Development of Laminar Shear Beam (LSB) Containers in Physical Modeling of Geotechnical Earthquake Problems: A Review

Physical modelling experiments at 1 g via shaking table or augmented gravitational field (Ng) with geotechnical centrifuge are powerful tools that have been widely used to investigate the seismic behaviour of various earthquake-related problems in recent decades. It is an established method for verifying design hypothesis, realization failure mechanisms, and gaining an insight into complex geotechnical problems including liquefaction-induced phenomena and their mitigation techniques, level or inclined grounds, problematic soils, retaining walls and embankments, and soil-structure systems such as shallow or pile foundation system through the use of appropriate similitude laws. While element tests are frequently used to obtain dynamic soil parameters, they fail in providing realistic observations of how soil and structures interact in reality. Thus, physical modelling is a better approach to understanding the behaviour of a wide range of geotechnical problems where large deformations occur such as liquefaction, lateral spreading, or landslide. However, geotechnical models cannot be directly mounted on shaking tables due to the requirements of confinement. To properly model the ground in full or reduced-scale physical modelling tests, a model container is required to hold the soil in place and provide confining stresses. Replication of the semi-infinite extent of the ground in a finite dimension model soil container could raise challenging issues; the undesirable effects of the container’s artificial boundaries could affect the obtained results by altering the stress-strain field of the soils through reflected P-waves along other superfluous waves within the model.
In the current study, a comprehensive literature review on the advancement of physical modelling in geotechnics has been carried out. In this regard, a brief historical development of shaking tables and geotechnical centrifuge apparatus was outlined. Further, different types of developed model containers were explored. Additionally, vital criteria and requirements of an ideal container for carrying out seismic model tests at 1 g shaking table or Ng centrifuge experiments were thoroughly discussed. In particular, the development of laminar shear beam (LSB) containers as well as key properties in terms of detail design, construction, and particular usage in designated projects was presented in this paper. In the end, the recently fabricated LSBs were examined nationwide providing key properties and features in their design procedures.
Among all types of developed model containers, LSBs are the most common containers due to their accuracy in reproducing one-dimensional (1D) ground response in seismic conditions. The LSB allows free movement of soil column during shaking without imposing significant boundary effects and is able to maintain 1D soil column behaviour. Moreover, the use of LSBs enables the modelling of large strain modelling problems. Comparative studies by numerous researchers have confirmed that LSBs are the most advanced and efficient type of soil container in modelling soil-structure systems.