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By Javier Rodriguez

Adaptive re-use of existing structures in urban environments has become very common due to lack of available space in our cities and requirements for increased structural capacity. Often, it involves retrofitting existing foundations to support increased loading. In such cases, Engineers face the need to review existing deep or shallow foundations for their true load carrying capacities in order to determine the required magnitude of retrofit work, if any. To accomplish this, the engineer must track down and cull through the existing construction documentation to determine what was actually constructed, complete an investigation to confirm these conclusions, possibly sample the foundation elements for strength properties, and on occasions complete non destructive or full scale load testing of indicator elements. This paper describes the typical procedure followed by the authors for design of retrofit schemes for existing buildings in the Washington DC metropolitan area. Three case histories are presented that illustrate various issues encountered during design.

Jan 1, 2006

By Darrell Wilder

When designing excavation support systems in urban environments, it is often necessary to consider the effect of vertical surcharge loads from adjacent structures. Several methods are used in practice to establish the horizontal surcharge-induce pressure on the excavation support. According to the experience of the authors, these methods often seem to overestimate the effect of the surcharge and may have significant impact on the construction costs. This paper explores several of these procedures and provides a discussion as to the reasons for the differences in surcharge effect predictions between different procedures. It also provides practical recommendations for designers dealing with excavation support design.

Jan 1, 2006

By Jeff Jackson, Paul Axtell, David Graham

The Montana Department of Transportation recently awarded a contract to construct a replacement bridge across the Clark Fork River in Heron, MT. Both abutments and both intermediate bridge bents were to be founded on 6-ft and 8-ft diameter, permanently cased drilled shafts with rock sockets, respectively. Two drilled shafts per substructure location were designed for a total of eight drilled shafts. The original design included 6-ft diameter drilled shafts at the abutments but the Contractor elected to submit a Value Engineering proposal that increased them to 8-ft diameter. On the basis of the subsurface exploration program, extremely challenging subsurface conditions were known to exist, including the potential presence of large boulders within the predominantly sand and gravel soil matrix. The successful bidder elected to use an oscillator to install the permanent casing to the top of bedrock, while simultaneously removing the spoils from inside the casing with a clam-grab. On seven of the eight shafts, this approach worked well. Unfortunately, on one of the shafts, the casing met refusal on one or more boulders encountered in the predominantly sand and gravel soil overburden. Following several attempts, and despite several variations of approaches, it was determined that the casing could not be advanced beyond the obstruction without unacceptable risks to the pile-supported temporary work trestle (i.e., loss of soil and reduction in pile capacity for the foundations supporting the work trestle). To mitigate the problematic drilled shaft, a unique solution was designed and successfully constructed. The solution involved the construction of seven 16-in diameter micropiles constructed within the confines of the obstructed casing. The micropiles were drilled to bedrock through the sand, gravel, and boulders and include rock sockets to satisfy axial design requirements. The micropile casing thickness, grade and grout strength were designed to provide adequate flexural strength as well as to satisfy other design requirements. Upon completion of the micropile installation, the upper portion of the drilled shaft above the boulders and within the permanent casing was constructed as usual. This paper discusses the difficult subsurface conditions at the site, the drilled shaft construction difficulties, and the design and construction of the micropile solution.

Jan 1, 2018

By Ken Andromalos

Continued population growth combined with limited water resources in the Denver area has resulted in the conversion of a number of mined out gravel pits in the area into municipal water storage facilities. The use of slurry walls provides a cost effective means of isolating groundwater to convert these pits into efficient water storage facilities. Design considerations include: stability, underlying bedrock conditions, backfill mix design and earthwork requirements. Installation issues during construction include: trench stability considerations when excavating through relatively clean sand and gravel deposits in potentially high groundwater conditions; keying into three to ten feet of fractured claystone, siltstone or sandstone that makes up part of the Denver formation, and quality assurance procedures to assure a proper groundwater barrier is constructed. The paper concludes with two brief case histories to illustrate how these considerations are applied

