| With the substantial improvement of China’s economic strength,The construction of railways and highways continues to develop in depth in the western mountainous areas,and the difficulty of tunnel construction continues to increase.The Miyaluo Tunnel No.3 on the Wenchuan-Malkang Expressway serves as a key throat to the Tibetan area,the importance is self-evident.The stratum in the tunnel site area is dominated by bad stratum.The disasters caused by high ground stress and weak surrounding rocks such as support encroachment and lining cracking have brought great challenges to the safety of the tunnel.Based on the Wenya Expressway Miyaluo No.3 tunnel project,this paper carried out the following research through literature investigation and theoretical derivation,combined with numerical simulation and on-site monitoring:（1）Based on the Burgers rheological constitutive model,a nonlinear viscous pot with stress as the threshold is introduced to describe the accelerated rheological stage of the rheological process of phyllite,and a modified Burgers model that can characterize the three stages of rheology is constructed.And complete the secondary development of revised Burgers rheological constitutive model.The FLAC3D finite difference software was used to verify the model’s viscoelasticity and viscoelasticity.The results show that the numerical model has undergone several stages,including transient rheological stage,decaying rheological stage,and accelerated rheological stage.The viscoelasticity and viscoelasticity of the modified Burgers rheological constitutive model are well verified.（2）Based on the modified Burgers rheological constitutive model,making full use of the time parameters in the constitutive model,the timeliness of the grouting circle is introduced into the constitutive model,and the grouting circle constitutive model has been developed to verify the results It shows that the model can well reflect the actual state of the slurry elastic modulus gradually increasing with time during the tunnel construction.The influence of the scope of grouting circle on the deformation of surrounding rock during tunnel construction and the safety of tunnel operation for 40years was explored.（3）Based on the modified Burgers rheological constitutive model,through the analysis of the deformation characteristics of the surrounding rock after the initial support at different timings under different depths（in-situ stress）,the support timing of the initial support is Q-50 At 24h,Q-100 is at 18h,Q-150 is at 15h,and Q-200 is at 18h;by analyzing the deformation law of the surrounding rock after initial support and applying secondary lining and creep calculation at different timings to calculate the impact after 200d The force characteristic analysis shows that the support timing of the secondary lining is 25d,40d,45d and 50d after the initial support is completed.Using the calculated timing of the initial support and secondary lining,the creep calculations of the four burial depths（in-situ stress）were conducted for 100 years,and it was found that the weak surrounding rock has significant rheological characteristics under the condition of high in-situ stress The load on the supporting structure gradually increases with time.（4）Through on-site monitoring,it can be concluded that compared with other tunnels with relatively complete stratums,the phyllite strata have the characteristics of large deformation,rapid deformation growth,and long deformation duration;the deformation and structural stress of the two-section surrounding rock There are significant differences:the stress of the initial support steel frame of section 058,the surrounding rock pressure,the contact pressure of the initial support and the second liner,and the internal force of the second liner all exhibit asymmetric characteristics.The stress of the initial support steel frame and the surrounding rock pressure of section168,The contact pressure between the first support and the second liner and the internal force of the second liner show a certain symmetry. |
