Laserfiche WebLink
w <br /> v <br /> 2.1.5 Quallty Control <br /> Quality control procedures include calibration of the electric fiction cone, checking for <br /> and remediating probe deficiencies,maximizing the safe achievable penetration depth, and <br /> deterring loss of the piezometric response (if applicable). The following paragraphs <br /> describe these procedures. <br /> Calibration of the electric fiction cone probes is perforated by imparting a series of <br /> known loads on the cone tip, friction sleeve,and pore pressure transducer,and comparing <br /> the known loads with the output signals from the probe. Deviations are corrected by <br /> adjusting the calibration settings of the DAS. The calibration is conducted over the full <br /> range of the probe's output, but particular attention is devoted to the lower end of the <br /> measurement range, where any deviations tend to be more critical. Changes in the <br /> calibration constants of each probe are monitored over time to provide performance <br /> histories,which help determine replacement intervals. <br /> Calibrations spanning the full range of measurements are conducted every 3,000 lineal feet. <br /> - of penetration. Zero-load readings of the cone tip and sleeve friction are recorded <br /> before and after each test, while the probe is suspended vertically in the air. These <br /> readings provide a direct indication of the data quality. Significant non-zero outputs <br /> could result from mechanical factors preventing proper load cell response, as well as <br /> ins-ability or malfunction of the DAS or strain gauges. Previous overloading of the load <br /> cells or severe temperature fluctuations can also cause zero drifts. <br /> The cone tip and friction sleeve diameters are measured daily to monitor the wear due to <br /> soil abrasion. These components are replaced when their dimensions drop below the ASTM <br /> (1986) specified tolerances. The friction sleeve diameter is always larger than that of <br /> the cone tip, so as to avoid artificially low friction sleeve readings. The roughness of <br /> the cone tip and friction sleeve surfaces are also monitored and maintained within ASTM <br /> specifications. The rubber fillers (quad rings) separating the cone tip and friction <br /> sleeve from each other and the stationary parts of the probe (see Figure 2) are checked <br /> before each test, and replaced if necessary, to ensure correct loan transfer from the cone <br /> tip and friction sleeve to the respective load cells. <br /> tiJ <br /> 6 <br /> pp <br />