Consid ering the complexity of the mechanical state of compacted PTFE powder, it is proposed, herein, to model the void closure strain in isotropic specimens with a purely phenomenological first-order kinetics equation such that the volumetric strain
rate associated to void closure, [[epsilon].sub.vol] [[epsilon].sup.vc] (t), is modeled as
The temperature also has a great influence on the volumetric strain
of asphalt concrete.
Interestingly, the volumetric strain
appeared to increase at the beginning of the 10 MPa pressure application.
It can be seen from (9) that the intrinsic permeability decreases following a cubic relationship as the compressive volumetric strain
To estimate mechanical properties and volumetric strain
by means of the uniaxial tensile test, the dumbbell specimens were molded under the same molding conditions as shown in Fig.
The deviatoric stress versus axial strain curve and the volumetric strain
versus axial strain curve of gravelly soil under the draining consolidation condition are shown in Figure 4(a) and Figure 4(b), respectively.
where [[epsilon].sub.v] is the volumetric strain
, [m.sup.s.sub.1k] = [m.sup.w.sub.1k] + [m.sup.a.sub.1k] is the coefficient of volume change with respect to a change in net normal stress, and [m.sup.s.sub.2] = [m.sup.w.sub.2] + [m.sup.a.sub.2] is the coefficient of volume change with respect to a change in matric suction.
In order to evaluate mechanical properties and volumetric strain
by means of the uniaxial tensile test, the dumbbell specimens, each of whose thickness is 2 mm, width is 10 mm, and length is 50 mm in its parallel portion, were molded under the same molding conditions.
Generally, volumetric strain
[[epsilon].sub.v] and shear strain [[epsilon].sub.s] have closer relationships with spherical stress p and deviatoric stress q, respectively, and as the basic variables, spherical stress p and deviatoric stress q are usually adopted in some models including Cambridge elastic-plastic model and its modified model [18, 19].
In (19), the permeability k depends on the porosity of coal [phi], and the porosity of coal [phi] is a function of the volumetric strain
[[epsilon].sub.v] of coal-rock mass and the volumetric strain
[[epsilon].sub.s] of matrix.
Next, also based on the temperature information, the volumetric strain
is determined for each point in time and space.
In HJC model, only shear modulus G and crushing volumetric strain
pc vary with Young's modulus and can be calculated by (2) and (3).