Three-dimensional Experimental Study On Characters Of Water Pressure Upon Tunnel Lining In Through Fractured Rock Mass

According to the features of fractured rock tunnel,cement mortar have been used to be the medium of surrounding rock.The connected fissures have been simulated by cement mortar and earthwork cloth.By using three-dimensional test and setting the similarity ratio as 1:50,model tests have been proceeded in a model test box.Pore water pressure gauge and static strain gauge have been used to measure the water pressures in model test box.Then distribution maps of water pressure have been drawn,and the effect coefficient have been obtained through calculating.Through analyzing the test data,the distribution characteristics of water pressure behind the lining,on fissures surface and in surrounding rock of one and two connected fissures have been obtained respectively.Main results:(1)A percolation model test equipment which used for fractured rock tunnel has been designed.The test equipment,along with pore water pressure gauge and static strain gauge,have formed a complete set of system to test lining water pressure.This system can work normally under a water pressure of 0.2MPa.(2)In the condition of non-drainage in tunnel,the water pressure of any point in surrounding rock approximately equal to its hydrostatic pressure.Effect coefficient of water pressure β≈1.0.In the condition of drainage in tunnel,the effect coefficient of water pressure β≈0.424.The results showed that water pressure in tunnel lining declined when drainage in tunnel.(3)The effect coefficient of lining water pressure declined when the bottom of surrounding rock were permeable,which means whether the bottom of surrounding rock were permeable is a influencing factor of lining water pressure.(4)Water level shows little influence to function coefficient of lining water pressure,but the function coefficient decline with the increase of water level.(5)The horizontal and vertical location can both influence the water pressure of test point in fissures surface,and the water pressure rise with height.Besides,water pressure rise fast with the increase of height.The water pressure in midcourt line smaller than its two sides when in the same horizontal location.