If you enter enough test readings for the current loading increment CONS displays a chart of dial readings vs. log10(time) or vs. √time in the lower left section of the screen. In this panel you can select whether the current chart (log10(time) or √time) is included in the final chart reports by checking the corresponding chart's Report box, or leave both log10(time) and √time box unchecked if you find that the loading increment's readings are not amenable to plotting a reasonable time-rate curve.
Both log10(time) and √time charts also have construction lines used to calculate Cv; while these lines are automatically placed by the program as you enter your time-rate data, they are user-adjustable.
- Please treat the program's construction line placement as an initial guess. Each line's placement should be carefully reviewed before printing your final reports.
You can toggle between the log10(time) and √time charts by clicking on the and buttons. Unlike in previous versions of the software, toggling between the charts does not reset any construction line adjustments you may have made. It also does not affect whether the chart is plotted on the final reports -- the Report check box displayed to the right of each chart selects whether the chart gets plotted on the time-rate chart reports.
Log(time) Construction Adjustment
To calculate Cv from a log10(time) plot a line must be placed tangent to the steepest portion of the time-rate curve (called the primary construction line), and a second line is placed through the final readings that represent a straight-line trend (called the secondary construction line). The intersection of these two lines represents D100
CONS estimates the initial placement of these lines based upon the mathematical model used to plot the curve. You can adjust this placement by dragging the line endpoints with your mouse, while holding the left mouse button down.
The D0 calculation requires an additional construction consisting of two vertical lines labeled t0 and 4t0. These lines represent a time ratio of 1 to 4 on the curve: D0 is taken as the dial reading at time "t" minus the difference between the dial readings at "4t" and "t". Again, the location of the construction can be adjusted by dragging the t0 line with your mouse while holding the left mouse button down.
- The time interval construction will only appear if the D0 is selection is
Construction. If you select
Initial dial, CONS will use the actual dial reading at time=0 as D0 instead of using a construction line to estimate the D0 value.
- Additionally, this construction will not be shown (and the D0 is selection will be set to
Initial dial) if the software cannot determine a placement for the t0 and 4t0 lines that satisfies two requirements (per ASTM D2435):
- t0 must be placed between 25 and 50% of the total loading increment deformation.
- 4t0 must be located at less than 50% of the total loading increment deformation.
Square-Root(time) Construction Adjustment
Calculation of Cv from a √time chart requires placement of a line tangent to the steepest portion of the time-rate curve, then a second line starting at the same left endpoint as the first but with a slope of 1.15 times the first. Finally a third, vertical, construction line is initially placed at the intersection of the second line with the curve. This line indicates the curve's T90 point.
All three lines can be adjusted by dragging on their endpoints with the mouse while holding down the left mouse button.
- The Cv percentage box causes the program to calculate Cv at a different percentage of primary consolidation than the default value of 90%.