanism has a control rope and a bolt inserted into the first hole and the second hole. Wherein, the rope or the control rope extends to the top end of the precast pile body.

[0017] Based on the same inventive concept, the present invention also relates to a construction method of the above-mentioned precast pile, which is characterized by including the following steps:

[0018] 1), After the precast pile is pressed into the foundation soil layer to a certain depth, use the rope or the control rope to unlock the mutual positional relationship between the first pile tip assembly and the second pile tip assembly;

[0019] 2), Continue to press the precast pile down by a certain depth.

[0020] Compared with the prior art, in the process of driving the precast pile, the mutual positional relationship between the first pile tip assembly and the second pile tip assembly is in a locked state. The first pile tip assembly and the second pile tip assembly are roughly in a plumb state (vertical state), and the end resistance area is very small, hardly increasing the driving resistance and construction difficulty. After the mutual positional relationship between the first pile tip assembly and the second pile tip assembly is in an unlocked state, as the pile driving (pressing down the precast pile or hammering the precast pile) progresses, the first pile tip assembly and the second pile tip assembly will automatically rotate outward and open, so that the end resistance area of the pile bottom is much larger than the pile body area, and the pile tip resistance is greatly improved, effectively improving the single-pile bearing capacity, saving the pile length or the number of piles, and saving a large amount of construction costs and construction period. Moreover, when the first pile tip assembly is clamped and fixed to the third rib plate and the second pile tip assembly is clamped and fixed to the fourth rib plate, a bottom-expanded anti-pulling structure can be formed, so the anti-pulling bearing capacity of the precast pile is also greatly improved. The excellent anti-pulling bearing capacity makes the precast pile more economical than the anti-floating anchor rod, and can simplify the construction and save the construction period.

[0021] In the geological situation where the overlying soil layer is relatively thin, the advantage of the large bearing capacity of the pipe pile body can be fully exerted, making the pipe pile plan feasible; in the geological situation of a deep overlying soil layer, the pile length can also be effectively controlled, the pile length matching can be optimized, and the loss can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a construction schematic diagram of the precast pile of the present invention;

[0023] Figure 2 is a schematic diagram of the precast pile of the present invention (the first pile tip assembly and the second pile tip assembly are in the first state);

[0024] Figure 3 is an exploded schematic diagram of the precast pile of the present invention;

[0025] Figure 4 is a schematic diagram of the precast pile of the present invention (the first pile tip assembly and the second pile tip assembly are in the second state);

[0026] Figure 5 is a bottom view of the precast pile of the present invention (the first pile tip assembly and the second pile tip assembly are in the second state);

[0027] Figure 6 is a top view of the under-reaming device of the present invention (the first pile tip assembly and the second pile tip assembly are in the first state);

[0028] Figure 7 is Figure 2 an enlarged view of area A in

[0029] Figure 8 is a schematic diagram of the third rib plate and the groove;

[0030] Figure 9 is a schematic diagram of the first hinge plate and the claw;

[0031] Figure 10 is a schematic diagram of the engagement of the third rib plate and the first hinge plate;

[0032] Figure 11 is a schematic diagram of the second embodiment of the locking mechanism (locking state);

[0033] Figure 12 is a schematic diagram of the second embodiment of the locking mechanism (unlocking state);

[0034] Figure 13 is a schematic diagram of the third embodiment of the locking mechanism (locking state).

[0035] In the figure: precast pile body 1, channel 1.1, under-reaming device 2, connecting body 2.1, bottom plate 2.1.1, stiffening rib plate 2.1.2, outer cylinder 2.1.3, first pile tip assembly 2.2, first hinge plate 2.2.1, first rib plate 2.2.2, second pile tip assembly 2.3, second hinge plate 2.3.1, second rib plate 2.3.2, first hole 2.4, second hole 2.5, locking mechanism 2.6, rope 2.6.1, pin 2.6.2, fluid chamber 2.6.3, wedge surface 2.6.4, pressure relief valve 2.6.5, stop block 2.6.6, notch 2.6.7, guiding plate 2.7, positioning member 2.8, third rib plate 3, fourth rib plate 4, groove 5, toothed groove 5.1, claw 6, toothed claw 6.1, foundation soil layer 7, pile driving machine 8. Detailed implementation mode

[0036] The present invention will be further described in detail below with reference to the accompanying drawings.

