Foundation pit prestress jet grouting anchor cable construction method

Abstract

The invention discloses a foundation pit prestress rotary jet grouting anchor cable construction method. The method comprises the following steps that after a row pile vertical face layer is completed, drilling is conducted on rotary jet grouting piles through a drilling machine; replacing a drill bit with a nozzle, and stirring the cement slurry; starting a guide device; the anchor cable is jacked, and the drill rod rotates forwards and backwards alternately for jacking; grease is smeared on the steel strand according to the depth of the anchor cable of the free section, and a plastic sleeve is arranged; after the anchor cable is jacked to a specified depth, the drill rod begins to retreat, and the drill rod alternately rotates forwards and backwards during retreating; after the guniting depth of the fixed end of the anchor cable is reached, the free section stops guniting, and the drill rod retreats; a waist beam made of channel steel is installed, and anchor cable tensioning is completed; the problems that the anchor cable deflects and is not centered in the anchor body, secondary guniting is conducted on the free section and the like are effectively solved, the overall construction quality of the anchor cable is comprehensively improved, materials are saved, and cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of engineering construction, and in particular to a method for constructing a foundation pit prestressed rotary grouting anchor cable. Background Art

[0002] The foundation pit is an earth pit excavated according to the design requirements of the underground structure. During the excavation process, the static equilibrium state of the underground soil around the foundation pit is broken, the internal pressure of the soil is automatically unloaded, and the soil pressure type is converted from static soil pressure to active soil pressure. In order to achieve a new equilibrium state, the side walls of the foundation pit are prone to move into the pit and even collapse. Therefore, slope and support treatment of the side walls of the foundation pit become necessary construction steps.

[0003] Conventional anchor support technology mainly uses steel bars or steel strands as the rod material. After drilling, cement slurry or mortar is poured into the hole to form a stone body and prestress is applied. The friction between the stone body and the soil is relied on to provide pull-out bearing capacity. However, during the construction process, the steel strands are prone to dislocation when impacted by concrete, resulting in uneven slurry sprayed around the anchor cable, which reduces the quality of the formed anchor cable.

[0004] Therefore, it is necessary to provide a method for constructing prestressed rotary grouting anchor cables in foundation pits to ensure that the position of the steel strand in the anchor body remains unchanged, the slurry around the anchor cable is uniform, uneven slurry distribution is avoided, the quality and efficiency of the anchor cable construction are improved, and at the same time, the slurry injected into the free section of the anchor body is reduced to save costs. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a method for constructing prestressed rotary grouting anchor cables in foundation pits, thereby ensuring that the position of the steel strands in the anchor body remains unchanged, making the slurry around the anchor cable uniform, avoiding uneven distribution of the slurry, improving the quality and efficiency of the anchor cable construction, and at the same time reducing the slurry injected into the free section of the anchor body to save costs.

[0006] The foundation pit prestressed rotary grouting anchor cable construction method provided by the present invention adopts the following technical scheme:

[0007] A method for constructing a prestressed rotary grouting anchor cable in a foundation pit comprises the following steps:

[0008] S1. After the pile row facade surface layer is completed, a hole-making machine is used to drill holes at the jet grouting piles. The drilling depth is greater than the diameter of the jet grouting piles. At the same time, the steel strands and the anchor end extrusion anchors are made and locked;

[0009] S2. Replace the drill bit with a spray head, set a steel strand resistance-free guide device at a suitable position behind the rotating motor, and stir the cement slurry at the same time;

[0010] S3. Open the guide device, put the steel strand in and lock it, introduce the steel strand into the center anchor plate at the nozzle, wrap it around the spraying pipe with a positioning bracket, and fix the steel strand at the corresponding position of the positioning bracket;

[0011] S4. Push the anchor cable in. When the depth exceeds the diameter of the jet pile, start spraying. The drill rod rotates forward and backward alternately to push in. The mud overflows out of the anchor hole. When adding the drill rod, set the positioning bracket at the same time to ensure that the anchor cable is always in the middle of the anchor hole.

