Quality evaluation of ground improvement by deep cement mixing piles via ground-penetrating radar.

Deep cement mixing piles are a key technology for treating settlement distress of soft soil subgrade. However, it is very challenging to accurately evaluate the quality of pile construction due to the limitations of pile material, large number of piles and small pile spacing. Here, we propose the idea of transforming defect detection of piles into quality evaluation of ground improvement. Geological models of pile group reinforced subgrade are constructed and their ground-penetrating radar response characteristics are revealed. We have also developed ground-penetrating radar attribute analysis technology and established ground-penetrating radar technical system for evaluating the quality of ground improvement. We further prove that the ground-penetrating radar results integrating single-channel waveform, multi-channel section and attributes can effectively detect the defects and stratum structure after ground improvement. Our research results provide a rapid, efficient and economic technical solution for the quality evaluation of ground improvement in soft soil subgrade reinforcement engineering.

Coupling of electrochemical-temperature-mechanical processes in marine clay during electro-osmotic consolidation.

Electro-osmotic consolidation has been applied in several geotechnical engineering applications that contain a series of complex processes, including electrochemical processes, temperature changes, and mechanical evolution. To explore the combination of electrochemical-temperature-mechanical processes in marine clay, electro-osmotic consolidation experiments were conducted using a self-made electro-osmotic consolidation system under various durations and voltages. The following findings was obtained: (1) the change in the pH value increased during electro-osmotic consolidation and as the voltage rise; (2) the temperature increased with a rise in voltage in the initial stage of the experiments, which was induced by Joule heating; (3) the temperature rise promoted the electro-osmotic consolidation process, which included a rise in the coefficient of consolidation and a reduction in water content; (4) horizontal shrinkage occurred when the horizontal stress increment was greater than the critical stress condition. In addition, the volume difference reached a constant value, and was proportional to the voltage rise. After the discussion, a coupling analysis was conducted, which can help to better understand the mechanism of electro-osmotic consolidation and can provide reference for engineering applications.

Effects of manganese content and calcination temperature on Mn/Zr-PILM catalyst for low-temperature selective catalytic reduction of NOx by NH3 in metallurgical sintering flue gas.

The effects of manganese content, carrier calcination temperature, and catalyst calcination temperature of manganese-based zirconium pillared intercalated montmorillonite (Mn/Zr-PILM) catalysts were investigated for low-temperature selective catalytic reduction of NOx by NH3 (NH3-SCR) in the metallurgical sintering flue gas. The physicochemical properties of these catalysts can be characterized by X-ray diffraction (XRD), N2 adsorption-desorption isotherm, and temperature-programmed desorption of ammonia (NH3-TPD). The 10Mn/Zr400-PILM(300) catalyst had the highest NOx conversion under excess oxygen conditions (15 vol% oxygen) and reached 91.8% NOx conversion at 200 °C. It was found that when the loading of manganese was 10 wt.%, the catalyst had the highest catalytic activity and the manganese-active component was highly dispersed on the Zr-PILM surface. The optimal calcination temperature of the Zr-PILM was 400 °C because the catalyst pore size was concentrated at 1.92 nm and the catalyst had the most acidic sites. And the optimum calcination temperature of the catalyst was 300 °C. This was because excessive calcination temperature promoted the manganese oxide polymerization and reduced the catalytic activity of the catalyst.

Fabrication of manganese-based Zr-Fe polymeric pillared interlayered montmorillonite for low-temperature selective catalytic reduction of NOx by NH3 in the metallurgical sintering flue gas.

A series of Zr-Fe (Zr/Fe = 4:0, 3:1, 2:2, 1:3, 0:4) polymeric pillared interlayered montmorillonite loading 10 wt.% MnOx (Mn/Zr-Fe-PILM) were investigated for the selective catalytic reduction of NOx by NH3 (NH3-SCR) in metallurgical sintering flue gas. The X-ray diffraction (XRD), N2 adsorption-desorption isotherm, scanning electron microscope (SEM), and ammonia temperature-programmed desorption (NH3-TPD) were used to analyze the physicochemical property. The Fe polymerized with Zr exchanged to montmorillonite can improve the Mn/Zr-Fe-PILM low-temperature NOx conversion and N2 selectivity. The Mn/Zr-Fe-PILM (1:3) shows the highest NOx conversion between 140 and 180 °C. The XRD results suggest that the growth of crystalline ZrO2 phase is intensely restrained for the Fe2O3 migration into the ZrO2 lattice. The ZrO2 and MnOx have an excellent dispersion in montmorillonite. The N2 adsorption result illustrates that the increase of Fe molar content in the Zr-Fe-PILM support increases the catalyst-specific surface area. The NH3-TPD results elucidate that the Mn/Zr-Fe-PILM (1:3) has the most total acid sites. Therefore, the low-temperature catalytic activity of the Mn/Zr-Fe-PILM (1:3) has been assigned to the large specific surface area, abundant acid sites, and the dispersion of metallic oxides.

Sm-doped manganese-based Zr-Fe polymeric pillared interlayered montmorillonite for low temperature selective catalytic reduction of NO x by NH3 in metallurgical sintering flue gas.

In this work, Sm-doped manganese supported Zr-Fe polymeric pillared interlayered montmorillonites (Mn/ZrFe-PILMs) were prepared for the low-temperature selective catalytic reduction (SCR) of NO x with NH3 in metallurgical sintering flue gas. These pillared interlayered montmorillonite catalysts were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy, nitrogen adsorption-desorption isotherm, ammonia temperature-programmed desorption, and hydrogen temperature-programmed reduction to study the influence of Sm doping on the SCR performance. The ZrFe-PILMs with a Mn/Sm molar ratio of 18 : 2 showed the excellent SCR activity among these catalysts, where a 95.5% NO x conversion ratio at 200 °C at a space velocity of 20 000 h-1 was obtained. Samarium oxide and manganese oxides were highly dispersed on the ZrFe-PILMs with different Mn/Sm molar ratios by the XRD results and SEM-EDS results. Meanwhile, the Mn-Sm/ZrFe-PILM (18 : 2) had the lowest temperature hydrogen reduction peak by H2-TPR results, which indicated that it had the lowest active bond energy on its surface. And the NH3-TPD results expressed that the Mn-Sm/ZrFe-PILM (18 : 2) had the most acidic sites, especially the weakly acidic sites. Therefore, it was found that the introduction of a small amount of Sm (Mn : Sm = 18 : 2) to Mn/ZrFe-PILM can significantly improve catalytic activity by the increased active oxygen component and the surface acidity.