[0037] See Figures 1-13 , a precast pile, which includes a precast pile body 1 and an under-reaming device 2. Among them, the precast pile body 1 is a prior art, and the precast pile body 1 is a concrete pipe pile or a hollow (or solid) square pile. The cross-section of the precast pile body 1 is circular, square, rectangular, etc.; the under-reaming device 2 is fixed to the lower end of the precast pile body 1.

[0038] As Figures 2-7 shown, the under-reaming device 2 includes a connecting body 2.1, a first pile tip assembly 2.2 and a second pile tip assembly 2.3. The first pile tip assembly 2.2 includes a first hinge plate 2.2.1 and a first rib plate 2.2.2. The first rib plate 2.2.2 is perpendicular to the first hinge plate 2.2.1. The second pile tip assembly 2.3 includes a second hinge plate 2.3.1 and a second rib plate 2.3.2. The second rib plate 2.3.2 is perpendicular to the second hinge plate 2.3.1; the first hinge plate 2.2.1 and the second hinge plate 2.3.1 are both hinged to the bottom of the connecting body 2.1, and the hinge axis of the first hinge plate 2.2.1 and the connecting body 2.1 is parallel to the hinge axis of the second hinge plate 2.3.1 and the connecting body 2.1; the first rib plate 2.2.2 is parallel to the second rib plate 2.3.2. A first hole 2.4 is provided on the first rib plate 2.2.2, and a second hole 2.5 corresponding to the first hole 2.4 of the first rib plate 2.2.2 is provided on the second rib plate 2.3.2. Among them, the corresponding setting of the first hole 2.4 and the second hole 2.5 means that when the first hinge plate 2.2.1 and the second hinge plate 2.3.1 are both in the vertical state, at least part of the first rib plate 2.2.2 and at least part of the second rib plate 2.3.2 overlap each other, and the first hole 2.4 and the second hole 2.5 are aligned. One first rib plate 2.2.2 (such as Figure 11 ) or multiple first rib plates 2.2.2 (such as Figure 5), one or more second rib plates 2.3.2 may also be provided on the second hinge plate 2.3.1. Preferably, guide plates 2.7 are provided at the ends of the first hinge plate 2.2.1 and the second hinge plate 2.3.1 away from the connection body 2.1, and the guide plates 2.7 are inclined with respect to the first hinge plate 2.2.1 and the second hinge plate 2.3.1. The guide plates 2.7 help to apply an outward turning moment to the first hinge plate 2.2.1 and the second hinge plate 2.3.1.

[0039] The connection body 2.1 is in a cylindrical structure or a cuboid structure, which is adapted to the cross-sectional shape of the precast pile body 1, that is, the cross-sectional profile of the connection body 2.1 is the same as the cross-sectional profile of the precast pile body 1; the lower end of the connection body 2.1 is a bottom plate 2.1.1, and both the first hinge plate 2.2.1 and the second hinge plate 2.3.1 are hinged to the bottom plate 2.1.1. The connection body 2.1 can be a solid structure or a hollow structure. When the connection body 2.1 is a hollow structure, the connection body 2.1 has a circular or square outer cylinder 2.1.3, and the inside of the outer cylinder is a hollow structure. A number of reinforcing rib plates 2.1.2 are provided inside the hollow structure, and the reinforcing rib plates 2.1.2 can be adjusted according to the stress conditions. Multiple transverse and longitudinal reinforcing rib plates 2.1.2 can be provided to enhance the structural strength of the connection body 2.1. The connection body 2.1 can be made of a metal material. Preferably, some of the reinforcing rib plates 2.1.2 are located above the above-mentioned hinge axis (as Figure 4 shown), so as to improve the strength of the hinge position.

