块裂结构岩质地下洞室松动特征试验研究

Experiment study on loose characteristics of underground excavation in block-fractured rock mass

对不同倾角层理下的块裂结构岩质地下洞室进行了物理相似模拟试验,得到了洞室上覆岩层的运动行为和松动区变化规律,并对松动区界限建立了初步数学模型。试验结果表明:①当层理倾角小于岩块摩擦角时,岩层发生离层,各层内的部分岩块整体性沿节理面滑落;顶部松动区的左右界限为层理面和节理面构成的两个台阶面,上部界限为一层理面,台阶面倾角由块裂岩体的构造特征决定,上限可由改进的Voussoir梁模型计算得到,松动区内块体群作为一个整体,表现在块体理论上即为可动块体;②当层理倾角大于岩块摩擦角,而小于围岩自稳极限角时,洞室上覆岩层不发生离层现象,松动区内块体群整体性自由掉落;松动区左右界限为两个台阶面,上限为一层理面,但此时,界限附近部分岩块发生转动,可形成有效的压力拱,从而保证上覆岩层的稳定性;③当层理倾角大于围岩自稳极限角,洞室顶部松动区可确定为两组层理面所围成的区域,在松动岩体整体性沿节理面滑落的过程中,有部分块体受力状态改变,发生转动行为,从而出现岩块挤压现象,可阻止松动岩体整体性滑落。

Based on the physically similar simulation experiments for underground excavation in block-fractured rock mass,the kinematic behaviors of overlying rock stratum and the change laws of loose zone with different dip beddings are obtained.A simple mathematical model for the limit dimension of loose zone is established.When the dip of bedding is less than the friction angle of rock,the rock stratum will separate and some rock blocks in every rock stratum may slide along joint surface as a whole.Left and right limits of loose zone are two step-surfaces consisting of beddings and joints.The upper limit is one of the bedding planes,which can be calculated by the model of Voussoir beam.The dip of step-surface is determined by the structural characteristics of block-fractured rock mass.All rock blocks in the loose zone is a movable block-group in block theory.When the dip of bedding is greater than the friction angle of rock and less than the limit angle of stability,rock stratum will not separate.All rock blocks in loose zone will fall freely as a whole.Right and left limits of loose zone are two step-surfaces.The upper limit is one bedding surface.In the vicinity of limit of loose zone,some blocks can rotate,and form an effective pressure arch which guarantees the stability of the overlying rock stratum.When the dip of bedding is greater than the limit angle of stability,loose zone can be identified as the area between two sets of bedding surfaces.In the sliding process of rock mass,the force status of some rock blocks may change.Rotation behavior of rock blocks results in block squeeze phenomenon,and prevents sliding of loose rock mass.