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First International Conference on Frontiers in Shallow Subsurface Technology
- Conference date: 20 Jan 2010 - 22 Jan 2010
- Location: Delft, Netherlands
- Published: 20 January 2010
21 - 40 of 48 results
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Inverse analysis of a road embankment using the Ensemble Kalman Filter including heterogeneity of the soft soil
Authors A. Hommels, F. Molenkamp and A.W. HeeminkGeomechanical models are indispensable for reliable design of engineering structures and processes and hazard and risk evaluation. Model predictions are however far from perfect. Errors are introduced by fluctuations in the input or by poorly known parameters in the model. To overcome these problems an inverse modelling technique to incorporate measurements into the deterministic model to improve the model results can be implemented. This allows for observations of on-going processes to be used for enhancing the quality of subsequent model predictions. In geomechanics several examples of inverse modelling exist where the improved model of the system is obtained by minimizing the discrepancy between the observed values in the system and the modelled state of the system within a time interval. This requires the implementation of the adjoint model. Even with the use of the adjoint compilers that have become available recently, this is a tremendous programming effort for the existing geomechanical model system. The Ensemble Kalman filter has been implemented to overcome this problem. The Ensemble Kalman filter analyses the state of the subsurface each time data becomes available. The Random Finite Element Method is used to simulate the heterogeneity of the subsurface. Very promising results of a conceptual example, based on the construction of a road embankment on soft clay, are presented. The Ensemble Kalman filter is not only used for a straight forward identification of the elastic Young’s modulus E of the foundation below the embankment, but also incorporates the determination of several critical parameters of the inverse modelling process.
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On the enhancement of railways transitions zones behaviour through maintenance
Authors Bruno Coelho, Paul Hölscher, Frans B. J. Barends and Jeffrey PriestTransition zones between embankments and rigid structures (e.g. bridges, culverts and tunnels) often require additional maintenance to preserve track quality, which not only increases costs but also causes delays. In order to reduce the maintenance, a better understanding of the behaviour of these zones is required. To this end, a strategy was developed and implemented to undertake a detailed investigation, using both static and dynamic measurements, of a standard transition zone in the Netherlands, which was located on a typical Dutch soft soil.
In this paper the observed results, for both static and dynamic behaviour of the system, will be discussed, in addition the differences between the original design assumptions and the real behaviour for this particular structure will be highlighted.
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Green remediation by facilitating industrial water use and heat surplus in the Port of Rotterdam
Authors E. van Nieuwkerk, H. Rijnaarts, N. van Ras, B. Drijver and W. van HattemIn the Port of Rotterdam the long-term presence of various industrial activities has resulted in soil and groundwater contamination. This contamination is substantial, complex and is usually not limited to one particular site but affects (ground)water systems at a regional scale. This being the case, site-specific approaches are neither effective nor cost efficient. In these cases it is better to develop an integral approach at megasite level, in which risk management scenarios are combined and measures are prioritized. The natural resilience of the soil and groundwater system will help significantly in reducing the risk of contaminated groundwater, if managed properly. In the EU WELCOME project an integrated management strategy (IMS) has been developed and later on successfully applied at the Port of Rotterdam. The implementation has revealed that a significant cost-reduction of up to 40% can be achieved in comparison to a site by site remediation approach, if measures are considered following a risk based approach on megasite scale. Active remediation efforts will still be conducted within the framework of the Integrated Management Strategy in order to manage the risk of still present contaminations. Conventional remediation techniques need energy and produce CO2 which has raised doubts about the overall sustainability of these techniques. The introduction of green remediation approaches can significantly boost the sustainability of Area Management of Contamination. For megasites like the Port of Rotterdam the key to this ambition lies in the combination of several goals for energy and water. For the Port of Rotterdam it is possible to effectively combine industrial water use and the industrial heat surplus with the remediation of contaminated groundwater. By using the groundwater for cooling purposes and storing (part of) the heat surplus underground (Aquifer Thermal Energy Storage, or ATES), biological remediation can be stimulated under certain conditions. This will lead to both an improvement of the groundwater quality and a reduction of energy use and CO2 emissions.
