Effect of vibro stone column installation on the performance of reinforced soil

Empirical design methods for stone column foundations are often on single stone columns or as a homogeneous medium of soil/column. These methods underestimate the capacity of the composite system because they do not take into account the increased confining stress acting on the stone column or the increased stiffness of the soil. This study used Plaxis 2D to study the effect of the installation method on the confining pressure and soil stiffness around a single column by assuming the installation of the column could be modelled as an expanding cavity followed by consolidation of the surrounding soil. The mean stress and stiffness generated during installation between two, adjacent columns was used in Plaxis 3D to compare the settlement of circular foundations on estuarine deposits reinforced by stone columns at a site in Santa Barbara, California. Good agreement was found between the predicted and actual settlement of the trial foundations on three column arrangements. The predictions gave a better estimate of the settlement compared to those using a unit cell or homogeneous medium showing that improvements to the soil should be taken into account when assessing stone column performance

Hydraulic conductivity of composite soils

Many natural soils (e.g. glacial tills, residual soils, and alluvial soils) and artificial soils (e.g. engineered fill, environmental barriers) are formed of a range of particle sizes and types. These soils are often difficult to sample and test when using standard site investigations thus it is necessary to resort to empirical correlations; most of which were developed for coarse-grained (e.g. clean sands) or fine-grained (e.g. pure clays) soils. The hydraulic conductivity is dependent on the void ratio, clay type and particle size distribution and, in the case of composite soils it is also dependent on the clay content. Composite soils formed of four clay minerals and two sands were consolidated from slurry to determine the variation of hydraulic conductivity with clay content, clay type and void ratio. The matrix dominated soils, the flow is a function of the matrix void ratio and clay type; and, in clast dominated soils, the intergranular void ratio and particle size distribution. The transition from a matrix dominated soil to a clast dominated soil occurs at a fines content between 20% and 35%

The Resilient Engineer

An increase in the magnitude and frequency of extreme events together with increases in urbanisation and population are testing the resilience of the social and economic infrastructure; that is the built environment. Over the years improvements in technology and changes to regulations have improved the performance of the built environment. This has raised community’s expectations but also lowered their resilience because of the success of the engineering profession to produce increasingly robust but complex systems. This is not sustainable because of the extreme events and because the increased resources required to create a resilient environment is contributing to climate change; a major cause of extreme events. Engineering is core to a resilient society and the role of the engineer has to change to help create a community that is able to cope with extreme events in an environment that is becoming more harmful. Achieving this means a fundamental shift in engineering education because the role of the engineer and engineering tools are changing. The 21st century engineer can no longer rely on the education that delivered the 20th century built environment. The 21st century engineer has to be resilient to cope with the pace of change that includes a shift in design placing more emphasis on outcomes and a shift in engaging society to help communities become more resilient

Briefing: The role of historical records in current and future civil engineering practice

Civil engineers design, build, operate, maintain and adapt projects with characteristics that distinguish them from other types of projects created by other engineering disciplines and artists. ■ They transform people’s lives by creating the infrastructure and built environment that underpins the wealth, health and well-being of society. ■ They are complex systems that require a multidisciplinary approach. ■ Most civil engineering projects are unique. ■ They are geographically distributed and mostly stationary. ■ There is a sense of permanence because they can last for one or more generations. ■ They are adapted throughout their life to cope with political, social, economic and technological changes. ■ They generate a wealth of information in the form of objects, letters, minutes, reports, papers, calculations, drawings, images and, now, digital records. It is the wealth of information that is the subject of this paper and how relevant it is to current and future generations of engineers

The Future of Geotechnical and Structural Engineering Research

A review of publicly funded UK structural and geotechnical research showed it was among the best in the world but incremental rather than transformational. Furthermore, public research investment in this area is less than in other sectors despite significant investment in construction and infrastructure generally. This is also at a time of rapid change driven by population growth, resource scarcity and security, developments in technology, society’s expectations and aspirations, and climate. A major review of the purpose of infrastructure and construction was thus undertaken by representatives from academia, industry, research organisations, clients and government. They concluded if transformational research is to take place, the research themes to address are hazards, understanding material behaviour, paradigm shift in design, construction processes, building performance, smart buildings, asset management, intervention, decarbonisation and adaption

Elastic-plastic solutions for expanding cavities embedded in two different cohesive-frictional materials

