Dynamic Response of Model Footing on Hair Fiber-Reinforced Sand
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ORIGINAL PAPER
Dynamic Response of Model Footing on Hair Fiber-Reinforced Sand Raghvendra Sahu . Ramanathan Ayothiraman
. G. V. Ramana
Received: 21 July 2018 / Accepted: 2 June 2020 Ó Springer Nature Switzerland AG 2020
Abstract Free vibration tests were conducted on scaled model footing resting on unreinforced and hair fiber-reinforced sand to determine the dynamic characteristics of the soil-foundation system. The sand was reinforced with the random mixing of unsorted human hair fibers collected from barber shops and compacted to a relative density (RD) of 80% in the model test tank. The percentage of fiber inclusion was varied up to 1.0% by dry weight of sand. The reinforced sand was prepared with an initial moisture content of about 2–3% to obtain the consistent uniform mixing. The sand bed was filled in eight layers of 10 cm each in loose condition. Each layer was compacted using a calibrated plate vibrator to achieve the desired relative density before filling the next layer. The free vibration tests were conducted in model test tank by varying the depth of fiber reinforcement (dr) and the width of the fiber reinforcement (wr) for different percentage of fiber inclusions, viz., 0.5%, 0.75%, and 1.0%. The results demonstrated that addition of even 0.5% R. Sahu Department of Civil Engineering, ITM Group of Institutions, Gwalior, MP, India e-mail: [email protected] R. Ayothiraman (&) G. V. Ramana Department of Civil Engineering, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 16, India e-mail: [email protected] G. V. Ramana e-mail: [email protected]
human hair fiber with the sand can help in shifting the natural frequency of the soil-foundation system. Keywords Free vibration Human hair fibers Soil dynamics Sand Soil reinforcement
1 Introduction The design of foundations resting on soil and rock under machine-induced dynamic loads is of significant interest to geotechnical engineers. Dynamic loads transmitted to machine foundations are small compared to the static weight of the machine and the foundation. Typically the dynamic load transmitted to machine foundation is limited to 20% of the total mass of machine and foundation to avoid nonlinear soil behavior (Prakash and Puri 1988). Soil behavior under such small repetitive force levels is essentially elastic. In the design of machine foundations, the critical design requirements are: (1) avoiding resonance condition (operating frequency, x = natural frequency, xn) and (2) restricting the amplitude of vibration within the permissible limit (20–200 lm; Richart 1962). This limiting amplitude criterion is generally described in terms of displacement under the different operating conditions of the machine. In case, where the design does not meet above criteria, either pile foundation or ground improvement is resorted to
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Geotech Geol Eng
limit the amplitude of vibration. Ground improvement changes the stiffness of the ground and thus shifts the natural frequency and
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