Publication Date
5-2020
Abstract
Kentucky River Lock and Dam 8, Jessamine and Garrard Counties, Kentucky, were constructed in 1900 and have for the past 120 years experienced significant degradation due to karst geology. The cement capped wood-cribbed dam is anchored to the karstic Grier 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 intrusive investigation a void was encountered in a boring in Cell 2. A secant grout curtain was proposed to prevent groundwater from migrating through the void. Six crosshole tomographic profiles between 4 cased borings imaged a fracture zone. The fracture zone displayed lower p-wave velocities in contrast to the surrounding material within the survey area. This low velocity zone is interpreted to be water- or mud-filled voids or vuggy zones within the fracture in the limestone.
DOI
https://doi.org/10.5038/9781733375313.1059
Crosshole mapping of a subsurface void
Kentucky River Lock and Dam 8, Jessamine and Garrard Counties, Kentucky, were constructed in 1900 and have for the past 120 years experienced significant degradation due to karst geology. The cement capped wood-cribbed dam is anchored to the karstic Grier 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 intrusive investigation a void was encountered in a boring in Cell 2. A secant grout curtain was proposed to prevent groundwater from migrating through the void. Six crosshole tomographic profiles between 4 cased borings imaged a fracture zone. The fracture zone displayed lower p-wave velocities in contrast to the surrounding material within the survey area. This low velocity zone is interpreted to be water- or mud-filled voids or vuggy zones within the fracture in the limestone.