Jan 1, 2007

By Kodi Ranga Swamy, N. Sankar, M. Akhila

"Until recently, liquefaction-related studies concentrated on clean sands believing that only sands are susceptible to liquefaction. However, a few earthquakes like 1976 Tangshan earthquake, the 1989 Loma Prieta earthquake, the 1999 Kocaeli earthquake, the 2010 Chile earthquake, and the 2011 Christchurch earthquake, etc. showed that sand with fines could also liquefy. The research findings on liquefaction of silty soils are limited, and several structures constructed on such soil deposits are damaged during the past earthquakes. Some previous results of research on earthquake events show an increase of liquefaction resistance in silt soils with increase the fines content, but some report the opposite trend. This study presents the results based on undrained triaxial cyclic tests which were carried out on the fine sand with fines (0%, 10%, 20% and 40% fines). The samples were prepared at the required unit weight (Dr = 50%) and saturated by using back pressure and cell pressure increments. Each consolidated sample is subjected to cyclic loading with sinusoidal wave load form at a frequency of 1 Hz. The liquefaction resistance is evaluated in terms of cyclic stress ratio required to cause 100% pore pressure or 20% failure strain occur at 15 numbers of load cycles. Results are presented in forms of pore pressure build up and axial strain propagation plots. As the fines content increased, an increase in liquefaction potential was observed.INTRODUCTIONLiquefaction and related phenomenon have been responsible for tremendous amounts of damage all around the world. In general, the liquefaction may occur in fully saturated sands, silts and low plastic clays. When the saturated soil mass is subjected to seismic or dynamic loads, there is a sudden buildup of pore water within a short duration, and it could not dissipate which leads to reducing the effective shear strength of soil mass. In this state, the soil mass behaves like a liquid and causes large deformations, settlements, flow failures, etc. This phenomenon is called soil liquefaction. As a result, the ability of soil deposit to support the foundations of buildings, bridges, dams, etc. is reduced. Liquefiable soil also exerts a higher pressure on retaining walls.This lateral movement of soil could cause settlement of the retained soil. A sudden build-up of pore water pressure during quake also triggers landslides. Liquefaction damages of structures are commonly observed in low-lying areas near the rivers, lakes, and oceans."

Jan 1, 2017

By Jose L. Garcia

The following document aims to cover all issues concerning the three main methods employed for the in-situ survey of concrete pile integrity. Within it are described both sonic coring and low-strain tests and the frequency and time domain analysis of their results, which are the most advanced techniques currently in use in Spain. The survey techniques described were developed and began worldwide deployment in the 1960s, but it was not until the 1980s that they saw large scale implementation in Spain, largely thanks to the miniaturisation of electronics and computer equipment that made them easier to use on-site. Sonic coring, echo and frequency-response testing or mechanical impedance tests are spreading further every day. However, there appears to be a need for standardisation of the testing methods, as well as their implementation, interpretation and the presentation of results. The goal of these Spanish recommendations is to serve as a guideline for test standards and to provide examples for a correct and commonly agreed interpretation of test results, as well as settling any differences in the evaluation of defects detected in foundation works.

Jan 1, 2006

By Gunhild Hennum, Tewodros Tefera, Gisle Håland, Annette Jahr

"Abstract The Gudrun field is located west of Stavanger in the North Sea at water depth of 109 m. A jacket substructure was selected to support the topside and was installed in 2011. The jacket shall be able to support 16 of 0.762 m (30 in) diameter conductors and is equipped with a drilling deck to allow for pre-drilling by a jack-up rig through the jacket. In general the soil conditions below mudline comprise of a thin top layer of very loose to dense sand overlaying several layers of sandy clay, ranging in stiffness from firm to hard. Below some 30 m depth the soil consists of layers of medium dense to dense silty sand overlaying very hard sandy clay containing thick beds of sand to 100 m depth or more below mudline. The jacket is secured to the seabed by twelve 2.438 m (96 in) diameter steel pipe piles, three at each pile cluster located at the four legs of the jacket at sea floor. Different design methods were used to determine the pile penetration depth. Pile drivability was evaluated using best estimate and upper bound soil parameters. The pile driving and blow count record show that the target penetration was reached as predicted. This paper discusses the different methods used to determine the pile capacity, target penetration depth and the drivability analyses made for the Gudrun jacket piles. The soil resistance during pile driving is back-calculated from the pile installation data and compared with the prediction made.IntroductionThe Gudrun platform is located west of Stavanger in the North Sea at water depth of 109 m. A jacket substructure was selected for the Gudrun platform. The general Gudrun platform jacket configuration is to a large extent dictated by the topside layout, the requirements for support points enclosing the well slots and access for the jack-up rig. The Gudrun platform jacket is a traditional 4 legged structure with a vertical side towards the jack-up rig. At the seabed the jacket is quadratic with a base dimension of 40 by 40 metres. Figure 1 shows the Gudrun jacket during load-out from the fabrication yard to the transport barge. At the site the jacket was lifted off the barge, upended and placed on the seabed by the installation vessel. The jacket is secured to the seabed by twelve 96"" (2.438 m) diameter steel pipe piles, three at each pile cluster located at the four legs of the jacket at sea floor. The target penetration of the piles is 47 m."

