Use Of Vertical Drains Research Articles

Prediksi Penurunan Konsolidasi Menggunakan Preloading dan Prefabricated Vertical Drain dengan Software Metode Elemen Hingga

Consolidation is the process of removing water from the pores of the soil which causes changes in the volume of the soil which results in damage to the construction above it. This is more fatal if the decline that occurs is local. Nowadays the use of vertical drains is increasingly in demand, especially with the Prefabricated Vertical Drain (PVD) system which can reduce the time of the soil consolidation process significantly from several years to a matter of months and with technological advances, software is created that can make it easier to calculate construction work with computer programs, one of which is the only finite element method software (Plaxis) to calculate the consolidation settlement process. This study aims to analyze using Finite Element Method software with the help of 2D and 3D plaxis programs to get the consolidation settlement size. The results of 2D and 3D modeling will be compared so that the results that are closest to the field conditions are obtained. From the results of the analysis, it can be concluded that the magnitude of the decrease in Plaxis 3D is closer to the settlement plate data S29 with a decrease of 6.956m or a difference of -0.234m, while the magnitude of the decrease in Plaxis 2D is 7.491 with a difference of decrease of 0.301m.

The mechanism and effects of subgrade fluidisation under ballasted railway tracks

The rapid growth in railway infrastructure and the construction of high-speed heavy-haul rail network, especially on ground that is basically unsuitable, poses challenges for geotechnical engineers because a large part of the money invested in the development of railway lines is often spent on track maintenance. In fact around the world, the mud pumping of subgrade fines is one of the common reasons why track performance deteriorates and track stability is hindered. This article presents a series of laboratory tests to examine following aspects of mud pumping: (1) the mechanisms of subgrade fluidisation under undrained condition, (2) the effects of mud pumping on the engineering characteristics of ballast, and (3) the use of vertical drains to stabilize subgrade under cyclic loads. The undrained cyclic triaxial testing on vulnerable soft subgrade was performed by varying the cyclic stress ratio (CSR) from 0.2 to 1.0 and the loading frequency f from 1.0 to 5.0 Hz. It is seen from the test results that for a specimen compacted at an initial dry density of 1790 kg/m3, the top portion of the specimen fluidises at CSR = 0.5, irrespective of the applied loading frequency. Under cyclic railway loading, the internal redistribution of water at the top of the subgrade layer softens the soil and also reduces its stiffness. In response to these problems, this paper explains how the inclusion of vertical drains in soft subgrade will help to prevent mud pumping by alleviating the build-up of excess pore pressures under moving train loads.

Inclined Perimeter Drains Performance as Liquefaction Countermeasure Techniques Below Existing Buildings

Reducing the risk of structural damage due to earthquake-induced liquefaction in new and existing buildings is a challenging problem in geotechnical engineering. Drainage countermeasure techniques against liquefaction have been studied over the last decades with an emphasis on the use of vertical drains. This technique aims to allow a rapid dissipation of excess pore pressures generated in the soil during the earthquake thereby limiting the peak excess pore pressures and consequently improve the structural response. Rapid drainage in the post-earthquake period in the presence of these drains helps quick recovery of the soil strength. Recent studies propose different variations in the vertical drains arrangement to improve the excess pore pressure redistribution in the soil around structures. However, conventional arrangements for existing buildings do not achieve an adequate proximity from the drains to the soil below the foundation. To address this, the performance of inclined and vertical perimeter drain arrangements are studied in this paper. Dynamic centrifuge tests were carried out for the different arrangements in order to evaluate the excess pore pressure generation due to ground shaking and the following dissipation together with the foundation settlement and dynamic response.

