Geochemistry in Geotechnical Engineering Problems: Ettringite as Case Study
M. Chrysochoou
ABSTRACT: Chemical and environmental changes in soils can affect their geotechnical properties, a fact that is increasingly acknowledged in recent years. Geochemistry offers a wide variety of modelling and experimental tools that can be used to study related problems. An increased number of researchers utilize geochemical modelling and spectroscopy to study changes in soil chemistry in the geotechnical field. This study illustrates the application of this methodology to a significant geotechnical problem, ettringite-induced heave in stabilized clays. Geochemical modelling was used to estimate the ranges of dissolved constituents that are needed to make ettringite, i.e. Ca, Al and SO4, as well of silica, which is known to influence indirectly ettringite stability. The study illustrates that systematic testing of ion activities in stabilized soils to generate data for modelling is needed, as well as understanding of the relationship of these activities to soil mineralogy, the type of stabilizer and time. Spectroscopy, such as X-ray Diffraction, can aid in this regard by providing an understanding of soil mineralogy, both qualitative and quantitative.
KEYWORDS: Geochemistry, Geochemical modelling, Mineralogy, Ettringite
Engineering Properties of Chromium Contaminated Soils
Wiwat Kamolpornwijit, Jay N. Meegoda, Janitha H. Batagoda
ABSTRACT: Soil and groundwater contamination occurs with the industrial activities. Majority of such contaminated sites are in urban areas. With the recent interest by millennial generation or generation Y to live in urban areas, there is a tremendous demand for urban land. Hence some of those contaminated sites will be remediated for residential purposes while others will be developed as brownfield sites for retail purposes. For contaminated soil to be treated or contaminated sites to be used as brownfield sites, one should have a comprehensive understanding of engineering properties of contaminated soils. This manuscript describes such situation where engineering properties of chromium contaminated soils were used to evaluate the feasibility of such soils to be used as construction material or treated and used in brownfield sites. Chromium contaminated soils from nine contaminated sites in New Jersey were subjected to several physical and chemical tests to determine their engineering properties. In addition advanced instrumentation such as environmental scanning electron microscope (ESEM) and X-ray diffractometer (XRD) were used to evaluate the feasibility to use chromium contaminated soils as construction material or remediated and used in brownfield sites. The physical test results were compared with New Jersey Department of Transportation (NJDOT) and ASTM specifications for use as a construction material as well as to remediate the soil. The chemical test results and information obtained from advanced instrumentation were analyzed to determine the long-term impact of using chromium contaminated soils as construction material or remediated and used in brownfield sites. Based on test results it was found that chromium contaminated soils from nine sites are not suitable candidates for either entrapping the contaminants using cement or asphalt or to use as a construction material in brownfield sites.
KEYWORDS: Engineering Properties, Chromium Contaminated Soils, Solidification and Stabilization, Construction Material, Brownfield Development
Study on factors affecting heavy metal sorption characteristics of two geomaterials
K.M.Nithya, D.N.Arnepalli and S.R.Gandhi
ABSTRACT: This study investigates effect of liquid to solid ratio, initial concentration of heavy metals, pH and composite heavy metal solution and nature of sorbent on sorption capacity of two different geomaterials such as clayey soil and moorum. The batch sorption experiments were carried out with the selected geomaterials using different heavy metal solutions such as Copper, Manganese, Zinc, Lead and Chromium. Based on the experimental results, the following conclusions are drawn i) increasing liquid to solid ratio decreases the removal rate of heavy metal, however heavy metal sorbed on unit mass of the sorbent increased at equilibrium ii) increase in pH and the initial heavy metal concentration leads to an increase in the heavy metal uptake by the geomaterials iii) nature of the clay mineral present in the geomaterials plays significant role in controlling the sorption characteristics of the geomaterials compared to amount of clay content present in the geomaterials iv) observed order of selectivity of heavy metals is Cr >Pb >Cu >Mn ~Zn.
