Analysis Of Surrounding Rock Stability Of Argillaceous Sandstone Tunnel Considering Moisture Diffusion Effect

Water content is an important factor which controls the stability of underground engineering rock mass.The affection of water content on rock strength has become research emphasis in the field of rock mechanics and practical engineering,which has great importance on theoretical and practical significance.Based on the previous researches on the influence of liquid water on rock,this paper focus on the other natural state of water-the gaseous water — the humidity,which may also affect the rock structure performance.The weakening of the physical and mechanical properties of the rock mass has been researched,which adversely affects the stability of the surrounding rock.Through the methods of experiment and numerical simulation,the mechanical properties of argillaceous sandstone under the effect of humidity diffusion has been study.The main research contents are as follows:(1)To investigate the law of humidity diffusion in argillaceous sandstone,the experiment of humidity diffusion effect of argillaceous sandstone has been carried out.The results show that the humidity diffusion curve has four stages: the first stage shows a descending trend,the falling stage time increases with the depth due to different humidity between the internal and external of the sample;the second stage shows a fast rising trend,the humidity begins to rise linearly after falling to the critical point.The humidity ratio and height change synchronization.The third stage shows a stable trend with the rate of humidity diffusion gradually decreases.The time required for this stage decreases with the increasing of depth.The fourth stage is a stabilization phase,in which the humidity tends to become stable and no longer grows.The functional relationship between humidity and water content was also studied.(2)To investigate the influence of water on the mechanical properties of argillaceous sandstones,uniaxial compression tests and conventional triaxial tests of argillaceous sandstones with different water contents have been carried out.By comparison and analysis in the uniaxial compression test and moisture content.The water content greatly influences the strength and deformation of argillaceous sandstone.The uniaxial compressive strength,elastic modulus and Poisson’s ratio of the specimen decrease with the increase of water content,and the elastic modulus and Poisson’s ratio the values are all smaller than the general sandstone and mudstone.In the conventional triaxial compression test,both the cohesive force and the internal friction angle decrease with the increase of water content,that the certain functional relationship between them were established.There is no correlation between the damage form and the argillaceous sandstone.(3)In order to investigate the influence of humidity diffusion on actual engineering,the FLAC3 D software was used to establish a water tunnel model to simulate the humidity diffusion process of argillaceous sandstone.It was found that humidity diffusion has a certain degrading effect on the surrounding rock of argillaceous sandstone,and the diffusion of humidity causes the increasing of surrounding rock displacement and stress range.Relevant construction suggestions were put forward by numerical simulation.