Large Pits Research Articles

Effect of alternating current and nitrate reducing bacteria on corrosion of X80 pipeline steel in Shenyang soil solution

In this work, electrochemical measurements and surface analysis techniques were used to investigate the effects of alternating current (AC) and nitrate reducing bacteria (NRB) on the corrosion behavior of X80 pipeline steel in the Shenyang soil extract solution. Either AC or NRB increases the corrosion rate of X80 steel samples, and the combination of AC and NRB can make the corrosion rate reach about 16.5 times of that without AC and NRB. Confocal laser scanning microscopy (CLSM) images show that the maximum pitting depth is up to 38.3 μm through the synergistic effect of AC and NRB. The data in this paper strongly confirms that AC and NRB synergistically accelerate the pitting formation of X80 pipeline steel, and lead to the generation of deeper and larger pits.

Unveiling unknowns: Practical application of InSAR for slope performance monitoring and risk management across multiple surface mines

The ability to monitor and predict slope failures in a surface mining setting is paramount for safely executing economically feasible open pit slope designs. Ground-based monitoring systems have proven to be effective for decades; however, with the geographical extensive nature of some mineral deposits, multiple open pit mining operations typically incur additional challenges of deploying and maintaining ground-based systems (compared with a single, large open pit). Monitoring strategies in the 2020s have significant opportunity to integrate satellite based InSAR (interferometric synthetic aperture radar) as part of the control measures depending on the expected failure mechanisms and risk profile. This paper uses case studies to explore the practical application of InSAR to ‘unveil unknowns’ for multiple open pit mining operations where ground monitoring capacity was previously constrained. Case studies include the retrospective analysis of historic slope failures, improving understanding of existing geotechnical hazards and improving engineering geological and slope stability models based on real slope performance data.

3D Insights into the Effects of Captivity on Wolf Mastication and Their Tooth Marks; Implications in Ecological Studies of Both the Past and Present.

Simple SummaryRecent years have seen major advances in the analysis of carnivore modifications to bone during feeding, based on the integration of 3D modeling and data science techniques, and with special attention being paid to tooth marks. From this perspective, carnivore tooth scores and pits have slowly converted into a protagonist in the identification of the carnivores producing them. The present study confronts the intra-species variability of tooth mark morphologies produced by Iberian wolves, taking into account not only different populations but also whether wild and captive wolves produce different shaped tooth marks. Here we show how, in the case of tooth scores, differences are notable and should thus be treated with caution. Further conclusions reveal that carnivore tooth pits are currently the most diagnostic elements for the study of carnivore feeding traces on bone, pending future studies that compare closely related taxa with sufficient intraspecific variability. In light of this, further investigation into the possible stress captivity may cause on these animals could be of great importance for both the study of past and present. If differences were to exist, these results could implicate a larger margin of error than previously perceived for some experimental samples, affecting both prehistoric and modern-day ecological studies.Human populations have been known to develop complex relationships with large carnivore species throughout time, with evidence of both competition and collaboration to obtain resources throughout the Pleistocene. From this perspective, many archaeological and palaeontological sites present evidence of carnivore modifications to bone. In response to this, specialists in the study of microscopic bone surface modifications have resorted to the use of 3D modeling and data science techniques for the inspection of these elements, reaching novel limits for the discerning of carnivore agencies. The present research analyzes the tooth mark variability produced by multiple Iberian wolf individuals, with the aim of studying how captivity may affect the nature of tooth marks left on bone. In addition to this, four different populations of both wild and captive Iberian wolves are also compared for a more in-depth comparison of intra-species variability. This research statistically shows that large canid tooth pits are the least affected by captivity, while tooth scores appear more superficial when produced by captive wolves. The superficial nature of captive wolf tooth scores is additionally seen to correlate with other metric features, thus influencing overall mark morphologies. In light of this, the present study opens a new dialogue on the reasons behind this, advising caution when using tooth scores for carnivore identification and contemplating how elements such as stress may be affecting the wolves under study.

