Screw pile, construction method of screw pile and building foundation

Abstract

The invention discloses a screw pile, the pile top of the screw pile is provided with a reserved steel bar section, the reserved steel bar section is used for extending into a foundation to cast the screw pile and the foundation into a whole, the screw pile further comprises a blocking device arranged at one end of the pile top, the reserved steel bar section extends into the blocking device, and the blocking device separates reserved steel bars from pile top concrete. According to the screw pile, the reserved steel bar section extends into the blocking device, the blocking device separates the reserved steel bar from the pile top concrete in the concrete pouring process of the pile body, and after pile cutting, the reserved steel bar section is exposed and can be used for being connected with a steel bar of a foundation, and the pile top and the foundation are poured into a whole.

Description

Technical Field

[0001] The invention relates to the technical field of building foundation construction, in particular to the technical field of screw pile molding and construction. Background Art

[0002] The Chinese invention patent with the publication number CN117266147A discloses a construction method for improving the quality of cast-in-place screw piles in pebble strata. The method uses a screw pile driver to drill holes. After the drilling is completed, the holes are lifted and grouting is performed while the steel cage is pressed in. The steel screw pile is constructed by first pouring and then lowering the steel cage. The casting method adopted by the method avoids the problem of surrounding backfill soil body disturbing the hole and shrinking the diameter after the hole is formed. Another Chinese invention patent with the publication number CN116988460A discloses another type of squeezed branch plate screw pile and its construction method and pile forming device used in the construction. The pile end of the pile foundation goes deep into the bearing layer, and the casting method of first pouring and then lowering the steel cage is also adopted. This method is different from the common screw pile construction method. The existing concrete screw pile uses a spiral pile driver to drill holes. The threaded drill rod squeezes the circumferential soil body. The drill rod is lifted while pumping concrete to form a concrete pile body, which is combined with the soil layer to form a composite foundation. Therefore, the pile foundation formed by this construction is generally a friction pile, which is used to improve the bearing capacity of the weak foundation. The pile foundation of the above-mentioned patent goes deep into the bearing layer. It is an end-bearing friction pile, which has higher requirements on the strength of the pile body, so a steel cage skeleton is added. When the steel cage is placed first and then the concrete is poured, there are problems such as collapse and shrinkage caused by the surrounding soil moving into the hole or rubbing against it. The above problems can be effectively avoided by pouring concrete first and placing the steel cage before the concrete begins to set. The disadvantage is that this method has the same problem as the original concrete screw pile. There is a problem of loose soil falling on the top of the concrete screw pile, and the solution is to dig out the soil layer around the top of the pile after the concrete screw pile is poured, and carry out pile cutting construction to cut off the loose soil part of the pile top until it is cut to the position that meets the requirements. After adding the steel cage as the end-bearing friction pile, the pile end (or pile bottom) acts on the bearing layer, and the pile foundation hardly settles. If a cushion layer is set on top in the same way as a concrete screw pile, the cushion layer will be pierced or deformed. Therefore, the end-bearing pile (or end-bearing friction pile) generally has steel bars reserved at the top of the pile and is cast as a whole with the building foundation. Since the screw pile steel bars formed in the above manner form an integral whole with the pile foundation concrete, the steel bars at the top of the pile will be removed together when the pile is cut. Summary of the invention

[0003] In view of the above shortcomings, the object of the present invention is to provide a screw pile that can achieve the effect of removing concrete separately when the top of the screw pile is removed. The object of the present invention is also to provide a cast-in-place construction and forming method for the above-mentioned screw pile. The object of the present invention is also to provide a building foundation structure including the above-mentioned screw pile.

[0004] To this end, the present invention provides a screw pile, wherein a reserved steel bar section is provided at the top of the screw pile, the reserved steel bar section is used to extend into the foundation to cast the screw pile and the foundation into a whole, and also includes a blocking device arranged at one end of the pile top, the reserved steel bar section extends into the blocking device, and the blocking device separates the reserved steel bar from the concrete at the pile top.

