JMZX-5040am dual-mode pressure cells were, respectively, installed on the tunnel vault
, tunnel arch (right), and right side wall of the K14 + 400 section to test the pressure change between the surrounding rock and the initial support.
Therefore, in this study, considering real excavation and three dimensional modeling effects, the results of two and three dimensional tunnel excavation models such as tunnel vault
and invert displacement (i.e., the measure of convergence at the tunnel section) and stress state around the tunnel opening were compared by means of a finite-element method based on 2D and 3D tunnel models.
Through ultrasonic and boring core sampling, Nie and Lai [24, 25] investigated the crack and water leakage of a tunnel and detected the strength and thickness of liner structure as well as the backfill tightness of tunnel vault
. To obtain the operating state of a tunnel in the cold plateau region, Kang and Yan [26, 27] used the GPR to detect the tunnel disease and assessed the integral safety of liner structure.
A geological survey shows that the average buried depth of this tunnel in vertical direction is approximately 600 m, and the average buried depth of the groundwater is approximately 132 m from the tunnel vault
. The strata are generally divided into five layers from top to bottom: the strongly weathered sandstone layer, the weakly weathered sandstone layer, the metamorphic sandstone layer, the metamorphic quartz sandstone layer, and the weakly weathered fine quartz sandstone layer.
In this project, the monitoring items include the settlement, inclination and cracking of the surrounding buildings, the vertical displacement of the adjacent underground colligation pipelines, the settlement of the ground surface, the underground water level, the sink deformation of the tunnel vault
, the tunnel bottom heave, and the tunnel clearance convergence.
(2) When the water head difference over the excavation face reaches the limit value of 18 m, longitudinal joint opening at tunnel vault
reaches the maximum value of 4 mm.
In fact, the position of the maximum bending moment at 90[degrees] of the lining section was transferred to the range of 200[degrees] to 240[degrees] (the apex of the tunnel is at right side of lining, thus, the tunnel vault
is taken to be 90[degrees]).