Steady-state strength, relative density, and fines content relationship for sands

The appropriate choice of shear strength of liquefied sands is an important component in seismic slope stability evaluation. Several factors affect the undrained steady-state strength (S_us) of sands. The steady-state strengths of 24 sandy soils were analyzed. It is shown that fines content, relative density, and friction angle play important roles affecting S_us. Fines content was found to be the major factor affecting S_us. This was verified experimentally for one sand. When the S_us data for sands were grouped into (a) relatively clean sands (<12 percent fines), (b) silty sands (12 to 50 percent fines), and (c) silts or sandy silts (>50 percent fines), at the same relative density, relatively clean sands showed the highest S_us. Silts showed the lowest S_us. Silty sands showed intermediate strengths. Lower-bound S_us-relative density relationships were established for relatively clean sands and silty sands.