Hsieh, Chang, Liu, and Liu. Paper No Title: Structural pattern effects on the engineering behavior of hexagonal wire mesh gabion panels

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1 Paper No Title: Structural pattern effects on the engineering behavior of hexagonal wire mesh gabion panels Author(s): Chiwan Wayne Hsieh Chewei Chang In-Wei Liu Ren-Sheng Liu 1.1 Transportation Research Board 92 nd Annual Meeting January 13 17, 2013 Washington, D.C.

2 Paper No.: Structural pattern effects on the engineering behavior of hexagonal wire mesh gabion panels by Chiwan Wayne Hsieh and In-Wei Liu Professor Department of Civil Engineering National Pingtung University of Science and Technology, Taiwan No.1, Shueh-fu Road, Neipu, Pingtung, Taiwan Tel No & Fax No cwh@mail.npust.edu.tw iwliu@mail.npust.edu.tw and Chewei Chang & Ren Sheng Liu Graduate Student Department of Civil Engineering National Pingtung University of Science and Technology, Taiwan Tel No Fax No This document has 6176 equivalent words

3 3 Structural pattern effects on the engineering behavior of hexagonal wire mesh gabion panels C.W. Hsieh, C.W. Chang, I.W. Liu & R.S. Liu ABSTRACT Three half-turn and four half-turn hexagonal wire mesh panels were built for tensile and punch tests with and without one center cut wire mesh panel. The study results indicated that the ultimate tensile strength or punch resistance for three half-turn and four half-turn hexagonal wire mesh panels without any cut within were similar. However, the four half-turn hexagonal wire panels showed better tensile and punch resistance after one wire broke at the panel center. This implied that the presence of broken wires within the four halfturn hexagonal wire mesh showed no significant influence on the panel s tensile strength and punch resistance. Four half-turn hexagonal wire mesh is a better structural pattern than that the three half-turn hexagonal wire mesh for slope stability and river bank protection applications. National Pingtung University of Science & Technology, Pingtung, Taiwan

4 4 INTROUDCTION Steel wire gabions are widely used for river bank protection in Taiwan. However, large stones and tree trunks carried by water damage gabion wire meshes during floods and cause gabion breakage. Currently, more than 15 million square meters of wire mesh gabion have been installed for river bank protection and slope stabilization applications in Taiwan. The annual material cost for river bank protection is more than 2 billion New Taiwan dollars. Currently, the average wire mesh gabion life-time period for these applications is about seven years. If a better wire mesh construction pattern can be used in practice, the replacement cost for river bank wire gabion protection would be reduced and the safety of hydraulic structures increased. The objective of this study is to investigate the engineering behavior of two different hexagonal wire mesh weaving patterns to provide technical information for engineers for future design and applications. RELATED LITERATURES In old times tree branches, rattan, and bamboo were used to construct gabion nets. Gabions were filled with pebbles, boulders, or rock pieces for river bank protection or retaining structures. Due to improvement in materials, galvanized steel wire is the most common material used to build current gabion structures. The Chinese version of Traditional Construction Technique Introduction and Explanation of Gabions was published by the Public Construction Commission (PCC) (2009). Taiwan received permission from the Japanese Gabion Association to translate the design guide into Chinese. The development background, design procedure, construction details, maintenance, case studies and cost and estimation for gabions are discussed in this guide. Muhunthan et al. (2005) prepared a research report, Analysis and Design of Wire Mesh/Cable Net Slope Protection, for the FHWA, USA. The field performance, test data and design guidelines are all covered in this report. Agostini et al. (1988) presented a technical report, hexagonal wire mesh for rock-fall and slope stabilization, to discuss the engineering and technical details of hexagonal wire mesh for engineering applications. Bergado & Teerawattanasuk (2001) developed several analytical models for predicting the pullout capacity and interaction between hexagonal wire mesh and silty sand backfill. Sasiharan et al. (2006) conducted a numerical analysis to study the performance of wire mesh and cable net rock fall protection systems. Bertrand et al. (2008) used the discrete element method to model double-twisted hexagonal mesh systems. The engineering behavior of hexagonal mesh systems was studied by laboratory testing and numerical analysis. Lin et al. (2009) performed a laboratory study to evaluate the pull out behavior of two types of hexagonal wire meshes and two kinds of rigid geogrids. The hexagonal wire mesh structural pattern influence on engineering behavior was investigated. TEST MATERIALS AND PROGRAM Hexagonal steel wire mesh is commonly used to construct steel wire gabions for river bank protection and slope stability applications. Because machine-made hexagonal wire mesh panels are usually woven from more than 30 strings of steel wires, a panel would typically consist of one or two wire connections within each mesh panel. These connections are generally the wire mesh panel weak points during service life or test procedures. A large testing machine with grips is required to conduct full scale engineering tests. Therefore, it was found easier and better to construct hexagonal wire mesh models for this preliminary test program. Three half-turn (Type A) and four half-turn (Type B) hexagonal double twisted wire mesh panels were constructed and tested to evaluate the difference in engineering behavior using tensile and punch tests. The mesh was woven using a nominal diameter of 1.18 mm galvanized steel wire. The tensile strength of the steel wire is 510 N/mm2. Forty-three (43) mm by 50 mm mesh opening was used to construct a near perfect hexagonal pattern wire mesh for both types. The test model hexagonal wire meshes consisted of structural patterns similar to typical full scale wire meshes. However, the only difference between the two mesh designs was the opening size. ASTM A975 and A370 test methods are used in these tests. Wire mesh panel tensile and punch tests with and without a center cut were conducted. The difference in weaving pattern between three half-turn (Type A) and four half-turn (Type B) double twisted hexagonal wire meshes is demonstrated in Figures 1 and 2, indicated as Type A and Type B wire mesh. As shown in the figures, top-down (vertical) and diagonal weaving patterns were observed for three half-turn and four half-turn wire meshes, respectively. Different engineering behavior can be expected due to the difference in weaving structure of these two types of meshes. The tensile test sample setup is shown in Figures 3. The tensile test panel dimension was 563mm by 300mm. RESULTS AND DISCUSSIONS

