Ground Improvement Technique
APPLICATION OF SEISMIC CONE FOR CHARACTERIZATION OF GROUND IMPROVED BY VIBRO-REPLACEMENT by ALI AMINI ASALEMI M.A.Sc., University of Science and Technology, Tehran, Iran B.Sc., University of Science and Technology, Tehran, Iran A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES (Civil Engineering)
THE UNIVERSITY OF BRITISH COLUMBIA December 2006 © ALI AMINI ASALEMI, 2006
ABSTRACT The objective of this thesis was to gain a better understanding of the physical process of ground improvement by vibro-replacement and of how the induced changes in ground conditions affect the interpretation of seismic cone penetration testing used to assess its effectiveness. This was achieved by a combination of field testing and monitoring supported by numerical modelling of both the vibro-replacement process and of in situ testing. Field measurements were made of the input motions created by the vibrator and the induced response of the ground. The measured vibrator motions were input to a numerical model of the soil mass and the results of the analysis were compared to the measured data. The results of seismic cone testing before and after treatment at 15 sites and existing chamber test data were analyzed and additional numerical modelling of seismic cone testing in the post-treatment ground conditions was carried out. The study showed that the ground response to the vibrator attenuated with distance due to geometrical spreading and material damping. The direction of the principal horizontal acceleration changed with distance from the vibrator. It was shown that vibro-replacement creates a young, heterogeneous deposit comprising the native soil with increases in density and horizontal stress varying with distance from stiffer stone columns. If the induced heterogeneity is neglected when interpreting in situ test results, there will be some over-estimation of the soil properties close to the
THE UNIVERSITY OF BRITISH COLUMBIA December 2006 © ALI AMINI ASALEMI, 2006
ABSTRACT The objective of this thesis was to gain a better understanding of the physical process of ground improvement by vibro-replacement and of how the induced changes in ground conditions affect the interpretation of seismic cone penetration testing used to assess its effectiveness. This was achieved by a combination of field testing and monitoring supported by numerical modelling of both the vibro-replacement process and of in situ testing. Field measurements were made of the input motions created by the vibrator and the induced response of the ground. The measured vibrator motions were input to a numerical model of the soil mass and the results of the analysis were compared to the measured data. The results of seismic cone testing before and after treatment at 15 sites and existing chamber test data were analyzed and additional numerical modelling of seismic cone testing in the post-treatment ground conditions was carried out. The study showed that the ground response to the vibrator attenuated with distance due to geometrical spreading and material damping. The direction of the principal horizontal acceleration changed with distance from the vibrator. It was shown that vibro-replacement creates a young, heterogeneous deposit comprising the native soil with increases in density and horizontal stress varying with distance from stiffer stone columns. If the induced heterogeneity is neglected when interpreting in situ test results, there will be some over-estimation of the soil properties close to the