Sectional modular large-deformation-resistant impact-resistant composite rock bolt and its assembling method

Abstract

This invention puts forward a sectional modular large-deformation-resistant impact-resistant composite rock bolt and its assembling method. The outer anchor module of this composite rock bolt consists of the outer anchor end, anchor tubes and anchor piers, all of which are bonded with the borehole wall through the anchorage agent to act as a full-grouted bolt. And the inner anchor module consists of the outer anchor end, anchor piers, springs and threaded rod. The threaded rod, under the traction by the outer anchor end, presses the inner anchor springs to distribute the anchoring force to the anchor piers, which then pass such force as a pressure to the anchoring agent, thus playing the role of a pressure-dispersive anchor. Before the failure of the anchor tube, the inner anchor module is in parallel with the outer anchor module, playing the role of auxiliary anchorage on surrounding rock; after the failure of the anchor tube, such structure can yield and buffer effectively against the surrounding rock and realize secondary high-strength support timely.

Claims

1. A sectional modular large-deformation-resistant impact-resistant composite rock bolt, wherein the composite rock bolt is divided into an outer anchor module and an inner anchor module; wherein said outer anchor module comprises a set of anchor tubes, anchor piers between the anchor tubes, and an outer anchor end, wherein the set of anchor tubes include a head anchor tube, several central anchor tubes and a tail anchor tube; each of said anchor piers is connected with the anchor tubes at two ends through threads, and an assembly between two adjacent anchor piers is called an anchorage section; said outer anchor end includes an anchor plate, a preloading spring, an anchor ring and a nut; wherein said anchor ring is connected with the tail anchor tube through threads; the preloading spring is disposed on a shaft portion of the anchor ring having a smaller diameter than a head portion of the anchor ring and secured against an outer surface of the anchor plate; under pressure of the preloading spring, an inner surface of the anchor plate is pressed tightly against a surface of a surrounding rock and an outer end surface of the anchor ring is secured against the nut; said inner anchor module, located inside enclosed space formed by the outer anchor module, includes a threaded rod, anchor piers, inner anchor springs and baffle rings, wherein said anchor piers and inner anchor springs are disposed the threaded rod; one end of the inner anchor spring is set in a spring groove on an edge of a center hole of the anchor piers, and the other end of the inner anchor spring is retained on the threaded rod by said baffle rings, the baffle rings and the threaded rod are connected through threads; a locking rubber ring is set at one end of each said baffle ring and nut, respectively, to prevent them from moving in the direction of spring extension; said outer anchor module and inner anchor module are connected through the outer anchor end.

2. The sectional modular large-deformation-resistant impact-resistant composite rock bolt according to claim 1 wherein said threaded rod is either a single piece or an assembly formed by connecting several threaded rods via casing tubes.

3. The sectional modular large-deformation-resistant impact-resistant composite rock bolt according to claim 1 wherein all threaded parts of said composite rock bolt are right-hand threaded except for the external thread of the anchor piers.

4. The sectional modular large-deformation-resistant impact-resistant composite rock bolt according to claim 1 wherein a diameter of a central circular hole of the anchor pier shoulder is identical to internal diameter of the inner anchor spring, both of which are slightly larger than the major diameter of the threaded rod, that the inner diameter of the anchor tube is slightly larger than the external diameter of the baffle ring, that the diameter of the central hole of the anchor plate is slightly larger than the external diameter of the anchor tube, and that the internal diameter of the preloading spring is slightly larger than the external diameter of the shaft portion of the anchor ring.

5. A method for assembling the sectional modular large-deformation-resistant impact-resistant composite rock bolt according to claim 1 including the following steps: Step I: implementing said composite rock bolt from a central part of the threaded rod to the two ends orderly by assembling the anchor piers, inner anchor springs, baffle rings, and locking rubber rings orderly in the central part of the threaded rod; Step II: assembling central anchor tubes at the two ends of each central anchor pier, and then assembling the anchor piers, inner anchor springs, baffle rings and locking rubber rings orderly at the two ends; Step III: assembling the head anchor tube and tail anchor tube, and assembling the anchor plate, preloading spring, anchor ring, nut and locking rubber ring at the outer anchor end, in that order.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is the structural schematic diagram of the composite rock bolt set forth by this invention;

(2) FIG. 2 is the enlarged view of Point A in FIG. 1;

(3) FIG. 3 is the enlarged view of Point B in FIG. 1;

(4) FIG. 4 is the structural schematic diagram of the anchor pier of the composite rock bolt set forth by this invention;

