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Cranfield University

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Ancillary Experiments<br />

The study from Lamande et al. (2006) confirming the theory of Söhne (1954) used identi-<br />

cal contact pressures on different plate sizes. Thus the soil was subjected to the same pres-<br />

sure with each plate but with larger plates the total load increased. This resulted in twice<br />

the LPPL for the larger plate compared to the smaller one at the same contact pressure.<br />

Considering the concept of the LPPL, this might explain the larger impact of greater loads<br />

Lamande et al. (2006) observed in the subsoil and actually show that it is neither the con-<br />

tact pressure nor the load determining alone soil deformation and pressure distribution in<br />

the soil. It is a combination of the LPPL and the contact pressure.<br />

The ability to describe the sinkage behavior from the soil bin experiments with the parame-<br />

ter LPPL reasonably well lead to a subsequent step: an investigation of the pattern of data<br />

points from small scale sinkage experiments replicating full size contact patches and plot-<br />

ting sinkage vs. LPPL compared to contact pressure for them. In a first instance this was<br />

investigated by using one plate and varying the applied pressure and measuring its sinkage<br />

and subsequently using different plate shapes scaled from real contact geometry.<br />

7.3.4.1 Variation of plate sinkage with applied load/contact pressure<br />

The response of small scale plates to applied pressure was investigated. A rectangular plate<br />

was laden to different contact pressures and the sinkage recorded. Afterwards the sinkage<br />

was plotted against contact pressure which is shown in Figure 125. A straight line fits the<br />

data exceptionally well and the intercept states that up to a pressure of 31 kPa no sinkage<br />

will take place as the soil is strong enough to carry this load without deformation.<br />

Plotting the data against LPPL (Figure 125, left) does not reveal a different pattern. Conse-<br />

quently in this condition with one plate size it could not be decided which of the two pa-<br />

rameters is able to describe the data more precisely. Due to the fact that the plate shape is<br />

the same, this is expected as with varying load contact pressure and LPPL change propor-<br />

tional to each other.<br />

Ph.D. Thesis Dirk Ansorge (2007)<br />

162

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