Feasibility Study on Synthetic Soft-Rock Materials for Hydraulic Model Tests
Certain riverbeds in western Taiwan consist of soft-rock geology, which is highly susceptible to severe erosion during heavy typhoon rainfall. This leads to riverbed changes and raises safety concerns for hydraulic structures. However, existing hydraulic models predominantly use conventional sand and gravel materials, making it difficult to accurately replicate the scour behavior of soft-rock riverbeds and limiting the practical application of test results.
As a preliminary research project, this study aims to develop simulated soft-rock materials suitable for hydraulic model tests, establishing material selection and construction techniques for soft-rock bed scour experiments.
Technical Features
Selecting materials based on availability, low cost, reproducibility, and non-toxicity, this study explored material formulations suitable for constructing soft-rock topography in hydraulic models.
Following comparative material property analyses, polymer silicone oil was selected as the binding material due to its lack of need for underwater curing, high stability, and excellent hydrophobicity. Two main material combinations were evaluated:
- Mudstone + Gypsum / Shotcrete Additive
- Glass Sand + Silicone Oil
Through clear-water scour, suspended-load scour, and bed-load scour tests, the study analyzed the scour characteristics, material stability, and fabrication feasibility of different synthetic soft-rock mixtures to evaluate their applicability in hydraulic model testing.
Test results revealed that under clear-water scour conditions, a ratio of 98% mudstone to 2% gypsum yielded an average scour depth of approximately 12.5 mm, coming closest to the target scour range of 8 -12 mm. On the other hand, the Glass Sand + Silicone Oil combination exhibited superior performance in material homogeneity, fabrication convenience, and scour control capability, effectively controlling scour depth under clear-water, suspended-load, and bed-load actions.
Applications & Results
Considering factors such as material availability, homogeneity and isotropy rapid reproduction capacity, scour control precision, and production cost, the Glass Sand + Silicone Oil combination received the highest rating (4.5/5) and was selected as the optimal synthetic material for building soft-rock topography in hydraulic models.
This study established foundational application techniques for artificial soft-rock materials in hydraulic model testing, enhancing the capacity to simulate soft-rock bed erosion behavior. In the future, this technology can be applied to river scour mechanism studies, river management project evaluations, and flood control structure design analyses.
By overcoming the limitations of traditional hydraulic models in simulating soft-rock riverbeds, this technology improves the reliability of hydraulic test outcomes, providing crucial technical support for future river management and water resources engineering planning.