JP2011084890A - Method for maintaining tension of wire rope for rock fall protection works - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To generate a constant or higher level of tension throughout the year even if the tension of a wire rope is fluctuated by being affected by heat and cold, to naturally restore the tension so that the tension can get closer to a desired tension, and to avoid the generation of an excessive load of the rope even if the tension of the wire rope is fluctuated by a variation with time. <P>SOLUTION: A rod-like anchor 3 which is erected on a rock bed and exerts firm fall inhibition resistance is used in a place of the rock-like natural ground; and a load-distribution ground-surface application anchor 4 equipped with a two-action point lever and a load dispersion plate 8 is used in a sediment or sand gravel place. A overall length variable steel material 15 which is bent in a corrugated shape which generates a resilient force in the direction of reducing constantly wavelength and is provided along a midway of the wire rope is used as an implement for adjusting the tension of the wire rope 1. In the application of the tension, the tension is applied in such a manner that the wavelength at laying the wire rope is set longer in winter than in summer. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for maintaining the tension of a wire rope in a rock fall protection work, and in particular, is applied to a rock fall protection work in which a wire rope is laid and pressed against a natural ground in order to prevent falling rocks and rocks scattered on the ground surface. Further, the present invention relates to a stretching method capable of applying a desired magnitude of tension to the rope.

  If there is a falling rock on the road under the slope, it may cause danger to pedestrians and traffic vehicles, or it will be impossible to pass the road. There are various methods for reinforcement, but the slope work depends greatly on the topography and soil quality, so every time it is devised. One of the measures to prevent collapse of rocks and rocks scattered on the ground surface is a wire net type rockfall protection work that lays a wire rope to hold the ground.

  Even if the ground is only rocky, or if it is a geology that includes both gravel and earth and sand in addition to the rock quality, in order to hold the floating rocks and rocks by laying the wire rope, It is imperative that the rope can be tensioned to exert a pressing force on the ground surface. In that case, both ends of the wire rope are firmly fixed, and the crossing of the wire rope laid in the vertical and horizontal directions is robust by the cross anchor clip etc. Currently, this is a major technical issue, and it is essential to take measures against it.

  The end of the rope is fixed to the head of the anchor on the surface of the anchor through a lashing tool, but a rock-like bar anchor is used in the rocky part, and in the case of sediment and gravel, the cement milk injection cavity is used. A formed long pipe anchor is used. In the latter, strong adhesion to the ground is achieved by solidification of cement milk rising from the underground tip along the anchor peripheral wall. This is because a large tension acts on the wire rope, and it is necessary to fix the wire rope against the pulling force. In general, the tension is applied to the rope by a cross anchor clip applied to the crossing portion of the rope whose ends are already fixed by anchors over the uneven surface layer. The anchor part uses the unevenness of the ground surface to generate rope tension to hold the head of floating stones and megaliths, while the clip part prevents the rope slippage at the intersection as described above, and the rope is loose It does not reach the intersection.

  Since the above-mentioned rod anchors and pipe anchors are well known, a detailed explanation of the structure is omitted, but the drilling machine for raising the latter anchor is much larger than that used for the former, and milk Even a pumping device must be attached. Incidentally, for example, Japanese Patent Application Laid-Open No. 2003-201713 discloses an anchor that attempts to enhance the pull-out resistance in a non-rocky ground that has a poor scaffolding and is often inconvenient for the installation of medium- and large-sized machines. In this method, an arm that can be swung a little is supported at a substantially middle point buried in the soil of the anchor, and a wire rope is secured to the tip of the arm that is exposed to the ground surface. Since the force applied to the arm reduces the tilting moment acting on the anchor, the pulling strength can be increased. The arm also puts the abdominal surface in the ground and demonstrates resistance to falling. A ground reinforcing plate is disposed on the ground surface side end of the arm to prevent the arm tip from sinking.

  It is not particularly difficult today to apply initial tension to the wire rope in any way. However, if the rock held by the rope weathers and sinks or slips even slightly, the rope loosens. In order to prevent this or prevent it from expanding, for example, Japanese Patent Application Laid-Open No. 2003-206535 proposes a cross anchor clip for suppressing the loosening of the rope intersection. At present, the concept of slip prevention fastening is permeating into the cross anchor clip in this type of protective work, and the conventional cross anchor clip of the cross rope contact type that may cause slipping and slipping tends to be excluded.

JP 2003-201713 A JP 2003-206535 A

  The above-mentioned anchor with an arm described in Patent Document 1 takes measures to prevent the arm from sinking into the surface layer. However, since the large force transmitted from the tip of the arm to the natural ground works in the direction along the surface layer, the ground reinforcing plate is placed along the surface of the natural ground. Therefore, the surface reinforcing plate must have a structure that can withstand a large shearing force between the ground surface. In order to prevent the displacement of the ground reinforcing plate, a large ground piercing blade is welded to the lower surface, and it becomes inevitable that the shape becomes bulky. Needless to say, a large number of these operations and installation operations to the unstable site at present are disadvantageous. Furthermore, in order to bury the arm, the ventral side of the anchor is dug up, and backfilling work and consolidation work are also accompanied. If the digging of the undergrowth is accompanied, the anchoring site will be weakened and the labor for reinforcement will increase.

  According to the cross anchor clip of Patent Document 2, the looseness of the wire rope at the crossing portion is reduced, and the wear between the ropes is advantageously reduced to some extent than before. However, rope wear is still inevitable. In addition, for high-torque fastening and inspection of individual bolts in clips that will be used with hundreds or thousands of pieces in one construction, the old model that only needs to demonstrate the fastening force that maintains the crossing Compared to the cross-anchor clip, it requires much hard work.

  By the way, the tension applied to the wire rope is highest when the tension is applied to the rope if the influence of thermal expansion is ignored. Then, as described above, if there is a change in the state of the natural ground due to weathering or the like, a situation where the tension is reduced occurs. If there is no crossing rope slippage due to the cross anchor clip, the looseness of the wire rope will be reduced, but it is impossible to recover the lost or reduced tension by itself.

  In addition, the general climate of Japan has four seasons, and the annual temperature difference is severe. If the temperature difference is about 40 ° C., for example, in the case of a 30-meter wire rope, a length variation of about 15 millimeters occurs. Even if a tension of a desired magnitude is applied at the time of tensioning, if the wire rope stretches by 15 millimeters as described above and the tension is released in the summer, the effect of preventing rock fall by holding the ground is drastically reduced. . On the other hand, the tension obtained by applying strongly in the summer becomes excessive tension due to the shrinkage in the winter, and drastically decreases the anchorage of the anchor for fixing the rope end and the anchor of the cross anchor clip at the rope crossing.

