Improvement of Alluvial Soil Quality from Flood in Chiang Rai Province Using Portland Cement for Producing Soil-Cement Blocks for Landslide Protection Walls (TOR Block)

Abstract

The major flood that struck Chiang Rai Province in 2024 caused significant disruptions to lives and the economy, including the widespread deposition of alluvial soils in residential and economic areas. These accumulations posed challenges for post-disaster waste material management. This study aims to improve the quality of alluvial soils using Portland cement to produce soil-cement blocks for constructing landslide protection walls, known as TOR Blocks. Soil samples collected from flood-affected areas were tested for their basic engineering properties and toxicity. Subsequently, a mix design was developed by varying the cement content from 5% to 30% to determine the optimal proportion for block formation. As the production facility is located in a remote area and aims to promote community self-reliance, a practical field quality control method using a free-falling object technique was also investigated. The findings indicate that alluvial soils from Mae Sai District are most suitable for producing TOR Blocks due to their sufficient availability, ease of access, and lower cement demand compared to soils from other areas. An optimal cement content of 15% by dry soil weight achieved a compressive strength exceeding 10 kg/cm² at 7 days. The results from the free-falling object experiments were consistent with values calculated based on mechanical principles. Specifically, with 15% cement content, the appropriate drop height was 50–60 cm, while with 20% cement, the suitable height was 150–180 cm. This method offers an effective and practical approach for quality control in remote locations.