Investigation of Shear Strength of Prefailed Overconsolidated Clayey Slopes by Fast Shearing

Öz

Clayey soils might be investigated since the days of the beginning of the geotechnical science. The behaviour of the clays under different loading and environmental conditions is still under investigation. This study is dealing with the pre-failed soil slopes consist of high and low plastic overconsolidated clays. After failure of a slope, the thought of “soil strength reduces its residual strength” has found general acceptance and residual strength is applied to the calculations of the stability of pre-failed slopes. At this point, the question comes to the minds; if the slope formed with clayey soil or more specifically, high or low plastic overconsolidated clays, what would be the difference in shear behaviour after failure? That is the main point of this study. In the tests, Kaolin clay is used for low plastic samples and 50% Kaolin + 50% Bentonite in weight are used for high plastic clay samples. As testing steps; first, samples are over-consolidated, then sheared until their residual strengths and finally tested after a certain time at the highest rate of shearing of the apparatus. At the end of the 30 (thirty) tests, the results are obtained as expected. High plastic samples could serve lower strength values under the same normal stress; however, the interesting result was about the difference in values between the residual strength and the shear strength at a higher rate of shearing.

Anahtar Kelimeler

• Pre-failed slope
• High and low Plastic clayey soil
• Residual and shear strength
• Overconsolidation
• Slope stability
• Fast shearing test

Önceden Kaymış Aşırı Konsolide Killi Şevlerin Kesme Mukavemetinin Hızlı Kesme Yöntemi ile Araştırılması

Öz

Killi zeminler geoteknik biliminin başlangıcından beri incelenmekte olabilir, ancak kilin farklı yükleme durumlarında ve farklı şartlardaki davranışı halen incelenmektedir. Bu çalışma, yüksek ya da düşük plastitedeki killerden oluşmuş önceden kaymış şevlerle ilgilidir. Kaymadan sonra, “zeminin gücü reziduel değere düşer” düşüncesi genel anlamda kabul görmüş ve önceden kaymış şevlerin kararlılık hesaplarında bu değer kullanılmıştır. Bu noktada, eğer şev kilden oluşuyorsa sorusu akıllara gelebilir; daha detaylı düşünürsek, eğer şev yüksek ya da düşük plastisiteli aşırı konsolide killerden oluşuyorsa kesme davranışında ne gibi farklılıklar olabilir? İşte bu çalışmanın ana noktası budur. Deneylerde, düşük plastisiteli örnekler için Kaolin, yüksek plastisiteli örnekler icin ise ağırlıkça %50 Kaolin ve %50 Bentonit karışımı kullanılmıştır. Deney aşamaları olarak, önce örnekler aşırı konsolide edilir, daha sonra reziduel değerlerine kadar kesme deneyi sürdürülür ve son olarak da hızlı kesme deneyi gerçekleştirilir. 30 (otuz) testin sonunda sonuçlar beklendiği gibi elde edilir. Yüksek plastik numuneler aynı normal stres altında daha düşük mukavemet değerleri vermektedir; asıl ilginç sonuç, reziduel mukavemet ile daha yüksek bir kesme hızındaki kesme mukavemeti arasındaki değerler arasındaki farktır.

Anahtar Kelimeler

• Önceden kaymış şev
• Yüksek ve alçak plastiliteli killi toprak
• Reziduel ve kesme kuvveti
• Aşırı konsolide
• Şev kararlılığı
• Hızlı kesme testi

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