An analytical solution of cavity expansion in two different concentric regions of soil is developed and investigated in this paper. The cavity is embedded within a soil with finite radial dimension and surrounded by a second soil, which extends to infinity. Large-strain quasi-static expansion of both spherical and cylindrical cavities in elastic-plastic soils is considered. A non-associated Mohr–Coulomb yield criterion is used for both soils. Closed-form solutions are derived, which provide the stress and strain fields during the expansion of the cavity from an initial to a final radius. The analytical solution is validated against finite element simulations, and the effect of varying geometric and material parameters is studied. The influence of the two different soils during cavity expansion is discussed by using pressure–expansion curves and by studying the development of plastic regions within the soils. The analytical method may be applied to various geotechnical problems, which involve aspects of soil layering, such as cone penetration test interpretation, ground-freezing around shafts, tunnelling, and mining

The permeability of composite soils

Many natural soils (e.g. glacial tills, residual soils, and alluvial soils) and artificial soils (e.g. engineered fill, environmental barriers) are composite soils formed of a range of particle sizes and types. These soils are often difficult to sample and test when following standard site investigation practice thus it is necessary to resort to empirical correlations, most of which were developed for either coarse-grained (e.g. clean sands) or fine-grained (e.g. pure clays) soils. The hydraulic conductivity of clean sands is a function of the void ratio and particle size distribution, and for clays, the clay type and void ratio. This suggests that the hydraulic conductivity of composite soils will be a function of these properties and the clay content. Composite soils formed of four clay minerals and two sands were consolidated from slurry to determine the variation of hydraulic conductivity with clay content, clay type and void ratio. With matrix dominated soils, soils that contain with more than 35% fines content, the flow is a function of the matrix void ratio and clay type; and, for clast dominated soils, soils that contain less than 20% fines content, the intergranular void ratio and particle size distribution. The behaviour of soils with a fines content between 20% and 35% depends on the confining pressure and density

The decoupled nature of basal metabolic rate and body temperature in endotherm evolution

The origins of endothermy in birds and mammals are important events in vertebrate evolution. Endotherms can maintain their body temperature (Tb) over a wide range of ambient temperatures primarily using the heat that is generated continuously by their high basal metabolic rate (BMR)1. There is also an important positive feedback loop as Tb influences BMR1,2,3. Owing to this interplay between BMRs and Tb, many ecologists and evolutionary physiologists posit that the evolution of BMR and Tb must have been coupled during the radiation of endotherms3,4,5, changing with similar trends6,7,8. However, colder historical environments might have imposed strong selective pressures on BMR to compensate for increased rates of heat loss and to keep Tb constant9,10,11,12. Thus, adaptation to cold ambient temperatures through increases in BMR could have decoupled BMR from Tb and caused different evolutionary routes to the modern diversity in these traits. Here we show that BMR and Tb were decoupled in approximately 90% of mammalian phylogenetic branches and 36% of avian phylogenetic branches. Mammalian BMRs evolved with rapid bursts but without a long-term directional trend, whereas Tb evolved mostly at a constant rate and towards colder bodies from a warmer-bodied common ancestor. Avian BMRs evolved predominantly at a constant rate and without a long-term directional trend, whereas Tb evolved with much greater rate heterogeneity and with adaptive evolution towards colder bodies. Furthermore, rapid shifts that lead to both increases and decreases in BMRs were linked to abrupt changes towards colder ambient temperatures—although only in mammals. Our results suggest that natural selection effectively exploited the diversity in mammalian BMRs under diverse, often-adverse historical thermal environments

Systematic review of grounded theory studies in physiotherapy

Aim: This systematic review aimed at appraising the methodological rigor of grounded theory research published in the field of physiotherapy to assess how the methodology is understood and applied. A secondary aim was to provide research implications drawn from the findings to guide future grounded theory methodology research. Methods: A systematic search was conducted in MEDLINE, CINHAL, SPORT Discus, Science Direct, PubMed, Scopus and Web of Science to identify studies in the field of physiotherapy that reported using grounded theory methodology and/or methods in the study title and/or abstract. The descriptive characteristics and methodological quality of eligible studies were examined using the assessment guidelines developed by Hutchison, Johnston and Breckon (2011). Findings: The review included sixty-eight studies conducted between 1998 and 2017. The findings showed that grounded theory methodology is becoming increasingly used by physiotherapy researchers. Thirty-six studies (53%) demonstrated a good understanding and appropriate application of grounded theory methodology. Thirty-two studies (47%) presented descriptive findings and were considered to be of poor methodological quality. Conclusions: There are several key tenets of grounded theory methodology that are integral to the iterative process of qualitative theorizing and need to be applied throughout all research practices including sampling, data collection and analysis