Laboratory-Based Full-Scale Calibration Chamber for Grout Injection Studies

Permeation grouting is a widely used soil improvement technique in civil and geotechnical engineering, aiming at enhancing soil strength, stiffness, and cohesion by injecting consolidating mixtures into pore spaces or discontinuities. Its applications include foundation stabilization, tunnelling ground improvement, and mitigation of landslide or subsidence risks. Effective implementation requires a detailed understanding of both grout injection mechanics and the resulting modifications to soil properties. Traditionally, grouting performance is assessed through in situ tests. While these provide practical insights, they are costly, offer limited control over boundary conditions, and provide restricted information on the spatial propagation of grout. To overcome these limitations, this research introduces a laboratory-based calibration chamber (CC) methodology, to replicate grouting operations under controlled yet representative conditions. The CC framework here presented enables reduced experimental costs, precise control of key parameters, and systematic investigation of variables such as grout composition, injection pressure, and soil structure. The paper describes the design of the CC and reports preliminary injection trials. Grout propagation was continuously monitored using embedded sensors, allowing real-time tracking of the injection process. Following treatment, soil specimens underwent hydromechanical testing to assess the spatial extent and efficiency of grouting. Results reveal the formation of cemented bulbs within the soil, showing improved mechanical performance that diminishes with radial distance from the injection point. This laboratory approach demonstrates the potential for detailed, cost-effective investigation of permeation grouting processes, offering insights that can inform field-scale applications and optimize soil improvement strategies.