The soil gas sampling threaded drill is mainly used to drill holes in soil at different depths, providing a channel for inserting gas sampling tubes and collecting soil pore gases (such as methane, carbon dioxide, volatile organic compounds, etc.). Its use should follow the process of "preparation drilling sampling closing", with the following specific steps:
1、 Preparation before use
Equipment inspection and assembly
Check whether the main body of the threaded drill (drill rod, drill bit) is intact, without bending, breakage or thread wear, ensuring that the connecting threads between the drill rods can be tightly engaged to avoid air leakage or disconnection during drilling.
Prepare supporting tools, including sampling tubes (usually made of inert materials such as stainless steel tubes), sealants/gaskets, tape measures (used to measure drilling depth), gloves, goggles (to protect against soil debris), and soil gas samplers (such as vacuum sampling pumps, gas collection bags).
Site selection and safety confirmation
Determine sampling points based on sampling purposes (such as pollution monitoring, ecological research), avoid underground pipelines, areas with dense tree roots, or hard rock layers, and avoid damaging equipment or affecting sampling accuracy.
Wear protective equipment, clean up weeds and gravel on the surface of the sampling point, level the ground, and ensure that the drill rod can enter the soil vertically during drilling.
2、 Drilling operation steps
Initial drilling and drill pipe connection
Hold the top handle of the threaded drill, align the drill bit vertically with the sampling point, rotate the drill rod clockwise, and gradually drill into the soil using the cutting force of the thread.
When a single section of drill pipe is about to fully enter the soil (with only the top connecting end remaining), stop rotating and align the lower thread of the next section of drill pipe with the upper thread of the already entered drill pipe. Tighten clockwise to ensure a secure connection without looseness.
Continue drilling to the target depth
Repeat the steps of "rotary drilling - connecting drill rod", pause for a moment every 10-20cm of drilling, clean the soil attached to the surface of the drill rod, and avoid soil blocking the threads and affecting the drilling efficiency.
Measure the total length of the drill rod that has been buried in the soil in real time with a tape measure until the preset sampling depth (such as 0.5m, 1m, 2m, determined according to research needs) is reached, and stop drilling.
3、 Cooperate with soil gas sampling
Insert the sampling tube and seal it
Slowly rotate the drill rod counterclockwise and gradually pull it out of the soil, leaving a vertical borehole in the soil.
Immediately insert the prefabricated gas sampling tube (the tube body can be perforated to collect pore gas) into the borehole, with the lower end of the sampling tube reaching the target depth and the upper end exposed 5-10cm above the ground.
Fill the gap between the sampling tube and the soil with sealant or gasket to ensure that there is no air leakage around the borehole and to prevent external air from entering and affecting the purity of the sampling.
Start the sampling device to collect gas
Connect the upper end of the sampling tube to a soil gas sampler (such as a vacuum sampling pump) or gas collection bag, start the equipment according to the operating instructions of the sampler, extract soil gas from the borehole, and complete gas collection.
If it is necessary to collect gases at different depths, the process of "drilling insertion sampling tube sampling" can be repeated, and the drilling positions at different depths can be changed to avoid cross contamination of gases caused by repeated use of the same drilling hole.
4、 Closing after use
Equipment cleaning and maintenance
Disassemble and separate the extracted drill rod and drill bit, and rinse the soil residue on the surface with clean water. If the soil adhesion is severe, it can be cleaned with a brush before rinsing to avoid clogging the threads after the soil dries.
Wipe the water off the drill rod and drill bit, check the wear of the threads and drill bit, apply rust proof oil to slightly worn areas, and replace severely damaged components in a timely manner to ensure normal use next time.
On site recovery and data recording
Level the soil at the sampling point, return the cleared weeds and gravel to their original positions, and restore the site environment.
Record the drilling depth, sampling time, soil type (such as loam, clay, sandy soil), and other information of this sampling to provide a basis for subsequent data analysis.