Engineering Geological Units Research Articles

A review of igneous and metamorphic saprolites

Major difficulties in ground engineering works in areas of humid climates arise from the internally heterogeneous and erratically varying zones of weathering profiles developed over igneous and metamorphic rocks as a result of dominantly chemical weathering processes. This paper provides a critical review of recent efforts on improving the description and classification of weathering grades, and discusses current conceptual and practical issues and proposed methods for the engineering geological characterisation of igneous and metamorphic saprolites. Analysis of these issues reveals that lack of comprehensive (geochemical, mineralogical, microfabric, and engineering geological) characterisation studies within well-defined geological frameworks is the underlying reason for failure to define, characterise, and model saprolites as complex engineering geological units and to devise specific site investigation methodologies to explore these complexities.

Urban geology: a case study of Tongchuan city, Shaanxi Province, China

Urban geology is the study of urban geologic environments to provide a scientific basis for rational land use planning and urban development. This paper examines the major geotechnical and environmental geologic problems arising from the characteristics (topography, geology and soil types, including their properties and areal distribution) and human engineering activities (slope excavation, underground mining) of Tongchuan city. The main factors restricting urban development are: steep slopes; landslides; the wide distribution of problematic soils; flooding; and surface subsidence caused by underground mining. Information theory has been applied to predict the slope susceptibility. The area of surface subsidence caused by mining at present and in the future is delimited using a finite element method. The factors closely related to land use planning are: slope susceptibility and landslides; flooding; collapsible soils; surface subsidence related to mining; and the low bearing capacity of a bearing layer. These are combined to produce uniform engineering geological units. The result of a suitability assessment of the study area is illustrated in the form of a rational land use planning map.