Paul McCombie

The use of the simple genetic algorithm in finding the critical factor of safety in slope stability analysis

Abstract A simple genetic algorithm (SGA) is applied to the search for the minimum factor of safety in slope stability analysis. The method is shown to be superior to simple optimisation routines, which can find false minima, and to ‘brute force’ approaches, which require the analysis of a very large number of possibilities. An approach to implementing SGA is defined and refined, indicating principles which may be used in applying the method to other engineering problems.

THE RELATIVE WATER DEMAND OF BROAD-LEAVED TREES—A NEW ANALYSIS OF THE KEW TREE ROOT SURVEY

Summary The Kew Tree Root Survey provides the most important data-base for damage to buildings by tree roots. It has been used to determine the relative danger different species of tree pose to building foundations on shrinkable clay soils; this can be expected to be related to the rate at which the tree uses water. Cutler and Richardson in “Tree Roots and Buildings” were properly cautious about the conclusions they drew, as there are so many factors involved. However, the author has found that general conclusions can be drawn for some of the most common species. Some of these conclusions are not consistent with recommendations given and assumptions made in the National House Building Council Standards, which have up to now been held to contain the most reliable information.

NDT Monitoring of Bridges using Innovative High Precision Surveying System

Monitoring the infrastructures is increasingly achieving a role of primary importance for their structural assessment, during service conditions or after unusual or catastrophic events. Long term monitoring has immediate implications in the safety and reliability of the infrastructures because it immediately allows data comparison between two events in the life of a structure, being able to find where and how the structure is changing its performance. Complementary to monitoring, in-situ load testing has become a viable and relatively inexpensive solution to assess structural performance, but an easy and quick setup is necessary to perform the test in an effective and relatively low cost procedure. The use of traditional test equipment for structural monitoring and load testing carries a certain number of disadvantages due to its high cost per instrumented point, limited durability and unpractical application. This paper presents, through a series of case studies, the use of high precision automated Total Station System, to remotely measure and record structure special deformations, and illustrates future research development undergoing at the University of Bath for further improving structural monitoring procedures.

The production of interactive engineering design software using Borland Delphi

Advances in PC programming systems allow the development of highly interactive engineering design software. Software can work in a way which is obvious to the user, and gives considerable feedback during and after the analysis. If an indication is given of the cost of a design, the user can concentrate on making design decisions, rather than on the mechanics of the analysis. Such programs can be developed to run themselves, making changes to the data and carrying out analysis until an optimum design has been reached. These possibilities are illustrated using a program for the design of reinforced soil structures.

TREES AND FOUNDATIONS—A REASSESSMENT

Summary The abstraction of water from the soil by tree roots causes damage tofoundations by shrinking clay soils. The factors determining whether or not damage occurs are the water supply to the ground, the flow of water through the ground to the trees roots, the water demand of the tree, and the shrinkability of the clay. Crude investigation of the extent to which a sample of clay is dessicated is shown to be possible by using the Liquidity Index as a measure of suction; a better indication is possible by measuring suction in the filter paper test, but both methods suffer because of the uncertainty in the contribution that stress relief has made to the suction measured. The main information available at present on damage to foundations by shrinkage of clay due to the water demand of trees is published in the National House Building Council Standards Chapter 4.2 (originally Practice Note 3). The most important factor involved s the water demand of the tree; the information given in the practice note is in...

Thermal imaging assessment of drystone retaining walls

Drystone retaining walls form an essential part of the infrastructure in hilly and mountainous regions around the world, by providing platforms for roads, buildings and for agricultural terraces. Research carried out in England and in France has led to a good understanding of their behaviour, but it is difficult to determine the details of the construction of individual walls without dismantling them – so it can be hard to tell if apparent defects and deformations are a threat to stability. Replacing every apparently defective or deformed wall would be a waste of resources, yet dismantling a wall would obviously be completely disruptive to its function. Invasive investigation, such as drilling, could easily cause damage to the wall structure and destabilise the wall. There is therefore a pressing need for non-intrusive methods of investigation that can reveal critical aspects of a wall’s construction. Thermal imaging can reveal important information about aspects of a wall’s construction that are critical...