KEYWORDS: Heavy metal, Geomaterials, Sorption capacity, Landfills, Clay liner
Reduction of Chromium in Water and Soil Using a Rhamnolipid Biosurfactant
I. Ara and C.N. Mulligan
ABSTRACT: Hexavalent chromium is of great concern as it is highly toxic and carcinogenic. The objective of this study is the reduction of hexavalent chromium to trivalent chromium using the biosurfactant rhamnolipid in both water and soil media. Rhamnolipid is readily biodegradable with a very low environmental impact. Batch experiments were performed to evaluate the feasibility of using rhamnolipid for the removal and reduction of hexavalent chromium from contaminated soil and water. Rhamnolipid concentration, pH and temperature were evaluated and found to affect the reduction efficiency. At a low concentration of Cr (10 ppm), 100% of initial Cr (VI) in water at optimum conditions was reduced., whereas at a higher concentration (400 mg/L) the reduction was lower (24.4%). In the case of soil, rhamnolipid, the reduction trend of the extracted chromium is the same as in water media.
KEYWORDS: Remediation, Chromium, Biosurfactant, Rhamnolipid
Reclamation project of a Brownfield site at Rio de Janeiro State, Brazil
M.C. Barbosa, A.R.M. Barboza de Oliveira and M.E.S. Marques
ABSTRACT: The paper presents the geotechnical solution proposed for remediation and further redevelopment of a Brownfield site from a bankrupted zinc processing industry. All installations were abandoned without a post closure technical plan, including a 1.2 million cubic meters mineral waste pile inside a 260,000 m2 liquid waste pond. Both structures were settled upon a soft clay deposit contaminated with Zn and Cd. The technical solution proposed involved the complete drainage of the liquid pond, accompanied by on site treatment, a hydraulic barrier of pump & treat wells and the construction of an engineered waste containment facility using the mineral solid waste as compacted earth fill material combined to geosynthetic products.
KEYWORDS: Contaminated soil, Waste containment, Soft clay, Reinforcement with geosynthetics
A Review of Acidic Groundwater Remediation in the Shoalhaven Floodplain in Australia
Buddhima Indraratna, Udeshini Pathirage and Laura Banasiak
ABSTRACT: Acid sulfate soils can be found around low-lying coastal floodplains. Acidic groundwater generated from acid sulfate soils creates adverse conditions to vegetation and aquatic life and corrodes steel and concrete infrastructure. As long as these soils are undisturbed and below the groundwater table, they are chemically inert. Therefore, it is important to maintain the groundwater table above the sulfidic soil horizon. Modified floodgates and weirs have been implemented in these low-lying areas to improve water quality. Nevertheless, these methods are not promising in low-lying areas because of the risk of flooding. As a solution, a pilot-scale permeable reactive barrier was installed and has proven to be a promising technology for long-term remediation. This paper presents a review of the above mentioned methods used for acidic groundwater remediation in coastal Australia with detailed field verification data.
KEYWORDS: Acid sulfate soils, Acidic groundwater remediation, Permeable reactive barrier
Experimental and numerical study of electro-osmosis on kaolinite under intermittent current
Liming Hu, Hui Wu, Jay N. Meegoda, and Qingbo Wen
ABSTRACT: Electro-osmosis has been used as an effective technique for soft ground improvement. An axisymmetric testing apparatus was developed to study the dewatering and consolidation behaviour of kaolinite samples with different initial water content during electroosmosis under intermittent current. An axisymmetric numerical model with non-linear variation of soil parameters was developed to compare with the experiment results. With the increase of the initial water content, the electrical resistance decreased and the current through the kaolin samples increased. As a result, the total water discharge and the final surface settlement also increased. The comparison of the experiment results and numerical results validated the effectiveness of the numerical model. The change in soil parameters should be considered during electro-osmosis, otherwise the final surface settlement may be over-estimated. The formation of cracks and the friction between the soil mass and apparatus caused the deviation between experiment results and numerical results.
