ABSTRACT
High-temperature ground improvement is becoming more widely used for various geotechnical applications. However, examples of the application of ground heating to tunnelling are limited. This study aims to assess the applicability of high-temperature ground improvement to tunnelling by reporting the variation in Unconfined Compressive Strength (UCS) and other geotechnical properties of clay and sand after heating to high temperatures. Laboratory experiments were conducted to assess the engineering properties of clay and sand specimens heated in a furnace at temperatures ranging from room temperature (~25°C) to 1200°C. The results show that a high temperature of 1200°C considerably affects the UCS and point load strength index of the clay and sand specimens, mainly mixed clay and sand specimens with ratios of 3:1 and 1:1 sand to clay. A higher clay content results in increased depth and frequency of surface fracturing within the specimens resulting in reduced material strength. The highest value of UCS obtained from the experiments is 1.9 MPa by heating a 25% clay 75% sand specimen to 1200°C until it becomes vitrified. Generally, high temperatures (~1200°C) result in an increase in the UCS strength index of soft clayey, sandy soils.
