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Remarks On The Sources Of Error In The Modelling Of Lunar Geotechnical Structures

Francesco Cafaro
Francesco Cafaro
, 
Emanuele Miticocchio
Emanuele Miticocchio
 and 
Valentina Marzulli
Valentina Marzulli
   | Sep 11, 2018
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Article Category: Research Article
Published Online: Sep 11, 2018
Page range: 133 - 139
Received: Jan 02, 2018
Accepted: May 29, 2018
DOI: https://doi.org/10.2478/sgem-2018-0012
Keywords
© 2018 Cafaro Francesco et al., published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Figure 1

Geometrical model: plan view (left side) and cross section (right side).
Geometrical model: plan view (left side) and cross section (right side).

Figure 2

Three-dimensional view of the generated mesh.
Three-dimensional view of the generated mesh.

Figure 3

Total horizontal stress σxx: (a) Prototype; (b) Scaled model. (Plaxis notation for the sign).
Total horizontal stress σxx: (a) Prototype; (b) Scaled model. (Plaxis notation for the sign).

Figure 4

Effect on the predicted prototype behavior of two constitutive models (Mohr-Coulomb and Hardening Soil): results are shown in terms of displacements along x-direction (ux).
Effect on the predicted prototype behavior of two constitutive models (Mohr-Coulomb and Hardening Soil): results are shown in terms of displacements along x-direction (ux).

Comparison between maximum absolute values for prototype and scaled model.

PrototypeScaled ModelN*Scaled Model
|u|[mm]3.3750.5413.246
σxx[kN/m2]2.4882.3052.305

Normalized Deviation (with respect to average) of σxx.

Type of EffectNormalized Deviation
Scale Effect3.8%
Constitutive Model Effect15.9%
ϕ’ Variability Effect32.4%
ψ Variability Effect11.7%
3D Effect (σxx vs σyy)15.4%

Comparison between maximum values for M-C and H-S models (Case a).

H-SM-CRatio
ux[mm]1.7990.7362.4
uz[mm]7.4643.2942.3
|u|[mm]7.6783.3752.3
σxx[kN/m2]3.4262.4881.4

Maximum values obtained for each combination.

123456
ux[mm]0.7950.8430.8640.7360.7950.764
uz[mm]3.0163.0333.0463.2943.0163.038
|u|[mm]3.1193.1303.1663.3753.1193.133
σxx[kN/m2]1.5521.8401.8792.4881.5521.598

Mohr-Coulomb Model Parameters.

ParameterUnit of MeasurementBackfillFoundation
ρ[kg/m3]17001800
E’[kN/m2]1090020400
v’[]0.250.25
φ’[°]41.845.5
δ[°]20.922.75
Rinter[]0.4270.412
ψ[°]15.614.3

Scaling strategies for simulating the behavior of a lunar structure.

SCALING PATHINVESTIGATION OUTPUTADVANTAGESPROBLEMS
Microgravity To Terrestrial GravityPrototype BehaviorLow Cost; No Coriolis EffectFixed Size Reduction; Scale Error deduced by “Virtual Prototype”
Microgravity To HypergravityPrototype BehaviorFurther Size Reduction; Scale Error measured on Experimental BasisHigh Cost; Coriolis Effect; Undesired Shear Stresses

Hardening Soil Model Parameters.

ParameterUnit of MeasurementBackfillFoundation
ρ[kg/m3]17001800
E50ref[kN/m2]1090020400
Eoedref[kN/m2]1090020400
Eurref[kN/m2]3270061200
pref[kN/m2]1530
m[]0.50.5
vur[]0.200.20
φ’[°]41.845.5
δ[°]20.922.75
Rinter[]0.4270.412
ψ[°]15.614.3

Comparison between results obtained for x-direction and y-direction.

x-directiony-direction
|u|[mm]3.3752.901
σxx(yy)[kN/m2]2.4881.825

Geotechnical parameters used in the analyses (Case b)

Combinationφ’ψE’ν’δRinter
[°][°][kN/m2][][°][]
145.5015.60204000.2522.750.412
245.5020.90142000.2522.750.412
345.5022.60112000.2522.750.412
441.8015.60109000.2520.900.427
545.5015.60204000.2522.750.412
649.7015.60244000.2524.850.393
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Language:
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Geosciences, other, Materials Sciences, Composites, Porous Materials, Physics, Mechanics and Fluid Dynamics
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