  The present invention has been made in view of the above problems, and its purpose is that even if the tension of the wire rope fluctuates due to the influence of cold and warm, it can generate a certain level of tension throughout the year, Even if the tension of the wire rope fluctuates due to changes over time, it can be naturally recovered to approach the desired tension and the occurrence of excessive rope tension can be avoided. Wire rope in rock fall protection work that realizes reduction of fastening work, secures rope end holding capacity with a compact structure even in non-rocky ground, and enhances durability of rope tension maintenance It is to provide a tension holding method.

  INDUSTRIAL APPLICABILITY The present invention is applied to a rope stretching method in a rock fall protection work in which a wire rope is laid at least vertically and horizontally to hold a natural ground in order to prevent the fall of floats and rocks. The characteristic features are as follows with reference to FIG. 1 and other drawings. As an anchor standing on the natural ground to hold the end of the wire rope 1, in the place where the natural ground is rocky, it is standing on the rock and exhibits a strong fall prevention resistance (for rocky) 2) is also used. On the other hand, as shown in FIG. 3, in the place where the natural ground is earthy and gravel, the head located on the ground surface of the pile 11 is supported so as to be pivotable in the vertical direction. A mounting portion 12 that anchors the end of the rope at a position away from it, and a pressing portion 13 that is provided at a position away from the fulcrum portion 14 to exert a force on the ground surface due to the moment generated by the rope tension acting on the mounting portion. A load-dispersing surface depositing type that exhibits a fall-preventing resistance with a two-action point type lever 7 having a load and a load distribution plate 8 that covers the earth and sand surface layer 6 and receives a load from the pressing portion 13 at a low surface pressure. An anchor 4 is used. As a tension adjuster for the wire rope 1, a full length variable steel material 15 (FIG. 6) is bent along the wire rope 1 by being bent into an arcuate shape or a wave shape, generating a resilient force in a direction that always reduces the chord length or wavelength. Are used). When laying the wire rope 1, the variable length steel material 15 is arranged in the middle of the wire rope, and the rope is bound so as not to separate from the steel material (see FIG. 10). The unfixed end of the wire rope 1 is attached to the bar-shaped anchor 3 or the load-dispersing surface-surrounding-type anchor 4 and placed on the ground, and the rope end is moored to the attachment portion 12 as shown in FIG. The pressing portion 13 is seated on the load distribution plate 8 by the moment around the fulcrum portion 14 generated in this manner. When applying tension by pulling the wire rope 1, in the summer laying, the string length or wavelength is applied with a tension that is larger than the free state length of the full length variable steel material 15, and in the winter laying, the string length or wavelength is set. Apply tension that is longer than the chord length or wavelength when laying the wire rope 1 in summer. In spring / autumn laying, tension is applied so that the chord length or wavelength is longer than the chord length or wavelength when laying a wire rope in summer and shorter than the chord length or wavelength when laying a wire rope in winter. Accordingly, if the wire rope 1 in FIG. 7D is thermally expanded and the tension is reduced, the elastic force of the full length variable steel material 15 is reduced to the chord length or wavelength corresponding to the remaining tension of the rope (see FIG. 7 (a)), by reducing the chord length of the bent portion of the rope along the variable length steel material 15, the rope is substantially pulled by hand, and part of the amount of rope expansion due to thermal expansion is absorbed. However, it leaves tension on the rope. When the wire rope 1 is thermally contracted and the tension is increased, the elastic force of the full length variable steel material 15 is expanded to the chord length or wavelength corresponding to the increased tension of the rope as shown in FIG. It is possible to avoid excessive tension on the rope while substantially extending the rope by increasing the chord length of the bent portion of the rope along the line and absorbing a part of the amount of reduction of the rope due to thermal contraction. Like that.

  When applying tension by pulling the wire rope, in place of the operation for laying time and thermal contraction of the rope, a tension that makes the chord length or wavelength larger than the free state length of the full length variable steel material 15 is applied, For example, even if the wire rope 1 is loosened due to sedimentation or displacement of the rock held by the rope, the elastic force of the full length variable steel material 15 reduces the chord length and wavelength according to the residual tension of the rope, and along the full length variable steel material 15 By increasing the bending of the portion of the rope, it is possible to substantially pull the rope and absorb the slack of the rope to restore the rope tension.

  With reference to FIG. 1, as rock fall protection work 2, the wire rope 1K may be laid on the diagonal of the rope frame formed by the wire ropes 1T and 1Y laid vertically and horizontally.

  As shown in FIG. 10, the variable length steel material 15 is a flat steel plate 21, and the wire rope 1 is bound to this steel plate by placing the wire rope along an arcuate or corrugated steel plate, at both ends of a string or at a wave node. At this point, the locking tool 22 prevents the separation from the steel plate.

  The steel rods 21B and 21C shown in FIGS. 16 and 18 are used as the variable-length steel member 15, and the wire rope 1 is bound to the steel rods by winding the wire rope around an arcuate or corrugated portion. It is good also as an aspect which is latched by the hook 22D formed by bending the steel bar end part at both ends, and the separation | separation from a steel bar is prevented.

  As shown in FIG. 13, the double acting point type lever 7 of the load distribution surface anchor 4 is attached to a line 23 connecting the fulcrum part 14 to be fitted to the head of the pile 11 and the attachment part 12. It is preferable that the line 24 connecting the portion 12 and the pressing portion 13 is substantially perpendicular.

  Consideration is made so that the wire rope 1 extending from the attachment portion 12 forms an angle of 45 degrees or more with respect to the line 23 connecting the fulcrum portion 14 and the attachment portion 12.

  According to the present invention, the rod-shaped anchor for rock is used in the place where the natural ground is rocky, and the load-dispersing surface-occluded anchor is used in the place where the soil is sandy or gravelly. Becomes strong, and a large tension can be applied to the wire rope stretched around the anchor. Since the variable length steel material that exerts elasticity in the direction of constantly reducing the chord length or wavelength is run along the wire rope, the total length of the rope can be reduced by changing the bending of the full length variable steel material due to the thermal expansion and contraction of the wire rope. The tension can be automatically adjusted so as to exert a tension higher than desired in a constant state. The rope slippage in the cross anchor clip is not a big problem, and the labor for the fastening operation can be greatly reduced.

  When laying a wire rope, apply a tension that makes the chord length or wavelength longer than the free length of the variable length steel material in summer, and in winter, apply a tension that makes the chord length or wavelength longer than those when laying the wire rope in summer. Try to hang. Therefore, as long as a tension of a certain magnitude or more is applied in winter, a predetermined tension or more can be applied to the wire rope during summer and winter. And since the difference in tension is smaller than when the full length variable steel material is not adopted, the load acting on the anchor does not become extremely different throughout the year. Since the alternating load of the load on the anchor placing hole wall is small and weakened, the anchor and the ground are kept in close contact with each other, and the standing state can be easily stabilized over a long period of time.