Jan 1, 2014

By D. P. Nicholson

The current phase of office development at Canary Wharf in the London Docklands includes twelve multi-storey buildings varying from eighteen to forty stories in height. The area of Canary Wharf South comprises five multi-storey buildings with low level in fill podium and garden areas. Three of these multi-storey buildings have "pile-cap" designs where the entire building load is applied to the piles. The remaining two buildings have "piled-raft" designs where allowance is made in the design for part of the building load to be transferred to the raft formation. Using a piled-raft design approach has enabled savings to be made on the number of piles used below the raft. This paper describes the calibration analysis undertaken to validate the design method. The ground conditions at the Canary Wharf site are typically fill and recent gravel deposits over the overconsolidated clay and sand of the Lambeth Group. Below these strata is the Thanet Sand. The Lambeth Group provided the founding layer for the raft and contributed to the pile shaft resistance. The Thanet Sand stratum provided the bearing layer for the 1.5m diameter base grouted bored piles. The piled-raft design required an assessment of the building load transfer through the raft to the formation layer. This load transfer led to significant increases in effective stress in the soil below the raft and thence a corresponding increased the capacity of the piles. This interaction of the raft with the prepared formation contributed to between 27% and 45% increase in total vertical load carrying capacity of the piled-raft substructure compared with the pile-cap design method. The development of the piled-raft design was carried out in three main phases: ? Development of the approach and validation analyses. ? Design work on various schemes resulting in detailed design packages. ? Validation analyses using full 3D finite element analysis (presented herein). The validation of the piled-raft design approach was initially carried out against published case histories for piled-raft interaction. To improve on the validation work a full 3D finite element analysis of a simplified pile raft and superstructure (which contributes stiffness to the raft) was undertaken; the analysis included only a quarter of the structure due to assumed symmetry of the structure and vertical loading. This 3D validation analysis is presented herein. The analysis was carried out using the Oasys LS-DYNA finite element program. Prior to carrying out the analysis of the piled-raft an initial finite element analysis was carried out to back analyse a fully instrumented field pile test providing accurate modelling of a single pile performance. This back analysis allowed confidence in the soil parameters used in the 3D model; comparisons of shaft and base resistances between the pile test and the FE model calculations for the single pile are presented. The parameters provided in this work were then carried into the full 3D model of the piled-raft. The 3D model of the piled-raft structure included 18 piles (12 full piles and 6 half piles on an axis of symmetry of the model).

Jan 1, 2002

By W. Robert Thompson

Hurricane Katrina caused significant damage to transportation structures on the Gulf coast in August, 2005, including the destruction of the US 90 Bridge over Biloxi Bay, Mississippi. Part of the successful design/build proposal for the replacement bridge included a comprehensive test pile program of indicator piles and load test piles in the geotechnical investigation program. A total of 22 indicator piles were installed on the project using the pile driving analyzer to monitor the pile behavior. Five load tests were performed: two axial Statnamic, two lateral Statnamic, and one static axial. The results of the test pile program established driving criteria for production piles that included end-of-drive blow counts and pile tip elevations with an appropriate allowance for setup. The program also confirmed that the planned installation equipment and techniques of GC Constructors, a joint venture of Massman Construction Co., Kiewit Southern Co., and Traylor Bros., Inc., would install the piles to the design tip elevations before production piles began. An extensive program of restrike measurements at a range of times after initial driving of the indicator piles provided a systematic documentation of pile setup in the soil profiles on the site. These resistance values were used to develop a dimensionless setup factor ?S? as the ratio of the restrike resistance to the end of drive resistance. This factor varied from 1.5 for piles penetrating clays and tipped in sand to 3.0 for piles bearing completely in clay and helped establish an end-of drive blow count that included an allowance for setup. The CAPWAP analyses of restrike data with setup and the load test data were used to confirm the design unit side shear and end bearing values developed from the borings and static capacity calculations and to select the design pile lengths.

