3G Consulting Engineers (Czechia)

In at least two out of the three recent major failures of tailings dams, two in Brazil and one in Australia, where incipient failure due to other causes has been evident, the occurrence of small earthquakes or mine blasts immediately prior to the failure has been essentially ruled out as the principal trigger. This is in accord with the widespread belief that very short period / higher frequency motions are not “seen” by large earth structures. That may be true in many cases, but if there is an incipient failure due, for instance, to uncontrolled seepage, piping and erosion, the characteristic dimension of that feature will be much smaller and it is possible, even likely, that high frequency motions can impact the potentially unstable local structure and trigger a larger progressive failure. This phenomenon is illustrated with a simple example. The importance of correctly modeling progressive failure is also addressed.

An institution of higher education recently decided to relocate and repurpose several of their existing dormitories to allow for construction of new dormitories. The three-story dormitories generally consist of unreinforced hollow masonry foundation walls, with reinforced-concrete footings. The building relocations required excavation beneath each building to provide clearance for the main jacking beams and cross beams to be inserted below the buildings. The building mover successfully transported the first two dormitories. During the third building relocation, the general contractor (GC) found the east foundation wall at one of the dormitories was reinforced concrete, rather than hollow masonry. The GC engaged a saw-cutting contractor to core access holes to insert the cross beams to lift the structure and then saw cut a horizontal separation joint through the east foundation wall of this dormitory above the line of core holes. After saw cutting the reinforced-concrete east foundation wall and excavating immediately adjacent to the east foundation wall footing below the bottom of footing, the east foundation wall at the third dormitory experienced a bearing capacity failure, which required emergency stabilization and shoring of the building. The failure caused differential settlement of the footing along the east side of the third dormitory, and large cracks developed in both the reinforced-concrete foundation wall and the hollow-masonry exterior walls above. This paper provides an overview of the project and discusses the causes of the failure and the emergency building stabilization.

The calcareous tubes inhabited by some polychaetes (some Serpulidae and the sabellid Glomerula) which are adapted to live sticking in soft ground, starting from the Permian, represent widespread but widely neglected and understudied substrates for domichnial bioerosion. Serpulids can be considered small macrofauna. However, due to the thinness of serpulid tubes, borings in them are sized in the order of 0.01–0.9 mm in diameter and thus rather considered micropaleontological objects. Extensive and methodologically broad search (vacuum castings studied at SEM; micro-computed tomography) for and study of borings in these specific substrates was performed on material from the Cenomanian of Le Mans area (France) and the Cenomanian and Turonian of the Bohemian Cretaceous Basin (Czechia). It shows that the bioerosive traces can be assigned to the existing ichnogenera Rogerella, Trypanites, Entobia, Maeandropolydora, and Iramena. Somewhat surprising is the frequency and disparity of dwelling borings. Several clues, especially in the more abundant ichnogenera Rogerella, Trypanites, and Entobia, support the hypothesis that the tracemakers of these borings adapted to the small size of their substrates by necessarily staying very small by themselves but nevertheless living to adulthood.

The paper describes the behavior of ternary gypsum-based composites, especially the changes of properties caused by the influence of moisture. The ternary gypsum-based mortar, composed of gypsum, hydrated lime, different types of pozzolan (silica fume, granular blast slag, and brick powder), and standard sand was investigated. Pozzolans in the mixture react with hydraulic lime and form CSH phases in the material. The presence of these phases improves the resistance of gypsum against the moisture. The way of samples’ storage affects the development of materials structure and properties of gypsum-based mortars. Therefore, samples were stored in two different environments (laboratory conditions and underwater) for a period of 360 days. The basic physical and mechanical properties of samples stored in the laboratory environment and under the water are compared. The comparison of the TG curves, based on the samples of different ages was carried out. The storage in the water has the most significant impact on the properties of all materials, especially on mechanical properties. While the strength of pure gypsum mortar, stored in the water, decreased significantly, and after one year in the water environment, the samples were nearly destroyed, the samples with pozzolan admixtures revealed the improvement of mechanical properties, when stored in water.

