ABSTRACT
An important factor in evaluating the stability of hydraulic fills against flow sliding is the undrained steady state strength mobilized in the field. This paper proposes an empirical relationship between three factors: the undrained strength back-calculated from fills which failed by flow sliding, equivalent clean sand normalized blow count values and soil specific parameters from steady state laboratory testing. It is shown that Suo, which is a reference value of steady-state strength at maximum void ratio, is an important soil parameter.
A methodology to evaluate the soil’s susceptibility to develop liquefaction flow failures once strain softening is triggered in the field is presented based on case-histories. The proposed approach gives undrained strengths close to the post-liquefaction strengths obtained from simple shear tests for the foundation sand at Duncan Dam. These values are much higher than those inferred from the original Seed’s relationship because the new method incorporates soil specific parameters obtained from laboratory testing.
The proposed method offers also an explanation for the performance of many artificial sand islands in the Beaufort Sea, indicates the extreme sensitivity of Suo to soil type and the usefulness of Suo for assessing the potential strength loss of soils for use in safety assessments of existing hydraulic fills.
