Experimental study on mechanical properties of loose spoil considering vertical distribution factor
JIANG Jiwei，PAN Jiajun，CHENG Zhanlin，XU Han，TAN Fan
(Key Laboratory of Geotechnical Mechanics and Engineering of The Ministry of Water Resources，Changjiang River Scientific Research Institute，Wuhan，Hubei 430010，China)
Abstract：Loose spoil slopes are naturally formed under gravity throwing(rolling) and prone to be instable for the loose structure of spoil under the circumstance of external environment. At present，there are few studies on the engineering characteristics of loose spoil. In this paper，a high loose spoil slope in a hydropower project was taken as the research object. Considering the distribution characteristics of particle configuration，four sampling lines along the vertical direction on the slope surface were arranged and a series of sampling，measurement and engineering characteristic tests of loose spoil were conducted. A new method for obtaining the natural density of loose rock and soil aggregates was proposed and verified by large-scale triaxial compression test. The research conclusions are as follows：(1) The field relative density of loose spoil is between 0.50 and 0.55，increasing along the vertical direction from top to downward. (2) Large deformation feature is the main engineering problem for loose spoil. During the process of large deformation，the spherical stress p well follows a linear relationship with the volume strain ev，whereas the bulk modulus B is linearly independent of the stress level s，only changing with the confining pressure s3. The Duncan-Zhang E-B model is more suitable for loose spoil. The failure stress ratio Rf of loose spoil is about 0.65，and loose spoil generally exhibits strain hardening characteristics. There¢s no peak deviator stress on stress-strain curves when the axial strain reaches 15%，and the mechanical mechanism of loose spoil can be summarized as large friction deformation of unstable granular materials. (3) The volume modulus B and the confining pressure s3 of loose spoil with different sampling heights have a good linear relationship，and the intercept of B on the stress coordinate axis is about equal to 0. The above conclusions are conducive to simplify calculation and to predict the deformation of loose spoil，also identifying the structure instability of loose spoil on the free surface.
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2022, Vol. 41 
