Ground Improvement Drainage and Soil Stabilization

Ground improvement PVDs (photovoltaic dispersible devices) are an effective way to improve the drainage capacity of any site. They are typically installed by inserting a hollow steel mandrel, which is accompanied by an anchor plate. The anchor plate keeps the drain firmly in place when it is removed. The steel mandrel is also removed after installation, which disturbs the soil surrounding the drain and reduces its hydraulic conductivity.

During the monitoring and design phase, maximum settlements were between 200 mm and 415 mm. One-dimensional consolidation theory was used to estimate settlements for 60700 m2 of loaded area overlying a layer of three to seven m of compressible soil. After thirty-to-fifty days of preloading, settlements had reached approximately 80 percent of the total area. The time required for complete consolidation was approximately 48 days when the PVDs were installed at 1.0 m centre-to-centre spacing.

One of the most important considerations when installing PVDs is to ensure that the installation process is fast and efficient. Depending on the terrain and type of soil, PVDs may be the best choice. They can help in improving soft ground conditions as well as reducing lateral displacements in coastal areas. PVDs can be used as an alternative to traditional filling. The initial cost of PVD installation is less than $1000 per square m.

Prefabricated vertical drains are also known as wick drains. They are plastic strips encased in geotextile. The prefabricated vertical drains are commonly used in conjunction with surcharging, which is a method to pre-load soft soils to increase pore water pressures and allow them to drain away. Surcharging reduces the preloading time and speeds up the primary settlement process. In addition, they improve soil tensile strength and reduce the occurrence of settlement and liquefaction.