Cho, Seong-ho (Chonggu Apt, Jeonmin-dong Yuseong-gu, 305-729 Daejeon, 101-1105, KR)
Cha, Dong-hwan (Hanmaeul Apt, Songgang-dong Yuseong-gu, 305-756 Daejeon, 112-1401, KR)
Choi, Se-whan (Dungji Apt, Dunsan 2-dong Seo-gu, 302-734 Daejeon, 101-1002, KR)
Yun, Kwang-jung (201 Yuseong Yeollip, 526-24 Bongmyeong-dong Yuseong-gu, 305-301 Daejeon, KR)
Cho, Seong-ho (Chonggu Apt, Jeonmin-dong Yuseong-gu, 305-729 Daejeon, 101-1105, KR)
Cha, Dong-hwan (Hanmaeul Apt, Songgang-dong Yuseong-gu, 305-756 Daejeon, 112-1401, KR)
Choi, Se-whan (Dungji Apt, Dunsan 2-dong Seo-gu, 302-734 Daejeon, 101-1002, KR)
| 1. | A geogrid comprising : a plurality of longitudinal fiberreinforced polymer strips arranged longitudinally in parallel at regular intervals, the longitudinal fiberreinforced polymer strip being configured so that a strip is reinforced with a fiber in a thermoplastic polymer resin; and a plurality of lateral fiberreinforced polymer strips arranged laterally in parallel at regular intervals, the lateral fiberreinforced polymer strip being configured so that a strip is reinforced with a fiber in a thermoplastic polymer resin, wherein each of the longitudinal fiberreinforced polymer strips has at least one first contact point which is crossed with one of the lateral fiberreinforced polymer strips on an upper surface thereof, and at least one second contact point which is crossed with another one of the lateral fiberreinforced polymer strips on a lower surface thereof, wherein the thermoplastic polymer resin of the longitudinal fiberreinforced polymer strip and the thermoplastic polymer resin of the lateral fiberreinforced polymer strip are welded and fixed at the contact points. |
| 2. | A geogrid according to claim 1, wherein each of the longitudinal fiberreinforced polymer strips is crossed with each of the lateral fiberreinforced polymer strips so that the first contact point and the second contact point are positioned in turns. |
| 3. | A geogrid according to claim 1, wherein at least one of the longitudinal fiberreinforced polymer strips is crossed with the lateral fiberreinforced polymer strip so that at least two second contact points are positioned between the first contact points. |
| 4. | A geogrid according to claim 1, wherein the thermoplastic polymer resin of the longitudinal and lateral fiberreinforced polymer strips is one selected from the group consisting of polyolefin resin having a melt index (MI) of 1 to 35, polyethylene terephthalate having an intrinsic viscosity (IV) of 0.64 to 1.0, polyamides, polyacrylates, polyacrylonitrile, polycarbonates, polyvinylchloride, polystyrene, polybutadiene, and their mixtures. |
| 5. | A geogrid according to claim 1, wherein the fiber of the longitudinal and lateral fiberreinforced polymer strips is an independent one selected from the group consisting of polyester fiber, glass fiber, aramid fiber, carbon fiber, basalt fiber, stainless steel fiber, copper fiber and amorphous metal fiber, or their doubled and/or twisted fiber. |
| 6. | A geogrid according to claim 1, wherein an entire cross section of the fiber of the longitudinal and lateral fiberreinforced polymer strips is 20 to 80% of an entire cross section of the fiberreinforced polymer strip. |
| 7. | 5 7. |
| 8. | A geogrid according to claim 1, wherein the longitudinal and lateral fiberreinforced polymer strips respectively have a rectangular cross section having a width of 2 to 30 mm and a thickness of 1 to 10 mm. |
| 9. | A geogrid according to claim 1, 10 wherein the longitudinal and lateral fiberreinforced polymer strips respectively have a circular cross section having a diameter of 2 to 20 mm. |
| 10. | A geogrid according to claim 1, wherein the plurality of longitudinal fiberreinforced polymer strips are arranged in parallel 15 at regular intervals of 10 to 100 mm on the basis of a center line of each longitudinal fiberreinforced polymer strip, and wherein the lateral fiberreinforced polymer strips are arranged in parallel at regular intervals of 10 to 100 mm on the basis of a center line of each lateral fiberreinforced polymer strip. |
| 11. | 20 10. A geogrid according to claim 1, wherein the plurality of longitudinal fiberreinforced polymer strips are crossed with the lateral fiberreinforced polymer strips at an angle of 80 to 100°. |