[0012] S5. Apply butter on the steel strand according to the depth of the free anchor cable, and install a plastic sleeve. The two ends of the sleeve are fixed firmly and tightly on the steel strand;

[0013] S6. When the anchor cable is pushed to the specified depth, the drill rod starts to retreat, and the drill rod rotates forward and backward alternately during retreat;

[0014] S7. After the shotcrete depth of the anchor cable fixed end is reached, the shotcrete of the free section is stopped and the drill rod is withdrawn;

[0015] S8. Install the waist beam made of channel steel and complete the anchor cable tensioning after the anchor body strength reaches 75% of the design value.

[0016] Furthermore, the guiding device includes a support frame and a roller arranged on the support frame, and the anchor cable moves into the anchor hole through the roller on the support frame.

[0017] Furthermore, a guide frame for mounting rollers is provided on the support frame, the guide frame is arranged in a circular shape, the rollers are evenly arranged inside the guide frame, and the anchor cable passes through the guide frame and contacts the rollers.

[0018] Furthermore, the rollers are arranged in multiple rows along the moving direction of the anchor cable.

[0019] Furthermore, the guide frame includes a fixed frame fixed on the support frame and a movable frame arranged on the fixed frame, one side of the fixed frame and the movable frame are hinged and buckled together to form a circular guide frame, and a lock for fixing the movable frame is arranged on one side of the fixed frame and the movable frame that can be opened and closed.

[0020] Furthermore, a handle is provided on one side of the movable frame that can be opened and closed.

[0021] Furthermore, the positioning bracket is arranged in a ring shape, the steel strands are evenly arranged on the circumference of the positioning bracket, and the drill rod passes through the positioning bracket.

[0022] Furthermore, a plurality of mounting portions for mounting the steel strands are evenly arranged on the circumference of the positioning bracket, and one side of the mounting portion can be opened and closed for placing the steel strands therein.

[0023] Furthermore, one side of the positioning bracket can be opened and closed to allow the drill rod to pass through.

[0024] In summary, the present invention includes at least one of the following beneficial effects: the detachable positioning bracket effectively distributes the steel strands evenly around the drill rod shotcrete pipe, the steel strands are firmly fixed and not loose, the drill rod shotcrete pipe pushes the anchor cable forward while the steel strands are guided by a resistance-free device, it is convenient to set the positioning bracket when adding a drill rod shotcrete pipe, and the steel strands will not be scattered; when the drill rod shotcrete pipe retreats to the free section, the spraying is stopped, and the slurry sprayed by the free section pushes forward to form a protective wall on the anchor hole wall, effectively solving the problems of the anchor cable being deflected and not centered in the anchor body, and the secondary spraying of the free section, comprehensively improving the overall construction quality of the anchor cable, saving materials, and reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of anchor cable construction according to an embodiment of the present invention;

[0026] Figure 2 A schematic cross-sectional view of a positioning bracket according to an embodiment of the present invention;

[0027] Figure 3 A top view of a positioning bracket according to an embodiment of the present invention;

[0028] Figure 4 is a schematic diagram of a guiding device according to an embodiment of the present invention;

[0029] Figure 5 for Figure 4 Section view along line AA.

[0030] Description of reference numerals:

[0031] 1. Guiding device; 11. Support frame; 12. Roller; 13. Guide frame; 131. Fixed frame; 132. Movable frame; 133. Lock; 134. Handle; 2. Positioning bracket; 21. Installation part; 3. Anchor cable; 4. Waist beam. DETAILED DESCRIPTION

[0032] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0033] The following is combined with Figure 1-5 The present invention is described in further detail.

