地微动勘探技术在孤石探测中应用——以福州地铁1号线工程为例

Application of Array Micro-tremor Survey for Investigating Weathered Boulder——A Case Study on Fuzhou Metro Line No.1

福州地铁1号线沿线普遍分布有影响盾构掘进孤石。为确保该盾构隧道施工顺利,采用地微动勘探技术对该区间隧道施工范围内的孤石进行探查。对微动台阵采集的数据,采用高分辨率频率波数域(HRFK)法提取瑞雷波频散曲线,并计算视S波速度。获得的视S波速度剖面能直观反映探查范围内的速度变化,剖面上的异常高速体对应着孤石或基岩凸起。在视S波速度判据基础上辅以H/V谱比判据,可有效提高孤石判别准确度。工程实践表明,对地微动探测结果与钻探验证进行对比分析,将探测区划分为盾构施工危险区、警示区和安全区,可很好地指导地铁盾构施工。

Along the first line of Fuzhou Metro,there are a lot of weathered boulders which will obstruct the advance of shield machine.In order to complete the shield construction successfully,the array micro-tremor technology,as a primary survey method,is adopted to find out the boulders within the area of tunnel.The high-resolution frequency-wave number spectrum arithmetic is used to process the acquired micro-tremor data for drawing out Rayleigh wave dispersion curve.And then,a velocity map which can exhibit the changes of apparent S wave velocity in the investigated region,is gained.The abnormally high velocity area may indicate that there is a boulder or protuberant rock in the map.It is more accurately to find out boulder using the H/V spectral ratio rules on the base of apparent S wave velocity map.The engineering practice shows that the survey area is divided into the dangerous,the cautious and the safe zone can conduct well the shield construction according to the results of micro-tremor survey and validations of drilling.