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Sustainable synergies for the subsurface combining groundwater energy with remediation: an illustration with 2 cases
Authors H. Slenders, P. Dols, R. Verburg, M. van Tulder, H. van den Berg and J. SchreursIn the last decade the policy on largely contaminated areas in the Netherlands has moved to groundwater and risk management. Parallel to this development the application of Heat Cold Storage (HCS) in groundwater has increased significantly as a result of the shift to more sustainable energy sources. Currently there are about 1.000 systems, and this is expected to increase to 20.000 in 2025. HCS initiatives are often used in dynamic areas (inner cities) where groundwater contaminants are also found. In a strict interpretation the Dutch Soil Protection Law prohibits the additional movement of contaminants and therefore the application of HCS in or near contaminants. But higher environmental goals at a more holistic level are also regarded nowadays, and what used to be a bottleneck is regarded as a perfect opportunity to combine the remediation of contaminated areas with sustainable energy1. Sensible use of the subsoil can lead to profit, and can also be a perfect means to protect and improve soil and groundwater quality. HCS systems can be used to contain, control or sustainably remediate groundwater. In this abstract two different, real life approaches are illustrated for the combination and interactions of Heat Cold Storage and Remediation. They all illustrate the shift towards sustainable use of groundwater, a means of improving groundwater quality.
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Physical aspects of heat transport in porous media
Authors Frans B.J. Barends and Sanaz SaeidAt present the search for energy other than coal, oil or gas is popular and the exploitation of geothermal energy provides an interesting alternative. For the design of exploitation sites, numerical models are in use, which should be validated by field test and analytical solutions. In this paper different physical processes encountered in heat transport in porous media and validation by analytical tools are explored.
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Capacitive-coupled electric-field sensing for urban sub-surface mapping: motivations and practical challenges
Authors Kae Y. Foo, Philip R. Atkins, Andrew M. Thomas and Chris D.F. RogersGround penetrating radar (GPR) technology is increasingly deployed as the survey tool of choice for urban sub-surface mapping due to its relatively fast speed and minimal ground intrusion. However, there are several application scenarios that still pose difficulties for a GPR, for example in mapping an area with heavy clay or when presented with shallow plastic pipes. A capacitive-coupled electric-field sensing technique is herein considered for the non-intrusive detection of shallow non metallic targets. This technique relies upon detecting an electric field associated with the variation of current density as a result of changes in ground impedance. This paper briefly reviews the theoretical underpinning of the sensor system, followed by a proposal of system design with the aim of operating as an aid to existing GPR technology in urban subsurface mapping. The quality of received signal is measured in comparison with those obtained using ground electrodes. A discussion on the practical challenges associated with the application of this technique is presented, along with preliminary trial results.
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Low-frequency electrical properties of homogeneous and heterogeneous sand samples
Authors M. Kavian, E.C. Slob and W.A. MulderWe conducted a series of laboratory measurements of the electrical properties of samples of water-saturated, unconsolidated sand as a function of frequency, water saturation, and salinity. We employ the parallel-plate capacitor technique to measure the complex impedance for frequencies between 200 Hz and 3 MHz. We performed main drainage and secondary imbibition cycles for unconsolidated sand-saline water systems at atmospheric pressure and temperatures between 21°C and 22°C. We found hysteresis in the electric permittivity and resistivity, caused by the redistribution of the water and air phases. The hysteretic effect becomes more pronounced at higher concentrations of salt. Also we found that the sand grain size does not affect the permittivity of dry sand. For the saturated sand, the situation changes considerably and the coarser grain size leads to a larger polarization effect. An explanation of this phenomenon is that for the coarse-grain size sand, the capillary pressure is lower than for the fine-grain size sand, allowing the water molecules to respond more easily to the external electric field. The electric properties at all saturation levels were found to depend on both frequency and salinity of the pore fluid, implying that a description by an effectively homogeneous medium should incorporate these parameters.
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A prototype cell to study electrical and geo-mechanical properties of peaty soils
Authors M. Ponziani, S. Shirasagi, D.J.M. Ngan-Tillard, E.C. Slob and K. HellerThis paper presents a new prototype cell that can perform electrical and compression tests on peaty soils. First tests on peat samples saturated with water at different salinities are presented. These data allowed comparing two models for inorganic sediments and peat in the reliable frequency range determined from calibration with distilled and saline water.
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Improving TDR for use with fine-grained soils
Authors A.M. Thomas, G. Curioni, K.Y. Foo, P.R. Atkins, C.D.F. Rogers and D.N. ChapmanTime-Domain Reflectometry (TDR) provides a robust and widely used method for the monitoring and characterisation of soils using user-friendly cable testers. However, the simplicity of common TDR practice, often utilizing only measurements of reflection distances for electromagnetic signals in probes, causes a number of difficulties when applied to fine-grained soils, largely because they can be electromagnetically dispersive: that is their dielectric 'constants' vary with frequency. This paper therefore considers two ways in which TDR data can be made to greater use in geotechnical disciplines: supplementing TDR with frequency-domain data, and addressing the issues of standardisation and data sharing.
