33 results found
Aliyu MM, Shang J, Murphy W, et al., 2019, Assessing the uniaxial compressive strength of extremely hard cryptocrystalline flint, International Journal of Rock Mechanics and Mining Sciences, Vol: 113, Pages: 310-321, ISSN: 1365-1609
Cryptocrystalline flint is an extremely hard siliceous rock that is found in chalk formations. The chalk is frequently a prefered rock type, which in recent decades is often used as a host for underground rock caverns and tunnels in Europe and North America. A reliable estimation of the uniaxial compressive strength (UCS) of the extremely strong flint, with an average UCS of about 600 MPa will provide guidance for a proper engineering design, where flint is encountered, thereby avoiding project progress delay, litigation as well as economic consequences. Conventional UCS measurement using core samples is cumbersome for flint due to the extreme strength and hardness of the rock, for which the core sample preparation process is often extremely difficult. In this study, the UCS prediction models of flints collected from the North-West Europe were developed and the validity of the developed models was investigated. A series of laboratory index tests (comprising the three-point-bending, point load, ultrasonic velocity, density, Shore hardness and Cerchar Abrasivity tests) were perfomed. The index test results were correlated with the UCS values previously determined in the laboratory using both cylindrical and cuboidal specimens to develop the UCS prediction models. Regression analysis of the UCS and the index test results was then performed to evaluate for any potential correlations that can be applied to estimate the UCS of the cryptocrystalline flint. Intensive validity and comparison studies were performed to assess the performance of the proposed UCS prediction models. This study showed that UCS of the tested flint is linearly correlated with its point load strength index, tensile strength and compressional velocity, and is parabolically correlated with its density. The present study also demonstrated that only a couple of the previously developed empirical UCS models for estimating UCS are suitable for flint, which should be used with care.
Lawrence JA, Spence R, Mortimore RN, et al., 2018, Coastal cliff rock mass weakening of chalk and the impact of salt water, Proceedings of the Institution of Civil Engineers - Geotechnical Engineering, Vol: 171, Pages: 545-555, ISSN: 1353-2618
The relationship between salt water and the strength of Chalk forming the coastal cliffs of northwest Europe was investigated. Uniaxial compressive strength (UCS) tests on core samples from three horizontal boreholes drilled at the base of Chalk cliffs in East Sussex, UK, showed the weakest Chalk to be near the cliff face. The UCS nearly doubled over the length of the 9 m deep boreholes. The UCS results were close to values expected for Chalk of this intact dry density for samples farthest from the cliff face. High chloride concentrations (salt water) of up to 69 000 mg/l were found to be associated with the lowest UCS values closest to the cliff face. Lower chloride concentrations, with values of 1850 mg/l or less and often with a non-marine origin, were found in the stronger core samples. It can be concluded that the Chalk coastal cliffs in the areas tested became weaker towards the cliff face. This can, in part, be linked to salt water weakening although it is likely that other factors are also contributing to this phenomenon.
Lawrence JA, Preene M, Lawrence U, et al., 2018, Engineering in Chalk, Publisher: ICE Publishing, ISBN: 978-07277-6407-2
Lawrence J, mortimore R, Thrower A, Macro and micro fabrics in chalk identified using the Bushinsky Oil Technique: an updated method and new applications for an old experimental technique, Engineering in Chalk
Lawrence J, hussein D, Rashid F, et al., Developing pore size distribution models in heterogeneous carbonates using especially nuclear magnetic resonance, Engineering in Chalk
Lawrence J, Agar S, Ghail R, et al., 2018, PSInSAR remote sensing observations of deformation behaviour at Salisbury Plain, UK, Engineering in Chalk, Pages: 269-274
PSInSAR is a radar remote sensing approach that offers measurements of ground deformation over large areas at sub-mm precision. The technique has significant potential for granting insight into ongoing geological processes. Data recovery in rural areas is challenging due to the highly inconsistent radar scattering behaviour exhibited by vegetated ground, and thus a rural area of the UK – Salisbury Plain - was used as a case study to examine the challenges and potential for PSInSAR techniques in rural areas. Results showed regional uplift of clay formations relative to the Chalk, which was attributed to clay shrink-swell correlated with seasonal increases in groundwater levels.
