應變率對地工加勁材基本性質影響之探討

Influence of Strain Rate on Measured Geosynthetic Reinforcement Properties

林上源(Shang-Yuan Lin)

指導教授 ： 張達德

中原大學/工學院/土木工程研究所/碩士(2001年)

https://doi.org/10.6840/cycu200100248

摘要

摘 要

關鍵字：加勁材模數、應變率、寬幅抗張試驗、單肋強度試驗

地工加勁材料之強度特性通常均由ASTM D4595寬幅抗拉試驗及GRI-GG1單肋強度試驗所求得，然而，現地加勁擋土牆結構中加勁材承受拉力之真實速率約比ASTM D4595寬幅試驗中10%變形/min之拉伸速率慢約105~106等級。因此，Holtz and Lee (1998) 建議依據織物低應變率寬幅試驗結果 (Boyle et al., 1996)，對不同材質織布之材料模數進行修正與調整。並發現若將修正後之材料模數應用於預測加勁擋土結構之力學機制，可產生很大之功效 (Lee et al., 1999)。故為了正確的分析加勁擋土結構內部應力－應變之分佈情形，必須將地工加勁材於低應變率狀態下所受之影響及模數折減率列入考慮。
因此，本研究為進一步探討應變率對地工加勁材性質影響之程度，針對八種不同材質、性質與強度之加勁材進行一系列之低應變率無圍壓抗張試驗，施加於加勁材之變形速率為50 ~ 0.05mm/min，試體尺寸為200mm ×200mm (夾具間為200mm ×100mm，依據ASTM D4595) 與格網單一肋條 (依據GRI-GG1)。
於研究之本文中將呈現下列成果：
1.將應變率對不同材質、性質與強度地工加勁材抗拉強度、材料模數與極限應變之影響進行分析，計算折減幅度與增量。
2.提出各種地工加勁材於低應變率狀態下之材料模數修正因子建議值。
研究之成果期望能增加大眾對地工加勁材力學性質之了解，並更準確預測加勁結構之變形行為及改善加勁擋土結構之設計方法。

關鍵字

單肋強度試驗 ； 加勁材模數 ； 應變率 ； 寬幅抗張試驗

並列摘要

ABSTRACT

Keywords：Modulus of Geosynthetic Reinforcements, Strain Rate, Wide Width Tensile Strength Test, Single Rib Strength Test

Strength properties of geosynthetic reinforcement are often obtained by performing ASTM D4595 wide width tensile test or GRI-GG1 single rib tensile tests. However, the actual rate of loading of the reinforcement in the field during wall construction may be five or six orders of magnitude slower than the standard ASTM D4595 testing rates. Holtz and Lee (1998) proposed low strain rate adjustments for moduli of different woven geotextile manufactured using different polymer materials based on the low strain rate wide width tensile test results (Boyle et al., 1996). The proposed modulus adjustments were found to be of great help in predicting performance of geosynthetic reinforced soil (GRS) retaining walls (Lee et al., 1999). It was found that Moduli of geosynthetic reinforcement had to be adjusted for the low strain rate conditions in order to correctly analyze the stress－strain distributions inside GRS retaining structures.
However, the strain effect on nonwoven geosynthetic reinforcement and geogrid has not been well studied so far. In an effort to further analyze the strain rate effects on the engineering properties of different geosynthetic reinforcement materials. The testing strain rates are ranged from 50 mm/min to 0.5 mm/min, and the specimen sizes are varied form the single rib specimen requirement (specified by GRI-GG1) to 200mm × 200mm (specified by ASTM D4595).
In this thesis, follows will be presented:
1. Summary and discussions of the strain rate controlled strength tests of different geosynthetic reinforcements; and
2. Proposed low strain rate adjustments for moduli of geosynthetic reinforcements.
Results of this study are hoped to improve our understanding of engineering properties of geosynthetic reinforcement under actual working conditions; as well as to improve design and performance prediction of GRS structures.

並列關鍵字

Single Rib Strength Test ； Strain Rate ； Modulus of Geosynthetic Reinforcements ； Wide Width Tensile Strength Test

參考文獻

20.謝啟萬，“地工合成材料常用檢測方法簡介”，地工技術雜誌第七十一期，pp. 13-28 (1999)。

27.Boyle, S.R., Gallagher, M. and Holtz, R.D., 1996, “Influence of Strain Rate, Specimen Length and Confinement on Measured Geotextile Properties”, Geosynthetics International, Vol. 3, No. 2, pp. 205-225.

28.Boyle, S.R., 1995a, “Deformation Prediction of Geosynthetic Reinforced Soil Retaining Walls”, Ph.D. Dissertation, Department of Civil Engineering, University of Washington, Seattle, Washington, USA, 391p.

35.Gallagher, M., 1995, “In-Isolation Wide Width Tests on Geotextiles”, M.Sc. Thesis, Department of Civil Engineering, Universty of Washington, Seattle, USA, 135p.

44.Lee, W.F., (1999) “Distributions of Lateral Earth Pressure and Reinforcement Tension Inside the Geosynthetic Reinforced Soil Retaining Walls”, Proceedings of Geosynthetics ’99, Boston, Vol. 2, pp. 651-660.