| 12. | 1 I. A method for producing a geogrid comprising: (a) arranging a plurality of longitudinal fiberreinforced polymer strips, each of which is configured so that a strip is reinforced with a fiber a thermoplastic polymer resin, in parallel ; (b) bending the plurality of longitudinal fiberreinforced polymer strips to form ridges and valleys in turns so that the ridge and the valley formed in at least one of the longitudinal fiberreinforced polymer strips are corresponding to the valley and the ridge formed in at least another one of the longitudinal fiberreinforced polymer strips ; (c) inserting at least one lateral fiberreinforced polymer strip, which is configured so that a strip is reinforced with a fiber in a thermoplastic polymer resin, through a space between the corresponding ridge (or, valley) and valley (or, ridge) of the longitudinal fiberreinforced polymer strips in order to make the lateral fiberreinforced polymer strip be crossed with the longitudinal fiberreinforced polymer strips ; and (d) adhering the longitudinal and lateral fiberreinforced polymer strips at contact points at which the longitudinal and lateral fiberreinforced polymer strips are crossed. |
| 13. | 12 A method for producing a geogrid comprising: (a) bending a plurality of longitudinal fiberreinforced polymer strips to form ridges and valleys in turns so that the ridge and the valley formed in at least one of the longitudinal fiberreinforced polymer strips are corresponding to the valley and the ridge formed in at least another one of the longitudinal fiberreinforced polymer strips ; (b) inserting at least one lateral fiberreinforced polymer strip through a space between the corresponding ridge (or, valley) and valley (or, ridge) of the longitudinal fiberreinforced polymer strips so as to form a first contact point at which a lower surface of the longitudinal fiberreinforced polymer strip is crossed with an upper surface of the lateral fiberreinforced polymer surface and a second contact point at which an upper surface of the longitudinal fiberreinforced polymer strip is crossed with a lower surface of the lateral fiberreinforced polymer strip ; and (c) adhering the longitudinal and lateral fiberreinforced polymer strips to each other at the first and second contact points. |
| 14. | 13 A method for producing a geogrid according to claim 12, wherein the first and second contact points are formed in turns in at least one of the longitudinal fiberreinforced polymer strips. |
| 15. | 14 A method for producing a geogrid according to claim 12 or 13, wherein the at least one of the longitudinal fiberreinforced polymer strips is a n°'strip, and the at least another one of the longitudinal fiberreinforced polymer strips is a n+1fl sttip. |
| 16. | 15 A method for producing a geogrid according to claim 12, wherein at least two second contact points are formed between the first contact points in at least one of the longitudinal fiberreinforced polymer strips. |
| 17. | 16 A method for producing a geogrid according to claim 12, wherein, in the step (c), the thermoplastic polymer resins of the longitudinal and lateral fiberreinforced polymer strips are welded and fixed to each other at the first and second contact points. |
| 18. | 17 A method for producing a geogrid according to claim 16, wherein the first and second contact points are formed by vibration welding, ultrasonic friction welding, or heating adhesion. |
| 19. | 18 A method for producing a geogrid according to claim 17, wherein one of the longitudinal and lateral fiberreinforced polymer strips positioned at the first or second contact points is fixed, while the other is vibrated so as to melt and adhere the thermoplastic polymer resins on opposite surfaces thereof. |
| 20. | 19 A method for producing a geogrid according to claim 12, wherein the first and second contact points are adhered step by step. |
| 21. | 20 A method for producing a geogrid with fiberreinforced polymer strips, each of which is configured so that a strip is reinforced with a fiber in a thermoplastic polymer resin, by using a device including a strip arranging means, which has upper and lower plates for oppositely moving at an interval and first and second bending members alternatively protruded on opposed surfaces of the upper and lower plates, the method comprising: (a) supplying a plurality of longitudinal fiberreinforced polymer strips in a row between the upper and lower plates along the first and second bending members; (b) bending the longitudinal fiberreinforced polymer strip by moving the upper and lower plates to approach to each other so that a portion of the longitudinal fiberreinforced polymer strip pressed by the first bending member becomes a valley, while a portion of the longitudinal fiberreinforced polymer strip pressed by the second bending member becomes a ridge; (c) inserting a lateral fiberreinforced polymer strip through the corresponding ridge (or, valley) and valley (or, ridge) of the plurality of longitudinal fiberreinforced polymer strips so that the lateral fiberreinforced polymer strip is crossed with the longitudinal fiberreinforced polymer strips; and (d) adhering contact points at which the longitudinal and lateral fiberreinforced polymer strips are crossed to each other. |
