| With the vigorous promotion of subway construction,the process of shallow buried concealed excavation method is becoming more and more mature.The road surrounding the Station on Xi’an Metro Line 8 has steep side slopes,and there are numerous tunnel segments in the space between them.All of these tunnel sections were built using the concealed excavation method.It is crucial to conduct research on the impact of construction stability of PBA concealed excavation metro station and interval articulation section in high slope terrain due to the technical challenges of high slope terrain forming bias pressure on PBA concealed excavation station and interval tunnel,complicated process conversion of PBA method,and high requirements of concealed excavation of interval tunnel near the station.We study the mechanical behavior of the construction shaft of the PBA station,the PBA concealed excavation station,and the PBA station and interdistrict tunnel interface section in this paper using literature research,indoor testing,simulation,and field measurement.We also reveal the development law of slope and surface displacement,analyze the construction stability of tunnel structure,and investigate the interactions between various processes to provide a guarantee for the project.The study seeks to serve as a guarantee for the subway’s safe construction and a guide for projects of a similar nature.The following are the key findings of the study:(1)The research methodology of integrated consideration and overall analysis of high side slopes,construction shafts,PBA concealed stations,and inter-district tunnels was proposed,taking into account the actual engineering conditions,after the existing studies and similar cases were compiled and summarized.Through on-site sampling and indoor tests,the project’s essential physical and mechanical properties of the soils were established,providing accurate experimental data for the simulation that followed.(2)Using finite element simulation and on-site monitoring and measurement to study the stability of the construction shaft of the high side slope PBA station,the results show that the maximum horizontal displacements of the top edge of each quadrant in the northeast,northwest and south quadrants after excavation of the construction shaft of the high side slope PBA station are 10.07 mm,11.59 mm and 8.22 mm respectively,and the maximum settlements are 8.05 mm,10.19 mm and 7.95 mm respectively,7.95 mm;the maximum horizontal displacements of 1#,2# and 3# shaft containment piles are 6.50 mm,6.46 mm and 5.66 mm respectively,and the deformation values are within the safe range.After comparing the numerical simulation with the measured data on site,it is found that the simulated value of surface settlement is 8.95%larger than the measured value on average,and the simulated value of the short-sided containment pile of #1 shaft is 27.30% larger than the measured value,so the numerical simulation results are relatively accurate.(3)Analysis and research on the stability of the high side slope PBA concealed excavation station by using finite element simulation and on-site monitoring and measurement,the results show that: in the refinement model of PBA method,the maximum settlement of the ground surface is 18.48 mm after the passage of the station guide hole;in the excavation model of the high side slope PBA station guide hole,the settlement groove appears on the ground surface after the passage of the station guide hole,and the maximum settlement value is 7.93 mm,the influence of topography In the refinement model of the PBA method,the maximum settlement value at the surface is 33.52 mm and the maximum uplift value at the bottom slab is 32.17 mm after the middle slab is applied;the maximum settlement at the surface is 31.36 mm after the bottom slab is applied,which is 10.04% less than that at the completion stage of the middle slab application;the maximum uplift value at the bottom slab is 44.24 mm,which is 44.24 mm less than that at the completion stage of the middle slab application.The construction of PBA station will affect the completed shaft pits and cross passages to a certain extent,but the impact of PBA concealed excavation station on the surrounding environment is within the safe range under the actual high side slope terrain.The comparison between numerical simulation and field measurement data shows that the simulated value of surface settlement is 33.85% larger than the measured value on average,and the simulated value of vault settlement is 23.16% larger than the measured value on average,so the numerical simulation results are reliable.(4)With the help of finite element software,the stability of the completed PBA station near the interval tunnel is analyzed and studied.The results show that: after the excavation of the interval tunnel articulation section is completed,the maximum horizontal displacement value of the edge of the slope roof is 7.10 mm,and the maximum settlement is 10.96 mm;the surface settlement curve in the center of the road is "concave",and the maximum surface settlement is 5.96 mm above the cross passage.The surface settlement is the largest,and the surface settlement above the interval tunnel is the second largest,and the maximum surface settlement is 13.96 mm;after the excavation of the interval tunnel joint section is completed,the settlement value of the left tunnel arch is 5.83 mm,and the settlement value of the right tunnel arch is 4.15 mm.(5)Combined with the analysis of the high side slope shaft,PBA concealed excavation station and interval tunnel interface section,the shaft is affected by high side slope,but the construction safety can be controlled;PBA station guide hole excavation,making the shaft pit support lateral deformation increased by 42.46% on average,but none of them exceeded the warning value;in the high side slope terrain conditions,the surface settlement in the center of the road is smaller,and the PBA concealed excavation station on the surface settlement impact is within the acceptable The impact of PBA concealed excavation station on surface settlement is within the acceptable range.After the completion of the construction of shaft #1 and the interval tunnel,the southeast part of the completed PBA station was more affected by the construction of the interval tunnel,with the maximum settlement value of 5.35 mm at the top slab,5.82 mm at the middle slab and 6.14 mm at the bottom slab of the station. |
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