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ABSTRACT: The article presents the results of detailed geotechnical and laboratory investigations which served as the basis for the model of a sliding, unstable slope in the area of designed structures at the motorway section Trojane – Blagovica (Slovenia). On the basis of geotechnical profiles the stability analyses were carried out. As for the input data of stability analyses the results of triaxial, rotation and direct shear tests along with the modified Hoek&Brown failure criterion were used. The critical failure was also accurately determined by means of inclination measurements and mineralogic-petrographic investigations. The pressures on designed structures were determined and the foundations conditions were calculated. INTRODUCTION Within the supplementary geotechnical investigations for the realisation of the construction works feasibility project on the motorway Vransko-Blagovica, there has been performed a geotechnical boring of deep boreholes, and a detailed engineering geologic, structural- geologic and hydrogeologic charting. In the area of supporting structures and viaducts, 47 boreholes in the total depth of 1430.7 m were carried out. During the boring, 285 of intact samples were taken for laboratory tests, and at the same time 56 in-situ measurements by pressuremeter took place along with 294 standard penetration tests. All cores of the boreholes were accurately recorded in an engineering-geological (RQD, RMR, QMR) and geotechnical way. The depth of performed investigations of elasticity and deformability of the soft rocks, as well as of the samples for triaxial investigations were conformed to the requirements of the structures foundation. The assembled results of all the investigations served for the formulation of the model – geotechnical cross-sections and input parameters for stability analyses as well as for the determination of pressures on designed structures and calculation of the foundation conditions. GEOLOGIC STRUCTURE The slope, on which the construction works are designed, consists of perm-carbonic strata (C, P).
- Geology > Geological Subdiscipline (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.41)
ABSTRACT: Previous construction works in regions of permo-carboniferous slates have led to difficulties with slopes. Three cases are presented where shear characteristics after investigations were estimated to be much higher than was established later when problems arose during construction works. Detailed investigations of standard in-situ and laboratory tests and sets of cylindrical triaxial tests were carried out to find out reasons for the stability problems. Drained and undrained incremental or continuous loading and unloading tests that considered conditions due to construction works were performed. Parameters determined with detailed investigations have much lower values than those found with previous investigations. The analyses performed, which are not presented in this paper, have shown suitability of the presented constitutive model. INTRODUCTION An extensive programme of motorway network construction is being carried out in Slovenia where very different geological regions are being encountered. The most interesting are regions formed of permocarboniferous slates. During the existing practice they have proved to be as very exacting and unpredictable. Investigations often show much better stiffness characteristics of permo-carboniferous slates than they display after construction works. The most influential condition change is large excavations of cuts and the consequent changes of stress states and ground water regimes. It is obvious that mechanical characteristics are very difficult to precisely establish by in-situ tests, because the influences of construction works can not be considered. The results of laboratory tests are unreliable as well, because it is difficult to obtain representative samples from critical layers. Therefore the models for analyses are inaccurate. Agitated stratification of land can make precise model determination more difficult. Three cases of large construction works in permo-carboniferous slopes are presented. Further investigations and analyses to perform sanitation works have shown a distinct decrease of shear strength in particular layers of permo-carboniferous slates in all three cases.
- Phanerozoic > Paleozoic > Permian > Cisuralian > Asselian > Lower Asselian (1.00)
- Phanerozoic > Paleozoic > Carboniferous > Pennsylvanian > Upper Pennsylvanian > Gzhelian (1.00)
- Geology > Rock Type > Metamorphic Rock > Slate (0.89)
- Geology > Geological Subdiscipline > Geomechanics (0.67)
ABSTRACT: The paper presents a critical review of the state of the art of geotechnical engineering of natural slopes, cuts and fills in soil. Topics which are covered include the pre and post failure mechanics at the micro and macro scale, including discussion of contractant and other strain weakening soils, creep, progressive and retrogressive failure and fissured clays. Geotechnical investigation requirements and methods for analysis of stability and deformations, and for analysis of post failure velocity and travel distance are reviewed. It is concluded that many slope instability hazards may be managed by traditional factor of safety methods, but that it is important that the post failure behaviour be considered. Observational, and risk assessment methods may be more appropriate than the traditional methods in many cases. 1. INTRODUCTION 1.1 General Objectives of the Paper This paper sets out to present a critical review of the state of the art of geotechnical engineering of natural slopes, cuts and fills in soil. This includes site characterization, including the geology and hydrogeology, the establishment of the material properties and pore pressures, the mechanics of sliding at the micro and macro scale, analysis of stability, deformations pre and post failure, and management of the slope hazard. The emphasis is on practical issues, and the integration of engineering geology, hydrogeology, rock and soil mechanics. We will be seeking to demonstrate that it is now practical to quantify the potential post failure deformations sufficiently well that their assessment should be part of any geotechnical assessment of a slope. In this way, the engineering of a slope can be linked to the consequences of failure, allowing better management of the risks. We have also emphasized those situations which are not well modelled by conventional effective stress analyses.
