大断面硐室锚喷支护试验研究

Trial and Study of Bolt Shotcrete Support For Large Cross-Section Underground Room

近500m^3的皮带机头硐室,通过围岩松动圈的观测,改现浇钢筋混凝土支护为锚喷支护的施工方案、施工方法和经济效果.

An underground room with a length of 25 m, a width of 10 m and a height of 12 m of a conveyor drive head was excavated through sandstone, shale and seam, The room was excavated with a bench constructtion method which started from top to bottom. But it would first require to excavate an inclined pilot hole (with a cross-section of 3m×2m) from the low level to the top level begining at the central floor of the end wall. Then, it was to divide the 12m height room into 5 benches, The enlargement excavation started at the top bench. The excavation was to excavate one bench and complete the support for the bench. The scheduled design of the room was to use a means of reinfored concrete lining with a thickness of 700 mm. After measurements by the ultrasonic wave device, the results shown that the relaxation zone of the surrounding rock was 1.1 m in depth. Then a means of bolt mesh shotcrete support was instead of the scheduled means of support. The bolt was 1.6 m in length, the steel was 16 mm in diameter and the bolt was a quick cement bolt. The anchorage strength of the bolt was higher than 4 t. An X type arrangement of the bolts was adopted with a spacing and row distance of 0.7 m. The shotcrete was 120 mm in thickness. At a corner point, the length of the bolt was increased to 1.8 m. A double metal mesh was used at a broken zone of a fault. After the convergence measurements, the results shown that the arch of the room had a max. deformation value of 12.8 mm and the wall was stable with a deformatio nvalue of 21.8mm.