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Abstract

Investigation of Factors Affecting Discharge Capacity of Prefabricated Vertical Drains An important factor affecting the performance of PVDs is their discharge capacity. The effect of factors such as, the hydraulic gradient, lateral stresses on a PVD, the type of soil in which PVDs are placed, the structure of PVDs and their flexural stiffness were investigated. Four different types of PVDs were used to investigate the effects of PVD deformation during the consolidation of soil and clogging of the core area on the discharge capacity of PVDs. The discharge capacity of PVDs, which is large at low deformations, decreases significantly (up to 57%) within the range of hydraulic gradients applied in this study (0.10 to 1.00). At large deformations, PVDs have a lower discharge capacity although the change in hydraulic gradient has a negligible effect on them. On the other hand, experimental observations have shown that the deformations occurring during consolidation of soils have an important effect on the discharge capacity of PVDs. For the type of PVDs used, the discharge capacity decreases by 68% to 100% when PVDs deform by 41.5%. Furthermore, a 40% decrease in discharge capacity is observed when lateral stress is increased from 25 kPa to 200 kPa. Clogging of the core zone, shapes of deformation, structure of PVD, and resistance against buckling have varying effects on the discharge capacity of PVDs depending on the soil type

Keywords

• Prefabricated vertical drain, model testing system for discharge capacity, discharge capacity of prefabricated vertical drains

Prefabrik Düşey Drenlerin (PDD) Boşaltma Kapasitesini Etkileyen Faktörlerin Belirlenmesi

Abstract

PDD’lerin performansını etkileyen önemli faktörlerden biri boşaltma kapasitesidir. Bu nedenle dört farklı özellikteki PDD türü için, uygulanan hidrolik eğim, etkiyen yanal gerilme, uygulandığı zemin cinsi, PDD’nin yapısı ve bükülmeye karşı direnci gibi faktörler dikkate alınarak, zeminin konsolidasyonu sırasında oluşan PDD’nin deformasyonu ve çekirdek bölgesinin kirlenmesinin boşaltma kapasitesi üzerine etkileri araştırılmıştır. Sonuçlar değerlendirildiğinde, düşük deformasyon seviyelerinde yüksek olan PDD’lerin boşaltma kapasitesi, bu çalışmada uygulanan en düşük ve en yüksek hidrolik eğim seviyesi aralığında (0.10-1.00) hidrolik eğimin artmasıyla önemli bir miktarda (%57’ye kadar) azalırken, yüksek deformasyon seviyelerinde daha düşük olan boşaltma kapasitesi üzerinde hidrolik eğimin etkisinin ihmal edilebilir olduğu gözlenmiştir. Zeminin konsolidasyonu sırasında farklı PDD türlerinde meydana gelen deformasyonun boşaltma kapasitesi üzerindeki etkileri incelendiğinde, %41.5 civarında deformasyon meydana geldiğinde boşaltma kapasitesinin %68-%100 arasında azalabileceği, etkiyen yanal gerilmeye bağlı olarak ise, yanal gerilmenin 25 kPa değerinden 200 kPa’ya yükselmesi durumunda boşaltma kapasitesinde yaklaşık %40 azalma olduğu belirlenmiştir. PDD’nin çekirdek bölgesinin kirlenmesi, PDD’de meydana gelen deformasyon biçimleri, PDD’nin yapısı ve bükülmeye karşı direnci gibi faktörlerin de uygulandığı zemin cinsine göre boşaltma kapasitesi üzerinde değişik derecelerde etkileri olduğu gözlenmiştir

Keywords

• Prefabrik düşey dren, boşaltma kapasitesi model deney sistemi, prefabrik düşey drenlerin boşaltma kapasitesi

