No description available.

No description available.

No description available.

Subsidence related to shallow abandoned mine workings are considered an inherent threat to safety, particularly of the transport infrastructure. In order to better constrain the conditions that can lead to subsidence, a study taking the form of a parametric analysis to investigate the features and properties significant in the causes of abandoned mine working instability has been undertaken within the numerical modelling code FLAC3D. The effect on stability of variations in excavation geometry along with variations of the in-situ stresses related to the overburden loading have also been investigated. Use has been made of interface elements to allow the modelling of coal measures rocks as a horizontally laminated assemblage of strata whereby discrete or discontinuous behaviour representative of the failure of layered rock masses over abandoned mine workings can be modelled. The modelling of variably dipping discontinuity features commonly present in rock masses has also been undertaken using an anisotropic constitutive model. The effects of fluctuations in the groundwater table are modelled as variations in pore water pressures on the stability of excavations have also been investigated. The modelling results indicate that the friction angle of the rock mass (which may be considered a composite of the intact rock and discontinuity friction angles) is a key parameter in controlling the geometry of failure of the strata forming the excavation roof. Pore water pressures are also shown to be significant in causing the initiation of instability. Empirical tools to allow the estimation of the height of collapse before arching or choking of the void occurs are also introduced as well as a numerical based methodology to allow the modelling of collapse propagation in rock masses above excavations. Numerical modelling was also undertaken of the subsidence event that occurred at Dolphingstone in Scotland which suggests that the increase in the ground water table may have been responsible for the collapse.

Landslide mechanisms and processes, particularly within the basal deformation region during failure, are poorly understood in the current knowledge. The aim of this research is to understand the initiation processes of shallow rainfall-triggered landslides under humid, tropical conditions. The major objectives are (1) to investigate the actual processes of rainfall-triggered landslides; and (2) to examine the relationship between the rates of pore water pressure increase and the rates of soil movement. Field sampling has been undertaken at two landslide sites on weathered volcanic slopes on Lantau Island, Hong Kong (22 N， 114(^o)E). Reinflation tests have been conducted on the undisturbed soil samples using a triaxial stress path cell to replicate the field conditions during rainstorm events. Various rates of increasing pore water pressure have been designed with reference to the field monitoring data. Landslide initiation processes have been deduced by examining the relationship between the increasing pore water pressures and soil deformation. The results demonstrate that rainfall-induced landslide development on weathered slopes undergoes three stages with distinctive movement patterns towards failure. The key controlling mechanism appears to be plastic deformation. The varied velocities are dependent on the stress state (changes in the mean effective stress, under constant shear stress), the pore water pressure reinflation rate and soil permeability, stage 1 represents a perfectly plastic state below yield. Velocity remains low or at zero as the soil particles are strongly interlocked. The fluctuating to constant strain rates at stage 2 are primarily controlled by the reinflation rate and permeability after exceeding the yield state, with localised interparticle sliding. Rapid acceleration to failure occurs at stage 3, facilitated by the general remoulding process. The systematic movement patterns have also been observed in shallow rainfall- induced landslides in plastic soil materials. The steady-state behaviour could be a precursor for the acceleration to the final failure.

Along a narrow swath from Nottingham through to Hartlepool, broad shallow depressions up to 100m in diameter and, more rarely, scarp-edged subsidence hollows are observed. These topographical features coincide with the sub-crop of the Permian strata beneath the Quaternary deposits and are attributed to the dissolution of sub-surface gypsum. Boreholes (<150 m deep) prove the existence of several layers of gypsum within the Permian geological succession.

No description available.

No description available.

No description available.

Το φαινόμενο των κατολισθήσεων στην χώρα μας είναι αρκετά σύνηθες, γεγονός που οφείλεται στην πολυσύνθετη γεωλογική κατασκευή και την έντονη τεκτονική καταπόνηση τους. Οι πρόσφατες κατολισθητικές κινήσεις προκαλούνται κυρίως από τις ανθρώπινες δραστηριότητες λόγω της συνεχώς αυξανόμενης αστικοποίησης και επέκτασης των περιοχών δόμησης, οι οποίες γίνονται χωρίς τις απαραίτητες τεχνικογεωλογικές μελέτες. Στην εκδήλωση των κατολισθητικών φαινομένων συμβάλλουν αποφασιστικά το ύψος βροχόπτωσης, ο υψηλός δείκτης σεισμικότητας της χώρας μας αλλά και η αυξημένη εκδήλωση πυρκαγιών, όπως συμβαίνει και στην περιοχή μελέτης. Σκοπός αυτής της διπλωματικής εργασίας είναι η συμβολή στην αναγνώριση, χαρτογράφηση και ερμηνεία της μορφολογίας των παλαιότερων και πρόσφατων κατολισθητικών φαινομένων της περιοχής, με σκοπό την κατανόηση των αιτιών που τις προκαλούν για να δοθούν λύσεις στο πλαίσιο των μορφογενετικών διεργασιών. Προκειμένου να επιτευχθούν οι παραπάνω στόχοι έγινε αναγνώριση των κατολισθητικών φαινομένων στην ύπαιθρο. / Landslides are a usual phenomenon in our country because of the earth’s geological complexity and the immense tectonics. Recent landslides movements are caused by human operations due to the increase of urbanization and the growth of regions that are constructed without the necessary engineering and geological studies. Furthermore, factors that contribute the cause of landslides are the rainfalls, the high rate of earthquakes but also the frequent breakout of fire, as it happens in the region of our study. The aim of this thesis is the recognition, the mapping and the interpretation of the morphology of former and recent landslides, as a result to understand why they are caused and to find solutions. In order to achieve the above, landslides have been identified in the field.