Long-term effective stress state refers to the state of all the excess pore water pressure dissipation in the soil, that is, the state of the state.
Non-cohesive soils are freely drained, so the excess pore water pressure generated during construction is quickly dissipated, so there is effective stress in the short and long term so that ¢ is common.
There are exceptions, such as the presence of fine silt fine particles can greatly shorten the time. The change of the pore (the state of stress) Water pressure may lead to the change of the strength of the cohesive soil. The balance of the negative pore water pressure in the soil makes the cohesion of the soil decrease and the internal friction angle F increases.
For fine silt, normal consolidated soil and underconsolidated clay, ie cohesive soil less than 40kPa cohesive soil change, the effective stress state generally does not play a decisive role, because the effective parameters of the change to improve the soil strength. In the case of Overconsolidated clays, ie soils with undrained cohesion of more than 40 kP, the opposite is true. Z-shaped steel sheet piles in most cases from the total stress state to the effective stress state, because the soil friction angle increment does not completely compensate for The loss of cohesion will lead to soil strength reduction. Therefore, steel sheet pile
the analysis of cohesive soils suggest the use of long and short-term analysis of multi-phase approach.