Experimental study of the single-particle crushing-strength-size effect of calcareous sand-quartz sand

Abstract

<p indent="0mm">Geotechnical engineering constructions of islands and reefs in the South China Sea are important for the implementation of the South China Sea strategy in the future. Calcareous sand is the main material of foundations and buildings for engineering construction of the island and reef of South China. Calcareous sand has the characteristics of porosity and fragility because of the special material source and formation process. A series of single-particle crushing tests for calcareous sand of different particle sizes taken from the island and reef of South China was performed to determine the crushing strength characteristics and size effect. The experimental results were compared with the single-particle crushing test results of quartz sand under identical conditions. According to the force-displacement curves plotted based on the single-particle crushing test results, the crushing modes of single particles of calcareous and quartz sand were analyzed. The particle-crushing strengths of calcareous and quartz sand were analyzed statistically based on the Weibull distribution function. The relationship between the single-particle crushing strength and particle size was explained based on the size effect. The results show that the single-particle crushing mode of calcareous and quartz sand can be divided into three modes, namely, the single peak point mode, double peak point mode, and multipeak point mode. The peak force of a single particle of calcareous sand and quartz sand decreases with a decrease in particle size. However, its crushing strength decreases with an increase in particle size and shows an obvious size effect. The crushing energy increases with an increase in particle size. The crushing strength and crushing energy of single-particle of quartz sand are greater than those of single-particle of calcareous sand when the particle sizes of calcareous and quartz sand are identical. The Weibull distribution can be applied to calculate the crushing strength of the calcareous and quartz sand well. The values of the Weibull modulus are 2.2 and 2.97 for calcareous and quartz sand, respectively. The crushing strength for larger particle sizes can be obtained using the Weibull modulus. The research results provide a theoretical basis for revealing the particle-crushing characteristics of calcareous sand and the stability of the engineering construction at a calcareous sand site.