Stability and Failure Mechanism Analyses of the Zhenggang Landslide in Southwestern China

The Zhenggang landslide is an ancient complex landslide located at southeastern Tibetan Plateau, China. Due to intensive rainfalls in 2008 and heavy snowfalls in 2009, the Zhenggang landslide exhibited a high probability of reactivation once again. In this study, geological structure, matter features, and macrodeformations of the Zhenggang landslide (including Zone I and Zone II) were investigated for uncovering its formation mechanism and evolution tendency first, and then the stability and failure mechanism analyses of the Zhenggang landslide were conducted in detail by a combined limit equilibrium and finite element analysis method. Results of geological investigations indicate that the Zhenggang landslide has undergone sliding several times and is in a metastable state now. The distribution of the activity of the landslide is a retrogressive landslide in Zone I but an advancing landslide in Zone II. Such conclusions are further proved by the numerical stability and failure analyses

Descope of the ALIA mission

The present work reports on a feasibility study commissioned by the Chinese Academy of Sciences of China to explore various possible mission options to detect gravitational waves in space alternative to that of the eLISA/LISA mission concept. Based on the relative merits assigned to science and technological viability, a few representative mission options descoped from the ALIA mission are considered. A semi-analytic Monte Carlo simulation is carried out to understand the cosmic black hole merger histories starting from intermediate mass black holes at high redshift as well as the possible scientific merits of the mission options considered in probing the light seed black holes and their coevolution with galaxies in early Universe. The study indicates that, by choosing the armlength of the interferometer to be three million kilometers and shifting the sensitivity floor to around one-hundredth Hz, together with a very moderate improvement on the position noise budget, there are certain mission options capable of exploring light seed, intermediate mass black hole binaries at high redshift that are not readily accessible to eLISA/LISA, and yet the technological requirements seem to within reach in the next few decades for China

Serum Activity of Platelet-Activating Factor Acetylhydrolase Is a Potential Clinical Marker for Leptospirosis Pulmonary Hemorrhage

Pulmonary hemorrhage has been recognized as a major, often lethal, manifestation of severe leptospirosis albeit the pathogenesis remains unclear. The Leptospira interrogans virulent serogroup Icterohaemorrhagiae serovar Lai encodes a protein (LA2144), which exhibited the platelet-activating factor acetylhydrolase (PAF-AH) activity in vitro similar to that of human serum with respect to its substrate affinity and specificity and thus designated L-PAF-AH. On the other hand, the primary amino acid sequence of L-PAF-AH is homologous to the α1-subunit of the bovine brain PAF-AH isoform I. The L-PAF-AH was proven to be an intracellular protein, which was encoded unanimously and expressed similarly in either pathogenic or saprophytic leptospires. Mongolian gerbil is an appropriate experimental model to study the PAF-AH level in serum with its basal activity level comparable to that of human while elevated directly associated with the course of pulmonary hemorrhage during severe leptospirosis. Mortality occurred around the peak of pulmonary hemorrhage, along with the transition of the PAF-AH activity level in serum, from the increasing phase to the final decreasing phase. Limited clinical data indicated that the serum activity of PAF-AH was likely to be elevated in the patients infected by L. interrogans serogroup Icterohaemorrhagiae, but not in those infected by other less severe serogroups. Although L-PAF-AH might be released into the micro-environment via cell lysis, its PAF-AH activity apparently contributed little to this elevation. Therefore, the change of PAF-AH in serum not only may be influential for pulmonary hemorrhage, but also seems suitable for disease monitoring to ensure prompt clinical treatment, which is critical for reducing the mortality of severe leptospirosis

Application of the Resistivity in Quality Control of Concrete Durability for the Hong Kong–Zhuhai–Macao Bridge

Engineering uses the chloride ion diffusion coefficient as the durability of concrete quality control indicators under the marine environment, due to the chloride ion diffusion coefficient and the electrical resistivity of concrete parameters are reflected in the concrete pore structure, and resistivity testing is convenient, fast advantages, the resistivity alternative chloride ion diffusion coefficient for the durability of concrete quality control has practical significance. In this paper, using concrete mix of the immersed tube tunnel in Hong Kong–Zhuhai–Macao Bridge as research object, Under the standard curing conditions (temperature 20±2°C, 95% RH or more), Through the different ages of the specimen tested, Wenner method resistivity test results are more stable than the RCM chloride diffusion coefficient of the test results. Building the relationships between resistivity and chloride diffusion coefficient, and resistivity tests the specimen which is the entire structure of retention, compared with the result of the actual measured RCM method of chloride diffusion coefficient, average value of the diffusion coefficient what is concluded by resistivity is higher than real one, using the resistivity for the durability of control indicators is conservative, more demanding of the quality of concrete materials. Therefore, using resistivity as index to monitor changes of the materials is possible

