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

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

Studia Geotechnica et Mechanica

Volume 40 (2018): Issue 2 (October 2018)

By: Francesco Cafaro, Emanuele Miticocchio and Valentina Marzulli

Open Access

|Sep 2018

Figures & Tables

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

Three-dimensional view of the generated mesh.

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

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_

		Prototype	Scaled Model	N^*Scaled Model
\|u\|	[mm]	3.375	0.541	3.246
σ_xx	[kN/m²]	2.488	2.305	2.305

Normalized Deviation (with respect to average) of σxx_

Type of Effect	Normalized Deviation
Scale Effect	3.8%
Constitutive Model Effect	15.9%
ϕ’ Variability Effect	32.4%
ψ Variability Effect	11.7%
3D Effect (σ_xx vs σ_yy)	15.4%

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

		H-S	M-C	Ratio
u_x	[mm]	1.799	0.736	2.4
u_z	[mm]	7.464	3.294	2.3
\|u\|	[mm]	7.678	3.375	2.3
σ_xx	[kN/m²]	3.426	2.488	1.4

Maximum values obtained for each combination_

		1	2	3	4	5	6
u_x	[mm]	0.795	0.843	0.864	0.736	0.795	0.764
u_z	[mm]	3.016	3.033	3.046	3.294	3.016	3.038
\|u\|	[mm]	3.119	3.130	3.166	3.375	3.119	3.133
σ_xx	[kN/m²]	1.552	1.840	1.879	2.488	1.552	1.598

Mohr-Coulomb Model Parameters_

Parameter	Unit of Measurement	Backfill	Foundation
ρ	[kg/m³]	1700	1800
E’	[kN/m²]	10900	20400
v’	[]	0.25	0.25
φ’	[°]	41.8	45.5
δ	[°]	20.9	22.75
R_inter	[]	0.427	0.412
ψ	[°]	15.6	14.3

Scaling strategies for simulating the behavior of a lunar structure_

SCALING PATH	INVESTIGATION OUTPUT	ADVANTAGES	PROBLEMS
Microgravity To Terrestrial Gravity	Prototype Behavior	Low Cost; No Coriolis Effect	Fixed Size Reduction; Scale Error deduced by “Virtual Prototype”
Microgravity To Hypergravity	Prototype Behavior	Further Size Reduction; Scale Error measured on Experimental Basis	High Cost; Coriolis Effect; Undesired Shear Stresses

Hardening Soil Model Parameters_

Parameter	Unit of Measurement	Backfill	Foundation
ρ	[kg/m³]	1700	1800
E₅₀^ref	[kN/m²]	10900	20400
E_oed^ref	[kN/m²]	10900	20400
E_ur^ref	[kN/m²]	32700	61200
p^ref	[kN/m²]	15	30
m	[]	0.5	0.5
v_ur	[]	0.20	0.20
φ’	[°]	41.8	45.5
δ	[°]	20.9	22.75
R_inter	[]	0.427	0.412
ψ	[°]	15.6	14.3

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

		x-direction	y-direction
\|u\|	[mm]	3.375	2.901
σ_xx(yy)	[kN/m²]	2.488	1.825

Geotechnical parameters used in the analyses (Case b)

Combination	φ’	ψ	E’	ν’	δ	R_inter
	[°]	[°]	[kN/m²]	[]	[°]	[]
1	45.50	15.60	20400	0.25	22.75	0.412
2	45.50	20.90	14200	0.25	22.75	0.412
3	45.50	22.60	11200	0.25	22.75	0.412
4	41.80	15.60	10900	0.25	20.90	0.427
5	45.50	15.60	20400	0.25	22.75	0.412
6	49.70	15.60	24400	0.25	24.85	0.393

DOI: https://doi.org/10.2478/sgem-2018-0012 | Journal eISSN: 2083-831X | Journal ISSN: 0137-6365

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Language: English

Page range: 133 - 139

Submitted on: Jan 2, 2018

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Accepted on: May 29, 2018

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Published on: Sep 11, 2018

Published by: Wroclaw University of Science and Technology

In partnership with: Paradigm Publishing Services

Publication frequency: 4 issues per year

Keywords:

lunar geotechnical structures,

physical scale-modelling,

lunar regolith,

numerical simulations,

Related subjects:

Geosciences, other,

Materials sciences,

Porous materials,

Mechanics and fluid dynamics

© 2018 Francesco Cafaro, Emanuele Miticocchio, Valentina Marzulli, published by Wroclaw University of Science and Technology
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

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