Hadlow NW, Lawrence JA, Mortimore RN, 2018, Evaluation and prediction of anticipated depths of weathering (engineering rockhead) as a function of geomorphology in areas of chalk outcrop in southern England and northern France, Pages: 711-720
© 2018 Engineering in Chalk - Proceedings of the Chalk 2018 Conference. All rights reserved. Conceptual models of weathering in areas of chalk outcrop in southern England indicate that the depth of weathering and engineering rockhead are variable with respect to geomorphology. This variation is typically demonstrated by the transition from interfluve to valley with the depth of weathering changing as result of elevation and aspect. Valley axes are shown to have the deepest weathering, inter-fluves the shallowest and valley slopes a transitional depth with slope gradients on north-west facing slopes generally greater than southeast facing slopes. The main processes considered to have formed the weathering profiles in the Chalk of southern England are periglacial processes associated with seasonal freeze-thaw and mass movement in the last ice-age. In this study, analysis of historical site investigation data, including geophysical surveys, has allowed these conceptual models to be reviewed. This analysis has suggested that two physical transitions occur within the near-surface chalk rock mass that relate to geomorphology. The first, and deepest, transition is considered to represent an opening of discontinuities in the rock mass as a consequence of relaxation in the near surface due to unloading. The second transition is considered to represent an increase in discontinuity frequency in the rock mass due to formation of new discontinuities which progressively intensifies towards the surface. The base of the second transition is generally considered to be engineering rockhead for most engineering situations. Using the data reviewed, a model was developed to estimate the approximate position of these transitions based on relative ground surface elevation within a geomorphological domain. This model may be used to estimate the depth of engineering rockhead based on topographical data, such as a digital terrain model (DTM), in the absence of site investigation data fo
Asoms SG, Stavrou A, Lawrence JA, 2018, Developing a GIS based methodology for coastal chalk cliff retreat using multiple datasets, Pages: 369-374
© 2018 Engineering in Chalk - Proceedings of the Chalk 2018 Conference. All rights reserved. Topographical mapping survey data which covered a period from 1951 to 2000 was used as the main data set to develop a cliff recession analysis of the coastal cliffs at Birling Gap, East Sussex, UK. This a portion of the coast is dominated by the Seven Sisters chalk coastal cliffs and Birling Gap is characterized by the presence of a palaeo-valley which formed during the Devensian glaciation. The entire area is subject to high rates of erosion and frequently cliff collapses at all scales. Using a GIS platform, a database was created geo-referencing this detailed cartographic historical record. The cartographic information was translated into spatial linear elements within the GIS; each linear element defining the position of the cliff at a specific period. A spatial and statistical analysis of the georeferenced information provided a complete and comprehensive analysis of the shoreline recession, allowing spatial and temporal correlation of the coastal erosion occurring at this location. The cartographic information was then enhanced by using more recent data sets, mainly obtained by aerial photos, which allowed the analysis to be extended into the 21st century. This methodology was developed to demonstrate how different data sets can efficiently and effectively be combined to provide end users with a single referenceable tool to holistically investigate the processes, causes and impact of coastal erosion.
Aliyu MM, Murphy W, Lawrence JA, et al., 2018, Impact of tectonic faults on the morphology and mechanical properties of grey flints, Pages: 515-520
© 2018 Engineering in Chalk - Proceedings of the Chalk 2018 Conference. All rights reserved. Grey flints of different morphologies (tabular and nodular) located proximally and distally to large tectonic faults were investigated. Different positions to tectonic faults were considered to examine the influence of geological structures on mechanical properties of flints. Different morphologies were considered to investigate the variation in mechanical properties of flints with morphology. Uniaxial compressive strength, point load strength, tensile strength, density and deformability of grey flints were tested. The results show grey flints are stronger, denser and more rigid than similar flints from zones of tectonic disturbance and faulting, but do not show any trend between flint morphology and mechanical properties. Understanding field variables such as the influence of proximity to tectonic faults and the variation in mechanical properties of flint may provide important input for the successful design of engineering projects and the behaviour of chalk oil reserviours.