Jan 1, 2009

By A. Garassino

A pile design was performed for a thermal power station in Egypt and more than 4000 piles were to be driven. Technical economical reasons suggested the choice of driven composite LACOR piles designed for very high specific loads. Some uncertainties on the behaviour of the pile soil system suggested to perform a test on an instrumented pile. Scope of the test was to verify the possibility of developping the required bearing capacity within the range of the allowable pile settlements values and the effect of the pile joint enlargement on that portion of skin friction to be developped by the upper pile section.

Jan 1, 1991

By Z. Y. Ding

This paper emphasize two points in piled wharf design which are important than structure calculation. First, during design of piled wharf on soft stratum, the bank slope stability is the first important item. Second, the live load, the backfill and the original ground's settlement will influence the wharf structure causes cracks. Two practical examples were illustrated.

Jan 1, 1991

By Alessandro Bertero, Dylan Pearson, Wesley Schmutzler, Matteo Bertoni

"The SR 83/US 331 highway is located in the Florida panhandle, where it connects the Walton County beaches to the I-10 corridor. The roadway is of vital importance to the economy of the area as well as its safety since it represents the primary hurricane evacuation route from southern Walton County. The Florida Department of Transportation (FDOT) decided to increase the number of traffic lanes from two to four and improve the geotechnical properties of the moderately deep, very loose foundation soils, that had affected the highway rideability for years. The soil mixing was selected as the method to meet the unique deep ground improvement challenges of the project. The design required that Shallow Mixing Method (SMM) be used to build a 10-foot thick platform that transferred axial load to the bottom soil layers through a series of Deep Mixing Method (DMM) columns. Upon completion over 8,300 SMM columns and 1,500 DMM columns had been installed, with no remedial work required. Also, only 1% of the almost 1,500 specimens tested did not meet the specification requirements. This paper will describe the challenges encountered and provide valuable information that may be useful for other future projects, including details not previously published.INTRODUCTIONThe counties of Walton and Okaloosa have been a very popular vacation destination for many ears. The 50-mile long coastline boasts beautiful, sugar-white beaches and waters the color of emeralds. The popularity of the area has been growing even further, over the last few years. A consequence of this phenomenon is a fast-paced increase of the traffic flow on the SR83/US331 highway, especially at the bridge that connects the Walton County beaches across Choctawhatchee Bay (Fig. 1) to the heavily traveled I-10 corridor. The highway plays a very important role for the area also as a commercial link and as the primary hurricane evacuation route from southern Walton County. The increase in traffic has produced higher travel time, when not a complete traffic paralysis, and exacerbated the issue of ground settlement where accelerated wearing of road foundation occurred due to the presence of very loose, moderately deep, soils, that had afflicted the highway for several years. The Florida Department of Transportation (FDOT) decided to put an end to these issues by increasing the number of traffic lanes from two to four and improving the geotechnical properties of the foundation soils. The Design-Build Maximum Price Request for Proposal (RFP) issued for the expansion of the Choctawhatchee Bay Bridge saw the participation of numerous D/B teams which produced various technical solutions. Among them, the FDOT selected the Skanska/Parsons Brinckerhoff (General Contractor) proposal which provided for the use of soil mixing as the ground improvement technology. The design/build team assigned Foundation & Geotechnical Engineering (Designer of Record) the ground improvement design which Treviicos South (Specialty Contractor) would execute."

