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Abstract The caving zones of two layered coal seams within a short distance after the coal mining overlap so that the disturbed zone caused by tunnel construction under the area of the double-deck mined-out seams is larger than the case of single mined out seam；which affects the supporting structure of the tunnel and the stability of surrounding rocks. Indoor tests of similarity model to simulate the tunnel construction was carried out and the ground movements of the mined-out area and the internal forces of the initial supporting structure were measured with the displacement meters，the earth pressure cells and the embedded electric resistance strain gauges. The test results demonstrate that the settlements of mined-out area mainly occur during the second stage of the tunnel excavation，i.e. the excavation of the upper section of the tunnel and the closing of the initial support. The smaller the dip angles of seams are，the larger the settlement rate. The steeper the settlement curve，the slower the convergence speed in the later period and the bigger the settlement value. The supporting structure of the tunnel carries a certain amount of eccentric loads in the inclined double-deck mined-out area，and the bigger the dip angle，the more pronounce the eccentric load. The maximum earth pressure mainly occurs in the invert arch. The anchoring effect of rock bolt is poor due to the mined-out area loosens. The maximum bending moment of the steel arch appears at arch heel and the axial force closed to the mined-out area is quite low which is not beneficial to the stability of the support structure. With the increasing of the dip angle of the mined-out area，the scope of positive bending moment of vault is closer to the coal mined-out area. The maximum bending moment and the eccentric distance increase notably while the stability of the supporting structure decreases.
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Received: 24 December 2013
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2014, Vol. 33 
