为解决城市地铁盾构穿越不良地质勘探时的范围大、精细化困难等问题，依托惠深城际铁路工程，采用分布式声波光纤传感（distributed acoustic sensor, DAS）技术开展城市地下不良地质体大范围、高精度勘探方法研究。首先，研究背景噪声扩展空间自相关（extended spatial auto correlation, ESPAC）法对地下岩土体信息的反演成像理论方法，通过建立声波光纤动应变与地下剪切波速度场的关联性反演地下岩土体信息及赋存溶洞的位置与规模；然后，结合现场钻孔勘探与电磁波扫描获取的岩土体信息进行系统的对比验证。研究表明： DAS-ESPAC法清晰反演了地下40 m深范围内剪切波速场的分布特征，基于剪切波速场分布进一步反演了地下岩土体分层、类型、规模及空间分布，探明了粉质黏土与灰岩的分界界面，对于溶洞规模与分布反演误差达到1 m级，相关的勘探信息与钻探详勘数据、补勘数据、地球物理勘探数据吻合较好。
To achieve largescale and high-precision geological
exploration for urban metro shield construction, a case study is conducted on
the Huizhou-Shenzhen intercity railway project using
distributed acoustic sensor (DAS) technology. The authors explore methods for
large-scale and detailed investigations of urban
underground bad geological bodies. First, the extended spatial autocorrelation
(ESPAC) method is applied to invert the properties of underground rock and soil
masses. By establishing a correlation between the dynamic strain measured by
acoustic fibers and the underground shear velocity field, information about
underground rock and soil properties, as well as the location and size of karst
caves are retrieved. The results are then systematically compared and verified
using data obtained from drilling and electromagnetic wave scanning. The
research findings indicate the following: The DAS-ESPAC
method effectively maps the shear wave velocity field up to a depth of 40 m. It
accurately identifies the stratification, type, size, and spatial distribution
of underground rock and soil masses based on the shear wave velocity
distribution. In addition, it verifies the boundary interface between silty
clay and limestone. The method achieves an inversion error for karst cave size
and distribution within 1 m. The exploration results align well with detailed
drilling data, supplementary exploration data, and geophysical exploration
data.