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Investigation of enhanced mixing of a tracer in a porous medium using Electrical Resistance Tomography
Authors S. Korteland, T.J. Heimovaara and C. van BeekElectrical resistance tomography (ERT) is a method used to construct images of the electrical conductivity inside a domain from electrical potential measurements at the boundaries. In this research, ERT is used to construct images of the three-dimensional solute concentration distribution in a laboratory experiment. This article focuses on the development and testing of the ERT measurement system that will be used for the visualization of the mixing of a saline tracer.
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Use of olivine as a liming material in agriculture to decrease CO2 emissions
More LessThis paper investigates the potential of using forsterite olivine as an alternative for carbonate-containing limes in agriculture. The use of carbonate containing limes contributes to the anthropogenic CO2 emissions. Additional to replacement of agricultural lime, it may also increase the pH of soil and therefore the flux of bicarbonate from soil to the sea. Soil has been incubated using various amounts of olivine flour or lime in a relative acidic soil during eight months. The results show that during this period the effect of olivine on the soil pH is very small compared to lime. Compared to lime it is necessary to use approximately 35 times more olivine to get the same pH increase. Assuming similar costs for olivine and lime it is uneconomical to use olivine to replace lime. Currently also the Dutch Fertilisers Act does not allow olivine as a fertilizer due to the high amount of nickel compared to the neutralizing value.
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Biodegradation of BTEX under varying soil moisture and temperature conditions
Authors Brijesh K. Yadav, S. Majid Hassanizadeh and Pieter J. KleingeldContamination of soils due to the release of hydrocarbons, including petroleum products containing BTEX, is a major public health concern. Remediation of these polluted soils is needed to eliminate risk to human and to the environment. Biological treatment of these organic contaminated soils is receiving increasing interests and where applicable, can serve as a cost-effective soil remediation alternative. The effective implementation of this eco-friendly remediation technology requires a thorough insight of contaminants fate and transport processes under varying environmental conditions associated to a target site. Among several environmental factors, soil moisture content and soil temperature variation are important environmental factors for controlling the biodegradation of BTEX pollutants. Therefore, this study aims to investigate the complex soil-water-BTEX-atmospheric continuum processes during bioremediation under varying soil moisture and temperature conditions. To achieve this, a series of in-situ experiments under controlled conditions are planned for two sandy soils (with and without organic matter) containing dissolved toluene for different temperature and moisture content varying from residual to saturated condition. The results of these lab experiments can be used for predicting the process of BTEX degradation in variably saturated soils and will be relevant to fields such as bioremediation.
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Monitoring redox processes with spectral induced polarization in a stimulated bioremediation experiment
Authors Adrian Flores-Orozco, Kenneth H. Williams and Andreas KemnaMeasurements of spectral induced polarization (SIP) data were performed during a biostimulation experiment consisting of electron donor amendment. The implementation of an appropriate error model for the phase data within a complex resistivity inversion algorithm provided images free of artifacts, exhibiting phase anomalies well correlated with spatiotemporal changes in geochemical conditions resulting from stimulated subsurface microbial activity.
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Biodegradation of organic compounds in unsaturated soil: role in reducing risk from vapor intrusion
Authors S. Picone, T. Grotenhuis, J. Valstar, P. van Gaans and H. RijnaartsEmissions of volatile contaminants from groundwater sources to indoor air, represent a critical risk driving process in urban environments with shallow groundwater. Risks are normally evaluated through risk assessment models. There is however ample evidence from field measurements of indoor air concentrations that current model predictions generally provide a one to three orders of magnitude overestimation. Biodegradation of organic compounds in the unsaturated zone is a process that potentially interrupts exposure to humans as the final receptor, but so far knowledge is lacking about the precise parameters controlling biodegradation. Here we present results from model simulations researching the role of biodegradation. The model simulations use the finite difference numerical model STOMP. It simulates the flow of the gas and water phases and the diffusive and advective transport of solutes in both phases. The model simulates vertical transport through a soil column towards a crawl space in a shallow groundwater area, as well as air exchange in the crawl space. An oxygen dependent biodegradation mechanism is incorporated in the model, and different scenarios, neglecting or including biodegradation are compared.
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Biostimulated ground improvement
More LessRecently several in situ techniques are being developed to change the mechanical properties of soils by stimulating biochemical processes. A procedure named Biogrout is developed to increase strength and stiffness of unconsolidated sands, based on microbial-induced carbonate precipitation. Recently, this development resulted in a field scale experiment in which 40m3 of sand was cemented within 12 days, reaching average unconfined compressive strengths of 2 MPa with limited reduction in permeability. Pilot projects are in preparation. In order to optimize this process, the use of waste streams as substrate for biocementation has been investigated.
