锚杆和锚索是工程边坡治理和地下工程开挖过程中最常用的支护措施之一。为反映支护结构受力情况,通常会选择一定数量的锚杆和锚索布置监测仪器,国内相关的4个规范对监测锚杆锚索布置数量和比例要求有一定差异。选取10座有代表性的大型水利水电工程进行监测布置研究,通过数理统计计算分析,提出监测仪器布置数量的合理建议。研究表明:锚杆锚索监测成果的代表性与所抽取的样本数关系密切,与总样本数及抽样比例无直接关系;被监测体样本的不均一性对抽样代表性影响显著;当抽样数<10时,随着抽样数的增加,抽样误差显著下降,抽样代表性显著增加;当抽样数>50时,抽样代表性增加不明显;考虑到采用大规模锚杆锚索支护时,各区域的地质条件和受力环境存在差异,其监测布置应结合地质条件和工程结构综合考虑,不宜统一规定相应的监测比例。

Anchor bolt and anchor cable are the most commonly used supporting measures in engineering slope treatment and underground engineering excavation. Monitoring instruments are arranged at a certain number of anchor bolts and cables to reflect the stress condition of support. However, the requirements for the number and proportion of anchor rods and cables differ in four relevant specifications in China. We made a research on the monitoring arrangement of ten representative large-scale water conservancy and hydropower projects, and gave reasonable suggestions on the number of monitoring instruments via mathematical statistical calculation and analysis. Our findings suggest that the representativeness of monitoring results of bolt and cable is closely related to the number of samples, but not directly related to the total number of samples and the sampling proportion; the heterogeneity of the monitored samples has a significant impact on the sampling representativeness; when the sampling number is less than 10, the sampling error drops significantly and the sampling representativeness rises significantly with the increase of the sampling number; when the sampling number is greater than 50, the increment of sample representativeness is not obvious. In conclusion, when large-scale anchor bolt and cable support is used, the monitoring should be arranged in line with local geological conditions and engineering structure rather than uniform monitoring proportion.