  It is only necessary to arrange a variable length steel material in the middle of the wire rope and bind the rope so as not to separate from the steel material. The occurrence of relative displacement in the longitudinal direction between the wire rope and the variable length steel material is substantially effective in adjusting the tension. It has no effect. Therefore, the operation of placing the rope along the full length variable steel is less burdensome. Combined with the light work of fastening operation of the cross anchor clip, the reduction and avoidance of heavy labor in harsh working environment with poor footing will contribute to the reduction of man-hours for rock fall protection work and promote cost reduction.

  When applying tension by pulling the wire rope, if the tension that makes the chord length or wavelength larger than the free state length of the variable length steel material is applied, not only the difference in temperature but also the weathering of the ground Even when the tension decreases, the tension can be recovered, and the rope tension can be maintained above a certain level.

  If the rock fall protection work has wire ropes laid on the diagonal line of the rope frame formed by the vertical and horizontal laying wire ropes, the rope laying density per area will increase, making it easier to hold not only large rocks but also cobbles. Become. If the tension of the diagonal rope is adjusted automatically, the rock cover protection effect by rock fall protection will be greatly enhanced.

  If the length-variable steel material is a flat steel plate, the rope along the steel plate surface and the prevention of separation by the locking tool can be achieved with a simple and less burdensome operation. If it becomes easy to bind the wire rope to the steel plate, it will greatly reduce the hard work on the sloping ground where the working environment is severe. By the way, since the flat steel plate is used as the main body, it can be inserted into the wire rope after a long time when looseness is found in the completed rock fall protection work. This makes it possible to repair an old rockfall protection work by simple operation.

  If a steel rod with a variable length is made into a bow or corrugated steel rod, the rope can be completely steeled by simply winding the wire rope and locking it to the hook formed by bending the ends at the ends of the string or wave. You can follow the stick. The operation is performed with at least one end of the wire rope not fixed to the anchor. Although the rope is strong, the rope can be made to follow the steel rod only by winding, so the burden is unexpectedly small. The burden on the steel rod along the rope is significantly smaller than the amount of high-torque fastening work at many locations on the cross-anchor clip. This will improve work efficiency and suppress the quality of materials.

  The double acting point lever of the load distribution surface type anchor has a substantially right angle to the line connecting the mounting part and the pressing part to the line connecting the fulcrum part and the mounting part to be fitted to the head of the pile. If so, the load from the pressing portion to the load distribution plate is introduced with reduced mechanical loss. Note that the two-action point lever manufactured by folding a steel plate that is cut into a substantially butterfly shape in half has a U-shaped base that serves as a fulcrum, thereby reducing the number of components and reducing the cost. It also contributes to

  If the wire rope extending from the attachment portion is at an angle of 45 degrees or more with respect to the line connecting the fulcrum portion and the attachment portion, the load distribution plate is burdened with 70% or more of the rope tension, Reduce the burden as much as possible and improve anchor stability.

The top view of an example of the rock fall protection worker to which the wire rope tension holding method according to the present invention is applied. (A) Explanatory drawing of wire rope in rocky ground where bar-shaped anchor is applied, (b) is the resistance to falling when the bar-shaped anchor is applied to earth and sandy gravel ground Explanatory drawing of this, (c) Explanatory drawing which shows a mode that the wire rope is tied to the rod-shaped anchor, and use of the winding grip used for it. Explanatory drawing of wire rope tension in earth and sandy and gravelly ground. The 5th page figure of a load distribution surface deposit type anchor. The load dispersion | distribution surface deposit type anchor, the two action point type lever which comprises it, explanatory drawing of a load distribution board, and the modified example figure of a two action point type lever. The 4th page figure of an example of the bow-shaped flat steel plate as a full length variable steel material. Explanatory drawing of the change of the elongation of a bow-shaped flat steel plate and the wire rope along it. Explanatory drawing of the elastic force generation mechanism when the edge part tensile load acts in full length variable steel materials. The tension | tensile_strength provision drawing of a wire rope in a load dispersion | distribution surface deposit type anchor. The top view and front view of the state which put the wire rope along the bow-shaped flat steel plate. Explanatory drawing of the latching tool of a U bolt locking tool and an example different from it. Explanatory drawing of the manufacture example and modification of a two action point type lever. Explanatory drawing about the action of force in a two action point type lever, and the mooring angle of a wire rope. The various aspect figure at the time of setting it as a corrugated full length variable steel material. Explanatory drawing of the inversion usage example of a flat steel plate, and an example along both surfaces. FIG. 4 is a four-sided view when the full-length variable steel material is formed of an arcuate steel rod. Explanatory drawing which shows the change of the shape when the state where the wire rope was wound around the bow-shaped steel bar, and tension was applied to it. The various aspect figure at the time of setting it as the full length variable steel material by a corrugated steel bar.

  Below, the tension maintenance method of the wire rope in the rock fall protection work which concerns on this invention is demonstrated in detail based on drawing showing the embodiment. FIG. 1 shows an example of a rock fall protective work 2 that lays a wire rope 1 at least vertically and horizontally to hold a natural ground in order to prevent collapse of floating stones 2a (see FIG. 2) and rocks 2b scattered on the ground surface. In this rock fall protection work, the anchors 3 and 4 that hold both ends of the wire rope 1 that are intentionally acted on by tension are employed that become stronger according to the hardness of the ground. In the middle of the wire rope 1, consideration is given to partially recovering the tension that has been weakened due to fluctuations in the environment or the like, or to relieve the excessive tension. In addition, the cross clip 1a, the cross anchor clip 1b, etc. are attached as needed to the crossing part of the wire rope, and the laying order of the wire rope is maintained. By the way, this rock fall protection work 2 is drawn on the assumption that the right half of the figure is a rocky natural ground, and the left half is an earth and sand natural ground.

  For example, rock fall protection may cause rocks that have been held down by weathering of the natural ground to sink or displace, and the rope may loosen later. Not only that, but in summer, the ropes heat up and become longer, resulting in lower tension. In winter, the rope shrinks and contracts, increasing tension. If the tension fluctuates due to these factors, the purpose of holding the ground will not be fulfilled, especially when the tension disappears due to thermal expansion. In addition, the pulling force acting on the anchor for maintaining the tension varies depending on the time and season. Such an alternating load reduces the ability to hold the ground and the anchor, which may lead to the weakness of the ground-holding protection work.

