Study On Load Bearing Features And Damage Mechanism Of High Water Content Filling Material

As a new filling material developed in recent years,high water content filling material has a series of advantages that ordinary materials do not have: early strength,good fluidity,coagulation easy,small volume strain,etc.At the same time,the high water content material has good compression resistance under three-dimensional compression,which is suitable for high temperature,humidity and closed goaf environment.In this paper,the basic mechanical properties,load-bearing characteristics,the relationship between deformation stability and time,and the mechanism of instability and failure under loading of high-solid water filling materials are systematically studied by means of simulation experiments,Main achievements are as follows:(1)On the basis of the preparation process of high water content filling materials,we studied the basic mechanical properties such as setting time,fluidity and hydration products.Acroding to chemical composition and hydration products of high water content filling materials,we discussed hardening mechanism of high water content filling materials.(2)By the uniaxial bearing test of high water content filling materials,we studied the deformation characteristics and got the law of strength deformation characteristics with the changes of water content.According to triaxial bearing test,we studied the dependences rules on peak strength and residual strength with different confining pressure.Got the failure process of high water content filling materials bases on elastic energy and dissipative energy by cyclic loading experiment.(3)We fitted the variation of high water content filling materials by original model.Based on the theory of H-B model,an improved model of H-B residual strength suitable for characterizing ductile failure characteristic material was developed by using the degree of cohesion loss to characterize the integrity of samples.(4)According to step loading,we researched creep characteristics rules of high water content filling material under different water content conditions.We analysed the creep deformation and instantaneous deformation of high water content filling material under different stress levels and studied creep curves under different water content.We also researched the creep rate,steady creep rate and creep strain curve,proposed a method suitable for the study of long-term strength of high water content filling material,established model for creep deformation curves under different stress conditions.(5)On the basis of the different angle of fracture surface,we researched the macroscopic failure mode of high water content filling materials.Based on SEM and CT scanning,combined with the macro-damage characteristics,studied the damage and failure of high water content filling material by several different angles,such as primary pore development,meso-structure composition and free water migration inside.