Performance Analysis of Tunnel Boring Machines for Rock Excavation

The study takes into account different classes of tunnel boring machines (TBM), with the aim of identifying correlation models which are meant to estimate, at a preliminary design phase, the construction time of a tunnel and to evaluate the mechanical and operational parameters of the TBMs, starting from the knowledge of the tunnel length and the excavation diameter. To achieve this goal, first of all a database was created, thanks to the collection of the most meaningful technical parameters from a large number of tunnels; afterwards, it was statistically analyzed through Microsoft Excel. In a first phase, forecasting models were identified for the three types of machines investigated, separately for compact rocks (open TBM) and fractured rocks (single and double shield TBM). Then, the mechanical parameters collected through the database were analyzed, with the aim of obtaining models that take into account, in addition to the type of TBM, the geological aspect and the type of rock characterizing the rock mass. Finally, the validation of the study was proposed in a real case, represented by the Moncenisio base tunnel, a work included in the new Turin–Lyon connection line. The estimated values were compared with the real ones, in order to verify the accuracy of the experimental models identified.

Performance Analysis of Tunnel Boring Machines for Rock Excavation

The study takes into account different classes of tunnel boring machines (TBMs), with the aim of identifying correlation models which are meant to estimate, at a preliminary design phase, the construction time of a tunnel and to evaluate the mechanical and operational parameters of the TBMs, starting from the knowledge of the tunnel length and/or the excavation diameter. To achieve this goal, first of all a database was created, thanks to the collection of the most meaningful technical parameters from a large number of tunnels; afterward, it was statistically analysed through Microsoft Excel. In a first phase, forecasting models were identified for the three types of machines investigated, separately for compact rocks (open TBM) and fractured rocks (single and double shield TBM). Then, the mechanical parameters collected through the database were analysed, with the aim of obtaining models that take into account, in addition to the type of TBM, the geological aspect, and the type of rock characterising the rock mass. Finally, the validation of the study was proposed in a real case, represented by the Moncenisio base tunnel, a work included in the new Turin–Lyon connection line. The estimated values were compared with the real ones, in order to verify the accuracy of the experimental models identified.

Influence of anisotropy, tilt and pairing of Weyl nodes: the Weyl semimetals TaAs, TaP, NbAs and NbP

By means of ab initio band structure methods and model Hamiltonians we investigate the electronic, spin and topological properties of four monopnictides crystallizing in bct structure. We show that the Weyl bands around a WP W1 or W2 possess a strong anisotropy and tilt of the accompanying Dirac cones. These effects are larger for W2 nodes than for W1 ones. The node tilts and positions in energy space significantly influence the DOS of single-particle Weyl excitations. The node anisotropies destroy the conventional picture of (anti)parallel spin and wave vector of a Weyl fermion. This also holds for the Berry curvature around a node, while the monopole charges are independent as integrated quantities. The pairing of the nodes strongly modifies the spin texture and the Berry curvature for wave vectors in between the two nodes. Spin components may change their orientation. Integrals over planes perpendicular to the connection line yield finite Zak phases and winding numbers for planes between the two nodes, thereby indicating the topological character. Graphical abstract

Development and Research on the Vertical Center Diaphragm Method Applied in Shallow Tunnel Construction

As a common method applied in the construction of tunnels with Grade IV and Grade V surrounding rock, the center diaphragm (CD) method has the advantage of resisting the inward horizontal convergence of the tunnel. However, due to the small lateral earth pressure of the shallow tunnel, the curved center diaphragm would have an unstable stress state and cannot provide sufficient support to the surrounding rock. Based on the CD method, this study presents a vertical center diaphragm (VCD) method with an axisymmetric structure. The application condition of the VCD method relies on the comparison of the surface settlement and tunnel deformation with the two methods in different surrounding rock grades and buried depths by using a three-dimensional finite-difference code. Based on the Shenzhen Eastern Transit Expressway Connection Line Tunnel, which has six lanes of double lines, the deformation regularities and mechanical characteristics of the VCD method, including the surface settlement, tunnel deformation, internal force of the center diaphragm, surrounding rock pressure, and steel arch stress, are investigated by numerical calculations and a field comparative test. The results obtained in this study provide several suggestions for constructing shallow tunnels. Furthermore, the construction efficiency and economy of the VCD method are evaluated.

