How do we begin to expand our civilization to the Moon? What are the technical issues that infrastructural engineers, in particular, must address? This paper has the goal of introducing this fascinating area of structural mechanics, design, and construction. Published work of the past several decades about lunar bases is summarized. Additional emphasis is placed on issues related to regolith mechanics and robotic construction. Although many hundreds of papers have been written on these subjects, and only a few tens of these have been referred to here, it is believed that a representative view has been created. This summary includes environmental issues, a classification of structural types being considered for the Moon, and some possible usage of in situ resources for lunar construction. An appendix provides, in tabular form, an overview of structural types and their lunar applications and technology drivers.

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Knowledge of the lunar regolith is essential to success in lunar missions whether crewed or robotic. The regolith is the loose material overlying more intact strata on the Moon. It varies in thickness from several meters on the maria or lunar seas to many meters on the highlands of the Moon. The regolith is the material humans walked and drove on from 1969 to 1972. In the future, people will use it for radiation protection and as a resource for recovery of oxygen, silicon, iron, aluminum, and titanium. Implanted in the regolith by the solar wind are recoverable amounts of volatiles such as hydrogen and helium. Increasing our knowledge of the mechanical properties of the regolith will enable constructors of the 21st Century to build habitats, do mining, establish manufacturing, and erect telescopes on the Moon. We already know much of the regolith from robotic and astronaut missions to the Moon. There is much more to be learned.

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At the present time, numerous computer programs are available for backcalculating layer elastic moduli using deflection basins obtained by nondestructive testing. These programs usually utilize both a forward calculation and a backcalculation scheme. This paper presents the results of a study made of several of these computer codes with deflection basins obtained from several low-volume (surface-treated) road sections using a falling weight deflectometer (FWD). A nonlinear finite-element program (ILLIPAVE) was first used to backcalculate the layer moduli of the surface-treated pavement sections using FWD deflection basins by the trial-and-error approach. A pavement dynamic cone penetrometer (PDCP) was also used (in situ) to measure the layer moduli. Several backcalculation programs, namely, BISDEF, CHEVDEF, ELSDEF, ISSEM4, MODCOMP2, LOADRATE, and MODULUS then were used to backcalculate the layer moduli. The forward calculation schemes considered include: BISAR, CHEVRON, ELSYM5, NELAPAV, and ELMOD was well as ILLIPAVE. All of these programs, including ILLIPAVE, are microcomputer based. The paper also includes an example problem which involves backcalculating the layer moduli of a 30.48-m (100-ft) stretch of a typical farm-to-market road in which deflection basins were taken at one-foot spacings.

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