Experimental And Theoretical Study On Seepage Characteristics Of Brittle-plastic Incompletely Filled Fractures

Since the construction of human engineering,accidents caused by fissure seepage were not uncommon,so many scholars have carried out research on the law of fissure seepage,and the scientific research results have provided some help to the project construction.However,the structure of natural fractures was complex and changeable,and the causes of accidents were also varied.The existing theoretical basis still cannot explain the causes of some accidents.Therefore,there is a large room for development in the study of fracture seepage.Extensive research has been done on non-filled cracks and fully-filled cracks,but there were few studies on seepage flow of incompletely filled cracks.There are a large number of incompletely filled cracks in natural cracks,and the properties of the fillers are also different.Based on this phenomenon,this paper has carried out a study on the seepage stress of brittle-plastic incompletely filled cracks,and hopes that the research results can provide a new perspective for the causes of engineering accidents.Based on the previous research results,this paper first analyzes the basic properties of the brittle-plastic filling medium,and theoretically analyzes the law of seepage stress in the brittle-plastic incomplete filling cracks.Then,using sandstone,rubber,clay,and cement mortar with different ratios(1:2,1:4,1:6,1:8)as brittle-plastic filling medium,the seepage stress experiment of incomplete filling cracks was carried out.The change law of brittle-plastic incomplete fracture deformation seepage was studied.Finally,the theoretical and experimental results were compared and analyzed.The main conclusions are as follows:(1)The theoretical analysis of seepage stress of brittle incompletely filled cracks was divided into three stages: elastic stage,softening stage and residual stage;the theoretical analysis of seepage stress of elastoplastic incompletely filled cracks was divided into two stages: elastic stage and plastic stage;The theoretical analysis of seepage stress of plastic incompletely filled cracks was a stage: plastic stage.According to the characteristics of mechanical deformation of incompletely filledcracks,a theoretical model of brittle-plastic incompletely filled cracks deformation and seepage was established.(2)Under the action of stress,the flow rate of the filling crack with the same property medium decreases in the same form.When the filling width decreases from20 mm,15mm and 10 mm successively,the displacement as the flow rate approaches the minimum value also decreases gradually.When the filling medium was changed from brittleness to elastic-plastic to plastic,The stationary phase of the seepage-stress curve of the fracture gradually shortened,and the stress value decreases when the seepage flow reaches the lowest level.Based on the experimental results,the changing law of seepage and stress in brittle-plastic incomplete filling fractures was studied,and a generalized model of seepage stress in brittle-plastic incomplete filling fractures was established.(3)The seepage curves of incompletely filled fractures with different properties show obvious differences.Brittleness(sandstone,cement mortar 1:2 and 1:4)incompletely filled crack deformation seepage curve showed three stages: stable stage,slow decline stage and rapid decline;elastoplastic(rubber)behaves in two stages:slow decline Stage and rapid decline.Plasticity(ceramic mud,cement mortar 1: 6 and1: 8)showed a stage: the flow rate showed a rapid decline with the loading of stress.(4)The experimental results of the brittle-plastic(sandstone,rubber,ceramic mud)filling crack deformation seepage have a high consistency with the comparison curves of the calculation results,but the different ratios(1:2,1:4,1:6,1:8)There was a certain error between the experimental results and the calculation results of the cement mortar,which was mainly caused by the characteristics of the cement mortar itself.