Improved Design Procedures for Ground Improvement using Pre- Fabricated Vertical Drains

Background/Objective: Ground improvement for soft saturated clay soil is often achieved by preloading combined with vertical drains. Use of vertical drains gives rise to smear zone and well resistance, which hinders consolidation. However, Indian code of practices doesn’t consider this aspect. Method: Computation of optimum spacing for vertical drains is iterative and tedious procedure. Therefore, an automate procedure using goal seek function of MS Excel is developed which gives optimum spacing instantly. Using developed spreadsheet, effect of smear zone has been studied by comparing field data to that obtained by using theoretical equations. Findings: Time estimates for target value of consolidation required in a project are better predicted by considering smear effects. Based on these findings it has been suggested to incorporate the effect of smear zone in Indian Codes for rational design of PVD. Application/Improvement: Using proposed modifications in Indian code of practices realistic estimate for desired consolidation can be found quickly.

Application of Multi-Directional Flow Consolidometer for a Constant Rate of Strain Consolidation Test Under Various Drainage Conditions

Abstract The use of vertical drains in the field demands sophisticated laboratory consolidation testing under various drainage conditions. In this study, a multi-directional flow consolidometer was developed for the constant rate of strain (CRS) consolidation test. This device provides variability in controlling the drainage direction (e.g., vertical, radially inward, radially outward) during K0 consolidation. For each drainage condition, relevant theories for interpreting the CRS testing data have been derived. Reconstituted kaolinite specimens were consolidated at a constant rate of 2.9%/h using the developed device with various drainage directions. The results showed consistent compression behavior, and the anisotropic coefficient of consolidation confirmed the applicability of the device in experiments involving in situ consolidation.

Review of mehods of analysis for the use of vacuum preloading and vertical drains for soft clay improvement

The use of vertical drains with vacuum preloading for soft soil improvement has become a booming interest in recent years. In this paper, theoretical and practical developments of the utilization of vertical drain with vacuum preloading are currently reviewed. Geotechnical aspects of factors affecting the performance of vacuum consolidation and conversion procedure for multi-drain analysis are discussed based on the current state of the art. The salient aspects of selected case histories on soft clays and land reclamations are elucidated.

Effects of an Abutment Construction on Soft Soil on a Neighbouring Structure: Influence of Different Construction Techniques Using Geosvntheties

The topographic and geological conditions of several regions in Brazil favour the formation of large deposits of soft soils. Sometimes this requires the use of innovative techniques to allow constructions of geotechnical works in these sites. The presence of deep soft foundation soils has led to an increasing number of reinforced bridge abutments being built in the last years. However, little is known on the behaviour of such works, particularly with respect to displacements and bending moments induced in the neighbouring bridge foundations due to the construction of the embankment. In this paper, hypothetical bridge abutments were modelled, with and without the presence of geosynthetic reinforcement, aiming to evaluate the effects of the embankment construction on the foundations of the neighbouring bridge. The effects of the use of vertical drains and piles with caps underneath the embankments were also investigated. The results obtained clearly indicated the potential of the use of reinforcement, vertical drains or piles to reduce damages to the foundations of neighbouring structures caused by embankment construction. The use of vertical drains in conjunction with geosynthetic reinforcement showed an important effect on the reduction of horizontal displacements and moments in the piles of the bridge.

Effectiveness of vertical drains in mitigation of liquefaction

One method of mitigating the damaging effects of earthquake-induced liquefaction is to provide rapid dissipation of excess pore pressures by the use of vertical drains through the liquefiable material. Drain systems are currently designed using a chart-based approach. Field experience suggests that the performance of these installations cannot yet be accurately predicted. In this paper, high quality centrifuge testing is used to help clarify drain behaviour. It will be established, supported by centrifuge test data, that the pore water from a radially expanding zone of soil contributing to drainage through the drains is developed. Naturally, the geometry of this expanding zone changes with time. It will be shown that fluid from deeper strata is drained first, reducing the effectiveness of the drain for near-surface soil layers. It is concluded that these zones are useful in analysing more complicated drain system geometries.

