## 1 Introduction
[18] investigated the shear buckling of porous nanoplates with even, uneven and logarithmic-uneven distribution templates, by means of the Galerkin method, a novel size-dependent quasi-3D shear deformation theory and Eringen's nonlocal elasticity. Another successful application of mesh-free methods can be found in [19] for the thermal buckling response of porous sandwich plates with CNT-reinforced nanocomposite layers. At the same time, [PERSON] et al. [20] studied the nonlinear vibration and dynamic buckling of a sandwich FG porous plate reinforced by graphene platelets and resting on a Winkler-Pasternak elastic foundation, where the Galerkin method was proposed together with the fourth-order Runge-Kutta approach as theoretical and numerical tools. A conventional FSDT approach was also employed by [PERSON] et al. [21] for the study of the buckling behavior of FG graphene-reinforced porous cylindrical shells combined with the Rayleigh-Ritz numerical method, whereas [PERSON] et al. [22] applied the classical Euler-Bernoulli theory and the Galerkin method to check for the dynamic instability of FG porous arches reinforced by graphene platelets. Based on the current literature on the buckling of FG porous structures, however, most studies rely on the use of simple elastic Hooke's laws, with limited attention to the effect of pore fluid pressures stemming from poroelastic constitutive Biot's laws. In such a context, [PERSON] et al. [23; 24] proposed a closed-form solution for the axial buckling of FG-saturated, porous, rectangular, simply supported Kirchhoff plates, immersed in a piezoelectric [23] or thermal field [24], respectively. In [25], the same authors studied the axisymmetric buckling of a saturated circular porous-cellular plate as provided by FSDT. In the further work by [PERSON] et al. [26; 27], classical plate theory (CPT) or HSDT was implemented for the analysis of the buckling capacity of circular porous plates under a radial compressive load, and its sensitivity to some important poroelastic material properties. In another work, [PERSON] et al. [28] performed a buckling study of thin circular FG plates made of saturated porous-soft ferromagnetic materials in transverse magnetic fields, whereas in [29; 30], a FSDT closed solution was proposed to the buckling problem of transversely graded saturated porous plates with piezoelectric layers, and the axisymmetric post-buckling study of saturated porous circular plates under a uniform radial compression. Among moderately thick plates, [PERSON] and [PERSON] [31] assessed the buckling behavior of fluid-infiltrated porous annular sector plates, as provided by Mindlin plate theory involving fluid-saturated and fluid-free conditions. Additional buckling studies for structural members made of metalsor composite materials can be found in [32; 33; 34; 35]. The available literature, however, shows the potential application of buckling issues in many porous structures, although at the present state, a proper study of the buckling response of saturated porous rectangular plates subjected to normal and shear loads is still lacking. Based on the literature overview, it seems that the analysis of porous structures is usually based on FSDT and HSDT. Moreover, in most studies, the Hooke's law or drained condition is commonly assumed to model the porous behavior of structures. Based on the above-mentioned lacking aspects of the problem, in this work, the buckling behavior is investigated for FG-saturated porous rectangular plates subjected to a double normal and shear loads. To this end, 3D elasticity theory and [PERSON]'s constitutive law are applied, while proposing a mixed FE-DQM based on a Rayleigh-Ritz energy formulation as an efficient computational tool to solve the problem. The application of [PERSON]'s constitutive law in lieu of the simple Hooke's law provides more realistic results and conclusions, even from a practical standpoint.