Применение статистического метода планирования для моделирования прогнозируемых параметров асинхронных двигателей

Рассматривается прогнозирование параметров асинхронных двигателей методом статистической экстраполяции. Для объединения данных по различным типоразмерам предлагается применение метода статистического планирования, позволяющего получить модель прогнозируемого параметра в зависимости от трех переменных. Точность построенных таким образом моделей является достаточной

The influence of the two-component grout on the behaviour of a segmental lining in tunnelling

Filling material is present around the segment lining when a shielded Tunnel Boring Machine is used to excavate a tunnel. The two-component grout is becoming lately one of the most used filling materials. Its mechanical properties evolve over time. Unfortunately, there are not many studies in the literature on the specific mechanical characteristics of these materials. This work presents the results obtained from an extensive laboratory test campaign that allowed to fully characterize the two-component filling material during the setting period. In particular, the values of the stiffness and resistance parameters were obtained over time, where uniaxial compression tests and oedometer tests were carried out. A detailed study of the effect of the presence of the filling material on the behavior of the support system (segmental lining + filling material) was developed for two of the most widespread analytical methods for the analysis of the behavior of tunnels and structures of support: the convergence-confinement method and the Einstein and Schwartz method. Subsequent parametric analyses made it possible to consider the variability of the influencing parameters within the typical variability ranges obtained from the laboratory test campaign or known from the available scientific literature. From the study carried out, it was possible to note that it is necessary to consider the presence of the filling material in the evaluation of the stiffness of the support system, when using the convergence-confinement method to estimate the loads acting on segmental lining. In this regard, it is necessary to have a reliable estimate of the elastic modulus of the filling material in the period of loading of the segmental lining. On the other hand, the presence of the ring of filling material is negligible when evaluating the state of stress of the segmental lining with specific methods capable of considering the rock-support interaction. In particular, adopting the Einstein and Schwartz method, it is possible to define the bending moments and normal forces acting in the support structure, referring to the stiffness parameters of the segmental lining alone

Experimental Evidence of the Effectiveness and Applicability of Colloidal Nanosilica Grouting for Liquefaction Mitigation

AbstractThe low viscosity and the ability to control solidification rate make colloidal nanosilica grout an excellent ground-improvement solution which is functional for different engineering purpo..

Experimental tests and fatigue strength assessment of a scotch yoke valve actuator

Abstract Aim of this work is the fatigue assessment of a main component, termed scotch yoke, of a valve actuator used for oil & gas, power and chemical industries, in order to comply with its heavy-duty applications. To do this, full-scale specimens of the scotch yoke made of structural steel have been fatigue tested under nominal axial loading. All specimens have been tested under stress-relieved conditions by adopting a nominal load ratio R=-1. After experimental tests, the fatigue crack paths have been analysed by means of liquid penetrant inspections. The fatigue strength class of the considered scotch yoke has been determined by statistically re-analysing the experimental results, expressed in terms of range of the nominal applied load, and it has been compared with the design condition required by the relevant European Standard, EN 15714-3/4. Finally, two methodologies for fatigue strength assessment of the considered scotch yokes have been proposed, which are based on experimental fatigue data derived from smooth or sharp V-notched specimens, respectively, made of the same yoke material. The assessment capability of the proposed methodologies has been evaluated and discussed by comparing theoretical estimations with the experimental fatigue results of the scotch yokes

Evaluating the potentiality of X-ray tomography on the quality assessment of grouted soils

The final authenticated version is available online at https://doi.org/10.1007/978-3-031-12851-6_1.Grouting is a technique used to improve the engineering properties of soils and rocks. Grouting techniques are classified under different criteria: injection method used, type of grout material injected, typical application, and the sequence of construction. The best-known criterion is the mode of entrance or admission of grout into the soil or rock. It is possible to identify therefore several grouting techniques: compaction, fracture, jet/mixing and permeation. The function of penetration grouting is to reduce the permeability of the soil or rock and/or increase the strength and density. In order to avoid displacements or piston effects, permeation grouting shall be carried out at carefully controlled pressures and flow rates, using appropriate grouts. Several tests have been performed, with a laboratory injection device, on four soil mixtures with different permeability values (kw values between 10–4 and 10–7 m/s) and the same void ratios, injected with a colloidal silica. Indirect tests (X-ray CT-scans) and destructive tests (unconfined compressive strength tests) were performed to assess the injection effectiveness and the grade of mechanical improvement achieved. The chosen binder was able to penetrate in low permeable soils with kw values of 10–7 m/s. Results are valuable for contractors and designers involved in the consolidation of soils where kw values are known.Postprint (author's final draft

