Installation of Prefabricated Vertical Drain

BAEK JAE PVD works are done vertically to depths exceeding 200 feet (65 meters). The water under pressure in excess of hydro-static, flows through the filter fabric of the drain and into the channels of the drain core where it can flow vertically out of the soil. This flow may be either up or down to intersect natural sand layers or to the surface where a sand drainage blanket or prefabricated strip drains are provided. The water in the soil only needs to travel to the nearest drain to reach a free drainage path. The drains are usually placed in a triangular configuration of 3 to 12 feet (1 to 4 meters) – depending on the desired consolidation time. As a result, the consolidation process can be reduced from decades to six months or less and the stability is increased, meaning that embankment construction can take place more quickly.

Prefabricated Vertical Drain Work Process

01

01

With surcharge preloading, ground settlement time will be greatly reduced as PVD installation reduce the water distance movement.
02

02

Preloading is usually accomplished by placing surcharge fills to accelerate consolidation, PVD are often used with preloading
03

03

Ground settlement difference with and without PVD installation

Detailed Procedure of Installation of PVD

  1. Marking of locations to be installed with PVD in accordance with the construction drawing. The PVD shall be installed in form of square net and placed by the distance of design drawing and designed depth from the surface of sand mat layer as specified.
  2. Setting PVD driving machine at right location in accordance with the designed layout.
  3. PVD shall be installed to the mandrel, operating the lead of the mandrel to the location of PVD to be installed.
  4. Attach anchor plate to the end of PVD with the fold up of PVD and fastened by steel pin.
  5. Insert the mandrel with PVD to the designed depth. When PVD is already installed, the mandrel is pulled up (concurrently the anchoring end shall keep PVD in the ground). When the mandrel is completely pulled up, PVD shall be cute by scissors leaving 30cm over the top of sand mat. The process of installing PVD shall be started in a sequential manner to the subsequent locations.
  6. Overlap joint of PVD is at least 30cm and fastened.
  7. The Contractor shall correctly record each installation, quantity of PVD, coordinate of grid and length of PVD.
  8. After the installation has been completed, the Engineer shall be invited to check and subsequent items shall only be carried out after getting the approval from the Engineer for the above work.
  9. All other requirements for installation of PVD shall be observed by the Contractor in accordance with the specifications.
  10. Remove or replace PVD improperly installed or damaged as directed by the Engineer.
  11. After installation 30cm of PVD above surface of sand mat will be folded into the sand mat by workers.

Main-Con Engineers to Witness Testing Works

Main-Con Engineers to Witness Panel Issues

Work will be recorded into Advanced Data Logger System