Jan 1, 2017

By Fathi Abdrabbo

Open caissons are used for many geotechnical engineering applications. Open caissons may be used as deep foundation elements bypassing weak soils to tip in firm deeper strata, and in rivers and maritime construction to reduce the risk of scour. Open caissons are also used for collecting sewage water through gravity sewer pipe networks or from sewer force mains. In such applications, the design and construction of open caissons require a detailed soil investigation program. In this way, the design and construction plan of an open caisson can be developed with full knowledge of the prevailing subsoil conditions. The engineering and construction techniques are key factors to achieve functional caissons. Based on close observations during construction stages, the current study presents some challenges that were encountered during the construction of two open caissons of internal diameters 20 m and 10 m (65.6 ft and 32.8 ft). This paper describes the procedure followed to alleviate the construction difficulties encountered. Site exploration program and control measures required to satisfy design and construction requirements are crucial aspects. Sinking of open caissons in dense or very dense sands is risky. Incorrect sinking of open caissons may cause extra cost, delay in construction, and harm to nearby structures. Air/water jetting near the cutting edge of an open caisson, outside slurry trench, and/or inside open trench may be used to drive an open caisson downward. Unsymmetrical work around an open caisson may lead to tilting of the caisson. If this occurs, the tilt should be immediately corrected before resuming the sinking process. Improper cleaning of fine materials on the caisson?s excavation bed, and/or inappropriate pouring of underwater concrete may result in a defective concrete seal. The paper contains a series of practical guidelines to assist those intending to use open caissons, and shares good caisson sinking practice with practitioners. Finally, the study aims to understand the difficulties encountered and to anticipate future problems.

Jan 1, 2012

By Minna Karstunen, Patrick Becker

"Abstract The deformation behaviour of a foundation on deep mixed columns in a natural soft soil is a three-dimensional problem, which has to be considered adequately in numerical modelling. However, simplifications are often made due to the computational costs of fully coupled 3D analyses by either modifying geometry of the problem or material parameters in 2D for plain strain analyses or by modelling the problem as 2D axisymmetric case. The volume averaging technique (VAT) is an enhanced 2D FE technique that enables mapping the 3D problem in two-dimensions, yet modelling the two constituents (column and soft soil) with appropriate different constitutive models within a homogenized material. The performance of the volume averaging technique is demonstrated by considering unit cell simulations of floating and end bearing columns in soft soil. The results with VAT are compared and validated against conventional 2D axisymmetric and fully coupled 3D finite element analyses.IntroductionThe properties of very soft clays, silts and organic soils can be improved by stabilizing agents, such as lime and/or cement that are mixed into the soil in situ by using auger-type mixing tools in situ. Deep mixed columns are extensively used to reduce deformations and to improve the overall stability of embankments and foundations on soft soils. Whilst the most typical applications are embankments, increasingly the method is used under foundations. The first category of applications is very common in Scandinavian countries, whilst the latter application has been pioneered in Poland, as an environmentally friendly (low CO2) and cost effective alternative for piling. Due to economic and environmental reasons there is an increasing interest in the technique elsewhere in Europe. With deep mixing, the strength and deformation properties of the soft soil can be improved, and the risk of unwanted deformations is substantially reduced.Numerical methods, such as finite element (FE) analysis, can be used as an alternative to conventional design methods. They are particularly suitable when considering serviceability limit state, i.e. deformation analyses under working loads. FE analyses allow using advanced constitutive models that take account of the complex stress-strain behaviour of natural soil and stabilized columns, respectively. The problems that involve a grid of circular columns under an embankment or a strip footing are fully three-dimensional problems. As 3D analyses are very laborious and expensive, an enhanced 2D technique using the so-called volume averaging technique (VAT) is utilised. The basic idea is to describe the column-improved ground as a homogenized composite material, and using clever mathematics to map the true 3D problem into 2D. Once the constitutive relations of both composites are defined, the response of the column-improved ground can be simulated in 2D subject to arbitrary loading and boundary conditions."

