Fully coupled elastoplastic hydro‐mechanical analysis of unsaturated porous media using a meshfree method

Abstract

Summary This paper presents the first application of an advanced meshfree method, ie, the edge‐based smoothed point interpolation method (ESPIM), in simulation of the coupled hydro‐mechanical behaviour of unsaturated porous media. In the proposed technique, the problem domain is spatially discretised using a triangular background mesh, and the polynomial point interpolation method combined with a simple node selection scheme is adopted for creating nodal shape functions. Smoothing domains are formed on top of the background mesh, and a constant smoothed strain, created by applying the smoothing operation over the smoothing domains, is assigned to each smoothing domain. The deformation and flow models are developed based on the equilibrium equation of the mixture, and linear momentum and mass balance equations of the fluid phases, respectively. The effective stress approach is followed to account for the coupling between the flow and deformation models. Further coupling among the phases is captured through a hysteretic soil water retention model that evolves with changes in void ratio. An advanced elastoplastic constitutive model within the context of the bounding surface plasticity theory is employed for predicting the nonlinear behaviour of soil skeleton. Time discretisation is performed by adopting a three‐point discretisation method with growing time steps to avoid temporal instabilities. A modified Newton‐Raphson framework is designed for dealing with nonlinearities of the discretised system of equations. The performance of the numerical model is examined through a number of numerical examples. The state‐of‐the‐art computational scheme developed is useful for simulation of geotechnical engineering problems involving unsaturated soils.

Investigation of the geotechnical properties and estimation of the relative density from the standard penetration test in sandy soils (Case study: north east of Iran)

“…However, the procedure to calculate the effective stress is explained here for the sake of completeness, and to be used when the soil of interest contains a considerable amount of fines. To this end, the method of effective stress (Khalili 2004;Ghaffaripour et al 2019) is used, in which in the unsaturated region of the soil we have,…”

Preconditioners for multiphase poromechanics with strong capillarity

“…It plays a critical role in unsaturated soil mechanics, 19–26 and significantly influences oil recovery predictions 27,28 . The solid deformation is intricately coupled with fluid pressures via nonlinear constitutive laws 29–33 relating the capillary pressure to degree of saturation. In some cases, the constitutive law may even display hysteresis with respect to wetting and drying 34 .…”

“…Modeling multiphase poromechanics with capillarity requires the solution of a coupled system of nonlinear algebraic equations 31,44–49 . Here, we consider fully‐implicit methods in which all governing variables are updated simultaneously.…”

Developing Pseudo Continuous Pedotransfer Functions for International Soils Measured with the Evaporation Method and the HYPROP System: I. The Soil Water Retention Curve

“…The field-scale applications of the water flow and solute transport models, and calculations of soil available water content, a widely used parameter in agronomic models, is greatly facilitated by the development of PTFs. The SWRC provides critical information about the soil moisture dynamics ("movement", "flow" and "transport") in unsaturated soils and has a wide range of applications including estimation of field capacity and soil available water [2], hydraulic conductivity [3], horizontal and vertical infiltration [4], and modeling-related problems in porous media [5,6].…”