Introduction
In consolidation test of soil parameters of a sample, the settlement caused by applying an increased load to a soil sample is measured. These measurements involve the amount of soil that will decompress or compress on an application of a load.
Materials
Sieve nest
Sieve brushes
Tamper
Consolidation device
Displacement indicator
Caliper
Drying oven
Moisture
Procedure
A soil sample of size finer than # 40 sieve is selected to be used in the experiment. The soil moisture content of the is first determined using a representative quantity and the mass of the remaining sample (Wd) which will be placed in the consolidated device is measured. The soil is then remolded into the apparatus but ensuring at least 0.8 inches tall but less than 1.0 inches tall. The large porous disc is then placed below the mold in the simple carriage. The sample soil is placed within the mold and then tampered to gentle compact soil using a tamper. During tampering, the weight of the tamper is allowed to compact the soil gently, and no additional force is applied to the sample. The initial height of the soil sample is determined and labeled as (H1). The diameter of the cell is sample is also measured to allow the determination of the area (A) and the initial volume (Vi). This is followed by placing the small porous disc on top of the soil sample with the groove facing up. The brass loading head is placed on the small porous stone, and the loading yoke screw is centered onto the loading head gently followed by adjustment until the loading arm is level is when the loading yoke is secured in position. The soil sample is then saturated by adding water to the carriage and allowed for the air to bubble until it ceases. The dial indicator is then moved in a position to allow displacements in both directions, and the indicator is zeroed. The loading arm is added a 1 kg mass and allowed for pre-consolidation for about five minutes. After the first pre-consolidation, another load of 4kg is added for 20 minutes, 8kg for 20 minutes, and 16 kg for 20 minutes. The new load application is known as new stage loading. The weigh is not supposed to be removed between the stages. The time deformation readings are recorded in Table 1 below (Kaniraj and Yee, 73)
Results
The following parameters in a table were obtained from the experiment.
The following equations were used in the calculation of the parameters in the subsequent tables.
Volume of solid Vs
df = change in for the stage loading
ΔH = Total change in height of the sample.
(Kaniraj and Yee, 74)
Discussion
In each of the graphs, the height of deformation increases with the increase in the log time and the square root time. However, as the mass increases it, reaches a point where a maximum height is reached, and the variable also begins to decline. This is also similar to the case of the stress-strain curve.
Coefficient of consolidation
At 4kg load
Cv= TH2D50t
T = 0.197, t = 1.2 (reading 0.312 of the graph)
HD50 = 0.312
Cv= 0.197 x 0.31221.2
= 0.01598
The other values of the coefficient of consolidation for the different masses were also established as shown above (Yan and Yu, 33)
Errors and Remedies
Some errors must have been experienced through non-uniform compaction due the variation of the applied force. Measuring instruments could also lead to errors and inconsistency. These errors could be corrected through the use of more accurate tools and maintaining all the parameters like input force in the experiment. Several trials of the same experiment could also yield values that have little variation. Despite a few mistakes and errors, the graphs obtained gives a clue of what the experiment was about, and hence the experiment achieved its objectives.
Conclusion
The experiment involves the determination of the consolidation of the soils sample through molding and a gentle amount of force through tampering. The resulting height after tampering is noted and different masses of soil; 8 and 16 kg were also used. Some graphs were plotted, and it was noted that the height of compaction increases with the square root of the time. It reaches a certain point when the parameters decline in the 8kg sample. Similarly, the strain increases with increase in stress until the yield point is reached when the graph begin to decline. Generally, the expectations of the experiment were met.
Work Cited
Yan, Liang, and Xiang Yu. "Microstructure Analysis of Soil Consolidation Material". AMR 557-559 (2012): 900-903. Web.
Kaniraj, Shenbaga R., and J. H. S. Yee. "Electro-Osmotic Consolidation Experiments On an Organic Soil". Geotechnical and Geological Engineering 29.4 (2011): 505-518. Web.
Appendix
Readings
USACE EM _1110-1906 Appendix VIII [3]
ASTM D2435/ D2435 M-11 [19]
Graphs
Equations Used
Vs=WdGsρw 1
Where,
Wd = Dry mass of the soil
Gs = specific gravity of solids
ρw = density of water
The effect height (height of the solids) is calculated using equation 2 below
He= VsA 2 (Yan and Yu, 30)
The void ratio is given by;
en=Hn-HeHe 3
Where,
en = void ratio at the nth time interval
Hn = Height at the nth time interval.
ΔHd50 = Change in height at d50
H50 = height at 50 % deformation stage.
The coefficient of consolidation Cv can be evaluated using the equation 4 below
Cv= TH2D50t 4
Where,
T = 0.197 when using the log time plot or 0.848 when using the square root of time plot
HD50 = half of the specimen height for a double drained device
t=time for consolidation t50 for log time plot and t90 for the square root of time plot
