ABSTRACT: This paper describes sources of local geological information and briefly summarises the current understanding of the Hong Kong Geological Survey with respect to the classification and distribution of rocks and superficial deposits in Hong Kong. General aspects of the geology of particular relevance to engineering are emphasised.

 ABSTRACT: Systematic logging of core from site investigations in Hong Kong is largely undertaken by rote and as a consequence vital clues as to the ground conditions can be missed or not considered. This paper highlights the importance of a comprehensive approach to rock and soil description, taking into account all geological factors seen in core and soil samples that have direct relevance to the geological model. For example, the contact relationships between rock types and deformation structures, such as foliation and veins, must be described and become part of any geological model. To illustrate how particular geological features are essential to the formulation of any comprehensive and reliable geological model, three recent ground investigations are described. The first is the site of the main support tower and back spans for the eastern side of the Stonecutters Bridge, which is underlain by three different types of granite, two sets of dykes, and several shear zones and faults. The second is the foundation for a school in Tin Shui Wai, where an inclined zone of intense deformation, within a sequence of metasedimentary rocks and a granodiorite body, has been the focus of weathering. Highly to completely decomposed rocks extend to over –100 mPD, and in places are covered by a wedge of fresh to slightly decomposed rock up to 30 m thick. The third example is the foundation of a proposed apartment block at Tung Chung, which consists of complex ground conditions characterized by the presence of metasedimentary rocks, feldsparphyric rhyolite dykes, granite, cavity-fill sediments and collapse material. In all these cases, the ground conditions could not have been determined without a full description and understanding of the geological evolution of the sites.

 ABSTRACT: This paper provides an introduction into active processes of weathering and how these affect the engineering properties of rocks. Five particular aspects are dealt with in some detail. The first concerns the shear strength of intact materials with particular consideration of the transition from rock-like to soil-like behaviour. The second topic is permeability of weathered rock profiles and in particular the often channelised flow of groundwater. Topic three concerns material disintegration and the growth of joints in the weathered rock mass; a classification of joints based on their “life-cycle” from oriented micro fractures to fully developed planes of weakness is introduced. The fourth topic concerns weathering along joints and the consequences for shear strength of such discontinuities. Finally deterioration of the overall rock mass is considered in a geomorphologic development sense, where such deterioration occurs and how such deterioration may be taken as indicative that failure is developing.

ABSTRACT: This paper presents some observations from a personal perspective on engineering geological practice and the effect of discontinuities on the mass stability of tropically weathered rocks. Case histories are used to illustrate some of the fundamental principles that are applicable to the investigation and design of excavations in discontinuous rock and saprolite masses.

ABSTRACT: The inter-relationship between soil behaviour and laboratory testing is addressed at an engineering yet fundamental level.  The issues of saprolites as structured soil and soft soil with a meta-stable structure are addressed. The principles of specifying laboratory soil testing are also presented.

ABSTRACT: A clear insight into the factors controlling formation of different failure mechanisms in rock engineering problems is important and vital to proper engineering analysis, design and construction monitoring. For most of the tunnelling conditions in Hong Kong, a parametric analysis can demonstrate that failure initiation is kinematically controlled rather than stress-induced controlled. This implies that during the site investigation stage, greater emphasis should be placed on obtaining the optimal shear strength parameters of discontinuities than in assessing the strength of the rock mass. A case study is described to illustrate that the representative shear strength parameters of a rock joint are highly variable because of the scale effect in measuring local roughness. This paper also describes recent advancements in rock joint mapping using non-contact techniques that incorporate 3-D laser scanning and digital photogrammetry.

ABSTRACT: This paper introduces (a) types of soil tests and advanced/special soil testing systems, (b) measurement of stress-strain-strength of Hong Kong marine soils in different stress states, and (c) general properties and behavior of Hong Kong marine soils and empirical correlations.

ABSTRACT: This paper discusses common mistakes in the interpretation and analysis of geotechnical data.  Empirical geotechnical correlations are often established by inappropriate choice of non-fundamental parameters, or incorrect use beyond their range of applicability.  Spurious correlations are frequently generated between functionally related variables.  Regression analyses are incorrectly treated as a statistical tool for interpretation of data when they are simply numerical techniques for curve fitting.  Algebraic manipulations of empirical correlations are often performed without knowing its potential danger.  Geotechnical theories are supported by improperly fitted straight lines to data.  Advice for proper interpretion of geotechnical data is given in the paper to prevent the above mistakes.