An Estimation of Ground Surface Settlement Due to Shielf Tunnelling by Peck-fujita Empirical Method
|關鍵字:||隧道;沉陷;潛盾機;經驗方法;Tunnelling;Settlement;Shield Machine;Empirical Method|
The first part of ths research proposes an empirical method with informations reported by Peck and Fujita, to estimate the surface settlement trough causd by shield tunnelling. Tunnelling observation data from 30 different cases have been used to justify the feasibility of the suggested method. The comparison between the measured ground settlement trough and the estiamted ground settlement curve proves that Peck-Fujita method can properly estimate the surface settlement troughs for various shield machine types, soil types, tunnel diameters, and tunnel depths. This research also reports the variation of surface settlement as a function of time, for tunnelling in different ground conditions with different shield machines. Field data indicaes that for shield tunnelling in cohesionless soil, ground surface becomes stable one week after the shield machine's passage. This is because the excess pore water pressure dissipates rapidly in cohesionless soils. For excavation with an EPB shield in cohesive soil, the ground stabilizes 40 days after the shield machine's passage. This is because the EPB shield does not disturb the ground too much. When using an open type shield machine, the compressed air method is generally adopted to keep the ground excavated stable. The time required to stabilize the ground is significantly influenced by the time when the compressed air is released. The second part of this study suggests a superposition method to estimate the ground settlement troughs due to parallel twin tunnel constructions. Field data from 27 cases of parallel twin tunnels are used to justify the feasibility of the proposed method. It has been found that if the distance between the two tunnels is far enough so that the plastic zones near the two tunnels are not overlapped, the suggested method could successfully estimate the surface sttlement caused by the two tunnels. Results from both methods indicate that if the distance between the tunnels is small, the total settlement trough reveals a single peak characteristic. However, if the clearance is large , a double peak settlement trough would appear. The third part of this paper introduces the instrumentation array deisgned by National Chial Tung University to Monitor the ground response of Nankang line 254 lot of Taipei MRT sytem. Not only instruments to monitor the ground response is introduced. but the data-collection plan is also discussed.
|Appears in Collections:||Thesis|