In the Field: Railroad Bridge Replacement Drilling
October 1, 2012
Gregg Drilling recently completed a project requiring a CPT and drilling investigation for railroad bridge replacements.
The project presented unique access challenges, but Gregg was able to maneuver the equipment into place on the railroad using self-propelled low-railers (see photo 1). This allowed a 25-ton cone truck, a limited-access hollow-stem auger rig, and a mud-rotary drill rig to move easily on the railroad lines to the exact locations for drilling and testing.
Holes were cut through the low-railers to allow for the cone and drilling equipment to pass directly through (see photo 2). Initially, the drill rigs were used to set casing through the gravels of the rail line so that the cone could be pushed to characterize the soil. In total, 25 CPT locations were tested to a maximum depth of 120 feet. A few borings also were conducted with the mud rotary drill rig to collect samples and verify the soil conditions. The main concern was discovering the depth of bedrock so that bridge piles could be designed to the correct length.
Gravels were encountered while drilling, causing a loss of drilling-fluid circulation. Gregg’s knowledgeable operators quickly installed casing, and were able to complete the sampling to bedrock.