Asoni SG, Stavrou A, Lawrence JA, 2018, Erosion of the chalk coastal cliffs at Birling Gap, Sussex, UK. Correlation between rate of coastal retreat, geotechnical rocks properties and precipitation, Pages: 361-367
© 2018 Engineering in Chalk - Proceedings of the Chalk 2018 Conference. All rights reserved. Birling Gap forms part of the Seven Sister cliffs, East Sussex, UK. Geotechnically the area is characterized by the presence of a Devensian paleovalley developed in a shallow syncline within the Seaford Chalk Formation. It is a dynamic coast line which is subject to continual erosion. A detailed survey has been undertaken along the coast of Birling Gap from 1950 to 2000. Using these data, the spatial information is translated into geospatial elements of an ArcGIS platform. The geo-referencing process defines the position of the cliff in a specific period. Aerial photos and most recent mapping survey are used to extend and complete the temporal analysis to the 21 st century. The outputs show that mean rate of coast retreat is 0.54 m/y and circa 30 m of coast has been lost in the last 60 years. Analysing the pluviometry data, it is possible to establish a relation between peak precipitation and high rates of coastal retreat. Higher rates of retreat are measured on the central portion of the studied area which is characterized by the deeply weathered paleovalley, which differs geotechnically from the surrounding more competent, less weathered chalk. The study shows how an accurate mapping survey translated into a GIS database can be a useful tool to understand the temporal geodynamic and hydrodynamic evolution of coastal environments. This work quantifies rapid erosion along this part of our chalk coastline and identifies that erosion is higher during periods of prolonged increased precipitation.
Mider G, Lawrence JA, 2018, Anisotropic permeability of chalk, Pages: 481-487
© 2018 Engineering in Chalk - Proceedings of the Chalk 2018 Conference. All rights reserved. The consolidation history of chalk denotes that it has been subjected to different horizontal and vertical stresses throughout its geological history. A testing programme was developed to investigate whether this would mean that chalk exhibits anisotropic permeability. Three Southern Province Chalk formations in south east England were tested; West Melbury Marly Chalk, Seaford Chalk and Newhaven Chalk formations. All the specimens were collected in the field, orientations were recorded before the samples were cut and prepared for laboratory testing. The laboratory testing programme identified small anisotropics in permeability measurements in Seaford and Newhaven Chalk formations, and anisotropy in unconfined compressive strength measurements. Anisotropic permeability in the West Melbury Marly Chalk Formation is unresolved due to heterogeneity of the samples collected from the formation. All tested samples also had index properties measured, and they have also been presented in the paper. It can be concluded that vertical samples in the Seaford and Newhaven Chalk formations are more permeable and weaker than horizontally drilled samples.
, 2018, ENGINEERING IN CHALK., ISBN: 9780727764072
Hussein D, Collier R, Lawrence JA, et al., 2017, Stratigraphic correlation and paleoenvironmental analysis of the hydrocarbon-bearing Early Miocene Euphrates and Jeribe formations in the Zagros folded-thrust belt, Arabian Journal of Geosciences, Vol: 10, ISSN: 1866-7538
The Lower Miocene Euphrates and Jeribe formations are considered as the main targets of the Tertiary petroleum system in the western part of the Zagros Basin. The formations consist of carbonates with some evaporate intercalations of the Dhiban Formation. This study utilized data from a field investigation including newly described outcrop sections and newly discovered productive oil fields within the Kirkuk embayment zone of the Zagros fold and thrust belt such as Sarqala and Kurdamir wells. This work is the first to show a stratigraphic correlation and paleoenvironmental interpretation by investigating both well data and new outcrop data. Three depositional environments were identified, (1) an inner and outer ramp belts environment, (2) shoal environment, and (3) restricted lagoon environment. Within these 3 environments, 12 microfacies were identified, based on the distribution of fauna mainly benthonic foraminifera, rock textures, and sedimentary structures. The inferred shallow water depths and variable salinities in both the Euphrates Formation and Jeribe Formation carbonates are consistent with deposition on the inner ramp (restricted lagoon and shoal) environments. Those found in the Euphrates Formation constrained the depositional environment to the restricted lagoon and shoal environment, while the microfacies in the Jeribe Formation provided evidence for an inner ramp and middle to outer ramp belt environments. This study represents the first detailed research that focuses on the stratigraphic correlation and changes in carbonate facies with the main aim to provide a wider understanding of stratigraphy of these carbonate reservoirs throughout the northern part of Iraq.