| 22. | 21 A method for producing a geogrid according to claim 20, wherein support grooves are formed on the first and second bending members along the longitudinal fiberreinforced polymer strips so that the longitudinal fiberreinforced polymer strips are not deviated when being pressed. |
| 23. | 22 A method for producing a geogrid according to claim 20, wherein through holes are formed in the first and second bending members respectively so that the lateral fiberreinforced polymer strip is inserted to pass through. |
| 24. | 23 A method for producing a geogrid according to claim 20, wherein, in the step (d), the contact points are adhered by means of a welding unit which includes: upper and lower jigs which oppositely moves at an interval ; and a plurality of support holders protruded on opposite surfaces of the upper and lower jigs so as to be opposed with each other. |
| 25. | 24 A method for producing a geogrid according to claim 23, wherein one of the longitudinal and lateral polymer strips crossed at the contact point is pressed and supported by one of the opposite support holders, and wherein the other of the longitudinal and lateral polymer strips crossed at the contact point is pressed and vibrated by the other of the opposite support holders so that the contact point is adhered. |
| 26. | 25 A method for producing a geogrid according to claim 24, wherein, in the step (c), a first contact point at which a lower surface of the longitudinal fiberreinforced polymer strip is crossed with an upper surface of the lateral fiberreinforced polymer strip and a second contact point at which an upper surface of the longitudinal fiberreinforced polymer strip is crossed with a lower surface of the lateral fiberreinforced polymer strip are formed, and wherein the first and second contact points are adhered step by step with the use of the welding unit. |
5 According to the present invention, it is possible to produce a geogrid with various woven structures by changing positions of the bending members 80 and 90 of the upper and lower plates 51 and 52. FIGs. l0ato 1Od show examples of such a geogrid.
As shown in FIG. 10a, if two first bending members 80'are successively positioned between the second bending members 90'along the longitudinal direction on the opposite surfaces 10 of the upper and lower plates 51'and 52', the longitudinal and lateral polymer strips are arranged so that two second contact points C2 are positioned between the first contact points Cl as shown in FIG. lOb. In other words, in this case, it may be understood that two lateral polymer strips are inserted into one valley (or, one ridge) of the longitudinal polymer strip.
In addition, if three first bending members 80"are successively positioned between the 15 second bending members 90"on the opposite surfaces of the upper and lower plates 51"and 52"as shown in FIG. l Oc, one longitudinal polymer strip 1 has three second contact points C2 between the first contact points Cl as shown in FIG. 10d. That is to say, this may be understood that three lateral polymer strips are inserted into one valley (or, one ridge) of the longitudinal polymer strip.
Though it is described in this embodiment regarding a ni longitudinal polymer strip and an 20 adjacent n+1'§l longitudinal polymer strip, the same principle may be applied to other longitudinal
polymer strips which are not adjacent to each other.
The longitudinal and lateral polymer strips 1 and 2 arranged as mentioned above are then transferred to the welding unit 60 so that the contact points Cl and C2 are welded. First, the upper and lower jigs 63 and 64 shown in FIG. 7a approaches each other at the first welder 61 a to press the polymer strip array interposed between the jigs 63 and 64. At this time, the first holders 63a and 64a formed on the opposite surfaces of the upper and lower jigs 63 and 64 press and support the first contact points Cl of the polymer strip array. More specifically, the support 63a of the upper jig 63 is contacted with the upper surface of the longitudinal polymer strip 1, while the support holder 64a of the lower jig 64 is contacted with the lower surface of the lateral polymer strip 2. At this time, the ends of the support holders 63a and 64a have rough surfaces so as to be contacted with the surfaces of the polymer strip without sliding.
In this state, if the upper jig 63 is vibrated in a direction perpendicular to the length of the longitudinal polymer strip 1, for example right and left directions, with the lower jig 64 being fixed, the polymer resin 110 of the strip is melt and the first contact points Cl become adhered (step S340).
