We're glad you asked! You may have noticed wood stakes with orange markings or drilling rigs in areas along the US 290 existing right of way and wondered why are they there? Great question! The wooden stakes are used for many purposes, for example, marking existing right of way and the location of utilities. Drilling rigs are used to collect soil samples as part of TxDOT's geotechnical investigation process.
Why are soil samples taken?
Geotechnical investigations are an integral part of the engineering design process for the construction of a bridge or highway. During the design process, it is important to understand the soil characteristics of the site where the facility will be built. The soil from a site is "sampled" (meaning soil samples are taken by drilling a hole in the ground). The soil is studied to obtain information on the physical properties of the soil, to better design foundations for proposed structures. Soil samples are used to provide design information for bridges and retaining walls, and are often drilled to depths up to 80' below ground.
How are soil samples collected?
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After a general site survey is performed, stakes are placed to identify all areas to be sampled. This photo shows equipment trucks (drilling rigs) on site for a day of soil sampling. |
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The operator controls the drilling rig pipes from mechanical equipment as they are lowered into the ground. Other workers connect and disconnect pull cables to change pipes for each depth. Workers carefully drive pipes into the ground to obtain samples. |
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As the cylinder pipe is lifted out of the hole, slurry (a water insoluble mixture) is backfilled into the hole. |
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The slurry is cleaned from the pipe as the sample is removed. |
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The sample is cut into approximately one foot sections. Each section receives a sample number and description for further use when sent for evaluation at the lab. A pocket penetrometer is used to collect readings from the soil sample cylinder. |
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A drilling report is used to record information about the samples collected. |
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After the information is recorded, samples are wrapped with aluminum foil, placed into a plastic bag (to preserve the moisture and air characteristics of the soil), and labeled. The final product is now ready for the lab! At the lab, a wide variety of tests can be performed to measure a variety of soil properties. The results of the tests are provided to the engineer for use in the design. |
Please continue to visit the my290.com website as we provide updated information on the progress of the US 290 Corridor Project.