台阶式锯切开挖边坡岩体质量及稳定性评价

Assessment on rock mass quality and stability of step-cutting slope

锯切法进行边坡开挖施工,开挖面平整光滑,对边坡岩体质量影响较小,利于提高边坡的开挖稳定性。目前采用锯切法开挖边坡的应用较少,缺少对切割岩体质量和应力应变特征的详细研究。本文对某抽水蓄能电站台阶式锯切开挖边坡进行研究,通过现场岩石回弹试验和波速测试,对切割开挖边坡的岩体质量进行研究,分析了切割开挖过程中岩体的应变特征。在此基础上,利用三维有限元模型,对锯切法开挖边坡的应力应变情况和稳定性特征进行了模拟。结果表明:台阶式锯切开挖对边坡的扰动较小,岩体质量几乎不受切割开挖影响;边坡开挖过程中的稳定性系数均大于3,边坡整体变形量较小,边坡稳定性较好;在开挖台阶上部会产生较大拉应力,容易引起局部拉裂或崩塌破坏,需要进行及时支护,边坡的锚杆支护深度建议在4.0m以上。

When the slope is excavated by saw cutting method,the excavation surface is smooth.The method has little influence on the quality of rock mass and is conducive to improving the stability of slope excavation.At present,there is few application of saw cutting in slope excavation,and the study on the quality and stress-strain characteristics of the cutting rock mass is lack.In this paper,the step-cutting slope of a pumped storage power station is studied.Through the on-site rock rebound test and wave velocity test,the rock mass quality of the cutting and excavation slope is studied,the strain characteristics of the rock mass during the process of cutting and excavation slope is analyzed.On this basis,a three-dimensional finite element model is used to simulate the stress-strain and stability characteristics of the cutting slope.The results show that the step-cutting method has little disturbance to the slope,and the rock mass quality is hardly affected by the cutting and excavation;the stability coefficients during the slope excavation process are all greater than 3,and the overall deformation of the slope is small,so the slope is stable;a larger tensile stress will be generated on the upper part of the excavation step,which is easy to cause local tensile cracking or collapse.Timely support is necessary,and the rock bolt support depth of the slope is recommended to be above 4.0m.