Site Investigation Information Research Articles

A least squares method for identification of unknown groundwater pollution source

Abstract The identification of unknown groundwater pollution sources is one of the most important premises in groundwater pollution prevention and remediation. In this paper, an exploratory application of a least squares method to identify the unknown groundwater pollution source is conducted. Supported by a small amount of observation data and the analytical solutions of the pollutant transport model, the initial concentration, the leakage location and the pollutant mass are identified by using the least squares method under a sand tank experiment and a gas station area. In the sand tank experiment, it is found that the fitting errors of three cross-sections are within 6%. In the gas station area, it is found that the results are nearly consistent with the site investigation information. The results indicate that the least squares method has considerable application values in the identification of groundwater pollution sources.

Design and Realization of Site Investigation System for Hydraulic Engineering Based on WeChat Enterprise Account

Based on the powerful open interface of WeChat enterprise account features, a site investigation system is proposed for management of hydraulic engineering projects. The implemented functions include integrated photographing, GPS based positioning and information submission from handheld mobile devices. By leveraging cloud computing and mobile internet technologies, all the site investigation information is collected by designers on the unified mobile terminal including smart phones, tablets, and laptops. The proposed system provides various services, such as batch uploading, geological position mapping, data query and data downloading of the investigated information of specific hydraulic engineering project. Moreover, high level functions are realized through high-precision location based service, synchronous saving, resource sharing and quick search. Our system outperforms and changes the traditional working mode of site investigation of hydraulic engineering projects, as well as improves the working efficiency and accuracy for data collection in the whole life of the project management.

Ethanol effects on the fate and transport of gasoline constituents in the UK

In the UK, use of ethanol in fuel as a fuel oxygenate/fuel supplement is currently limited but could rise in an effort to meet the requirements of the European “Biofuels” Directive. This Energy Institute study focussed on the risk that accidental releases of ethanol blended gasoline (EBG) (i.e. gasoline containing 10% or less of ethanol) could pose to UK groundwater resources. Ethanol is miscible and highly biodegradable. As a result it tends to be strongly attenuated in the unsaturated zone and in groundwater and so does not, in itself, pose a significant risk to groundwater resources. However, it may lead to increased persistence of other gasoline constituents, particularly through alteration of geochemical conditions as a result of intensive biodegradation activity.A semi-probabilistic modelling exercise was undertaken to better understand the risks that use of EBG could pose to UK groundwater resources. Site investigation information from over 500 filling stations was used in combination with GIS data to predict the proportion of potable water supply wells that could potentially be impacted by benzene and MtBE, and estimate the length of benzene and MtBE plumes with and without the use of ethanol in gasoline. The results show that the use of EBG is likely to have a negligible effect on MtBE plumes. Some increase in benzene plume length is predicted, most notably in fissured aquifers, but increases in plume length of greater than 30% are predicted to be rare. A corresponding slight increase in risk to licensed potable water supply wells from benzene was predicted with the use of EBG but the percentage of wells at risk was still predicted to be small (0.13%), and in the context of the conservatism within the modelling, it was concluded that widespread use of EBG is unlikely to cause an increased risk to UK water resources.

Nondestructive Assessment of Axial Load–Deflection Behavior of Drilled Shafts for a Suspension Bridge

