不同降雨工况下锚杆锚固提升风化凝灰岩高陡边坡稳定性研究

Research on improving stability of high and steep slopes of weathering tuff by anchor rod anchorage under different rainfall conditions

凝灰岩质地松散,抗剪强度和抗风化能力低,使得凝灰岩高陡边坡易发生局部崩塌甚至失稳产生滑坡。为探究不同降雨强度对平朔某露天矿运输公路旁凝灰岩高陡边坡的稳定性的影响,采用GeoStudio数值分析软件,选择3种降雨强度,对比计算了边坡在采用锚杆锚固前后的稳定性和孔隙水压的变化。结果显示,边坡在中雨工况下,岩土体内部的孔隙水压随降雨时长的增加而降低;在大雨和暴雨持续降雨5 h后,边坡岩土体孔隙水压达到稳定状态,岩土体内部受到雨水下渗与孔隙内部气体的释放达到平衡状态,而在中风化和强风化凝灰岩交界处,水流量较大,这是由于两层岩土体的渗透性差异导致的渗透雨水产生优先渗流引起的,很可能在此交界处发生边坡滑移破坏。经过锚杆锚固后边坡有效滑弧面积缩小,粉砂堆积层和深部凝灰岩基岩滑弧安全系数较高,说明锚杆起到了较好的锚固作用。数值模拟主要了考虑降雨对边坡的影响,可为类似结构的岩土体边坡工程提供借鉴。

The texture of tuff is loose,with low shear strength and weathering resistance,making high and steep slopes of tuff prone to local collapse and even instability,resulting in landslides.To investigate the effect of different rainfall intensities on the stability of high and steep slopes of tuff next to the transportation road of an open-pit mine in Pingshuo,three rainfall intensities were selected and the stability and changes in pore water pressure of the tuff slope before and after anchor rod anchoring were compared and calculated,utilizing the GeoStudio numerical analysis software.The results showed that under moderate rainfall conditions,the pore water pressure inside the rock and soil mass decreased with the increase of rainfall time.After 5 hours of heavy rainfall and continuous heavy rainfall,the pore water pressure of rock and soil mass on the slope reached a stable state,and the rock and soil mass was balanced by rainwater infiltration and the release of gas inside the pores.However,at the junction of moderately weathering tuff and strongly weathering tuff,the water flow was relatively large,this was due to the difference in permeability between the two layers of rock and soil mass,resulting in preferential seepage of rainwater,which means that slope sliding damage is likely to occur at this junction.After anchoring,the effective sliding arc area of the slope decreased,and the sliding arc safety coefficients of the silty sand layer and deep tuff bedrock increased,indicating that the anchors played a better anchoring role.This numerical simulation mainly considers the impact of rainfall on slopes,which can provide reference for similar structures of rock and soil mass slope engineering.