- Asia > Japan (1.00)
- North America > United States > California (0.92)
- Oceania > Australia (0.67)
- (3 more...)
- Overview (0.67)
- Research Report > New Finding (0.67)
- Geology > Structural Geology > Tectonics (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.92)
- (3 more...)
- Geophysics > Seismic Surveying (1.00)
- Geophysics > Borehole Geophysics (1.00)
- Materials > Metals & Mining (1.00)
- Government > Regional Government > North America Government > United States Government (1.00)
- Government > Military > Army (1.00)
- (2 more...)
- Asia > Middle East > Iraq > Kirkuk Governorate > Zagros Basin > Khabbaz Field > Shuaiba Formation (0.93)
- Asia > Middle East > Iraq > Kirkuk Governorate > Zagros Basin > Khabbaz Field > Nahr Umr Formation (0.93)
- Well Drilling > Drilling Operations (1.00)
- Well Drilling > Drilling Fluids and Materials (1.00)
- Well Completion (1.00)
- (10 more...)
ABSTRACT: Ground support comprises a wide field of geotechnical engineering. Therefore some special topics are selected: Reinforcement and dowelling of soil and rock by nails, anchors, piles and jet-grouting. Thus, the ground becomes more or less a compound body which locally can be considered a quasi-monolith. In the case of retaining structures or underground excavations, prestressed anchors are used in addition to conventional reinforcement. The paper focuses on retaining structures, underpinning of buildings, and tunnelling. Residual shear strength of the ground is considered an essential value for parametric design analyses and risk assessment, and the observational method is favoured over the fully-engineered design. INTRODUCTION Building in unstable, heterogeneous, or soft ground includes a significantly higher calculated risk than is experienced by the other branches of civil engineering. In most cases, sophisticated theoretical models and calculations simply feign an accuracy which in practice does not exist. Statistical investigations do not really solve the problem either. This refers to the ground parameters as well as to the climatic data. But, parametric studies are essential for a reliable risk assessment and to follow the concept of most probable and most unfavourable conditions. This involves designs which can be improved in steps during construction or even in the long-term according to the observational method. Unstable terrain requires a "semi-empirical" design method based on comprehensive monitoring - and pre-planned safety measures which allow for future strengthening if the results of long-term measurements require such. The observational method has also proved suitable for deep excavations in urban areas and for tunnelling. Reinforcing or dowelling of soil or rock is a very appropriate method to achieve such goals, because this technique is adaptable to practically all local conditions with regard to morphology, spacing, forces etc.
- Energy > Oil & Gas > Upstream (1.00)
- Construction & Engineering (1.00)
- Materials (0.83)
Abstract Landslides are recognized as one of the major hazards, reflected through large material and human loss throughout the world. They can be triggered by anthropogenic, but also due to a natural and/or climatic factors. Rainfalls are noted as one of the most important natural triggers for landslides re-activation, while the positive trend in the climate change shown recently, implies that this type of weather-related hazards would be even more frequently prevalent in future. Thus, rainfall induced landslide arises large interest among the professionals that are working in this field recently, and is main concern of this research paper. The long-term stability, as well as the landslide reactivation susceptibility due to rainfall, of one well documented slope is going to be assessed in time, through FE analysis in program package PLAXIS. In the model two different hydrologic scenarios measured on the aforementioned location, are going to be analysed; average annual precipitation data for the period between 1961-1996 and average annual precipitation data for the most recent period between 2005-2014. The soil behaviour in time is represented with the non-linear hypoplastic material model, which is considered that will provide the most reliable results for the deformations, taking into account the strain-softening behaviour. One of the main interests of this paper is the slope failure mechanism in time, the spatial position of the failure plane due to the rainfall infiltration and pore water fluctuation, as a result of changes in the meteorologic data. Furthermore, this paper provides a comprehensive analysis of the laboratory tests needed for the hypo-plastic material model.
- Energy > Oil & Gas > Upstream (0.96)
- Materials > Chemicals > Commodity Chemicals > Petrochemicals (0.61)