Numerical investigations of long-term thermal performance of a large water pit heat storage

Water pit heat storage is an effective long-term heat storage. Experimental and theoretical investigations of a 60,000 m3 water pit heat storage in Dronninglund, Denmark was carried out with an aim to study its long-term thermal performance. Experimentally, detailed measurements were analyzed to monitor thermal behavior of the store, including flow rates, temperatures of the inlet and outlet flow, thermal stratification in the store and temperatures of the surrounding soil at four different depths. Theoretically, a simulation model of the water pit heat storage was developed based on the Type 343 model (ICEPIT) in TRNSYS. The calculated temperatures were compared to the measurements. The developed model was used to investigate the influence of soil properties and inlet arrangement on the thermal performance of the store. The result show that the simulation model predicts well the thermal behavior of the store. Over the whole year, the calculated average temperature of the store differed within ±4.7 K from the measured values. The measurements show that the annual charged and discharged heat are 12,787 MWh and 11,957 MWh respectively. The deviation of the charged and discharged energy between the simulation and the experiment did not exceed ±4%. The annual storage efficiency reached 90% in the second year of operation. The calculated ground temperatures were consistent with the measured ones at different depths. Measured heat loss of the store is 1392 MWh. As elucidated by the model, the heat loss from the cover contributed to 60% of the annual heat loss, while the heat loss from the sidewall and the bottom contributed 38% and 2% respectively. The influence of soil types on thermal performance of the store is significant. For a PTES surrounded by dry soil, the storage efficiency can reach 90%, while for a PTES surrounded by wet sandy gravel, the storage efficiency decreases by 7%. Change of the height of the middle inlet/outlet diffuser could slightly improve the storage efficiency by 1%. The restrains of the model were analyzed and the focus areas of further investigations were pointed out. The findings of the paper give good reference for researchers, designers and consultants in planning of a solar heating plant with a large water pit heat storage.

Cretaceous Lauraceae wood from El Rosario, Baja California, Mexico

A new wood type for the Baja California Cretaceous adds to the plant diversity so far known for the area where gymnosperms seem to be dominant. It was collected near El Rosario, Baja California, from rocks of the Rosario Formation, in a sedimentary sequence that comprises ca. 1200 m of non-marine to deep marine sediments from Upper Campanian to Lower Danian age. The wood is characterized by having semiring porous growth rings, predominantly radial multiples of 2–7 with occasional clusters and some solitary vessels, simple perforation plates, alternate intervascular pits, oval to large elliptical vessel element-ray pits with reduced borders, septate thin-walled fibers, 1–4 seriate heterocellular rays, scares paratracheal, vasicentric and marginal parenchyma and oil cells associated with ray parenchyma. All these characters are found in Lauraceae, however, none of the extant taxa of the family have all these characters and even among fossil woods the characters in the Baja California material are better described only among the diverse Laurinoxylon, but vessel grouping, growth ring type, absence of marginal parenchyma, and slightly thicker rays suggest the presence of a new taxon, Rosarioxylon bajacaliforniensis Cevallos-Ferriz, Catharina & Kneller. By the end of the Cretaceous the family formed part of the plant community that represents a western extension of vegetation types more completely described from areas in the margins of the southern limits of the Western Interior Sea. The new taxon is proposed to highlight anatomical differences and geographic isolation from similar taxa and further suggests a large distribution of Lauraceae in what appears to be conifer dominated communities.

Displacement Monitoring during the Excavation and Support of Deep Foundation Pit in Complex Environment

Taking a super large deep foundation pit project as an example, the horizontal displacement of crown beam and driveway, surface settlement, axial force of anchor cable, and underground water level in the construction process of the foundation pit are dynamically monitored and analyzed. The excavation deformation rule of the deep foundation pit and the influence of excavation on surrounding buildings are analyzed. The results show that, with the excavation of the foundation pit, the crown beam and driveway of the foundation pit incline towards the direction of the pit and eventually tend to be stable. The variation of axial force of the prestressed anchor cable in the first layer of the foundation pit is basically consistent with the variation of horizontal displacement time history. The variation trend of the groundwater level at each side of the foundation pit is different but tends to be stable in a short time. In the whole monitoring period, the cumulative settlement value of each area of the foundation pit is within the controllable range, but the surface settlement of the north side of the foundation pit and a surrounding building has not reached stability, so it is suggested to extend the monitoring time of settlement in the relevant area.