5 5 A series of wide width tensile and punch tests were conducted according to the ASTM D975 test method. The test panel dimensions were 563mm by 300mm and 900mm by 400mm for the wide width tensile and punch tests, respectively. Tensile and punch tests for Type A and Type B double twisted hexagonal wire mesh panels with and without one center wire cut were conducted. A minimum of three repeated tests were conducted for each test condition to prove the repeatability of the engineering behavior. A very good repeatability of the tensile tests and punch tests for Type A and Type B double twisted hexagonal wire mesh panels is shown in the Figures 4 and 5, respectively. The representative test results are discussed as follows. The test conditions are represented using two letters; the first letter indicates the test material and the second letter shows the cut wire condition. Tensile tests without a center cut wire The tensile test results for three half-turn (Type A) and four half-turn (Type B) hexagonal wire mesh panels are shown in Figure 6. As shown in Figure 6, the initial tensile force versus elongation curves for both wire types of mesh are quite similar to each other. The tensile stress versus elongation curves can be divided into four stages. According to observation the elongations were contributed from the straight and twisted wire sections of the hexagonal wire mesh for stage-1 and stage-3. The elongation for stage-2 was a transition between stage-1 and stage-3. The first and maximum peak tensile stress occurred at elongation around 50 to 60 mm for both wire types. After the tensile stress reached a peak, a drop in tensile stress associated with mesh elongation and steel wire de-twisting occurred near the broken wire. In general, one peak stress is associated with breaking one steel wire. The elongation after the first peak was considered as the test stage-4. The peak tensile force for Type A wire mesh is slightly higher than that for Type B wire mesh. However, several similar consecutive peak tensile forces were observed after the first and highest peak tensile force occurred as the elongation continued. A larger amount of elongation between each consecutive break was also observed for the Type A mesh test. This implied that Type A wire mesh elongated more and quicker than Type B wire mesh. The consecutive peak tensile forces for the Type B wire mesh panel decreased as the elongation increased. However, the elongation between each consecutive break was significantly less than that for Type A wire mesh. This implied that Type B wire mesh deformed less when subjected to tensile loads. Tensile test of panel with a center cut wire In many cases, steel wires in a panel would be broken by stones or other objects during panel service life. Therefore, it is necessary to study the engineering behavior of steel wire mesh with some steel wires broken. A series of tensile tests for Type A and Type B hexagonal wire mesh panels with one center wire cut was performed. The typical tensile force versus elongation curves are shown in Figure 7. As shown in the figure, the maximum tensile forces for both wire mesh types were about 5 kn and quite similar to each other. However, the elongation at maximum tensile force for Type A wire mesh was much greater than that for Type B wire mesh. Typical failure modes for the Type A and Type B wire mesh panel tensile tests with one center wire cut are shown in Figures 8 and 9. As shown in Figures 8 and 9, steel wire de-twisting occurred around the cut wire, inducing the mesh panel to divide into two parts at the center. The steel wire de-twisting around the cut wire in the tensile test for Type B wire mesh was relatively less significant. Wire breakage occurred around the cut wire as shown in Figure 9. Comparing the typical tensile force versus elongation curve for Type A wire mesh with and without one cut center wire, a significant difference in wire mesh elongation occurred between the two test conditions. Comparison of typical tensile test curves for Type B wire mesh with and without one cut center wire was quite similar to each other. This implied that the presence of one center cut wire in the Type B mesh panel showed no significant effect on the tensile behavior. However, the Type A mesh panel showed a larger displacement and less tensile resistance after one wire was cut at the center of the panel. Punch tests Pebbles and boulders are commonly used to fill the steel wire gabions to construct retaining earth structures or for slope protection applications. A punch test was used to evaluate the engineering behavior of wire mesh subjected to pushing or bursting force from pebbles and boulders due to external forces. A half circular steel ball with diameter of 200 mm, three times the dimension of the test mesh opening, was used as the punching object in the test. A 900mm by 400 mm mesh panel was fixed at four boundaries using shop design clamps.

