Crosshole Mapping of a Subsurface Void

Publication Abstract:

Kentucky River Lock and Dam 8, Jessamine and Garrard Counties, Kentucky, was constructed in 1900 and has for the past 120 years experienced significant degradation due to karst geology.  The cement capped wood-cribbed dam is anchored to the Grier Limestone, a karst-forming limestone.  Due to the dissolution of limestone, water seepage around and under the dam has created unstable conditions for the dam that required engineering rehabilitation many times over the years.  A recent rehabilitation project to prevent river water from seeping under the dam included installing engineered secant grout curtains anchored into the Grier Limestone.

During the course of the intrusive investigation a void was encountered in a boring within the proposed secant grout curtain.  Six crosshole tomographic profiles between 4 cased borings imaged several areas of interest.  These areas of interest displayed lower p-wave velocities in contrast to the surrounding material within the survey area.  These low velocity zones are interpreted to be water- or mud-filled voids or vuggy zones within the limestone.

Read full text:

Crosshole Mapping of a Subsurface Void