This European standard establishes general principles for the execution,testing,supervision and monitoring of vertical drain projects.
This European standard includes the application of prefabricated vertical drains and sand drains and deals with requirements to be placed on design,drain material and installation methods.This European standard applies to the improvement of low-permeability, highly compressible soils by vertical drainage and preloading.imformation regarding loading(embankment,vacuum or ground water lowering)and preloading is given in informative Annexes A and B.
Vertical drainage is used both in on land and in marine constructions for the following puiposes:
- (pre-)consolidation and reduction of post-construction settlements;
- speeding up the consolidation process by decreasing the path lengths for pore water dissipation;
- increase of stability(by increasing effective stresses in the soil);
- groundwater lowering;
- mitigation of liquefaction effects.
In each case there is an overall treatment of the soil(the volume of the drains is small in relation to the soil volume treated).
This European standard does not include soil improvement by means of wells,gravel and stone columns, large-diameter geotextile enclosed columns or reinforcing elements.
Vertical drainage can also be combined with other foundation or ground improvement methods,e.g.electro-osmosis,piles and compacted sand piles,dynamic compaction and deep mixing.
Guidance on practical aspects of vertical drainage,such as investigation of deain properties, execution procedures and equipment, is given in Annex A.Investigation of soil characteristics and assessment of design parameters,which are affected by drain properties and execution,are presented in Annex B.