OCR Text |
Show 3 cone assembly is held up by the clamp. The operator looks through the observation window, loosens the clamp, and gently lowers the cone assembly until it makes contact with the snow. The operator holds the cone assembly in this position and notes the meter stick reading, designated Z to symbolize reference position. The cone assembly is then lifted to an initial Z, reading on the meter stick, released and allowed to fall and penetrate the snow. The cone assembly comes to rest at a meter stick position recorded as Z2. The cone assembly is then lifted and clamped in the up position, the aluminum frame is picked up and reset in a level position over a new sampling area, and the sequence is repeated. If the weight of the cone assembly is w, the impact energy is given by: U = w( Z2 - Z,) and the penetration is: Z = Z2 - zr Minimum input energy is obtained when Z, = zr U can be increased by decreasing Z] ( i. e. raising the cone assembly since the meter stick is oriented with the 0 marking above the 1 meter marking) until the cone touches the cross bracket. For further increases in U it is necessary to add weights to the cone assembly. Previous drop cone penetrometer models measured the diameter of the cone impression. This was a time- consuming operation and restricted the experimenters to two or three drops per determination of U. Using the construction and procedure described above enables the operator to quickly make 5 to 10 drops for each determination. |