中文摘要：

双层煤层由于距离较近,采空后冒落带范围相互叠加,下穿隧道施工引起的围岩松动垮塌范围要大于单层采空区,对隧道结构受力和围岩稳定产生不利影响。开展公路隧道下穿双层煤层采空区的室内开挖模型试验,通过埋设地中位移计、土压力盒和电阻应变片,测量了隧道开挖过程中采空区地层移动和初期支护内力特征。测试结果表明,采空区地层沉降主要产生于上台阶开挖至初支闭合阶段,倾角较小时,地层沉降速率较大,沉降曲线较陡,而后期收敛较慢,沉降较大;隧道支护结构承受一定的偏压荷载,且倾角越大,偏压越明显,围岩与支护的最大接触压力出现在采空区对侧的仰拱处。由于采空区地层的松散性,锚杆的作用没有得到充分发挥。钢拱架最大弯矩主要发生在上台阶靠近采空区侧拱脚处;轴力分布不均匀,靠近采空区侧轴力水平普遍偏低,不利于支护结构稳定。随着采空区倾角的增大,初期支护拱顶正弯矩区域向采空区侧偏移,最大弯矩值和最大偏心距都显著增加,支护结构稳定性降低。试验揭示了隧道下穿双层煤层采空区开挖过程中采空区地层移动规律和初期支护受力特征,可用于指导类似工程设计与施工。

英文摘要：

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.