# Static Liquefaction Assessment Combining Shear Wave Velocity, Peak Strength and Soil Grading
## 1 Introduction  
Static liquefaction has been identified in several tailings dam failures [1; 2; 3] where loose saturated soils are deposited. These accidents resulted in severe consequences in terms of casualties, damages, environmental impacts and serious disruptions in the raw materials supply. The increasing number of these accidents has prompted more research in this area aimed at enhancing the design of these geotechnical structures and contributing to their sustainable construction and exploration. A large number of these facilities are immobilized and have to be removed (decommissioned) due to the high levels of failure probability. This condition demands for particularly sensitive deconstruction techniques that require a very accurate knowledge of the consequences of the necessary interventions on these highly unstable materials. The assessment of soil liquefaction potential using laboratory techniques was initiated by [PERSON] in 1936 [4], who proposed the critical void ratio line (CVR), nowadays known as the critical state line (CSL), as a boundary separating liquefiable from non-liquefiable soils. Later, [PERSON] and [PERSON] (1985) [5] proposed the state parameter, \(\psi\), assuming the existence of a unique CSL. This parameter is usually correlated, for static liquefaction assessment purposes, with the britteness index, \(I_{B}\), which measures the normalized degree of strain softening of a contractive soil using the peak and minimum shear strengths, \(\sigma^{\prime}\)_a(peak)_ and \(\sigma^{\prime}\)_d(min)_, respectively (e.g., [6; 7; 8]). Despite being widely consistent, both parameters are dependent on the soil type. Moreover, the state parameter also requires the previous laboratory determination of the position of the CSL. Nevertheless, in order to provide a universal framework, ref. [7] after [9], proposed the normalization of the state parameter as a ratio between \(\psi\) and the slope of the CSL, \(\lambda\) (\(\psi/\lambda\)). Shear wave velocities were also used to assess soil liquefaction potential (especially cyclic liquefaction), which was initiated by [PERSON] et al. (1988) [10] and later adapted by [11] through the correlation of the normalized small-strain shear wave velocity with the cyclic resistance ratio, CRR. In the case of static liquefaction, the combination of both strength and stiffness measurements, using the seismic cone penetrometer test (SCPTU), for example, was found to effectively predict liquefaction response as it has a good correlation with the state parameter [12; 13; 14]. This combination also has the advantage of distinguishing between recent and/or aged or cemented deposits [15]. Its successful combination was already somewhat expected as both variables are controlled by the confining stress, void ratio, stress history, soil structure and geological age [16; 17; 18] and are also correlated with critical state parameters, which governs soil liquefaction response. [PERSON] et al. (2013) [19] used triaxial compression and extension tests with bender elements to develop a framework for the assessment of static liquefaction on gold tailings, showing that peak undrained deviatoric stress and shear wave velocity are correlated. More recently, [PERSON] and [PERSON] (2021) [20] used the normalized shear wave velocity to distinguish between liquefiable and non-liquefiable soils, proposing an empirical method to evaluate the onset of instability and the post-liquefaction strength of tailings using shear wave velocity. However, it is assumed that this relationship is still soil-dependent, as demonstrated by [21]. [PERSON] et al. (2019) [22] shows that shear wave velocity in granular soils is significantly affected by the uniformity coefficient and fines content, which affect liquefaction potential [23]. Moreover, [PERSON] and [PERSON] (2004) [24] and [PERSON] et al. (2006) [25] demonstrated that particle size and shape can be correlated with different critical state parameters as the macro scale behavior of the soil results from particle-level interactions.