[0034] The embodiment of the present invention discloses a method for constructing a prestressed rotary grouting anchor cable in a foundation pit. Figure 1-Figure 5 The construction method of prestressed rotary grouting anchor cable in foundation pit includes the following steps:

[0035] S1. After the pile row facade surface layer is completed, a hole-making machine is used to drill holes at the jet grouting piles. The drilling depth is greater than the diameter of the jet grouting piles. At the same time, the steel strands and the anchor end extrusion anchors are made and locked;

[0036] S2, replace the drill bit with a spray head, set the steel strand resistance-free guide device 1 at a suitable position behind the rotating motor, and stir the cement slurry at the same time;

[0037] S3, open the guide device 1, put the steel strand in and lock it, introduce the steel strand into the center anchor plate at the nozzle, wrap it around the spraying pipe with the positioning bracket 2, and fix the steel strand at the corresponding position of the positioning bracket 2;

[0038] S4, jacking anchor cable 4, start grouting when the depth exceeds the diameter of the jet pile, the drill rod rotates forward and reverse alternately to jack up, and the mud overflows outward with the anchor hole. When adding the drill rod, the positioning bracket is set synchronously to ensure that the anchor cable 4 is always in the middle of the anchor hole;

[0039] S5. Apply butter on the steel strand according to the depth of the free anchor cable 4, and install a plastic sleeve. The two ends of the sleeve are fixed firmly and tightly on the steel strand;

[0040] S6. When the anchor cable 4 is pushed to the specified depth, the drill rod starts to retreat, and the drill rod rotates alternately forward and reverse during retreat;

[0041] S7, after the shotcrete depth of the fixed end of the anchor cable 4 is reached, the shotcrete of the free section is stopped and the drill rod is withdrawn;

[0042] S8. Install the waist beam 5 made of channel steel and complete the tensioning of the anchor cable 4 after the anchor body strength reaches 75% of the design value.

[0043] The detachable positioning bracket 2 effectively distributes the steel strands evenly around the drill rod shotcrete pipe, and the steel strands are firmly fixed and not loose. The drill rod shotcrete pipe pushes the anchor cable forward while the steel strands are guided by the resistance-free device 1. When adding the drill rod shotcrete pipe, it is convenient to set the positioning bracket 2, and the steel strands will not be scattered. When the drill rod shotcrete pipe retreats to the free section, the grouting is stopped, and the slurry sprayed by the free section pushes forward to form a protective wall on the anchor hole wall, which effectively solves the problems of the anchor cable 4 being deflected and not centered in the anchor body and the secondary grouting of the free section, comprehensively improving the overall construction quality of the anchor cable, saving materials, and reducing costs.

[0044] In this embodiment, the guiding device 1 includes a support frame 11 and a roller 12 arranged on the support frame 11. The anchor cable 3 is moved into the anchor hole by the roller 12 on the support frame 11. The guiding device 1 reduces the friction and resistance of the anchor cable 3 during the movement through the cooperation of the support frame 11 and the roller 12, thereby improving the efficiency and accuracy of the construction of the anchor cable 3. The anchor cable 3 can move into the anchor hole more smoothly and without resistance, which effectively solves the problems of inefficiency and inaccurate positioning of the anchor cable 3 due to friction and resistance during the construction process.

[0045] In this embodiment, a guide frame 13 for installing a roller 12 is provided on the support frame 11. The guide frame 13 is arranged in a circular shape. The rollers 12 are evenly arranged on the inner side of the guide frame 13. The anchor cable 3 passes through the guide frame 13 and contacts the roller 12, so that the anchor cable 3 can contact the roller 12 when passing through the guide frame 13, thereby reducing the friction of the anchor cable 3 when moving, and improving the installation efficiency and accuracy of the anchor cable 3.

[0046] In this embodiment, the rollers 12 are arranged in multiple rows along the moving direction of the anchor cable 4. The rollers 12 arranged in multiple rows can make the anchor cable move more smoothly and can reduce the friction generated by the anchor cable 4 during the movement as much as possible.