[0040] In a preferred embodiment, a third rib 3 and a fourth rib 4 parallel to the first rib 2.2.2 are further provided on the outer surface of the connecting body 2.1; when the first pile tip assembly 2.2 and the second pile tip assembly 2.3 are in the first state, at least part of the first rib 2.2.2 and at least part of the second rib 2.3.2 overlap each other, and the first hole 2.4 and the second hole 2.5 are aligned; when the first pile tip assembly 2.2 and the second pile tip assembly 2.3 are in the second state, the first hinge plate 2.2.1 abuts against the lower edge of the third rib 3, and the second hinge plate 2.3.1 abuts against the lower edge of the fourth rib 4. Wherein, the first state corresponds to the state where the relative position relationship between the first pile tip assembly 2.2 and the second pile tip assembly 2.3 is locked. At this time, the first pile tip assembly 2.2 (the first hinge plate 2.2.1) and the second pile tip assembly 2.3 (the second hinge plate 2.3.1) are substantially in a vertical state, which is conducive to pressing the entire precast pile into the foundation soil layer. The first pile tip assembly 2.2 and the second pile tip assembly 2.3 in the vertical state will not significantly increase the pile pressing resistance. When the first pile tip assembly 2.2 and the second pile tip assembly 2.3 are in the second state, the first hinge plate 2.2.1 and the second hinge plate 2.3.1 are substantially in a horizontal state. At this time, projected along the vertical direction, the projected ranges of the first hinge plate 2.2.1 and the second hinge plate 2.3.1 significantly exceed the projected range of the precast pile body 1 (and the connecting body 2.1), thereby expanding the pile tip resistance area and enhancing the bearing capacity of the precast pile. Wherein, the number of the third ribs 3 (the fourth ribs 4) can be one or more (such as Figure 6 shown), and can be selected according to the specific stress conditions. Chamfers can be provided at the outer tops of the third ribs 3 (the fourth ribs 4) to reduce the weight. Wherein, at least part of the first rib 2.2.2 and at least part of the second rib 2.3.2 overlapping each other means that the first rib 2.2.2 and the second rib 2.3.2 are parallel and close to each other, but there is still a certain gap between the two to avoid friction and interference between the two.

[0041] In a preferred embodiment, as Figures 8-10 shown, grooves 5 are provided on both side surfaces at the lower ends of the third rib 3 and the fourth rib 4. A claw 6 (the claws 6 are provided in pairs) is provided on the side of the first hinge plate 2.2.1 facing away from the first rib 2.2.2, and a claw 6 is also provided on the side of the second hinge plate 2.3.1 facing away from the second rib 2.3.2. The claws 6 are provided corresponding to the grooves 5. When the first pile tip assembly 2.2 and the second pile tip assembly 2.3 are in the second state, the claws 6 can be inserted into the grooves 5, thereby fixing the first pile tip assembly 2.2 to the third rib 3 and fixing the second pile tip assembly 2.3 to the fourth rib 4, improving the uplift bearing capacity of the precast pile. By providing the third rib 3 and the fourth rib 4, not only the compressive bearing capacity of the precast pile is enhanced, but also the uplift bearing capacity of the precast pile is enhanced. Preferably, as Figures 8-10As shown, the groove 5 is a toothed groove 5.1 extending along the vertical direction (i.e., a groove with multiple intervals along a certain direction), and the claw 6 is a toothed claw 6.1 (i.e., a projection (claw) with multiple intervals along a certain direction). The advantage of setting the toothed groove 5 is that even if affected by muck and the like, not all the tooth claws of the toothed claw 6.1 can be inserted into the toothed groove 5.1, at least some tooth claws can be inserted into the corresponding toothed groove 5, improving the reliability and fault tolerance of the entire bottom-expanded device. Since the groove 5 is arranged on the two side surfaces of the third rib plate 3 and the fourth rib plate 4 that are roughly in the vertical plane, during the process of pressing the third rib plate 3 and the fourth rib plate 4 into the foundation soil layer, the groove 5 is not easily stuck by gravel, facilitating the insertion of the claw 6; at the same time, the claw 6 is a plate-like structure extending in the vertical plane, and during the process of pressing the first hinge plate 2.2.1 and the second hinge plate 2.3.1 into the foundation soil layer, the two claws 6 are not easily stuck by gravel, facilitating the insertion of the claw 6 into the groove 5.

[0042] In the present invention, the first rib plate 2.2.2 and the second rib plate 2.3.2, on the one hand, play a role in enhancing the structural strength of the first hinge plate 2.2.1 and the second hinge plate 2.3.1, and on the other hand, provide an installation position for the locking mechanism 2.6, achieving the purpose of reliably locking the relative positions of the first pile tip assembly 2.2 and the second pile tip assembly 2.3. In addition, the third rib plate 3 and the fourth rib plate 4 not only provide a reliable supporting effect for the first pile tip assembly 2.2 and the second pile tip assembly 2.3, but also fix the first pile tip assembly 2.2 to the third rib plate 3 and the second pile tip assembly 2.3 to the fourth rib plate 4 by using a clamping structure, improving the anti-pulling bearing capacity of the precast pile.

