Innovative experimental method based on development of transparent rock mass materials for physical tests

In geotechnical model experiments, the classical test model is made of opaque materials and its direct deformation measurement is limited to the outside surface of model, while the internal deformation of model can be investigated only by some local or indirect methods. So the deformation, cracking process and complex mechanical characteristics of rock mass are difficult to be explicitly made because of the limited deformation data obtained from the opaque model. This paper has drawn lessons from the transparent soil method for the development of transparent rock mass materials, test load system and DSCM technique and has solved the most important problem such as model transparency, strength similarity with soft rock mass and digital photogrammetry for transparent rock mass. The main achievements from the researches on the basic physical and mechanical tests and similar model experiments using the developed transparent rock mass are summarized as follows: (1) The preparation methods of transparent rock mass are proposed as well as the optimized mixture ratio of silica powders, liquefied paraffin wax and tridecane for better transparency. A novel transparent similar material is developed successfully for simulating the mechanical property, deformation and fracture characteristics of soft rock. (2) Two types of effective DSCM application methods, placing measured ball points and making a digital spectacle plane inside the test model which is illuminated by red laser light and incandescent light respectively, for measuring internal deformation of transparent rock mass model are proposed and implemented. (3) An innovative physical similar experiment method based on the transparent rock mass materials is established, which includes components selection, mixture ratio of sample or model preparation, process control, man-made measured points or cross plane with colored spectacles, digital photogrammetry and test loading apparatus. The innovative experiment method is beneficial to the experimental studies on of scientific problems and engineering technology in geotechnical engineering fields.