[0005] Furthermore, the blocking device includes a transverse blocking plate and a longitudinal blocking plate. The longitudinal blocking plate is arranged on the outside of the steel cage. The transverse blocking plate is provided with a through hole. The reserved steel bar section passes through the transverse blocking plate from the through hole. The transverse blocking plate and the longitudinal blocking plate enclose a space separated from the concrete on the pile top.

[0006] Furthermore, the screw pile is formed by cast-in-place, and includes a straight column section and a screw section. The screw section is against the bearing layer. A guide slope is provided at the connection position of the straight column section and the screw section. The guide slope is set low on the outside and high on the inside.

[0007] Furthermore, the guide inclined surface is provided with an annular convex strip close to the outer wall of the straight column section.

[0008] The present invention also includes a construction method of the screw pile, comprising the following steps:

[0009] S1: Use the drill rod of the screw pile driver to drill into the soil layer to form a straight column hole and a screw-shaped hole, wherein the screw-shaped hole contacts the bearing layer, the screw pile driver comprises a main frame, a bracket, a driving device, a turntable and an annular plate, the lower end of the annular plate has a predetermined shape for forming an inclined surface or a formed inclined surface and an annular groove, the main frame is connected to the bracket, the annular plate is movably connected to the bracket, the drill rod is connected to the turntable and passes through the bracket and the annular plate, the drill hole cooperates with the annular plate, the turntable is driven by the driving device, and the upper end of the driving device is connected to the feeding device;

[0010] S2: The ring plate is pressed down to form a bevel or a bevel and an annular groove at the bottom of the straight cylindrical hole;

[0011] S3: lift the drill rod upwards and pump concrete through the drill rod until the concrete reaches a predetermined height;

[0012] S4: before the initial setting of the concrete, a steel cage is placed in the drilled hole, a reserved steel bar section is provided on the upper part of the steel cage, and the reserved steel bar section is fixed with the blocking device;

[0013] S5: Part of the concrete on the top of the pile and the longitudinal barrier plate are removed to form a screw pile with a reserved steel bar segment.

[0014] Furthermore, during the construction of step S3, when concrete is poured into the straight cylindrical hole, the annular plate and the drill rod are lifted upward at the same speed.

[0015] Furthermore, before step S1, it also includes determining the pile position, digging a soil layer of predetermined thickness at the pile position, and setting a T-shaped retaining device at the pile position, wherein an annular baffle extends vertically downward from the middle of the retaining device, and a middle circular hole is provided in the middle of the annular baffle, and the inner diameter of the middle circular hole matches the outer diameter of the annular plate, and the drill rod and the annular plate pass through the middle through hole.

[0016] Furthermore, the steel cage includes main bars and stirrups, and the density of the stirrups in the straight column section is greater than the density of the stirrups in the screw section.

[0017] The invention also discloses a building foundation. After the screw pile is formed by the construction method, foundation steel bars are arranged, the reserved steel bar sections are extended into the foundation steel bars, and concrete is poured to connect the foundation and the pile top into a whole.

[0018] Furthermore, the building foundation also includes short piles, which are formed by on-site drilling and by pumping concrete while lifting the drill rod upward. The screw piles are arranged at the corner points of the square, and the short piles are arranged at the center of the square.

[0019] The beneficial technical effects of the present invention are:

[0020] (1) A screw pile of the present invention has a reserved steel bar section at the pile top, the reserved steel bar section extends into a blocking device, and the blocking device separates the reserved steel bar from the concrete at the pile top during the concrete pouring process of the pile body, so that a cavity or a groove is formed inside the pile top, and the reserved steel bar section is arranged in the cavity or the groove. After the concrete pile body hardens, the soil around the pile top is excavated in the same manner as that of an ordinary screw pile, and the pile is cut by a pile cutting device. The length range of the pile top is determined based on the experience or test of ordinary screw pile cutting, and the blocking device is set within the corresponding range. After the pile is cut, the reserved steel bar section is exposed and can be used to connect with the steel bars of the foundation and cast the pile top and the foundation into a whole.

