Overview of Innovations in Geotechnical Engineering

This paper outlines some historical and current innovative concepts that underpin the developments in geotechnical engineering. The far reaching aim is to inspirationally encourage further innovation in that innovation need not necessarily be entirely new and unique ways of doing things. Accordingly, the lessons from the historical development, bio mimicry and emerging concepts are illustratively presented. The importance of creating added value to projects through innovation is endorsed. A number of examples based on the author’s research and experience, ranging widely across the themes of the conference are presented.. In many ways geotechnology has reached maturity over the last century, but some scenarios continue to remain as challenging engineering problems. In the recent times, geotechnical engineering finds benefit in being at the crossroads with the advancements in high-tech solutions and the expanding geo technology applications, and in multi disciplinary collaborations with nanotechnology, biotechnology and information technology. The goal of innovative geo engineering research must provide effective solutions in both short and long term, with knowledge and understanding to solve problems with more sustainable certaint

Some Built Environment Research Contributing to Sustainability

Engineering in all forms must address global challenges of sustainability including its dimensions such as poverty, urbanisation, and climate change. The built environment is the dynamic interface between human society as it interacts and influences the ecosystem.  An understanding of this inextricably linked interdependence underpins the sustainability issues relevant to Civil Engineering. Geotechnical engineering outstand the rest of the disciplines in being the most resource intensive and having an early stance in the construction process. Philosophies and definitions of sustainability, as appropriate to geotechnical engineering is punctuated with illustrations through such research studies that contribute to sustainable development. This paper is thus a technical narrative of such innovative geotechnical research focusing on the author’s research career to include the modeling and assessment of the performance of a rectangular hyperbolic paraboloid shell foundation to mimic the “duck’s foot” on very soft mud; innovative research on the development of rocker pipes to arrest the often unnoticed failure of utility services arising from differential settlement; industrial design and sustainable installation of thick compacted London clay surround to protect the Heathrow Express Rail link Tunnel from noxious gases entering the tunnel as it traversed through an old landfill site;  Urban Heat Island studies; Hemp in rammed earth construction,; Quality control and enhancement of geo synthetic clay liners; adoption of lightweight manufactured aggregates; used vegetable oil in asphalt pavements and soil stabilization and sustainable construction through use of enzymes and light geo composites on challenging soils are presented

Optimising the Performance of Bentonite in Geosynthetic Clay Liners

Geosynthetic clay liners (GCLs), developed over the last quarter century, are innovative composite matting comprising of bentonite with two covering geosynthetics. The three-layered (2:1) clay mineral montmorillonite forms the dominant (approximately 75-90% by weight) clay mineral in the bentonite that is used in its manufacture. Quantitative mineralogical analyses with an assessment of the adsorbed cation regime need to be normally carried out as part of performance appraisal. The mineralogical and geotechnical differences between the preferred sodium and the less effective calcium montmorillonite are presented in the paper. The liners with its encapsulated high active clay minerals depend on the water balance between the sealing element and the surrounding soil layers. Assessment of long term hydraulic conductivities and clay-leachate compatibility assessment is also deemed necessary and the derogatory factors affecting the performance of the bentonite in GCLs placed in difficult construction and hostile chemical environments are discussed. The performance specifications for GCLs are identified in this paper and the need to enhance its cation exchange capacity with polymer treatment coupled with the need for factory prehydration of the untreated sodium bentonite is emphasised

Rocker Pipe Solution to Alleviate Settlement Induced Distress in Flexible Pipes

Soil-pipe interaction studies generally recognise the significance of deformations in the pipe due to soil loading, but not differential ground and structure movements, which can induce excessive stress concentrations in the pipeline. Plastics pipes can suffer failure due to such movements, though their flexibility makes them less vulnerable than rigid pipes. This paper examines the settlements and how the redistribution of the soil sub grade reactions caused by the installation of a pipeline within a soil mass, can then be estimated by treating the pipeline as a beam on elastic foundation. Various case histories are summarised, demonstrating these effects, and pointing the way to possible solutions, which could be incorporated at the project design stage