Modelling consolidation accelerated by vertical drains in soils subject to creep

The settlement of embankments and reclamations over soft soils is frequently accelerated by the use of vertical drains. The magnitude of long-term settlement is sometimes reduced by the use of surcharge, although there is often uncertainty about how long the surcharge should be maintained to minimise creep movement. The design of vertical drains is generally based on closed-form solutions of Terzaghi's consolidation equation, and rarely takes into account non-linear stiffness and creep of the soil. In this paper a one-dimensional finite difference consolidation analysis is outlined showing how vertical and radial drainage of a multi-layer soil profile in the zone of influence of a vertical drain may be modelled. The analysis allows inclusion of a zone of peripheral smear around the drain and drain resistance, permeabilities may be varied with void ratio, and creep is modelled both during and after primary consolidation. The application of the model is illustrated with back-analysis of field data from construction of an embankment with temporary surcharge over estuarine alluvium.

Modelling consolidation accelerated by vertical drains in soils subject to creep

The settlement of embankments and reclamations over soft soils is frequently accelerated by the use of vertical drains. The magnitude of long-term settlement is sometimes reduced by the use of surcharge, although there is often uncertainty about how long the surcharge should be maintained to minimise creep movement. The design of vertical drains is generally based on closed-form solutions of Terzaghi's consolidation equation, and rarely takes into account non-linear stiffness and creep of the soil. In this paper a one-dimensional finite difference consolidation analysis is outlined showing how vertical and radial drainage of a multi-layer soil profile in the zone of influence of a vertical drain may be modelled. The analysis allows inclusion of a zone of peripheral smear around the drain and drain resistance, permeabilities may be varied with void ratio, and creep is modelled both during and after primary consolidation. The application of the model is illustrated with back-analysis of field data from cons...

Soil improvement works for Changi East Reclamation Project

Reclamation in Changi East, Singapore involved the formation of 2000 ha of land. The use of prefabricated vertical drains, combined with surcharge, was required to accelerate the consolidation settlement of the underlying soft compressible soil throughout most of the area. The fill used was marine dredged sand which was placed mainly by hydraulic means and densified by various deep compaction methods such as dynamic compaction, vibroflotation and Müller resonance compaction. A comprehensive instrumentation scheme was used to monitor the process of consolidation. The various methods used for assessing the performance of the soil improvement works, namely soil instrumentation, in situ tests and laboratory tests, are also discussed. The soil improvement works, which included the treatment of a siltpond filled with ultrasoft soil and three pilot tests associated with the use of vertical drains, are also described and discussed. La récupération de terre en Changi Est à Singapour comprend la formation d'un terrain de 2000 hectares. Des drains verticaux préfabriqués sont combinés avec une surcharge pour accélérer le tassement du subsol compressible dans la plupart de la surface. Nous remblayons avec du sable dragué du mer et placé principalement par la méthode hydraulique et densifié par un nombre de méthodes de compactage, comme le compactage dynamique, la vibroflotation et le compactage résonance de Müller. Le procès de consolidation est contrôlé par un programme d'instruction détaillé. De plus, nous discutons des méthodes utilisées pour évaluer la performance du système de stabilisation, notamment l'instrumentation du sol, et les essais sur place et en laboratoire. Enfin, le système de stabilisation du sol, qui comprend le traitement d'un bassin de vase rempli de sol très mou et 3 épreuvespilote associés avec l'usage de drains verticaux, est décrit et discuté.

Geotechnical engineering for the Medway tunnel and approaches

The design and construction of the Medway immersed tube tunnel and approach structures required a thorough investigation of the site and a detailed understanding of the geology and geotechnical behaviour of the soils. The paper describes the ground investigation and discusses how the design accommodated the ground conditions to allow the tunnel and approach structures to be safely and efficiently constructed. Two main geotechnical challenges are described; the approach embankments and the casting basin in which the immersed tube tunnel sections were constructed. Part of the approach embankment was constructed over very soft soils. The construction made use of vertical drains, stage construction and preloading to ensure that the embankment was constructed economically within the available programme. The immersed tube tunnel sections were constructed in a casting basin next to the river. The design of the casting basin required careful consideration of the stability of the temporary slopes and the dewatering system had to deal with large quantities of water without causing significant settlement of some sensitive nearby structures. These two areas are discussed and details of the construction and performance are provided.

