# Static Liquefaction Assessment Combining Shear Wave Velocity, Peak Strength and Soil Grading
## 3 Specim Preparation and Testing Conditions  
The specimens were tested at different void ratios, but usually reconstituted to very loose conditions, and a wide range of confining pressures, aiming to evaluate their influence on liquefaction susceptibility. The reconstituted specimens were prepared by moist damping with a water content of 5% for all uniformly graded sands (Osorio, Algeria and Coimbra sand), 11.5% for the silt and gold tailings (Sorio, Algeria and Coimbra sand), 11.5% for the silt and gold tailings (Sorio, Algeria and Coimbra sand) and 8.75% for the mixture (an intermediate value between 11.5% and 5%). These values were obtained by testing different tamping moisture contents, with the purpose of achieving a high void ratio. The moist damping procedure was selected since (Sorio, Algeria and Coimbra sand) showed that inherent anisotropy created by specimen preparation with moist damping or funnel dry pluviation did not significantly interfere with the liquefaction susceptibility of Coimbra sand. It is also an effective, easy and relatively quick reconstitution technique that does not segregate soil particles (as opposed to the dry funnel pluviation technique), allowing the operator to control the final density much more readily (Sorio, Algeria and Coimbra sand). The moist damping reconstitution technique, used in this research, is described in detail in (Sorio, Algeria and Coimbra sand). A large set of strain and stress-controlled triaxial tests were performed to study the static liquefaction potential of these soils. Thirty-eight undrained isotropically consolidated triaxial compression tests (CIU) are presented and discussed in this paper, together with twelve CIU triaxial tests published by (Sorio, Algeria and Coimbra sand). The results of those tests are presented in Tables 2-7, where the test ID indicates the first letter of the soil (G for gold tailings, O for Osorio, S for silt, M for mixture, A for Algeria and C for Coimbra), followed by CU (undrained compression) and test number. Each triaxial test was carried out following the typical stages: percolation, saturation, consolidation and shear. In the initial stage, the specimens were percolated with de-aired water in a volume no less than twice the  
Figure 6: Grading curve and coefficient of uniformity of Coimbra sand (Sorio, Algeria and Coimbra sand, 2018). Figure 7: Grain shape of Coimbra sand. Volumetric strains were systematically evaluated and recorded using internal/local transducers (inductive hall-effect calipers) to measure axial and radial deformation until the end of the saturation phase and complementarily monitored by a volume change gauge during the consolidation and shear stages. In addition, the tests presented in this paper were carried out on triaxial apparatuses equipped with bender-extender elements (for \(S\)- and \(P\)-wave velocity measurements) at the pedestal and cap. When excited, the transmitting bender element vibrates in a direction perpendicular to the length of the element producing a shear wave, which is registered in the other bender, located at the other end of the specimen. The shear wave velocity, \(V_{S0}\), is then calculated from the ratio between the tip-to-tip travelling distance (\(d\)) and the travel time (\(t\)), based on the first wave arrival method (described in [38]), according to Equation (1):  
\[V_{S0}=\frac{d}{t} \tag{1}\]  
The shearing stage was applied under both strain-control and stress-control on \"Bishop-Wesley\" stress-path cells and classical triaxial cells, respectively, up to at least 20% axial strain, until the critical state or \"true\" liquefaction was reached. The undrained tests were typically sheared with a strain rate of 0.05 mm/min while the ones carried out on the \"Bishop-Wesley\" cells required an initial stress rate specifically determined to enable shearing during less than one day.