The new Rio Cuarto Bridge, currently under construction in the Province of Cordoba, Argentina, consists of a 110-m long, cable-stayed main span with a prestressed concrete deck, steel pylons, and two 50-m–long side spans founded on groups of drilled shafts. The construction method, structural configuration of the superstructure, and post-tensioning sequence of the cables required a detailed characterization of the axial load behavior of the drilled shafts, both for the temporary support shafts and the foundation piers. Small-strain and working load level predictions were made during design, on the basis of conventional site investigation information and in situ geophysical testing. A series of nondestructive evaluations, coupled with nonlinear extrapolations calibrated to represent the measured small-strain range, were carried out in lieu of conventional verification of design predictions by means of more cumbersome large-strain testing. The testing program consisted on monitoring accelerations generated at the top of the shaft as a result of a small amplitude dynamic load measured by means of a dynamic force transducer. A nonlinear numerical model was then calibrated so as to reproduce the initial stiffness measured during the small-strain testing program to extrapolate the load-deflection curve into the service load range and thus define load-deflection curves of the shafts at each pier location up to service load levels. To obtain an experimental validation of the approach at the site, a conventional static load test, carried up to the service load level, was performed on a main pier shaft. Results showed a reasonable agreement between the nondestructive evaluation with nonlinear extrapolation, large-strain measurements, and design predictions for the main pier shafts, whereas some differences were observed between the design predictions and small-strain measurements at other locations, primarily as a result of as-built conditions unforeseen in the original design. Thus, the nondestructive testing program was instrumental in the verification of the as-built behavior of the shafts and allowed the development of load-deflection curves for the drilled shafts that accurately represented the behavior up to the service load level.

The ground: clients remain exposed to unnecessary risk

The ground remains the greatest source of risk to construction projects. In spite of a wealth of freely available information and guidance on the central importance of adequate site investigation in managing ground risk, many clients remain unnecessarily exposed to risk due to inadequate site investigation. The Federation of Piling Specialists undertook a comprehensive survey of geotechnical designers within its membership to evaluate the usefulness of site investigation information routinely provided to them. For nearly a third of all the piling and specialist geotechnical contracts surveyed, the site investigation information provided was poor, preventing optimisation of the foundation solution. The cost to clients arising out of poor site investigations far exceeds the savings that could be made by following good practice when investing in a site investigation. The survey indicates that good practice guidance is not being followed, resulting in investigations that are not adequately designed, specified or supervised.

Assessment of ground condition for a mass rail transit system in Singapore

Subsurface ground conditions will have a large influence on the design of underground structures such as tunnelling and deep excavation works. Adequate site investigation information is very useful in understanding the ground conditions. For the on-going mass rail transit system Circle Line Stage 2 - Contract 823 project, close to 90 exploratory boreholes were sunk to investigate the ground condition. The project involves the construction of three underground MRT stations and twin bored tunnels of approximately 2.5 km long. The objectives of the site investigation were to obtain a better appreciation of the ground subsurface profile along the route of the project and to ascertain design parameters. The results obtained from the site investigation are summarised in this paper. In this mass rapid transit project, the geological conditions of the site can be generalised as three main types: Fill, Kallang Formation and Old Alluvium Formation. Part of the geological profile of the site is shown in the figure. In this paper, the characteristics and engineering properties of Kallang Formation, especially Marine Clay Layer and Old alluvium Formation are discussed in detail. The Kallang Formation at the site consists of the following strata: (a) Marine clay layer, (b) Estuarine layer, (c) Silty/clayey sand layer (Fluvial sand F1); (d) Silty clay layer (Fluvial clay F2). The Marine Clay layer is the predominant layer within this formation found at the site with a maximum thickness of about 30 m. The silty clay (F2) is encountered mainly as an intermediate layer between the Upper and Lower Marine Clay layers as well as sub-layers found in ''buried valleys''. The estuarine layer and clayey sand (F1) are only encountered in a few boreholes and they are generally discontinuous laterally over the site. One of the most interesting findings from the site investigation were evidence of possible occurrence of some previous earthslips of Old Alluvium hillocks (shown as dotted area in figure) that had taken place during the initial stage of the Holocene period, i.e. before the deposition of the Lower Marine Clay layer, and are now buried between Kallang Formation soils. These earthslips had caused huge volume of soils displaced into adjacent valleys. Some of these ''buried valleys'' are now filled with intact Old Alluvium soils, which have undergone moderate degree of weathering albeit the soil fabric of the parent material remains relatively undisturbed. These earthslip layers are unusually much denser or stiffer than the Fluvial F1 and F2 soils that are commonly encountered within the Kallang Formation, as the measured SPT N-values could be greater than 30 blows. (A). Reprinted with permission from Elsevier. For the covering abstract see ITRD E124500.

