Self-anchored prestressed cast-in-place pile tendon anchoring anchor rod and anchoring method thereof in hard rock area

Abstract

The present application relates to a kind of self-anchored prestressed cast-in-place pile tendon anchoring anchor rod in hard rock area and construction method, wherein the anchoring anchor rod includes pile foundation, the pile foundation includes concrete pile and prestressed steel strand, prestressed tendon hole is arranged in the concrete pile, prestressed steel strand and grouting pipe are arranged in the prestressed tendon hole, the concrete pile includes upper concrete pile and lower concrete pile, the upper concrete pile is arranged in the lower concrete pile upper portion, the lower concrete pile is arranged in the cavity of rock, prestressed tendon is arranged in the prestressed tendon hole and is anchored by anchor device, the anchor device includes clamping piece, plunger, constraint rubber band, cloverleaf type steel strand bogie and limit spring, plunger is arranged in the upper portion of cloverleaf type steel strand bogie, clamping piece is arranged in the upper portion of plunger.The present application achieves the effect of self-anchoring, cloverleaf type steel strand bogie can make steel strand not interfere with each other and can be well diverted, avoid the disadvantages of steel strand anchoring in hole bottom.

Description

Technical Field

[0001] This invention relates to the field of pile foundation construction, and more specifically, to a self-anchored prestressed cast-in-place pile reinforcement anchor rod and its anchoring method in hard rock areas. Background Technology

[0002] For bored piles that need to penetrate deep into hard rock, drilling is difficult, inefficient, and costly due to the extreme hardness of the rock. Replacing high-strength rock with lower-strength concrete is theoretically uneconomical. However, conventional bored piles require sufficient depth of embedment in the rock to meet the pile foundation's bending and pull-out resistance requirements. Drilling for underwater pile foundations in bare rock areas with high rock strength is also extremely challenging. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a self-anchored prestressed cast-in-place pile anchor rod and its anchoring method in hard rock areas. The use of prestressed anchor rods to anchor rock piles can effectively connect the pile foundation with the hard bedrock into a whole, and the bending resistance of the pile body will be further improved after the prestress is applied.

[0004] The technical solution adopted by this invention to solve its technical problem is: constructing a self-anchored prestressed cast-in-place pile reinforcement anchor rod for hard rock areas, characterized in that it includes a pile foundation, the pile foundation including concrete piles and prestressed steel strands, the concrete piles having prestressed tendon holes, the prestressed steel strands and grouting pipes being installed in the prestressed tendon holes, the concrete piles including an upper concrete pile and a lower concrete pile, the upper concrete pile being located above the lower concrete pile, the lower concrete pile being located within a cavity in the rock, and the prestressed tendon holes containing prestressed steel strands and grouting pipes. The prestressed tendons are anchored by anchorages, which include wedges, plungers, restraining rubber bands, a bridge-type steel strand bogie, and limiting springs. A plunger is provided on the upper part of the bridge-type steel strand bogie, and a wedge is provided on the upper part of the plunger. A limiting spring is provided between the wedge and the bridge-type steel strand bogie to limit the upward movement of the wedge. A restraining rubber band is provided on the outside of the wedge to prevent the wedge from spreading out. The prestressed steel strand passes through the wedge and is wound around the bridge-type steel strand bogie. A grouting pipe is provided in the middle of the prestressed steel strand.

[0005] According to the above scheme, the plunger is a frustum structure with a larger bottom and a smaller top. The plunger is made of hard steel and is shaped like a plum blossom with the raised petals forming plum blossom holes. Prestressed steel strands and grouting holes are provided inside the plum blossom holes.

[0006] According to the above scheme, the clamping piece is made of hard steel material that is thinner at the bottom and thicker at the top.

[0007] According to the above scheme, the prestressing tendon holes are formed by pre-embedded rigid plastic pipes or steel pipes.

[0008] According to the above scheme, the grouting pipe has circumferential stiffness and axial flexibility.