Method of selecting main parameters of smoothing devices for railway DC substation

The paper presents main clauses of a method for selecting main parameters of smoothing devices for railway direct current traction substation, which are intended for developing a state standard. The authors have created a list of required initial data for selecting parameters of smoothing devices. For each type of the connection line the authors have proposed optimal types of smoothing devices with the consideration for characteristics of direct current traction substations. As a result, they have determined the order of calculation of the main parameters of the smoothing device.

Remoção cirúrgica de sialolito em glândula submandibular: relato de caso

Introdução: A sialolitíase é a desordem mais comum das glândulas salivares acometendo principalmente a glândula submandibular e o seu ducto. Caracteriza-se pela formação de cálculos ou sialólitos no interior do ducto ou do próprio parênquima glandular. A etiologia pode estar associada ao pH alcalino e aumento da concentração de cálcio na saliva, além de fatores anatómicos como estenose ou diverticulação do ducto salivar. Objetivo: relatar um caso clínico de sialólito localizado no ducto da glândula submandibular, bem como discutir a literatura pertinente sobre o tema. Métodos: Paciente do gênero masculino, compareceu ao Hospital Geral de Areias com queixa de aumento em região de soalho bucal direito. Foram solicitadas radiografias panorâmica e oclusal e observou-se massa radiopaca de formato cilíndrico e alongado na região submandibular. A excisão cirúrgica foi realizada sob anestesia local. Paciente não apresentou complicações e retomou-se o reestabelecimento da patência do ducto e normalidade do fluxo salivar. Conclusões: A conduta mostrou-se eficaz no manejo da lesão através de remoção cirúrgica por acesso intrabucal. Estas desordens são facilmente diagnosticadas através do exame clínico e de imagem.Descritores: Glândula Submandibular; Soalho Bucal; Cálculos das Glândulas Salivares.ReferênciaRibeiro J, Mourão CF, Magacho LF, Albieiri F, Vicentis G, Fernandes O, et al. Tratamento cirúrgicos dos sialolitos gigantes das glândulas submandibulares: relato de dois casos. In J Sci Dent. 2016;22(46).Acevedo JAD, Trocino BS, Mercado HR. Sialolitiasis del conducto submandibular: reporte de un caso reporte de un caso. Rev Mex Cir Bucal Maxilofac. 2017;13(3):100-7.França DCC, Facio JC, Maia CMP, Monteiro AD, Carvalhosa AA, Moi GP et al. Sialolito no ducto da glândula submandibular: relato de casa. Connection Line. 2012;7:78-89.Landgraf H, Assis AF, Klüppel LE, Oliveira CF, Grabielli MAC. Extenso sialolito no ducto da glândula submandibular : relato de caso Rev Cir Traumatol Buco-Maxilo-Fac. 2006;6(2):29-34.Kim JH, Aoki EM, Rodriguez A, Cortes ARG, Abdala-Júnior R, Asaumi J, Arita ES. Comparison of the diagnostic performance of panoramic and occlusal radiographs in detecting submandibular sialoliths. Imaging Sci Dent. 2016;46(2):87-92.Tahher AA. The incidence and composition of salivary stones (sialolithiasis) in Iran: analysis of 95 cases—a short report. Singapore Dent J. 1990:14(1):33-5.Cho S, Han J, Kim J, Lee S, Jo J, Kim C et al. Removal of submandibular calculi by surgical method and hydraulic power with curved needle : a case report. J Korean Assoc Oral Maxillofac Surg. 2017;43(3):182-85.Pereira RS, Bonardi JP, Silva JR, Mourão CFAB, Souza FI, Pimentel RM. Remoção cirúrgica de sialolito no ducto da glândula submandibular : relato de caso. Arch Health Invest. 2017;6(4):185-88.Folchini S, Stolz AB. Sialolitos na glândula submandibular : relato de caso. Odontol ClínCient. 2016;15(1):67-71.Ogura I, Hayama K, Sue M, Oda T, Sasaki Y. Submandibular sialolithiasis with CT and scintigraphy : CT values and salivary gland excretion in the submandibular glands. Imaging Sci Dent. 2017;47(4):227-32.Alves NS, Soares GG, Azevedo RS, Camisasca DR. Sialolito de grandes dimensões no ducto da glândula submandibular. Rev Assoc Paul Cir Dent. 2014;68(1):49-53.Baurmash HD. Submandibular salivary stones : current management modalities. J Oral Maxillofac Surg. 2004;62(3)369-78.