At this time, the vibration preferably has the frequency of 60 to 300 Hz and the amplitude of 0.3 to 1.8 mm so that the polymer resin is melt for a short time without damaging the reinforcing fiber 100 in the polymer resin.
If the first contact points Cl are adhered as mentioned above, the longitudinal and lateral polymer strip array is transferred again to the second welder 62 for vibration welding of the second contact points C2 (step S350).
In the second welder 62, the second support holders 65a and 66a of the upper and lower jigs 65 and 66 are contacted with the second contact points C2 of the longitudinal and lateral polymer strip array. At this time, in this embodiment, the support holder 65a is contacted with the upper surface of the lateral polymer strip 2, while the support holder 66a is contacted with the lower 5 surface of the longitudinal polymer strip 1.
In this state, the upper jig 65 is fixed and the lower jig 66 is vibrated in a direction perpendicular to the length of the longitudinal strip 1, for example right and left directions, so as to perform the adhesion in the same way as the former procedure.
Though it is illustrated in the description and drawings that the first contact points Cl and 10 the second contact points C2 are separately vibration-welded, it should be understood that the present invention is not limited to that case but various modifications may be applied thereto. For example, the first contact points C ; and the second contact points C2 may be adhered using only one welder. In this case, the first contact points C, is firstly adhered and then the strip array is wound around the winder, and then the strip array is again released into the welder. At this time, 15 if the array is turned over for inversion of the upper and lower surfaces, the second contact points C2 may be adhered. Furthermore, the contact points of the polymer strip may be adhered using the ultrasonic frictional welding or the heating, or hot-melt instead of the vibration welding.
After completing the adhesion, the geogrid is wound around the winder 71 by a regular length through the pulling unit 70. Preferably, the fiber-reinforced geogrid product has a length of 20 25 to 200 m for the convenience of treatment on the working spot.
Though the making process of the fiber-reinforced polymer strip and the producing process of the geogrid are separately described in this embodiment, these processes may be perfonned successively.
Hereinafter, preferred embodiments of the present invention will be described in detail.
5 Prior to the description, it should be understood that the embodiments according to the present invention may be changed in various ways, and the present invention should not be interpreted to be limited to the following embodiments. The embodiments of the present invention are intended just for giving better perfect explanation to those ordinary skilled in the art.
The properties of the geogrid according to the embodiments are measured using the 10 following tests.
Wide-width Tensile Strength Test: ASTM D 4595 A sample having a width of 20 cm is fixed between clamps attached on and below the transformation-controlling tensile strength tester and then tensioned at a rate of 10 3%/min, and 15 then tensile strength and tensile elongation are measured at the breaking point due to tensile transformation. In case a glass fiber is used as a reinforcing fiber, the tensile strength (LASE 2%) when the tensile strain is 2% is separately recorded, while, in case a polyester high-strength fiber is used as a reinforcing fiber, the tensile strength (LASE 5%) when the tensile strain is 5% is separately recorded.
20 Creep Test: ASTM D 5262 The creep test evaluates deformation behavior of the geogrid when a constant tensile load is applied continuously at a constant temperature condition of21 2°C so as to determine a tensile strength reduction factor due to the creep, which is considered in design. In this experiment, 45% 5 load of the maximum tensile strength of the geogrid sample is applied to the sample, and the creep strain is measured after 1,000 hours.
Assessment of Installation Damage : ASTM D 5818 A base subgrade is treated in the same way as the actual structure building, then a geogrid 10 sample of at least 10 m2 is installed, a fill material is installed thereon, and then they are compacted in the same way as the actual structure building. As for the fill material, aggregate having a size of at most 20 mm is compacted in a thickness of 30 cm, and then the geogrid sample is installed and the same fill material is installed again thereon in a thickness of 30 cm, and then a vibration roller of l Oton capacity is used for four time reciprocating compaction.
15 After the compaction, the compacted aggregation is removed not to damage the geogrid so that the geogrid sample is exhumed, and then a tensile strength is tested for the exhumed sample to calculate a strength reduction rate in comparison to the tensile strength of the original sample.
