Environmental and Numerical Analysis of the Effects of Groundwater Level Changes on Face Stability in Tunnel Construction Using the TBM-EPB Method: The Impacts of Tunnel Diameter and Pressure on the Excavation Machine.
Subject Areas : Natural resources and environmental hazards
احمدی Ahmadi
1
,
AMIR VAKILI
2
,
روزبه آقامجیدی
3
1 - Department of Food Hygiene, Ayatollah Amoli Branch, Islamic AZAD University, Amol, Iran.
2 - civil department , islamic azad university , beyza , branch , Iran
3 - هیئت علمی
Keywords: changes in underground water level, drilling front pressure, drilling diameter change, Abaqus software,
Abstract :
Introduction: Nowadays, there are various methods for digging tunnels in urban environments. Factors such as the cross-section of the tunnel, the amount of progress, the amount of capital required, the duration of the project, and most importantly the type of soil and rock and the condition of the underground water, play a fundamental role in choosing the drilling method in urban environments. Based on this, the aim of this research is to numerically investigate the effect of changes in the underground water level on the pressure on the excavation front by changing the diameter of the tunnels.
Materials and Methods: In this study, three general cases have been examined. In the first case, only one tunnel was executed and the tunnels were executed near the heel of the pile. In the second case, two tunnels were executed and the position of the tunnels is near the heel of the pile, and finally, in the third case, both tunnels were executed near the middle of the pile. For this purpose, in this study, the changes in soil settlement due to the implementation of twin tunnels in the three mentioned cases has been investigated.
Results and Discussion: The results of the research showed that the intensity of the maximum settlement increase is significantly dependent on the drilling diameter; In a drilling with a diameter of 5 meters, the maximum settlement is about 11 mm, and this value reaches 12 mm with an increase of 9% in a drilling diameter of 7 meters. If the tunnel is dug with a diameter of 12 meters, the maximum settlement increases by 44% and reaches 16 mm compared to the case of digging with a diameter of 5 meters.
Conclusion: In all modeling modes, as the groundwater level approaches the ground surface, the maximum settlement decreases. If the underground water level is at the bottom of the model, increasing the drilling diameter will not change the location of the maximum settlement along the depth, and this settlement will remain at the crown of the tunnel. Finally, with the increase of the drilling diameter, the need for more pressure for the stability of the tunnel excavation front also increases. An important point that can be seen in this research is that the longitudinal settlement at a distance equal to the sum of the overhead and the diameter of the tunnel reaches less than one millimeter from the excavation front, and it can be concluded that the length of the area affected by the tunnel excavation reaches the level of the underground water level. And the drilling diameter is not dependent.
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