Drying Kinetic of Prehydrated and Extruded Clay Mat

The isothermal drying of prehydrated and extruded clay mat was investigated on a laboratory scale over a temperature and relative humidity range from 20°C to 40°C and 15% to 70% respectively. Two sets of polymer enhanced clay mats were used in this study. By measuring the mass loss of the samples during the isothermal drying process basis dependencies necessary to describe the kinetic drying process was obtained. The most commonly used model, Page, Wang & Singh, Henderson & Pabis and Thin layer equation were used to fit experimental data using a nonlinear regression analysis. The fit quality of the proposed model was evaluated by using the standard error of estimate, relative percent error and coefficient of correlation. Results probed that the Page model was more appropriated to predict prehydrated and extruded clay mat for the range of temperatures and relative humidity studied. Applied model analysis enabled evaluation of the main transport properties: drying constant, drying rate, effective diffusion coefficient and exponential model parameter. It was found that the drying condition and type of polymer incorporated in the clay mat strongly influenced the drying kinetic and transport parameters

Moisture Desorption Isotherms and Thermodynamic Characteristic of Prehydrated and Extruded GCL

An experimental investigation into the drying of pre-hydrated and extruded GCL is presented in this paper. Moisture desorption isotherm at temperature from 20 to 40°C and water activity from 0.20 to 0.70 were determined using the static gravimetric method. The moisture isotherms were sigmoid shaped and were influenced by the thermal environment. The Guggenheim- Aderson-DeBoer (GAB) was used to fit experimental values using a non-linear regression analysis. GAB model was appropriate to predict the desorption equilibrium moisture content of pre-hydrated and extruded GCL for the range of temperatures and water activities studied. Finally, an expression for predicting the thermal property was developed

Geotechnical Characteristics of Peat

Peat soil is encountered in many areas and generally originates from plant/animal remains and is considered partly as decomposed biomass (Adnan and Wijeyesekera, 2007). Due to this composition, the structure of this soil is very different when compared with inorganic soils like clay, sand and gravel. Peat has a high compressibility, low shear strength, high moisture content and low bearing capacity (Bujang, 2004, Adnan et al., 2007). The behaviour and composition of peats in different geographical areas are different from one another, accentuating the need in soil engineering for a useful geological classification of peat soils. This paper focuses on presenting a comparative overview of the characteristic geotechnical properties for these soils. It also examines and discusses the effects of composition on the basic properties and behaviour of each soil, supported by case studies from Malaysia

Mathematical Modelling of Moisture Movement in Geosynthetic Clay Liners

Drying characteristic of clays has been revisited and a mathematical model to predict moisture change has been developed and is presented in this paper. The development of the mathematical model has allowed for the factors controlling the moisture movement within the clay for a range of temperature, relative humidity environments, and varying properties of clay composite. Strong correlations between aforesaid parameter and drying characteristics were observed and are discussed in detail. In addition, an argument is presented for the superiority of the drying-rate test in current laboratory procedures for determining the moisture retention in comparison with moisture extraction under ‘on site’ conditions

Flexibility of ‘Clay Mats’

This paper presents a scientific development to addressing the current absence of a convenient technique to identify the ductile to brittle transition of clay mats. The applicability of clay mats can be brought into question if they become brittle due to drying in hot weather / tropical climates. Bentonite clay mats produced with different liquid polymers and at different moisture content were used in the study. The dependence of flexural stiffness on moisture content is presented. All the specimens showed that the flexibility of the clay mat declined exponentially with decreasing moisture content. Often one would adopt the feeling from a finger pressure test to give a perception of the softness / stiffness of the material. The paper also presents an extension of this concept to adopt an appropriately modified Brinell hardness test for the clay mats. Concurrently, 3 point bending tests were carried out on samples of the clay mat to obtain a value for the elastic structural stiffness (EI). The paper further confirms a strong correlation between Brinell Hardness Test and the structural stiffness. This study helps to assess the performance of clay mats with different proportions of additives that have been introduced in the mat manufacture to delay the inevitable drying characteristics of the mat, when exposed to hostile thermal environments

Experimental investigation of hydrodynamic erosion of soils

Recent research studies revealed that most bridge piers and other hydraulic structures such as levees and embankments adopted in flood protection schemes in maritime environment have collapsed due to the failures attributed to scour associated with a soil–hydrodynamic interaction phenomenon (e.g. Shirole and Holt, 1991). Though erosion characteristics of coarse sands and gravels are relatively well known, soil-hydrodynamics interaction for finer sands such as silts and clays is not fully investigated. A series of small-scale laboratory experiments were conducted in a moveable sediment tank to investigate scour characteristics under various flow and soil conditions. The present paper discusses preliminary experimental observations and the analysis of hydrodynamic erosion of soils in line with the extensive research project „Mathematical and Physical Modelling of Hydrodynamic Erosion of Soils (HES)‟ carried out under the „UEL Promising Researcher Fellowship 2009-2010‟ funded by the University of East London (UEL)