Layer | Fill | Outline |
---|
Map layers
Theme | Visible | Selectable | Appearance | Zoom Range (now: 0) |
---|
Fill | Stroke |
---|---|
Collaborating Authors
ABSTRACT: Based on detailed geological-geotechnical investigations on the Blagovica-Konpolje motorway section (E-W corridor in Slovenia), the influence of time on the changes of the stress-strain in the physical behavior of Carboniferous-Permian mixed soft rock mass was defined. Significant volumetric and distortion deformations appeared after a long period of rainfall after unloading of the excavation. Finally, gradual structural degradation caused sliding of the altered or disintergrated soft rock mass as this soft rock mass took on the characteristics of the saturated residual soft soil. Most important in this process were pre-existing weak soft rock zones. As a result of the suction process of pore water pressure dissipation out of the micro-cracks (dilatation suction and dissipation), viscous creeping developed. The presentation focuses on numerical back analyses which were made at three scales: mineralogical petrography specimens at micro-scale, at the scale of borehole samples and at the scale of land-sliding slopes. 1. INTRODUCTION Based on a detailed geological-geotechnical investigation of the Blagovica-Kompolje motorway section, Carboniferous-Permian soft rocks were divided into three typical layers with different strength and deformability parameters. The purpose of the investigation and analysis was to determine the input parameters for numerical analysis which were needed to specify support and retaining measures for the excavation of cutting slopes. Excavation for the foundation caused unloading and, along with heavy rainfall during autumn in 2002, activated a deep landslide in the building area of this motorway section. The landslide was successfully stabilized with an anchored pile wall, material exchange below the pile wall and a special drainage system. With detailed laboratory analysis, "in situ" examination and monitoring results, we have gathered enough data for the creeping analysis of the landslide. The analysis was conducted using a special method of calculation enabled by the software used. During each calculation step, the grid is updated and active pore pressures are recalculated. Geometric nonlinearities, occurring in deformations of this extent, are thus avoided. With the slowing of creeping, conditions were established to begin a planned restoration using an anchored pile wall. Technical observation is ongoing while the structures are operational. 2. GEOTECHNICAL INVESTIGATIONS Prior to the motorway construction, geological-geomechanical investigations were first conducted in the preliminary project phase and later in the main project phase. For those sections where the route was planned to cut into slopes, additional investigations were conducted. During the motorway construction, the back slopes of the planned supporting and retaining structures became accessible. For the main project, technical observation and monitoring were called for. For determining rock mass characteristics, we engineering geologically mapped the slopes in detail during the excavations and catalogued bore holes, outcrops and piles. For that we used the new rock mass classification for mixed and soft rock mass by determination of the geological strength index GSI [1]. In selected bore holes, preasuremeter measurements ("in situ" measurements) were conducted and intact samples taken. During laboratory examination, we conducted triaxial consolidated undrained shear tests ("CU"-tests) of fifteen intact samples and nine compressibility and permeability oedometric tests.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.30)
Deep-Seated Structurally Controlled Landslides of Corinth Gulf Rift Zone, Greece: The Case of Panagopoula Landslide
Sabatakakis, N. (University of Patras) | Tsiambaos, G. (National Technical University of Athens) | Rondoyanni, Th. (National Technical University of Athens) | Papanakli, S. (University of Patras) | Kavoura, K. (University of Patras)
Abstract A representative composite fault-related landslide of the Corinth Gulf graben named "Panagopoula" is reported that considered to be one of the most prone to slope instability sites along the main motorway and railway connecting Athens with the city of Patras. The presence of tectonically highly sheared and weathered geological formations, including Alpine basement (mainly flysch) contributes to the site instability, triggered/reactivated by seismic activity and heavy rainfalls. Although a series of remedial measures have been already constructed, the inclinometer readings during the last twenty years time period show a continuous very slow movement which indicates that the landslide is still "active". This fact has resulted to divert the axes of the new motorway and railway through twin tunnels which are under construction. Introduction The spatial and temporal evolution of landslides in the case of structurally complex slopes is lithologically and often structurally controlled while their type and frequency are mainly related to tectonic and lithological anisotropy (Baron et al. 2005; Hradecky et al. 2007). The triggering mechanisms mainly include:excessive rainfall generating high pore pressure and strong earthquakes resulting in dynamic loading conditions at the failure surface. Data such as past earthquakes or the precipitation records are useful to be gathered when a landslide model is examined since they could act as a landslide triggering mechanism. Recording of the movement through surface and inclinometer measurements as well as combination of the above information with historical records of failure could lead to a more accurate estimation of the location of the failure surface and understanding of the landslide mechanism. Slope instability in the southern segment of the Gulf of Corinth, Northern Peloponnesus, Greece, is ubiquitous and ranges from deep-seated bedrock failure to secondary earth flows in recent deposits. In this part of Greece, the periodically induced landslide events triggered by heavy rainfall, earthquake and anthropogenic activity are closely related to active fault tectonics. The Gulf of Corinth is considered as a typical example of a relatively simple asymmetric half-graben with major border faults to the south and a flexure of the northern shore. Panagopoula landslide is located along the trace of a WNW trending normal fault (dipping northwards) (Figure 1). The area is considered to be one of those most prone to slope instability along the E95 motorway and railway connecting Athens with the city of Patras. The paper outlines the significance of active fault tectonics for the development of landslides which could affect the transportation routes. Recent and past inclinometer data are evaluated in order to establish a ground displacement rate through a twenty years' time frame.
