Tunnel Squeezing Deformation Control and the Use of Yielding Elements in Shotcrete Linings: A Review

Shotcrete lining shows high resistance but extremely low deformability. The utilization of yielding elements in shotcrete lining, which leads to the so-called ductile lining, provides a good solution to cope with tunnel squeezing deformations. Although ductile lining exhibits great advantages regarding tunnel squeezing deformation control, little information has been comprehensively and systematically available for its mechanism and design. This is a review paper for the purpose of summarizing the development history and discussing the state of the art of ductile lining. It begins by providing a brief introduction of ductile lining and an explanation of the importance of studying this issue. A following summary of supporting mechanism and benefits of ductile lining used in tunnels excavated in squeezing ground conditions is provided. Then, it summarizes the four main types of yielding elements applied in shotcrete lining and introduces their basic structures and mechanical performances. The influences of parameters of yielding elements on the supporting effect are discussed and the design methods for ductile lining are reviewed as well. Furthermore, recommendations for further research in ductile lining are proposed. Finally, a brief summary is presented.

Old growth forests and large old trees as critical organisms connecting ecosystems and human health. A review

Old forests containing ancient trees are essential ecosystems for life on earth. Mechanisms that happen both deep in the root systems and in the highest canopies ensure the viability of our planet. Old forests fix large quantities of atmospheric CO2, produce oxygen, create micro-climates and irreplaceable habitats, in sharp contrast to young forests and monoculture forests. The current intense logging activities induce rapid, adverse effects on our ecosystems and climate. Here we review large old trees with a focus on ecosystem preservation, climate issues, and therapeutic potential. We found that old forests continue to sequester carbon and fix nitrogen. Old trees control below-ground conditions that are essential for tree regeneration. Old forests create micro-climates that slow global warming and are irreplaceable habitats for many endangered species. Old trees produce phytochemicals with many biomedical properties. Old trees also host particular fungi with untapped medicinal potential, including the Agarikon, Fomitopsis officinalis, which is currently being tested against the coronavirus disease 2019 (COVID-19). Large old trees are an important part of our combined cultural heritage, providing people with aesthetic, symbolic, religious, and historical cues. Bringing their numerous environmental, oceanic, ecological, therapeutic, and socio-cultural benefits to the fore, and learning to appreciate old trees in a holistic manner could contribute to halting the worldwide decline of old-growth forests.

Analysis of the umbrella-type reflector opening process on a stand with an active gravity compensation system

During the verification of the functioning of the transformed structures in ground conditions, it is necessary to minimize the effect of gravity in order to exclude the occurrence of additional loads on the hinge assemblies and opening mechanisms. To perform this task, when testing a transformable umbrella-type reflector, stands with an active gravity compensation system are used, in which the gravity compensation force is applied to each spoke of the reflector. However, when compensating for the gravity spokes of the reflector, the fixing point of the suspension cable does not coincide with the center of mass of the spoke, which leads to the appearance of additional moments of forces acting on the suspended structure. Therefore, as an object of research, a part of the reflector was considered, consisting of a spoke, with cords of a formforming structure attached to it and a mesh. A 3D model has been developed, using which the positions of the center of mass of the structure under consideration were determined in the key phases of the reflector opening. A computational analysis of the driving forces and moments acting on the structure in the process of disclosure is carried out. The degree of influence of the suspension point position on the inaccuracy of gravity compensation has been established. The results of the analysis presented in the article can be used as initial data for the development of an algorithm for the operation of an active gravity compensation system, which will be able to take into account the position of the suspension point and the center of mass of the structure relative to the axis of rotation of the spoke during the opening of the reflector, by changing the gravity compensation force.

Prediction of Subsidence during TBM Operation in Mixed-Face Ground Conditions from Realtime Monitoring Data

The prediction of settlement during tunneling presents multiple challenges, as such settlement is governed by not only the local geology but also construction methods and practices, such as tunnel boring machine (TBM). To avoid undesirable settlement, engineers must predict the settlement under given conditions. The widely used methods are analytical solutions, empirical solutions, and numerical solutions. Analytical or empirical solutions, however, have limitations, which cannot incorporate the major causes of subsidence, such as unexpected geological conditions and TBM operational issues, among which cutterhead pressure and thrust force-related factors are the most influential. In settlement prediction, to utilize the machine data of TBM, two phases of long short-term memory (LSTM) models are devised. The first LSTM model is designed to capture the features affecting surface settlement. The second model is for the prediction of subsidence against the extracted features. One thing to note is that predicted subsidence is the evolution of settlement along TBM drive rather than its maximum value. The proposed deep-learning models are capable of predicting the subsidence of training and test sets with excellent accuracy, anticipating that it could be an effective tool for real-world tunneling and other underground construction projects.

