Determination of Initial-Shear-Stress Impact on Ramsar-Sand Liquefaction Susceptibility through Monotonic Triaxial Testing  
[PERSON]  
1 Department of Civil Engineering, University College of Rouzbahan, Sari 3994548179, Iran; [EMAIL_ADDRESS] (M.N. ); [EMAIL_ADDRESS] (S.S.)1  
[PERSON]  
2 Civil Engineering Program, Middle East Technical University, Northern Cyprus Campus, Kalkanli, Guzelyurt, North Cyprus, via Mersin 10, Turkey; [EMAIL_ADDRESS]  
[PERSON]  
3 Civil Engineering Department, Near East University, Lefkosa 99138, Mersin 10, Turkey
the treatment of anisotropically consolidated samples. [PERSON] et al. [9] observed that this method plays a significant role in stimulating the liquefaction susceptibility of the soil condition on a slope subjected to high shear strain or under a structure that can tolerate high shear stresses. [PERSON] [7] performed several static tests on anisotropically and isotropically consolidated undrained samples and distinguished three different types of behavior for sands, as shown in Figure 1.  
On the other hand, a conventional triaxial test cannot represent a real site stress condition where the direction of the major principal stress may change according to various loading conditions such as wave load, traffic load or earthquake load. However, the mechanism of liquefaction is intensively related to these loading conditions. It has been widely reported in the literature that the rotation of the major principal stress orientation can accelerate the development of pore water pressure and can lead to liquefaction of sandy soils [10; 11]. Numerous studies [8; 12; 13; 14; 15; 16; 17; 18] have concluded that the initial state expressed in terms of the initial void ratio \(\mathrm{e_{0}}\) as well as the initial effective mean stress \(\mathrm{p^{\prime}}_{0}\) significantly affect undrained soil response. The influence of the initial shear stress on the liquefaction susceptibility has been investigated in recent decades. [PERSON] and [PERSON] [19] observed that in samples consolidated to principal effective stress ratios (K' of 1.5, 2.0, and 2.25, the increase in deviator stress under undrained conditions required to initiate liquefaction were approximately 0.6, 0.25, and 0.13 ksc (59, 25, and 13 kPa), respectively. They reported that the resistance to static liquefaction in these samples decreased significantly as the initial shear stress level increased. Later contributions by [PERSON] and [PERSON] [20], and [PERSON] and [PERSON] [21] demonstrated that the presence of the initial shear stress ratio (\(\alpha\)) improved liquefaction resistance at high relative densities (55-70%), whereas the effect was less pronounced at low relative densities (approximately 35%). According to recent research [22; 23], triaxial tests performed at higher initial shear stress parameter values could create both improving and aggravating effects on the liquefaction susceptibility of loose or very dense sands, depending on the given range of the initial shear stress ratio (\(\alpha\)). Soil samples under shearing up to large strains tend to reach a state of continuous deformation under constant shear (q) and normal stresses (p'), where such occurrence is known as the ultimate  
Figure 1: Liquefaction, limited liquefaction and dilation in static loading tests 7 [3]. steady-state line (SSL). Soil at the SSL exhibits a relationship between the ultimate values of the deviatoric stress and mean effective principal stress. Therefore, soil behavior can be predicted by expressing the state of the effective confining stress and defining the location of this point relative to the steady-state line. [PERSON] and [PERSON] [PERSON] and [PERSON] (2018) observed that in addition to the steady-state line position being a unique soil property, the inclination of steady-state lines varies extensively, even for apparently similar soils. The steady-state concept and SSL were further described by other studies [1,7,24]. [PERSON] et al.