Mesco-analysis On Mud Flow In Crack Rock Mass And Experimental Study On Mud-water Burst In Confined Karst Area

The research material of experiments is red clay which is widespread in the south of China,analyses theoretically flow characteristics of mud in fractured rock mass,regarding mud viscosity tests and laboratory model experiments of mud-water burst as majority study methods,in addition to combine with numerical analysis,this thesis discusses the change regulation of mud viscosity under the influence of grain size and moisture content ? how is the mud flows through the mud channel under mud-water pressure?the characteristic of slurry discharge after mud burst?the laws of needing time about mud outburst under different water pressure.It is of great significant for understanding regulations and mechanisms of mud burst in Karst region and prevention and treatment of mud outburst.conclusions are following:(1)Flow characteristics of mud in fractured rock mass are influenced by viscosity of mud?roughness of fracture?stress conditions of fractured rock mass?seepage pressure and so on.(2)Using numerical software of PFC conducted a series of numerical analysis show: firstly,there are few particles immediately pushed into cracks,the majority of particles move toward the center of models,a phenomenon of eddy current is appeared on the corner of the models;with the increase of running time,flow direction of particle will be changed certainly,eddy current is disappear,the direction of flow on the corner is pointed to crack,and the rest of particles along to vertical direction;research also found the relation between particle velocity and pressure gradient is no proportional function entirely but a function of "S" curve,which means the relation between particle velocity and pressure gradient does comply to Darcy laws.(3)NDJ-8S rotary viscometer was utilized to conduct tests of mud viscosity show that: the mud viscosity is not depend on the particle size but on moisture content;the changeable stages of mud viscosity can be divide into three phases: firstly,drops rapidly? then,declined slowly ?ultimately,keeping stable,at the third phase mud viscosity is approximately equal to purely water 5.46mpa·s;Experiments found that the relationship between slurry viscosity and moisture are exponential function.(4)According to the laboratory experiments of mud-water burst which were conducted on Test instrument of mud outburst in confined Krast ares found: the procedure of slurry burst can be distinguished into four stages,mud-water burst lag to time.The thesis investigated the non-linear relationship between pressure gradient of mud-water and flow speed on the basis of experiments data.