[0009] This invention also provides an anchoring method for self-anchored prestressed cast-in-place pile reinforcement anchor rods in hard rock areas, comprising the following steps:

[0010] S1. Piling holes are formed in the rock using rotary drilling equipment, drilling to a depth of more than 500mm into the rock. The reinforcing cage of the drilled pile adopts structural reinforcement. Before installation, the prestressed tendon hole forming pipe is tied together with the reinforcing cage. The concrete pile is poured using underwater concrete technology. After the concrete reaches the predetermined strength, a geological drilling rig or down-the-hole drilling rig is used to drill downward from the prestressed tendon hole to make the hole depth reach the design anchor depth requirement.

[0011] S2. First, align the overpass-type steel strand bogie with the direction and position and weld it to the large section side of the plunger. Pass the prestressed steel strand from the large section side to the small section side of the plum blossom hole of the plunger, pass it around the overpass-type steel strand bogie and pass it back through the holes of the plum blossom hole of the symmetrical plunger. After all the strands are passed through, place the clamps on the outside of the plunger and constrain them into a whole with the restraining rubber band. Use the limit spring to connect the clamps to the overpass-type steel strand bogie.

[0012] S3. Insert the prestressed steel strands together with the anchor system into the bottom of the prestressed tendon holes with the anchor facing downwards. After all the prestressed steel strands in the holes are inserted, use a jack to tension the prestressed steel strands on the top surface of the concrete pile. The top surface needs to be ground flat and padded with steel plates before tensioning.

[0013] S4. After tensioning to the design tension force, use grouting equipment to inject grout into the prestressing tendon holes from bottom to top through the grouting pipe.

[0014] The prestressed cast-in-place pile anchor bolt for hard rock areas, as described in this invention, has the following beneficial effects:

[0015] The anchoring system used in this invention utilizes the wedge-shaped anchoring stability principle, which allows the plum blossom-shaped plunger and the wedge to slide and squeeze the wedge against the borehole wall. After the horizontal compression generated by tension, the friction force of the borehole wall on the wedge is much greater than the tension force, achieving the effect of self-anchoring. The overpass-type steel strand bogie can prevent the steel strands from interfering with each other and can turn well, avoiding the disadvantages of anchoring the steel strands at the bottom of the borehole. Attached Figure Description

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0017] Figure 1 This is a schematic diagram of the structure of the self-anchored prestressed cast-in-place pile reinforcement anchor rod for hard rock areas according to the present invention;

[0018] Figure 2This is a top view of the self-anchored prestressed cast-in-place pile reinforcement anchor rod for hard rock areas according to the present invention;

[0019] Figure 3 This is a side view of the combination of steel strand and anchor.

[0020] Figure 4 yes Figure 3 A horizontal sectional view in the middle;

[0021] Figure 5 This is a side view of the combination of the clip and the plunger;

[0022] Figure 6 yes Figure 5 Bottom view;

[0023] Figure 7 This is a schematic diagram of the clip's retracted state;

[0024] Figure 8 This is a diagram showing the clip in the open position;

[0025] Figure 9 This is a side view of a plum blossom-shaped plunger;

[0026] Figure 10 This is a bottom view of a plum blossom-shaped plunger;

[0027] Figure 11 This is a side view of the combination of an overpass steel strand bogie and a plunger.

[0028] Figure 12 This is a top view of the combination of an overpass steel strand bogie and a plunger.

[0029] Figure 13 This is a side view of an overpass-type steel strand bogie;

[0030] Figure 14 This is a top view of an overpass-type steel strand bogie. Detailed Implementation

[0031] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0032] like Figure 1-14As shown, the self-anchored prestressed cast-in-place pile anchor rod in the hard rock area of ​​this invention includes a pile foundation, which includes a concrete pile 1 and prestressed steel strands 4. A prestressed tendon hole 3 is provided in the concrete pile 1, and the prestressed steel strands 4 and grouting pipes 10 are provided in the prestressed tendon hole 3. The concrete pile 1 includes an upper concrete pile and a lower concrete pile. The upper concrete pile is located above the lower concrete pile, and the lower concrete pile is located within a cavity in the rock 2. Prestressed tendons anchored by anchorages are provided in the prestressed tendon hole 3. The anchorages include clamps... The structure includes a plate 5, a plunger 6, a restraining rubber band 7, a bridge-type steel strand bogie 8, and a limiting spring 9. The upper part of the bridge-type steel strand bogie 8 is equipped with a plunger 6, and the upper part of the plunger 6 is equipped with a clamping plate 5. A limiting spring 9 is set between the clamping plate 5 and the bridge-type steel strand bogie 8 to limit the upward movement of the clamping plate 5. A restraining rubber band 7 is set on the outside of the clamping plate 5 to prevent the clamping plate 5 from spreading out. The prestressed steel strand 4 passes through the clamping plate 5 and is wound around the bridge-type steel strand bogie 8. A grouting pipe 10 is set in the middle of the prestressed steel strand 4.