Test for Shape Stability 20 Installation and compaction are conducted in the same way as the assessment of
installation damage, and then contact points of the longitudinal and lateral strips are observed. If the number of separated contact points is more than 20%, it is evaluated as"inferior", if the number of separated contact points is in the range of 10 to 20%, it is evaluated as"nonnal", while the number of separated contact points is less than 10%, it is evaluated as"superior".
Evaluation of Pullout Test Soil is filled in a soil box having a length of 140 cm, a width of 60 cm, and a height of 60 cm, and the geogrid is installed in the soil. At this time, the geogrid sample is connected to a drawing device through a slit of 2.5 cm. In addition, a rubber membrane is mounted to the upper portion of the soil box so as to apply a uniform vertical load to the soil box by means of air pressure.
Then, with changing the vertical load from 0. 3 to 1.2 kg/cm2 (3 to 12 kN/cm2), an interaction coefficient Ci showing a frictional force between the geogrid and the soil is evaluated by analyzing the pullout displacement of the geogrid at the maximum pullout force, with a pullout displacement rate of 0.1 cm/min.
Embodiment 1 A polyester high-tenacity fiber bundle of 48000 deniers is passed through a nipple having a rectangular section and through a rectangular die to make a longitudinal fiber-reinforced polymer strip having a section shown in (a) of FIG. 11 a with a width of 8.4 mm and a thickness of 2.3 mm In addition, a lateral fiber-reinforced polymer strip having the same section as the longitudinal
fiber-reinforced polymer strip with a width of 6. 3 mm and a thickness of 1. 5 mm is made with the use of polyester high-tenacity fiber bundle of 20000 deniers. Polypropylene having a melt index of 4 is used as a fhen-noplastic polymer resin. Then, the longitudinal fiber-reinforced polymer strips are arranged on the strip arranging unit so that a product width is 4 m and a distance between the strips is 40 mm, and then the lateral fiber-reinforced polymer strips are inserted at an interval of 50 mm to have an angle of 90° with the longitudinal strip, thereby making a lattice having a plain weave structure as shown in FIG. 1. Subsequently, the first welder welds contact points at which the longitudinal strip is positioned above the lateral strip, by vibrations having a frequency of 194 Hz and an amplitude of 0.5 mm. And then, the lattice is moved to the second welder so as to weld contact points at which the longitudinal strip is positioned below the lateral strip, by vibration having a frequency of 194 Hz and an amplitude of 0.5 mm, thereby making a geogrid. The number of ribs per unit length (ribs/m), a wide-width tensile strength (kN/m), LASE5% (kN/m), a tensile strain (%), a creep strain (%) and a strength reduction rate (%) under construction of the produced geogrid are shown in the following table 1, and an interactive coefficient in pullout and shape stability are shown in the following table 4.
Embodiment 2 Two polyester high-tenacity fiber bundles of 24000 deniers are passed through a two-hole nipple having a rectangular section and through a rectangular die to make a longitudinal fiber-reinforced polymer strip having a section shown in (b) of FIG. 1 la with a width of 8.4 mm
and a thickness of 2.3 mm. In addition, a lateral fiber-reinforced polymer strip having the same section as the longitudinal fiber-reinforced polymer strip with a width of 6.3 mm and a thickness of 1. 5 mm is made with the use of two polyester high-tenacity fiber bundles of 10000 deniers. Then, the strips are arranged in the same way as the first embodiment to produce a geog-id. The number of ribs per unit length (ribs/m), a wide-width tensile strength (kN/m), LASE5% (kN/m). a tensile strain (%), a creep strain (%) and a strength reduction rate (%) under construction of the produced geogrid are shown in the following table 1.
Embodiment 3 Three polyester high-tenacity fiber bundles of 16000 deniers are passed through a three-hole nipple having a rectangular section and through a rectangular die to make a longitudinal fiber-reinforced polymer strip having a section shown in (c) of FIG. 1 la with a width of 8.4 mm and a thickness of 2.3 mm. In addition, a lateral fiber-reinforced polymer strip having the same section as the longitudinal fiber-reinforced polymer strip with a width of 6.3 mm and a thickness of 1.5 mm is made with the use of four polyester high-tenacity fiber bundles of 5000 deniers. Then, the strips are arranged in the same way as the first embodiment to produce a geogrid. The number of ribs per unit length (ribs/m), a wide-width tensile strength (kN/m), LASE5% (kN/m), a tensile strain (%), a creep strain (%) and a strength reduction rate (%) under construction of the produced geogrid are shown in the following table 1.