  Therefore, in the present invention, as an anchor standing on the natural ground in order to hold the end of the wire rope 1, it is erected on the bedrock 5 as shown in FIG. The rock-like rod-shaped anchor 3 exhibiting strong and strong fall prevention resistance is used. On the other hand, in the place 6 where the natural ground is earthy sand and gravel, the rod-like anchor 3 is likely to fall as shown in FIG. 2 (b). Therefore, the two-action point lever 7 and the load distribution plate 8 shown in FIG. Thus, the load distribution surface depositing type anchor 4 that exhibits the fall prevention resistance is used. This is an assembly of the metal fitting shown in FIG. 4, and its structure will be described in detail later. Incidentally, Japanese Patent Application Laid-Open No. 2007-297778 discloses a device that recalls the shape of the latter anchor.

  As shown in FIG. 2 (a), the rock anchor 3 has a rod shape, and a hole having a depth of, for example, 1 meter is formed in the rock 5 immediately below the surface soil 9 or exposed, and a solidified material is injected to fix the anchor. Plugged in. After curing the solidified material, it becomes a solid pile that exhibits sufficient holding power to secure the wire rope. This type of rod anchor is well known.

  As shown by the arrow 10 in FIG. 5A, the above-mentioned double action point type lever 7 is supported by the head portion of the hollow pile 11 so as to be slightly pivotable in the vertical direction. This has a rope attachment portion 12 and a pressing portion 13 that exerts a force on the natural ground as two action points. The attachment portion 12 anchors the rope end away from the fulcrum portion 14, and the pressing portion 13 exerts a force due to the moment generated by the rope tension acting on the attachment portion 12 on the load distribution plate 8. Therefore, the pressing part 13 is provided at a position away from both the fulcrum part 14 and the attachment part 12. By the way, the upper surface, side surface and cross section of the two-action point type lever 7 are represented in (b), the front surface of the load distribution plate 8 to be touched in detail later is in (c), the rear surface is in (d), and the pile portion is It is represented in (e).

  Currently, it is called a two-action point type lever, but on the work, it should have a substantially triangular shape as shown in the figure to increase the rigidity. This lever is selected at a position where the fulcrum part 14 is not in the middle of the line connecting the two action points, and the fulcrum part 14 forms the third vertex when the attachment part 12 and the pressing part 13 form a triangle, for example. It can be named as a dual action point V-shaped lever. Therefore, if there is no problem in strength or the like, the V-shape may be a lateral or downward V shape as shown in (f) or (g) of FIG.

  As can be seen from FIG. 3, the load distribution plate 8 is an iron plate that covers the earth and sand and gravel surface layer 6 and receives the load from the pressing portion 13 at a low surface pressure. Since this is to receive the force exerted on the ground surface due to the moment generated by the rope tension, consideration is given to improving the efficiency of load transmission to the ground. Therefore, consideration is given so that the load does not follow the surface layer but is intentionally inclined downward as illustrated. The surface of the earth is scooped out a little and a soil shoulder 6A is taken out, and a load distribution plate 8 is applied to the shoulder. Therefore, it suffices to provide a number of spikes 8A for preventing slippage on the lower surface of the iron plate.

  5B in FIG. 5C is a stay for increasing the rigidity of the central portion of the plate, and a hole 8C shown in FIG. 5D for receiving the claw 13A of the pressing portion 13 is opened in the vicinity thereof. I try to prevent slipping. Such a load distribution plate 8 may be installed by being buried shallowly near the surface layer as shown in FIGS. 13B and 13D. In any case, as long as the earth and sand surface layer 6 exists below the load distribution plate, the earth and sand surface layer is covered. In principle, it is refrained from dug up.

What should be noted as the rock fall protection work that is the subject now is the introduction of the full length variable steel material 15 shown in FIG. This generates a resilient force in a direction which always reduced to a free state length of the chord length L _P0 in FIG. 7, a tension adjusting plate bowed to be along the middle of the wire rope 1 But it should be said. Japanese Patent Application Laid-Open No. 2005-314981 discloses something that reminds of this.

  The principle of the present invention will be described below. When the wire rope thermally expands and the tension decreases, the elastic force of the variable length steel material reduces the chord length according to the residual tension of the rope, and increases the bending of the rope along the variable length steel material. Pull the ropes together. Absorbs part of the amount of rope expansion due to thermal expansion, leaving tension in the rope. On the other hand, if the wire rope heat shrinks and the tension increases, the elastic force of the variable length steel will lose the increased tension of the rope and expand the chord length, reducing the bending of the rope along the variable length steel Substantially pull out the rope. A part of the amount of shrinkage of the rope due to heat shrinkage is absorbed so that excessive tension can be avoided in the rope.

This is illustrated in FIG. 8 (a). (A) is simply a single line representing the full length variable steel material 15 which is bent into an arcuate shape and generates a resilient force in the direction of constantly reducing the chord length. In a free state where no force is applied to the left and right ends of the steel material, the end-to-end distance (= string length) is assumed to be L _PO . The fact that the elastic force is applied means that the steel material is made to have a reduced curvature (that is, a radius of curvature is increased) as shown by a broken line, a one-dot chain line, and a two-dot chain line with reference to FIG. Means that it is restored in the direction of the arrow 16 to become a solid line. Such a variable length steel material is manufactured by using spring steel or heat treatment.

Now, both ends as in FIG. 8 (a) (ii) when pulled with a force of F _1, and extended by [Delta] L _M1. (C) and (D) show that when they are pulled by the forces of F ₂ and F ₃ , they are extended by ΔL _M2 and ΔL _M3 , respectively. An example of a graph showing the relationship at this time is (c). The spring constants calculated for each are k ₁ , k ₂ , and k ₃ , and the values are generally different. However, in “force vs. elongation”, k ₁ , k ₂ , k ₃ = k _P Can be handled as being substantially linear as shown in the figure. If the chord length L _PO and curvature in the free state, the longitudinal elastic modulus E _P of the steel material, and the cross-sectional secondary moment I _P are determined, the change as shown in (b) becomes reproducible.

The following is an easy-to-understand explanation using specific values. I will refuse that it is only an example. Now, the distance L _W0 between the anchors of the vertical rope 1T of the rock fall protection work 2 (see FIG. 1) is 30 meters, that is, 30,000 millimeters. And a 30,000 millimeter wire rope (= L _W ) expands and contracts by 15 millimeters with a difference of 41.7 ° C. When the linear expansion coefficient α of the wire rope is 12 × 10 ⁻⁶ / ° C. and the maximum temperature difference ΔT between summer and winter at the construction site is 41.7 ° C., the difference in rope length ΔL _WT due to the temperature difference is ,
ΔL _WT = L _W × α × ΔT
= (30 × 10 ³ mm) × (12 × 10 ^{−6 /} ° C.) × (41.7 ° C.)
= 3 × 1.2 × 10 ⁻¹ × 41.7 = 15.0 mm (1)
Because it becomes.

The total of the elongation of the wire rope and the elongation of the string of the variable length steel material with respect to the magnitude of the tension is as shown in Table 1 below.