KEYWORDS: electro-osmosis, initial water content, intermittent current, numerical model, surface settlement
Electro-osmosis drainage effect of a new type of EKG electrode
Yang Shen and Yande Li
ABSTRACT: The electro-kinetic geo-synthetics (EKG) electrode is a kind of electrode which may avoid the electrode corrosion and provide an effective drainage channel during the electro-osmosis process. Comparing tests between a new type of EKG electrode and the iron electrode were carried out. The drainage amount, drainage velocity, current, potential distribution, water content and cracks were monitored. Results showed that the iron electrode eroded seriously while the EKG electrode kept intact. In addition, drainage capacity on the soil’s top surface of the EKG electrode was better than that of the iron electrode. The potential drop on the electrode-soil interface of the EKG electrode was smaller than that of the iron electrode when the anode was arranged in the hexagonal pattern. The water content increased gradually from the anode to the cathode for the iron electrode, while it increased at first and then decreased from the anode to the cathode for the EKG electrode.
KEYWORDS: Electro-osmosis, EKG electrode, Iron electrode, Voltages, Hexagonal pattern
Innovative Soft Soil Improvement Method through Intelligent Use of Vacuum De-Watering and Dynamic Compaction Techniques
R. Liang, S. Xu and T. Edil
ABSTRACT: Recently, an innovative soft soil improvement method was advanced in China by integrating and modifying vacuum consolidation and dynamic compaction ground improvement techniques in an intelligent and controlled manner. This innovative soft soil improvement method, often referred to as “High Vacuum Densification Method (HVDM)”, has been successfully used in China and Asia for numerous large-scale soft soil improvement projects, from which enormous time and cost savings have been achieved. In this presentation, the working principles of the HVDM are described, followed by a summary of two case studies. Results of numerical simulation using FLAC3D computer program, in which dynamic compaction is modelled as a three-dimensional, coupled hydro-mechanical model, are presented to highlight the mechanisms of positive pore pressure generation due to dynamic compaction. Both field studies and numerical simulation results support the mechanisms of HVDM in that dynamic compaction induced positive pore water pressure together with vacuum generated negative pore water pressure have added effects in rapidly expelling water out of the soil, thus increasing density (reducing void ratio) and improving undrained shear strength of soft, fine-grained soils in a relatively short duration.
KEYWORDS: HVDM, Soil improvement, Vacuum consolidation, FLAC3D
Some Studies on Engineering Properties, Problems, Stabilization and Ground Improvement of Lithomargic Clays
R. Shivashankar, A. U. Ravi
ABSTRACT: The study area for this paper is coastal Karnataka in India. The area has laterites and lateritic soils, and also a large number of sporadic lateritic hillocks. The soil stratification mainly consists of lithomargic clay sandwiched between the weathered laterite at top and the hard granitic gneiss underneath. Quite often the top laterites are removed in this area for use as bricks for construction purposes, thus exposing the underlying lithomargic clay. This coastal area receives copious amount of rainfall and a lot of developmental activities are taking place. These lithomargic clays, locally called as ‘shedi soils’ are also used as fill material in low lying areas, very often adjacent to water bodies. These soils behave as dispersive soils and are also highly erosive. A lot of engineering problems – such as foundation problems, subgrade problems, erosion and slope stability problems are being faced due to the presence of these shedi soils. Some laboratory studies on the engineering and strength properties of these lithomargic clays and stabilized soils, Ground Improvement on shedi grounds are made and reported.
KEYWORDS: Lithomargic clays, Dispersive soil, Erosion, Slope stability, Stabilization, Geogrid reinforcement, Stone columns, Coir fibres, Geocoir, Vetiver
Stone column reinforcement of a soft South African clay: A laboratory investigation
L. Sobhee-Beetul and D. Kalumba
ABSTRACT: The current rate of development in the construction industry has given rise to higher demands for land. In pursuit of satisfying the needs of property developers, engineers have resorted to new ground improvement technologies to eventually implement construction on lands which were previously regarded as unfeasible or uneconomical for this purpose. This study therefore aimed at investigating the potential use of singular stone columns in improving a soft wet clay of South African origin. Bench scale tests were conducted to evaluate the effect of the moisture content of the base soil and the column diameter. The results indicated a clear improvement in the vertical applied stress as well as in the settlement of the clay, when subjected to a compressive load. These findings were ultimately used to generate information regarding the stress concentration ratio and the settlement reduction ratio.
