Lunar exploration, which slowed in the 21st century after the Apollo program, has seen more activity recently with the participation of Asian countries such as Japan, China, and India. Because lunar modules and rovers cannot be tested directly on lunar soil, these countries have developed lunar simulants. Simulating lunar soil is difficult and expensive because its formation mechanism and geotechnical behavior are comprehensively different from those of the terrestrial soil. Johnson Space Center Number One (JSC-1) and Johnson Space Center Number One A (JSC-1A), developed by the National Aeronautics and Space Administration, are the most widely used simulants. Korea has yet to succeed in developing a lunar simulant that meets international standards. The authors perform basic research on lunar simulant development based on basalt samples having similar chemical and mechanical properties to those of lunar soil, with reference to lunar soil data reported under the Apollo program. The resulting prototype is named Korea Lunar Stimulant—Type 1 (KLS-1). Compared with other lunar simulants [JSC-1 and Fuji Japanese Simulant 1 (FJS-1)], KLS-1 shows promise in terms of affordability and similarity to real lunar soil. As such, it is expected to find a wide variety of applications not only in space development projects but also in international research.

Underpinning in an existing foundation with piles is commonly used to improve their load-bearing capacity to allow vertical extension works. This study evaluated the effect of the piles’ stiffness on the load-sharing behavior of existing and underpinning piles during the vertical extension of existing buildings. A series of 1 g model tests, all with a scale factor of 1/20, was used to compare the underpinning performance of micropiles of varying stiffness. The performance was evaluated in terms of total settlement reduction and load sharing capacity. The results showed that the underpinning performance improved with the increase of underpinning pile stiffness. The ratio of carried loads of the underpinning pile to the existing pile increased linearly with its increasing stiffness (as expressed as a ratio relative to the stiffness of the existing pile).

Foundation reinforcement using micropiles can enhance the bearing capacity of foundations and reducing the settlement of structures in building remodeling with vertical extension. However, in the process of vertical extension following foundation reinforcement, the allowable bearing capacity of the existing piles is still likely to be exceeded due to the additional load. This study presents a preloading method used to carry a partial load from the existing piles and to mobilize skin friction along the reinforcing piles in advance to ensure that the carried load on the existing piles does not exceed the pile’s allowable bearing capacity. Two cases, foundation underpinning without preloading and with preloading, were compared using FEM analysis with PLAXIS 3D. The analysis results showed that the preloading method using jacking equipment had a significant influence on mobilizing the skin friction along the reinforcing pile and reducing the carried load on the head of the existing piles.