Rashid F, Glover PWJ, Lorinczi P, et al., 2017, Microstructural controls on reservoir quality in tight oil carbonate reservoir rocks, Journal of Petroleum Science and Engineering, Vol: 156, Pages: 814-826, ISSN: 0920-4105
In carbonate reservoir rocks the complex interaction between the petrophysical properties corresponds to the various depositional microstructures which are modified by various diagenetic process es that ultimately define the reservoir quality, and pose challenges to the prediction of permeability. The permeability heterogeneity in the carbonate oil reservoirs of northern Iraq varies widely and is thought to be controlled by a number of different factors. In this work, controls of matrix permeability for the Cretaceous Kometan formation selected from five oil fields in Kirkuk embayment zone have been investigated. Helium porosity, helium pulse decay permeability, brine permeability, Nuclear Magnetic Resonance (NMR), Mercury Injection Capillary pressure (MICP), Scanning Electronic Microscopy (SEM), X-Ray diffraction (XRD), and photomicrography of thin section have been used to investigate the effect of microstructure on the variation of permeability in the Kometan Formation. The formation has porosities and permeabilities which range from 0.5 ± 0.5% to 29 ± 0.5% and from 0.65 ± 0.08 μD to 700 ± 0.08 μD respectively. Three types of pore systems have been investigated using pore type, pore size and pore-throat size as characterizing parameters. We have recognized three microstructural types: (i) matrix composed of nano-intercrystalline pores (pore diameter d p smaller than 1 μm and a nanoporous pore-throat size), (ii) matrix composed of micro-intercrystalline pores (1 < d p < 10 μm with a corresponding micron-scale pore-throat distribution), and (iii) meso-intragranular and moldic pores (d p > 10 μm) also with microporous pore-throat radii. The nano-intercrystalline pore system is common across northern Iraq and represents the effective pore system type in the reservoirs of the Kirkuk embayment zone. For these tight carbonate reservoirs, the mineralogy, especially of quartz and clay minerals (illite and smectite
The petrographic and mechanical properties of flints from the Burnham (North Landing, Yorkshire, UK), Seaford (East Sussex, UK, and Dieppe, France), and Lewes Nodular (Mesnil-Val, France) Chalk formations have been investigated. Microtexture and mineral composition of flints are studied to understand how the geological and petrophysical properties of the flint affect drilling responses to the rock and investigate any spatial variation. The flints are categorized based on physical observation into white crust and light brownish grey, dark brownish grey and grey flints. Scanning electron microscopy shows textural variation in the classes. The white crust, light brownish grey, brownish grey and grey flints from the Burnham Chalk Formation from North Landing contain more calcite and have coarser, more poorly cemented silica spherules in comparison with similar classes of flint from the Seaford and Lewes Chalk formations from the Anglo-Paris Basin. In these latter flints, the structure is dominated by massive quartz cement with trace calcite independent of location. Strength tests show that the grey flints from North Landing are weaker than equivalents from the Anglo-Paris Basin. It is suggested that variation in engineering properties between grey and the dark brownish grey flints is caused by mineral composition, microtexture, structure and the local or site geology of flint materials.
Aliyu MM, Murphy W, Collier R, et al., 2015, Classification of flints for drill wear potential, Future Developments of Rock Mechanics. EUROCK2015 & 64th Geomechanics Colloquium, Publisher: Austrian Society for Geomechanics, Pages: 309-314
The assessment of abrasiveness and hardness of rocks have been extensively coveredby previous researchers, with little attention to flints, which were only described as highly abrasive.However, analysis of flints has shown that abrasivity of flints varies. These parameters areimportant inputs for the prediction of drill bit wear rate and design of various parts ofdrilling/tunneling/mining equipment. In this paper, a classification of flints (sampled from theEnglish, French and Danish Chalk) which correlates with the abrasivity and hardness of flints isproposed. The results showed lighter/grey flints (with more calcite) have lower potential to causedrill bit wear as indicated by hardness and geotechnical wear indices than dark flints. This tends tosuggest that even small variations in the carbonate content results in significant variation inabrasivity and that colour can be used as an indication of the potential of flints to cause tool wear.
