Kohezyonsuz Zeminde CPT ile Kazık Kapasitesinin Boşluksal Değişkenlikle Hesabı

Year 2021, , 1051 - 1060, 29.12.2021

Ahmet Can Mert Gökhan Yazıcı

https://doi.org/10.21605/cukurovaumfd.1048348

Abstract

Çalışma, kohezyonsuz zeminde CPT tabanlı kazık nihai taşıma kapasitesi hesabı için rastgele alan teorisine dayalı bir yöntem oluşturmayı amaçlamaktadır. Koni uç direnci (qc), sabit alınan ortalama ve farklı değişme katsayısı (COV) değerleri ile boşluksal değişken olarak tanımlanmıştır. Rastgele alan ile CPT profilleri benzeştirilmiş ve tekil kazığın nihai kapasitesi (Qu) bu simule edilen profillerle hesaplanmıştır. qc’deki değişimin Qu değerlerine etkisi incelenmiştir. Önerilen yöntem son olarak, gerçek CPT veri tabanı ile ve simule CPT profilleri ile hesaplanan sonuçların karşılaştırılması ile doğrulanmıştır. Edinilen sonuçlar CPT tabanlı kazık kapasite hesaplarında, düşey dalgalanma ölçeğinin kritik değerinin bir kazık çapı kadar olduğunu (dv=1D), ve yöntemin nihai kazık kapasitesini rastgele alan ile etkili bir şekilde tahmin ettiğini göstermiştir. Doğrulanan yöntem özellikle belirsizlik hesabı yapılması gerekli olan ancak yeterli sahaya özel verinin bulunmadığı durumlar için önerilmektedir. Çalışmanın literatüre, CPT tabanlı kazık kapasitesi yöntemlerine pratik bir çerçeve ile belirsizlik analizi eklemeyerek katkı sağlaması amaçlamaktadır. Ayrıca önerilen yöntemin, kısıtlı veri bulunması durumlarında kazık tasarımını kolaylaştırması hedeflenmiştir.

Keywords

Koni penetrasyon deneyi, Kazık nihai kapasitesi, Rastgele alanlar, Boşluksal değişkenlik, Kohezyonsuz zemin

Calculation of Pile Capacity in Cohesionless Soil by CPT Considering Spatial Variability

Abstract

The study aims to construct a framework for CPT based ultimate pile capacity calculation for cohesionless soils with random field theory. Cone tip resistance (qc) was taken as the spatially varying parameter with a constant mean and changing coefficients of variation. CPT profiles were simulated with random field generations, and the ultimate capacity of a single pile (Qu) was calculated with these simulations. The influence of spatial variation of qc on the variation of Qu was investigated. The proposed framework was finally verified by comparing the results of an actual CPT database and the simulated CPT profiles in the study. The results showed that the critical vertical scale of fluctuation for CPT-based pile capacity calculations was equal to one diameter of pile (dv=1D), and that the method effectively predicted the ultimate pile capacity through simulated CPT profiles with random field. The proposed method is especially recommended for cases where the uncertainty consideration is necessary, yet the site-specific data is limited. The study aims to contribute a simple framework to the methods of CPT-based pile capacity with unceratinty consideration. The propesed method aims to facilitate the pile design framework with limited available data.

Keywords

Cone penetration test, Ultimate pile capacity, Random fields, Spatial variability, Cohesionless soil