(5) FIG. 5 is the side view of FIG. 4;

(6) FIG. 6 is the structural schematic diagram of the baffle ring of the composite rock bolt set forth by this invention;

(7) FIG. 7 is the side view of FIG. 6;

(8) FIG. 8 is the structural schematic diagram of the anchor ring of the composite rock bolt set forth by this invention;

(9) FIG. 9 is the side view of FIG. 8;

(10) FIG. 10 is the structural schematic diagram of the nut of the composite rock bolt set forth by this invention;

(11) FIG. 11 is the side view of FIG. 10;

(12) FIG. 12 is the schematic diagram of assembly step 1 of this invention;

(13) FIG. 13 is the schematic diagram of assembly step 2 of this invention;

(14) FIG. 14 is the schematic diagram of assembly step 3 of this invention;

(15) FIG. 15 is the schematic diagrams of the composite rock bolt before and after the failure of an anchor tube.

SPECIFIC IMPLEMENTATION

(16) A further description of this invention is provided below in combination with the drawings and specific implementation means.

(17) FIGS. 1-11 show a sectional modular large-deformation-resistant impact-resistant composite rock bolt, which consists of the outer anchor module and inner anchor module. The said outer anchor module comprises a set of anchor tubes, anchor piers (3) between the tubes, and outer anchor end. The set of anchor tubes include a head anchor tube (21), several central anchor tubes (22) and a tail anchor tube (23). The said anchor pier (3) is connected through threads to anchor tubes at both ends. The part between every two adjacent anchor piers (3) is an anchorage section. The said outer anchor end comprises the anchor plate (7), preloading spring (8), anchor ring (9) and nut (10). The said anchor ring (9) and the tail anchor tube (23) are connected through threads. The preloading spring (8) is set on the thin part of the anchor ring (9). The preloading spring (8) presses tightly against the outer surface of the anchor plate (7). The inner surface of the anchor plate (7), pushed by the preloading spring (8), is tightly pressed against the surface of surrounding rock. And the outer end surface of the anchor ring (9) clings tightly to the nut (10). The said inner anchor module is located inside the enclosed space formed by the outer anchor module. The inner anchor module comprises the threaded rod (1), anchor piers (3), inner anchor springs (4) and baffle rings (5). The said anchor piers (3) and inner anchor springs (4) are set on the threaded rod (1). One end of the inner anchor spring is positioned in the spring groove on the edge of the central hole of the anchor pier (3); and the other end is restricted by the baffle ring (5) to a certain range of length. The baffle ring (5) and threaded rod (1) are connected through threads. There is a locking rubber ring (6) set on one end of the said baffle ring (5) and nut (10), respectively, to prevent them from moving in the direction of spring extension. The said outer anchor module and inner anchor module are combined through the anchor piers and outer anchor end into a whole.

(18) Depending on the length requirement of rock bolt, the said threaded rod (1) can be a single piece or an assembly formed by connecting several threaded rods with casing tubes. All threaded parts of the said composite rock bolt adopt the right-hand thread except for the external thread of the anchor pier (3), which is left-hand threaded. The diameter of the central circular hole of the said anchor pier (3) is identical to the internal diameter of the inner anchor spring (4), both of which are slightly larger than the major diameter of the threaded rod (1); the inner diameter of the anchor tube is slightly larger than the external diameter of the baffle ring (5); the diameter of the central hole of the anchor plate (7) is slightly larger than the external diameter of the anchor tube; and the internal diameter of the preloading spring (8) is slightly larger than the external diameter of the thin part of the anchor ring (9).

(19) The method for assembling the aforementioned sectional modular large-deformation-resistant impact-resistant composite rock bolt includes the following steps.

(20) As shown in FIG. 12, Step I: The assembly of the said composite rock bolt is implemented from the central part of the threaded rod to the two ends orderly. Firstly, assemble the anchor piers, inner anchor springs, baffle rings, and locking rubber rings orderly in the central part of the threaded rod;

(21) As shown in FIG. 13, Step II: Secondly, assemble the central anchor tubes at the two ends of each central anchor piers, and then assemble the anchor piers, inner anchor springs, baffle rings and locking rubber rings orderly at the two ends;

(22) As shown in FIG. 14, Step III: Then assemble the head anchor tube and tail anchor tube, and finally assemble orderly the anchor plate, preloading spring, anchor ring, nut and locking rubber ring at the outer anchor end.

(23) The working principle and process of this invention is the following.

