ESTIMATION OF UNCONFINED COMPRESSIVE STRENGTH OF CEMENT TREATED SOILS BASED ON MULTI-POINT NEEDLE PENETRATION RESISTANCE

Abstract

 Proper quality control and assurance are required for engineering practices which deal with cement treated grounds since the strength quality is affected by the variability of soil properties as well as distribution of cement particle. Conventional quality control and assurance by means of the unconfined compression test is normally to evaluate an average strength of specimens sampled from discrete points in cement treated ground. On the other hand, needle penetration test can confirm the presence or absence of weak zones in specimen and a continuous strength distribution that cannot be measured solely by the unconfined compression tests. Therefore, the purpose of this study is to propose more reliable strength evaluation method taking advantage of needle penetration tests and to offer advanced conversion formula to induce unconfined compressive strength from the needle penetration resistance. Based on multi-point measurements with a desktop-type needle penetration apparatus, we first propose a new conceptual formula to estimate unconfined compressive strength. To verify the proposed concept, we then conduct needle penetration tests on cement-treated soils with different 51 specimens prepared in various strength ranges. Finally, coefficients of the conceptual formula are identified, and applicability and validity of the formula are discussed.