(1. School of Civil Engineering，Shandong Jianzhu University，Jinan，Shandong 250101，China；2. Shandong Hi-speed Engineering Construction Group Co.，Ltd.，Jinan，Shandong 250000，China；3. School of Civil Engineering，Southwest Jiaotong University，Chengdu，Sichuan 630000，China；4. School of Urban Geology and Engineering，Hebei GEO University，Shijiazhuang，
Hebei 050031，China；5. China Railway 14th Bureau Group Co.，Ltd.，Jinan，Shandong 250000，China)
Abstract：The gap between the segment and the surrounding rock in shield TBM tunnels is backfilled with pea gravel and then grouted to form backfill. The backfill and its state have an important impact on the mechanical characteristics of the tunnels. In order to find out the influence law of the backfill layer on the stress and deformation of tunnels，the mechanical characteristics of shield TBM tunnels in construction are analyzed through field test in this paper，and the following conclusions are drawn. When the backfill layer is in a loose state，the constraints and supports of the surrounding on the segments are limited，and the segments cannot provide enough support for the surrounding rock. As a result，the surrounding rock is prone to deformation and collapse，and the structural stress，opening，staggering and surface settlement of the segments will increase significantly. The stress system of the surrounding rock，the segment and the backfill layer is gradually stable after the backfill layer is grouted and consolidated. The volume of the pea gravel behind the segments has an important effect on the force and deformation of shield TBM tunnels in construction. The smaller the filling volume of the pea gravel is，the more obvious the stress concentration is，and the greater the opening，staggering and surface settlement of the segments are. The volume control standard of the pea gravel behind the segments should be formulated in the construction of shield type TBM tunnels，and the grouting time should be selected according to the volume control standard and the volume of the pea gravel filled behind the segments.
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2021, Vol. 40 
