Laboratory Study On The Dynamic Characteristics Of MBT Waste

The accelerated urbanization has brought serious challenges to the treatment of municipal solid waste and environmental protection.Mechanical Biological Treatment(MBT),as an advanced municipal solid waste treatment technology,has the advantages of volume reduction,emission reduction and resource reuse,and is attracting attention from many countries.At present,scholars from different countries have mainly focused on the static properties of MBT waste,and there is a lack of research on the dynamic properties of MBT waste.The dynamic characteristics of landfills under seismic loading and their stability strongly depend on the cyclic stress-strain characteristics of the waste.An accurate assessment of the dynamic characteristics of MBT waste is crucial to the construction and safe operation of landfills.MBT waste obtained from the Hangzhou Tianziling landfill pilot project was used for the test.A cyclic triaxial test apparatus with a sine wave and strain-controlled loading was used,and considering the effects of different loading frequencies(0.1,1.5,and 1 Hz),different confining pressures(50,100,150,and 200 k Pa),and different strain amplitudes(0.05%,0.1%,0.25%,0.5%,1.25%,and 2.5%),72 sets of consolidated undrained cyclic triaxial tests were conducted,and the dynamic strength characteristics of MBT waste were systematically investigated,the results show that:(1)The morphological characteristics of hysteresis curves of MBT waste in terms of inclination,width and area characterize to some extent the stiffness,viscosity and seismic performance of MBT waste,which change with loading frequency,confining pressure and strain amplitude.(2)The dynamic stress amplitude of MBT waste increases with increasing strain amplitude and decreases with increasing number of cycles.(3)The pore water pressure of MBT waste decreases with the increase in the loading frequency,increases with the increase in the confining pressure,and increases with the increase in the strain amplitude.(4)With the increase in the number of loading cycles,the dynamic shear modulus and damping ratio of MBT waste decrease and gradually level off.(5)The dynamic shear modulus of MBT waste increases with the increase in the confining pressure and decreases with the increase in the strain amplitude.(6)The damping ratio increases with the increase in the strain amplitude,and the change in the confining pressure has less effect on the damping ratio of MBT waste.(7)The dynamic shear modulus slightly increases and the damping ratio slightly decreases as the loading frequency increases.However,the magnitude of this change is not significant.Based on the experimental results,the skeleton curve of MBT waste is fitted based on the Hardin-Drnevich model,which is less applicable when the confining pressure is large.The dynamic shear modulus of MBT waste is normalized in this paper,and since the Davidenkov model did not consider the influence of the confining pressure,a model to describe the variation of the normalized dynamic shear modulus of MBT waste under the combined effect of confining pressure and shear strain is established.The results of the consolidated undrained cyclic triaxial test of MBT waste in this paper were compared with the cyclic triaxial test results of other scholars on MSW,and the results of this study can be used as references for analyses of the dynamic stability of MBT landfills.