Construction Mechanics and Evolution of Surrounding Rock Loose Circle of In-situ Tunnel Expansion:Taking the In-situ Expansion Project of Tingxin Tunnel on Hezhou—Bama Expressway in Guangxi as an Example
Construction Mechanics and Evolution of Surrounding Rock Loose Circle of In-situ Tunnel Expansion:Taking the In-situ Expansion Project of Tingxin Tunnel on Hezhou—Bama Expressway in Guangxi as an Example
The early-built highway tunnels cannot meet the traffic demand due to the surge in traffic volume,and in-situ expansion of the highway is adopted to address this problem.However,the evolution law of the loose rock zone and the stress redistribution law during in-situ tunnel expansion are not clear yet,which often leads to safety accidents and engineering quality problems such as large deformations or even collapses.In order to study the mechanical behavior of in-situ tunnel expansion and the evolution law of the loose rock zone,the discrete element software GDEM was used to establish models of newly built two-lane,three-lane and four-lane tunnels,as well as"two expansions and three lanes"and"two expansions and four lanes"tunnel models.The simulation results were qualitatively compared and verified with on-site stress monitoring analysis to study the mechanical behavior of highway tunnel in-situ expansion and the evolution law of the loose rock zone.The results show that the stress of the surrounding rock mass is in the order of crown＜haunch＜invert,and the increase in excavation width or the decrease in rock mass grade will lead to the increase in rock mass stress.Under the same excavation width,the stress of the surrounding rock mass of the newly built tunnel is smaller than that of the in-situ expanded tunnel.The loose rock zone around the tunnel gradually expands with the decrease in rock mass grade,and its shape changes from"point"to"ear"and then to"butterfly".When the rock mass grade is the same,the loose rock zone around the newly built tunnel is smaller than that of the expanded tunnel.The expansion of the tunnel will cause the rock mass to undergo multiple stress redistributions on the basis of the original multiple stress redistributions,and the complex evolution of this stress will result in completely different stress and strain fields between the newly built tunnel and the expanded tunnel,while the expansion of the tunnel will cause the loose rock zone around the rock mass that is originally in a stable state to expand outward again.
关键词
隧道/原位扩建/围岩松动圈/围岩荷载
Key words
tunnel/in-situ expansion/loosening zone of the surrounding rock/surrounding rock load
维普
万方数据