[0047] In this embodiment, the guide frame 13 includes a fixed frame 131 fixed on the support frame 11 and a movable frame 132 arranged on the fixed frame 131. One side of the fixed frame 131 and the movable frame 132 are hinged and buckled together to form a circular guide frame 13. The fixed frame 131 and the movable frame 132 are provided with a lock 133 that fixes the movable frame 132 on one side that can be opened and closed. The fixed frame 131 and the movable frame 132 are hinged and buckled together on one side to form an integral circular guide frame 13. The hinged design allows the movable frame 132 to rotate around the hinge point to achieve opening and closing. The other side is fixed by setting the lock 133 to fix the movable frame 132, so that the guide frame 13 can be stably maintained in a closed state when in use. The lock 133 can be used. Various forms, such as spring locks, bolt locks, etc., are used to ensure that the movable frame 132 can be firmly fixed when closed. In addition, the materials of the movable frame 132 and the fixed frame 131 can be made of high-strength metal materials to ensure that they can withstand greater forces during construction. The design of the guide frame 13 allows for quick and convenient installation and disassembly during construction, especially during the construction of the foundation pit anchor cable 3 and the surface layer 4. The opening and closing function of the guide frame 13 allows construction personnel to easily place the anchor cable 3 into the guide frame 13 and move it to the anchor hole through the roller 12, thereby improving construction efficiency. At the same time, the stability and firmness of the guide frame 13 also ensure the accurate positioning of the anchor cable 3 during construction, reducing errors and safety hazards that may occur during construction.

[0048] In this embodiment, a handle 134 is provided on the openable side of the movable frame 132. The handle 134 can be provided on the side or top of the movable frame 132 and installed by screw fixing or welding. The material of the handle 134 can be selected from metal or high-strength plastic to ensure its durability and reliability. By providing the handle 134, the operator can save effort and convenience when opening and closing the movable frame 132, avoiding the difficulties and inconveniences that may occur during manual opening and closing.

[0049] In this embodiment, the positioning bracket 2 is arranged in an annular shape, the steel strands are evenly arranged on the circumference of the positioning bracket 2, and the drill rod passes through the positioning bracket 2. The annular design of the positioning bracket 2 can be achieved by different materials and structures. For example, the positioning bracket 2 can be made of steel or alloy materials to provide sufficient strength and durability. The annular part of the positioning bracket 2 can be manufactured by an integrated molding process, or spliced ​​by multiple arc segments, which can be convenient for transportation and installation. The uniform arrangement of the steel strands can be achieved by setting a plurality of fixing holes or clamping devices on the circumference of the positioning bracket 2. These fixing holes or clamping devices can be adjustable to accommodate steel strands of different diameters and quantities; the positioning bracket 2 is arranged in an annular shape to ensure that the steel strands are evenly distributed on the circumference of the bracket during installation, so as to avoid the steel strands from being offset during the drilling process. The drill rod passes through the positioning bracket 2 to ensure stability and accuracy during the drilling process. The annular positioning bracket 2 and the evenly arranged steel strands solve the problem of inaccurate positioning of the anchor cable 3 in the construction of the foundation pit side wall support, and ensure the stability and safety of the anchor cable 3 construction.

[0050] In this embodiment, a plurality of mounting portions 21 for mounting the steel strands are evenly arranged on the circumference of the positioning bracket 2. One side of the mounting portion 21 can be opened and closed for placing the steel strands therein. This design can be achieved through hinges and locks. One side of the mounting portion can be connected to the positioning bracket 2 through a hinge, and a lock is provided on the other side. When the steel strand needs to be installed, the lock can be opened to open the mounting portion 21. After the steel strand is placed in, the lock can be closed to fix the steel strand in the mounting portion 21. The lock can be a spring lock or a spiral lock to ensure that the mounting portion can firmly fix the steel strand when closed, thereby achieving effective installation and fixation of the steel strand, thereby solving the problem of installation and fixation of the steel strand on the positioning bracket 2.

