Optimal Analysis of Tunnel Construction Methods through Cross Passage from Subway Shaft

Advances in Mechanical Engineering

et al. 2019

Self Cite

The Provincial Hospital Station of Guiyang Metro Line No. 2 in China is located on the upper-soft lower-hard stratum. In order to analyze the adaptability of primary support arch cover method for the project, the construction process of the main tunnel of the Provincial Hospital Station is simulated by virtue of numerical simulation. Meanwhile, the excavation process of the tunnel is simulated by the double-side drift method for comparison. The numerical simulation results show that the primary support arch cover method has advantages in settlement control, plastic zone distribution, and supporting structure safety. Only the primary supporting structure is relatively weak in the rock-soil interface and on the arch shoulders and vault, and liable to tension failure. However, the application of strengthened primary support can significantly improve this unfavorable situation. Therefore, it is suggested that the primary support arch cover method be adopted for the construction of the main tunnel of the Provincial Hospital Station. The numerical simulation results obtained by primary support arch cover method are consistent with the field data in terms of the change trend of surface settlement, and the final settlement value is also similar. On this basis, the influence of grade variation of underlying surrounding rock on surface settlement and surrounding rock plastic zone distribution caused by the two methods is further simulated, and the grade range of underlying surrounding rock suitable for primary support arch cover method is given in the article.

Section: Analysis Of Calculation Resultsmentioning

confidence: 99%

Study on adaptability of primary support arch cover method for large-span embedded tunnels in the upper-soft lower-hard stratum

Wang

Advances in Mechanical Engineering

et al. 2019

Self Cite

“…In this procedure, TBM tunneling pressure (P T ) was 0.30 MPa, grouting pressure (P G ) was 0.20 MPa, and jacking pressure (P J ) was 200 kN/m which was applied in as linear loading. e basic assumptions of the simulation were as follows: (1) the influence of groundwater on the stability of surrounding rock after TBM excavation was neglected [27] and (2) hardened grouting area between segment and surrounding rock was replaced by an equivalent layer of 0.15 m after TBM tunnel excavation [29,33].…”

Section: Tbm Excavation Programmentioning

confidence: 99%

Stability Analysis of TBM Tunnel Undercrossing Existing High‐Speed Railway Tunnel: A Case Study from Yangtaishan Tunnel of Shenzhen Metro Line 6

Zhao

Cheng

Advances in Civil Engineering

et al. 2021

Self Cite

During the construction of the underpass of a new tunnel, the excavation unloading effect disturbs surrounding rock masses and promotes surrounding rock deformation, inevitably changing stress and displacement in the existing tunnel. Taking Yangtaishan tunnel excavation of Shenzhen Metro Line 6 as an engineering example, effects of excavation programs of left and right lines on the deformation characteristics of newly excavated and existing tunnels were evaluated based on Midas numerical model and priority excavation advantages of the left line were determined. The settlement and horizontal deformation characteristics of the existing tunnel were analyzed using the construction monitoring method. Results showed that maximum settlement and horizontal deformation of the existing tunnel were 1.35 and 0.23 mm, respectively. Settlement of invert and inverted top along axis direction was from growth to decline, and then a V-shaped settlement trough was formed with maximum settlement values of 1.36 and 0.97 mm, respectively. Maximum settlement and uplift of the newly built tunnel appeared on the upper and bottom parts of invert, respectively. In the newly built tunnel segments, the top settlement was dominated and deformation was mainly distributed in both side areas. At the top of the existing tunnel segment, convergence settlement was 3.09 mm and settlement rate was slow first which was accelerated, then stabilized, and finally slowed down again which was opposite to the uplift development trend of the bottom of tunnel segment. The top of the existing tunnel segment showed four settlement stages, slow, rapid, stable, and slow settlement stages. Compared with the right line, preferential excavation of the left line had obvious advantages in terms of tunnel stability. The unloading effect of TBM excavation created vault settlement in the existing tunnels where actual settlement values were 1.12 and 1.13 times, which theoretically calculated settlement. The horizontal deformation of the existing tunnel was varied first linearly and then nonlinearly with maximum deformation in the convergence stage of 1.47 mm.

“…e initial stress field is calculated according to the self-weight stress field. e construction interval is basically within the envelope structure, and the driving load on the ground is not considered; that is, the effect of variable load is not considered [8,24]. In order to ensure the calculation accuracy, fine elements are used around the tunnel.…”

Section: Establishment Of Calculation Model Using Midas Gts/mentioning

confidence: 99%

“…In the process of construction, with the stress conversion of the structure, there are many times of surrounding rock disturbance, and the amount of settlement increases, which is easy to cause accidents; it is the key and difficult point of concealed excavation construction. erefore, it is very important to make a reasonable construction scheme and reasonable planning of the construction step [8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Risk Analysis of Tunnel Construction Scheme Change based on Field Monitoring and Numerical Analysis

Advances in Civil Engineering

Tian

et al. 2021

Self Cite

Because of the surrounding environment restriction, some sections of the Lanzhou Metro Line 2 were forced to change the original open excavation method to the concealed excavation method. Among them, the ingate is the transitional section connecting the shaft and the cross passage, which is accompanied by the force conversion of the structure during the plan change process, and accidents are prone to occur. Combining this project situation, a construction scheme for turning the shaft from the cross passage into the ingate of mine line was proposed, and the finite element software is used to simulate the scheme. Numerical analysis shows that the stability of the tunnel supporting structure, shaft, and cross passage all meet the design requirements. The final ground settlement caused by the proposed construction method is 7.1 mm, and the settlement of the vault is 11.97 mm. It also turns out that the proposed construction method causes less deformation, and the method can be applied to the construction of the ingate conversion. The rationality of the method and numerical model was further verified by the comparison between the monitored data of surface settlement and vault sinking and numerical simulation results. Finally, the modified concealed excavation method and the original open excavation construction method is compared. It is concluded that the concealed excavation method is superior to the original open excavation method in terms of construction schedule, construction safety, economic benefits, and impact of construction on the surrounding environment. It indicates that it is a good choice to replace the construction method early if necessary. The successful implementation of this project can provide a reference for the design and implementation of similar urban subway projects.