Field Pullout Testing and Performance Evaluation of GFRP Soil Nails

Hong-Hu Zhu 1, Jian-Hua Yin, M. ASCE 2; Albert T. Yeung, F. ASCE 3; and Wei Jin 4
1 School of Earth Sciences and Engineering, Nanjing University; formerly,  Department of Civil and Structural Engineering, The Hong Kong Polytechnic University
2 Department of Civil and Structural Engineering, The Hong Kong Polytechnic University
3 Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong
4 Department of Electrical Engineering, The Hong Kong Polytechnic University
Journal of Geotechnical and Geoenvironmental Engineering, 2010.
Submitted 24 June 2009; accepted 6 October 2010; posted ahead of print 8 October 2010


ABSTRACT: Glass fiber reinforced polymer (GFRP) materials provides practical solutions to corrosion and site maneuvering problems for civil infrastructures using conventional steel bars as reinforcements. In this study, the feasibility of using GFRP soil nails for slope stabilization is evaluated. The GFRP soil nail system consists of a GFRP pipe installed by the double grouting technique. Two field-scale pullout tests were performed at a slope site. Fiber Bragg grating (FBG) sensors, strain gauges, linear variable displacement transformers (LVDTs), and a load cell were used to measure axial strain distributions and pullout force-displacement relationships during testing. The pullout test results of steel soil nails at another slope site are also presented for comparison. It is proven that the load transfer mechanisms of GFRP and steel soil nails have certain difference. Based on these test results, a simplified model using a hyperbolic shear stress-strain relationship was developed to describe the pullout performance of the GFRP soil nail. A parametric study was conducted using this model to study some factors affecting the pullout behavior of GFRP soil nails, including nail diameter, shear resistance of soil-grout interface, and ratio of interface shear coefficient to the Young's modulus of the nail. The results indicate that the GFRP soil nail may exhibit excessive pullout displacement and thus a lower allowable pullout resistance in comparison with the steel soil nail.

KEYWORDS: soil nail, glass fiber reinforced polymer (GFRP), pullout test, fiber Bragg grating (FBG)

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