Vertical Drainage System Research Articles

Increase of bearing capacity of foundation soil in Port of Koper (Slovenia)

The Port of Koper is situated in the northern part of Adriatic Sea and is the only maritime port for Slovenia to handle its seaborne cargoes. All port terminals and structures need high bearing capacity of foundation soil in the case of shallow foundations or require deep foundations for their construction elements, which is considerably more expensive. The entire Port of Koper was built on the area, acquired with dredging and reclaiming from the shallow sea bottom. Till 1969 the sea depth on this area was about 2m. It was reclaimed with dredged material from the sea bottom till level about +1m msl and after that the area was filled with moulded marl and crushed rock till level about +3m msl. From the soil investigation it can be seen that the soil layers consist of weak silty and clayey soils with low bearing capacity. For the shallow foundation the bearing capacity of the foundation soil has to be improved. To increase the bearing capacity and to accelerate the consolidation, gravel piles in a polymer meshes and preloading with the embankment have been installed at the site. During the consolidation process the ground water was filtered up because of preloading embankment, using gravel piles as vertical drainage system. The whole system was equipped with observation points for settlement observations and we were able to observe the soil consolidation degree. The results of settlement readings during preloading time on the site, were exceptional close to computational ones based on the theory of elasticity with mean modules of compressibility and to those based on the theory of finite elements.

Vertical and horizontal purging of contaminated groundwater in confined spaces

This paper presents the design and field application of a cost-effective, combined vertical and horizontal drainage system used to extract contaminated The purge system was used to drain chromium and trichloroethylene contamination. The design resulted in a 40% cost reduction over traditional remediati

Application of vertical drainage to dewatering seacoasts

One of the most common difficulties arising when building roads and railway lines in seacoast areas is the high watertable in these regions. Among the applied dewatering methods, the most effective seems to be vertical drainage permanently lowering the level of underground water. Application of this method has also been carried out in Iraq. One should consider the fact that the vertical drainage method permits dewatering of not only the existing targets but also the areas designated for new construction. Lowering the watertable allows stabilization of the bed, and that secures stability and resistance of the foundation. The vertical drainage system depends upon underground water intake flowing to the drains from the directions of watershed in order to avoid its damming up under the building site.

Vertical drainage in the foundation of the overflow dam of the Dneprodzerzhinsk hydroelectric station

1. The seasonal variations of the discharge and piezometric heads noted in the results of the on-site observations indicate the presence of seasonal deformations of the seepage medium, which with the course of time, evidently, can lead to changes in the state of the contact zone of the dam foundation. 2. The results of measuring the temperature of the seepage flow make it possible to distinguish weakened areas of the foundation subject to special monitoring and to estimate the degree of influence of the lower pool on the drainage discharge. According to an approximate evaluation, the inflow from the lower pool does not exceed 10% of the total discharge. The data of the temperature measurements confirm the overall effectiveness of the vertical drainage system for discharge of the flow in the dam foundation. 3. The wells of the vertical drainage system, accessible for measuring the discharge and water temperature and also for conducting experiments with tracers, can serve as a means of reliable monitoring of the state of the watertight and drainage devices in the foundations of concrete structures and can give additional valuable information about the development of seepage processes in the foundation of the structure.

Consolidation by vertical drains

A theory is described which can be used in designing a vertical drainage system. This theory incorporates important parameters such as vertical discharge capacity, remoulding effects during installation and filter resistance. The importance of these parameters is widely recognized, but very seldom taken into account in the design, by engineers. Six well-documented case records, related to different drain types are briefly presented. Experience gained from these case records shows that in many cases, even if the overall performance appears successful, there are aspects of soil/drain behaviour that cannot be explained on the basis of existing theories. L'article décrit une théorie que l'on peut appliquer à la conception d'un système de drainage vertical. Cette théorie renferme d'importants paramètres tels que la capacité de décharge verticale, les effets du remaniement pendant l'installation et la résistance de filtration. L'importance de ces paramètres est reconnue par bien des ingénieurs, mais ils en tiennent rarement compte au stade de la conception. L'article donne une description sommaire de six cas bien documentés dans lesquels divers types de drains sont utilisés. L'expérience acquise grâce à cette étude de cas montre que, très souvent, même si l'efficacité globale semble satisfaisante, il existe certains aspects du comportement sol/drains que l'on ne peut expliquer sur la base des théories existantes.

Soil stabilisation for the wolfurt freight depot : Ground Engng, V11, N1, Jan 1978, P20–22,44

The site selected for building a new freight depot and switching yard was found completely unsuitable for building. It was decided to consolidate the soil sufficiently to enable the site to be used for rails and switches by means of a vertical and horizontal drainage system as well as by surcharge loading. First, a large number of core drillings were made to a grid pattern. Consolidation time was found to depend primarily upon the distance between the drains and to a lesser extent upon the thickness of the layer. Once the pre-tests and theoretical calculations were complete, a stabilization plan for the subsoil was decided. In order to avoid the formation of an undesireable lubricant layer on the walls of the drill holes of the vertical drains, the drilling apparatus that was used loosened the soil and transported it to the surface by means of flushing with water only. High demands were placed on the drainage sand and on the fill material used for loading and surcharge. Measurement points were placed at ten spots in the area and were equipped with porewater pressure meters, depth gages, surface gages, and water level pipes. It was thus possible to determine the connection between settlement and excess porewater pressure in the individual layers of soil. The soil stabilization process for the freight depot together with the comprehensive theoretical investigations led to the corroboration of theory with practice. It was proved that peaty soils do not adversely affect the action of vertical drains when these are properly installed. In addition these soils followed the settlement process described in the Terzaghi-Frohlich theory of consolidation. Also, it was possible to predict a high percentage of the settlement.

Wick drains employed on malton by-pass : Beyer, M G; Falconer, J S Ground Engng, V11, N1, Jan 1978, P16–18

The purpose of this new type of vertical drainage system is to accelerate the process of consolidation of soft alluvial deposits under embankment loading. An economical method of accelerating the consolidation process is achieved by shortening the distance between the drainage paths by means of highly permeable vertical drains inserted into the ground. The wick drain is a high quality special non-woven polyester fabric which is resistant to all acids and basic chemicals in soils, to bacteria, frost, and UV radiation. Its pore volume in excess of 80% accounts for the drain's high water transmissibility. The wick drain is 300 mm wide and 4 mm thick and is supplied in roles of up to 300 m in length. The route of the bypass crosses a flood plain before rejoining the original truck road. Problems were anticipated with settlement and stability of the embankments. Because of potential flooding, the embankment was formed above the flooding level with rock fill arising from the cutting. To reduce the drainage path within the aluvium and accelerate the consolidation settlement and increase shear strength, vertical drains were installed to an average depth of 5 m below ground level. A specially designed tubular steel lance was vibrated into the ground through which the wick drain was passed through and into the ground. The drain was then cut off approximately 0.5 m above ground level. Instrumentation was provided to monitor the construction of the embankments as well as both the drained and undrained areas of the special embankment.