Embodiment 4 Eight polyester high-tenacity fiber bundles of 3000 deniers are passed through a four-hole nipple having a rectangular section and through a rectangular die to make a longitudinal fiber-reinforced polymer strip having a section shown in (e) of FIG. 1 la with a width of 6.3 mm and a thickness of 1.5 mm. In addition, a lateral fiber-reinforced polymer strip having the same section as the longitudinal fiber-reinforced polymer strip with a width of 6. 3 mm and a thickness of 1.5 mm is made with the use of four polyester high-tenacity fiber bundles of 5000 deniers. Then, the strips are arranged in the same way as the first embodiment to produce a geogrid. The number of ribs per unit length (ribs/m), a wide-width tensile strength (kN/m), LASE5% (kN/m), a tensile strain (%), a creep strain (%) and a strength reduction rate (%) under construction of the produced geogrid are shown in the following table 1.
Embodiment 5 Twelve polyester high-tenacity fiber bundles of 3000 deniers are passed through a four-hole nipple having a rectangular section and through a rectangular die to make a longitudinal fiber-reinforced polymer strip having a section shown in (e) of FIG. 1 la with a width of 6. 8 mm and a thickness of 2.0 mm. In addition, a lateral fiber-reinforced polymer strip having the same section as the longitudinal fiber-reinforced polymer strip with a width of 6.3 mm and a thickness of 1.5 mm is made with the use of four polyester high-tenacity fiber bundles of 5000 deniers. Then, the strips are arranged in the same way as the first embodiment to produce a geogrid. The number
of ribs per unit length (ribs/m), a wide-width tensile strength (kN/m). LASE5% (kN/m), a tensile strain (%), a creep strain (%) and a strength reduction rate (%) under construction of the produced geogrid are shown in the following table 1.
Embodiment 6 Two polyester high-tenacity fiber bundles of 40000 deniers are passed through a two-hole nipple having a rectangular section and through a rectangular die to make a longitudinal fiber-reinforced polymer strip having a section shown in (b) of FIG. 1 la with a width of 11.5 mm and a thickness of 2.5 mm. At this time, polypropylene having a melt index of 4 is used as a thermoplastic polymer resin. A lateral fiber-reinforced polymer strip having a section shown in (c) of FIG. 1 la with a width of 6.3 mm and a thickness of 1.5 mm is made with the use of three polyester high-tenacity fiber bundles of 7000 deniers and a three-hole nipple having a rectangular section. A position of the bending members 80'and 90'of the strip arranging unit is changed as shown in FIG. 10a, the made longitudinal strips are arranged on the strip arranging unit at intervals of 40 mm, and then the lateral fiber-reinforced strips are inserted at intervals of 50 mm to have an angle of 90° with the longitudinal strip, thereby making a lattice having a modified strip array as shown in FIG. 10b. Subsequently, contact points formed in the strip array are adhered with the use of a vibration welding device giving a frequency of 194 Hz and an amplitude of 0.5 mm to produce a geogrid.
The number of ribs per unit length (ribs/m), a wide-width tensile strength (kN/m),
LASE5% (kN/m), a tensile strain (%), a creep strain (%) and a strength reduction rate (%) under construction of the produced geogrid are shown in the following table 1.
Embodiment 7 A geog-id is produced in the same way as the sixth embodiment except that a position of the bending members 80'and 90'is changed as shown in FIG. l Oc.
The number of ribs per unit length (ribs/m), a wide-width tensile strength (kN/m), LASE5% (kN/m), a tensile strain (%), a creep strain (%) and a strength reduction rate (%) under construction of the produced geogrid are shown in the following table 1.
Table 1 Longitudinal strip Lateral ship Strength No. of Tensile Tensile Creep No. of Wide-width Tensile LASE5% reduction ribs strength strain strain ribs tensile strength strain (kN/m) rate (ribs/m) CN/m) f cN/m) (o/o) mte (o/o) (ribs/m) (kN/m) (%) Embodiment 25 96 54 10. 3 10. 5 4. 2 20 34 10. 3 1 Embodiment 25 98 52 10. 7 11. 4 4. 3 20 35 10. 5 2 Embodiment 25 95 53 II. O 10. 2 4. 4 20 38 10. 2 3 Embodiment 25 45 25 10. 9 11. 2 4. 5 25 45 10. 9 4 Embodiment 25 67 38 10. 7 11. 0 4. 3 25 39 10. 7 5 Embodiment 25 160 92 9. 9 H. 1 40 20 34 10. 5 6 Embodiment 25 158 158 90 10. 5 10. 4 4. 2 20 35 10. 6 7
Embodiment 8 A geogrid is produced in the same way as the third embodiment except that three glass fiber bundles of 2200 tex are used as a reinibrcing fiber instead of polyester fiber.
