Mechanical Behavior of Coupled Elastoplastic Damage of Clastic Sandstone of Different Burial Depths

Abstract

Clastic sandstone is widely distributed in oil and gas reservoirs; its internal structure has many micro-defects. Under different stress environments of burial depth, significant damage evolution and plastic deformation easily occur. A series of triaxial compression tests were performed to study the coupled elastoplastic damage mechanical behavior of clastic sandstone samples at different burial depths ranging from 581.28 m to 979.82 m. Results reveal that the stress-strain responses of clastic sandstone samples exhibit significant nonlinear and softening characteristics. The mechanical behavior is due to the coupling of plastic deformation and mechanical damage. Plastic and damage internal variables cause damage stiffness degradation and plastic flow. Considering the coupling of elastoplastic damage in the loading process, an elastoplastic damage coupling model is proposed to study the mechanical behavior of different burial depth clastic sandstones. The model can effectively describe the mechanical behavior of clastic sandstone, such as the volume compression and dilatancy transformation, plastic hardening and damage softening, which are in good agreement with the experimental results. Furthermore, the mechanical behavior of the clastic sandstone shows a dependency on the confining pressure and burial depth. The load-bearing capacity and the ability to resist deformation of the clastic sandstone are improved as the confining pressure and burial depth increase. Relevant results can provide reliable basis for the safe exploitation of oil and gas engineering.

The influence of the mechanical damage on a viscothermoelastic nanobeam due to ramp-type heating under Green-Naghdi theory type-II

“…Otherwise, our conclusions would be fallacious. On the other hand, if we use the isotropic damage, then, D is independent of n, thus, the effective stresses become 30,37 :…”

“…This definition proved to be useful as several applications and problems utilized it. 30,[38][39][40][41][42] Therefore, the primary goal of this work is to analyze homogeneous, isotropic viscothermoelastic nanobeam of silicon nitride under the influence of mechanical damage. Under simply supported conditions, a thermoelasticity Green-Naghdi type-II model will be developed.…”

“…According to macroscopic phenomena, a material’s damage can be categorized as brittle, ductile, creep, and fatigue damage. 30,37 In continuum mechanics, conclusions from the description of the macroscopic behavior of a damaged material are still pending. For us, damage may unite fracture mechanics with conventional continuum mechanics.…”

“…Assessing any injured body’s cross-section, we observe an element’s area dA with unit normal vector “ n .” We may denote the area of defects by d A D . The amount of damage may take the form 30,37 :…”

“…21 Numerous writers have researched and written on the vibration and heat-transfer process of nanoresonators. 22–30 Youssef and Al-Lehaibi, for instance, looked at the vibration of a gold nanobeam that had experienced a thermal shock. 23 Kidawa, on the other hand, was interested in the effects of internal and external damping on a beam’s transverse vibrations induced by a moving heat source, and he addresses this issue using the properties of the Green functions.…”