Over-consolidation pressure (OCR) is the pressure exerted on clay soil due to past loading and subsequent unloading. This results in a decrease in the volume of the soil, causing it to become more compact and dense. This pressure can have significant effects on the behavior of the soil and any structures built on it.
Negative skin friction is a phenomenon that occurs when a structure, such as a building or bridge, is built on clay soil. As the structure's weight compresses the soil, it causes a decrease in volume and an increase in pore water pressure. This results in a downward drag force on the structure, known as negative skin friction, which can cause settlement and potential structural damage.
Over-consolidation pressure can significantly affect negative skin friction by increasing the compressibility of the clay soil. This can result in larger settlements and higher drag forces on structures, potentially leading to structural damage. It is important to consider both over-consolidation pressure and negative skin friction when designing structures on clay soil.
The factors that influence over-consolidation pressure and negative skin friction include the type and properties of the clay soil, the magnitude and duration of past loading, and the current loading conditions. Other factors such as groundwater levels and construction methods can also play a role in these phenomena.
There are various methods for mitigating the effects of over-consolidation pressure and negative skin friction, including preloading and surcharging the soil, using geosynthetic materials to reduce the drag force, and improving the drainage and consolidation properties of the soil. It is important to assess the specific site conditions and choose the most appropriate mitigation measures for each case.