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Landslides are regarded as significant geological hazards across the world, causing serious economic losses and casualties. The understanding on deformation characteristics and failure mechanisms of landslides plays the vital roles in slope stability evaluation and reinforcement design. In this study, the deformation characteristics and failure mechanism of the Xiaomiaoling talus slope were analyzed based on field monitoring data. In addition, as it was difficult to measure the shear strength parameters of the rock–soil mixture due to its complex spatial structure and variable material composition, a displacement back analysis based on the back-propagation neural network (DBA-BPNN) was proposed to determine the shear strength parameters of the rock–soil mixture. The analytical results show that deformation of the Xiaomiaoling talus slope was that of a typical traction landslide, which has the characteristics of progressive failure, and major slope deformation was triggered by excavation and rainfall. According to field monitoring data, the shear strength parameters of the rock–soil mixture could be determined. The predicted cohesion and internal friction angle of the rock–soil mixture were 10.84 kPa and 19.51°, respectively, and the predicted and test values were in good agreement. The method proposed in this paper can provide references for the design and construction in geotechnical engineering.

Double-wall steel sheet piles (DSSPs) are widely used in large-span cofferdams for docks due to their good performance against wave action during storm surges. This paper describes a study of the dynamic behavior of a DSSP cofferdam under wave action through flume tests and a numerical simulation that combined computational fluid dynamics (CFD) and the finite element method. The influences of the water level and wave height on the DSSP cofferdam were investigated experimentally and numerically. Tall waves in shallow water broke upon and impacted the seaside pile with large dynamic wave pressure, dramatically increasing the stress and displacement of the seaside pile. The overlap of the traveling and reflected waves increased the excess pore water pressure near the seaside pile due to taller overlapped waves and higher wave frequency. The DSSP cofferdam failed under the combined actions of the dynamic wave pressure and erosion of the landside seabed. The leakage and overflow of the breaking waves resulted in significant erosion of the landside seabed and greatly weakened the support of the seabed. The dynamic wave pressure then pushed the DSSP cofferdam until it failed. The simulation with the combined methods of CFD and FEM resulted in trends that were similar to those of the test measurements. Compared to the quasi-static method and pseudo-dynamic method, the results of the simulation via the present method were much closer to the test results because the simulation included the effects of breaking waves. The reinforced measure worked well to prevent the DSSP cofferdam in a sandy seabed foundation from continuous failures of deformation–leakage–erosion–tilting. However, it failed in a clay interlayer seabed foundation due to the large settlement.

As a reliable building foundation form, piles are driven into collapsible soil layers to ensure stability of foundations. Because of water immersion, significant subsidence occurs on collapsible loess; then negative skin friction emerges on the pile surface, which eventually causes serious bearing capacity failures of pile foundations. Relying on water immersion tests of multiple piles in Lanzhou, China, this study analyzed the influencing factors of negative skin friction for pile foundations in collapsible loess regions. The main factors studied in this research are cumulative relative collapse amount, pile type, and change in loess collapsibility. The results demonstrate that the maximum negative skin friction has a negative correlation to the cumulative relative collapse amount, which is determined by the degree of difficulty of the emergence of the shear fracture surface. Owing to the compaction effect of the driven pile and surcharge load of the exploded pile, their negative skin frictions increase in varying degrees compared to that of the bored concrete pile. At the same test site, the changes in loess collapsibility are mainly affected by natural moisture content and dry density. Increases in both the natural moisture content and dry density reduce the loess collapsibility, immersion settlement rate, and negative skin friction of pile. The loess collapsibility can be improved by surcharge loading and pre-watering to reduce the adverse effect of negative skin friction on pile foundations in engineering applications.

Large-diameter rock-socketed pile groups are an effective method for distributing bridge and traffic loads in long-span bridges. Currently, the bearing behavior of large-diameter rock-socketed pile groups in valley areas remains insufficiently understood. In order to understand the bearing behavior of large diameter rock-socketed pile group in valley area, three centrifuge model tests were carried out to simulate the mechanical characteristics of pile group with different slope angle. The results indicated that pile groups shown linear load-settlement responses until the ultimate load, and the settlement of pier cap was positively correlated with slope angle. There are obvious differences in the load sharing of single piles, and the existence of the slope angle exacerbated the differences in load sharing for single piles. Moreover, the tendency of axis force-depth was similar, showing that the axis force of the large-diameter rock-socketed pile decreased modestly in the overburden layer, and decreased steeply in the rock-socketed layer. The slope angle reduces the shaft resistance of the overburden layer, which reduces the bearing capacity of the group pile, and this negative effect increases with the slope angle. Accordingly, the valuable results obtained from the centrifugal model tests to guide the design and construction of large diameter rock-socketed pile group in valley area.

