NATURAL PHENOMENA OF ENDOGENIC ORIGIN IN THE ARCTIC BASIN

The results of the study of the influence of the deep factor on the process of melting of the ice cover of the Arctic Ocean and the formation of dangerous natural phenomena are presented. The peculiarities of the structure of the earth’s crust contributing to the ice destruction are visualized based on the interpretation of anomalies of the magnetic field and gravity. Density and magnetic sections of the bottom structures are constructed taking into account seismic and seismological data. Two-dimensional density calculations of the Arctic crust density have been performed to detect fluid-saturated layers. Analysis of satellite observations of ice condition together with interpretation of gravity and magnetic data made it possible to identify natural phenomena of endogenous origin, caused by influence of thermo fluid flows of the earth’s crust. The study of annual and seasonal changes in the thickness of multiyear ice over the period 2007–2020 has shown that a decisive role in the thawing process is played by fluid-supplying channels of deep-seated fault zones. The role of an endogenous factor in the destruction of ice of different ages and in the emergence of dangerous phenomena in the areas of hydrate development has been revealed. This makes it possible to predict the localization of zones of variability in the thickness of multiyear ice, the nature of the destruction of its edges and reduce the risks of navigation.

MANIFESTATIONS OF MODERN FLUID DYNAMIC ACTIVITY OF THE NORTHERN CASPIAN SEA (GEOPHYSICAL DATA)

The paper presents analysis of geological-geophysical data, both from archives and collected in recent expeditions by Shirshov Institute of Oceanology, RAS (SIO RAS) together with satellite data. The interpretation shows modern rise of fluid dynamic activity on North Caspian. Based on summary of previous data, it is possible to recognize ryithmostratigraphic and seismostratigraphic complexes. Side sonar data shows many reflexing objects on the sea bottom. One of the most prominent features of Northern and Central Caspian is great number of pipe-like vertical bodies, they were discovered by SIO RAS expeditions with high-resolution seismic methods. These “pipes” go down beyond seismic section data. All specified seismic anomalies and bottom microrelief can be considered as evidence of vertical migration of gas and water via sediments and its escaping to water by gas and water grifons. Satellite images of North and Central Caspian show great amount of sliks and oil signs on the sea surface, and some of them present constantly on the same place, so it is possible to claim the sub-bottom fluid escape theory. The paper shows connection between bottom structures and grifon activity via satellite images (spatial-time grouping of oil slicks) of 2011–2019.

Fatigue Performance of Tunnel Invert in Newly Designed Heavy Haul Railway Tunnel

The Haoji railway in China is the longest heavy haul railway in the world, including 235 tunnels located along the 1837 km railway. With the increasing axle load of the new line and the basal deterioration of the existing heavy haul railway in China, studying the fatigue performance of the newly designed tunnel structure is essential. To study the coupling effect of the surrounding rock pressure and 30 t axle load train, in this study, we combined three-dimensional numerical simulation and three-point bending fatigue tests to investigate the fatigue performance of the basal structures. The results of numerical simulation indicate that the center of the inverted arch secondary lining is the position vulnerable to fatigue in the lower tunnel structures; the surrounding rock pressure performance exerts a stronger influence on the stress state of the vulnerable position than the dynamic train loads. The S–N formula obtained from the experiment showed that the fatigue life of tunnel bottom structures decreases with increasing surrounding rock pressure and dynamic load. In typical grade V surrounding rock and 30 t axle loads, fatigue failure will not occur in the newly designed tunnel bottom structures within 100 years if bedrock defects are lacking and pressure of surrounding rock is not excessive.

Hydraulic studies of bottom regulatory devices

Introduction. Accidents at underwater pipeline crossings lead to serious environmental consequences. The choice of the location of the pipeline junction made without accounting the general dynamics of the channel process, use of improper construction technology of underwater trenches and pipeline laying often result in their destruction, which are caused by erosion and pipe sagging. Existing methods for protecting the pipeline by soil or crushed stone filling, exposure embedding with sandbags, strengthening with flexible concrete mats and other materials are not always effective and, as a rule, are expensive. Materials and methods. The article considers a method of protection of the main pipeline against erosion by means of through bottom devices of various types to determine their efficiency. Velocities of the flow are measured behind the bottom obstacles at the flow axis at several points in depth using the microcomputer flowmeter/velocimeter. The measuring sections are located at distances of 1 to 10 of flow depths from the bottom obstacles. The near-bottom velocities at the height of the roughness protrusions are calculated according to the dependences suggested by V.N. Goncharov. Results. The article shows results of laboratory hydraulic investigations of a tray flow around four types of bottom obstacle models: solid flat wall, slotted flat wall, volumetric round-section obstacle of fixed synthetic strings and volumetric soft structure. All the studied design models cause a rearrangement of the velocity diagrams and a decrease of near-bottom velocities. However, only through-passing structures are suitable for sediment deposition behind the barriers. If the bottom velocities are reduced to values less than sediment-washing ones, sediments will be deposited behind the barriers at a certain relative distance determined in the work. Conclusions. The investigated models of through bottom structures showed themselves to be quite effective in reducing the near-bottom speed and depositing sediments at a certain distance behind them. The most effective is the “volumetric” construction, since it gives the greatest reduction in relative velocities at a certain relative distance.

Twenty-six years (1990–2015) of monitoring annual recruitment of the invasive zebra mussel (Dreissena polymorpha) in the Rideau River, a small river system in Eastern Ontario, Canada

We monitored the recruitment of young-of-year zebra mussels (Dreissena polymorpha (Pallas, 1771)) each autumn at 13 locations within four river reaches along the length (100 km) of the Rideau River, starting in 1990, the year of its discovery in that river, until 2015. Sampling was conducted on bottom structures of locks or on seasonally exposed substrate during autumn drawdowns conducted by Rideau Canal staff. Twenty-six years of monitoring zebra mussels in that river revealed a distinct and persistent upstream–downstream pattern, with highest densities occurring in the two downstream reaches. A “lake effect” was observed at Long Reach, where veligers have ideal conditions for larval development. Highest densities occurred in the mid-1990s, comparable with those reported in the Laurentian Great Lakes during peak invasion (200 000 to 500 000+ mussels/m2). Although the most upstream reaches of the river had low recruitment rates and low densities initially (0.01 to 10 mussels/m2), annual recruitment progressively increased to higher values (10 to 1000+ mussels/m2) because more veligers from the Rideau Lakes and the river headwaters were produced and drifted into the system. This study is unique because it provides a thorough understanding of the 26 years of invasion history of the zebra mussel in a small river system.

Experimental Investigations of Hydroelastic Effects on Loads During Flat Water Entry

Extensive water entry experiments were performed to identify the influence of elasticity on impact-induced loads acting of flat bottom structures. Two bodies were tested. One body was fitted with stiffened, rigid bottom plating; the other body, with thin elastic plating. Bottom pressures and forces acting on the flat bottom plating and impact-induced elastic bottom strains were measured. High-speed videos of water entry sequences were evaluated to investigate hydroelastic effects on air trapping.