Thermal imaging assessment of drystone retaining walls: some case studies

Drystone retaining walls form an essential part of the infrastructure in hilly and mountainous regions around the world, by providing platforms for roads, buildings and for agricultural terraces. Research carried out in England and in France has led to a good understanding of their behaviour, but it is difficult to determine the details of the construction of individual walls without dismantling them – so it can be hard to tell if apparent defects and deformations are a threat to stability. Replacing every apparently defective or deformed wall would be a waste of resources, yet dismantling a wall would obviously be completely disruptive to its function. Invasive investigation, such as drilling, could easily cause damage to the wall structure and destabilise the wall. There is therefore a pressing need for non-intrusive methods of investigation that can reveal critical aspects of a wall’s construction. Thermal imaging can reveal important information about aspects of a wall’s construction that are critical...

Serviceability limit state check in reinforced soil design

The nature-inspired concept of self-healing materials in construction is relatively new and has recently attracted significant attention as this could bring about substantial savings in maintenance costs as well as enhance the durability and serviceability and improve the safety of our structures and infrastructure. Much of the research and applications to date has focused on concrete, for structural applications, and on asphalt, with significant advances being made. However, to date no attention has been given to the incorporation of self-healing concepts in geotechnical and geo-environmental applications. This includes the use of concrete and other stabilising agents in foundations and other geotechnical structures, grouts, grouted soil systems, soil-cement systems and slurry walls for ground improvement and land remediation applications. The recently established Materials for Life (M4L) project funded by EPSRC has initiated research activities in the UK focussing on those applications. The project involves the development and integration of the use of microcapsules, biological agents, shape memory polymers and vascular networks as healing systems. The authors are exploring development of self-healing systems using mineral admixtures, microencapsulation and bio-cementation applications. The paper presents an overview of those initiatives to date and potential applications and presents some relevant preliminary results.By contrast to studies in petroleum geology and, despite their world-wide occurrence, geotechnical studies of ancient fluvial sediments are rare. This paper introduces the main characteristics of these sediments by reference to a classic UK example. Attention is then drawn to a number of major overseas examples where, although the principal features can be recognised, large differences arise as a result of factors such as the tectonic setting, the volume and mineralogy of the source material and the climate at the time the sediments were deposited. The first, over-riding problem for their engineering evaluation comes during the site investigation phase with the difficulty of deducing the geological structure and distribution of the widely varying lithologies.Strain accumulation in granular soils due to dynamic loading is investigated through long term cyclic triaxial tests and cyclic triaxial tests according to ASTM D 3999-91. Soil parameters, test equipment and loading conditions have a significant influence on strain accumulation, therefore a parameterization of the silica sand and a description of the cyclic triaxial test device are explained. Cyclic triaxial tests are performed and test results are presented illustrating the evolution of Young’s modulus during long term cyclic loading. The influence of the width of the stress-strain loop and the initial void ratio on strain accumulation is investigated and validated with existing accumulation models. The usefulness of Miner’s rule on sand subjected to cyclic loading is demonstrated by two tests with different packages of loading cycles.

