千枚岩隧道破碎带TSP超前预报解译标志

Study of seismic wave reflection characteristics of unfavorable geological bodies in phyllite tunnel

千枚岩等软岩隧道施工中易出现垮塌等地质灾害。以典型千枚岩隧道——汶马高速公路鹧鸪山隧道为例,以地震波传播理论为依据,结合工程地质分析及地震波正演模拟,探讨TSP预报中针对千枚岩构造破碎带在不同含水率状况下的地震波反射特性及解译标志,结果表明:纵波及横波遇千枚岩构造破碎带反射现象明显,横波较纵波反射更强烈;破碎带富水时,千枚岩泥化变软,纵波反射加强;从深度偏移角度分析,破碎带内正负反射频繁变化,单个反射层延伸性差。研究结果可以提高TSP在软岩隧道中的预报准确性。

Collapse and other geological disasters often occur in the process of tunnel construction in soft rock like phyllite.Accurate prediction of geologic bodies in front of tunnel face is particularly important.Taking the typical phyllite tunnel,the Zegu mountain tunnel in Wenchuan-Maerkang Highway of Sichuan as example,on the basis of seismic wave propagation theory,combined with engineering geological analysis and forward modeling,the reflectivity and interpretation signs of seismic waves under different water conditions for phyllite fracture zone in the TSP prediction are discussed.It shows that reflection phenomenon is obvious when longitudinal wave and transverse wave meet fracture zone and transverse wave reflection phenomenon is more intense than the longitudinal wave.When fracture zone is rich in water,phyllite becomes softer and transverse wave reflection intensified.Analysis of the perspective of depth migration reveals that normal reflection and negative reflection shift frequently and the extensibility of single reflecting layer are poor.The result of this research improves the accuracy of TSP prediction in the construction of soft rock tunnel.