Issue34

Y. Li et alii, Frattura ed Integrità Strutturale, 34 (2015) 599-607; DOI: 10.3221/IGF-ESIS.34.66 600 strength of the cement silt clay and the cement silt were researched by cyclic triaxial tests [9]. High liquid limit undisturbed clay quick shear tests with different moisture were carried out through different dry-wet cycle paths, including the process of humidification and dehumidification of the dry-wet cycle[10]. The relationship between particle mesoscopic and macroscopic mechanical parameters of cohesive materials were studied [11]. But there is little research on shear strength of red clay based on dry-wet cycle. Experiments have been conducted on the strength characteristics of unsaturated red clay and expansive soil, which are different from those of common clay soil [12]. The relationships among mechanical indexes, swelling-shrinkage properties, pore size distributions and moisture content of lateritic clay in Guigang of Guangxi Zhuang Autonomous Region were discussed [13]. The red clay soil and the expansive soil were analyzed regarding the relationships between shear strength index and temperature [14]. It has been determined that high and low confining pressures have different effects on the deformational properties and mechanical index of frozen soil [15]. In addition, the above results show the various impact factors of study on intensity variability of the clay. However, the cracks’ effect on the shear strength of red clay has been limited. In order to observe development of red clay fractures, we simulated red clay in dry-wet cycles under natural conditions combined with computer image processing technology. It was concluded that reticular cracks will form in the red clay under certain circumstances, then a direct shear apparatus was used to test this sample. The test considered multiple factors in controling the cutting ring size and humidification method to determine the fractal dimension and crack ratio of three samples under different conditions. After each dry-wet cycle, direct shear tests were conducted on samples to study the effects of red clay cracks on cohesive force and internal friction angle. T ESTING METHODS Samples he red clay samples were taken from the Guilin Yan Mountain. The red clay samples were dried then crushed, and a fine sieve 2.0mm was used to sieve samples. Finally, these samples were stored. The physical and mechanical parameters of the red clay are shown in the Tab. 1. w/% ρ(g/cm 3 ) e I P /% I L c/kPa φ /° a v1-2 /MPa -1 51.20 1.81 1.42 26.10 0.76 19.00 13.20 0.60 Table 1 : Physical and mechanical indexes of red clay. Factors Value Class Number Artificial humidification Times of dry-wet cycle: 1, 2, 3, 4, 5; Moisture content: 35%; Dry density: 1.5 g/cm 3 ; Small cutting ring: diameter is 61.8mm, height is 20mm; Large cutting ring: diameter is 150mm, height is 50mm. Small cutting ring: 12 group Large cutting ring: 12 group Vacuum saturation Times of dry-wet cycle: 1, 2, 3, 4, 5; Moisture content: 35%; Dry density: 1.5 g/cm 3 ; Small cutting ring: diameter is 61.8mm, height is 20mm. Small cutting ring: 12 group Table 2 : Test project. Test project This test mainly considered the sample size and the influence of different humidification methods on the mechanical properties of red clay. Study on the attenuation law of shear strength of samples after five dry-wet cycles shows that shear T