[0043] The bottom-expanded device 2 further includes a locking mechanism 2.6. The locking mechanism 2.6 has a rope 2.6.1 passing through the first hole 2.4 and the second hole 2.5; or the locking mechanism 2.6 has a control rope (not shown) and a pin 2.6.2 inserted into the first hole 2.4 and the second hole 2.5. When the pin 2.6.2 or the rope 2.6.1 straddles the first hole 2.4 and the second hole 2.5 at the same time, the relative positions between the first pile tip assembly 2.2 and the second pile tip assembly 2.3 are locked. When unlocking is required, only by withdrawing the pin 2.6.2 or the rope 2.6.1 from the first hole 2.4 and / or the second hole 2.5, the unlocking of the relative positions between the first pile tip assembly 2.2 and the second pile tip assembly 2.3 can be achieved. The function of the locking mechanism 2.6 is to lock and unlock the relative positional relationship between the first pile tip assembly 2.2 and the second pile tip assembly 2.3. Those skilled in the art can understand that there are various locking mechanisms in the prior art that can be applied to the embodiments of the present invention. The following introduces the specific embodiments of 4 locking mechanisms, but the locking mechanism of the present invention is not limited to the following 4 methods.

[0044] Embodiment 1 of the locking mechanism: As Figure 7 shown, the rope 2.6.1 passes through the first hole 2.4 and the second hole 2.5 simultaneously. The rope 2.6.1 is tied with a slipknot. The rope 2.6.1 can be a steel wire rope with a certain strength, etc., which can provide a locking force to lock the relative positions between the first pile tip assembly 2.2 and the second pile tip assembly 2.3. When unlocking is required, the rope 2.6.1 extending to the top of the precast pile body 1 is pulled, and the slipknot is opened, and the rope 2.6.1 can be withdrawn from the first hole 2.4 and / or the second hole 2.5 to realize the unlocking of the relative positions between the first pile tip assembly 2.2 and the second pile tip assembly 2.3. To improve the reliability, a horizontal baffle (not shown) can be welded at the positions of the first rib plate 2.2.2 and the second rib plate 2.3.2 corresponding to the lower end of the slipknot, and a small steel pipe is arranged outside the rope 2.6.1 and welded to the corresponding rib plate to prevent the foundation soil layer from damaging or unlocking the rope 2.6.1 exposed outside during the process of pressing down the precast pile, which affects the established construction step nodes. Of course, those skilled in the art can understand that without setting a slipknot, the locking and unlocking functions can also be realized by using the rope 2.6.1 when selecting an appropriate rope 2.6.1.

[0045] Embodiment 2 of the locking mechanism: As Figures 11-12 shown, the locking mechanism 2.6 includes a bolt 2.6.2, a stop block 2.6.6 and a control rope (not shown). The stop block 2.6.6 is fixed to the second rib plate 2.3.2 (the stop block 2.6.6 is preferably protected in a housing). The bolt 2.6.2 is inserted into the first hole 2.4 and the second hole 2.5, and both ends of the bolt 2.6.2 abut against the stop block 2.6.6 and the first hole 2.4 respectively; the first hole 2.4 and / or the bolt 2.6.2 has a wedge-shaped surface 2.6.4, and one end of the bolt 2.6.2 abutting against the stop block 2.6.6 has an avoidance notch 2.6.7. When the bolt 2.6.2 rotates a certain angle under the action of the control rope, the avoidance notch 2.6.7 corresponds to the stop block 2.6.6. At this time, under the rotation drive of the first pile tip assembly 2.2 and the second pile tip assembly 2.3, the wedge-shaped surface 2.6.4 is used to apply a thrust to the bolt 2.6.2 to withdraw it from the first hole 2.4 (at this time, the notch 2.6.7 can avoid the stop block 2.6.6 so that the bolt 2.6.2 can withdraw from the first hole 2.4). Figure 11The figure shows the locked state. When unlocking is required, the control rope extending to the top of the precast pile body 1 is used to rotate the bolt 2.6.2 by a certain angle. Corresponding stoppers (not shown) can be provided. After the bolt 2.6.2 rotates by a predetermined angle, the avoidance notch 2.6.7 just corresponds to the stopper 2.6.6. To prevent the first rib plate 2.2.2 and the second rib plate 2.3.2 from separating from each other or being distorted and deformed, resulting in the failure of the locking mechanism 2.6, positioning members 2.8 for positioning the edge of the second rib plate 2.3.2 are provided on the first hinge plate 2.2.1, and positioning members 2.8 for positioning the edge of the first rib plate 2.2.2 are provided on the second hinge plate 2.3.1. The edge of the first rib plate 2.2.2 is limited between the second rib plate 2.3.2 and the positioning member 2.8, and the edge of the second rib plate 2.3.2 is limited between the first rib plate 2.2.2 and the positioning member 2.8.