KEYWORDS: Stone columns, Stress-settlement behavior, Stress concentration ratio, Settlement reduction ratio
Numerical modelling of Tunis soft clay
Mnaouar Klai, Mounir Bouassida and Seifeddine Tabchouche
ABSTRACT: The paper briefly reviews research investigations conducted on Tunis soft clay that is classified as problematic soil. Results obtained from an experimental study carried out on undisturbed Tunis soft clay specimens are presented and interpreted. On the basis of experimental results the paper discusses which constitutive law can describe at best the observed behaviour of Tunis soft clay? The elastoplastic behaviour modelled by the Hardening Soil Model (HSM) is then justified based on numerical simulation of oedometer and triaxial tests carried out on undisturbed soft clay specimens. Adopted parameters of the HSM model are considered to simulate the behaviour of geotechnical structures founded on Tunis soft clay using the finite element code Plaxis V9-2D and the FLAC3D code. The prediction of behaviour of two Tunisian case studies is analyzed: cylindrical oil tank on soft clay reinforced by sand columns and full pile loading. Comparison between predictions by the soft soil model (SSM) and HSM is presented.
KEYWORDS: Behavior, Characterization, Hardening, Numerical, Simulation, Soft clay
A Framework for the Destructuring of Clays During Compression
M. D. Liu, S. Horpibulsuk, and Y. J. Du
ABSTRACT: Based on the work by Liu and Carter (1999, 2000), a framework for the compression behaviour of structured clays is proposed, in which two entities of an existing soil are differentiated and described clearly: the original structure of the soil and the destructuring the soil has experienced. A theoretical Compression Destructuring Line (CDL) is proposed to describe the whole destructuring process of soil from its original or un-destructured state. Soils of the same original structure form a unique CDL, irrespective of loading history or structuring/destructuring history. The “theoretical” original structure of a soil is represented by parameters A and c, which are detectable from compression tests on soil specimens with or without destructuring. The destructuring a soil has experienced is dependent on its current yielding stress and is quantified when the value of the yield stress is determined. The compression behaviour of four types of clay with twenty-two tests is then analysed. It is seen that the compression behaviour of clays with various structures is described well, and the magnitude of desctructuring can be quantified by the proposed method.
KEYWORDS: Clays, Compression, Destructuring, Structure of soils
Inundation Caused by Sea-Level Rise Combined with Land Subsidence
K. Yasuhara, S. Murakami and N. Mimura
ABSTRACT: As a crucially important issue that Asia–Pacific region residents are currently confronting, this paper treats an increasing probability of unusual and extreme natural disasters that continue as a consequence of climate change, combined with sea-level rise (SLR). The calculated inundation areas in two low-lying regions in Thailand and Japan are visualized using a geographical information system (GIS). Results suggest that the effect of SLR on increasing inundation is more remarkable than that of land subsidence. Therefore, appropriate adaptation measures must be undertaken by the respective regions to avoid the enormous losses and damage from inundation that are expected to derive from the effects of SLR combined with land subsidence.
KEYWORDS: Sea-level rise, Land subsidence, Inundation, Compound disaster
Levels of what and how in the Education of Geo-engineering on Problematic Soils
R. Ray, P. Scharle, R. Szepesházi
ABSTRACT: Majority of recent studies discussing the development issues of civil engineering education focus the attention on the innovative teaching and learning methods. Evolution of the engineers’ habit of mind demands, in addition, the conscious harmonization and synchronization of educational level, basic mathematical and mechanical preliminaries and professional content. Consideration of the interdependence among these factors results in some conclusions usable for educators interested in creating innovative curricula. Distinction between BEng and MEng levels of competence has to be identified properly. Geotechnical works on or in problematic soils deserve this attention, in particular.
