| Along with our country the construction of the hydropower bases in the southwest of our country,such as the Jinsha river,Yalong river and Dadu river,Lancang river,Nujiang river and Brahmaputra river hydropower bases,the construction of underground hydraulic tunnel reached a lot of records.However the geological environment of hydraulic tunnel is becoming more and more complex,the design and construction is becoming more and more difficult.In traditional research on the limitations of tunnel lining crack control research,the creep of surrounding rock and water action is not taken into account.So the limitations of traditional research is becoming more and more obvious,due to the creep characteristics of surrounding rock,the surrounding rock deformation occur repeatedly under the long-term action of outer load,which is easy to cause the instability of surrounding rock and tunnel lining cracking without reasonable control.According to reasonable creep model,It is the key to obtain creep parameters of surrounding rock through tests in situ test and indoor test.Due to the inevitable disturbance and the scale effects,the test data also has big deviation with the real situation.With the widely application of NATM,the inversion of surrounding rock creep parameters based on the displacement monitoring data become the main way of surrounding rock creep parameters inversion.At the same time due to large rainfall in southwestern China and the thicker layer of surrounding rock of hydraulic tunnel,the inward radial deformation of the tunnel lining will be occur under the effect of external water pressure,which will have an adverse effect on the stress of lining.After tunnel puts into use,the internal hydrostatic pressure and the dynamic water pressure on tunnel lining will lead to the radial deformation of outward.According to the hydraulic tunnel design specification,the run-time stable seepage pressure belongs to the basic loads,so this article also simulate the stable seepage field of run-time.Through simulation we found that tunnel lining of internal water pressure is still small under the condition of stable seepage,that is the reason why we only consider external water action as the hydrostatic pressure.The research results showed that reasonable creep parameters of surrounding rock can be back-calculated according to the field monitoring of displacement,besides the stress and strain of hydraulic tunnel concrete lining are of large deterioration under the action of a surrounding rock creep.Large tensile stress appears in the floor and wall of the lining,especially the bottom end section of floor where the maximum tensile stress is up to 1.78 MPa.So surrounding rock creep effect has a huge impact on anti-cracking of lining concrete.Under the action of water hydraulic the stress of tunnel floor is larger than sidewall,because internal and external water pressure on the floor both are larger than sidewall,but the big size of sidewall will lead to bigger stress and strain of the sidewall.The calculation results show that in the middle section of floor and sidewall tensile stress is larger,the tensile stress of bottom side is the largest which is up to 1.59 MPa.In short,the effect of rock creep,temperature and water on the hydraulic tunnel lining all have big influence on concrete anti-cracking security. |
PDF Full Text Request