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Geomechanics and Engineering
  Volume 17, Number 3, February28 2019 , pages 253-259

Frictional responses of concrete-to-concrete bedding planes under complex loading conditions
Wengang Dang, Heinz Konietzky and Xiang Li

    Concrete-to-concrete bedding planes (CCBP) are observed from time to time due to the multistep hardening process of the concrete materials. In this paper, a series of direct/cyclic shear tests are performed on CCBP under static and dynamic normal load conditions to study the frictional behavior effect by the shear velocities, normal impact frequencies, horizontal shear frequencies, normal impact force amplitudes, horizontal shear displacement amplitudes and normal load levels. According to the experimental results, apparent friction coefficient k (k = FShear/FNormal) shows different patterns under static and dynamic load conditions at the stable shear stage. k is nearly constant in direct shear tests under constant normal load conditions (DCNL), while it is cyclically changing with nearly constant peak value and valley value for the direct shear tests under dynamic normal load conditions (DDNL), where k increases with decreasing normal force and decreases with increasing normal force. Shear velocity has little influence on peak values of k for the DCNL tests, but increasing shear velocity leads to increasing valley values of k for DDNL tests. It is also found that, the valley values of k ascend with decreasing impact normal force amplitude in DDNL tests. The changing pattern of k for the cyclic shear tests under constant and dynamic normal load conditions (CCNL and CDNL tests) are similar, but the peak value of k is smaller in CDNL tests than that in CCNL tests. Normal load levels, shear displacement amplitudes, vertical impact frequencies, horizontal shear frequencies and normal impact force amplitudes have little influence on the changing pattern of k for the cyclic shear tests. The tests of this study provide useful data in understanding the frictional behavior of the CCBP under distinct loadings, and these findings are very important for analyzing the stability of the jointed geotechnical structures under complicated in situ stress conditions.
Key Words
    concrete-to-concrete; dynamic normal force; constant normal force; cyclic/direct shear
Wengang Dang: School of Civil Engineering, Sun Yat-sen University, Gungzhou 520275, China

Heinz Konietzky: Geotechnical Institute, TU Bergakademie Freiberg, Gustav-Zeuner-Strabe 1, Freiberg 09599, Germany

Xiang Li: School of Resources and Safety Engineering, Central South University, Changsha 410083, Hunan, China

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