現今加勁擋土牆設計規範多以滲透性高之顆粒性砂土級配料作為回填材料，但實際上卻常用現地的非顆粒性土壤回填，這樣的背填材料對牆體的穩定性影響甚鉅。過去案例中不乏因連日豪雨致使回填材料含水量上升，造成土壤不排水剪力強度迅速減低，側向土壓力增加而破壞的案例。
因此本研究乃利用地工離心模型試驗探討改變加勁材的配置方式，探討在高含水量下以中大紅土為背填材料之加勁擋土牆穩定性的改良效果。研究結果顯示：1.藉著本研究所提出之改善率等高線圖可得到在高含水量粘土加勁擋土牆之加勁材的最佳配置方式。2.加勁間距減小為0.067H、加勁長度增長為0.85H時，可獲得最大改善量為90%。3.當加勁間距為0.1H時，牆面變形行為肚凸狀；加勁間距為0.067H時，牆面變形行為前傾狀。4.牆體的破壞面不會穿過牆趾，而外部不穩定破壞面是在牆趾上方約0.133H處開始大約沿夾角θ=tan-1(0.43H/L)向上發展；內部不穩定破壞面是在牆趾上方約0.133H處開始大約沿夾角45°向上發展。

Mechanically Stabilized Earth Wall (MSEW) is required to use the high quality granular soil as reinforced backfill materials. In practice, however, the in-situ clayey soil is usually used instead to cut down the cost, which obviously violates the design assumptions. Nevertheless, the clayey soil backfill may block the draining path, leading to increase in water content and lateral earth pressure during heavy rainfall. There were many cases of failure of MSEW with clayey soil backfill caused by cloudburst in Taiwan.
Sixteen centrifuge modeling tests were performed to investigate the effectiveness of different combinations of reinforcement length and spacing in improving the stability of MSEW with clayey soil backfill at high water content (41%). Based on the test results, a contour plot is proposed which can be used to determine the different combinations of reinforcement length and spacing for a given amount of improvement ratio of deformation. From the test results of this study, the maximum improvement ratio is 90% with 0.067H reinforcement spacing and 0.85H reinforcement length. The deformation types of wall facing are bulging and tilting with 0.1H and 0.067H reinforcement spacing, respectively. The failure surface for external instability starts at 0.133H above the toe of the wall and extends along the angle of tan-1(0.43H/L) until it intersects with reinforcement end and then extend upward; the failure surface for internal instability also starts at 0.133H above the toe of the wall, but extends along an angle of 45° until it intersects the horizontal line at a height of 0.5H and then extends upward, lying within the reinforced zone.

參考文獻
[1] Acutronic, Civil Engineering Centrifuge Model 665-1 Installation Manual 5941E, France (1992).
[2] Acutronic, Geotechnical Centrifuge Model 665-1 Product Description 5933H, France (1993).
[3] Acutronic, Geotechnical Centrifuge Model 665-1 Technical Proposal 6022, France (1993).
[4] Goodings, D. J., and Santamarina, J. C., “Reinforced Earth and Adjacent Soils: Centrifuge Modeling Study,” Journal of Geotechnical Engineering, Vol. 115, No. 7, pp.1021-1025 (1989).
[5] Huang, C. C., “Report on Three Unsuccessful Reinforced Walls,” Recent Case Histories of Permanent Geosynthetic-Reinforced Soil Retaining Walls, (eds. Tatsuoka & Leshchinsky), Balkema, Rotterdam pp. 219-222(1994).
[6] Jewell, R. A., Millilgan, G. W. E., Sarsby, R. W., and Dubois, D., “Interaction Between Soil and Geogrids,” Proc. Symp. On Polymer Grid Reinforcement in Civil Engineering, Science and Engineering Research Council and Netlon Limited, March 22-23(1984).
[7] Leshchinsky, D., Volk, J. C., and Reinschmidt, A. J., ”Stability of Geotextile-Retained Earth Railroad Embankments,” Geotextiles and Geomembranes, 3, 105-128(1986).
[8] Mechanically Stabilized Earth Walls and Reinforced Soil Slopes Design and Construction Guidelines, U.S., Department of Transportation Federal Highway Administration(FHWA), NHI Course, No. 132042(2001).