This is because a tensile load of 10,000 N was applied to a 30-meter wire rope, with the longitudinal elastic modulus (E _W ) of the wire rope being 2.1 × 10 ⁵ N / mm ² and the real cross-sectional area of the rope being 95 mm ² . The elongation of the rope at the time ΔL _WM = F × L _W / (E _W × A _W )
ΔL _WM = 10,000 × 30,000 / (2.1 × 10 ⁵ × 95)
= 3 × 10 ^8/2 × 10 ⁷
= 15.0 mm (2)
(See the fourth row from the bottom in Table 1). Since the elongation of the rope with respect to other loads is proportional, it is as shown in the other column of “Rope elongation” in Table 1. On the other hand, E _P × I _P (E _P is the longitudinal elastic modulus of the total length variable steel, I _P is the second moment of the same section) and the chord length are selected so that the stretch of the string is as shown in Table 1. And This can be obtained by calculating a curved beam. Incidentally, in FIG. 8, the relationship between the extension of the string and the tensile force when it is pulled with the force F _i in the direction of expanding the bow (i = 1, 2, 3) is linear (string extension spring constant k _i. = Constant = k _P ) as described above. However, the spring constant does not have to be constant. In short, the elastic deformation data shown in Table 1 may be acquired in advance. Once the material and dimensions are determined, it is easy to verify and correct the calculated values.

By the way, when a tension of 4,286 N is applied in winter, it is assumed that the distance between anchors is just 30 meters. From Table 1,
Total length = Rope length before loading + Rope stretch + String stretch
= L _WFW + 6.43 + 8.57 = 30,000
Therefore, the free state length of the wire rope in winter (rope length before loading) L _WFw is
30,000- (6.43 + 8.57) = 29,985 millimeters. In summer, this is expanded by 15 millimeters calculated by equation (1) to 30,000 millimeters. By the way, even if the wire rope is 29,900 millimeters shorter by 100 millimeters, for example, the elongation due to the thermal expansion of the rope is only 299/300 times, and it is still almost 15.0 millimeters. Therefore, 29,985 millimeter wire rope is treated as 15 millimeter extension in summer. This summer free state length (rope length before loading) L _WFS means that the anchor-to-anchor distance L _W0 is already 30 meters, so that the tension naturally disappears in summer. In other words, in summer, there is little or no force to hold the ground. It can be seen that in order to keep the tension generated in the summer, in the case of construction materials having the qualities according to Table 1, a tension exceeding 4,286 N must be applied in the winter. In the description here, it is assumed that the wire rope always needs a tension of 2,000 N or more throughout the year (hereinafter referred to as the minimum set tension).

Accordingly, (see column 2,000N in Table 1) with reference to FIG. 7, and multiplying the 2,000N in summer as tension, as shown in this case (a), 30 anchor distance L _W0 Suppose that it is exactly the meter.
Total length = Rope length before loading + Rope stretch + String stretch
= _LWFs + 2 x (1.50 + 2.00) = 30,000
Therefore, when the tension is released, L _WFs = 29,993 millimeters as shown in (b). As shown in (c), this wire rope is thermally contracted by 15 millimeters in winter and becomes L _WFw = 29,978 millimeters. As shown in (d), if the distance between anchors L _W0 is 30 meters, it is necessary to extend 22 millimeters. From Table 1, it can be seen that the tension to achieve 22 millimeter elongation is 6,280N. The rope stretch at this time is 9.40 millimeters and the string stretch is 12.60 millimeters, which provides an elongation of 22 millimeters. By the way, if the temperature difference is half that of spring and autumn, the expansion amount is 15 / 2≈8 millimeters, so 29,986 millimeters is obtained by adding 8 millimeters to 29,978 millimeters. If this is to be 30 meters, the distance between anchors needs to be increased by 14 millimeters. From Table 1, the tension to achieve an extension of 14 millimeters is 4,000N.

  In other words, taking the two seasons in winter and summer as an example, the wire rope will thermally expand in summer and reduce the tension from 6,280 N in winter to 2,000 N in winter. In order to balance the elastic force of the variable length steel material with the rope tension, the length of the 12.6 mm chord length is reduced to 4 mm. As a result, the chord length of the bent portion of the rope along the length-variable steel material is reduced, and the rope is substantially lifted by 8.6 (= 12.6-4.0) millimeters. More than half of the 15.0 millimeters of rope expansion due to thermal expansion is absorbed by the full length variable steel material. Nevertheless, the rope tension of the above-described minimum set tension of 2,000 N is ensured. Incidentally, the unabsorbed extension amount = 15.0−8.6 = 6.4 mm is compensated by the fact that the rope that had been extended by 3 mm has been extended by 9.4 mm.

  On the other hand, when a wire rope applied with a tension of 2,000 N in summer is heat-shrinked in winter and increases to 6,280 N, the variable length steel has increased from 1 mm to 42.6 mm. Presents. As a result, the chord length of the bent portion of the rope along the length-variable steel material is increased, and the rope is substantially drawn out by 8.6 millimeters. Replenish more than half of the 15 mm reduction due to heat shrinkage. Nevertheless, the rope tension can be kept at 6,280N, which is greater than the minimum set tension of 2,000N.

  By the way, if the variable length steel material is not interposed, 15.0 millimeters shortened by heat shrinkage in winter must be offset by wire rope pulling. Since the tension in that case is 10,000 N (see the above formula (2)), the full length variable steel material reduces the tension burden of the wire rope by 10,000-6,280 = 3,720 N. It can also be seen that the variable length steel avoids excessive tension in the wire rope.

  A more specific example of not using variable length steel is described below. If a tension of 2,000 N is applied to a wire rope that has been thermally expanded by 15 millimeters in the summer, the wire rope will be stretched to 30,000 millimeters with an extension of 18 millimeters plus 3 millimeters. That is, the free state length in summer is 29,997 millimeters. Since it shrinks by 15 millimeters in winter, it has a free state length of 29,982 millimeters. If this is to be made 30,000 millimeters without using a variable length steel, it will need to be stretched by 18 millimeters. The tension of 12,000 N is applied. If a steel with a variable length is used, 6,280N is sufficient as described above, and a higher tension is applied to the wire rope by 5,720N. Not only does the burden on the wire rope increase, but the labor to apply tension to the wire rope also becomes serious. It can be seen how the adoption of the full length variable steel material produces the tension relaxation action and the tension reduction labor reduction effect.

By the way, Table 2 shows the spring, summer, and autumn tensions obtained in the same manner as described above using a variable length steel material when the tension was increased by 1,000 N in winter.