[0046] Third embodiment of the locking mechanism: As Figure 13 shown, the locking mechanism 2.6 includes a bolt 2.6.2, a fluid chamber 2.6.3, and a control rope (not shown). The bolt 2.6.2 is inserted into the first hole 2.4 and the second hole 2.5. The first hole 2.4 and / or the bolt 2.6.2 has a wedge-shaped surface 2.6.4, and the wedge-shaped surface 2.6.4 is used to apply a thrust force to the bolt 2.6.2 to withdraw it from the first hole 2.4; a fluid chamber 2.6.3 is provided on the second rib plate 2.3.2, and one end of the bolt 2.6.2 is located in the fluid chamber 2.6.3. The bolt 2.6.2 is in sealing fit with the second hole 2.5 (sealing assembly can be achieved by existing means such as sealing rings). The fluid chamber 2.6.3 has a pressure relief valve 2.6.5, and the pressure relief valve 2.6.5 is connected to the control rope. Figure 13 The figure shows the locked state. When unlocking is required, the pressure relief valve 2.6.5 is pulled out by using the control rope extending to the top of the precast pile body 1, and the fluid in the fluid chamber 2.6.3 is discharged. As the precast pile is continuously pressed into the foundation soil layer, the external force received by the first pile tip assembly 2.2 pushes the bolt 2.6.2 out of the first hole 2.4 through the wedge-shaped surface 2.6.4, thereby achieving the purpose of unlocking. In the locked state, the fluid in the fluid chamber 2.6.3 provides a pressure to counteract "the thrust force applied by the wedge-shaped surface 2.6.4 to the bolt 2.6.2 to withdraw it from the first hole 2.4". Among them, either the first hole 2.4 or the bolt 2.6.2 is provided with a wedge-shaped surface 2.6.4, or both are provided with wedge-shaped surfaces 2.6.4, which can provide a thrust force for the bolt 2.6.2 to withdraw from the first hole 2.4.

[0047] Fourth embodiment of the locking mechanism (not shown): Compared with the above-mentioned third and fourth embodiments, it is more concise. The locking mechanism 2.6 includes a bolt and a control rope. In the locked state, the bolt is inserted into the first hole 2.4 and the second hole 2.5. When unlocking is required, the bolt is pulled out of the first hole 2.4 and / or the second hole 2.5 by using the control rope.

[0048] The rope 2.6.1 or the control rope of the above locking mechanism preferably extends from the inside of the connecting body 2.1 and the precast pile body 1 to the top of the precast pile body 1. However, those skilled in the art can understand that the rope 2.6.1 or the control rope can also extend from the outside of the precast pile body 1 to the top of the precast pile body 1. For example, a protective casing is arranged outside the precast pile body 1, and the rope 2.6.1 or the control rope is arranged in the protective casing.

[0049] As Figure 1 shown, the construction method of the precast pile of the present invention mainly includes the following steps:

[0050] Install the bottom expanding device 2 at the lower end of the precast pile body 1. The fixed connection between the bottom expanding device 2 and the precast pile body 1 can be realized by means of welding connection or fastener connection, etc.; the rope 2.6.1 or the control rope can penetrate through the bottom plate 2.1.1 of the connecting body 2.1 and the channel 1.1 (not shown) inside the precast pile body 1. The rope 2.6.1 or the control rope extends to the top end of the precast pile body 1, and the relative position relationship between the first pile tip assembly 2.2 and the second pile tip assembly 2.3 is in a locked state;