Phenological traits of red amaranth varieties with a high content of amaranthine cultivated in open fields of Moscow region

The article focuses on phenological features of amaranth varieties grown in open fields as a reaction to variability of weather conditions in the Moscow region. Amaranthine is one of the promising compounds found in red-colored amaranths. It refers to a class of betalain pigments. The study revealed growth stages defined by the highest content of amarantine per plant and analyzed accumulation of the pigment in amaranth leaves and inflorescences. Phenological observations of introduced plant species under new conditions are important and determine their resistance to adverse environmental factors, ability to produce high quality fruits and seeds, and potential for cultivation. During the introduction of new amaranth varieties, the most adapted forms were selected for the conditions of the Non-Chernozem zone of the Russian Federation in 2013-2016. The studied Russian and Ecuador varieties were divided into 4 groups depending on the growth period (from germination to seed maturity). Analysis of phenological traits of plants confirmed that period of amaranth development did not depend on the variety, except the fourth stage of late-ripening cultivars - Don Pedro and Eku 17020, dependent on weather conditions. Being dependent on weather conditions, the vegetative growth period turned to be the most stable. Late cv. Eku 17020 did not form mature seeds in open ground conditions, which is explained by its origin (Ecuador). In the present study we identified growth stages when plant raw materials had the highest dye content in red-leaved amaranth varieties (Valentina, Don Pedro and Fakel). We also considered the perspective of cultivation of green-leaved varieties with red inflorescences - Pamyati Kovasa and Eku-17020 - as sources of biologically valuable compounds in the Moscow region.

Groundwater Lowering for Construction of the Kilsby Tunnel – Geological and Geotechnical Interpretation

The Kilsby Tunnel, constructed in the 1830s, faced severe problems when a section of the tunnel, almost 400 m long, encountered unstable ‘quicksand’ conditions. The engineer for the project, Robert Stephenson, developed an extensive groundwater lowering scheme, unique for the time, using steam engines pumping from multiple shafts, to overcome the quicksand. Modern geological information indicates most of the tunnel was in Middle Lias bedrock, but the ‘quicksand’ section passed through a buried channel of water-bearing sand of glacial origin. In the early 19th century the impact of glacial processes on British geology was not widely accepted and, based on contemporary geological knowledge, Stephenson’s problems appear to be genuine unforeseen ground conditions, not predicted by his experienced advisers. It seems just random chance that trial borings missed the buried channel of sand. The work at Kilsby was two decades before Darcy’s law established the theoretical understanding for groundwater flow, and 90 years before Terzaghi’s effective stress theory described how reducing pore water pressures changed ‘quicksand’ into a stable and workable material. Despite the lack of existing theories, Stephenson used careful observations and interpretation of groundwater flow in the ‘quicksand’ to navigate the tunnel project to a successful conclusion.

An Operating Model for an EPB Shield TBM Simulator by the Correlation Analysis of Operational Actions and Mechanical Responses

This study reports on the development of an operating model for an EPB Shield TBM simulator by the correlation between operating parameters. First, four main operating parameters required for excavation are analyzed, then multiple regression analysis estimates their requirements depending on the ground conditions and the TBM’s specifications. Further multiple regression analysis then determines the interactions between six operational actions and ten mechanical responses. Operating procedures are established, and interlock and warning alarm systems are designed for use in the operating model. Lastly, several simulations were tested for the operating model of the TBM simulator under various conditions.

Development of a method for obtaining healthy mini-tubers of potatoes of the Yubilyar variety using a humic preparation from peat

The influence of various nutrient medium compositions on the growth of potato plants during in vitro cultivation and the possibility of using biological fertilizer from peat in different concentrations to improve the adaptation of plants to growing in ground for the development of a method for obtaining healthy mini-tubers of potatoes of the Yubilyar variety were studied. The influence of various nutrient medium compositions on the height, biomass, intensity of rhizogenesis, the number of internodes of improved potato micro-plants, as well as humic fertilizer from Humostim peat on the survival rate and height of potato plants when adapting it to ground conditions is analyzed. Taking into account the data obtained, as well as the cost of the studied variants of the medium, the optimal medium for growing potato micro-plants in laboratory conditions in vitro is a nutrient medium with a content of mineral components 1/3 from the norm. The use of humic preparation from peat Humostim in a concentration of 0.001% caused an acceleration of plant growth and an increase in their height, and this concentration is recommended for use.