  By the way, the total of the wire rope elongation and the string length of the variable length steel material is shown in Table 1 above with respect to the magnitude of the tension, and when it is multiplied by 6,000 N in the fall, the wire rope is between the anchors. Assume that the distance is 30 meters. Now, suppose that the tension of this wire rope dropped to 4,714N due to the weathering of rocks, etc., and that was autumn. From Table 2, a tension of 7,000 N is still exerted in winter and a tension of 2,714 N is still exerted in summer, and this wire rope does not lose the minimum set tension of 2,000 N.

  However, if the tension dropped to 4,000 N in winter, the tension is lower than the above-mentioned 4,290 N, so the tension becomes zero in summer. Therefore, it is understood that selecting the applied tension at the time of laying is also an extremely important design factor in consideration of the occurrence of the amount of loosening over time. Taking this into consideration, the tension needs to be 3,714 N (≈0.4 ton) in order to maintain the minimum set tension of 2,000 N even if the tension drops by 1,714 N in summer. . At this time, the winter tension is 8,000 N (≈0.8 tons) from Table 2. Conversely, it teaches that 8,000 N tension should be applied in winter construction.

  Although the target is different from the above-mentioned rock fall protection work, it is assumed that the tension of 4,000 N has now reached 6,000 N for some reason with a tension of 4,000 N acting on the wire rope. Although detailed explanation is omitted, such a case occurs, for example, in a pocket type rock fall protection net work. The sum of the stretch of the rope at 6,000 N and the stretch of the string is 21.0 millimeters, so it is 7 millimeters longer than 14.0 millimeters at 4,000 N, that is, the rope is 9.00-6. The string is extended by 0.000 = 3.00 millimeters and the string is extended by 12.00-8.00 = 4.00 millimeters, which means that a tension of 6,000 N is required. This is because if the total elongation of 21.0 millimeters described above is to be achieved with a 30-meter wire rope without a variable length steel, the wire rope must withstand a tension of 10,500 N from Table 1. . It is understood in this example that the burden of the wire rope is greatly reduced by adopting the variable length steel material.

  Next, a procedure for laying a wire rope will be described. First, as shown in FIG. 7B, the full length variable steel material 15 is arranged in the middle of the wire rope 1, and the rope is bound by the locking tool 22 so as not to be separated from the steel material. At this time, there is no problem even if a relative displacement in the longitudinal direction occurs between the wire rope and the full length variable steel material. On the other hand, it can be said that it is preferable that the deviation can occur. However, the variable length steel material 15 and the wire rope 1 in a portion along the variable length steel material are arranged in accordance with the wire along the variable length steel material no matter how it bends. The length of the rope on the variable length steel is unchanged. Even if there is a difference of half and half in the coefficient of thermal expansion, if the chord length is 50 centimeters, for example, the difference in the amount of thermal expansion is at most 0.13 millimeters according to the equation (1) above, It does not affect the whole system.

  After the wire rope 1 is laid along the variable length steel member 15, the ground unfixed end of the wire rope is attached to the bar-shaped anchor 3 or the load distribution surface storage type anchor 4 and is wound on the ground (not shown). . That is, the operation of causing the wire rope 1 to run along the variable length steel member 15 is left to the operator to determine whether one end of the wire rope is fixed and the other end is unfixed or both ends are unfixed. Because. The pressing portion 13 is seated on the load distribution plate 8 by a moment around the fulcrum portion generated only by mooring the rope end to the attachment portion 12.

  And when pulling the end part of the wire rope 1 and applying the tension, in the laying in the summer, a tension is applied so that the chord length is larger than the free state length of the full length variable steel material 15. When laying in winter, the string length is applied with a tension that is longer than the string length during wire rope laying in summer. In laying in the middle of spring or autumn, tension is applied so that the string length is longer than the string length when laying the wire rope in summer and shorter than the string length when laying the wire rope in winter. More specifically, in winter laying, a tension that can produce a state in which the minimum set tension can be exerted even when thermal expansion expected in summer occurs is applied. That is, if the difference in thermal expansion is 15 millimeters, “rope elongation” + “string elongation” is multiplied by a tension of 15 millimeters with a 30,000 millimeter rope.

  Incidentally, traction for applying tension and mooring of the wire rope 1 may be performed as shown in FIGS. Hang the wire rope 1 on the attachment portion 12 as shown in (a), take out the rope from the attachment portion, sandwich the rope with the clamper 1c just before reaching the attachment portion, and use the chain block etc. not shown in the direction of the arrow 17 Pull to. When a predetermined tension is applied, the wire rope is tied as shown in (b), and the unnecessary rope is removed as shown in (c) if necessary. As shown in FIG. 9, it does not matter whether the tension is obtained on the load-dispersing surface anchor 4 side or the rod-like anchor 3 side in FIG. For the fixing, a known winding grip 18 shown in FIG.

  Here, the details of the full length variable steel material used in the present invention will be described from the example of the flat steel plate 21 shown in FIG. As shown in FIG. 10, the wire rope 1 is bound to the steel plate by placing the wire rope along the back surface of the steel plate bent into an arcuate shape and preventing separation by a locking tool 22 such as a U-bolt at both ends of the string. Is done by. I have already mentioned many times that it is bent into a bow shape that generates elasticity in the direction of constantly reducing the chord length. If such a flat steel plate is used, the rope along the steel plate surface and the separation prevention by the locking tool can be achieved by a simple operation. If it becomes easy to bind the wire rope 1 to the steel plate, the power work on the sloping ground where the working environment is severe is greatly reduced.

  As the locking tool, instead of the U-bolt 22A shown in FIG. 11A, an Ω-shaped metal fitting 22B shown in FIG. 11B may be used. Further, as shown in (c), a bending protrusion 22C obtained by cutting and raising a part of a flat steel plate may exhibit a hook function. In this case, as shown in (d), if the hooks are alternately turned to the left and right with the directions of the hooks reversed, it is difficult for the rope to come off at one end.

  As mentioned above, the relative displacement in the longitudinal direction between the wire rope and the variable length steel has no effect on the tension adjustment, so the operation of moving the rope along the variable length steel is light. . Due to the presence of the full length variable steel material, the rope slippage in the cross anchor clip 1b (see FIG. 1) is not a big problem. The rope slip complete prevention operation which has been performed recently for the purpose of preventing the loosening of the wire rope is not always necessary. The avoidance of the clip fastening operation or the reduction in the number of operations frees or remarkably reduces heavy labor in a harsh working environment with a poor foothold, and contributes to a reduction in the number of steps for installing a rockfall protection work.

