Properties and Engineering Influence of Corewall Filter I with Different Fine Particle Contents

Abstract

The protection provided by filter I for the corewall constitutes an important safety guarantee for the impervious bodies of corewall dams. In particular, the fine particle content (the content of particles < 0.075 mm in size) of filter I provides a filter protection effect for the corewall. Furthermore, this also determines its own drainage characteristics as an important gradation requirement for filter design. In practical engineering, due to the nature of the aggregate source, the crushing and screening process, and rolling construction, the fine particle content may exceed relevant standards. Relying on the field measured gradation envelope of the filter of a gravelly earth core rockfill dam project, this study prepared two classes of filter I (i.e., filter I of class I with a fine particle content of 8%, and filter I of class II with a fine particle content of 12%). Permeability property test, large-scale compression test, large-scale static triaxial test, and large-scale dynamic triaxial test were conducted. Furthermore, dynamic finite-element calculation of the dam under seismic action was performed, and the anti-seismic liquefaction property of the filter was analyzed. According to the permeability property test, the permeability coefficients of the two classes of filter I were both 1∼5×10−3 cm/s. Lower content of particles < 0.075 mm in size increased the permeability coefficient. According to the mechanical test, the stress-strain test curves of both classes of filter I presented nonlinearity, compressive hardening, elastoplasticity, and other general laws. The strength index and deformation resistance both increased with increasing relative density. Under the same relative density, both strength index and deformation resistance declined with increasing fine particle content. According to the dynamic finite-element anti-seismic liquefaction analysis on filter I of class II (with a content of particles < 0.075 mm in size of 12%) under seismic action, the liquefaction degree had a maximum value of 0.58 (less than 0.8), and the anti-liquefaction safety coefficient had a minimum value of 1.72, which would not trigger liquefaction of filter I. This experimental study and computational analysis offers references for the exploration of the gradation design of filter I of earth core rockfill dams and investigates the related engineering influence.