Badania nad wstępną konsolidacją podłoża zwałowiska zewnętrznego przy zastosowaniu drenów piaskowych
Abstract
STUDIES ON PRELIMINARY CONSOLIDATION OF OUTER HEAP SUBSTRATUM WITH THE USE OF SAND DRAINS
Summary
The paper presents conditions of the increase of pore pressure (u) on the dump sUbgrade of an open-cast mine. On the basis of field measurements it was estimated that the critical value of the pore pressure (u) under given conditions is 0.17-0.20 MN/m2. It was found that in order to reduce so high pore pressure by 50% it is necessary to make drain network with 7 X 7 m or 12 X 12 m spacing, which would work for a least 160-170 days. If the pore pressure is not dispersed, then - according to calculations - the values of shear stress caused by the dump (τxzp) will be almost equal the value of effective shear strength (τ') of the subsoil. It means that the value of stress in the substratum will reach its limit state. The results of field studies and theoretical calculations explain causes of the strong deformations of the subgrade which took place when the subsoil was consolidated in uncontrolled way.
Summary
The paper presents conditions of the increase of pore pressure (u) on the dump sUbgrade of an open-cast mine. On the basis of field measurements it was estimated that the critical value of the pore pressure (u) under given conditions is 0.17-0.20 MN/m2. It was found that in order to reduce so high pore pressure by 50% it is necessary to make drain network with 7 X 7 m or 12 X 12 m spacing, which would work for a least 160-170 days. If the pore pressure is not dispersed, then - according to calculations - the values of shear stress caused by the dump (τxzp) will be almost equal the value of effective shear strength (τ') of the subsoil. It means that the value of stress in the substratum will reach its limit state. The results of field studies and theoretical calculations explain causes of the strong deformations of the subgrade which took place when the subsoil was consolidated in uncontrolled way.