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Brittleness is an important parameter to evaluate the performance of rock engineering. A scientific and reasonable brittleness evaluation method is of great significance to theoretical research and the engineering practice of rock mechanics. In view of the existing statistical constitutive models of rock based on the Weibull distribution being able to express various constitutive behaviors well, such as brittleness, plasticity, strain softening, this paper wants to determine rock brittleness from constitutive models. First, the parameter m, which can effectively reflect the overall characteristics of the rock stress-strain curve, and the parameter δ, which can reflect the post-peak characteristics, are selected. Then, a brittle evaluation method based on rock statistical damage constitutive parameters is proposed, and the brittleness index Bm (Bm = m·δ) is established. The feasibility is verified by the testing data of granite, sandstone and marble under different conditions. The results show that the brittleness of those hard rocks decrease with the increasing of confining pressure. For confining pressures of 5 MPa and 15 MPa, the brittleness of granite under triaxial unloading test is greater than that under triaxial compression test. The calculation results quantitatively reflect the brittle characteristics of sandstone, marble and granite in the test. Compared with the existing representative brittleness indexes, it is found that the brittleness index Bm can effectively reflect the characteristics of rock brittleness decreasing with increasing confining pressure and enhancement under unloading stress path. This paper provides a way to evaluate rock brittleness from the perspective of a constitutive model, which is helpful to enrich our understanding of rock brittleness.

Within an eight-year period, starting in September 2011 and ending in July 2019, Shanghai Electric-KSB Nuclear Pumps & Valves Co., Ltd (hereinafter called SEC-KSB) has managed to develop a new pump type that can be used as reactor coolant pump (hereinafter called RCP) in generation 3 pressurized water reactor design. Wet winding motor reactor coolant pump (pump type RUV 650–870) is a customized and especially designed to meet the high safety criteria of generation 3 nuclear power plant, which is a hermetically sealed (without shaft seal system) type pump, and it is first time used as reactor coolant pump in pressurized water reactor in the worldwide. Started with the pump commissioning test in December 2014, total eight times high temperature and high-pressure full load testing had to be carried out in order to eliminate design or manufacturing flaws. In early 2019 within three months of intensive testing, under all the specified design transient scenarios, the RUV 650-870 pump had successfully passed all the qualification test items. On July 31. 2019 an expert qualification meeting was organized by China Machinery Industry Federation and China General Machinery Industry Association, the qualification committee states that the development of first set wet winding motor reactor coolant pump is successful in the worldwide, and the pump technical performance meet the requirements of the equipment specification, test specification and related industry standards, the RUV 650-870 pump can be used for nuclear power plant projects. On January 2022, the first production pump was delivered to nuclear power plant.

会議名/ Conference Name : APSSRA2020, 回次 / Conference Sequence : 7, 開催期間 / Conference Date : October 4-7, 2020, 開催会場 / Conference Venue : The University of Tokyo, 開催地 / Conference Place : Tokyo, 開催国 / Conference Country : JPN

This paper summarizes the main factors affecting the large deformation of soft rock tunnels, including the lithology combination, weathering effect, and underground water status, by reviewing the typical cases of largely-deformed soft rock tunnels. The engineering geological properties of the rock mass were quantified using the rock mass block index (RBI) and the absolute weathering index (AWI) to calculate the geological strength index (GSI). Then, the long-term strength σr and the elastic modulus E0 of the rock mass were calculated according to the Hoek–Brown failure criterion and substituted into the creep constitutive model based on the Nashihara model. Finally, the creep parameters of the surrounding rock mass of the Ganbao tunnel were inverted and validated by integrating the on-site monitoring and BP neural network. The inversion results were consistent with the measured convergence during monitoring and satisfied the engineering requirements of accuracy. The method proposed in this paper can be used to invert the geological parameters of the surrounding rock mass for a certain point, which can provide important mechanical parameters for the design and construction of tunnels, and ensure the stability of the surrounding rock mass during the period of construction and the safety of the lining structure during operation.

The diffuser of a reactor coolant pump was optimized using an orthogonal approach with numerical simulation to improve the pump hydraulic performance. Steady simulation was conducted by solving Reynolds-averaged Naiver-Stokes equations with the SST k-ω turbulence model using CFX code. The influence of the diffuser geometric parameters, namely, S, φ, α 4, b 4, δ 2, R t and R 4, on the pump performance were determined. L18 (37) orthogonal table was chosen for the optimization process. Best indicators were determined, and range analysis of energy losses, head, and efficiency at the rated condition was performed. Optimal parameters of the diffuser were S = 490 mm, φ = 36°, α 4 = 30°, b 4 = 200 mm, δ 2 = 20 mm, R t = 5 mm and R 4 = 565 mm. The final design was experimentally tested. Simulation results showed more remarkable performance than the experimental result. However, the numerical predictions and experimental results were consistent, validating the design procedure. Loading of the impeller and diffuser blades was analyzed to investigate the direct impact on the hydrodynamic flow field. The head was 14.74 m, efficiency was 79.6 %, and efficiency of the prototype pump was 83.3 % when the model pump functioned at the rated conditions. Optimization results showed that efficiency and head were improved at the design condition.