Analysis Of Seepage Control Measures And Long-term Stability Of Tunnel Lining Under High External Water Depth

A water conveyance tunnel has obvious highland stress and occurrence environment with high external water pressure as it is deep buried and excavated from the long complex geological conditions surrounding rock.The presence of high external water pressure could easily cause Gushing water,landslides and other engineering accidents,serious threat to the security of the tunnel structure.It is important to carry out drainage and waterproofing design and determine a reasonable seepage control scheme for the protection of engineering safety.As an important mechanical property,rheology is usually an important factor in causing engineering instability.Affected by the highland stress and high environment with high external water,the rheological property becomes more complicated and it is not easy to ensure the stability of surrounding rock and the safety of supporting structure under long-term rheology.(1)Based on the analytic formula and the numerical simulation,the effects of the water head height and of the permeability of surrounding rock to the tunnel seepage have been analyzed contrastively,verifying the feasibility of the numerical simulation.On this basis,combined with engineering typical sections,analyzed the influence and the law of the composite lining structure,drainage measures to the seepage flow and the external water pressure on lining,determined the reasonable depth of the drain and arrangement and gettted the effective measures of “blocking ground water and limiting discharge”.(2)Based on the concept of water shutoff,combined with practical engineering data and lining structure security requirements,the thought of determining seepage control has been putforward.Based on the numerical simulation,analyzing the comprehensive measures of water blocking and drainage about the different geological section,the preliminary scheme is determined through the comparison with seepage control standards.The dynamic simulation of the construction process is carried out to verify the rationality of the seepage control measures.(3)According to creep test data and the reasonable creep rule we chose,the creep model can been determined by means of curve fitting.The creep model is verified for its rationality by numerical simulation of creep test process and comparing simulate results to test data.(4)According to seepage control measures of the section and fitting creep model,simulating the dynamic process of tunnel construction with ABAQUS.The reasonable supporting time can been determined by considering comprehensive consideration of seep-creep and analyzing surrounding rock and long-term mechanical response of secondary lining.