[0021] (2) Compared with ordinary screw piles, the screw piles of the present invention have higher requirements for pile body strength. When the speed of drilling rod lifting and concrete pumping is well controlled, the drilling rod in the screw hole fits with the soil, and the soil is not easy to collapse. However, in the straight column section, the thread of the drilling rod contacts the wall of the straight column hole, and the soil in the thread groove of the drilling rod is easy to fall off and fall to the interface between the straight column hole and the threaded hole under the rotation and vibration of the drilling rod. The floating soil attached to the interface will affect the quality of the pile body. In a specific embodiment of the present invention, an inclined surface is set on the interface of the two holes. The fallen soil blocks have a certain speed and can roll along the inclined surface to the V-shaped groove, thereby adhering to the V-shaped structure of the straight column section protruding to the screw section, thereby avoiding adverse effects on the quality of the pile body. Further, a metal plate with a smooth surface can be pressed into the inclined surface to prevent the fallen protrusions from adhering to the inclined surface.

[0022] (3) In a specific embodiment of the present invention, in order to reduce the length of the cut pile, that is, to reduce the amount of loose soil on the top of the drill hole falling into the concrete, a retaining device is provided at the pile position. After the pile body is cast, the retaining device can be removed to reduce the waste of building materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of a specific embodiment of a screw pile for implementing the present invention;

[0024] Figure 2 It is a schematic diagram of a drill rod of the present invention;

[0025] Figure 3 It is a partial schematic diagram of a screw pile with annular convex strips;

[0026] Figure 4 A schematic diagram of a screw pile for setting up a retaining device;

[0027] Figure 5 A schematic diagram of a building foundation of the present invention;

[0028] Figure 6 Schematic diagram of the layout of screw piles and short piles.

[0029] Explanation of the reference numerals: 1. Screw pile; 101. Straight column section; 102. Screw section; 103. Main reinforcement; 104. Hoop reinforcement; 105. Horizontal baffle plate; 106. Longitudinal baffle plate; 107. Partition space; 108. Reinforcement bar; 109. Guide slope; 110. Annular convex strip; 111. Reserved steel bar section; 2. Auger drilling rig; 201. Drive device; 202. Turntable; 203. Bracket; 204. Hydraulic device; 205. Annular plate; 206. Inclined surface; 207. Main frame; 208. Drill rod; 3. Foundation; 4. Short pile; 5. Bearing layer; 6. Retaining device; 601. Annular baffle plate. DETAILED DESCRIPTION

[0030] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation mode, structure, characteristics and effects of the present invention are described in detail below in combination with the accompanying drawings and preferred embodiments.

[0031] Reference Figures 1 to 6As shown, a screw pile 1 of the present invention has a reserved steel bar section 111 at the top of the pile. The reserved steel bar section 111 is used to extend into the foundation 3 to cast the screw pile 1 and the foundation 3 into a whole. It also includes a blocking device arranged at one end of the pile top. The reserved steel bar section 111 extends into the blocking device. The blocking device separates the reserved steel bar section 111 from the concrete at the top of the pile. The screw pile 1 is cast in situ. The screw pile 1 includes a straight column section 101 and a screw section 102. A spiral drill rig 2 is used to drill into the soil layer at the pile position to form a borehole. Concrete is pumped into the drill rod while rotating in the opposite direction and lifting it. After the drill rod is completely lifted, a steel cage is vertically inserted into the middle of the concrete to form a pile. The above-mentioned cast-in-situ drilling technology of the screw pile 1 is a prior art, and the technology of inserting the steel cage later has also been disclosed by other prior arts, which will not be described in detail here. The upper end of the steel cage (corresponding to the end of the pile top) is provided with a reserved steel segment 111 that cooperates with the foundation 3. After the steel cage is put in place, the reserved steel segment 111 can extend out of the pile top or not. The blocking device can be Figure 1 The steel box or steel trough shown is fixed on the main reinforcement 103 of the steel cage by ribs 108. The steel box or steel trough includes longitudinal baffles 106 around and transverse baffles 105 fixed to the lower part of the longitudinal baffles 106. The transverse baffles 105 and the longitudinal baffles 106 form a separation space 107 between the steel box and the steel trough, separating the pile top concrete from the reserved steel bar segment 111, and the steel bar passes through the through hole on the transverse baffle 105. The longitudinal baffles 106 of the steel box or steel trough can form a polygonal or irregular shaped baffle, preferably an annular baffle concentric with the pile body, which is convenient for cutting around the pile when cutting the pile. Of course, the blocking device can also use a foam filling block, insert the reserved steel bar segment 111 into it, and the foam filling block and the above-mentioned steel box and steel trough can be removed when cutting the pile. The position of the blocking device is designed according to the position of the pile top that needs to be cut. When it cannot be accurately estimated, the length of the blocking device in the longitudinal direction of the pile body can be extended. When the surface layer of the soil is disturbed, the loose soil falls into the concrete at the top of the pile, and even migrates downward. The loose soil affects the quality of the pile top and the structural strength of the pile. It is usually necessary to cut off the part of the pile top affected by the loose soil. In this embodiment, the concrete at the top of the pile is cut off by a common pile cutting device to form a screw pile 1 with the reserved steel bars exposed. The screw pile 1 of this embodiment penetrates deep into the bearing layer and is a friction end-bearing pile. The soil stress shared by the soil around the pile is relatively high, thereby reducing the end load.