Permeation grouting of an upstream tailing dam: a feasibility study

The presence of potentially liquefiable deposits in tailing dams represents a serious hazard, as is now increasingly clear that liquefaction triggering may occur in unanticipated ways. For legacy dams in which this hazard is already present, intervention alternatives are sought to mitigate the associated risks of liquefaction failure. One interesting possibility is to use targeted ground improvements of tailings within the structural zone of the dams, so that they become nonliquefiable. Liquefaction remediation technologies that are relatively gentle would be preferable, as the possibility of triggering liquefaction during the ground improvement operation itself cannot be lightly discarded. Permeation grouting is a classical soil improvement technology that has been renovated with the apparition of new permeating agents, such as colloidal silica suspensions (CS). Permeation grouting of CS consists in low-pressure injections leading to CS treated soils characterized by a significantly reduced liquefaction potential. CS grout has a complex rheology that is best described by a Bingham model whose parameters change in time. This paper presents design tools that incorporate this complexity and allow both a safer and more realistic design of permeation treatments. As an application example, we study a case based on the Merriespruit tailing dam, which failed by static liquefaction. It is concluded that CS permeation could realistically offer a potential solution to reduce instability risk of some tailing storage facilities (TSF).Postprint (published version

Exploring the mechanical response of low-carbon soil improvement mixtures

As society moves towards decarbonisation, it is important to assess the hydromechanical behaviour of binders that could offer a low-carbon alternative to Portland cement in ground improvement technologies. This work considers two such alternatives: one still largely unexplored (metakaolin-based geopolymers) and a better known one (colloidal silica). Results from unconfined compressive strength, permeability tests, undrained monotonic and cyclic triaxial tests on granular soils (sand and silty sand) treated with those two binders are presented and discussed, emphasizing similarities and differences with the response of similar soils treated with other conventional and unconventional binders. Effects of silt content, curing conditions and soil/binder ratios are examined. Both colloidal silica and metakaolin-based geopolymer significantly improve the mechanical properties of the treated soils, although the geopolymer results in a stronger and stiffer material. Both treatments reduce much the permeability of the treated soil, but the reduction achieved with colloidal silica is larger.Peer ReviewedPostprint (author's final draft

P-wave velocity measurements for preliminary assessments of the mineralization in seafloor massive sulfide mini-cores during drilling operations

Highlight • It is important to develop systems able to detect and classify mineralized zones from waste materials while drilling deep-water; • Seismic P-wave velocities (Vp) were measured on 40 SMS and unmineralized mini-cores; • The porosity was back-calculated from Vp; • The results were compared with electrical resistivity measurements; • Using Archie’s Law, it is possible to observe that metallic conduction exists. Abstract Deep-sea mining exploration for seafloor massive sulfide (SMS) deposits is currently increasing. At present, most exploration activities are surficial and use indirect methods to identify potential sites and perform first assessments. For a proper resource estimate, however, drilling is inevitable. By using seabed drill rigs, exploration costs can be reduced considerably. SMS deposits are normally found at depths between 1000 and 4000 m and in order for deep sea mining to be implemented, reliable technologies are needed. Additionally, the development of geophysical systems that can detect and classify mineralized zones from waste materials while drilling could decrease costs and speed up offshore operations by limiting the amount of drilling of unmineralized materials. This paper shows how the physical properties of SMS can be used to discriminate between host rocks and mineralization. Seismic P-wave velocities (Vp) were measured on 40 SMS and unmineralized mini-cores. By back-calculating the porosity from Vp, comparing the results with electrical resistivity measurements, and using Archie's Law, it is possible to observe that metallic conduction exists. For deep-sea mineral exploration, the combination of seismic tests, electrical resistivity and magnetic susceptibility could support the preliminary discrimination of mineralized samples in the cores while drilling at the seafloor