Next, the details of the two-action point type lever 7 of the above-described load distribution surface anchor 4 will be described. As shown in FIG. 12 (a), a U-shaped portion formed by folding a steel plate 7A cut into a substantially butterfly shape in two is used as a base (the fulcrum portion 14 shown in FIG. 5 (b)). And a portion 23 that fits the head portion of the pile 11 and connects the base portion and the attachment portion 12, as shown in FIGS. 13A and 13C, the attachment portion 12. And the line 24 connecting the pressing portion 13 is set to approximately 90 degrees. This way, the load from the pressing portion to the load distribution plate 8 is to be introduced with less mechanical losses (T in FIG. ... rope tension, T _V ... pressing force direction component, T _E ... drawing direction component). Note that the two-action point type lever 7 manufactured by substantially butterfly-shaped planing realizes a reduction in the number of parts and contributes to a reduction in cost compared to the alternatives described later.

  By the way, the wire rope 1 extending from the attachment portion 12 toward the valley or mountain or horizontally, as shown in FIGS. 13A and 13C, with respect to the line 23 connecting the fulcrum portion 14 and the attachment portion 12. Consider making an angle of 45 degrees or more. As a result, 70% or more of the rope tension can be loaded on the load distribution plate 8, and the load exerted on the anchor is as small as possible than the case shown in FIGS. 13B and 13D of less than 45 degrees. To reduce anchorage and promote anchor stability.

  As an alternative lever of the two-action point type lever, the one shown in FIG. This is not much different from (a) of FIG. 5 as long as (c) in the form assembled as the load distribution surface anchor 4 is seen. However, the fulcrum part 14 has the same bolt type as that of the attachment part 12 so that the swinging at the fulcrum part becomes smoother. As shown in (b), when the collar 27 is sandwiched between the bolt 25 and the nut 26, the collar softens the friction between the wire rope 1 and the bolt at the mounting portion 12, and the space through which the pile 11 passes at the fulcrum portion 14. Functions as a spacer to ensure

  Many things have been described above. According to this wire rope tension maintenance method, rock-like bar anchors are used in places where the natural ground is rocky, and load distribution surface is used in places where it is earthy or gravel. Deposit anchors are used. Therefore, the wire rope end is firmly fixed, and a large tension can be applied to the wire rope stretched around the anchor. Since the variable length steel material that exerts elasticity in the direction of constantly reducing the chord length or wavelength is laid along the middle of the wire rope, the total length of the rope is constant due to the change in the bending length of the variable length steel material due to the thermal expansion and contraction of the wire rope. It is automatically adjusted to maintain the desired tension while keeping

  When laying a wire rope, apply a tension that makes the chord length or wavelength longer than the free length of the variable length steel material in summer, and in winter, apply a tension that makes the chord length or wavelength longer than those when laying the wire rope in summer. Try to hang. As a result, the wire rope can be kept in tension during the summer and winter as long as the tension of a certain magnitude or more is applied in winter. And since the difference in tension is reduced to about half that when not using a variable length steel material, the load acting on the anchor does not become extremely different throughout the year.

  Since the alternating load of the load on the anchor placing hole wall is small and weakened, the anchor and the ground are kept in close contact with each other, and the standing state can be easily stabilized over a long period of time. By the way, because the wire rope is only laid along the flat steel plate, even when the looseness of the wire rope is found in the facility that is already functioning as a rockfall guard, both ends of the rope are fixed, There is an advantage that it is easy to interpose.

  By the way, in the rock fall protection work 2 shown in FIG. 1, the wire rope 1K is also laid on the diagonal line of the rope frame formed by the wire ropes 1T and 1Y laid vertically and horizontally. If the diagonal rope 1K is introduced as a main or auxiliary wire rope in this way, the amount of rope stretched per area increases, but it becomes dense, and it is easy to hold not only large rocks but also gravel. If the tension of the diagonal rope is adjusted automatically, the ground cover effect by rock fall protection will be greatly enhanced. Since this diagonal rope has various lengths, some of the intervening full length variable steel materials may not be in accordance with Table 1, but in that case, the total length of the corrugation described below is used. What is necessary is just to make it correspond with a variable steel material.

The above is an example of a steel material that is bent into a bow shape and generates elastic force in a direction that always reduces the chord length. However, the corrugated flat steel plate 21A shown in FIG. 14 that is bent into a waveform and generates a resilience in the direction of constantly reducing the wavelength may be used. (A) is in the form of a wave of one pitch and a half, and to refer to the horizontal projection length of 1 pitch half the wavelength, which is the direction of the spring to reduce constantly so that free state length of L _WA Demonstrate power. Speaking of strength, it is like a string of three strings with the above strings as half pitch. A table in which the column of string elongation in Table 1 is tripled may be applied. Of course, it goes without saying that the growth can be changed by changing the EI.

  By the way, even if a part of the tension does not follow as shown in (b) when tension is applied in the state of FIG. 14 (a), there is no problem as long as this configuration is maintained thereafter. If it is desired to always follow the flat steel plate, another or two locking tools 22 may be added at the center as shown in (c) (one figure is added). In addition, when three arcuate flat steel plates 21 are connected, for example, they may be arranged in an opposite posture so as to alternately follow the lower surface and the upper surface of the wire rope 1 as shown in (d). At this time, the flat steel plates are connected to each other by sandwiching the wire rope with U-bolts 22A having slightly longer legs.

  In this way, a substantially corrugated full-length variable steel material can be formed. It becomes easy to change the stretch absorbency of the rope depending on the number of flat steel plates, and it becomes a versatile steel with variable length. By the way, because it is a flat steel plate, it can be inserted into the wire rope after it has been found loose by a rockfall guard that has already been completed. Even an old rockfall protection work can be regenerated with a simple operation. Incidentally, as shown in FIGS. 15A and 15B, the wire rope 1 can be along the opposite surface (for example, the lower surface) of the flat steel plate, or along both surfaces as shown in FIG. 15C. In the latter case, the load application range can be increased, and conversely, a thin rope can be introduced.

  In the rock fall protection work using the corrugated flat steel plate 21A as the variable length steel material 15 as described above, when applying tension by pulling the end of the wire rope, in the summer laying, the wavelength can be freely adjusted. Apply tension that is greater than the state length. In winter laying, apply a tension that makes the wavelength longer than the wavelength used in summer wire rope laying. Needless to say, a tension that is shorter than the wavelength is applied.

  If the above operation is expressed without sticking to rock fall protection work, it will be as follows. In addition, since it is the range understood by the description so far, illustration is abbreviate | omitted. Applying tension that makes the chord length or wavelength larger than the free length of the variable length steel, for example, even if the wire rope loosens due to rock settling or displacement, the elastic length of the variable length steel depends on the residual tension of the rope. Alternatively, the wavelength is reduced. Increasing the bend of the rope along the length-variable steel material substantially pulls the rope, and all or part of the looseness of the rope is absorbed to restore the rope tension.