[0032] Figure 2The figure shows a forming device for a screw pile 1, which includes an auger 2, which mainly includes a main frame 207, a bracket 203, a driving device 201, a turntable 202, an annular plate 205 and a drill rod 208. The bracket 203 is connected to the track of the main frame 207 and can move along the track. The main frame 207 is connected to a hydraulic device, and the verticality of the track of the main frame 207 can be adjusted. The lower part of the bracket 203 is connected to the annular plate 205 through the hydraulic device 204, and the upper part of the bracket 203 is connected to the turntable 202. The turntable 202 is connected to the drill rod 208 and drives the drill rod to rotate. The drill rod 208 passes through the bracket 203 and the annular plate 205. The inner diameter of the annular plate 205 is the same as the outer diameter of the drill rod 208 or is provided with a certain gap. The upper part of the turntable 202 can be connected to a driving motor, and the driving motor is connected to a base, and the base is connected to a feeding device. Of course, the above-mentioned spiral drilling machine also includes other existing structures such as walking devices, control systems, circuits, pipelines, etc. Other equipment also includes concrete pumping devices, as well as cranes for lifting and placing steel cages or equipment for pressing steel cages, which will not be repeated here. The bottom of the above-mentioned annular plate 205 is provided with an inclined surface 206. The hydraulic device 204 on the bracket 203 can press the annular plate 205 down to the connection interface between the straight column hole and the screw hole, and form an inclined surface on the interface. When pouring concrete, soil particles falling from the drill rod thread can fall into the V-shaped groove of the straight column hole along the inclined surface formed on the interface, reducing the floating soil on the interface and avoiding a large amount of floating soil or scum adhering to the interface between the straight column section 101 and the screw section 102 of the pile to affect the strength of the pile body. Preferably, in order to prevent the soil particles from rolling smoothly due to the large friction of the inclined surface 206 formed by the soil layer, a metal plate with a smooth surface can be set at the lower end of the annular plate 205, fixed to the bottom of the annular plate 205 by an electromagnetic suction cup or other unlockable means, and released after being pressed down into place so that the metal plate is set on the inclined surface. Figure 4 As shown, after the concrete is formed, a guide slope 109 is formed, and the guide slope 109 is set low outside and high inside. Preferably, in order to prevent a large number of fallen soil particles from filling the V-shaped groove and affecting the quality of the pile body, refer to Figure 3 As shown, the V-shaped groove is changed into a groove for storing fallen soil particles, and concrete is poured in the groove to form an annular convex strip 110. The bottom of the annular convex strip 110 is combined with loose soil or slag, thereby preventing the loose soil from affecting the pile quality at the connection between the straight column section 101 and the screw section 102.

