Coupled hydro-mechanical influence on hydraulic conductivity of well-graded sandy gravel

Abstract

In embankment dams and hydraulic structures, locally excavated sandy gravel is extensively used as the major rockfill material for its relatively low cost. As an increasing number of hydraulic buildings are designed with higher height and are constructed at steep valleys as well as turbulent waterways, the hydraulic conductivity performance of this building material becomes a vital parameter to evaluate the structure safety against seepage. This paper focuses on the changes of hydraulic conductivity induced by coupling effect of hydraulic load and mechanical behavior. Multi-stage hydraulic heads as well as various stress states are achieved by a newly developed apparatus to replicate infield sophisticated conditions. Sufficient specimen size is provided so that the well-graded test soil remains its natural gradation during constant water head permeability tests. The outflow of soil specimen was measured for each test. It is revealed that both the hydraulic and the mechanical effect result in a global decrease of gravelly material. A threshold of more than 6 MPa exists, indicating that the impact of further stress loading remains to a limited extent. In addition, no observation of obvious seepage failure illustrates that both hydraulic and mechanical loads are favorable to seepage prevention and corresponding countermeasures.