KEYWORDS: Burland-tetrahedron, Levels of competency, Complexity and multidisciplinarity, Analogy with medicine
Characteristics and Consequence of Nepal Earthquake 2015: A Review
A S M Fahad Hossain, Tuk Lal Adhikari, Mehedi Ahmed Ansary and Quazi Hamidul Bari
ABSTRACT: An earthquake is a natural disaster that comes in different parts of the earth every year. Most of them are very weak and unnoticeable. But some of them are too severe to cause a great loss of lives and destruction of properties. A major earthquake happened in Nepal on 25th April 2015. More than 8,000 people died and more than 19,000 people got wounded in this earthquake. People of Nepal had anticipated but never experienced such a devastating earthquake. This paper deals with the Gorkha earthquake in Nepal, its causes and characteristics, previous earthquake history of Nepal, consequences etc.
KEYWORDS: Nepal, Geology, Seismicity, Earthquake, Damages, Gorkha, Reverse Fault
SPECIAL FEATURE STORY ON “Challenges in Going Underground in Big Cities”
L. J. Endicott
ABSTRACT: The hearts of many large cities are already congested. City planners are looking for ways to accommodate more people and to supply their needs including means of transportation. High rise buildings, descriptively called “sky scrapers”, are common and going higher does not necessarily solve the problem. Increasing the number of people in a congested area severely overtaxes the infrastructure with no space to expand it. Enclosure by sub-urban development inhibits lateral development. The next place to look is underground. Already many buildings have basements, already there are many subways for pedestrians, for metros and for roads and in several cities these are inter-connected. However, if one digs a hole in the road one will encounter lots of utilities and as more metro lines are developed they cross each other and construction to shallow depths in developed urban areas becomes deeper encountering more obstructions and can be very expensive. This paper reviews some of the challenges that face planners and geotechnical engineers when considering how to strategically plan urban development in major cities by going deeper underground.
KEYWORDS: Caverns, Basements, Underground, Planning
HISTORIC NOTE: Underexcavating the Tower of Pisa: Back to Future
J. B. Burland, M. B.Jamiolkowski, and C. Viggiani
SYNOPSIS: The stabilization of the Tower of Pisa is a very difficult challenge for geotechnical engineering. The tower is founded on weak, highly compressible soils and its inclination has been increasing inexorably over the years to the point at which it is about to reach leaning instability. Any disturbance to the ground beneath the south side of the foundation is very dangerous; therefore the use of conventional geotechnical processes at the south side, such as underpinning, grouting, etc., involves unacceptable risk. The internationally accepted conventions for the conservation and preservation of valuable historic buildings, of which the Pisa Tower is one of the best known and most treasured, require that their essential character should be preserved, with their history, craftsmanship and enigmas. Thus any intrusive interventions on the tower have to be kept to an absolute minimum and permanent stabilization schemes involving propping or visible support are unacceptable and in any case could trigger the collapse of the fragile masonry.
In 1990 the Italian Government appointed an International Committee for the safeguard and stabilization of the Tower. It was conceived as a multidisciplinary body, whose components are: experts of arts, restoration and materials; structural engineers; geotechnical engineers. After a careful consideration of a number of possible approaches, the Committee adopted a controlled removal of small volumes of soil from beneath the north side of the foundation (underexcavation). The technique of underexcavation provides an ultra-soft method of increasing the stability of the tower which is completely consistent with the requirements of architectural conservation.
The paper reports the analyses and experimental investigations carried out to explore the applicability of the procedure to the stabilization of the leaning tower of Pisa. All the results being satisfactory, a preliminary stage of underexcavation of the tower has been carried out in 1999; the results obtained are presented and discussed.