[0033] The present invention also discloses a construction method of the screw pile 1, comprising the following steps:

[0034] S1: using the drill rod 208 of the spiral drilling machine 2 to drill into the soil layer to form a straight columnar hole and a screw-shaped hole, wherein the screw-shaped hole abuts against the bearing layer 5;

[0035] S2: The annular plate 205 is pressed down on the bottom of the straight cylindrical hole to form a bevel or a bevel and an annular groove;

[0036] S3: lifting the drill rod 208 upwards and pumping concrete through a pumping port provided in the middle of the drill rod 208 until the concrete reaches a predetermined height;

[0037] S4: before the initial setting of the concrete, a steel cage is placed in the drilled hole, a reserved steel segment 111 is provided on the upper part of the steel cage, and the reserved steel segment 111 is fixed with the blocking device;

[0038] S5: Cut off part of the concrete on the top of the pile and the longitudinal barrier plate 106 to form a screw pile 1 with a reserved steel bar segment 111.

[0039] The above construction method also includes measuring and laying out to determine the pile position. After the pile position is determined, the spiral drill 2 is in place to level and adjust the verticality of the drill rod 208. The drilling process requires strict feed speed (i.e., vertical descent speed of the drill rod) and rotation speed of the drill rod. Specifically, the drill rod 208 rotates for more than two weeks and drops one pitch to form a straight cylindrical hole. After the drill rod 208 drops to the designed depth, the drill rod rotates for one week and drops one pitch to form a threaded hole. After the drilling is completed, the drill rod 208 is reversed and lifted upward. During the lifting process, the lifting speed and rotation speed need to be strictly controlled to avoid damaging the threads in the soil layer, and concrete is pumped through the pumping port located in the middle of the drill rod.

[0040] In the above embodiment, during construction step S3, when concrete is poured into the straight cylindrical hole, the annular plate 205 and the drill rod 208 are lifted upward at the same speed to prevent the annular plate 205 from lifting prematurely and causing soil on the hole wall to fall off.

[0041] In the above embodiment, referring to Figure 1 As shown, before step S1, it also includes digging a soil layer of a predetermined thickness on the pile position, and setting a T-shaped retaining device 6 on the pile position, wherein an annular baffle 601 extends vertically downward from the middle of the retaining device 6, and a middle circular hole is provided in the middle of the annular baffle 601, and the inner diameter of the middle circular hole matches the outer diameter of the annular plate 205, and the drill rod 208 and the annular plate 205 pass through the middle through hole. As described above, the drill rod in the soil layer can prevent the top soil from falling or collapsing into the hole, and when the drill rod is fully lifted and in the subsequent process of steel bar insertion and vibration, the top soil is easy to fall into the concrete on the top of the pile, resulting in the quality of the concrete on the top of the pile being affected, which is also the reason why the pile needs to be cut. After the retaining structure 6 is set in this embodiment, the falling of floating soil can be reduced, the thickness of the pile top can be reduced, the construction materials can be saved, and the quality of the pile top can be improved.

[0042] In the above embodiment, referring to Figure 1As shown, the steel cage includes main bars 103 and stirrups 104, and the density of the stirrups 104 of the straight column section 101 is greater than the density of the stirrups 104 of the screw section 102. Since the geometric cross-section of the screw pile 1 and the distribution law of the additional stress field decrease from top to bottom, the density of the stirrups 104 of the straight column section 101 can be increased to improve the pile body strength, and the screw section can be relatively provided with fewer stirrups 104 to adapt to the change of soil stress, reducing the consumption of casting materials and labor.

[0043] Reference Figure 5 and Figure 6 As shown, the present invention also discloses a building foundation. After the screw pile 1 is formed by the above-mentioned construction method, the steel bars of the foundation 3 are arranged, the reserved steel bar section 111 extends into the steel bars of the foundation 3, and concrete is poured to connect the foundation 3 and the pile top into a whole. The foundation also includes short piles 4, which can be semi-squeezed soil forming piles without steel bars, such as ordinary screw piles, which are formed by drilling holes on site to form straight columns and threaded holes and pumping concrete while lifting the drill rod upward. The special screw pile 1 of the present invention is arranged at the corner point of the square, and the short pile 4 is set at the center of the square. The screw pile 1 as a friction end bearing pile is mainly used to bear the building load, and the short pile is mainly used to control local settlement and uneven settlement.