(24) This invention is an organic combination of the sectional modular full-grouted tubular rock bolt (the outer anchor module) and the impact-resistant pressure-dispersive rock bolt (the inner anchor module). The basic principle of this invention is described as follows: the part between every two adjacent anchor piers is an anchorage section; the outer anchor module consists of the outer anchor end, anchor tubes and anchor piers, all of which are bonded with the borehole wall through the anchorage agent to act as a full-grouted bolt; the inner anchor module consists of the outer anchor end, anchor piers, springs and threaded rod. The threaded rod, under the traction by the outer anchor end, presses the inner anchor springs to distribute the anchoring force to the anchor piers, which then pass such force as a pressure to the anchoring agent, thus playing the role of a pressure-dispersive anchor; before the failure of the anchor tube, the inner anchor module is in parallel with the outer anchor module, playing the role of auxiliary anchorage on surrounding rock; after the failure of the anchor tube, such structure can play the role of buffering and yielding against the surrounding rock and realize secondary high-strength support in a timely manner. In each anchorage section, the high-strength anchor tube, inner anchor spring and high-strength threaded rod play the leading role in load bearing orderly at different work stages, allowing each anchorage section to perform the three-stage load-bearing characteristics of resistance-yielding-resistance, i.e. primary high-strength anchoring, elastic buffering, and secondary high-strength anchoring. All anchorage sections are relatively independent but connected closely each other, realizing the long-term effective maintenance of surrounding rock while ensuring the reliability of the rock bolt itself.

(25) Take the rock bolt with three anchorage sections as an example. Its working principle and process are shown in FIG. 15. The l.sub.t1, l.sub.t2 and l.sub.t3 in the figure represent the effective lengths of the anchor tubes of the head anchorage section, central anchorage section and tail anchorage section, respectively. The l.sub.s1, l.sub.s2 and l.sub.s3 represent the effective lengths of the springs of the head anchorage section, central anchorage section and tail anchorage section, respectively. The l.sub.r1, l.sub.r2 and l.sub.r3 represent the effective lengths of the rods of the head anchorage section, central anchorage section and tail anchorage section, respectively. And the .sub.burst represents the amount of extension suddenly occurring after the failure of the tail anchor tube.

(26) Given that the coefficients of elasticity of the inner anchor springs are k.sub.t, k.sub.2 and k.sub.3, respectively, that the compressive deformation amounts are l.sub.s1, l.sub.s2 and l.sub.s3, respectively, and that the acting forces on the anchor piers are F.sub.s1, F.sub.s2 and F.sub.s3, respectively, it can be determined according to the Hooke's law that the formulas for calculating the acting forces on the anchor piers are as follows:
F.sub.s1=k.sub.1.Math.l.sub.s1(1)
F.sub.s2=k.sub.2.Math.l.sub.s2(2)
F.sub.s3=k.sub.3.Math.l.sub.s3(3)

(27) Given that the modulus of deformation of the threaded rod is E, that the effective area of the cross section is S, that the deformation amounts of the sections are l.sub.r1, l.sub.r2 and l.sub.r3, respectively, and that the axial forces are F.sub.r1, F.sub.r2 and F.sub.r3, respectively, the formulas for calculating the axial forces of the sections of the threaded rod are:
F.sub.r1=E.Math.S.Math.l.sub.r1/l.sub.r1(4)
F.sub.r2=E.Math.S.Math.l.sub.r2/l.sub.r2(5)
F.sub.r3=E.Math.S.Math.l.sub.r3/l.sub.r3(6)

(28) According to the force balance relationship, the relations between the acting forces applied by the spring on the anchor piers and the axial forces of the threaded rod are indicated below:
F.sub.r1=F.sub.s1(7)
F.sub.r2=F.sub.r1+F.sub.s2(8)
F.sub.r3=F.sub.r2+F.sub.s3(9)

(29) According to formulas (1), (4) and (7), it can be determined that k.sub.1.Math.l.sub.s1=E.Math.S.Math.l.sub.r1/l.sub.r1. In order to make the spring play an effective role of buffering and yielding before reaching its compression limit so as to avoid the premature breakage of the threaded rod, it is required to make the threaded rod's deformation amount l.sub.r1 significantly less than the spring's compression amount l.sub.s1, i.e. the threaded rod's rigidity E.Math.S/l.sub.r1 shall be significantly higher than the inner anchor spring's rigidity k.sub.1.