[0033] The concrete pile 1 is drilled using drilling equipment such as a rotary drilling rig, and the reinforcement cage of the pile body is configured according to the structural reinforcement. The plunger 6 is a truncated cone structure, wider at the bottom and narrower at the top. The plunger 6 is cast from hard steel and shaped like a plum blossom, with the raised petals forming plum blossom-shaped holes. Prestressed steel strands 4 and grouting pipes 10 are installed within these plum blossom-shaped holes. The grouting pipes 10 possess circumferential stiffness and axial flexibility. The wedge 5 is made of hard steel, thinner at the bottom and thicker at the top. The prestressed tendon holes 3 are formed using pre-embedded hard plastic pipes or steel pipes. The prestressed steel strands 4 are bound with longitudinally flexible grouting pipes 10, which possess certain circumferential stiffness and axial flexibility.

[0034] The prestressed tendons are anchored in the holes of rock 2 using a self-anchoring structure. The anchor mainly consists of wedges 5, plungers 6, restraining rubber bands 7, a bridge-type steel strand bogie 8, and limiting springs 9. The wedges 5 have a thinner bottom and thicker top structure and are made of hard steel. The plungers 6 are made of hard steel and are cast and machined. They have a truncated cone structure with a larger bottom and a smaller top. The plum blossom holes of the plungers 6 accommodate the prestressed steel strands 4 and the grouting holes 11. The restraining rubber bands 7 are placed in the grooves on the outside of the wedges 5 to prevent the wedges 5 from spreading out. The limiting springs 9 can limit the upward movement of the wedges 5, prevent the wedges 5 from leaving the range of the plungers 6, and generate an initial downward pull on the wedges 5 after the anchor is lowered into place, so that the wedges 5 generate an initial friction force with the hole wall.

[0035] For underwater pile foundations in bare rock areas with high rock strength (Rock 2), drilling is very difficult. However, the pile foundation is required to resist horizontal loads, so a certain rock anchoring depth is needed. In this case, prestressed anchor piles are used instead of drilled rock anchor piles. Conventional drilling equipment is used to drill Rock 2 to a surface with the required strength and good integrity. The cast-in-place concrete is poured normally. Before pouring the concrete, prestressed anchor holes are pre-embedded. After the concrete reaches a certain strength, a geological drilling rig or down-the-hole drilling rig is used to drill a hole from the pre-embedded anchor holes into Rock 2 to a certain depth. Then, the prestressed tendons and the anchor system are placed into the drilled hole until they reach the bottom of the hole. The anchor wedges 5 will slide down and stick to the hole wall under the tension of the spring. When the prestressed tendons are tensioned, the plum blossom-shaped plungers 6 move upward, generating a large horizontal thrust on the outer wedges 5, which further increases the pressure of the wedges 5 on the hole wall. Under the action of pressure, frictional resistance is formed, preventing the wedges 5 from moving upward, thus forming an anchoring effect.

[0036] This invention also provides an anchoring method for self-anchored prestressed cast-in-place pile reinforcement anchor rods in hard rock areas, comprising the following steps:

[0037] S1. Piling holes are formed in rock 2 using rotary drilling equipment, drilling to a depth of more than 500mm in rock 2. The reinforcing cage of the drilled pile adopts structural reinforcement. Before installation, the prestressed tendon hole 3 forming pipe is tied together with the reinforcing cage. The concrete pile 1 is poured using underwater concrete technology. After the concrete reaches the predetermined strength, a geological drilling rig or down-the-hole drilling rig is used to drill downward from the prestressed tendon hole 3 to make the hole depth reach the design anchor depth requirement.