References

1. ASTM D4716, Standard test method for determining the (in-plane) flow rate per unit width and hydraulic transmissivity of a geosynthetic using a constant head, Annual Book of ASTM Standards, 1995.
2. Chu, J., Bo, M.W. ve Choa, V., Practical Considerations for Using Vertical Drains in Soil Improvement Projects, Geotextiles and Geomembranes, 22: 101-117, 2004.
3. Hansbo, S., How to Evaluate the Properties of Prefabricated Drains, Proceedings of the Eighth European Conference on Soil Mechanics and Foundation Engineering: Improvement of Ground. Vol.2, Soil Reinforcement, Speeding Up of Consolidation, Improvement of Special Soils, Soil Improvement Under Water and Soil Stabilization., Helsinki, 6(13): 621-626, 1983.
4. Kamon, M., Pradhan, B.S., Suwa, S., Laboratory Evaluation of The Prefabricated Bands-Shaped Drains, Soil Improvement, Current Japanese Materials Research. Vol.9, Cambridge University Press, Cambridge, UK, 1984.
5. Guido, V.A., Ludewig, N.M., A Comparative Laboratory Evaluation of Band-Shaped Prefabricated Drains, In. Yong, R.N., Townsend, F.C. (Eds.), Consolidation of Soils: Testing and Evaluation, ASTM STP 892, 642-662, 1986.
6. Suits, L.D., Gemme, R.L., Masi, J.J., Effectiveness of Prefabricated Drains on Laboratory Consolidation of Remolded Soils, In. Yong, R.N., Townsend, F.C. (Eds.), Consolidation of Soils: Testing and Evaluation, ASTM STP 892, 663-683, 1986.
7. Bergado, D.T., Manivannan, R. ve Balasubramaniam, A.S., Proposed Criteria for Discharge Capacity of Prefabricated Vertical Drains, Geotextile and Geomembranes, 14: 481-505, 1996.
8. Lee, C.H., Kang, S.T., Discharge Capacity of Prefabricated Vertical Band Drains, Final Year Report, Nanyang Technological University, Singapore, 1996.

9. Sasaki, S., Report of Experimental Test for the Prefabricated Drain Geodrain, Tokyo Construction Co., Tokyo, 1981.
10. Miura, N., Chai, J.C. ve Toyota, K., Investigation on Some Factors Affecting Discharge Capacity of Prefabricated Vertical Drain, Proceedings of the 6th International Conference on Geosynthetics, IFAI, Atlanta, Georgia, 2: 845-850. 1998.
11. Kremer, R., De Jager, W., Maagdenberg, A., Meyvogel, I. ve Oostveen, J., Quality Standards for Vertical Drains, Proceedings 2nd International Conference on Geotextiles, Las Vegas, 2: 319-324, 1982.
12. Kremer, R., Discussion to Specialty Session 6, Proceedings of the 8th European Conference on Soil Mechanics and Foundation Engineering, Helsinki, 3: 1235-1237, 1983.
13. Ali, F.H., The Flow Behavior of Deformed Prefabricated Vertical Drains, Geotextiles and Geomembrane, Vol.10, 235-248, 1991.
14. Chu, J., Bo, M.W. ve Choa, V., Improvement of Ultra-Soft Soil Using Prefabricated Vertical Drains, Geotextiles and Geomembranes, 24: 339-348, 2006.
15. Tran-Nguyen, H.H., Effect of Deformation of Prefabricated Vertical Drain on Discharge Capacity and The Characteristics of PVD Smear Zone, University of Wisconsin-Madison, P.H.D. Thesis, 2010.
16. Bo, M.W., Chu, J. ve Choa, V., Soil Improvement: Prefabricated Vertical Drain Techniques, Thompson, Singapore, 341, 2003.
17. Holtz, R. D., Jamiolkowski, M. B., Lancellotta, R. ve Pedroni, R., Prefabricated Vertical Drains: Design and Performance, Butterworth-Heinemann, Oxford, U.K., 1991.
18. Miura, N. ve Chai, J.C., Discharge Capacity of Prefabricated Vertical Drains Confined in Clay, Geosynthetics International, 7(2): 119-135, 2000.
19. Chai, J.C., Miura, N. ve Nomura, T., Effect of Hydraulic Radius on Long-Term Drainage Capacity of Geosynthetics Drains, Geotextiles and Geomembranes, 22(1-2): 3-16, 2004.