Model test study on bearing effect prestressing anchors in shallow buried tunnels
The use of prestressing anchor active support technology in tunnel engineering is becoming morecommon.However,the support characteristics and mechanism of action have not been fully under-stood for shallow,large-span rocky tunnels.In order to investigate the bearing characteristics of the sur-rounding rock under the prestressed anchor support system,a concealed excavation station of Qingdao Metro Line 6 was used as the engineering background,and based on the similarity principle of formula-ting experimental materials for stratum and support structure modelling,the bearing characteristics of the anchors under the prestressed anchor and ordinary anchor support were investigated by hydraulic loading tests.The results indicate that:① The interaction between prestressed anchors and the sur-rounding rock creates a load-bearing anchor solid that can effectively support most of the overlying loads.The application of prestressed anchors during the overburden loading process increased the warn-ing load value of tunnel instability damage by 42.8％and the ultimate load value by 41.2％.② The o-verburden loading process involved the prestressing anchors going through the tight anchorage load hold-ing stage and the de-anchorage unloading stage.Simultaneously,the lining underwent the strain accumu-lation stage,strain surge stage,and strain release stage during the overlay loading process.③ The pres-tressed anchor under active support has better force synergy with the rock body than an ordinary anchor,without the axial force mutation phenomenon.This allows the support performance of the anchor to be fully utilized.Additionally,the prestressed active support effectively inhibits the development of fissures and significantly improves the overall stability of the tunnel.
Shallow buried large span tunnelprestressing anchorsactive supportanchor solidmodel test
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