Water–Binder Ratio Monitoring as a Quality Control Tool for the High-Performance Concrete Used in the Construction of the Submerged Tunnel

The designed service life of Hong Kong-Zhuhai-Macao Bridge is 120 years. Concrete quality control for the submerged tunnel of the project is an important work to assure the designed service life. This article is to present an advanced concrete performance prediction method based on water–binder ratio (w/b) monitoring, which is used to serve for concrete quality control. During experiments in the lab, the w/b of submerged tunnel concrete mix proportion was designed to fluctuate up and down, while the other compositions were kept constant. Concretes with different w/b were prepared. The w/b of fresh concrete was tested, followed by preparation of specimens for compressive strength and chloride diffusion coefficient tests. The compressive strength and chloride diffusion coefficient of the hardened concrete were tested. Relationships between the tested w/b and the compressive strength and chloride diffusion coefficient were established. The fitting curves were taken as the prediction models. During construction of submerged tunnel in field, w/b of fresh concrete was tested. The compressive strength and chloride diffusion coefficient of the concrete were calculated using the established models. In addition, specimens of the tested concrete were prepared and cured for compressive strength and chloride diffusion coefficient tests. Finally, the predicted results and the tested results were analyzed, and the predicted deviation was calculated. Results of the calculations show that the prediction deviations of compressive strength and chloride diffusion coefficient ar

Water–Binder Ratio Monitoring as a Quality Control Tool for the High-Performance Concrete Used in the Construction of the Submerged Tunnel

The designed service life of Hong Kong-Zhuhai-Macao Bridge is 120 years. Concrete quality control for the submerged tunnel of the project is an important work to assure the designed service life. This article is to present an advanced concrete performance prediction method based on water–binder ratio (w/b) monitoring, which is used to serve for concrete quality control. During experiments in the lab, the w/b of submerged tunnel concrete mix proportion was designed to fluctuate up and down, while the other compositions were kept constant. Concretes with different w/b were prepared. The w/b of fresh concrete was tested, followed by preparation of specimens for compressive strength and chloride diffusion coefficient tests. The compressive strength and chloride diffusion coefficient of the hardened concrete were tested. Relationships between the tested w/b and the compressive strength and chloride diffusion coefficient were established. The fitting curves were taken as the prediction models. During construction of submerged tunnel in field, w/b of fresh concrete was tested. The compressive strength and chloride diffusion coefficient of the concrete were calculated using the established models. In addition, specimens of the tested concrete were prepared and cured for compressive strength and chloride diffusion coefficient tests. Finally, the predicted results and the tested results were analyzed, and the predicted deviation was calculated. Results of the calculations show that the prediction deviations of compressive strength and chloride diffusion coefficient ar

Strength Performance and Stabilization Mechanism of Fine Sandy Soils Stabilized with Cement and Metakaolin

Enhancing strength performance while reducing cement consumption for soil stabilization is the key to improving the economic benefits of engineering construction projects like retaining structures of underground engineering, subgrade bases, and foundation reinforcement. This study employed metakaolin as the additive to realize these two aims. A series of compression and microstructural observation tests on cement- and metakaolin-stabilized fine sandy soils (CMSFSS) were conducted with different cement–metakaolin ratios, water–binder ratios, dosages of the binder (the mixture of cement and metakaolin), and curing ages. The influences of these factors on the mechanical performance of the CMSFSS were studied. The empirical relationships between compressive strength and these influence factors were discussed. Then, the strengthening mechanism of the CMSFSS at different curing ages was investigated. The results showed that the optimal cement–metakaolin ratio for fine sandy soil stabilization was 5:1, which did not change with the total consumption of cement and metakaolin. The compressive strength of the CMSFSS decreased linearly with the water–binder ratio but increased linearly with the curing age. Four empirical prediction formulas about these strength-influencing factors were summarized. The evolution of microstructural characteristics discovered by scanning electron microscope and mercury intrusion tests showed that the hydrated gels in CMSFSS were being formed during the early curing age and resulted in decreasing pore sizes with an initial rapid rate and then a slower rate over the curing age. The gradual disappearance of calcium hydroxide (by-products of cement hydration) over the curing age proved the promoting effect of metakaolin on the strength improvement of cement-stabilized fine sandy soils. This study can provide a reference for applying cement and metakaolin in soil stabilization practices