International Journal of Earth Sciences and Engineering

B. G. Shivaprakash ¹, S. V. Dinesh ¹

Affiliations
1 Department of Civil Engineering, Siddaganga Institute of Technology, Tumkur, Karnataka, IN

Abstract

This paper presents the dynamic properties of sand-fines mixtures based on the results of undrained cyclic triaxial tests. The sand was obtained from Sabarmati River, and three types of fines F1, F2, and F3 were obtained from locally available fine grained soils i.e. Suddha soil, Black cotton soil, and Bentonite soil. Sand-fines mixtures of wide range of plasticity from non-plastic to highly plastic mixture with PI=86 were prepared using the fines passing 75μ size. The initial shear moduli of all sand-fines mixtures are examined in terms of fines content and conventional plasticity index (IP). In the present investigation, a term equivalent plasticity index (IP*) has been defined by considering the plasticity characteristics of soil passing 2 mm size IS sieve on the same lines of. There is better correlation between the initial shear modulus of sand-fines mixtures and equivalent plasticity index (IP*) compared to conventional plasticity index (IP). An empirical equation for predicting initial shear modulus is proposed based on equivalent plasticity index and mean-effective stress.

Keywords

Dynamic Properties, Shear Modulus, Plasticity Index, Equivalent Plasticity Index, Sand-Fines Mixture.

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B. G. Shivaprakash ¹, S. V. Dinesh ¹

Affiliations
1 Department of Civil Engineering, Siddaganga Institute of Technology, Tumkur, Karnataka, IN

Abstract

Geotechnical earthquake engineers have been studying the ground response of deep soil deposits under earthquake loadings. The site amplification is correlated not only to soil thickness, but, also to soil properties such as shear modulus, damping and depth of half-space. There are no clear guidelines on the depth at which input motion is to be given. This paper presents the effect of depth of input for site response analysis of deep soil deposits. The influence of depth to the half-space is studied by conducting the 1D response analysis for soil column data for West Tennessee and Charleston site soil profiles. Two bedrock motions are given as input at various depths starting from 40, 60, 80,100, 120, 140, 160, 180, 200, 300, 400, and 500 m. From the limited analysis, it is observed that the variation of PSA and PGA values beyond 300 m are constant. Hence, the effective depth of soil column for the response analysis of deep soils shall be taken as 300-400 m.

Keywords

Earthquake, Input Bedrock Motion, 1D Site Response Analysis, Response Spectrum.

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