The engineering geology of the Nottingham area, UK

Nottingham was built near a crossing point on the River Trent in the East Midlands of England. Initially, the City developed on a low sandstone hill close to the north bank of the river, which provided a secure, well-drained location above the marshes that bordered the river. Geologically, Nottingham stands at the boundary between Palaeozoic rocks to the north and west, and Mesozoic and Cainozoic strata to the south and east. The area is underlain by coal-bearing Carboniferous Coal Measures, Permian dolomitic limestones, Permo-Triassic mudstones and weak sandstones, Jurassic clays and Quaternary glacial and alluvial deposits. Artificial deposits, resulting from the social, industrial and mineral extraction activities of the past cover the natural deposits over much of the area. This geological environment has underpinned the economic development of the area through the mining of coal (now largely ceased), oil extraction that was important during the Second World War, brickmaking from clays, alluvial sand and gravel extraction from the Trent Valley and gypsum extraction from the Permo-Triassic mudstones. The Permo-Triassic sandstone is a nationally important aquifer and has also been exploited at the surface and from shallow mines for sand. However, this history of the use and exploitation of mineral deposits has created a number of environmental problems including rising groundwater levels, abandoned mine shafts and mining subsidence, and, within the City itself, the occasional collapse of artificial cavities in the sandstone and contaminated land left by industrial activities. Natural constraints on development include gypsum dissolution, landslides, rockfalls, swell-shrink problems in Jurassic clays and flooding. Occasional minor earthquakes are attributed to movements due to coal mining or natural, deep geological structures. Thus, Nottingham’s geological context remains an important consideration when planning its future regeneration and development

The Importance of Creating Value in Seismic Design

Major earthquakes have resulted in devastating consequences in terms of human and economic loss. In almost all the earthquakes we observe the failure of structures, sometimes due to poor construction but also due to designers not identifying the specific geo-hazards (iIntensity of ground motion, faults, liquefaction, slopes etc) which affect these structures. In many cases these damages could have been avoided if the original design had correctly identified the geohazards at the site and incorporated the philosophy of performance based design. In this paper several examples will be presented where the different stages of risk assessment will be identified and possible solutions incorporated in the final design. The paper provides examples where existing studies and codes in certain countries may be storing up problems for the future.This paper also highlights some gaps in existing knowledge where more research is needed. Design examples will also cover the advantages of performing detailed design accounting for soil structure interaction effects. In many cases these will offer potential saving to the clients and thus provide value in seismic design. Examples are shown where structures which have accounted for the geohazards will be shown to perform satisfactorily during past earthquakes

A decision support system for ground improvement method selection

Abstract unavailable please refer to PD

Effect of internal erosion on the mechanical behaviour of soils

A thesis submitted to the Faculty of Engineering and Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the Degree of Doctor of Philosophy, 2017The effect of internal erosion on the mechanical behaviour of soils was investigated experimentally, using sodium chloride grains as an analogue for erodible soil grains. With this technique, the loss of controlled quantities of finer particles could be simulated under more realistic hydro-mechanical conditions than in previous research, but within practical experimental time scales. Two experimental programs were undertaken. The first looked at general changes in volume and shear strength using a large diameter oedometer adapted to perform a punch test following salt dissolution. The second program investigated particular changes in volume and shear strength following salt dissolution using an adapted direct shear box Previous studies have shown shear strength reductions following the loss of finer particles representing as little as 5 % of the total mass of the original soil. Findings here show shear strength can be largely unaffected if the erodible finer fraction (F) makes up less than a transition value (Ft) of approximately 10 – 15 % by mass of the original soil. This threshold represents F above which the coarser fabric is looser than at its minimum void ratio. As F increases further, finer particles increasingly hinder the coarser particles from achieving their densest packing, such that the coarser fabric remaining after finer particle loss is in a looser state than the original fabric, the remaining fabric reaching its maximum void ratio at a critical finer fraction (Fc) of approximately 25 – 35 %. For F < Fc, finer particle loss results in limited collapse of the coarser fabric and it was found that the state of this initial coarser fabric determines the shear behaviour of the soil following the loss of finer particles. The shear behaviour of initially dense specimens with F < Ft remained similar to that of a dense soil following finer particle loss, whereas shear behaviour of initially dense specimens with Ft < F < Fc approached that of a loose soil as F increased. Soils with higher internal filter ratios (D15c/D85f) were found to have higher values of Ft and Fc. Soils with F > Fc, settled and weakened significantly following finer particle loss, reflecting the load-bearing role finer particles play in this case. This load bearing nature of the finer particles in soils with F > Fc decreases the risk of internal erosion.CK201

