Assessing the effects of confining stress state on the mobilization of axial compressive resistance for a single aggregate pier/


Thesis Type: Postgraduate

Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Faculty of Engineering, Department of Civil Engineering, Turkey

Approval Date: 2014

Student: ALPARSLAN DOĞAN

Supervisor: KEMAL ÖNDER ÇETİN

Abstract:

Aggaregate piers are widely used to enhance the performance of cohesionless and cohesive foundations soils. It is an effective and economical solution to several geotechnical engineering problems including insufficient bearing capacity, excessive settlements, slope instability and liquefaction. The performance of stone columns is governed by a number of factors including installation procedure, area replacement ratio, column length, shear strength characteristics of the column and native soil characteristics. Within the scope of this thesis, the effect of construction induced confining stresses on the mobilization of axial compressive resistance of a single aggregate pier is examined. For this purpose, series of finite element based numerical simulations were performed by modeling piers of different length to diameter (L/D) and cavity expansion ratios (Δr/R0). Both components of resistance including shaft friction and end bearing were evaluated by utilizing an axisymmetric finite element model. Finally, normalized resistance vs. normalized settlement curves were developed for piers of different length to diameter and cavity expansion ratios to demonstrate mobilization of the axial resistance. By careful invesitgation of analysis results, it was found that aggregate pier capacity increases as the confining stress increases. Also, an improvement in the settlement was observed through confining stress increase for a specified value of axial compressive stress.