Study on Similar Materials for Tunnel Lining and Sand in Water-Rich Scale Model Tests

Abstract

Addressing the challenge of similar material selection in fluid-solid coupling physical model tests for water-rich tunnels, this study systematically investigates the mix proportion optimization of similar materials for tunnel lining and sand. Through sequential testing, two lining similar material schemes based on gypsum and micro-concrete were compared. The results indicate that gypsum-based materials, although capable of matching scaled mechanical parameters, exhibit poor forming integrity and significant water softening, making them unsuitable for water-involved environments. The optimized micro-concrete proportion demonstrates good compactness and impermeability, with a strength retention rate of approximately 70% after water immersion, rendering it more adaptable to water-rich conditions. For sand similar materials, a practical scaled-down strategy of "parameter substitution" was proposed to maintain soil characteristics while strictly controlling particle gradation to ensure key parameters such as friction angle and permeability coefficient. Ultimately, a mixing scheme of river sand, barite powder, and glass fiber was selected, successfully simulating the density, internal friction angle, and permeability coefficient of the prototype medium-coarse sand layer. This research establishes a design method for similar materials in water-rich fluid-solid coupling model tests, with permeability coefficient and hydro-stability as primary control indices, providing reliable technical references for physical simulation of similar projects.