[0051] Use a pile driving machine 8 (such as a hammering machine or a static hydraulic machine, etc.) to press down the precast pile so that both the first pile tip assembly 2.2 and the second pile tip assembly 2.3 enter the set depth of the foundation soil layer 7; use the rope 2.6.1 or the control rope to unlock the relative position relationship between the first pile tip assembly 2.2 and the second pile tip assembly 2.3; continue to press down the precast pile, and the lower soil continuously squeezes into the space between the first hinge plate 2.2.1 and the second hinge plate 2.3.1, causing a soil pressure difference, that is, the soil pressure inside the first hinge plate 2.2.1 and the second hinge plate 2.3.1 is greater than the soil pressure outside. The soil pressure difference pushes the first hinge plate 2.2.1 and the second hinge plate 2.3.1 to automatically cut the soil outward and then rotate and unfold outward; continue to press down the precast pile. Under the action of a large impact force or pile pressing force, the claws 6 of the first hinge plate 2.2.1 and the second hinge plate 2.3.1 are clamped into the grooves 5 of the third rib plate 3 and the fourth rib plate 4, and are buckled and locked to form an expanded bottom precast pile. And under the action of the impact force or the pile pressing force, the first hinge plate 2.2.1 and the second hinge plate 2.3.1 are tightly squeezed and pressed against the underlying bearing layer soil.

[0052] Those skilled in the art can understand that: the first rib plate 2.2.2 being perpendicular to the first hinge plate 2.2.1 and the second rib plate 2.3.2 being perpendicular to the second hinge plate 2.3.1 do not mean that the first rib plate 2.2.2 and the first hinge plate 2.2.1 are absolutely perpendicular, but the included angle between the two can be about 90°. The "parallel" mentioned in this patent does not mean absolute parallelism either, but the included angle between the two can be about 0°. Among them, the first pile tip assembly 2.2, the second pile tip assembly 2.3, the third rib plate 3, and the fourth rib plate 4 can all be made of steel, or can also be made of other high-strength metals or alloys.

[0053] In addition, although there is only one pair of the first pile tip assembly 2.2 and the second pile tip assembly 2.3 in the above embodiments, those skilled in the art can understand that two pairs, three pairs or more of the first pile tip assembly 2.2 and the second pile tip assembly 2.3 can be provided at the lower end of the connection body 2.1.

[0054] In the above embodiments, the first hinge plate 2.2.1 and the second hinge plate 2.3.1 are both hinged to the bottom of the connection body 2.1. The reference hinge method is to realize the hinge connection between two components through a hinge pin (similar to the hinge of a door). However, those skilled in the art can understand that: the first hinge plate 2.2.1 and the second hinge plate 2.3.1 can also be hinged to the connection body 2.1 without using a hinge pin. For example, when the first hinge plate 2.2.1 and the second hinge plate 2.3.1 are made of steel plates, notches are provided at the positions along the hinge axis. When the first hinge plate 2.2.1 and the second hinge plate 2.3.1 are subjected to torque, the first hinge plate 2.2.1 and the second hinge plate 2.3.1 can also rotate outward along the notches (hinge axis).

[0055] The embodiments of the present invention have been described above in conjunction with the accompanying drawings. Without conflict, the embodiments and features in the embodiments of the present invention can be combined with each other. The present invention is not limited to the above specific embodiments. The above specific embodiments are merely illustrative rather than restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many forms without departing from the purpose of the present invention and the scope protected by the claims. These all fall within the protection scope of the present invention.

Claims

1. An under-reaming device, characterized in that: The invention comprises a connecting body (2.1), a first pile tip assembly (2.2) and a second pile tip assembly (2.3), wherein the first pile tip assembly (2.2) comprises a first hinged plate (2.2.1) and a first rib plate (2.2.2), wherein the first rib plate (2.2.2) is perpendicular to the first hinged plate (2.2.1), and the second pile tip assembly (2.3) comprises a second hinged plate (2.3.1) and a second rib plate (2.3.2), wherein the second rib plate (2.3.2) is perpendicular to the second hinged plate (2.3.1); The first hinged plate (2.2.1) and the second hinged plate (2.3.1) are both hinged to the bottom of the connecting body (2.1), and the hinge axis of the first hinged plate (2.2.1) and the connecting body (2.1) is parallel to the hinge axis of the second hinged plate (2.3.1) and the connecting body (2.1); The first rib (2.2.2) is parallel to the second rib (2.3.2); the first rib (2.2.2) is provided with a first hole (2.4); the second rib (2.3.2) is provided with a second hole (2.5) corresponding to the first hole (2.4) of the first rib (2.2.2).

