An Experimental Investigation and an Elastoplastic Constitutive Model for a Porous Rock

Abstract

International audienceThis paper presents a new constitutive model for the description of elastoplastic behaviour of a porous rock. In the first section, a brief summary of the experimental investigations is presented. The data obtained show that an important coupling exists between elastic and plastic deformation, and that the confining pressure has a great influence on the yielding process of the rock. In the second section, firstly, a plastic internal variable is defined, which is able to record the influence of the stress state on the progressive yielding process. Then, based on the plastic internal variable, the respective evolutions of the subsequent yield surface, dilatancy angle and elastic parameters are studied, and the applicability of the generalized orthogonal flow rule which connects the irreversible strain increment and the yield function are analyzed. The results show that the generalized orthogonal flow rule is not suitable for the porous rock during plastic deformation. Then, based on the experimental evidence, a general formulation of the model is presented. In the third section, simulations of the conventional triaxial compression tests are performed, and the results show that the proposed model is indeed capable of capturing the main features of the mechanical behaviour of the rock. Finally, the model is extended to simulate unloading confining pressure tests, and for which it gives reasonable results

A Coupled Elastoplastic Damage Model for Clayey Rock and Its Numerical Implementation and Validation

“…The elastic damage strain dε ed ij is deduced from the change of elastic parameters during the strain hardening [17]:…”

“…Therefore, the macromechanical model has been mainly used in underground engineering and can be easily applied to simulate engineering problems, for example, determining the distribution of EDZ and extent of failure. As for plastic deformation and strainsoftening behavior for clayey rock, the modelling approaches mainly include the following [7,[14][15][16][17]: (1) the strength parameters are considered to be weakened during strain softening based on laboratory tests and field observations and (2) the damage concept is introduced into the classical continuum theory to describe the degradation of stiffness and strength of clayey rock.…”

Determination of sealing depth of in-seam boreholes for seam gas drainage based on drilling process of a drifter

“…The initial gas pressure in the coal seam is set to be 1.5 MPa. The coal is considered to be strain softening (Zhang et al, 2015;Zhang et al, 2013), and the parameters referring to the Mohr-Coulomb yield criterion are given in Table 2. The strength parameters decreased linearly to their residual values with the plastic deformation.…”

A modified NX-borehole jack with flexible loading platens

“…The modulus of deformation characterizes the deformability of the rock mass, and is among the most important parameters for geotechnical design (Feng and Jimenez, 2015;Zhang et al, 2013). Many efforts have been made to determine the modulus, both in the laboratory and the field.…”