Advances in the assessment of drystone retaining walls - some case studies

The nature-inspired concept of self-healing materials in construction is relatively new and has recently attracted significant attention as this could bring about substantial savings in maintenance costs as well as enhance the durability and serviceability and improve the safety of our structures and infrastructure. Much of the research and applications to date has focused on concrete, for structural applications, and on asphalt, with significant advances being made. However, to date no attention has been given to the incorporation of self-healing concepts in geotechnical and geo-environmental applications. This includes the use of concrete and other stabilising agents in foundations and other geotechnical structures, grouts, grouted soil systems, soil-cement systems and slurry walls for ground improvement and land remediation applications. The recently established Materials for Life (M4L) project funded by EPSRC has initiated research activities in the UK focussing on those applications. The project involves the development and integration of the use of microcapsules, biological agents, shape memory polymers and vascular networks as healing systems. The authors are exploring development of self-healing systems using mineral admixtures, microencapsulation and bio-cementation applications. The paper presents an overview of those initiatives to date and potential applications and presents some relevant preliminary results.By contrast to studies in petroleum geology and, despite their world-wide occurrence, geotechnical studies of ancient fluvial sediments are rare. This paper introduces the main characteristics of these sediments by reference to a classic UK example. Attention is then drawn to a number of major overseas examples where, although the principal features can be recognised, large differences arise as a result of factors such as the tectonic setting, the volume and mineralogy of the source material and the climate at the time the sediments were deposited. The first, over-riding problem for their engineering evaluation comes during the site investigation phase with the difficulty of deducing the geological structure and distribution of the widely varying lithologies.Strain accumulation in granular soils due to dynamic loading is investigated through long term cyclic triaxial tests and cyclic triaxial tests according to ASTM D 3999-91. Soil parameters, test equipment and loading conditions have a significant influence on strain accumulation, therefore a parameterization of the silica sand and a description of the cyclic triaxial test device are explained. Cyclic triaxial tests are performed and test results are presented illustrating the evolution of Young’s modulus during long term cyclic loading. The influence of the width of the stress-strain loop and the initial void ratio on strain accumulation is investigated and validated with existing accumulation models. The usefulness of Miner’s rule on sand subjected to cyclic loading is demonstrated by two tests with different packages of loading cycles.

Reinforced soil design using a two-part wedge mechanism: justification and evidence

The nature-inspired concept of self-healing materials in construction is relatively new and has recently attracted significant attention as this could bring about substantial savings in maintenance costs as well as enhance the durability and serviceability and improve the safety of our structures and infrastructure. Much of the research and applications to date has focused on concrete, for structural applications, and on asphalt, with significant advances being made. However, to date no attention has been given to the incorporation of self-healing concepts in geotechnical and geo-environmental applications. This includes the use of concrete and other stabilising agents in foundations and other geotechnical structures, grouts, grouted soil systems, soil-cement systems and slurry walls for ground improvement and land remediation applications. The recently established Materials for Life (M4L) project funded by EPSRC has initiated research activities in the UK focussing on those applications. The project involves the development and integration of the use of microcapsules, biological agents, shape memory polymers and vascular networks as healing systems. The authors are exploring development of self-healing systems using mineral admixtures, microencapsulation and bio-cementation applications. The paper presents an overview of those initiatives to date and potential applications and presents some relevant preliminary results.By contrast to studies in petroleum geology and, despite their world-wide occurrence, geotechnical studies of ancient fluvial sediments are rare. This paper introduces the main characteristics of these sediments by reference to a classic UK example. Attention is then drawn to a number of major overseas examples where, although the principal features can be recognised, large differences arise as a result of factors such as the tectonic setting, the volume and mineralogy of the source material and the climate at the time the sediments were deposited. The first, over-riding problem for their engineering evaluation comes during the site investigation phase with the difficulty of deducing the geological structure and distribution of the widely varying lithologies.Strain accumulation in granular soils due to dynamic loading is investigated through long term cyclic triaxial tests and cyclic triaxial tests according to ASTM D 3999-91. Soil parameters, test equipment and loading conditions have a significant influence on strain accumulation, therefore a parameterization of the silica sand and a description of the cyclic triaxial test device are explained. Cyclic triaxial tests are performed and test results are presented illustrating the evolution of Young’s modulus during long term cyclic loading. The influence of the width of the stress-strain loop and the initial void ratio on strain accumulation is investigated and validated with existing accumulation models. The usefulness of Miner’s rule on sand subjected to cyclic loading is demonstrated by two tests with different packages of loading cycles.