- Phanerozoic > Mesozoic (0.70)
- Phanerozoic > Cenozoic > Neogene (0.47)
- Phanerozoic > Cenozoic > Quaternary (0.47)
- Geology > Structural Geology > Tectonics > Plate Tectonics > Earthquake (1.00)
- Geology > Structural Geology > Tectonics > Extensional Tectonics (1.00)
- Geology > Structural Geology > Fault > Dip-Slip Fault > Normal Fault (1.00)
- Transportation > Ground (1.00)
- Energy > Oil & Gas > Upstream (1.00)
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)
A10 Motorway – Refurbishment Reitdamm: Stabilization of a Longtime Creeping Landslide of a Hillside Embankment
Bach, Dietmar (IGT Geotechnik und Tunnelbau Consulting Engineers) | Sönser, Sabrina (IGT Geotechnik und Tunnelbau Consulting Engineers) | Breymann, Helfried (Consulting Engineer) | Treichl, Hanspeter (ASFINAG BMG)
Abstract At the end of the 1970's the A10 motorway was constructed. One lot of this large infrastructure project was a 450 m long and 40 m high embankment dam situated on an inclined ground surface. Shortly after the beginning of construction of the engineered fill, geotechnical measurements showed movement of the embankment toe. The movement could not be stopped by reducing the rate of filling or periodically suspending the works. The increase of excess pore water pressure in a layer of saturated glacial lake clay, which was known to exist beneath the original ground surface, worsened the situation. Due to the required opening date of the highway the consolidation of the clay could not be undertaken. Therefore, extensive stabilization and dewatering works had to be installed during the construction period and in later years up to the present day. 1 History 1.1 Situation Brandecker (1976) investigated the geologic and geotechnical ground conditions. He emphasized in his report that the following stabilization measures should be carried out in order to guarantee a successful construction of the dam:Stone wedge used as a supporting foot for the dam Partial excavation of settlement sensitive soil layers Systematic dewatering of the whole dam basement Monitoring of the displacements during the building process The dam (500,000 m) was filled with excavation material from the Reit tunnel, which is situated at the east end of the embankment. It is based on an inclined surface consisting of silty sand and gravel layers with layers of glacial lake clay beneath. The crystalline basement existing below is composed of phyllite and sedimentary moraine material (Figure 1).
ABSTRACT: Identification of bedding shears during site investigations is problematical. The paper describes the use of the observational approach and discusses its implications for design and construction. RESUME: L'identification des bandes de cisaillement dans des plans de stratification presente des difficultes au cours des etudes d'un terrain de construction. Cet article decrit I'usage des methodes base sur l'Observation et les implications pour les constructions. ZUSAMMENFASSUNG: ldentifizierung der Schichtungsseherebene wahrend der Bodenuntersuchung ist problematisch. Der Bericht beschreibt die Verwendung der Beobachtungsmethode und diskutiert deren Implikationen fuer die Bemessung und den Bauprozess. 1. INTRODUCTION The identification of rock failure mechanisms, and ipso facto, material parameters, is of prime importance in the investigation of rock cuttings since these are the most fundamental controls on overall design and provision of revetment. However, rock outcrops for direct assessment of rock conditions are usually limited. Even in areas of comparatively good exposure, experience has shown that often the most critical geological factors have been obliterated by weathering. Reliance must therefore be placed in the first instance on indirect techniques and geological prediction, based on an interpretation of the stratigraphy, structural history and hydrogeology. These can be supplemented by observations and controls within the construction process, but only if the appropriate contractual and financial provisions are in place. This paper discusses the problems and successes in the identification of potential failure mechanisms and subsequent design input for three case histories of deep motorway cuttings in diverse strata:-700m long × 20m deep cutting in Thrace, Turkey, through very weak mudstones. 1000m long × 80m deep cutting in Anatolia, Turkey, through weakly indurated outwash fan deposits, consisting of sandy silts with gravel bands and thin layers of stiff clay, 600m long × 35m deep cutting in North Wales, UK, through strong banded mudstones and siltstones. These three case histories illustrate very different geological environments but show many similarities. All were affected by tectonic activity, resulting in gently folded sequences and consistent dips over long distances. In all cases, an important control on stability was the presence of residual clay-coated shear surfaces, parallel to bedding planes. These developed by flexural slip as a result of folding. The extent to which theoretical considerations can be used effectively to predict whether a sequence is at risk from this mechanism is discussed. CASE HISTORY 1: THRACE MOTORWAY, TURKEY Several sections of the Thrace Motorway in Turkey cross outcrops of the Sulemaniye Formation, Miocene strata often described as "Istanbul Green Clay", between 11 km and 47 km west of the centre of Istanbul. The stability problems encountered on this section of motorway are discussed in detail in Gordon, Lord and Statham (1991). In the mid 1980's, prior to motorway construction, this was an area of rolling farmland with few geological exposures. Hence little was known of the stratigraphic or structural details, although it was well known that the sequence contained heavily overconsolidated. The 25 motorway cuttings in these areas, had originally been schemed by others with slopes of 1 of 3 and no drainage measures. A maximum cutting depth of 20m occurred where the motorway crossed sidelong ground for a distance of some 700m. The geological complexity of this area had caused extensive landslides which, prior to motorway construction, were dormant and to some extent masked by a long history of intensive agriculture. Boreholes had been sunk at intervals along the route, mainly at the sites of structures, but these did not reveal the geological complexity and at feasibility stage, the motorway designers had not recognised the large areas of residual landslide. The scheme proceeded to construction without any further geotechnical investigation. Re-activation of landslides occurred during initial excavation of several of the cuttings, well before formation levels were reached. In the worst case, progressive displacement extended up to 80m beyond the crest of the original cutting. These difficulties required further investigations, re-appraisal of the design, significant delays and expensive remedial works.
- Geology > Geological Subdiscipline > Stratigraphy (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock (0.89)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (0.88)
- Management > Professionalism, Training, and Education > Communities of practice (0.76)
- Data Science & Engineering Analytics > Information Management and Systems > Knowledge management (0.76)