Study on dynamic strength and liquefaction mechanism of silt soil in Castor earthquake prone areas under different consolidation ratios

Under the Castor earthquake, there is a risk of liquefaction instability of saturated tailings, and the evolution of dynamic pore pressure can indirectly reflect its instability process. Before applying dynamic loads, the static stress state of soil is one of the main factors affecting the development of soil dynamic strength and dynamic pore pressure, and there are significant differences in soil dynamic strength under different consolidation ratios. This paper conducted dynamic triaxial tests on saturated tailings silt with different consolidation ratios, and analyzed the dynamic strength variation and liquefaction mechanism of the samples using the discrete element method (PFC3D). The results showed that 1) as the Kc′ gradually increased, and there was a critical consolidation ratio Kc′ during the development of the dynamic strength of the sample. The specific value of Kc′ was related to the properties and stress state of saturated sand. The Kc′ in this research was about 1.9. When Kc < 1.9, dynamic strength was increased with the increase in Kc; when Kc > 1.9, dynamic strength was decreased with the Kc. 2) Under the impact of cyclic load, when samples were normally consolidated (Kc =1), the pore water pressure would tend to be equal to the confining pressure to cause soil liquefaction. In the case of eccentric consolidation (Kc > 1), the pore water pressure would be less than the confining pressure, thus, the soil liquefaction would not be induced, and the pore pressure value would decrease with the increase of consolidation ratio. This paper provides engineering guidance value for the study of dynamic strength and liquefaction mechanism of tailings sand and silt in Castor earthquake prone areas under different consolidation ratios

Study on optical fiber multi-parameter sensor

Based on the principle of fiber Bragg grating detection,an optical fiber sensor for detecting wind speed and temperature and humidity in underground space was designed.The designed optical fiber wind speed sensor was based on the thermal flow detection method,which has high sensitivity to low wind speed.For the speed rising from 0 to 0.5 m/s,the wavelength variation is about 800 pm.For the demodulator with sensitivity of 1 pm,the speed resolution is 0.7 mm/s.Fiber optic humidity sensor was fabricated by uniform surface coating of FBG element in polyimide solution,and detection sensitivity of 4.2 pm/% RH was achieved with accuracy less than ± 3% RH

The interaction between local melting and helium bubble in radiated aluminium under dynamic tension at high temperature and strain rates

Materials exposed to extreme radiation environments (e.g., nuclear devices) accumulate substantial defects, such as helium (He) bubbles. These defects can alter material properties, including melting behavior, which has not been intensively explored. Here, the melting process and the He bubble evolution in aluminium under dynamic tension at high temperature and strain rates were investigated via molecular dynamic simulations. We found that the melting process contains slow premelting and sequential fast local melting at relatively lower strain rates (106 ∼ 108 /s). The rapid growth of the bubble promotes local melting, which in turn facilitates the migration and shrinkage of the bubble. The underlying microscopic mechanisms for the interplay between the bubble and local melting have also been uncovered. Such interaction becomes weak at high strain rates (109 ∼ 1010 /s). Homogeneous melting occurs directly and spontaneously throughout the sample, and local melting around the bubble becomes inconspicuous. The evolution process of the bubble gets simple, characterized by continuous growth without shrinkage or migration. Furthermore, damage development is dominated by the growth of the He bubble, which occurs after the sample is nearly completely melted at lower strain rates while it happens concurrently with melting at high strain rates