A constitutive model for frozen soil based on rate-dependent damage evolution

Growing awareness of sustainability in the landfill cover system has increased the use of biochar amendment for degraded landfill surface soils. Hydraulic and vegetative benefits of biochar on cover soil have been studied in the past, while ignoring mechanical characteristics, which is important to understand progressive failure of landfill infrastructure. In this study, the mechanical characteristics of four soil–biochar composites were investigated by conducting 81 unconfined compressive strength test. The results based on four in-house produced biochar were used to study the effect of compaction state (density, moisture content) and biochar percentage (5% and 10%) on unconfined compressive strength of soil–biochar. The ductility of soil–biochar was investigated for all the four biochars. Results from this study indicate a contrasting observation of strength gain depending on the type of biochar. The unconfined compressive strength of soil–biochar is potentially influenced by the different surface functional groups of biochar (hydrophilicity/hydrophobicity) and soil-biochar interlocking. It was noted that the peanut shell biochar gave comparable unconfined compressive strength of soil–biochar with that of bare soil for different compaction state. However, a diminution in the unconfined compressive strength was observed for all the other three soil–biochar sourced from water hyacinth, saw dust, and poultry litter. The study indicates that the use of biochar in soils does not ensure an improvement in the strength of soil–biochar. Enhancement in ductility was found for all the four soil–biochar irrespective of compaction state. Improvement in ductility was maximum when the soil–biochar is compacted at the dry state of optimum. Plant-based biochar has higher potency to increase the ductility of soil as compared to the animal-based biochar. Our study identifies peanut shell biochar ideal for landfill cover amendment material, considering its mechanical characteristics and design criterion. Soil biochar composite from water hyacinth, saw dust, and poultry litter can be used for potential application in green-infrastructure.

Section: Future Workmentioning

confidence: 99%

Influence of biochar from animal and plant origin on the compressive strength characteristics of degraded landfill surface soils

Bora

Bordoloi

Kumar

et al. 2020

“…In the authors' earlier work (Cao et al., 2018), by considering the damage evolution as the propagation of micro-cracks and micro-defects dependent on the stress and strain rate, the strain rate term is introduced into the damage evolution equation. Referring to some relevant research on metals and concrete, a damage evolution equation for frozen soil was established where the thermal activation theory is used to explain the damage evolution law of frozen soil.…”

Section: Dynamic Constitutive Modelmentioning

confidence: 99%

“…(2018) studied the damage evolution equation and constitutive model of rock based on the statistical strength theory, Lemaitre strain equivalent assumption, and damage mechanics, in order to establish a damage evolution equation for chemical freeze-thaw sandstone under a load. Cao et al. (2018) took the strain and strain rates into account in order to establish a rate-dependent damage evolution law under the assumption of equivalent strain.…”

Section: Introductionmentioning

confidence: 99%

SHPB test analysis and a constitutive model for frozen soil under multiaxial loading

Zhu

Cao

2019

Self Cite

A split Hopkinson pressure bar is adopted to test the dynamic mechanical behavior of frozen soil at different temperatures and high strain rates. An aluminum sleeve is used as a passive confining pressure device. Comparing the results of this test with those under the uniaxial state shows that besides the temperature and strain rate effects, frozen soil exhibits obvious stress strengthening characteristics. In addition, the failure mode is viscoplastic instead of brittle. If frozen soil is regarded as a particle-reinforced composite material, then the debonding damage of ice particles and rate-dependent damage of soil matrix are taken into account. Based on this, a dynamic constitutive model of frozen soil under a multiaxial state is proposed. The theoretical results of the model agree well with the experimental results, verifying the rationality and applicability of the model.

“…Thus, numerous scientific efforts have been devoted to studying the creep strength, time-dependent deformation, damage propagation, failure characteristics and theoretical model in uniaxial/triaxial, bending, and shear rheological tests (Challamel et al, 2005;Cruden, 1971;Itoˆand Sasajima, 1987;Mishra and Verma, 2015;Nadimi and Shahriar, 2014;Rassouli and Zoback, 2015;Tomanovic, 2006;Tsai et al, 2008). In recent years, for special engineering problems, many researchers began to study the rheological properties of soft rock (Cao et al, 2016;Mansouri and Ajalloeian, 2018), rock containing pre-existing flaws (Shi et al, 2019;Wu et al, 2018), frozen soil (Cao et al, 2018;Hou et al, 2018;Kostina et al, 2018;Zhou et al, 2018;Zhu et al, 2019) and frozen rock (Ladanyi, 2006;Song et al, 2019) due to the complex and variable occurrence, environment, lithology and structure of rock. Wang et al (2014) investigated the creep damage behavior of rock salt, gave the evolution rule of deformation and failure in three stages, and evaluated the long-term strength of rock salt.…”

Section: Introductionmentioning

confidence: 99%

Study on triaxial creep behavior and the damage constitutive model of red sandstone containing a single ice-filled flaw

Bai

Shan

Han

et al. 2020

The freezing method is widely used in the construction of vertical shafts in water-rich strata. The formed frozen rock wall is often involved in the creep process, and in particular, the creep behavior of frozen fissured rock mass poses a great threat to construction safety. To better understand the creep instability law of ice-filled, fractured red sandstone under freezing and triaxial stress conditions, a series of triaxial creep tests on frozen red sandstone specimens containing a single, pre-existing flaw at −10°C and under a confining pressure of 4 MPa were carried out with a self-developed DRTS-500 subzero rock triaxial testing system. The multistage loading creep curves were obtained, and the evolution laws of deformation and damage for the frozen specimens in the primary (instantaneous), secondary (steady-state) and tertiary (accelerating) phases were analyzed. The nonlinear visco-elastoplastic constitutive model of red sandstone with a single ice-filled flaw was established according to the fractional calculus theory and the Kachanov damage theory. The results show that the initial creep property, unstable creep property and creep failure mode of frozen single-flaw red sandstone are significantly affected by the flaw dip angle. The proposed creep damage model can accurately describe the complete creep curves of frozen red sandstone with a single ice-filled flaw, especially in the unstable creep stage. The influences of the stress level and flaw dip angle on the creep parameters were analyzed, and sensitivity analyses of the characteristic creep parameters were carried out to verify the reliability and rationality of our creep model. This research can be applied to the assessment of collapse, cracking and other long-term failures and hence can be used as a theoretical basis of design in the freezing engineering of coal mine shafts.