Routes of the Uruk Expansion

The late fourth millennium B.C. of Mesopotamia is best known for an expansion of material culture from Southern Mesopotamia known as the Uruk Expansion or Uruk Phenomenon. The precise nature of this expansion remains unknown, but at its core it evidences unprecedented levels of interregional interaction whether in the form of colonies, trade diasporas, or otherwise. This thesis uses quantitative route analysis to examine the hollow ways across the North Jazira region of northern Mesopotamia before, during, and after the Uruk Expansion in the late fourth millennium B.C. to learn more about the phenomenon. To accomplish this, new methodologies were required. A bottom up method for reconstructing land cover was developed and the first velocity-based terrain coefficients were calculated to factor both land cover and slope into the route models. Additionally, the first quantitative method for directly comparing route models to preserved routes was developed to statistically assess the significance of three physical route choice variables: easiest, fastest, and shortest. First, it is statistically proven that, for the North Jazira, physical variables did not play a major role in route choice, highlighting the importance of cultural variables. Second, it is shown that the routes evidence the formation of polities starting in the late fourth millennium. Thirdly, it is demonstrated that the Uruk Expansion was a disruptive force that broke down previous east-west dynamics, spatially polarizing the population. Furthermore, when east-west movement resumes in the early third millennium B.C., the region remains divided in two distinct sub-regions. Finally, the poor performance of route models based on physical variables frequently used for predicting route locations has implications for the usefulness of this practice, particularly in areas with flatter terrain. What was important to other cultures cannot be assumed, but must be based on evidence from the cultures themselves

An investigation into the volume change characteristics of loess like soil in Mount Moorosi Village in Lesotho

The Mount Moorosi village is situated in the Senqu River Valley of southern Lesotho, within the Stormberg landform. The integrity and aesthetic appearance of nearly all the structures in this area are undermined by recurrent cracks. At present, no apparent institutionalised effort had been conducted to investigate the source of this problem. The crack patterns were associated with the possible volume change of the underlaying loess like soil. This soil has caused a disastrous failure to brittle civil engineering structures in various parts of the world. Its behaviour is attributed to sand and silt particles bonded by minerals, which become active upon saturation and induce hydrocollapse settlement. This study characterised the volume change properties of the underlaid deposits in Mount Moorosi. The research utilised representative samples from trial pits in the study region to perform laboratory experiments such as the Atterberg limits, wet sieving, sedimentation, free swell, x-ray diffraction, scanning electron microscope and slaking. The consolidated undrained tests and hydrocollapse potential were also determined from the GEOCOMP triaxial and Global Digital System oedometer, respectively. Results revealed that Mount Moorosi is generally underlaid by a more than 3 m thickness of low plasticity (9 to 17 %) silty-sandy loess. The material had significant warping (up to 27 mm) in linear shrinkage that illustrated potential inducement of detrimental stresses to the superimposed structures during drying. The identification and quantification of the mineralogy composition clearly evidenced the passive minerals (quartz, feldspar and mica) to be predominant (86 %), while the active phases (kaolinite, carbonates, sulfates, halides, the oxides and hydroxides of aluminum and iron) were subordinate (14 %), which substantiated potential soil settlement upon wetting. Furthermore, the micrographs depicted structures that synergistically enhanced the collapse properties of the tested deposits. These included the porous clays, silts bonded by clay and silts coated with clay, which all rendered a metastable fabric. A comparison of the stressstrain graphical plots from the consolidated undrained tests at the field and saturated moisture contents indicated a drastic reduction (up to 73 %) in deviator stress at saturated water content. This was attributed to the augmentation of the interparticle spaces, caused by a rise of up to 337 kPa in pore water pressure. Shear strength parameters obtained from Mohr’s failure envelopes were also decreased by up to 80 %. The hydrocollapse index measured from the oedometer tests ranged from 10 to 15 % at a vertical stress of 200 kPa. It indicated severe settlement problems for structures constructed on this soil. This was caused by the loss in shear strength of the soil under the saturated conditions and a high slaking mechanism that reached a maximum rating of 4. Generally, the mineralogy composition, morphology, saturated shear strength, slaking and hydrocollapse index collectively indicated the possibility of soil volume decrease. In fact, the check for serviceability limit state demonstrated a settlement that exceeded the tolerable value of 50 mm. The cracks observed on structures were, therefore, related to soil settlement. This study recommends further research on suitable ground techniques to minimise settlement, thereby improving the durability of structures. Moreover, investigations should be conducted to understand the pressure induced by warping during shrinkage

Understanding Seismic Embankment Dam Behavior Through Case Histories

From the lessons learned from past earthquakes, it is noticed that modern embankment dams withstand the design earthquake without significant damages. In spite of this scenario it is important to prevent the occurrence of incidents and accidents of embankment dams during the earthquakes and so a deep understanding of the triggering factors is important. Well documents case histories from many parts of the world related embankment dams behaviour during recent earthquakes were carefully selected and are discussed. Based in the governed factors attention is given to the requirements for materials characterization, modelling, analysis, monitoring and safety evaluation. Ageing effects and rehabilitation of dams are analysed. The risks associated with dam projects are discussed. The benefits and concerns of dams are presented. It is important to develop new ways of thinking and strategies to address the future challenges