Date of Award

1993

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Civil and Environmental Engineering

First Advisor

Yalcin B. Acar

Second Advisor

Mehmet T. Tumay

Abstract

An understanding of the effect of cementation on geotechnical properties of soil deposits is gaining increasing attention in the profession. When low levels of cementation in sands are neglected, pile capacity and slope stability are underestimated and liquefaction is overestimated. It is essential to devise schemes to identify cementation in soil investigations and develop methods in evaluating engineering characteristics of cemented deposits. The objective of this study is to develop a method to identify cementation in sands and assess the engineering characteristics of cemented sand deposits using the cone penetration testing scheme. The scope of the study includes evaluation of the effect of cementation on cone penetration testing (experimental model) and comparison of these experimental results with theoretical models of penetration mechanism in cemented sands. Existing models based upon the bearing capacity theories and cavity expansion models are utilized in theoretical modeling. A constitutive model is developed for strength-deformation behavior of cemented sands and is used in theoretical modeling. Artificially cemented Monterey No. 0/30 is used in the calibration chamber study. A total of 30 tests are conducted at three ranges of relative density (45-55, 65-75 and above 85%), three confining pressures (100, 200 and 300 kPa) and three different cement content (0, 1 and 2%). Pluviation method is used for specimen preparation. Specimens are cured for 7 days, transferred into the flexible wall calibration chamber and then consolidated under $K\sb0$ conditions. Penetration testing was conducted with a 1.27 cm diameter miniature cone. Separate drained triaxial tests provided the necessary parameters for strength-deformation modeling of cemented sands. The experimental model results coupled with the theoretical model predictions provide a semi-empirical and empirical schemes for evaluating engineering characteristics of cemented sand deposits. An assessment of the applicability of these models in prediction of cementation in such deposits is also provided. The results indicate that tip resistance and sleeve friction in cone penetration testing provide a reasonable assessment of cementation. The charts and the analysis method provided can be used to estimate the engineering characteristics of such deposits.

Pages

383

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