References

• 1. Phoon, K.K., Kulhawy, F.H., 1999. Characterization of Geotechnical Variability. Canadian Geotechnical Journal, 36(4), 612-624.
• 2. Ghorbani, B., Sadrossadat, E., Bazaz, J.B., Oskooei, P.R., 2018. Numerical ANFIS-based Formulation for Prediction of the Ultimate Axial Load Bearing Capacity of Piles Through CPT Data. Journal of Geotechnical and Geoenvironmental Engineering, 36(4), 2057-2076.
• 3. Padmini, D., Ilamparuthi, K., Sudheer, K.P., 2007. Ultimate Bearing Capacity Prediction of Shallow Foundations on Cohesionless Soils Using Neurofuzzy Models. Computers and Geotechnics, 35(1), 33-46.
• 4. Valikhah, F., Eslami, A., Veiskarami, M., 2019. Load-displacement Behavior of Driven Piles in Sand Using CPT-based Stress and Strain Fields. International Journal of Civil Engineering, 17(12), 1879-1893.
• 5. Wang, C.H., Osorio-Murillo, C.A., Zhu, H.H., Rubin, Y., 2017. Bayesian Approach Calibrating Transformation Model from Spatially Varied CPT Data to Regular Geotechnical Parameter. Computers and Geotechnics, 85, 262-273.
• 6. Tumay, M.T., Fakhroo, M., 1981. Pile Capacity in Soft Clays Using Electric QCPT Data. In: Proceedings of a Conference on Cone Penetration Testing and Experience. (St Louis), 434–455.
• 7. Robertson, P.K., Campanella, R.G., Davies, M.G., Sy, A., 1988. Axial Capacity of Driven Piles in Detail Soils Using CPT. Proceeding of International Symposium on Penetration Testing, ISOPT-1, Orlando. Balkema Pub., Rotterdam, 2, 919-928.
• 8. Eslami, A., Fellenius, B.H., 1997. Pile Capacity by Direct CPT and CPTu Methods Applied to 102 Case Histories. Canadian Geotechnical Journal, 34(6), 886-994.
• 9. Bustamante, M., Gianeselli L., 1982. Pile Bearing Capacity Prediction by Means of Static Penetrometer CPT. Proceedings of 2nd European Symposium on Penetration Testing, Amsterdam, 493-500.
• 10. Phoon, K.K., Kulhawy, F.H., 1999. Evaluation of Geotechnical Property Variability. Canadian Geotechnical Journal, 36(4), 625-639.
• 11. Beck, J.L., Au, S.K., 2002. Bayesian Updating of Structural Models and Reliability Using Markov Chain Monte Carlo Simulation. Journal of Engineering Mechanics, 128(4), 380-391.
• 12. Xu, D., Liu, Z., Chen, B., Xu, X., 2020. Bearing Capacity Analysis of Offshore Pipe Piles with CPTs by Considering Uncertainty. Computers and Geotechnics, 126, 103731.
• 13. Baker, J.W., Faber, M.H., 2008. Liquefaction Risk Assessment Using Geostatistics to Account for Soil Spatial Variability. Journal of Geotechnical and Geoenvironmental Engineering, 134, 14-23.
• 14. Cai, Y., Bransby, F., Gaudin, C., Uzielli, M., 2021. A Framework for the Design of Vertically Loaded Piles in Spatially Variable Soil. Computers and Geotechnics, 134, 104140.
• 15. Vanmarcke, E., 2010. Random Fields: Analysis and Synthesis. World Scientific, New Jersey, USA.
• 16. Fenton, G.A., Griffiths, D.V., 2008. Risk Assessment in Geotechnical Engineering. Wiley, New York, USA.
• 17. Cai, Y., Li, J., Li, X., Li, D., Zhang, L., 2019. Estimating Soil Resistance at Unsampled Locations Based on Limited CPT Data. Bulletin of Engineering Geology and the Environment, 78(5), 3637-3648.
• 18. Uzielli, M., Lacasse, S., Nadim, F., Phoon, K.K., 2007. Soil Variability Analysis for Geotechnical Practice. In: Proceedings of the 2nd International Workshop on Characterisation and Engineering Properties of Natural Soils (eds Tan, T.S., Phoon, K.K., Hight D.W., Leroueil, S.,), The Netherlands: Taylor and Francis, Singapore, 1653-1752.
• 19. Bong, T., Stuedlein, A.W., 2017. Spatial Variability of CPT Parameters and Silty Fines in Liquefiable Beach Sands. Journal of Geotechnical and Geoenvironmental Engineering, 143(12), 04017093.