6 6 Punch test results for three half-turn (Type A) and four half-turn (Type B) hexagonal wire mesh panels are shown in Figure 10. As shown in Figure 10, the peak punch force for Type A wire mesh was slightly higher than that for Type B mesh. However, the slope for the punch force versus displacement curve for the Type B mesh was slightly higher than that for Type A mesh. Since one peak force shown in Figure 10 is associated with one broken steel wire, a drop in punch force is also associated with the broken wire and wire de-twisting near the broken wire and push head displacement. Several similar consecutive peak punch forces were observed after the first, highest peak punch force occurring as the punch head displacement continued. A larger amount of punch displacement between several consecutive peaks was also observed for Type A wire mesh. This implied that the punch resistance for Type A wire mesh was less than that for Type B wire mesh. The consecutive peak punch forces for Type B wire mesh gradually decreased as the punch head displacement increased. The head displacement between each consecutive peak was significantly less than that for Type A wire mesh. A series of punch tests for Type A and Type B hexagonal wire mesh panels with one center cut were also performed. The typical punch force versus displacement curves are shown in Figure 11. As shown, no significant peak punch force was observed for Type A mesh. The maximum punch force was only about 0.8 kn. Low punch resistance was measured and a greater punch displacement was observed as shown in Figure 11. The punch head was easily pushed through the wire mesh during the test. In contrast, 2.6 kn maximum peak punch force was measured and the consecutive peak punch forces gradually decreased as the head displacement increased for Type B wire mesh. Low head displacement was measured between each consecutive peak punch force. The typical failure modes near the end of the punch tests for Type A and Type B wire mesh panels are shown in Figures 12 and 13. A large and near circular punch hole is shown in Figure 12 for Type A wire mesh. An irregular punch hole is observed in Figure 13 for Type B wire mesh. In general, Type B wire mesh showed better punch resistance than Type A wire mesh. A comparison of the typical punch force versus displacement curve for Type A wire mesh with and without one center wire cut showed that a significant difference in displacement occurred between the two test conditions. A much lower punch resistance with a larger punch displacement and steel wire de-twisting near the punch hole occurred for the condition with one center wire cut. In contrast, the tests for Type B wire mesh showed the punch force versus punch head displacement curves for mesh panels with and without one center cut wire were quite similar to each other. This implied that the presence of one center cut wire showed no significant influence on the punch behavior for Type B wire mesh. It is interesting that the first peak punch force for the mesh with one center cut wire was similar to the second highest peak punch force for the mesh without one center cut wire. The remaining test data from these two tests showed good similarities to each other. CONCLUSIONS The average replacement time for wire mesh gabions for river bank protection and stabilization applications is about seven years in Taiwan. The annual material cost for this is more than 2 billion New Taiwan dollars. This study investigated the engineering behavior of three half-turn and four half turn hexagonal wire meshes using tensile and punch tests. The results of the study provide technical information for engineers to reduce the replacement costs for wire gabion. Further research may require to establish data to improve the design and increase the safety of hydraulic structures. The study results indicated that the ultimate tensile strength or punch resistance for three half-turn or four half-turn hexagonal wire mesh panels without cut wires were similar. However, the four half-turn hexagonal wire panels showed better tensile and punch resistance after one wire was cut at the panel center. This implied that the presence of broken wires within the four half-turn hexagonal wire mesh would show no significant influence on the panel tensile strength and punch resistance. Four half-turn hexagonal wire mesh is a better weaving pattern than three half-turn hexagonal wire mesh for slope stability and river bank protection applications. REFERENCES