Jan 1, 2014

By George J. Tamara

The urban environment presents special challenges for the design and construction of earth retention systems. Complications arising from difficult subsurface conditions are compounded by the presence of urban infrastructure and existing and prior construction. The proximity of adjacent structures as well as intense prior use can cause special concerns including the potential for archeological artifacts or contaminated ground or ground water. Utilities and structures may be particularly vulnerable to the effects of ground movement, dewatering and vibrations. Difficulty of access, congestion and limited work areas may severely restrict means and methods of construction. Dewatering may be limited or prohibited because of concerns for disposal of clean or contaminated water, depletion of aquifers, drawing of contaminants to the site or dewatering induced settlements.

Jan 1, 2003

By M. T. Davisson

Pile compression load capacity prediction methods are divided into four categories for purposes of discussing their reliability compared to static load test results. The categories considered are: 1) static analysis, 2) driving formulas, 3) wave equation analysis, and 4) dynamic measurement and analysis. It is concluded that any method of static analysis that works for the geological deposit in question may be satisfactory. However, any given method can be quite wrong when applied to other deposits of soil that are different in terms of their engineering and geological characteristics. Dynamic formulas are found to be theoretically unjustifiable. The ready availability of the wave equation analysis for microcomputers eliminates the need to utilize dynamic formulas. The wave equation analysis is found to be the best analytical method for making predictions both for design and for construction control. Dynamic methods of measurement and analysis are found useful, but have limitations that have caused troubles on many projects. Two case histories are presented that show the limitations of dynamic measurement and analysis, and of the wave equation analysis. Soil deposits exist that defeat both the wave equation and dynamic measurement techniques; static load tests are currently the only method of proving the load capacity of piles in such soils.

Jan 1, 1991

By Roger A. Archabal, Omar A. Conte, Gustavo Langoni

This international case study focuses on the rigorous geotechnical interaction and results of a soil improvement program utilized to mitigate consolidation settlements of over 1.5 m [5.0 ft]. The extreme settlement results from very deep, nearly normally consolidated clay and the required high floor loading of a new Logistics Park near Bogota, Colombia. The general subsurface conditions consist of very soft clay extending to depths beyond the 50 m [164.0 ft] explored. A required 1.2 m [3.9 ft] thick fill combined with high floor loads resulted in an applied areal load of approximately 7 ton/m2 [1300 psf] (equivalent to about 4.5m [15.0 ft] of fill). Langan recommended performing a test section to validate the initial consolidation settlement calculations and evaluate possible optimization of the prefabricated vertical drain (PVD) spacing and length. The test section sizing was designed to accurately represent the stresses at depth of the future structures. Extreme settlements of over 1.5 m [5.0 ft] in the center and large differential settlements of over 0.6 m [2.0 ft] were measured between the center and corners of the test section over a relatively short test time. Discussion on the methodology, instrumentation, measured results and future optimization are presented. The recommended soil improvement varied from the standard approaches typically utilized in the area. PROJECT LOCATION AND DESCRIPTION The project site is immediately north-northwest of the city of Bogota in the Bogota Valley. The site is bordered with, and has historically been, farming land bordered to the south by the El Rosal-Bogotá highway. The overall site encompasses about 570,000 m2 [141.0 acres] of gross area and about 484,000 m2 [119.6 acres] of net buildable area. The warehouse complex will consist of 10 very large warehouses with footprints ranging from about 15,000 m2 [3.7 acres] to 30,000 m2 [7.4 acres]. The total building area is about 210,000 m2 [51.9 acres] with most of the remaining areas being paved principal drives, truck parking or administrative parking. The topography of the site is relatively flat and close to final grade in roadway areas. However, the warehouse floors will be raised about 1.2 m [3.9 ft] (equivalent to about 2 t/m2 [370 psf] considering engineered fill) to allow for truck docking. In addition, the design floor loads are heavy and estimated to be up to 5 t/m2 [930 psf] and equivalent to about 2.5m [8.2 ft] of fill. Geotechnical conditions at the site are very weak at depths of 50 meters [165 ft] or more, with soft compressible clays comprising the majority of the soil profile. The Bogota Valley is composed in some areas of very deep alluvial deposits. These deposits have been classified as an important challenge and limitation to the development of high/heavy structures such as the project in question for many years (Orozco, 2006). Soft clay deposits have been encountered even beyond depths of 100 meters [328 ft] in some regions of the Bogota Valley (Sanz, 1994). Extreme settlements can be expected if extensive and high permanent loads (above preconsolidation stress levels) are supported in these thick alluvial deposits.

