Observations from past events are used to show that the concept of progressive failure may explain translational progressive landslides and spreads — large landslides occurring in sensitive clays. During progressive failure, the strain-softening behaviour of the soil causes unstable forces to propagate a failure surface further in the slope. Translational progressive landslides generally take place in long, gently inclined slopes. Instability in a steeper upslope area is followed by redistribution of stress, which increases earth pressure further downslope. Passive failure may therefore occur in less-inclined ground, heaving the soil. Spreads are usually trigged by erosion of a deposit having a higher angle near the toe. Instability starts near the toe of the slope and propagates into the deposit, reducing earth pressure. This may lead to the formation of an active failure with dislocation of the deposit into horsts and grabens. The failure mechanism of both types of landslides is controlled by the stresses in the slope and the stress–strain behaviour of the soil. The mechanism presented explains the sensitivity of a slope to minor disturbances and the resulting high retrogressions observed for such landslides in Scandinavia and eastern Canada.

Batten to rafter connections in light framed timber housing can be vulnerable to wind loading, and failures of these connections are one of the more common failure modes seen in post windstorm damage surveys. Such failures often occur in a progressive or cascading manner resulting in the loss of a large section of the roof envelope. These progressive failures of batten to rafter connections are a complex process influenced by the pressure fluctuations on the roof surface, the response of individual connections and the behaviour of the structural system as a whole. This study presents a method for examining load redistribution and progressive failure behaviour of batten to rafter connections in light framed structures. Nonlinear time history analyses were performed using a finite element model using fluctuating pressures determined from a wind tunnel study and connection properties determined from laboratory testing of connections under dynamic loads.

The phenomena of progressive failures are very common and important in geotechnical engineering. In this paper, a reliable prediction model is proposed to interpret the progressive failure phenomenon of roof collapse in deep tunnels using the functional catastrophe theory. The progressive collapse mechanisms and collapsing block shapes of deep circular tunnels under conditions of plane strain are investigated. The analytical solutions for the shape curves of the collapsing blocks of circular tunnels are derived based on the nonlinear power-law failure criterion considering variable dilatancy angle and detaching velocity. Moreover, criterions with variable dilatancy angle on progressive failure occurrence for deep tunnels are obtained. Then, the analytical predictions obtained in this paper are compared with experimental testing results, which indicate that the impacts of variable detaching velocity on the shape curves of the several continuous collapsing blocks should be considered to obtain more consistent prediction results with the corresponding experimental testing results.

Statistics for data collected on eastern Canadian clays (Champlain, Goldthwait, Tyrrell, and Laflamme marine clays and Barlow–Ojibway lacustrine clays) are computed and analyzed. These clays are divided into three groups: eastern Canadian marine clays, Champlain clays (as an important part of the first group), and Barlow–Ojibway lacustrine clays. The analysis reveals significant differences between eastern Canadian clays and Scandinavian clays. Some relationships proposed in the literature and based on plasticity index, liquidity index, and plastic limit are found to be inapplicable to eastern Canadian clays. On the basis of a proposed method for estimating the undrained shear strength of normally consolidated eastern Canadian marine clays, the overconsolidation ratio is found to be equal to the ratio of the in situ undrained shear strength to the estimated normally consolidated undrained shear strength. Key words: undrained shear strength, plasticity index, liquidity index, plastic limit, statistical evaluation, over-consolidation ratio, lacustrian clays.

We show the two types of a progressive failure by strain energy, U: strain energy released and accumulated propagations . We also have clarified the failure mechanism of strain energy accumulated propagation by model tests and theoretical examination of a simple model. As a result, we have been able to show that the external force condition classifies the strain energy accumulated propagation into the two types: forced and self-excited propagations . Only forced propagation occurs in soft ground, but both forced and self-excited propagations occur in hard ground. Verification tests have shown the validity of most of the examination results.

The increased significance and value of the multi- and interdisciplinary failure analysis field arises from the benefits incurred in terms of insurance costs, quality improvement, and prevention or minimization of environmental and safety risks. Especially in the chemical industry sector, the preventive role of failure analysis is of paramount importance, since the criticality and risk of an unfolding failure event provides a potential of huge safety and/or environmental hazards (chemical accidents, explosions, environmental-type leakages, etc.). Progressive-type failures are considered as the most insidious damage mechanisms which are very often difficult to detect and predict. Aggressive service conditions prevailing in chemical process plants, such as elevated temperature and pressure and corrosive environments, stretch the safety operating limits of engineering materials and components at challenging levels of endurance and reliability. The current chapter presents the investigation methodology of characteristic failures of chemical and process plants’ components, based mainly on case history investigation approach. A brief introduction addresses the progressive failure modes, focusing mainly on creep and stress corrosion cracking (SCC) in special steel structural members. Next, the results of the investigation of two respective case histories are thoroughly analyzed and discussed. The evolution of creep damage is presented in the case of a steel pipe operating in a power plant together with the discussion of the influence of operation parameters. The SCC mechanism is addressed through the catastrophic failure of a stainless steel screen (grid) used in a naphtha production unit in petrochemical industry. Visual inspection, optical microscopy, and scanning electron microscopy coupled with energy dispersive X-ray microanalysis were used as the principal analytical techniques for the case history failure investigation.

The shear modulus and hysteretic damping of three sensitive clays from the sediments of Champlain Sea were investigated using a combined triaxial simple shear apparatus. The tests were conducted on undisturbed samples and were carried out on a wide range of shear strains from about 0.001% to 1%. The values of the small-strain shear modulus of the tested clays were further confirmed through a series of piezoelectric ring actuator tests. Although the shear modulus and damping ratio of the sensitive eastern Canadian clays follow some classic literature models, the results show that the examined clays exhibited more linear behaviour. Such behaviour may be attributed to their highly structured nature compared to other clays. The compilation of available data on the shear modulus and damping ratio of several sensitive eastern Canadian clays confirmed this trend and showed that some literature models might not be representative.

Preliminary synthesis of detailed investigations of spreads that occurred in Canadian sensitive clays is presented. A thorough description of these landslides, including their final geometry, failure surface, and soil conditions in which they occur is given. Observation of debris morphology leads to the conclusion that horsts and grabens are resulting from active failure in the soil mass, dislocation, translation and subsidence in the remoulded shear zone below with no significant rotation. Failure surface forming during these landslides is close to the horizontal and generally starts near the toe of the slope. It is proposed that spreads results from (i) a failure surface being initiated and transmitted in an intact soil by progressive failure, followed by (ii) the dislocation of the above soil mass in horsts and grabens.

A new method is proposed to simulate progressive failure processes in heterogeneous brittle materials such as concrete, ceramics, rocks etc., by considering the time-dependence of stress redistributions induced by local break... | Find, read and cite all the research you need on Tech Science Press

A simplified method validated by centrifuge tests is developed to estimate both the deformation and stability of soft ground improved by piles during the rapid construction of embankments. Furthermore, this method, which considers pile-soil interaction, is adopted to investigate the failure mechanism and performance of piles. It is determined that piles embedded in a stiff stratum may be subjected to a dual bending failure. The first failure may occur at the soft-stiff interface because of the embedment effect of the stiff stratum, while the second failure may take place at the upper part of the piles due to the inflexion effect of soft ground movements. A progressive bending failure of piles may also occur as the maximum bending moment of each pile varies with the pile location. The progressive failure could propagate from the piles beneath the embankment toe towards the embankment centre. In addition, the location, stiffness, and fixity of piles have a significant influence on the stability of soft ground. The piles beneath the embankment toe are key piles, and increasing the stiffness and enhancing the embedment of these piles could efficiently ensure the stability of soft ground.