2. The under-reaming device according to claim 1, characterized in that, The outer surface of the connecting body (2.1) is also provided with a third rib (3) and a fourth rib (4) parallel to the first rib (2.2.2); when the first pile tip assembly (2.2) and the second pile tip assembly (2.3) are in a first state, at least part of the first rib (2.2.2) and at least part of the second rib (2.3.2) are overlapped with each other, and the first hole (2.4) and the second hole (2.5) are aligned; when the first pile tip assembly (2.2) and the second pile tip assembly (2.3) are in a second state, the first hinged plate (2.2.1) abuts against the lower edge of the third rib (3), and the second hinged plate (2.3.1) abuts against the lower edge of the fourth rib (4).

3. The under-reaming device according to claim 2, characterized in that, Grooves (5) are arranged on both side surfaces of the lower ends of the third rib plate (3) and the fourth rib plate (4); a claw (6) is arranged on the side of the first hinged plate (2.2.1) away from the first rib plate (2.2.2); a claw (6) is also arranged on the side of the second hinged plate (2.3.1) away from the second rib plate (2.3.2); the claw (6) is arranged corresponding to the groove (5); when the first pile tip assembly (2.2) and the second pile tip assembly (2.3) are in the second state, the claw (6) can be clamped into the groove (5).

4. The expanding bottom device according to claim 3, characterized in that, The groove (5) is a toothed groove (5.1) extending in a vertical direction, and the claw (6) is a toothed claw (6.1).

5. The under-reaming device according to claim 1, wherein It also includes a locking mechanism, which has a rope (2.6.1) that passes through the first hole (2.4) and the second hole (2.5); or the locking mechanism has a control rope and a pin that is inserted into the first hole (2.4) and the second hole (2.5).

6. The under-reaming device according to claim 5, characterized in that The locking mechanism includes a bolt (2.6.2), a fluid chamber (2.6.3), and a control rope. The bolt (2.6.2) is inserted into the first hole (2.4) and the second hole (2.5). The first hole (2.4) and / or the bolt (2.6.2) has a wedge-shaped surface (2.6.4), and the wedge-shaped surface (2.6.4) is used to apply a thrust force for the bolt (2.6.2) to withdraw from the first hole (2.4). The fluid chamber (2.6.3) is provided on the second rib plate (2.3.2). One end of the bolt (2.6.2) is located in the fluid chamber (2.6.3). The bolt (2.6.2) is in sealing fit with the second hole (2.5). The fluid chamber (2.6.3) has a pressure relief valve (2.6.5), and the pressure relief valve (2.6.5) is connected to the control rope.

7. The under-reaming device according to claim 5, characterized in that, The locking mechanism includes a bolt (2.6.2), a stop block (2.6.6), and a control rope. The stop block (2.6.6) is fixed to the second rib plate (2.3.2). The bolt (2.6.2) is inserted into the first hole (2.4) and the second hole (2.5). Both ends of the bolt (2.6.2) are respectively abutted against the stop block (2.6.6) and the first hole (2.4). The first hole (2.4) and / or the bolt (2.6.2) has a wedge-shaped surface (2.6.4). One end of the bolt (2.6.2) abutted against the stop block (2.6.6) has an avoidance notch (2.6.7). When the bolt (2.6.2) rotates a certain angle under the action of the control rope, the avoidance notch (2.6.7) corresponds to the stop block (2.6.6). At this time, under the rotation drive of the first pile tip assembly (2.2) and the second pile tip assembly (2.3), the wedge-shaped surface (2.6.4) is used to apply a thrust force for the bolt (2.6.2) to withdraw from the first hole (2.4).

8. A precast pile, characterized in that, It includes a precast pile body (1) and an under-reaming device as described in any one of claims 1-7, and the connecting body (2.1) of the under-reaming device is fixed to the lower end of the precast pile body (1).

9. A precast pile according to claim 8, characterized in that, The under-reaming device further includes a locking mechanism (2.6). The locking mechanism (2.6) has a rope (2.6.1) passing through the first hole (2.4) and the second hole (2.5); or the locking mechanism (2.6) has a control rope and a bolt (2.6.2) inserted into the first hole (2.4) and the second hole (2.5). Wherein, the rope (2.6.1) or the control rope extends to the top end of the precast pile body (1).

10. A construction method for a precast pile as described in claim 8 or 9, characterized in that, It includes the following steps: 1). After the precast pile is pressed into the foundation soil layer (7) to a certain depth, use the rope (2.6.1) or the control rope to unlock the mutual positional relationship between the first pile tip assembly (2.2) and the second pile tip assembly (2.3); 2). Continue to press the precast pile down to a certain depth.

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