Prefabricated tunnel prestressed anchor and manufacturing method and use method therefor

Abstract

A prefabricated tunnel prestressed anchor comprises an anchor rod, the anchor rod comprises a free section and a prestressed section which are arranged in sequence; the prestressed section of the anchor rod is sleeved with a steel casing, holes are formed in the steel casing, a filler material is arranged between the steel casing and the anchor rod and filled in a space between the steel casing and the anchor rod after a prestress is applied to the anchor rod on a tensioning bench, and when the filler material is electrified, the structure of the filler material is destroyed; sleeves are arranged at two ends of the steel casing, and grout plugs used for sealing the steel casing are arranged in openings of the sleeves. The prestressed anchor can be directly installed in site to be used, a prestress is applied after the structure of the filler material is destroyed.

What is claimed is: 
     
         1 . A prefabricated tunnel prestressed anchor, comprising an anchor rod, wherein the anchor rod comprises a free section and a prestressed section which are arranged in sequence;
 the prestressed section of the anchor rod is sleeved with a steel casing, holes are formed in the steel casing, a filler material is arranged between the steel casing and the anchor rod and filled in a space between the steel casing and the anchor rod after a prestress is applied to the anchor rod on a tensioning bench, and when the filler material is electrified, a structure of the filler material is destroyed;   sleeves are arranged at two ends of the steel casing, and grout plugs used for sealing the steel casing are arranged in openings of the sleeves.   
     
     
         2 . The prefabricated tunnel prestressed anchor according to  claim 1 , wherein an outer diameter of the steel casing is less than a diameter of a borehole, an inner diameter of the steel casing is 20-25 mm greater than an outer diameter of the anchor rod, and a length of the steel casing is the same as a length of the prestressed section in a tensioned state. 
     
     
         3 . The prefabricated tunnel prestressed anchor according to  claim 1 , wherein the steel casing is configured to be electrically conductive to conduct current to the filler material to destroy the structure of the filler material. 
     
     
         4 . The prefabricated tunnel prestressed anchor according to  claim 1 , wherein a diameter of the holes is 5-15 mm, and a distance between every two adjacent said holes is 20-30 cm. 
     
     
         5 . The prefabricated tunnel prestressed anchor according to  claim 1 , wherein a wall thickness of the sleeves is 6-10 mm, and each said sleeve comprises:
 a threaded portion connected to the steel casing, wherein an inner diameter of the threaded portion matches an outer dimeter of the steel casing; and   a grout plug receiving portion having a space for receiving the corresponding grout plug.   
     
     
         6 . The prefabricated tunnel prestressed anchor according to  claim 5 , wherein a wall thickness of the steel casing is 4-6 mm, threads are arranged at the two ends of the steel casing respectively, and the two ends of the steel casing are connected to the threaded portions by means of the threads. 
     
     
         7 . The prefabricated tunnel prestressed anchor according to  claim 1 , wherein the grout plugs are made from an elastic material; middle portions of the grout plugs are protrusive to form spindle structures, an outer diameter of front and rear ends of the grout plugs is the same as an inner diameter of the sleeves, and an outer diameter of the protrusive middle portions is 3-4 mm greater than the inner diameter of the sleeves. 
     
     
         8 . The prefabricated tunnel prestressed anchor according to  claim 1 , wherein the filler material is an organic material with fluidity, compressive strength after solidification, and bond strength to the anchor rod satisfying preset conditions. 
     
     
         9 . A manufacturing method for the prefabricated tunnel prestressed anchor according to  claim 1 , comprising:
 installing the steel casing at a set position on a tensioning bench, wherein an axis of the steel casing pipe is consistent with a tensioning axis and is kept horizontal, a length of the steel casing is the same as a length of the prestressed section in a tensioned state, and the holes in the steel casing are kept facing upwards; installing the sleeves at the two ends of the steel casing, and installing the grout plugs at ends of two sides of the sleeves;   allowing the anchor rod to penetrate through the steel casing, placing the prestressed section in the steel casing, tensioning the anchor until a set prestress is obtained, and injecting the filler material into a space between the steel casing and the anchor rod by means of the holes; and   when the filler material is solidified and satisfies a design strength requirement, relaxing two ends of the anchor rod, and before the prestressed anchor is placed in a warehouse to be further cured, detaching the grout plugs and sleeves from the two ends of the steel casing, such that the prefabricated tunnel prestressed anchor is obtained.   
     
     
         10 . A use method for the prefabricated tunnel prestressed anchor according to  claim 1 , comprising:
 installing the prefabricated tunnel prestressed anchor in a borehole, burying a wire in the steel casing, leading out of the wire, allowing the wire to penetrate through a grout plug together with a grouting pipe, connecting the grouting pipe to a reserved grouting hole, and injecting grout into a gap between the anchoring section and the borehole and a gap between the steel casing and the borehole; and   after the gaps are full of grout and the grout satisfied a design strength requirement, connecting the prestressed anchor to a power supply by means of the wire to destroy the structure of the filler material to eliminate a gripping effect of the filler material on the prestressed anchor so as to transfer a prestress to surrounding rock, such that prestressed anchor support requirements are satisfied.