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Mapping Geomorphological Environments Phần 2

Tham khảo tài liệu 'mapping geomorphological environments phần 2', khoa học tự nhiên, công nghệ môi trường phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Methodology-Techniques Solid Core Recovery is called the total length of categories 1 and 2 and is expressed as sampling length percentage. Rock Quality Designation RQD total core length 10cm sampling length x 100. There are various measures that can be taken during sampling in order to decrease core loss when the latter is due to one of the following reasons Drilling post vibrations. This can be avoided by preserving the drill in good mechanical state by decreasing the spindle s propulsion and rotation velocities and by using drilling rods of the same diameter along the full length of the drilling column. Excessive drilling velocity. This can be avoided by decreasing drilling and rotation velocities. Sample destruction because of large water circulation. This can be avoided by implementing dry boring in selected depths by changing the circulating drilling pulp or fluid and by using compressed air instead of water. Sample pulverisation. This can be avoided by increasing water supply by slightly elevating the drilling column or and lifting it to the surface to unblock it. The term rock fragment sampling describes the systematic collection of rock decay products that are lifted to the surface with the drilling pulp or fluid that circulates while drilling. With rock fragment sampling The drilling diameter remains stable independently of the rock s hardness There is no drilling wall collapse Transport of rock fragments from drilling bottom is complete with no water loss. Rock fragments are collected on the surface washed with water dried packed and sent to the laboratory for further analysis C. Sampling with physical support It refers to sampling in natural sections of soil materials and loose depositions by hand. It also refers to sampling with drills moved by hand Auger type . The first task concerns detection and accurate determination of sampling location with GPS support in order for location redetermination and sampling repetition to be possible if required. The