Tunnel primary support structure with built-in steel pipe frame

Abstract

The invention discloses a tunnel primary support structure with a built-in steel pipe frame, and aims to effectively improve mechanical properties of a primary support, avoid buckling instability of a steel frame and fully achieve the structural strength of the primary support. The tunnel primary support structure comprises a sprayed concrete layer covering cave surrounding rock, and steel frames embedded in the sprayed concrete layer at intervals in the tunnel excavation direction, and is characterized in that the steel frames are steel pipe frames of which the cross sections are circular; the steel pipe frame consists of a left-side wall section, an arch top section and a right-side wall section which are butted with one another, or consists of a left-side wall section, an arch top section, a right-side wall section and an inverted arch section which are butted with one another; the left-side wall section, the right-side wall section and the inverted arch section of the steel pipe frame are filled with concrete.

Description

technical field [0001] The invention relates to tunnels, in particular to a tunnel primary support structure. Background technique [0002] At present, underground excavation tunnels are basically constructed according to the principle of the new Austrian method, using composite lining support, including primary support and secondary lining. Among them, the support system composed of primary support and surrounding rock is the main bearing structure, and the secondary lining is mainly used as a safety reserve. [0003] The initial support is mainly composed of shotcrete layer, bolts and steel mesh combined support (referred to as shotcrete support). When the tunnel passes through unfavorable geological sections and weak broken zones, I-beams are generally installed in the shotcrete. , H-shaped steel and other auxiliary measures. [0004] In recent years, investigations on railways such as Liuzhan, Lanyu, Chenglan, Yungui, and Changkun have found that for some tunnels passi...

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Problems solved by technology

[0004] In recent years, investigations on railways such as Liuzhan, Lanyu, Chenglan, Yungui, and Changkun have found that for some tunnels passing through weak and broken surrounding rock, fault fracture zone, and soft rock with high ground stress, the initial support of medium-sized steel frames Buckling instability often occurs, leading to primary support failure

The reason is that since the section steel frame is I-shaped or H-shaped, the bending rigidity of its section in the X direction and Y direction is quite different, and because it is difficult to ensure that the I-shaped steel or H-shaped steel is close to the junction of the tunnel side flange and the web. The shotcrete is dense, so the grip force of the shotcrete to the steel frame cannot be effectively exerted

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