地震作用下锚杆支护边坡动力响应

Dynamic response of anchors-supported slope under earthquake

为研究填土边坡锚杆的动力响应特征与失效模式,进行了锚杆格构支护土质边坡振动台模型试验,采用正弦激励,分别对边坡的加速度和锚杆的轴向应变进行了监测。分析结果表明:在同一振动频率下,锚杆轴向动应变幅值随加速度峰值的增大而增大;加速度峰值较小时,应变基本在固定正负值之间往复循环,边坡处于稳定状态;随着加速度峰值增大,锚杆的最大与最小应变不再稳定,但变化不是很大,边坡仍处于稳定状态;当加速度峰值达到破坏峰值时,锚杆轴向应变不再具有规律性,滑面处锚杆轴向应变突变最明显,滑体与稳定体之间发生明显的相对位移。加速度峰值较小时,中下层锚杆轴向应变较大,中层锚杆应变约为顶层锚杆应变的2倍;随着加速度峰值的增大,顶层锚杆轴向应变逐渐变大,主要由中上层锚杆承受荷载;当加速度峰值达到破坏峰值时,各层锚杆的动应变最大值急剧增大,中层锚杆应变变化幅度最大,振动过程中滑体与滑床之间出现明显分离,锚杆被拔出。可见,传统的边坡锚杆设计思想"强腰固脚"适合于地震设防烈度较小地区,对于设防烈度较大地区,锚杆设计时需适当增加上层锚杆和腰部锚杆的锚固长度。

In order to investigate the dynamic response characteristic and failure mode of anchor in a soil-filled slope,a shaking table mode experiment on clathrate anchors-supported soil slopes was carried out.Sinusoidal motions were used as the incident waves,and the acceleration of slope and the axial strain of anchor were monitored.Analysis result shows that under the same vibration frequency,the axial strain amplitude of anchor increases with the increase of peak acceleration.When the peak acceleration is low,the slope is stable,and the strains of anchors recirculate between a positive value and a negative value.The maximum and minimum strains of anchor are unstable and change slightly with the increase of the peak acceleration,but the slope is still stable.When the peak acceleration reaches to the rupture limit,the axial strains of anchors are no longer regular,and the axial strains of key points on the sliding surface greatly and suddenly change,and the relative displacement is very obvious between the sliding body and the stable body.When the peak acceleration is less,the strains of middle and lower anchors are larger,and the strains of middle anchors are about two times as much as the value of top anchor.When the peak acceleration increases,the strains of top anchors gradually increase,and the middle andupper anchors bear loads mainly.When the peak acceleration reaches to the rupture limit,the maximum dynamic strains of anchors increase sharply,and the changing amplitudes of strains of middle anchors are greatest,a clear gap shows between the sliding body and the sliding bed,and the anchors are pulled out.Obviously,the traditional design idea＂strengthening slope waist and reinforcing slope toe＂is suitable for the areas of low seismic fortification intensity,and the top and middle anchors should be lengthened properly in the areas of high seismic fortification intensity.