目前采用地质雷达等无损检测技术可快速、准确检测衬砌厚度和衬砌中钢筋数量等参数，并可有效判识衬砌背后空洞等缺陷沿隧道纵向和环向长度，但对这类缺陷的径向尺度因介电常数的差异、反射面的识别等原因而无法准确判识。依托西南地区某运营铁路隧道衬砌背后存在较大空洞的工程实际，结合现场钻孔调查和地质雷达无损检测，首次运用钻孔三维激光扫描技术对运营铁路隧道衬砌背后空洞进行扫描，实现精确检测，得到衬砌背后空洞的三维形态和具体尺寸，检测成果可为隧道病害整治提供准确的数据，可设计出更具针对性和操作性的整治方案。提出的“物探+钻孔三维激光扫描”技术，能实现衬砌背后空洞“粗中有细”的全面检测。

The parameters, i.e. lining thickness and reinforced rebar of lining, and the longitudinal and circumferential length of hollow behind lining can be detected rapidly and accurately by nondestructive ground penetrating radar detection technology nowadays. However, the radial dimension of the hollow behind lining can not be clearly identified due to the difference of dielectric constant and recognition of reflecting surface. The technology of threedimensional laser scanning in borehole is adopted to detect the hollow behind lining of an operating railway tunnel in Southwest China for the first time. The threedimensional shape and sizes of the hollow are obtained based on borehole drilling method and ground penetrating radar. The detection results can provide accurate data for tunnel disease treatment and reference for pertinent and feasible tunnel disease treating schemes. The technology of geophysical prospecting+threedimensional laser scanning in borehole can detect the hollows behind tunnel lining accurately.