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Quantitative Integration of high-resolution hydrogeophysical data Through Monte-Carlo-type Conditional Simulations
Authors Klaus Holliger, Bapiste Dafflon and James D. IrvingGeophysical techniques can help to bridge the inherent gap with regard to spatial resolution and the range of coverage that plagues classical hydrological methods. This has lead to the emergence of the new and rapidly growing field of hydrogeophysics. Given the differing sensitivities of various geophysical techniques to hydrologically relevant parameters and their inherent trade-off between resolution and range the fundamental usefulness of multi-method hydrogeophysical surveys for reducing uncertainties in data analysis and interpretation is widely accepted. A major challenge arising from such endeavors is the quantitative integration of the resulting vast and diverse database in order to obtain a unified model of the probed subsurface region that is internally consistent with all available data. To address this problem, we have developed a strategy towards hydrogeophysical data integration based on Monte-Carlo-type conditional stochastic simulation that we consider to be particularly suitable for local-scale studies characterized by high-resolution and high-quality datasets. Monte-Carlo-based optimization techniques are flexible and versatile, allow for accounting for a wide variety of data and constraints of differing resolution and hardness and thus have the potential of providing, in a geostatistical sense, highly detailed and realistic models of the pertinent target parameter distributions. Compared to more conventional approaches of this kind, our approach provides significant advancements in the way that the larger-scale deterministic information resolved by the hydrogeophysical data can be accounted for, which represents an inherently problematic, and as of yet unresolved, aspect of Monte-Carlo-type conditional simulation techniques. We present the results of applying our algorithm to the integration of porosity log and tomographic crosshole georadar data to generate stochastic realizations of the local-scale porosity structure. Our procedure is first tested on pertinent synthetic data and then applied to corresponding field data collected at the Boise Hydrogeophysical Research Site near Boise, Idaho, USA.
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Nanoseismic monitoring of extremely weak failure signals in unstable shallow subsurface cavities and validation of numerical stress predictions
Authors Michael Tsesarsky and Gilles H. Wust-BlochIncipient instabilities, which are presently developing within the chalk of ancient (ca. 1100 years old) bell-shaped caverns at the Bet Guvrin National Park (Israel), have been the aim of multiple investigations for more than a decade. An innovative and independent validation approach is presented here, whereby numerical predictions of material instabilities are compared with the spatial distribution of extremely weak (ML > -4.0) failure signals detected by nanoseismic monitoring. Our data show that it is indeed possible to detect a series of extremely weak spiky broad-band signals. Their characterization and location indicate that they are unequivocally generated by incipient brittle failure within the chalk material of the bell-shaped caves, thus verifying numerical predictions. Furthermore, our investigations suggest that numerical modelling is best used to guide nanoseismic monitoring, which, in turn, can quantify the spatio-temporal distribution of actual incipient failure.
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Scattered-surface wave imaging: from the lab to the field
Authors A. Kaslilar and X. CampmanScattered surface waves provide information about localized heterogeneity in the shallow subsurface. Several methods have been developed and are under development to characterize and locate shallow heterogeneity, like voids, tunnels or mine shafts. In this study we use an efficient inverse scattering approach based on an integral representation of the scattered wave field. At the hand of examples of this method applied to synthetic data, ultrasonic laboratory data and field data, we discuss advantages and limitations of our method. With an eye on possible applications in passive seismology and the increased use of non-uniform arrays in geotechnical engineering, we show that the method is not very sensitive to non-uniform acquisition geometries.
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Application of seismic interferometry to near-surface active S-wave data
Authors Deyan Draganov and Ranajit GhoseWe apply seismic interferometry to shallow-subsurface shear-wave data recorded using active sources. We cross-correlate the active data to obtain virtual shot gathers and virtual common-offset sections and compare the results to the active data.
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Ground deformation in the former coal mines in southern Limburg, The Netherlands, as observed by satellite radar interferometry
Authors Miguel Caro Cuenca and Ramon F. HanssenPersistent Scatterer Interferometry methodologies measure ground motion with, under the right circumstances, 1 mm/yr precision by using the scatterers that remain coherent over a series of radar acquisitions. In this study, we present the results of applying this technique to measure land deformation in South Limburg, the Netherlands. This area is of special interest because of its long coal mining history, which ceased almost completely during the seventies. After the collieries were abandoned the water drainage also stopped. As a consequence, the water started to recover to flow through the galleries produce in ground uplift. Thus, from PSI observations we estimated the total cumulative deformation in the area. We employed two data sets in this research that were acquired by the European satellites ERS1/2 and Envisat, spanning from 1993 to 2001 and from 2003 to 2008, respectively.
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