Mine water inrush is one of the major geological hazards that threaten safe production in coal mines. The accurate identification of mine water inrush sources plays a vital role in mine water disaster control, and it is the key to preventing mine water inrush incidents. Ninety-three water samples were extracted from the three types of aquifers in the Qinan coal mine. The cluster analysis method was then used to analyze 82 of the original water samples, and the other 11 water samples that did not meet the requirements were removed. Then, the remaining 82 water samples were regarded as training samples, and the principal component analysis was completed. Taking the scores of the principal components as the independent variable and the types of water inrush sources as the dependent variable, the multiple logistic regression recognition model was established. Meanwhile, this recognition model was used to recognize the types of mine water inrush sources and verify the recognition accuracy for the 82 training samples. The comprehensive recognition accuracy reached 86.6%, which is much higher than the traditional recognition methods of water inrush sources. Based on cluster analysis, the multiple logistic regression recognition model fully considers the ion content measurement errors and the complex relationships between the internal ions, and this recognition model is more reasonable and improves the accuracy of water inrush source recognition. This paper provides a new method for recognizing the problem of water inrush sources, which also provides an effective basis for mine water inrush prevention and control.

Compared with the traditional anti-slide pile, the h-type anti-slide pile has larger overall lateral stiffness, more reasonable structure stress, and can resist the greater landslide thrust. However, due to the short development history, there are relatively few studies on h-type anti-slide pile, and its structural design is not perfect. Numerical software Flac3d was used to optimize the structural parameters of h-type anti-slide pile, and the results showed that the optimal beam stiffness was 3 times of the front and rear piles, the optimal rear pile depth was 0.28 times of the length of the rear pile, and the front pile depth was 0.5 times of the length of the front pile.

The controlling criterion for differential settlement between the new and old subgrade of widened expressway is an important technical problem concerned by academia and engineering field. Based on an engineering project, finite element method was used to analyze the effects of foundation, embankment and road surface on the differential settlement, in which the foundation, embankment and pavement was considered as a whole structure, and the ultimate tensile strength was used to determine its strength. The calculation duration is from the construction of the original road to the post construction settlement of the widened road. The controlling criterion of differential settlement after bilateral widened expressway was explored. The analysis results show that the maximum differential settlement should be controlled in 5cm considering the mechanical response of pavement structure, and the integral analysis method is more reasonable to analyze the differential settlement of widened subgrade.

In order to study the application of distributed optical fiber in temperature monitoring of mass concrete, monitoring instruments are embedded in pile cap to carry out the field experiment. The results show that the distributed temperature fiber which is based on brillouin optical time-domain analysis (BOTDA) has the superiority of anti-jamming, corrosion resistance, high precision and continuous measurement. It can accurately reflect the temperature change, effectively guide the construction, and play a positive role in preventing the emergence of concrete cracks caused by temperature change. What’s more, optical fiber has small volume and less influence on engineering, which make it have a good application prospect.

The ultra-small textured surface of multicrystalline silicon solar cell, prepared by electroless chemical-etching method, shows an excellent anti-reflection property over a wide spectral bandwidth. A novel back surface protection method and front surface passivation method have been used in the multicrystalline solar cells with ultra-small textured surfaces. With these improvements, the back surface remains intact after the etch process and the efficient minority lifetime is apparently increased. The test result shows that the solar cell with ultra-small textured surface can obtain better electrical performances by these improvements.

Background The deep sea harbors the majority of the microbial biomass in the ocean and is a key site for organic matter (OM) remineralization and storage in the biosphere. Microbial metabolism in the deep ocean is greatly controlled by the generally depleted but periodically fluctuating supply of OM. Currently, little is known about metabolic potentials of dominant deep-sea microbes to cope with the variable OM inputs, especially for those living in the hadal trenches—the deepest part of the ocean. Results In this study, we report the first extensive examination of the metabolic potentials of hadal sediment Chloroflexi , a dominant phylum in hadal trenches and the global deep ocean. In total, 62 metagenome-assembled-genomes (MAGs) were reconstructed from nine metagenomic datasets derived from sediments of the Mariana Trench. These MAGs represent six novel species, four novel genera, one novel family, and one novel order within the classes Anaerolineae and Dehalococcoidia . Fragment recruitment showed that these MAGs are globally distributed in deep-sea waters and surface sediments, and transcriptomic analysis indicated their in situ activities. Metabolic reconstruction showed that hadal Chloroflexi mainly had a heterotrophic lifestyle, with the potential to degrade a wide range of organic carbon, sulfur, and halogenated compounds. Our results revealed for the first time that hadal Chloroflexi harbor pathways for the complete hydrolytic or oxidative degradation of various recalcitrant OM, including aromatic compounds (e.g., benzoate), polyaromatic hydrocarbons (e.g., fluorene), polychlorobiphenyl (e.g., 4-chlorobiphenyl), and organochlorine compounds (e.g., chloroalkanes, chlorocyclohexane). Moreover, these organisms showed the potential to synthesize energy storage compounds (e.g., trehalose) and had regulatory modules to respond to changes in nutrient conditions. These metabolic traits suggest that Chloroflexi may follow a “feast-or-famine” metabolic strategy, i.e., preferentially consume labile OM and store the energy intracellularly under OM-rich conditions, and utilize the stored energy or degrade recalcitrant OM for survival under OM-limited condition. Conclusion This study expands the current knowledge on metabolic strategies in deep-ocean Chlorolfexi and highlights their significance in deep-sea carbon, sulfur, and halogen cycles. The metabolic plasticity likely provides Chloroflexi with advantages for survival under variable and heterogenic OM inputs in the deep ocean. CxfeXiBUAN16RTa_sQ4c7H Video Abstract