| Description |
ix, 65 leaves : illustrations, maps ; 28 cm |
| Summary |
"A structural support was needed to strengthen the load-bearing capacity of an unnamed bridge foundation in Laclede County in South-Central Missouri due to increasing traffic volume and age of the bridge. This area is characterized by karstic features such as losing streams, underground caves and sinkholes. During the construction of a drilled shaft for the substructure, a few feet north of the north footing of the pier, voids were noted beneath a roughly 2 foot thick cap of dolomite rock. Because of this, there were concerns about the integrity of the rock beneath the existing bridge foundation. Consequently, subsurface investigation was conducted at the site using borings. Results from the borings confirmed the presence of voids adjacent to or at the foundation bearing level of the northern and central pier footings. This information alone provides accurate data only at the sampling location, so control elsewhere has to be interpolated, which can result in erroneous interpretation. To map the lateral and vertical extent of the voids, electrical resistivity tomography (ERT) was employed using the SuperSting R8/IP Earth resistivity meter. The result obtained was used to complement the borehole information. Dipole-dipole electrode configuration was used. Based on the interpretation of the results of the ERT survey and borehole control, it was concluded that the bedrock in the area was mainly dolomite dipping from east to west, and appears to be competent bedrock. Voids encountered were not of room-sizes as to breach the integrity of the bridge foundation. Compaction grouting was the engineering solution employed to fill the voids and stabilize the ground around the structure"--Abstract, leaf iii. |
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