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Abstract In view of the dynamic stability of red clay cutting bed under the ballastless track of Wuhan- Guangzhou high-speed railway，the reformed stress-controlled dynamic triaxial test instrument is utilized firstly to measure short-time and fatigue dynamic shear strain threshold，replacing the shear strain-controlled resonant column test apparatus not existing at home now. A complete set of short-time and fatigue cyclic triaxial testing program and test data processing methods are put forward，it opens up a new test way of measuring dynamic shear strain threshold. The values of short-time and fatigue dynamic shear strain threshold and its corresponding curves of red clay under 9 kinds test conditions are given. The fatigue dynamic shear strain threshold of red clay is always less than its short-time dynamic shear strain threshold，and the former is 2/10–3/10 of the latter. There are three types of curves for red clay：the stable ones，critical ones，destructive ones，and there are similar trends features in the same kind of curves under different test conditions. The influences on dynamic shear strain threshold of red clay are discussed for water content ratio and confining pressure，and the simple and practical empirical formulas of estimating dynamic shear strain threshold are provided. Based on contrastive analysis，we think it is feasible for the stress-controlled cyclic triaxial test to measure dynamic shear strain threshold replacing the shear strain-controlled resonant column test，and test results and data processing methods are correct and reasonable. The results provide valuable first-hand information for the dynamic stability evaluation of red clay subgrade of high-speed railway，as well as useful reference for similar projects.
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Received: 18 June 2010
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2011, Vol. 30 