Ground improvement engineering – the state of the US practice: part 1. Methods

The US practice of ground improvement is divided into six main categories: densification, consolidation, reinforcement, chemical treatment, thermal stabilization and biotechnical stabilization. Densification, which applies mainly to granular soils, includes vibrocompaction, dynamic compaction, blasting and compaction grouting. Consolidation is basically achieved through preloading and the use of vertical drains. Soil reinforcement is divided into two groups: those involving compacted fill such as mechanically stabilized backfill systems, and those applied in situ such as soil nailing, element walls, micropiles and stone columns. The chemical treatment methods discussed are those applied at depth such as permeation grouting, jet grouting, deep soil mixing and lime columns. Thermal stabilization is covered through ground freezing and its use in urban construction. Finally, biotechnical stabilization, which is one of the latest developments in the field, is briefly presented. Discussed in the paper are the applications, advantages, limitations, design and construction aspects of each ground improvement method as well as the durability and long-term performance of the improved ground. The use of ground improvement in environmental engineering is briefly highlighted.

Comparison of the Hyperbolic and Asaoka Observational Method of Monitoring Consolidation with Vertical Drains

The use of vertical drains and surcharge to accelerate the consolidation of clayey soils is well established in soil improvement technology. For this method of soil treatment, it is important to monitor the progress of consolidation where the average degree of consolidation is usually defined as the ratio of current settlement to the ultimate settlement due to primary consolidation. An accurate estimate of the ultimate primary settlement is, therefore, required in order to determine the state of consolidation, and the appropriate time for surcharge removal when the desired degree of consolidation has been achieved. Recently, Tan (1995) proposed a new hyperbolic method to identify the 60% and the 90% consolidation stages from field settlement data due to one dimensional consolidation. Knowing the settlement at these points, it is possible to determine the ultimate primary settlement. Once sufficient data has been recorded to identify the linear portion of the hyperbolic plot between the 60% to 90% consolidation stages, the method can be employed. This method has been validated by application to various well documented case histories in the published literature. In Japan, however, Asaoka’s method for estimating ultimate primary settlement from field observation has been widely used and is well accepted by the geotechnical engineering community. This research paper presents a comparison of two different observational methods for monitoring the progress of consolidation to determine their similarity and differences, and their accuracy of predictions compared to actual observations. First, the theoretical basis of the two methods are examined. It was found that settlement data beyond the 60% consolidation stage are needed in both methods to make accurate predictions of ultimate primary settlement. Next, both methods are applied to oedometer laboratory consolidation data for kaolin specimens in order to determine how prediction of ultimate primary settlement and coefficient of consolidation would compare in carefully controlled laboratory experiments. Finally, both methods are applied to several well documented case histories of vertical drain projects, and the predictions of ultimate primary settlement and in situ coefficient of consolidation are compared. It was found that both methods gave good agreement with predictions, making them complementary tools for use in monitoring consolidation in field applications.

Finite element analysis of soil containing vertical drains : Russell, D Ground EngngV25, N6, Aug 1992, P20–24

The construction of embankments over soft, compressible soils can cause considerable problems to the geotechnical engineer. Expedients such as reinforcement, vertical drains or stage construction are often necessary to achieve an efficient, economical design. The analysis of such embankments becomes complex and requires the use of a numerical technique such as the finite element method. Although the use of vertical drains has become widespread in embankment construction the finite element analysis of such problems has only occasionally been reported. The reason for this may be the difficulty in equating the plane strain embankment analysis with the essentially axisymmetric consolidation behaviour of the soil surrounding a single vertical drain. In this paper a method for the plane strain finite element consolidation analysis of soil improved by vertical drains is presented. The consolidation of axisxmmetric and plane strain unit cells, representing the soil around a single drain, are compared for a normally consolidated clay deposit. The clay formed part of the subsoil at a well documented construction project which has been analysed in full plane strain. Results from the finite element prediction are compared with published observed behaviour. All the finite element analyses were performed using a modified version of the program CRISP. (A)

Improvement of soft Bangkok clay using vertical drains

This paper presents case records demonstrating the use of vertical drains on soft Bangkok clay. The documented cases include four sand drains and two prefabricated vertical drains. The observed performances of the vertical drains are evaluated. The effects of soil flow parameters, including smear effects due to the installation of the drains, in particular the prefabricated vertical drains, are also evaluated in the light of the current practice of using vertical drains for ground improvement. It is concluded that the use of vertical drains is a viable ground improvement method for soft Bangkok clay.