[9] Porbaha, A., and Goodings, D. J., “Centrifuge Modeling of Geotextile-Reinforced Steep Clay Slopes,” Canadian Geotechnical Journal, Vol. 33, pp696-704(1996).
[10]Porbaha, A., and Goodings, D. J., “Centrifuge Modeling of Geotextile-Reinforced Cohesive Soil Retaining Walls,” Journal of Geotechnical Engineering, Vol.122 No.10 pp.840-847(1996).
[11]Porbaha, A., and Goodings, D. J., “Laboratory Investigation of Nonuminformly Reinforced Soil-Retaining Structures,” Geotechnical Testing Journal, Vol. 20, No. 3, pp289-295 (1997)
[12]Suah, P. G., and Goodings, D. J., “PART 4 GEOSYNTHETICS IN TRANSPORTATION FACILITIES - Failure of Geotextile-Reinforced Vertical Soil Walls with Marginal Backfill,” Transportation Research Record, No. 1772, pp. 183-189 (1989).
[13]Shahar, Y., and Frydman, S., “Centrifuge modeling of narrow reinforced retaining walls,” Physical Modeling in Geotechnics, pp. 1005-1010 (2002).
[14] Yang, Z., “Strength and Deformation characteristics of Reinforced Sand,” Ph.D Dissertation,University of California at Kos Angeles(1972).
[15]Yoo, N.J., and Ko, H-Y., ”Centrifuge modeling of reinforced earth retaining walls, ” Proceedings,Centrifuge 91,Ko(ed),Balkema,Rotterdam,pp.325-332(1991).
[16] Zornberg, J. G., Sitar, N., and Mitchell, J.K., “Performance of Geosynthetic Reinforced Slopes at Failure,” Journal of Geotechnical and Geoenvironmental Engineering, Vol.124, No.8, pp.670-683 (1998)
[17] Zornberg, J. G., Sitar, N., and Mitchell, J. K., “Limit Equilibrium as Basis for Design of Geosynthetic Reinforced Slopes,” Journal of Geotechnical and Geoenvironmental Engineering, Vol.124, No.8, pp.684-698(1998).
[18]李崇正，「離心模型試驗在大地工程之應用」，地工技術雜誌，第36期，第76-91頁（1991）。
[19]李咸亨，「神戶地震中加勁擋土牆的行為」，現代營建，第210期，第24-29頁（1997）。
[20]周南山，「加勁擋土結構之分析設計及其在公路與高鐵之應用（一）」，現代營建，第216期，第11-18頁（1997）。
[21]周南山等人，加勁擋土結構設計及施工手冊，台北市土木技師公會，第三章，第7-17頁(2001)。
[22]周南山、陳鴻運，「坡地社區安全工法及防災預警系統之研究(一)」，內政部建築研究所研究計畫成果報告，No.091301070000G1014，台北（2002）。
[23]黃景川，「以粘土質沉泥為背填土之大型加勁擋土牆長期觀測與降雨試驗」，行政院國家科學委員會專題研究計畫成果報告，No.NSC85-2611-E-006-31，台南(1996)。
[24]黃景川，「921集集地震中擋土結構之損害調查與分析」，國家地震工程研究中心研究報告，No. NSC89-2921-Z-319-005-05，台北(200)。
[25]陳景文、吳宗欣、Claybourn, A. F.，「不同地工織物擋土牆設計方法之比較」，地工技術雜誌，第43期，第43-49頁（1993）。
[26]陳榮河，「地工合成材於掩埋場之應用」，地工技術，第71期，第57-63頁（1999）。
[27]陳柏文，「以離心模型試驗探討高含水量黏性背填土加勁擋土牆之穩定性」，碩士論文，國立中央大學土木工程學系，中壢(2002)。
[28]陳元吉，「以加勁長度改善高含水量下黏土加勁擋土牆穩定性之研究」，碩士論文，國立中央大學土木工程學系，中壢(2003)。
[29]章為民、賴忠中、徐光明，「加筋擋土牆離心模型試驗研究」，土木工程學報，第33卷，第3期，第84～91頁（2000）。
[30]單信瑜，「地工合成材料於山坡掩埋場之應用」，地工技術，第73期，第57-66頁（1999）。
[31]楊錫武、歐陽仲春，「加筋高路堤陡坡邊坡離心模型的研究」，土木工程學報，第33卷，第5期，第88～91頁（2000）。