Review of Proposed Stress-dilatancy Relationships and Plastic Potential Functions for Uncemented and Cemented Sands

Stress-dilatancy relationship or plastic potential function are crucial components of every elastoplastic constitutive model developed for sand or cemented sand.This is because the associated flow rule usually does not produce acceptable outcomes for sand or cemented sand.Many formulas have been introduced based on the experimental observations in conventional and advanced plasticity models in order to capture ratio of plastic volumetric strain increment to plastic deviatoric strain increment(i.e.dilatancy rate).Lack of an article that gathers these formulas is clear in the literature.Thus,this paper is an attempt to summarize plastic potentials and specially stress-dilatancy relations so far proposed for constitutive modelling of cohesionless and cemented sands.Stress-dilatancy relation is usually not the same under compression and extension conditions.Furthermore,it may also be different under loading and unloading conditions.Therefore,the focus in this paper mainly places on the proposed stress-dilatancy relations for compressive monotonic loading.Moreover because plastic potential function can be calculated by integration of stress-dilatancy relationship,more weight is allocated to stress-dilatancy relationship in this research.

Finite Element Implementation of the Exponential Drucker-Prager Plasticity Model for Adhesive Joints

This paper deals with the numerical implementation of the exponential Drucker-Parger plasticitymodel in the commercial finite element software,ABAQUS,via user subroutine UMAT for adhesive joint simulations.The influence of hydrostatic pressure on adhesive strength was investigated by a modified Arcan fixture designed particularly to induce a different state of hydrostatic pressure within an adhesive layer.The developed user subroutine UMAT,which utilizes an associated plastic flow during a plastic deformation,can provide a good agreement between the simulations and the experimental data.Better numerical stability at highly positive hydrostatic pressure loads for a very high order of exponential function can also be achieved compared to when a non-associated flow is used.

Rheological constitutive model of rock mass based on viscoplastic theory

With many major projects under construction,more and more attention is paid to rheological mechanical properties of rock mass,and extensive researches are carried out for rheological constitutive modeling of rock mass.Based on viscoplastic theory,a new rheological constitutive model is proposed.The rationality and validity of proposed model are verified through the creep test data.The results show that the rheological constitutive model based on viscoplastic theory is able to simulate the typical creep curves of rock mass and the identified parameters are reasonable.Therefore,the rheological constitutive model could be used to describe the rheological mechanical behaviour of rock mass.

Adult neurogenesis in the four-striped mice(Rhabdomys pumilio)

In this study, we investigated non-captive four-striped mice （Rhabdomys pumilio） for evidence that adult neurogenesis occurs in the adult brain of animal models in natural environment. Ki-67 （a marker for cell proliferation） and doublecortin （a marker for immature neurons） immunos-taining conifrmed that adult neurogenesis occurs in the active sites of subventricular zone of the lateral ventricle with the migratory stream to the olfactory bulb, and the subgranular zone of the dentate gyrus of the hippocampus. No Ki-67 proliferating cells were observed in the striatum substantia nigra, amygdala, cerebral cortex or dorsal vagal complex. Doublecortin-immunore-active cells were observed in the striatum, third ventricle, cerebral cortex, amygdala, olfactory bulb and along the rostral migratory stream but absent in the substantia nigra and dorsal vagal complex. The potential neurogenic sites in the four-striped mouse species could invariably lead to increased neural plasticity.

Recovery of plastics from dumpsites and landfills to prevent marine plastic pollution in Thailand

Marine plastic pollution has become a major threat to the ecosystem.The increasing production and use of plastic,combined with limitations of waste management practices,mean the leakage of plastic waste into the environment is bound to increase.This study focuses on the determination of plastic recovery potential from dumpsites and landfills in Thailand,to potentially prevent marine plastic pollution.In this study,two dumpsites were analysed wherein an average of 42% of plastic was found to be present.This value,when extrapolated for Thailand,is equivalent to 187.9 million tonnes of plastic waste in dumpsites and landfills.While there are 2380 dumpsites in the country,this study suggests that 973 of these spread over 42 provinces are located near water bodies or coastline,which should be considered as a priority.The plastic waste recovered from these dumpsites can be treated by co-fuelling in cement industries.Cement kilns can valorise plastic waste as they can reach up to 75%energy recovery from waste,which is much higher compared to traditional waste-to-energy plants.With adequate incentives and sound regulations,cement industries could help in the reduction of marine plastic pollution with controlled emissions and a very large capacity to co-fuel cement production,there is a readily available solution to manage the large volumes of solid waste generated.

Simple approach for solution of the quasi-plane-strain problem in a circular tunnel in a strain-softening rock mass considering the out-of-plane stress effect

The out-of-plane stress is sometimes the major or intermediate principal stress in a circular tunnel opening.The influences of the outof-plane stress and axial strain are often neglected in the stability analyses of tunnel excavation,which can induce significant errors in the determination of surrounding rock deformations.In this paper,the use of a simple approach is proposed to solve the quasi-plane-strain problem of circular tunneling considering the effect of the out-of-plane stress,which is deformation-dependent and influenced by the in situ stress.As the intermediate principal stress is deformation-dependent,to obtain the numerical solution of the intermediate principal stress,the quasi-plane-strain problem is defined based on assumptions that the initial axial total strain is a nonzero constant(e0)and that the axial plastic strain is nonzero.With the numerical solution for the plastic strain,obtained using the plastic potential functions based on the three-dimensional failure criteria,the formula for the intermediate principal stress can be derived using Hooke’s law.The proposed approach can be utilized to obtain the numerical solution for the intermediate principal stress,which is deformationdependent,and the numerical results can be simplified as the solution presented by Pan and Brown.The proposed approach can also be used to obtain the solution for the strain softening of the surrounding rock.To verify its validity and accuracy,the results obtained using the proposed approach are compared with the solution of Pan and Brown.In addition,parametric studies are performed to address the influences of the out-of-plane stress on the stress and displacement in the circular tunnel.