7 7 1.Agostini, R., Mazzalai, P., & Papetti, A., Hexagonal wire mesh for rock-fall and slope stabilization, Bologna Italy, Officine Maccaferri S.p.A. 2.ASTM A975-97, Double-Twist Hexagonal Mesh Gabions and Revet Mattresses (Metallic-Coated Steel Wire or Metallic-Coated Steel Wire with Poly (Vinyl Chloride) (PVC) Coating), Philadelphia, USA. 3.ASTM A370-97a, Standard Test Methods and Definitions for Mechanical Testing of steel Products, Philadelphia, USA. 4.Bergado, D.T., & Teerawattanasuk, C., Analytical Models for Predicting the Pullout Capacity and Interaction between Hexagonal Wire Mesh and Silty Sand Backfill, Tamkang Journal of Science and Engineering 4(4): Bertrand, D., Nicot, F., Gotteland, P., & Lanert, S., Discrete Element Method (DEM) numerical modeling of double-twisted hexagonal mesh, Canadian Geotechnical Journal 45: Lin, Y.L., Yang, G.L., Li, Y., Fang, W., The Mechanical Characteristics of the Reinforcements under Tensile Load, China Railway Science 30(5): Muhunthan, B., Shu, S., Sasiharan, N., Hattamleh, O., Badger, T., Lowell, S., and Duffy, D., Analysis and Design of Wire Mesh/Cable Net Slope Protection, Washington State Transportation Commission and Department of Transportation, Federal Highway Administration, USA. ( ) 8.Public Construction Commission, Traditional Construction Technique Introduction and Explanation of Gabions, Taipei Taiwan (in Chinese). 9.Sasilharan, N., Muhunthan, B., Badger, T.C., Shu, S., & Carradine, D.M., Numerical analysis of the performance of wire mesh and cable net rockfall protection systems, Engineering Geology 88:

8 8 Listing of Figure Captions FIGURE 1 Schematic view of wire weaving pattern for Type A mesh FIGURE 2 Schematic view of wire weaving pattern for Type B mesh FIGURE 3 Schematic view of the setup for tensile test FIGURE 4 Three repeated tensile test results of Type A and B mesh panels without one cut wire FIGURE 5 Three repeated punch test results for Type A and B mesh panels without one cut wire FIGURE 6 Typical tensile test results for Type A and B mesh panels without one cut wire FIGURE 7 Typical tensile test results for Type A and B mesh panels with one cut wire FIGURE 8 Tensile failure mode of Type A mesh panel with one center cut wire FIGURE 9 Tensile failure mode of Type B mesh with one center cut wire FIGURE 10 Punch test results for Type A and B mesh panels without one center cut wire FIGURE 11 Punch test results for Type A and B mesh panels with one center cut wire FIGURE 12 Punch failure mode of Type A mesh with one center cut wire FIGURE 13 Punch failure mode of Type B mesh without one center cut wire

9 9 Figure 1. Schematic view of wire weaving pattern for Type A mesh.

10 10 Figure 2. Schematic view of wire weaving pattern for Type B mesh.

11 11 Figure 3. Schematic view of the setup for tensile test.

12 12 (a) Type Au (b) Type Bu Figure 4. Three repeated tensile test results of Type A and B mesh panels without one cut wire.

13 13 (a) Type Au (b) Type Bu Figure 5. Three repeated punch test results for Type A and B mesh panels without one cut wire.

14 14 Figure 6. Typical tensile test results for Type A and B mesh panels without one cut wire.

15 15 Figure 7. Typical tensile test results for Type A and B mesh panels with one cut wire.

16 16 Figure 8. Tensile failure mode of Type A mesh panel with one center cut wire.

17 17 Figure 9. Tensile failure mode of Type B mesh with one center cut wire.

18 18 Figure 10. Punch test results for Type A and B mesh panels without one center cut wire.

19 19 Figure 11. Punch test results for Type A and B mesh panels with one center cut wire.

20 20 Figure 12. Punch failure mode of Type A mesh with one center cut wire.

21 21 Figure 13. Punch failure mode of Type B mesh without one center cut wire.