Statistics and Data Analysis in Geology

The initiation and propagation of failure in intact rock are a matter of fundamental importance in rock engineering. At low confining pressures, tensile fracturing initiates in samples at 40%–60% of the uniaxial compressive strength and as loading continues, and these tensile fractures increase in density, ultimately coalescing and leading to strain localization and macro-scale shear failure of the samples. The Griffith theory of brittle failure provides a simplified model and a useful basis for discussion of this process. The Hoek–Brown failure criterion provides an acceptable estimate of the peak strength for shear failure but a cutoff has been added for tensile conditions. However, neither of these criteria adequately explains the progressive coalition of tensile cracks and the final shearing of the specimens at higher confining stresses. Grain-based numerical models, in which the grain size distributions as well as the physical properties of the component grains of the rock are incorporated, have proved to be very useful in studying these more complex fracture processes.

Fracture initiation and propagation in intact rock – A review

The effect of scale on the shear behaviour of joints is studied by performing direct shear tests on different sized replicas cast from various natural joint surfaces. The result show significant scale effects on both the shear strength and deformation characteristics. Scale effects are more pronounced in the case of rough, undulating joint types, whereas they are virtually absent for planar joints. The key factor is the involvement of different asperity sizes in controlling the peak behaviour of different lengths of joints. It is shown that as a results both the joint roughness coefficient (JRC) and the joint compression strength (JCS) reduce with increasing scale. The behaviour of multiple jointed masses with different joint spacing is also considered. It is found that despite unchanged roughness, jointed masses consisting of many small blocks have higher peak shear strength than jointed masses with larger joint spacing. These scale effects are related to the changing stiffness of a rock mass as the block size or joint spacing increases or decreases. Economic methods for obtaining scale-free estimates of shear strength are described.

Experimental studies of scale effects on the shear behaviour of rock joints

Matlab (the language of technical computing): using matlab graphics ver.5

A database of some 300 case histories of wall and ground movements due to deep excavations worldwide is presented. Although recognizing the weakness in the approach, a large database is used to exa...

Database for Retaining Wall and Ground Movements due to Deep Excavations

Dimensionering av samverkanskonstruktioner i berg med sannolikhetsbaserade metoder : En inledande studie

Large infrastructure projects are in general unique as the conditions and demands vary from one project to another. Furthermore, these projects are often related to risks of different nature due to high technological level, high environmental, public and political focus, long lead and project times, large and complex organizations, complex contracts etc. This paper aims to give some guidelines how to perform a successful management of risks in a large infrastructure project. The main conclusion is that the key to a successful risk management in a large infrastructure projects is early planning and a strict and continuous execution during the entire life-cycle of the project. Good planning and control of the risks enable an organized, comprehensive and iterative approach for identifying and evaluating the risks and give handling options necessary to optimize the project strategy. The management of risks should be performed as early as possible in the life-cycle of a project in order to ensure that critical risks are incorporated into the project plan and addressed with mitigation actions.

On risk management in large infrastructure projects

This contribution gives a case study on the deformations of anchor back-tied steel sheet pile walls and retained soils at deep excavations in soft soils overlying bedrock in Stockholm. Instrumentation results show the deformation of the retained soils is larger than that from similar case histories. The monitored anchor stresses increase quickly in the early stages of excavation and decease gradually to a constant value during later stages, while the lateral displacements of the sheet pile walls increase gradually. The results of both monitoring and numerical analysis show that this dynamic feature becomes weak as the thickness of the underlying soils is small. The decrease of the anchor stresses is mainly due to the flectional behavior of the sheet pile wall and the stress rotation in the retained soils.

Deformation of Anchor-Sheet Pile Wall Retaining System at Deep Excavations in Soft Soils Overlying Bedrock

Geotechnical Strategies for Poverty Reduction in Kibaha, Tanzania : Best Way Forward for Damaged Buildings on Expansive Soils

Describing the mechanical parameters of a rock joint with single values is difficult since rock has a natural spatial variation. In addition to this, the interpretation of the results is dependent ...

Håkan Stille

Papers

Dimensionering av samverkanskonstruktioner i berg med sannolikhetsbaserade metoder : En inledande studie

On risk management in large infrastructure projects

Deformation of Anchor-Sheet Pile Wall Retaining System at Deep Excavations in Soft Soils Overlying Bedrock

Geotechnical Strategies for Poverty Reduction in Kibaha, Tanzania : Best Way Forward for Damaged Buildings on Expansive Soils

Variation of Mechanical Parameters of a Slightly Weathered Joint In Granite Estimated From Fourteen Shear Tests