The number of ribs per unit length (ribs/m), a wide-width tensile strength (kN/m), LASE2% (kN/m) and a tensile strain (%) of the produced geogrid are shown in the following table 2.
Embodiment 9 A geogrid is produced in the same way as the sixth embodiment except that six glass fiber bundles of 2200 tex are used as a reinforcing fiber for a longitudinal strip and three glass fiber bundles of 2200 tex are used as a reinforcing fiber for a lateral strip.
The number of ribs per unit length (ribs/m), a wide-width tensile strength (kN/m), LASE2% (kN/m), a tensile strain (%), a creep strain (%) and a strength reduction rate (%) of the produced geogrid are shown in the following table 2.
Embodiment 10 A geogrid is produced in the same way as the seventh embodiment except that six glass fiber bundles of 2200 tex are used as a reinforcing fiber for a longitudinal strip and three glass fiber
bundles of 2200 tex are used as a reinforcing fiber for a lateral strip.
The number of ribs per unit length (ribs/m), a wide-width tensile strength (kN/m), LASE2% (IcN/m) and a tensile strain (%) of the produced geogrid are shown in the following table Table 2 Longitudinal strip Lateral strip Strength No. of Tensile Tensile Creep No. of Wide-width Tensile LASE2% reduction ribs strength strain strain ribs tensile strength strain ocN/m) rate (ribs/m) (kN/m) (%) o (o/o) (ribs/m) (kN/m) (%) "(/o) Embodiment 25 85 59 2. 5 12. 3 1. 2 20 76 2. 8 8 Embodiment 25 144 102 2. 4 11. 7 1. 2 20 72 2. 6 9 Embodiment 25 148 105 2. 9 11. 2 1. 3 20 75 2. 5 10
Comparative Example 1 Polyester high-tenacity fiber bundles are woven into a lattice shape, and then coated with polyvinylchloride resin to produce a textile geogrid.
The number of ribs per unit length (ribs/m), a wide-width tensile strength (kN/m), LASE5% (kN/m), a tensile strain (%), a creep strain (%) and a strength reduction rate (%) of the produced geogrid are shown in the following table 3.
Comparative Example 2 A plastic geogrid is produced according to a conventional method which is extruding a sheet with the use of polyolefin resin and then perforating and drawing the sheet on one axis.
The number of ribs per unit length (ribs), a wide-width tensile strength (kN/m).
LASE5% (lS/m), a tensile strain (%), a creep strain (%) and a strength reduction rate (%) of the produced geogrid are shown in the following table 3.
Comparative Example 3 A geogrid is produced by making longitudinal and lateral fiber-reinforced strips in the same way as the first embodiment. However, the lateral fiber-reinforced strips are extruded and inserted while the longitudinal fiber-reinforced strips are moving, and then the longitudinal and lateral fiber-reinforced strips are adhered with compression rollers to produce a fiber-reinforced geogrid having a lattice shape as shown in FIG. 12 with a width of 4 m.
The number of ribs per unit length (ribs), a wide-width tensile strength (kN/m), LASE5% (kN/m), a tensile strain (%), a creep strain (%) and a strength reduction rate (%) of the produced geogrid are shown in the following table 3, and shape stability and interactive coefficient are shown in FIG. 4.
Table 3 Longitudinal strip Lateral strip Strength No. of Tensile Tensile Creep No. of Wide-width Tensile LASE5% reduction ribs strength strain sttain ribs tensile stienb h strain (k/m) rate (ribs/m) (kN/m) (%) (%) (ribs/m) (kN/m) (%) (%) Comparative 41 88 43 10. 7 15. 8 5. 1 30 36 12. 7 Example I Comparative 43 92 45 12. 9 12. 2 14. 0--- Example 2 Comparative 25 85 43 10. 2 11. 2 4. 2 20 31 13. 2 Example 3 Table 4 Shape Stability Interactive Coefficient (Ci) Embodiment 1 Superior 0.95 Comparative Example 3 Inferior 0.88
When properties of the geogrids according to the embodiments and the comparative examples 1 and 2 are compared with reference to Tables 1 to 3, the following differences will be found.
