Seismic Performance of Footings on Stone Columns Treated Dry Sand Beds
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pISSN 1226-7988, eISSN 1976-3808 www.springer.com/12205
DOI 10.1007/s12205-020-2319-9
Geotechnical Engineering
Seismic Performance of Footings on Stone Columns Treated Dry Sand Beds Priti Maheshwari
a
, Nitish Kumar Yadava, and Jagdish Prasad Sahoo
c
a
Dept. of Civil Engineering, Indian Institute of Technology Roorkee, Roorkee 247667, India Dept. of Civil Engineering, Indian Institute of Technology Kanpur, Kanpur 208 016, India
b
ARTICLE HISTORY
ABSTRACT
Received 16 December 2019 Revised 1 May 2020 Accepted 14 June 2020 Published Online 28 August 2020
An extensive experimental study has been carried out to study the seismic performance of footings on stone columns treated dry sand beds. Physical models have been prepared in a laminar shear box of size 1 m3 on the shaking table which has a single degree of freedom motion for representing horizontal shaking action under seismic vibrations. Effect of the configuration of stone columns, aspect ratio of footing, relative density of sand bed, frequency and peak ground acceleration (PGA) of cyclic input motion on vertical settlement of footing has been studied. Optimum length of stone columns has been found to lie between 13 − 16 times the diameter. Direction of shaking perpendicular to length of footing has been found to be more critical. Effect of aspect ratio has been found to be more pronounced at larger PGA. Influence of the frequency on response of footings has also been quantified.
KEYWORDS Laminar box Shaking table Stone columns Dry sand Seismic conditions Square and rectangular footings
1. Introduction Performance of stone columns in improving the bearing capacity of foundations and reducing the settlement is now very well established. In view of this, stone columns are quite widely employed in various projects pertaining to railroads, highways, airports, silos, land reclamation and various buildings. Function of stone columns varies on the basis of type of soil in which these are installed. For soft cohesive soils, these accelerate rate of consolidation and thus help in reducing the post construction settlement. On the other hand, for loose sandy soils, stone columns act as measure to densify the soil and hence result in enhancement of bearing capacity of foundation and reduction in the settlement. These aspects have been detailed by Raju and Daramalinggam (2012) along with details of various techniques for installation of stone columns in various types of soils and various application areas. Han (2015) briefly discussed various types of columnar structures used to improve the ground, installation methodology, materials adopted for its construction, load transfer mechanism and the failure pattern. Many experimental, analytical and numerical studies are available showcasing the effectiveness of stone columns and therefore performance of treated ground under different loading conditions including static as well dynamic. Some of the CORRESPONDENCE Priti Maheshwari ⓒ 2020 Korean Society of Civil Engineers
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