A New Dynamic Direct Shear Testing Device on Rock Joints
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TECHNICAL NOTE
A New Dynamic Direct Shear Testing Device on Rock Joints Shengwen Qi1,2,3 · Bowen Zheng1,2,3 · Faquan Wu4 · Xiaolin Huang1,2,3 · Songfeng Guo1,2,3 · Zhifa Zhan5 · Yu Zou1,2,3 · Giovanni Barla6 Received: 17 January 2020 / Accepted: 9 June 2020 © Springer-Verlag GmbH Austria, part of Springer Nature 2020
Keywords Direct shear · Dynamic load · Cyclic load · New apparatus · Constant normal load · Constant normal stiffness
1 Introduction Discontinuities, i.e., joints, bedding planes, contacts and faults (ISRM 2007), are widely developed in rock masses. The assessment of the shear strength of these discontinuities is very important for evaluating the stability of rock structures, so lots of researches have been carried out on this aspect (i.e., Patton 1966; Barton 1973; Barton and Choubey 1977; Grasselli and Egger 2003; Guo and Qi 2015; Zheng and Qi 2016). In addition to static shear loads, also dynamic shear loads, e.g., seismic wave loads, which are rapid and cyclic loads, need to be considered (i.e., Li et al. 2011, 2014). The shear strength of discontinuities under dynamic cyclic shearing is expected to decrease gradually (i.e., Crawford and Curran 1981). Therefore, a rock structure which is stable under static loads may move or slide along the discontinuities and co-seismic landslides or other instabilities may occur during strong earthquakes (i.e., Qi et al. 2010, 2011, 2015). Hence, the shear behavior of discontinuities under dynamic cyclic shearing should be properly investigated (Dang et al. 2016; Fathi et al. 2016).
* Shengwen Qi [email protected] 1
Key Laboratory of Shale Gas and Geoengineering, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
2
Innovation Academy for Earth Science, Chinese Academy of Sciences, Beijing, China
3
University of Chinese Academy of Sciences, Beijing, China
4
Shaoxing University, Shaoxing, China
5
China Highway Engineering Consulting Corporation, Beijing, China
6
Politecnico di Torino, Torino, Italy
Laboratory shear testing has been widely used to investigate the shear behavior of discontinuities under different shear rate conditions (Schneider 1977; Crawford and Curran 1981; Li et al. 2006; Mehrishal et al. 2016; Kleepmek et al. 2016). The dynamic direct shear apparatus used to test the dynamic shear behavior of discontinuities is significantly different from the static direct shear apparatus adopted in the references i.e., Cen and Huang (2017), Huang and Zhu (2018), Zhu and Huang (2019). In addition to the basic equipment, i.e., the normal and tangential loading devices, the shear box, the hydraulic control device and the data acquisition and processing system (Barla et al. 2010; Huang and Zhu 2019), a servo oil source system with a large flow and accumulator is needed. The maximal shear rate and frequency are requested to be in the range 600–1000 mm/s and 10–20 Hz, respectively (Hu et al. 1996). At the same time, the specimens should be large enough to simulate the seismic wave loads properly as
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