Determination of the limiting strength of soil under the tips of sunken shafts

Conclusions

1. Berezantsev's approximate solution is not recommended for determination of the limiting strength of the soil beneath the tips of sunken shafts, since the results of computations may be 30–40% on the high side in individual cases.

2. Vyrvo's solution obtained without consideration of the specific gravity of the soil produces good convergence only for determination of the limiting drag of the soil against shaft casings where the height of the soil core is no less than 0.5D and 2 m; values of pli are found to be on the high side by 16–45% in the remaining cases.

3. The limiting pressure of the tip against the soil for circular sunken shafts of any size can be determined using the solution of the plane problem of limiting equilibrium with the introduction of a correction factor that takes into account the axisymmetric stressed state of the soil. Errors do not exceed 4–5% in this case.

4. For a ratio n≥20, the results of solution of the axisymmetric and plane problems are in virtual agreement.