| The Wulidian Station is a super-shallow buried tunnel with a maximum excavation area of about 433 m2.The construction difficulty of the station is shallow,the section is large,the top of the vault is miscellaneous fill,the hole is located in the soil layer,the excavation risk is high,the open-cut distance is short,the site construction site is extremely small,the rock-rock excavation amount is large,and if the construction step is according to the original design,After the excavation and support of the left and right side wall guide pits,the construction of the core soil shall be carried out.At that time,the upper core soil working face is 14 m on both sides,the safety protection coefficient is large,the safety protection cost is high,and the construction difficulty is great.The entrance and exit connected with the concealed excavation of the five-li store station are many,and the construction parts are various,and the original design and construction scheme cannot meet the requirements of the synchronous construction.Based on the actual situation of the site and the ANSYS analysis data of the finite element software,the four finite element models are compared,and the stability analysis of the optimized construction scheme is obtained.The main contents are as follows:(1)Temporary horizontal brace number optimization,from the original two temporary horizontal support into one.The result of ANSYS analysis shows that the reduction of transverse brace has little effect on the vertical displacement of surrounding rock,the vertical displacement of initial support,the vertical displacement of temporary support and the overall change of secondary lining stress,but it only affects the horizontal displacement of surrounding rock in the process of partial excavation.Horizontal displacement of initial support and temporary support.(2)Demolition of the 12m core soil in advance to form a transverse channel,and a 12m wide temporary lateral emergency escape route between the upper guide pits every 24m(and the right and wrong conversion lanes of the entrance construction vehicles),the removal of the core soil to the overall construction process The maximum displacement and stress change have no effect,but the surrounding rock and temporary support are greatly affected during the upper excavation process.The initial bulge value of the first branch and the second excavation support process is increased by 0.434mm,increasing.About 25%,the maximum horizontal displacement of the temporary support increased by 0.586 mm,and the maximum vertical displacement increased by 0.74 mm.(3)The core soil is optimized in the form of core soil,the core soil in the vertical form has a certain self-stabilization capacity,the maximum of the horizontal deformation of the surrounding rock,the maximum value of the vertical deformation of the surrounding rock,the initial branch level and the initial support vertical deformation are basically the same as compared with the 8 m arc-shaped core soil.The vertical temporary support deformation of the vertical type core soil is more obvious,the vertical temporary support deformation of the vertical type core soil is increased by 54.5%,the vertical type core soil in the expanded foundation form is relatively stable,When the core soil is small in size,the displacement value of the vertical relative arc core soil is basically the same,the stress value is relatively small,the first principal stress is small 0.58Mpa,and the third principal stress is less than 0.02Mpa.(4)The inverting arch lining is applied from the inside of the cave to the outside of the cave.In the relatively good geological conditions,the 30m core soil is removed as a trolley assembly area at the small mileage end.Providing experience for the underground excavation station with limited geological conditions and limited space for the assembly of trolleys.Figure 31 table 55 reference 86... |
PDF Full Text Request