First, the geogrids of the embodiments and the geogrid of the comparative example 1 show similar values in the wide-width tensile strength (kN/m), LASE5% (kN/m), the tensile strain (%) and the creep strain (%), but the strength reduction rate (%) is larger in the textile geogrid of the comparative example 1 rather than the geogrids of the embodiments. The strength reduction rate (%) makes it possible to estimate the installation damage, and high strength reduction rate means poor resistance to installation damage. Thus, it will be understood that the geogrids according to the embodiments of the present invention shows excellent resistance to installation damage rather than the textile geogrid. It means that the geogrid of the present invention is usable in a soil having many rocks since the reinforcing fiber of the geogrid is protected by the polymer resin and any damage applied in construction may be prevented.
5 Second, the geogrids of the embodiments and the plastic geogrid of the comparative example 2 show similar values in the wide-width tensile strength (kN/m), LASE5% (kN/m) and the strength reduction rate (%), but they show some difference in the tensile strain (%) and the creep strain (%). In particular, the creep strain (%) of the comparative example 2 is three times of that of the embodiments. This shows that the plastic geogrid has lower resistance against the 10 creep deformation rather than the geogrid of the present invention. That is to say, the conventional plastic geogrid shows high creep strain due to insufficient drawing at its junction points of longitudinal and lateral ribs when a load is applied thereto for a long time, while the geogrid of the present invention greatly improves resistance against the creep deformation since it is reinforced with the fiber having good resistance against the creep deformation.
15 In addition, if the properties of the geogrids of the embodiments are compared with those of the comparative example 3, the following differences are revealed.
First, though the strength reduction rate is similar in both cases, the shape stability is very different. That is to say, the geogrid of the comparative example 3 is apt to easily separate its contact points by a vertical load (see FIG. 13b), while, in the geogrid of the present invention, only 20 the contact points adhered below a lateral strip are separated due to the specific structure in which
the longitudinal and lateral fiber-reinforced polymer strips are arranged up and down in turns (see FIG. 13a).
Second, after the interaction coefficients Ci between the soil and the reinforcing material are compared, it is found that the interaction coefficient Ci of the geogrid of the first embodiment is 0.95 and the interaction coefficient C, of the geogrid of the comparative example 3 is 0.88. That is to say, the interactive coefficient of the geogrid according to the first embodiment is higher than that of the geogrid according to the comparative example 3. In connection with this fact, the interaction coefficient is influenced by the shape of the geogrid, particularly by the shape of members positioned vertical to a pullout direction. In the experiment for the geogrid having the same width of 60 cm, the geogrid of the comparative example 3 is configured so that the strip positioned vertical to a pullout force has a length of 60 cm, but the geogrid of the first embodiment is configured so that the strip positioned vertical to a drawing force has a length of more than 60 cm since a curvature is generated in the strip due to the up/down alternative arrangement. Thus, the passive resistant member of the geogrid according to the present invention gives larger contact area with the soil than that of the comparative example 3, so the geogrid of the present invention may give more excellent reinforcing function.
INDUSTRIAL APPLICABILITY As mentioned above, since the longitudinal and lateral fiber-reinforced polymer strips are alternatively arranged up and down and their cross contact points are welded and fixed to increase resistance against vertical load and frictional force with a reinforced material such as soil, the geogrid of the present invention gives excellent shape stability and superior resistance to installation damage. In addition, since the geog-id of the present invention uses the fiber-reinforced polymer strip in which a fiber is reinforced in a polymer resin, the geogrid of the present invention shows 5 high tensile strength, low tensile strain and low creep strain. Thus, the geogrid of the present invention may be useful as a reinforcing material in various civil engineering works such as for retaining wall reinforcement, slope reinforcement or soft ground reinforcement and as a protecting net of a building or other installations.
In addition, by using the method for producing a geogrid according to the present invention, 10 it is possible to mass-produce the geogrids at a low cost.
The present invention has been described in detail. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed 15 description.
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