AS 8700:2011 pdf – Execution of prefabricated vertical drains.
2.4.5 Discharge capacity and filtration characteristics
The discharge capacity of the round drains is usually much larger than is required for soil consolidation. It may decrease if the round core is crushed due to an increase of lateral effective pressure during the consolidation process and/or buckling.
The perforation of the pipe (core) shall not be sealed due to compression of the filter sleeve. The pipe and filter of drains used for longer term applications shall consider longer term durability aspects (see Clause 2.2).
2.4.6 Filter of round drain
The fitter of round drains shall comply with the requirements of Clause 2.3.6.
2.4.7 Tensile strength per unit sldth of filter
The tensile strength per unit width of filter for round drains shall comply with the requirements of Clause 2.3.7.
2.4.8 Permittivity/pernicability of filter
The permiuivity/pernieability of the filter of round drains shall comply with the requirements of Clause 2.3.8.
2.4.9 Pore size of filter
The pore size of filter for round drains shall comply with the requirements of Clause 2.3.9.
2.4.10 Quality control
The round drain shall comply with this Standard and the applicable conformity assessment procedures.
NOTE: The filter and drain characteristics and corresponding test methods, as well as the testing frequency, are given in Table 2.2. except that the discharge capacity tests (straight and buckled) need not apply.
(ji) Process design Is the second phase，the method of drain installation and its
functioning in practice has to be designed. This phase accounts for effects of draininstallation on the ground, geometry, the nature and the dimensions of the drains andfor effects such as possible buckling in case of excessive strains in some soil layers.
3.2 DESIGN PHILOSOPHY
Vertical drainage may be used for different purposes as outlined in Clause 3.1 ; however, theprocess of designing vertical drainage generally follows the operations listed in Figure 3.1.The objective (design basis) and the ground properties (first row of boxes) interact with thesettlement and stability analyses to satisfy the requirements put on the targeted outcomefrom the effect of the drains; that is to reach a given degree of global and/or localconsolidation within a specific period of time.
Ground treatment by vertical drainage and the associated subsequent preloading shall bedesigned and executed in such a manner that the structure，embankment or paved areasupported by the treated ground, during its intended life and with an appropriate degree ofreliability and cost-effectiveness,will remain fit for the intended use and sustain all actionsand influences that are likely to occur.
The serviceability requirements for the development of the soft soil site shall be specifiedby the client. The observational method,which involves adapting the design in a plannedmanner,is an important part of the design.
The design shall take into account the loads that could occur during construction andservice. It shall account for the known effect of the drain installation on the properties ofthe ground and the effects of the initial and longer term groundwater levels and the impactssuch levels may pose on the preloading design.
AS 8700:2011 pdf – Execution of prefabricated vertical drains