Jan 1, 2018

By Luca de Sanctis

The analysis of piled raft foundations in layered soils may be performed by 3D finite elements or by approximate procedures. Among the latter, the code NAPRA (Russo, 1998) is based on the method of the interaction factors and accounts for soil layering by the so called Steinbrenner approximation. A comparison between the results of 3D FEM and NAPRA for some reference layered soil profiles shows that the approximation is fully acceptable for engineering purposes, provided the stiffness of the single pile is properly selected. The interest of the conclusion lies in the fact that the amount of work needed to model a practical problem by NAPRA is but a fraction of that needed by FEM modelling.

Jan 1, 2002

By Aminul Islam, Vinay M. Kumar

"About 100 Hectares of land reclamation over the very soft to soft marine clay at Uran Creek in Maharashtra is planned. The depth of marine clay varies from 10m to 24m as observed from the geotechnical investigation. The marine clay was treated with Pre-fabricated Vertical Drains (PVD’s) installed from the elevation of +5.5mCD (chart Datum) and preload/placement of surcharge. A Settlement of soft soil mud under the reclamation was monitored using magnetic extensometer (M) and ground settlement maker (S2). These instruments are installed after constructing working platform at around +5.5m CD. Based on the field instrumentation data, the consolidation parameters were adjusted to match the theoretical and actual settlement plot. The author called this approach as “Back analysis method”. The objective of this paper is to present a case study of instrumented preloading treatment for a thick marine clay deposit. The degree of consolidation in clay strata was determined from magnetic extensometer and ground settlement marker data. Authors also determined degree of consolidation as Asaoka method, Hyperbolic method and Back analysis method and compared the results.INTRODUCTIONExpansion of Container terminal with port buildings, rail container depot, roads and utility buildings at Jawaharlal Nehru Port Trust (JNPT) is planned over a reclaimed land of 100 hectares. Uran creek predominately consists of the estuarine deposit of very soft to soft marine clay. They are characterized by low shear strength, very low bearing capacity and exhibit large settlement when subjected to loading. The additional load causes the significant magnitude of consolidation settlement over a considerable period of time. Thus for development projects on top of soft soil, the postconstruction settlement would be of primary concern.To accelerate the consolidation pre-fabricated vertical drains (PVD) were used. Pre-loading procedure was adopted to minimize the post construction total and differential settlements. PVD’s were installed at 1.0m and 1.2m c/c triangular pattern. Locally available borrow material is used as a reclamation material. The reclamation material has been placed over the existing sea bed level by land based method/end tipping method and created the working platform. The level of working platform is decided based on the tide data and it has been selected such that work should be affected during highest high water level. The PVD has been installed from the working platform and subsequently all the field instruments have been installed from the same level. Five different types of field instruments are installed to monitor ground improvement works."

Jan 1, 2017

By Mario Aiezza

This paper outlines the results of a relationship developed during the design and construction of the foundations for the Gallery Towers project in Melbourne. Both the builder and the piling contractor were determined to arrive at a satisfactory foundation solution to the problems encountered at the site. The scope of piling work was to provide load-bearing piles under the building columns, some of which were located within a retention system that also required a piling solution. Geological conditions were variable and challenging. The site area was small and located adjacent to the National Arts Centre in the developed Southbank area, a high density office area. This presented logistical problems in limiting construction traffic on site and also demanding minimal noise and vibration emanating from piling activities. The piling contractor, Vibro-Pile, and the builder, Walter Construction Group, faced the challenges presented with a refreshing cooperative attitude that was beneficial to both companies. Commercial issues rising from design and construction problems were first put apart in order to allow the respective technical department of each company to work with minimum constraints to achieve the most cost effective solution. In the process usual adversarial attitudes resulting in loss of time and money was avoided. A number of issues were addressed successfully at minimum cost and time during this contract. Despite the difficulties encountered, the job was completed on time and with negligible claims for extras, resulting in the development of a strong mutual respect between both companies.

Jan 1, 2002