Stavrou A, Murphy W, Lawrence JA, 2015, Evaluating the influence of block size in cable bolt performance, Future Developments of Rock Mechanics. EUROCK2015 & 64th Geomechanics Colloquium, Publisher: Austrian Society for Geomechanics, Pages: 859-864
Rashid F, Glover PWJ, Lorinczi P, et al., 2015, Permeability prediction in tight carbonate rocks using capillary pressure measurements, MARINE AND PETROLEUM GEOLOGY, Vol: 68, Pages: 536-550, ISSN: 0264-8172
Rashid F, Glover PWJ, Lorinczi P, et al., 2015, Porosity and permeability of tight carbonate reservoir rocks in the north of Iraq, Journal of Petroleum Science and Engineering, Vol: 133, Pages: 147-161, ISSN: 0920-4105
© 2015 Elsevier B.V. The distribution of reservoir quality in tight carbonates depends primarily upon how diagenetic processes have modified the rock microstructure, leading to significant heterogeneity and anisotropy. The size and connectivity of the pore network may be enhanced by dissolution or reduced by cementation and compaction. In this paper we have examined the factors which affect the distribution of porosity, permeability and reservoir quality in the Turonian-Campanian Kometan Formation, which is a prospective low permeability carbonate reservoir rock in northern Iraq. Our data includes regional stratigraphy, outcrop sections, well logs and core material from 8 wells as well as a large suite of laboratory petrophysical measurements. These data have allowed us to classify the Kometan Formation into three lithological units, two microfacies and three petrofacies. Petrofacies A is characterized by dense and compacted and cemented wackstone/packstone with nanometer size intercrystalline pores and stylolites and presents a poor reservoir quality (porosity range 0.005±0.01 to 0.099±0.01, permeability range 65nD-51μD). Occasional open fractures in Petrofacies A improve reservoir quality resulting in a 2-3 order of magnitude increase in permeability (up to 9.75mD). Petrofacies B is a dissolved wackstone/packstone that contains moldic and vuggy pores (porosity range 0.197±0.01 to 0.293±0.01; permeability range 0.087-4.1mD), with both presenting good reservoir quality, while Petrofacies C is a carbonate mudstone that has undergone dissolution and possibly some dolomitization (porosity range 0.123±0.01 to 0.255±0.01; permeability range 0.065-5mD). All three petrofacies can be distinguished from wireline log data using porosity and NMR measurements. A poroperm plot of all of the data is fitted by a power law of the form k(mD)=aϕ<sup>b</sup> with a=28.044 and b=2.6504 with coefficient of determination, R<
Lawrence JA, Mortimore RN, 2015, Reply to comment on: Lawrence, JA, Mortimore, RN, Stone, KJ, and Busby, JP, 2013. Sea saltwater weakening of chalk and the impact on cliff instability. Geomorphology 191, 14-22, GEOMORPHOLOGY, Vol: 231, Pages: 393-394, ISSN: 0169-555X
Ahmad F, Murphy W, Lawrence JA, et al., Strength Mobilisation of Rock Masses in Relation to Deep Seated Landslide, Geophysical Research Abstracts 17, EGU2015, 8151
Lawrence JA, Mortimore RN, Stone KJ, et al., 2013, Sea saltwater weakening of chalk and the impact on cliff instability, GEOMORPHOLOGY, Vol: 191, Pages: 14-22, ISSN: 0169-555X
Castedo R, Murphy W, Lawrence J, et al., 2012, A new process-response coastal recession model of soft rock cliffs, GEOMORPHOLOGY, Vol: 177, Pages: 128-143, ISSN: 0169-555X
Lawrence JA, Soil and Rock Description in Engineering Practice, D. Norbury: Book review, International Journal of Rock Mechanics & Mining Sciences, Pages: 1381-1381
Stavrou A, Lawrence JA, Mortimore RN, et al., 2011, A geotechnical and GIS based method for evaluating risk exposition along coastal cliff environments: a case study of the chalk cliffs of southern England, NATURAL HAZARDS AND EARTH SYSTEM SCIENCES, Vol: 11, Pages: 2997-3011, ISSN: 1561-8633
Quinn JD, Rosser NJ, Murphy W, et al., 2010, Identifying the behavioural characteristics of clay cliffs using intensive monitoring and geotechnical numerical modelling, GEOMORPHOLOGY, Vol: 120, Pages: 107-122, ISSN: 0169-555X
Lawrence JA, Informing chalk cliff recession management decisions, Civil Engineering Year Book 2010, Pages: 17-18
Senfaute G, Duperret A, Lawrence JA, 2009, Micro-seismic precursory cracks prior to rock-fall on coastal chalk cliffs: a case study at Mesnil-Val, Normandie, NW France, NATURAL HAZARDS AND EARTH SYSTEM SCIENCES, Vol: 9, Pages: 1625-1641, ISSN: 1561-8633
Quinn JD, Murphy W, West LJ, et al., 2008, The use of terrestrial laser scanning, differential GPS surveying and panoramic photography to characterise the landslides and recession of the Holderness Coast, Yorkshire, England, Geo Edmonton 2008. 61st Canadian Geotechnical Conference and 9th Joint CSG/IAH-CNC Groundwater Conference, Publisher: Canadian Geotechnical Society, International Association of Hydrogeologists-CNC, Geotechnical Society of Edmonton, Pages: 411-418
Lawrence JA, Mortimore RN, Eade M, et al., 2007, Developing a strategy for coastal cliff monitoring and management, International Conference on Landslides and Climate Change, Publisher: TAYLOR & FRANCIS LTD, Pages: 81-+
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