Acceleration of Self-Weight Consolidation Settlement by Prefabricated Vertical Drain Board

In dredging and reclamation, self-weight consolidation of marine clay need relatively long time. In this study, to accelerate self-weight consolidation time laboratory large size column test were performed using prefabricated vertical drain board. And also presented optimum time of prefabricated vertical drain board insert. Prefabricated vertical drain board-test result showed l/2 time to consolidation compared to Selfweight consolidation-test. Therefore, It can be judged that in reclamation of dredged marine clay, prefabricated vertical drain board can used to accelerate self-weight consolidation.

Managing the Construction Process (4th Edition)

Managing the Construction Process: Estimating, Scheduling, and Project Control, Fourth Edition, covers all areas of the Construction Management industry—with a balanced focus on both theory and practicality. Helping students gain a working knowledge of the whole Building Industry, this text provides the technical skills required to manage a construction project from conception through occupancy. Emphasizing current industry practices, it makes a useful reference for the construction professional.

Constitutive Modeling of Geomaterials: Principles and Applications

Evaluation of Discharge capacity of prefabricated vertical drain

Prefabricated vertical drains are widely used in Singapore for land reclamation to accelerate the consolidation process of the clay. There are several key properties that affects the performance of the vertical drain and in which national test standards have been established and adopted for used. However, one key parameter of the vertical drain is the discharge capacity in which the adopted test standard does not really measure the vertical drain performance. This paper highlights some of the performance parameters of the vertical drain used in Hong Kong and Singapore. At the same time it also highlights the various methods used in Singapore that attempts to measure the discharge capacity of the vertical drain. It also discusses some of the factors that will affect the discharge capacity results.

Predictions and Performances of Prefabricated Vertical Drain Stabilised Soft Clay Foundations

In this paper, the analytical solution for radial consolidation of soft soils is proposed considering the impacts of the variation of volume compressibility and permeability. The Cavity Expansion Theory is employed to predict the smear zone caused by the installation of mandrel driven vertical drains in soft clay. The smear zone prediction is then compared to the data obtained from the large-scale radial consolidation tests. Furthermore, the advantages and limitations of vacuum application through vertical drains in the absence of high surcharge embankments are discussed using the proposed solutions. The applied vacuum pressure generates negative pore water pressure, resulting in an increase in the effective stress, which leads to accelerated consolidation. Analytical and Numerical analysis incorporating the equivalent plane strain solution are conducted to predict the excess pore pressures, lateral and vertical displacements. The equivalent plane strain solution can be used as a predictive tool with acceptable accuracy due to the significant progress that has been made in the past few years through rigorous mathematical modelling and numerical analysis developed by the primary author and co-workers (Indraratna et al., 1992 – 2005).

Several case histories are discussed and analysed, including the site of the 2nd Bangkok International Airport. The predictions are compared with the available field data, confirming that the equivalent plane strain model can be used confidently to predict the performance with acceptable accuracy. Difficulties in assuring good performance can also be analysed and interpreted through mathematical modelling, thereby enabling due caution in the design and construction stages. The research findings verify that the role of smear, drain unsaturation, and vacuum distribution can significantly affect soil consolidation, hence, these aspects need to be modelled appropriately in any numerical analysis to obtain reliable predictions.

Prefabricated Vertical Drains for Enhanced In Situ Remediation

Prefabricated vertical drains (PVDs), also known as wick or strip drains, commonly used to accelerate consolidation of fine-grained soils and sludges, have been successfully demonstrated for enhancing in situ remediation of contaminated soils and groundwater. Over the last decade, the technology basis was developed for using PVDs to accelerate in situ flushing, i.e., removal of contaminants below the groundwater table. During the last five years, the basis for using PVDs to enhance soil vapor extraction systems, i.e., removal of contaminated soil gas in the vadose zone was developed. Both of these geosynthetic applications have been field demonstrated on a limited basis. The first at an abandoned TCE evaporation pond at a U.S. Department of Energy processing plant and the second at a municipal solid waste landfill experiencing subsurface lateral migration of methane gas. The PVD enhanced remediation technologies have yet to find wide acceptance and utilization. Perhaps if several remaining issues are resolved and additional, well-instrumented field demonstrations are performed with results implemented in a design manual, consultants, remediation contractors and regulatory agencies will begin to include and utilize these technologies among their remediation options. In this paper we present an overview of the PVD-remediations technologies, a brief description of some past field demonstrations and our thoughts on research/development issues necessary to further the use of this technology.

FILTRATION CRITERIA FOR PREFABRICATED VERTICAL DRAIN GEOTEXTILE FILTER JACKETS IN SOFT BANGKOK CLAY

Filtration tests on soil-geotextile filter systems were conducted in the laboratory in order to evaluate the filtration and clogging performance of prefabricated vertical drain (PVD) geotextile filter jackets in soft Bangkok clay. Initially, the flow was very slow for all types of PVD geotextile filter jackets and the soil permeability characteristics controlled the flow behavior. Subsequently, flow increased with time followed by a loss of fine particles. Finally, flow decreased and reached an equilibrium stage. As a result of the laboratory filtration tests, filtration and clogging criteria are proposed for geotextile filter jackets on PVDs in soft Bangkok clay.

Design curves for Prefabricated Vertical Drains

Vertical drains and preloading are very effective and economical ground modification techniques for accelerating primary consolidation and compensating some secondary compression of soft compressible soils. If vertical sand drains are used, they can be installed at different diameters. The drain diameter required thus becomes a dependent variable in the design process and the drain spacing is determined a priori. The required parameters can be obtained after a few iterations. However, the number of iterations may increase significantly when prefabricated vertical drains or strip drains are used as the drain size is predetermined by manufacturers and available only in a very limited range. Design curves are developed for prefabricated vertical drains in this paper. The equivalent drain diameter is used as the independent variable and drain spacing becomes the dependent variable. Soil smear around the drain is considered but well resistance of the drain is neglected. The curves can be used to design a vertical drain system without unnecessary iterations and/or interpolations when the equivalent drain diameter, degree of consolidation required, time available, and pertinent geotechnical engineering properties of the soil to be consolidated are given.