Laboratory study of shear strength of loose sand in the case of Individual stone columns, Equivalent trench, and Equivalent area method

Document Type : Research Article

Authors

1 Department of Civil Engineering, Lenjan Branch, Islamic Azad University, Isfahan, Iran

2 Assistant Professor, Department of Civil Engineering, Shahr-e-Qods Branch Islamic Azad University, Tehran, Iran

Abstract

Due to the complexity of a three-dimensional (3-D) arrangement of multiple columns, a 3-D problem has been commonly converted into a two-dimensional (2-D) model, which has equivalent properties and dimensions by the equivalent trench method and the equivalent area method. These methods are used extensively in analytical and numerical studies. However, no comparison of the results of the above methods and laboratory studies has been done. Therefore, in this research, the experiments performed on reinforced soil in a large direct shear device with dimensions of 305×305×152 mm3. Experiments performed with individual stone columns (single, square and triangular arrangement), equivalent trench and equivalent area method. The effective parameters include the area replacement ratio, 8.4,12, 16.4 and 25 percent, and vertical loads (55, 75 and 100 kPa) Has been studied. Results showed that improves the stiffness of composite soils and increase in shear strength of individual stone columns (single, square and triangular arrangement) and equivalent trench and stone column arrangement had an impact on improving the shear strength of stone columns. The most increase in shear strength and stiffness values was observed for square arrangement of stone columns and the least increase was for single stone columns. Comparing the results of individual stone columns and equivalent trench in any arrangement, showed that equivalent trench arrangement could be used in two-dimensional models instead of three-dimensional individual stone columns. In the equivalent area method, there is no increase in shear strength and shear strength parameters compared to sandy bed.

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[1] B. Dheerendra , S. Nayak, R. Shivashankar, A Critical Review of Construction, Analysis and Behaviour of Stone Columns, Geotech Geol Eng J, 2013(31( 22-1.
[2] J.K. Mitchell, Soil improvement-state of the art report, in: Proceedings of the 10th international conference on soil mech. and found. Eng., Stockholm, (1981) 565–509.
[3] R.D Barksdale, R.C. Bachus, Design and Construction of Stone Column,VOL1,FHWA/RD(1983)
[4] S. Murugesan, K. Rajagopal, Studies on the behavior of single and group of geosynthetic encased granular columns, Geotech. Geoenvironmental Eng, (2010)(1)136 .139-129
[5] S. Murugesan, K. Rajagopal, Model tests on geosynthetic encased granular columns, Geosynth. Int., (6)14 .354-346(2007)
[6] S. Murugesan, Studies on the Behavior of Single and Group of Geosynthetic Encased Stone Columns,GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING, 136 .139-129 (2010)
[7] A.J. Choobbasti, A. Zahmatkesh, R. Noorzad, Performance of Stone Columns in Soft Clay: Numerical Evaluation, Geotech Geol Eng J, .684-675 (2011)29
[8] K. Deb, Modeling of granular bed-stone columnimproved soft soil, International Journal for Numerical and Analytical Methods in Geomechanics,(-1267 (2008 1288.
[9] J. Nazari Afshar, M. Ghazavi, A simple analytical method for calculation of bearing capacity of stone column, International Journal of Civil Engineering, ,(2014)(1)12 .15
[10]. A.J. Choobbasti, A. Zahmatkesh , Investigation of Bearing Capacity and Settlement of Strip Footing on Clay Reinforced with Stone Columns, Australian Journal of Basic and Applied Sciences, .3668-3658 (2010)(8)4
[11] K. Ali, J.T. Shahu, K.G. Sharma, Model tests on geosynthetic-reinforced stone columns: a comparative study. Geosynth. Int. 19 (4) (2012), 305-292.
[12] M.B.D. Elsawy, Behaviour of soft ground improved by conventional andgeogrid-encased stone columns, based on FEM study, Geosynth. Int. 20 (4) (2013), 285-276.
[13] J. Nazari afshar, N. Mehrannia, F. Kalantary,N. Ganjian, Bearing Capacity of Group of Stone Columns with Granular Blankets. International Journal of Civil Engineering(2017), doi.org/10.1007/s-0271-017-40999y.
[14]J. Nazari afshar, N. Mehrannia, F. Kalantary, Experimental Investigation on the Bearing Capacityof Stone Columns with Granular Blankets,Geotech Geol Eng J,1(36) (222-209(2017.
[15].K. Deb, N.K. Samadhiya, J.B. Namdeo, Laboratory model studies on unreinforced and geogrid-reinforced sand bed over stone column-improved soft clay, Geotextiles and Geomembranes, .196-190 (2011)(2)29
[16] M.Y. Fattah, M.A. Al-neami ,A.S. Al-Suhaily, Estimation of bearing capacity of floating group of stone columns”. Engineering Science and Technology, an International Journal, .1172-1166 (2017)(3)20
[17] M.Y. Fattah, M.Y., K.T. ShLASH ,M.J.M. Al-Waily, Stress Concentration Ratio of Model Stone Columns in Soft Clays”. Geotechnical Testing Journal, .11-1(2010)(1)34
[18] M. Ghazavi, J. Nazari Afshar,  Bearing capacity of geosynthetic encased stone columns, Geotextiles and Geomembranes, .36-26 (2013)38
[19] M. Ghazavi, A.E. Yamchi, J. Nazari Afshar, Bearing capacity of horizontally layered geosynthetic reinforced stone columns”. Geotextiles and Geomembranes, 2018(46), .318-312
[20]S. Murugesan, K. Rajagopal, Shear load tests on granular columns with and without geosynthetic encasement, Geotech. Test. J, .44-35 (2008)(1)32
[21] S.R. Mohapatra , K.R., Jitendra Sharma, Direct shear tests on geosynthetic-encased granular columns, Geotextiles and Geomembranes, 405-396 (2016)(3)44.
[22] S.W. Abusharar, J. Han, Two-dimensional deep-seated slope stability analysis of embankments over stone column-improved soft clay, Engineering Geology, 2011(120), .110-103
[23] Z. Zhang, J.  Han, G. Ye, G., Numerical investigation on factors for deep-seated slope stability of stone columnsupported embankments over soft clay, Engineering Geology, 2014(168(, .113-104
[24] J. Castro, Review Modeling Stone Columns, Materials, 7(10) (2017), doi:10.3390/ma10070782.
[25] S.A. Tan, S.  Tjahyono, Oo, Kk, G., Simplified plane-strain modeling of stone-column reinforced ground. J. Geotech. Geoenviron, 2(134) (2008), .194-185
[26]N.V. Nayak , Recent Advances in Ground Improvements by Stone Column, in In: Proceedings of Indian Geotechnical Conference,Madras (1983). India.