Interactive Analysis of Spatial Subsurface Data Using GIS-Based Tool

Much of the spatial information that is an inherent part of geotechnical and geoenvironmental investigation programs has been underutilized due to the unavailability of analysis tools designed to take advantage of the spatial attributes of the information. This paper describes a system developed to provide a quantitative estimate of the adequacy of coordinate-based information used to make particular decisions, with particular emphasis on geotechnical and geoenvironmental site investigation information. The system was developed using a geographic information system (GIS) as a platform that was integrated with an existing commercial geostatistical software package to allow for more comprehensive analysis and optimization capabilities.

Spatial management of geotechnical data for site selection

A ground characterisation exercise was conducted in order to identify sites suitable for a blast furnace at the Redcar steelworks in northeast England. The purpose of this exercise, conducted some 20 years after the investigations were carried out and a decade after the steelworks had been constructed, was to develop techniques for managing spatial data using Geographical Information Systems (GIS) and geostatistics. Borehole details, from the factual site investigation reports, were entered into a database using a relational structure with linked files. The borehole location and lithology files were keyed in using codes for geological material, weathering grade, strength, borehole type and verification status. Laboratory and field test data were input by scanning tables in the ground investigation reports and processing the scanned images using optical character recognition software. The XBase programming language was used to execute graphing, GIS and geostatistics programs; thereby enabling repetitive tasks to be carried out by the computer. This both saved time and reduced errors and inconsistencies that could result from repeated manual execution of the same program. Some simple spatial operations could also be carried out entirely from within dBase, an example being the use of moving-window statistics employing rectangular windows aligned parallel to the axes of the coordinate system to study local stationarity. GIS have been found to offer an effective tool for analysing, querying and presenting spatial site investigation information. Geostatistical kriging and simulation techniques offer powerful spatial modelling tools for creating visualisations of the spatial variability of parameters measured at points during a ground investigation. The Redcar case history demonstrates how a database management system (DBMS) can be used to manipulate site investigation data as part of a modelling and interpretation exercise. DBase source code allows others to follow the same path or build upon the foundations herein.

Some issues associated with the preparation of a review of foundation conditions in Great Britain

Abstract The Department of the Environment commissioned Wimpey Environmental Limited, with the National House-Building Council, to undertake research to establish whether planners should take greater account of foundation conditions in preparing development plans and in considering planning applications. Existing information on factors such as compressible ground, shrinkage and swelling, saturated and loose granular deposits, frost susceptibility, groundwater conditions, durability of construction materials, and gas emissions, was reviewed. It was concluded that some of these factors may be material planning considerations whilst others are likely to remain only a matter for site development and Building Control. Soil survey digital data were used as a basis for 1:250 000 and 1:625 000 scale maps showing the general geographical extent of selected potential foundation problems in Great Britain. These, together with reports, provide information on ground conditions to planners and developers which will help to increase awareness of the problems and of the purposes, procedures and benefits of thorough site investigation. The preparation of the maps was guided by a database of site investigation information which should be of use to those who are undertaking more detailed consideration of sites.

A methodology for comparing soils for use in knowledge-based systems

Knowledge-based systems (KBSs) can be particularly useful in assisting with the interpretation of ground conditions from site investigation information, a major part of geotechnical design. This requires interpolating or extrapolating from observations at discrete points, such as boreholes, and involves considerable engineering (and geological) judgement. Such a system must be able to compare soils observed at two or more locations, in order to identify whether the soils observed belong to the same horizon. A scheme is put forward for calculating the similarity of two soils based on engineering soil descriptions. The descriptive terms are converted to quantitative representations. Similarity numbers can then be calculated from the quantitative parameters for a number of different factors such as soil type, structure, consistency and colour. These similarity numbers can then be combined using appropriate weighting factors to give an overall similarity number which represents a comparison based on all these factors. The approach used is procedural, but can be used as part of a KBS for interpreting ground conditions.

Times Beach: The Long Road to Recovery

Times Beach: The Long Road to Recovery