Abstract We analyze a suspended pipe with the application to offshore pipelaying and suspended production risers. Basic equations from the planar theory of elastic rods are reduced to a second-order ordinary differential equation with special end conditions that is solved numerically. Dimensionless results are given for the maximum curvature in the sag portion of the pipe and the slope angle at the upper end of the pipe in the absence of hydrodynamic forces. Both a rigid and a compliant seafloor are treated. We find that tension is highly effective in limiting curvature. A equation is found for the applied tension at the upper end of the pipe. Our results are intended for preliminary design studies that can be followed by more sophisticated analyses.

The operation of a hydro power project in North Turkey started in 2015, included the 12km long headrace tunnel. An 8km long lower tunnel section was excavated by double shield TBM technology with 8.7m ID. Due to problems with the mechanised excavation, a 4km long upper tunnel section was excavated conventionally by the Drill and Blast method with single shell lining generated from fibre reinforced sprayed concrete and rock bolts. Significant operational problems were observed in September 2016. The flooded tunnel was investigated by underwater Remotely Operated Vehicle which indicated significant collapses. Operation of the power station had to be stopped and water from a supply dam at the headrace tunnel inlet had to be discharged to enable dewatering and inspection of the tunnel. Consequent investigation revealed three major collapses and a considerable variety of other damages in the D&B section of the tunnel. Repair and strengthening of the tunnel was completed in October 2017.

Abstract Hochfester Stahl S690 für Autobahnbrücken – Allgemeine Hinweise für die Bemessung und Konstruktion. Die Verwendung von hochfestem Stahl (HFS) S690 für Autobahnbrücken ist noch nicht weit verbreitet. Ein Forschungsprogramm hat die optimale Verwendung von HFS für Brücken untersucht. Für eine 21,5 m breite Autobahnbrücke mit einer typischen inneren Stützweite von 80 m und einem Stahlbetonüberbau mit zwei Plattenträgern wurde ein Konstruktionsvergleich nach Eurocode erstellt. Es wurden drei Entwürfe erstellt: Ausführung (A) mit Stahlsorte S355 NL, Ausführung (B) mit HFS S690 QL/QL1 und Ausführung (C), ebenfalls mit HFS S690 und Untersuchung verschiedener Gestaltungsmöglichkeiten durch Schweißnahtbehandlung zur Reduzierung von Ermüdungserscheinungen und mögliches Übertreffen der aktuellen Eurocode‐Vorgaben. Allgemeine Richtlinien für die Bemessung und Konstruktion von Autobahnbrücken mit HFS S690 sind enthalten.

The new section of the Prague metro V.A is located in the west part of Prague, between stations Dejvická and Motol Hospital. The new metro section is 6.2km long and has four new stations. Majority of the two running tunnels that are 6.2km long were excavated by two EPB (Earth Pressure Balance) shields (2 × 4.8 km), it was the first use of modern tunnelling machines in the Czech Republic. Surface settlement above the running tunnels caused by the EPB shields was regularly monitored. The following paper is focused on an evaluation of the mentioned surface settlement using a volume loss. Consequently, numerical modelling of various cross-sections was executed. Modelling was realised by a finite element method in 2D, using the software Plaxis. Two different approaches were applied for modelling of the 3D effect in 2D. Important parameters M<em><sub>stage</sub> and C<sub>ref</sub></em> were derived for the selected cross-sections by back analyses (comparison of the numerical modelling results with the results of monitoring). The results of realised numerical modelling and the volume loss evaluation can be used for a preparation and realisation of similar tunnels in similar geology (for example, construction of the Prague metro line D, which will probably also be excavated by the EPB shields).

Flat glass panels are in use since the time of the Roman Empire. In the ruins of the city of Pompeii, destroyed by the Vulcan Vesuvius in 79 DC, a glass panel in a bronze frame of 300 × 600 mm was found. In this article we describe a mayor improvement in the structural behaviour of glass panels by making the glass curved, or more accurately, corrugated. Both the in- and out-plane loading meet far more resistance against deformation, and the corrugated glass panels have a largely increased bearing capacity with the same thickness of glass the flat panel has. Also architecturally the appearance of a corrugated glass panel in facades is far more appealing.