In order to realise efficient, economic, low carbon and environmentally friendly slurry disposal, floc sedimentation velocity (S _f ), supernatant volume (V _s ), water content of bottom mud (W _b ), supernatant turbidity (N _s ) and pH value were determined by slurry sedimentation tests, specific resistance tests, and water quality analysis. Orthogonal tests were performed to analyze the matching rule and control mechanism between flocculants and the slurry settlement characteristics. The results show that polyaluminum chloride (PAC) and polyferric chloride (PFC) had a low dose and a fast sedimentation rate. The sedimentation effect of 20 ionic degree cationic polyacrylamide (CPAM-20) in organic flocculant is the best. Although flocculants can shorten the sedimentation time, excessive flocculants can also weaken the slurry separation effect. The sedimentation efficiency of organic flocculants is higher than that of inorganic flocculants, but it is easy to form foam on the supernatant surface. For the composite flocculants, the sensitivity sequence of S _f , V _s and W _b is PAC>CPAM-20>PFC. PAC plays a controlling role in the sedimentation effect of the slurry.

Grouting is a common method used to fill rock joints to improve the stability and integrity of rock mass in geotechnical engineering, and the filling has been observed to have an effect on crack behavior and mechanical property. To investigate this topic, a numerical study of crack behavior and mechanical property of rock samples with two parallel open flaws or infilled flaws under uniaxial compression was conducted in this research. The smooth joint model was proved to be suitable to simulate the interface between rock material and grout material. The occurrence of shear cracks at the interface between rock material and grout material as well as the occurrence of tensile cracks in the grouting material has been successfully simulated in this research. Numerical results indicate that grouting can reduce the tensile force near the flaws, suppress the generation of tensile cracks, and improve the initiation stress of the sample. The tensile force in the specimens with infilled flaws is smaller than that with open flaws, which lead to the improvement of the peak strength of the sample. Moreover, crack development and mechanical properties of samples are affected by bridge inclination angle and flaw inclination angle.