Disturbance function for soil disturbed state strength based on X-ray computed tomography triaxial test.

Soil is a porous, multiphase, and loose medium, which is prone to serious disturbance by the activity of biological livings, accompanied with cracks and macro pores. These phenomena greatly affect the strength of soil and the degradation of land. Two different quantifiable values from X-ray computed tomography (CT) images are usually used to define the disturbance function for soil disturbed state strength: mean density (MD value) and standard deviation (SD value). Two types of disturbance functions are investigated quantitatively by CT-triaxial testing using four samples with different macro-pore sizes (disturbed samples) and one sample without a macro-pore (undisturbed sample). It is found that the shear strength of three disturbed samples with the same macro-pore size is close to each other. As with the shear strength, the SD value and its defined disturbance function have a similar correlation with the cross-sectional area of macro-pore. However, the MD value and its defined disturbance function have no regularity with the macro-pore size. Therefore, the disturbance function expressed in terms of the SD value is deemed more reasonable and appropriate in analyzing the soil disturbed state strength using the quantitative CT morphometry. While, the disturbance function defined by the MD value has often been used to characterize a rock damage.

Floc Performance parameters during water treatment in a micro-vortex flocculation process determined by machine vision.

The coagulant dosage of an existing water plant is mainly determined based on the experience of water treatment process and influent/effluent water quality indexes that have time hysteresis effects. To solve this problem, the effect of coagulant dosage on a number of parameters used to evaluate the efficiency of flocculation in a setup was determined by using the micro-vortex flocculation technology in conjunction with the investigation of the relation between the equivalent diameter and the fractal dimension. By means of the machine vision system and computerized analysis, the effects of floc quantity, floc equivalent diameter and fractal dimension can be assessed. The correlations of these parameters with turbidity and ζ potential of the settling water, taken as measures for effluent quality, were explored. The study results show that the optimal flocculation effect with a turbidity removal rate of 97.9% is achieved at the poly-aluminum chloride dosage of 20 mg/L. Meanwhile, a power exponential relation between the floc equivalent diameter and the fractal dimension was established with a correlation coefficient R2 of 0.826; relations among the effluent turbidity and the floc quantity, equivalent diameter, fractal dimension were established with a correlation coefficient R2 of 0.982, 0.851, and 0.875, respectively; equations between the ζ potential and the floc quantity, equivalent diameter, fractal dimension were also established where the correlation coefficient R2 were 0.868, 0.879, and 0.942, respectively. These results may provide excellent reference data for water plants to feed back the coagulant by floc performance parameters, which could relieve the hysteresis effect efficiently.