[0044] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A screw pile, wherein a reserved steel bar section is provided at the top of the screw pile, and the reserved steel bar section is used to extend into the foundation to cast the screw pile and the foundation into an integral whole, characterized in that: It also includes a blocking device arranged at one end of the pile top, the reserved steel bar section extends into the blocking device, and the blocking device separates the reserved steel bar from the concrete on the pile top.

2. A screw pile according to claim 1, characterized in that: The blocking device includes a transverse blocking plate and a longitudinal blocking plate. The longitudinal blocking plate is arranged on the outside of the steel cage. The transverse blocking plate is provided with a through hole. The reserved steel bar section passes through the transverse blocking plate from the through hole. The transverse blocking plate and the longitudinal blocking plate enclose a space separated from the pile top concrete.

3. The screw pile according to claim 1, characterized in that: The screw pile is formed by cast-in-place, and includes a straight column section and a screw section. The screw section is against the bearing layer. A guide slope is provided at the connection position of the straight column section and the screw section. The guide slope is set low on the outside and high on the inside.

4. A screw pile according to claim 3, characterized in that: The guide inclined surface is provided with an annular convex strip close to the outer wall of the straight column section.

5. A method for constructing a screw pile according to claim 3 or 4, characterized in that: The following steps are involved: S1: Use the drill rod of the screw pile driver to drill into the soil layer to form a straight column hole and a screw-shaped hole, wherein the screw-shaped hole contacts the bearing layer, the screw pile driver comprises a main frame, a bracket, a driving device, a turntable and an annular plate, the lower end of the annular plate has a predetermined shape for forming an inclined surface or a formed inclined surface and an annular groove, the main frame is connected to the bracket, the annular plate is movably connected to the bracket, the drill rod is connected to the turntable and passes through the bracket and the annular plate, the drill hole cooperates with the annular plate, the turntable is driven by the driving device, and the upper end of the driving device is connected to the feeding device; S2: The ring plate is pressed down to form a bevel or a bevel and an annular groove at the bottom of the straight cylindrical hole; S3: lift the drill rod upwards and pump concrete through the drill rod until the concrete reaches a predetermined height; S4: before the initial setting of the concrete, a steel cage is placed in the drilled hole, a reserved steel bar section is provided on the upper part of the steel cage, and the reserved steel bar section is fixed with the blocking device; S5: Part of the concrete on the top of the pile and the longitudinal barrier plate are removed to form a screw pile with a reserved steel bar segment.

6. The method for constructing a screw pile according to claim 5, characterized in that: During the construction of step S3, when concrete is poured into the straight cylindrical hole, the annular plate and the drill rod are lifted upward at the same speed.

7. The method for constructing a screw pile according to claim 5, characterized in that: Before step S1, the method also includes determining the pile position, digging a soil layer of a predetermined thickness at the pile position, and setting a T-shaped retaining device at the pile position, wherein an annular baffle extends vertically downward from the middle of the retaining device, and a middle circular hole is provided in the middle of the annular baffle, and the inner diameter of the middle circular hole matches the outer diameter of the annular plate, and the drill rod and the annular plate pass through the middle through hole.

8. The method for constructing a screw pile according to claim 5, characterized in that: The steel cage comprises main bars and stirrups, and the density of the stirrups of the straight column section is greater than the density of the stirrups of the screw section.

9. A building foundation, characterized in that: After the screw pile is formed using the construction method described in claim 8, foundation reinforcement is laid, the reserved reinforcement section extends into the foundation reinforcement, and concrete is poured to connect the foundation and the pile top into a whole.

10. A building foundation according to claim 9, characterized in that: It also includes short piles, which are formed by on-site drilling and by pumping concrete while lifting the drill rod upward. The screw piles are arranged at the corners of the square, and the short piles are arranged at the center of the square.

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