A comparative study of pseudo-static slope stability analysis using different design codes

Many researchers have developed new calculation methods to analyze seismic slope stability problems, but the conventional pseudo-static method is still widely used in engineering design due to its simplicity. Based on the Technical Code for Building Slope Engineering（GB 50330-2013） of China and the Guidelines for Evaluating and Mitigating Seismic Hazards in California（SP117）, a comparative study on the pseudo-static method was performed. The results indicate that the largest difference between these two design codes lies in determination of the seismic equivalence reduction factor( f;). The GB 50330-2013 code specifies a single value for f;of 0.25. In SP117, numerous factors,such as magnitude and distance, are considered in determining f;. Two case studies show that the types of slope stability status evaluated by SP117 are in agreement with those evaluated by the seismic time-history stability analysis and Newmark displacement analysis. The factors of safety evaluated by SP117 can be used in practice for safe design. However, the factors of safety evaluated by GB 50330-2013 are risky for slope seismic design.

Crystal structure and negative thermal expansion of solid solution Lu_2W_(3-x)Mo_xO_(12)

A new series of solid solutions Lu2W3-xMoxO12 （0.5≤r≤2.5） were successfully synthesized by the solid-state method. Their crystal structure and negative thermal expansion properties were studied using high-temperature X-ray powder diffraction and the Rietveld method. All samples of rare-earth ttmgstates and molybdates are found to crystallize in the same orthorhombic structure with space group Pnca and show the negative thermal expansion phenomena related to transverse vibration of bridging oxygen atoms in the structure. Thermal expansion coefficients （TEC） of Lu2W3_xMoxO12 are determined as -20.0× 10^-6 K^-1 for x=0.5 and -16.1×10^-6 K^-1 for x=2.5 but -18.6× 10^-6 and -16.9× 10^-6K^-1 for unsubstituted Lu2W3012 and Lu2M03012 in the identical temperature range of 200 to 800℃. High-temperature X-ray diffraction （XRD） data and bond length analysis suggest that the difference between W-O and Mo-O bond is responsible for the change of TECs after the element substitution in this series of solid solutions.

Effects of doping Fe cations on crystal structure and thermal expansion property of Yb_2Mo_3O_(12)

Crystal structures and thermal expansion properties of Yb2-xFexMo3O12（x=0.0,0.6,1.0,1.1,1.4） solid solutions have been studied by X-ray powder diffraction（XRPD） at different temperatures.Rietveld analysis of the XRPD data shows that Yb2-xFexMo3O12 solid solutions adopt orthorhombic structure and have variable thermal expansion coefficients controlled by the ratio of Yb^3＋ to Fe^3＋.Yb2Mo3O12 shows anisotropic negative thermal expansion property,induced by the reductions in average Yb-O-Mo angle and average apparent Mo2-O bond length with increasing temperatures.As more Yb^3＋ substituted by Fe^3＋,the linear thermal expansion coefficients of Yb2-xFexMo3O12 increase from negative to positive.A near-zero thermal expansion coefficient of 0.55×10^-6K^-1 for Yb0.6Fe1.4Mo3O12 is observed in the temperature range of 573-873 K.