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Four kinds of tri-axial shear structural yield stress is studied by controlling the pre-test consolidate degree and draining condition during the test. The results showed that draining condition influenced the tri-axial shear structural yield stress. When under the UU condition, structural characteristics appeared not clearly; when consolidated before testing and un-drained during test, only the undisturbed soil performed the structural yield stress; when draining during testing, the undisturbed soil showed the increased structural yield stress while the remolded soil could form certain structure. The impact of the draining condition on the structural characteristics is incurred by the change of the internal structure, which means that the draining condition have changed the arrangement and connection of the soil particles, then changed the soil structural properties.

Graphene oxide (GO) was modified by polyphenylvinylsiloxane (PPVS) through π-π conjugation interaction. The modified GO/PMMA nanocomposites were prepared via in situ bulk polymerization. The modification of GO was characterized by using Fourier transformed infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Thermal conductivity, thermal stability and mechanical properties of PMMA and its composites were investigated by using TG, heat conduction analysis, and three-point bending strength test, respectively. The results showed that PPVS modified GO was prepared through non-covalent interaction, and composites with non-convalent phase interfaces were also obtained. With the addition of GO-PPVS, the three-point bending strength of GO-PPVS/PMMA increased to about 68 MPa. GO wrapped by PPVS could not form thermal conducting networks at the percolation thresholds. The increasing amount of PPVS prevented the formation of thermal conduction network, and decreased the thermal conductivity of the composites. The thermal stability of the composites was influenced by three main factors, and the total effect of the three factors on thermal stability illustrated a negative trend.

Railway track and nearby structures in the vicinity of high-speed railway are exposed to low-amplitude small-strain vibrations as high-speed railway traffic construction activities arise. These low-level dynamic events can lead to a non-linear softening behavior of the “elastic” stiffness and a considerable amount of energy dissipation in soils with a gradually increasing strain. The modelling of these non-linear behaviours are an important to predict lifetime and serviceability of existing structures in the vicinity of high-speed railway. An objective of this study is to develop validated computational models that can be used to perform stiffness and damping characteristics of saturated clayey soils due to low-amplitude small-strain vibrations. This paper provides an insight in the normalized shear modulus G/Gmax and damping ratio D in relation with shear strain amplitude γ through free-vibration column test, and proposes a modified Davidenkov model.

This study examined the co-pyrolysis characteristics of low-rank coal (SJC) and direct coal liquefaction residue (DCLR) through thermogravimetric analysis coupled with Fourier transform infrared spectrometry. It also investigated the influences of different mass fractions of DCLR to SJC on the co-pyrolysis characteristics and release regulation of gas phase components. Results showed that with increasing DCLR content, coke yield initially decreased and then increased, but tar and gas yield reversed. Different addition of DCLR changed the composition of the pyrolysis gas in various degrees, and reduced the content of-OH and nitrogen compounds in coke. The H2 content in the gas gradually increased. When 40% DCLR was added, the maximum tar yield was 22.79%, and the maximum H2 yield was 37.12%. At 60% DCLR, the lowest semi-coke yield was 65.01%, and the highest gas yield was 14.65%. The co-pyrolysis of SJC and DCLR can be divided into three stages. The first was the dry degassing stage, during which the adsorbed gas and small-molecule gas were removed on the coal surface at room temperature to 350 °C. The second stage (350 °C–650 °C) was the intense pyrolysis reaction stage, during which a large number of volatiles were obtained. The substantial weight loss rate peak appeared around 450 °C. The weight loss rate of pyrolysis gradually increased with increasing DCLR dosage. The co-pyrolysis of SJC and DCLR was not a simple sum between SJC and DCLR, which indicated a synergistic effect in the co-pyrolysis. The synergistic effect between SJC and DCLR enhances the interaction between free-radical fragments, thereby increasing the yield of pyrolysis tar. The third stage was the shrinkage of semi-coke from 650 °C to the end of the reaction. The polycondensation reaction between free-radical fragments to form solid coke with higher aromaticity, and H2 released.