  By the way, the steel rod 21B can be used as the variable length steel material in place of the flat steel plate. As shown in FIG. 16, a round bar or a square bar is sufficient (illustration is a round bar), but hooks 22D formed by bending the ends of steel bars are provided at both ends of the string. Then, as shown in FIG. 17, the wire rope 1 extends along the steel bar only at the bent portion, and the wire rope is bound only by the hook 22D. I try to prevent the departure from. Such an operation is performed at a stage where at least one end of the wire rope is not fixed to the anchor. Although the rope is strong, the rope is pressed only once or about once and a half once around the steel rod. Because it can be placed along the steel rod, the burden is surprisingly small. The burden on the steel rod along the rope is significantly smaller than the amount of high-torque fastening work at many locations on the cross-anchor clip. This will improve work efficiency and suppress the quality of materials.

  FIG. 18 shows a corrugated steel bar 21C. There are hooks 22D formed by bending at both ends of the wave. (B) is the reverse of (a), but there is no problem. Actually, as in the case of the flat steel plate described above, the posture of the variable length steel material can be changed depending on the mounting operation, the undulation or twisting of the rope, etc., so that the vertical movement in the mounting state does not matter.

FIG. 18C and FIG. 17 show a state in which both ends are extended by ΔL _K by applying tension to the front steel rods in the free state. Chord depth of the steel rod in a state of even a tensioned in either, unwinding the rope by the height of the wave is reduced, is depicted as offset the [Delta] L _K. By the way, Figure 1 was an example of hard and soft rocks, but only rock-like anchors are used as anchors in rocky rocks, and load distribution is used in rocky and gravelly rocks. Needless to say, it will be only the surface deposit type anchor.

  DESCRIPTION OF SYMBOLS 1 ... Wire rope, 1K ... Diagonal rope, 1T ... Vertical rope, 1Y ... Horizontal rope, 1b ... Cross anchor clip, 2 ... Falling rock protection work, 2a ... Floating stone, 2b ... Rock, 3 ... Bar anchor (Rocky anchor ) 4 ... Load-dispersing surface anchors, 5 ... Bedrock, 6 ... Sediment / gravel surface (sediment / gravel surface), 7 ... Dual action lever, 8 ... Load distribution plate, 11 ... Pile, 12 ... mounting part, 13 ... pressing part, 14 ... fulcrum part, 15 ... full length variable steel, 21 ... arched flat steel sheet, 21A ... corrugated flat steel sheet, 21B ... arched steel bar, 21C ... corrugated steel bar, 22 ... engagement Stopper, 22D ... Hook.

Claims (7)

In order to prevent the fall of rocks and rocks, in the rope tension method in the rock fall protection work that lays the wire rope at least vertically and horizontally and holds the natural ground,
As an anchor to stand on natural ground to hold the end of the wire rope,
In the place where the natural rock is rocky, a rod-shaped anchor standing on the rock and demonstrating strong fall prevention resistance is used,
In places where the natural ground is earthy or gravelly, it is supported by the head located on the surface of the pile so that it can be pivoted up and down and moored at the end of the rope away from the fulcrum And a two-action point type lever having a pressing portion provided at a position away from the fulcrum portion so as to exert a force on the ground surface due to a moment generated by a rope tension acting on the attachment portion, and earth and sand A load distribution surface anchor that provides a load distribution plate that covers the material surface layer and receives the load from the pressing portion at a low surface pressure, and exhibits a fall prevention resistance is used.
As a wire rope tension adjuster,
Variable length steel material is used that is bent into a bow or corrugation, generates elastic force in a direction that always reduces the chord length or wavelength, and runs along the wire rope.
When laying a wire rope,
Arrange the full length variable steel material in the middle of the wire rope and bind the rope so as not to separate from the steel material,
Attach the unfixed end of the wire rope to the bar-shaped anchor or load-dispersing surface-deposited anchor and place it on the ground.
Due to the moment around the fulcrum part generated by mooring the rope end to the attachment part, the pressing part is seated on the load distribution plate,
When pulling the wire rope and applying tension,
In laying in the summer, apply a tension that makes the chord length or wavelength larger than the free state length of the full length variable steel,
In winter laying, apply a tension that makes the chord length or wavelength longer than the chord length or wavelength when laying a wire rope in summer.
In spring / autumn laying, the string length or wavelength is applied with tension that is longer than the length or wavelength of the wire rope in summer and shorter than the length or wavelength of the wire rope in winter.
When the wire rope is thermally expanded and the tension is reduced, the elastic force of the full length variable steel is reduced to the chord length or wavelength corresponding to the remaining tension of the rope, and the portion of the rope bent along the full length variable steel is chorded. Reducing the length substantially pulls the rope, absorbs a part of the amount of rope expansion due to thermal expansion, but leaves tension on the rope,
When the wire rope heat shrinks and the tension increases, the elastic force of the variable length steel material expands to the chord length or wavelength according to the increased tension of the rope, and the string of the bent part of the rope along the variable length steel material A wire rope in rock fall protection work, which is able to avoid excessive tension on the rope while substantially extending the rope by extending the length and absorbing part of the shrinkage of the rope due to heat shrinkage Tension holding method. When applying tension by pulling the wire rope, instead of the operation for preparing the laying time and the heat shrinkage of the rope,
Even if the tension of the chord length or wavelength is greater than the free length of the variable length steel, the elastic force of the variable length steel reduces the chord length or wavelength according to the residual tension of the rope even if the wire rope is loosened in that state. The rope is substantially pulled up by increasing the bending of the rope along the length-variable steel material, and the rope tension is absorbed and the rope tension can be recovered. The method for maintaining the tension of the wire rope in the rock fall protection work described in Item 1.   The wire in the rock fall protection work according to claim 1 or 2, wherein a wire rope is also laid on the diagonal line of the rope frame formed by the wire rope laid vertically and horizontally in the rock fall protection work. Rope tension retention method.   The full length variable steel material is a flat steel plate. 4. The method for maintaining tension of a wire rope in a rock fall protection work according to any one of claims 1 to 3, wherein separation is prevented.   The length-variable steel material is a steel rod, and the wire rope is bound to the steel rod by winding the wire rope around the bow or corrugated portion and bending the end of the steel rod at both ends of the string or corrugation. The method for maintaining the tension of the wire rope in the rock fall protection work according to any one of claims 1 to 3, wherein the wire rope is locked to a hook formed to prevent separation from the steel rod. .   In the dual acting point lever of the load distribution surface anchor, the line connecting the mounting portion and the pressing portion is substantially perpendicular to the line connecting the fulcrum portion to be fitted to the head and the mounting portion. The wire rope tension maintaining method in the rock fall protection work according to any one of claims 1 to 5, wherein the wire rope tension maintaining method is provided.   7. The wire rope extending from the attachment portion forms an angle of 45 degrees or more with respect to a line connecting the fulcrum portion and the attachment portion. 8. Method for maintaining tension of wire rope in a fallen rock guard.