(30) The first stage load bearing of the rock bolt, called the primary high-strength anchoring, takes place from the installation of the rock bolt until the failure of the anchor tube, during which the anchorage property of the entire rock bolt depends mainly on the bonding characteristics of the anchor tube. In this stage, the anchorage on surrounding rock is mainly realized through the high-strength anchor tubes of the outer anchor module acting as a full-grouted rock bolt, and meanwhile the inner anchor module, acting as a pressure-dispersive rock bolt, plays the role of auxiliary support on surrounding rock.

(31) Given that the extension amounts of the anchor tubes induced by the deformation of surrounding rock are l.sub.t1, l.sub.t2 and l.sub.t3, respectively, that the anchor pier of the head anchorage section is the fixed reference point, and that other anchor piers move toward the outside of the drill hole as the anchor tubes extend, it can be determined according to the deformation coordination relations between the structural parts that the following relational expressions exist among the deformation amounts of the anchor tubes, inner anchor springs and threaded rod:
l.sub.t1+l.sub.t2+l.sub.t3=l.sub.r1+l.sub.r2+l.sub.r3+l.sub.s1(10)
l.sub.s2=l.sub.s1+l.sub.r1l.sub.t1(11)
l.sub.s3=l.sub.s1+l.sub.r1+l.sub.r2l.sub.t1l.sub.t2(12)

(32) According to the above formulas and actually measured deformation amounts of the structural parts, the value and distribution of the anchoring force of the inner anchor module can be obtained. Accordingly, the parameters of the structural parts of the rock bolt can be optimized in design to ensure that the rock bolt has the optimal structural stability and support effectiveness under various specific engineering conditions.

(33) The second stage load bearing of the rock bolt, called the buffering and yielding, takes place from the failure of the anchor tube until the inner anchor spring reaching its compression limit. In this stage, the anchorage property of the anchorage section of the failed anchor tube depends on the spring's bearing behavior, while other anchorage sections still work as a grouted rock bolt. When an anchor tube breaks, the status of load bearing in this section will be changed from jointly undertaken by both the outer anchor module and inner anchor module to solely undertaken by the inner anchor module, which will result in a sudden drop of the anchoring force and thus cause the sudden movement .sub.burst of surrounding rock between the two sides of the breakage point. As the rigidity of the inner anchor spring is far less than that of the threaded rod, the spring will produce a relatively large compression deformation to absorb most energy released by surrounding rock, and meanwhile the anchoring force applied by the spring via the anchor pier on surrounding rock will increase sharply, thus playing the role of buffering, yielding and timely secondary reinforced support. In addition, the preloading spring at the outer anchor end, pushed by the surrounding rock and anchor plate, will produce a certain amount of compression deformation, which also absorbs partial energy of impact deformation and plays the role of auxiliary buffering and yielding.

(34) Given that in such process the compression amounts of the inner anchor springs are l.sub.s1, l.sub.s2 and l.sub.s3, respectively, and that the deformation amounts of the threaded rod at different sections are l.sub.r1, l.sub.r2 and l.sub.r3, respectively, the following relational expressions can be obtained according to the deformation coordination relations between the structural parts:
l.sub.r1+l.sub.r2+l.sub.r3+l.sub.s1=.sub.burst(13)
l.sub.s2=l.sub.s1+l.sub.r1(14)
l.sub.s3=l.sub.s2+l.sub.r2(15)

(35) It can be seen that the spring compression amounts newly added during the buffering period show the relation of l.sub.s1<l.sub.s2<l.sub.s3, i.e. the closer to the breakage point an inner anchor spring is, the larger compression amount it will produce.

(36) The third stage load bearing of the rock bolt, called the secondary high-strength anchoring, starts from the inner anchor spring having reached its compression limit. The anchorage property of the anchorage section of the failed anchor tube in this stage depends on the threaded rod's bearing behavior, while other anchorage sections still work mainly as a grouted rock bolt. When the inner anchor spring has reached its compression limit, its acting force on the anchor pier will no longer be influenced by the spring's mechanical parameters but depend on the threaded rod's stress-strain relationship and deformation of each anchorage section. After the first stage of primary high-strength anchoring and the second stage of buffering and yielding, the threaded rods at all anchorage sections usually have undergone relatively large deformation and consequently remain in a state of high stress, thus being able to provide timely secondary high-strength support on surrounding rock.

(37) It should be pointed out that as far as general technicians in this technical field are concerned, they may implement some improvements and modifications on the premise of following the principle of this invention, however, such improvements and modifications shall be deemed as within the coverage of protection of this invention. All components unspecified herein can be realized through existing technology.