Use of vertical drains for soil improvement at bridge approaches : Woo, S M; Cheng, L K; Dawn, J D; Ou, C D Proc 8th Southeast Asian Geotechnical Conference, Kuala Lumpur, Malaysia, 11–15 March 1985V1, P2/23–30. Publ Kuala Lumpur: Organising Committee, 1986

Use of vertical drains for soil improvement at bridge approaches : Woo, S M; Cheng, L K; Dawn, J D; Ou, C D Proc 8th Southeast Asian Geotechnical Conference, Kuala Lumpur, Malaysia, 11–15 March 1985V1, P2/23–30. Publ Kuala Lumpur: Organising Committee, 1986

Environmental Systems Optimization.

This book is described as a Symposium in Print. It contains five papers on vertical drains which were printed initially in the March 198 1 issue of Geotechnique. In May 1981, a half-day meeting was jointly organized by the British Geotechnical Society and the Institution of Civil Engineers to discuss vertical drains using the papers as a basis. The Institution subsequently published the five papers, together with their discussions in this book entitled Vertical clrains. Of the 160 pages, 90 are devoted to the papers and 70 to the discussions. With the development of new types of prefabricated drains and installation equipment and the economies associated with them, there has been renewed interest in the use of vertical drains to improve soil conditions. The various papers deal with the many aspects of the subject, from the types of field and laboratory investigations required to the practical aspects of drain installation, design methods, and costs. A number of case histories are also presented, including some describing unsuccessful examples. In the discussion section, some of the authors provided additional performance data that was not available at the time of preparing the original papers. The discussions deal with all aspects of the subject and provide a valuable addition. For anyone interested in the application, design, and installation of vertical drains, this book provides an excellent state-of-the-art coverage of the subject and should be considered as must reading for the practising foundation specialist.

Consolidation of soil using vertical drains

The use of vertical drains is examined critically in view of the fact that in half a century of use there have been a large number of occasions when vertical drains have failed to promote a more rapid consolidation of the soil under load. The mode of operation of the drain is discussed and it is shown that an understanding of this has affected the design of the more recent band-shaped drains. The effects of smear and drain resistance are also discussed. Reference is made to a three-dimensional finite difference computer program, modelling the flow of excess pore water in the drain and the surrounding soil which is used to aid in the drain design. Specific cases which can also be analysed by published techniques have been used to check the validity of the model. Consideration is also given to the methods of site investigation which should be employed to obtain the appropriate soil parameters for design. Cases are cited where a lack of data on the soil parameters has restricted the design of the vertical drainage schemes. L'utilisation de drains verticaux fait l'objet d'une analyse critique car au cours d'un demi-siècle de service, les drains verticaux se sont révélés, à maintes reprises, incapables de permettre une consolidation plus rapide du sol sous chargement. L'article décrit le mode de fonctionnement d'un drain et montre comment la compréhension de ce mode a influencé la conception des drains récents en forme de bande. Il étudie également les effects de l'étalement et de la résistance des drains. L'article se réfère à un programme informatique à différences finies tridimensionnel qui model isele débit de l'eau interstitielle excédentaire dans le drain et le sol environnant; celui-ci sert à faciliter la conception des drains. Des cas spécifiques qui peuvent également être analysés à l'aide de techniques existantes déjà publiées ont été utilisés pour vérifier la validité du modèle. L'article traite également des méthodes d'exploration in situ qui doivent être utilisé eb pour obtenir des paramètres du sol appropriés en vue de la conception. Il présente des cas où un manque de données concernant les paramètres du sol a considérablement limité la conception de systèmes de drainage vertical.