[0038] S2. First, align the overpass-type steel strand bogie 8 with the direction and position and weld it to the large section side of the plunger 6. Pass the prestressed steel strand 4 from the large section side to the small section side of the plum blossom hole of the plunger 6, pass it around the overpass-type steel strand bogie 8 and pass it back through the symmetrical plum blossom hole of the plunger 6. After all the strands are passed through, place the clamp 5 on the outside of the plunger 6 and constrain it into a whole with the restraining rubber band 7. Use the limiting spring 9 to connect the clamp 5 to the overpass-type steel strand bogie 8.

[0039] S3. Insert the prestressed steel strand 4 and the anchor system into the bottom of the prestressed tendon hole 3 with the anchor facing down. After all the prestressed steel strands 4 in all the holes are inserted, use a jack to tension the prestressed steel strand 4 on the top surface of the concrete pile 1. The top surface needs to be ground flat and padded with steel plates before tensioning.

[0040] S4. After tensioning to the design tension force, use grouting equipment to inject grout into the prestressed tendon hole 3 from bottom to top through grouting pipe 10.

[0041] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A self-anchored prestressed cast-in-place pile reinforcement anchor rod for hard rock areas, characterized in that, The system includes a pile foundation, comprising concrete piles and prestressed steel strands. The concrete piles contain prestressed tendon holes, within which prestressed steel strands and grouting pipes are installed. Each concrete pile consists of an upper concrete pile and a lower concrete pile, with the upper pile positioned above the lower pile and the lower pile positioned within a rock cavity. The prestressed tendons in the prestressed tendon holes are anchored by anchorages. Each anchorage includes a wedge, a plunger, a restraining rubber band, a bridge-type steel strand bogie, and a limiting spring. A plunger is positioned on the upper part of the bridge-type steel strand bogie, and a wedge is positioned above the plunger. A limiting spring is positioned between the wedge and the bridge-type steel strand bogie to restrict the upward movement of the wedge. A restraining rubber band is positioned on the outside of the wedge to prevent it from unraveling. The prestressed steel strands pass through the wedge and are wound around the bridge-type steel strand bogie. A grouting pipe is positioned in the middle of the prestressed steel strands. The plunger is a frustum structure with a larger bottom and a smaller top. The plunger is made of hard steel and is shaped like a plum blossom with plum blossom holes at the protruding petals. Prestressed steel strands and grouting holes are provided inside the plum blossom holes. The clip is made of hard steel that is thinner at the bottom and thicker at the top.

2. The self-anchored prestressed cast-in-place pile reinforcement anchor rod for hard rock areas according to claim 1, characterized in that, The prestressing tendon holes are formed using pre-embedded rigid plastic pipes or steel pipes.

3. The self-anchored prestressed cast-in-place pile reinforcement anchor rod for hard rock areas according to claim 1, characterized in that, The grouting pipe has circumferential stiffness and axial flexibility.

4. A method for anchoring self-anchored prestressed cast-in-place pile reinforcement anchors in hard rock areas according to claim 1, characterized in that, Includes the following steps: S1. Piling holes are formed in the rock using rotary drilling equipment, drilling to a depth of more than 500mm into the rock. The reinforcing cage of the drilled pile adopts structural reinforcement. Before installation, the prestressed tendon hole forming pipe is tied together with the reinforcing cage. The concrete pile is poured using underwater concrete technology. After the concrete reaches the predetermined strength, a geological drilling rig or down-the-hole drilling rig is used to drill downward from the prestressed tendon hole to make the hole depth reach the design anchor depth requirement. S2. First, align the overpass-type steel strand bogie with the direction and position and weld it to the large section side of the plunger. Pass the prestressed steel strand from the large section side to the small section side of the plum blossom hole of the plunger, pass it around the overpass-type steel strand bogie and pass it back through the holes of the plum blossom hole of the symmetrical plunger. After all the strands are passed through, place the clamps on the outside of the plunger and constrain them into a whole with the restraining rubber band. Use the limit spring to connect the clamps to the overpass-type steel strand bogie. S3. Insert the prestressed steel strands together with the anchor system into the bottom of the prestressed tendon holes with the anchor facing downwards. After all the prestressed steel strands in the holes are inserted, use a jack to tension the prestressed steel strands on the top surface of the concrete pile. The top surface needs to be ground flat and padded with steel plates before tensioning. S4. After tensioning to the design tension force, use grouting equipment to inject grout into the prestressing tendon holes from bottom to top through the grouting pipe.

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