문경 가은 석회암지역에서 물리검층법을 이용한 지반평가

초록

Understanding the size, shape, and location of underground cavities should be given priority to effectively predict ground subsidence and evaluate ground stability. We conducted integrated geophysical well loggings in the limestone area and discussed their applications. The geophysical responses of natural gamma and gamma-gamma (density) logs provided information to map the distribution of limestone, limestone cavity, and cavity filled with clays. The cavity leaded to high caliper and low natural gamma radiation and density responses in contrast with limestone and clay. The vertical distribution of seismic velocity and density were described by full waveform sonic and gamma-gamma (density) logs to understand the in situ physical properties, and dynamic elastic modulus was estimated from these physical properties. Moreover, groundwater flow was investigated in order to assess the possible groundwater flow through the cavities. As a result of well logs, many limestone cavities and cavities filled with clays were detected at a shallow depth, and they were concentrated in some areas. The variations of fluid temperature and electrical conductivity enabled us to define the groundwater flow through the limestone cavities or faults.

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