[0051] In this embodiment, one side of the positioning bracket 2 can be opened and closed to allow the drill rod to pass through. This openable and closable positioning bracket 2 can be achieved in a variety of ways. For example, a hinge structure can be used to enable one side of the positioning bracket 2 to be opened and closed like a door; a sliding structure can also be used to enable one side of the positioning bracket 2 to slide open and close. In addition, in order to ensure the stability and firmness of the positioning bracket 2 during the opening and closing process, a locking device, a snap buckle, or the like can be provided at the opening and closing part of the positioning bracket 2 to ensure that the positioning bracket 2 is easy to operate during use and can firmly and reliably fix the drill rod.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for construction of prestressed rotary grouting anchor cables in foundation pits, characterized in that: The following steps are involved: S1. After the pile row facade surface layer is completed, a hole-making machine is used to drill holes at the jet grouting piles. The drilling depth is greater than the diameter of the jet grouting piles. At the same time, the steel strands and the anchor end extrusion anchors are made and locked; S2. Replace the drill bit with a spray head, set a steel strand resistance-free guide device at a suitable position behind the rotating motor, and stir the cement slurry at the same time; S3. Open the guide device, put the steel strand in and lock it, introduce the steel strand into the center anchor plate at the nozzle, wrap it around the spraying pipe with a positioning bracket, and fix the steel strand at the corresponding position of the positioning bracket; S4. Push the anchor cable in. When the depth exceeds the diameter of the jet pile, start spraying. The drill rod rotates forward and backward alternately to push in. The mud overflows out of the anchor hole. When adding the drill rod, set the positioning bracket at the same time to ensure that the anchor cable is always in the middle of the anchor hole. S5. Apply butter on the steel strand according to the depth of the free anchor cable, and install a plastic sleeve. The two ends of the sleeve are fixed firmly and tightly on the steel strand; S6. When the anchor cable is pushed to the specified depth, the drill rod starts to retreat, and the drill rod rotates forward and backward alternately during retreat; S7. After the shotcrete depth of the anchor cable fixed end is reached, the shotcrete of the free section is stopped and the drill rod is withdrawn; S8. Install the waist beam made of channel steel and complete the anchor cable tensioning after the anchor body strength reaches 75% of the design value.

2. The method for construction of foundation pit anchor cables and surface layers according to claim 1, characterized in that: The guiding device comprises a supporting frame and a roller arranged on the supporting frame, and the anchor cable moves into the anchor hole through the roller on the supporting frame.

3. The method for construction of foundation pit anchor cables and surface layers according to claim 2 is characterized in that: A guide frame for mounting rollers is arranged on the support frame, the guide frame is arranged in a circular shape, the rollers are evenly arranged inside the guide frame, and the anchor cable passes through the guide frame and contacts the rollers.

4. The method for construction of foundation pit anchor cables and surface layers according to claim 3 is characterized in that: The rollers are arranged in multiple rows along the moving direction of the anchor cable.

5. The method for construction of foundation pit anchor cables and surface layers according to claim 3 is characterized in that: The guide frame includes a fixed frame fixed on the support frame and a movable frame arranged on the fixed frame. One side of the fixed frame and the movable frame are hinged and buckled together to form a circular guide frame. The openable and closable side of the fixed frame and the movable frame is provided with a lock to fix the movable frame.

6. The foundation pit anchor cable and surface layer construction method according to claim 5 is characterized in that: A handle is provided on one side of the movable frame that can be opened and closed.

7. The foundation pit anchor cable and surface layer construction method according to claim 1 is characterized in that: The positioning bracket is arranged in a ring shape, the steel strands are evenly arranged on the circumference of the positioning bracket, and the drill rod passes through the positioning bracket.

8. The method for construction of foundation pit anchor cables and surface layers according to claim 7, characterized in that: A plurality of mounting parts for mounting the steel strands are evenly arranged on the circumference of the positioning bracket, and one side of the mounting part can be opened and closed for placing the steel strands therein.

9. The foundation pit anchor cable and surface layer construction method according to claim 8, characterized in that: One side of the positioning bracket can be opened and closed for allowing the drill rod to pass through.

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