Shear strength behaviour and critical shear stress for nesosilicates subjected to wildfire

• Main Author: Wan Nurhusna, Wan Azmi
• Format: Undergraduates Project Papers
• Language: English
• Published: 2017
• Subjects: TA Engineering (General). Civil engineering (General)
• Online Access: http://umpir.ump.edu.my/id/eprint/23694/1/Shear%20strength%20behaviour%20and%20critical%20shear%20stress%20for%20nesosilicates%20subjected%20to%20wildfire.pdf; http://umpir.ump.edu.my/id/eprint/23694/
• Institution: Universiti Malaysia Pahang Al-Sultan Abdullah

Fires can reduce soil infiltration capacity, induce soil water repellency and increase runoff and erosion. This study examines the effect of temperature under natural and laboratory condition of soil samples collected from hillside at Jalan Gambang. The unburned and burned soil sample were obtained from site. In addition, the soil samples under laboratory condition were burned at three temperatures, i.e. 440˚C, 800˚C and 1350°C. Various soil properties were studied, including specific gravity, Atterberg limits, swell index and organic matter content. The soil-water characteristic curve (SWCC) of all soil samples were also determined. The SWCC were established using chilled-mirror dew point technique and osmotic technique. The shear strength of soil were determined using vane shear test and direct shear test. Experimental results demonstrated that temperature at 440°C, the liquid limit, organic matter content and SWCC were reduced and the swell index was eliminated. Heating the soil at 800°C and 1350°C completely eliminated the liquid limit, plastic limit, swell potential and organic content of soil tested. The soil suction decrease with increasing temperature. From overall experimental results, the natural burned soil was predicted had experienced a fire at temperature between at 440°C. Results of vane shear test for natural unburned, natural burned and burned temperature at 440˚C shows the result which are shear strength decreases with increasing water content. The result of direct shear test shows cohesion diminished with increasing water content. Burned 440 shows the results of cohesion increase compare to burned 800˚C and 1350˚C. However, the result influence water content due to angle of friction indicate instability might be attributed to high percentage of sand fraction in the specimen, which causes lower values of cohesion, hence lower values of shear strength.