边坡岩石块体动力响应及锚固抗震效应研究

Research on Dynamic Response of Rock Blocks in Slope and Anti-seismic Effect of Anchor Reinforcement to Rock Mass

为研究路堑岩质边坡的抗震设防问题,在对汶川地震震区公路沿线岩质边坡进行震害调查的基础上,以川藏公路沿线某处典型岩坡为例,结合块体理论分析和动力数值计算,对边坡岩石块体的地震动反应特性及块体锚固效应进行研究。结果表明:节理会造成加速度的显著放大,未锚固的楔形块体加速度放大系数比完好岩体大3倍;锚固后,加速度放大系数比锚固前减小了30%。频谱分析表明,节理面降低了岩体的整体性,提高了地震动放大的幅值,扩大了加速度放大的频率范围,并使自振频率接近地震波的主频,从而增强了块体的地震动反应强度;锚固使节理岩体的自振频率远离地震波的主频,降低了节理面附近岩体响应加速度的幅值,从而提高了岩体的抗震能力。

To research the anti-seismic behavior of rock slope along cutting of highway,on the basis of field investigation on the damages of rock slopes of highway in Wenchuan seismic area,some typical slope along Sichuan-Tibet highway was taken for example to explore the seismic response behavior and anchorage effect of slope rock mass by combing block theoretical analysis with dynamic numerical calculation.It shows that（1） joints may cause significant amplification of seismic motion,enhance the amplitude of the earthquake motion and make the natural frequency of rock mass close to that of seismic wave with acceleration amplification factor of unanchored wedged block mass 3 times larger than that of wholesome rock mass;（2） acceleration amplification factor of anchored wedged block mass will decrease by 30% to that of unanchored wedged block mass.According to spectrum analytic result,the frequent range of seismic motion amplification in jointed rock mass is larger than that in the integrity of rock mass.Anchor reinforcement will make the natural frequency of jointed rock mass go away from the domain frequency of seismic waves,decrease the amplitude of seismic response acceleration of rock mass around joints,therefore improve the seismic capacity.