Issue34

Y. Li et alii, Frattura ed Integrità Strutturale, 34 (2015) 599-607; DOI: 10.3221/IGF-ESIS.34.66 606 The relationship between shear strength and fractal dimension (1) The relationship between fractal dimension and the cohesive force is shown in Tab. 5 and Fig. 5. With fractal dimension increasing, the cohesive force would decrease. When the fractal dimensions of samples 1, 2 and 3 are over 0.5, 0.85 and 0.963 respectively, the cohesion drops rapidly, and changes of cohesion in different fractal dimensions are familiar to crack ratio. But even though the mutation of the fracture in sample 3 is apparent, it cannot be observed when the fractal dimension is less than 0.963, so it is considered to have no impact on crack ratio in this situation. (2) The relationship between the fractal dimension and the internal friction angle is shown in Tab. 5 and Fig. 6. Changes in the internal friction angle in different fractal dimensions are familiar to cohesive force, and they both have a threshold quantity. After the first wet-dry cycle, the crack of samples 1 and 3 do not appear, the fractal dimension is 0, the internal friction angle is 8.82°and 9.06°respectively. After the second wet-dry cycle, because of the different method of humidification, the fractal dimension and internal friction angle of samples 1 and 3 have different trends. Due to the relatively large size, sample 2 would form the earlier fracture, with the fractal dimension having a great effect on the internal friction angle. Figure 5: The relationship between fractal dimension and cohesive force. Figure 6: The relationship between fractal dimension and internal friction angle. C ONCLUSION y changing the sample size and humidification method to study the effects of cracks on shear strength of red clay, this study analyzed the mechanics of red clay cracking, and the main conclusions are as follows: 1. To analyze variables such as the matrix suction in the process of fracture development in red clay, we established the mechanics model, determined the state equation of the soil cracking critical conditions, so that study of the images of soil fissures would become an analysis of the specific formula. 2. With the increase of the number of dry-wet cycles, shear strength of samples 1 and 2 would decrease. After the first dry-wet cycle, the intensity index was at its maximum. With the increase of the number of dry-wet cycles, the cohesive force of sample 3 continued to decline. 3. There is a strong correlation between the shear strength of red clay and the crack ratio. With an increase in the crack ratio, the strength curve of samples 1 and 3 are both similar to a parabola, and the change rule of the curve of sample 2 is slightly different. 4. With an increase in the fractal dimension, the intensity index will decrease, as the influence of the crack ratio on the strength index shows that the fractal dimension can be used as one of the indicators in discrimination of the crack influence on the strength of red clay. R EFERENCES [1] Yingwen, Z., Lingwei, K., Aiguo, G., et al., Mechanical behaviors and water-sensitive properties of intact Guangxi laterite, Rock and Soil Mechanics, 04 (2003) 568-572. B