Engineering Geology 

Abstract: Metals including lead, chromium, arsenic, zinc, cadmium, copper and mercury can cause significant damage to the environment and human health as a result of their mobilities and solubilities The selection of the most appropriate soil and sediment remediation method depends on the site characteristics, concentration, types of pollutants to be removed, and the end use of the contaminated medium The approaches include isolation, immobilization, toxicity reduction, physical separation and extraction Many of these technologies have been used full-scale This paper will review both the full-scale and developing technologies that are available Contaminants can be isolated and contained to minimize further movement, to reduce the permeability of the waste to less than 1×10−7 m/s (according to US guidelines) and to increase the strength or bearing capacity of the waste Physical barriers made of steel, cement, bentonite and grout walls can be used for isolation and minimization of metal mobility Another method is solidification /stabilization, which contains the contaminants in an area by mixing or injecting agents Solidification encapsulates contaminants in a solid matrix while stabilization involves formation of chemical bonds to reduce contaminant mobility Another approach is size selection processes for removal of the larger, cleaner particles from the smaller more polluted ones To accomplish this, several processes are used They include: hydrocyclones, fluidized bed separation and flotation Addition of special chemicals and aeration in the latter case causes these contaminated particles to float Electrokinetic processes involve passing a low intensity electric current between a cathode and an anode imbedded in the contaminated soil Ions and small charged particles, in addition to water, are transported between the electrodes This technology have been demonstrated in the US full-scale, in a limited manner but in Europe, it is used for copper, zinc, lead, arsenic, cadmium, chromium and nickel The duration of time that the electrode remains in the soil, and spacing is site-specific Techniques for the extraction of metals by biological means have been not extensively applied up to this point The main methods include bioleaching and phytoremediation Bioleaching involves Thiobacillus sp bacteria which can reduce sulphur compounds under aerobic and acidic conditions (pH 4) at temperatures between 15 and 55°C Plants such as Thlaspi, Urtica, Chenopodium, Polygonum sachalase and Alyssim have the capability to accumulate cadmium, copper, lead, nickel and zinc and can therefore be considered as an indirect method of treating contaminated soils This method is limited to shallow depths of contamination Soil washing and in situ flushing involve the addition of water with or without additives including organic and inorganic acids, sodium hydroxide which can dissolve organic soil matter, water soluble solvents such as methanol, nontoxic cations, complexing agents such as ethylenediaminetetraacetic acid (EDTA), acids in combination with complexation agents or oxidizing/reducing agents Our research has indicated that biosurfactants, biologically produced surfactants, may also be promising agents for enhancing removal of metals from contaminated soils and sediments In summary, the main techniques that have been used for metal removal are solidification/stabilization, electrokinetics, and in situ extraction Site characteristics are of paramount importance in choosing the most appropriate remediation method Phytoremediation and bioleaching can also be used but are not as well developed

Abstract: a University of New South Wales, Sydney, Australia b Department of Geotechnical Engineering and Geosciences, Technical University of Catalonia -UPC, Jordi Girona 1-3, D-2 Building.08034 Barcelona, Spain c PBBG SA, Lausanne, Switzerland d Department of Civil Engineering, University of Salerno, via Ponte don Melillo, 84084 Fisciano, SA, Italy e Urbater, 48 avenue Trespoey 64000 Pau, France f U.S. Geological Survey, Box 25046 MS966, Denver, CO., USA

Abstract: Barton, N., 1973. Review of a new shear-strength criterion for rock joints. Eng. Geol., 7: 287–332. The surface roughness of rock joints depends on their mode of origin, and on the mineralogy of the rock. Amongst the roughest joints will be those that formed in intrusive rocks in a tensile brittle manner, and amongst the smoothest the planar cleavage surface in slates. The range of friction angles exhibited by this spectrum will vary from about 75° or 80° down to 20° or 25°, the maximum values being very dependent on the normal stress, due to the strongly curved nature of the peak strength envelopes for rough unfilled joints. Direct shear tests performed on model tension fractures have provided a very realistic picture of the behaviour of unfilled joints at the roughest end of the joint spectrum. The peak shear strength of rough—undulating joints such as tension surfaces can now be predicted with acceptable accuracy from a knowledge of only one parameter, namely the effective joint wall compressive strength or JCS value. For an unweathered joint this will be simply the unconfined compression strength of the unweathered rock. However in most cases joint walls will be weathered to some degree. Methods of estimating the strength of the weathered rock are discussed. The predicted values of shear strength compare favourably with experimental results reported in the literature, both for weathered and unweathered rough joints. The shear strength of unfilled joints of intermediate roughness presents a problem since at present there is insufficient detailed reporting of test results. In an effort to remedy this situation, a simple roughness classification method has been devised which has a sliding scale of roughness. The curvature of the proposed strength envelopes reduces as the roughness coefficient reduces, and also varies with the strength of the weathered joint wall or unweathered rock, whichever is relevant. Values of the Coulomb parameters c and Φ fitted to the curves between the commonly used normal stress range of 5–20 kg/cm2 appear to agree quite closely with experimental results. The presence of water is found in practice to reduce the shear strength of rough unfilled joints but hardly to affect the strength of planar surfaces. This surprising experimental result is also predicted by the proposed criterion for peak strength. The shear strength depends on the compressive strength which is itself reduced by the presence of water. The sliding scale of roughness incorporates a reduced contribution from the compressive strength as the joint roughness reduces. Based on the same model, it is possible to draw an interesting analogy between the effects of weathering, saturation, time to failure, and scale, on the shear strength of non-planar joints. Increasing these parameters causes a reduction in the compressive strength of the rock, and hence a reduction in the peak shear strength. Rough—undulating joints are most affected and smooth—nearly planar joints least of all.

Abstract: Landslides can result in enormous casualties and huge economic losses in mountainous regions. In order to mitigate landslide hazard effectively, new methodologies are required to develop a better understanding of landslide hazard and to make rational decisions on the allocation of funds for management of landslide risk. Recent advances in risk analysis and risk assessment are beginning to provide systematic and rigorous processes to enhance slope management. In recent years, risk analysis and assessment has become an important tool in addressing uncertainty inherent in landslide hazards. This article reviews recent advances in landslide risk assessment and management, and discusses the applicability of a variety of approaches to assessing landslide risk. Firstly, a framework for landslide risk assessment and management by which landslide risk can be reduced is proposed. This is followed by a critical review of the current state of research on assessing the probability of landsliding, runout behavior, and vulnerability. Effective management strategies for reducing economic and social losses due to landslides are described. Problems in landslide risk assessment and management are also examined. D 2002 Elsevier Science B.V. All rights reserved.