Analysis of deformation monitoring results of a deep and large foundation pit

Taking a deep and large foundation pit project as an example, the paper analyzed some developmental characteristics of its deformation during construction. The deformation included vertical displacements of the ground surface and horizontal displacements of deep soil surrounding the foundation pit. At the same time, the trends of the ground settlement were predicted based on the monitoring data. The analysis and predictions showed that: (1) The soil around the foundation pit was influenced by the excavation and supporting construction; (2) The vertical and horizontal displacements appeared some regular patterns of gradual development over time. In addition, there were certain differences in the trends of measuring points at different locations; (3) By fitting the monitoring data, the deformation of the foundation pit could be effectively predicted and offer a guidance to the engineering practice.

The economic potential of metalliferous sub-volcanic brines.

The transition to a low-carbon economy will increase demand for a wide range of metals, notably copper, which is used extensively in power generation and in electric vehicles. Increased demand will require new, sustainable approaches to copper exploration and extraction. Conventional copper mining entails energy-intensive extraction of relatively low-grade ore from large open pits or underground mines and subsequent ore refining. Most copper derives ultimately from hot, hydrous magmatic fluids. Ore formation involves phase separation of these fluids to form copper-rich hypersaline liquids (or ‘brines') and subsequent precipitation of copper sulfides. Geophysical surveys of many volcanoes reveal electrically conductive bodies at around 2 km depth, consistent with lenses of brine hosted in porous rock. Building upon emerging concepts in crustal magmatism, we explore the potential of sub-volcanic brines as an in situ source of copper and other metals. Using hydrodynamic simulations, we show that 10 000 years of magma degassing can generate a Cu-rich brine lens containing up to 1.4 Mt Cu in a rock volume of a few km3 at approximately 2 km depth. Direct extraction of metal-rich brines represents a novel development in metal resource extraction that obviates the need for conventional mines, and generates geothermal power as a by-product.

Multi-Criteria Analysis for the Selection of the Optimal Mining Design Solution—A Case Study on Quarry “Tambura”

Mining design is usually evaluated with different multiple-criteria decision-making (MCDM) methods when it comes to large open pit or underground ore mines, but it is not used on quarry sites. Since Croatia is mostly mining stone, the implementation of such methods in decision making of the quarry mine design is imperative but left out. In this paper, the PROMETHEE II and AHP decision-making methods are implemented on the quarry site to find out the best final quarry design contour. By implementing the MCDM methods, the best quarry model was chosen based on 22 different criteria parameters out of three final quarry designs. The chosen model is not only financially sound but also has the least environmental impact.

Heavy Metals Present in the Soils from Extremely Large Opencast Iron Mine Pit.

The mining areas have faced severe pollution by caustic metals. In this study, heavy metals (Cu, Zn, Cr, Cd, Pb and Ni) in the soil of an extremely large iron mine pit from Ningwu-Luohe metallogenic belt, one of the seven iron ore areas in China was characterized. SiO2 was predominant soil mineral composition as 57.0 ± 1.3 %, followed by considerable Al2O3 (23.1 ± 2.5 %) and Fe2O3 (8.58 ± 1.2 %). Cu, Zn, Cr, Cd, Pb and Ni had the range of 7.62-237, 97.8-313, 1.73-43.8, 0.119-0.512, 5.13-44.7 and 7.87-23.9mg/kg, respectively, wherein, Cu, Zn, Cr and Pb were likely to have relatively low concentration in the soil from the boom of mining pit. Comparatively, both Cu and Zn arose at the level of 1-fold higher than that of local background values, indicating that the soil from mining pit had been subjected to Cu and Zn accumulation. BCR (European Communities Bureau of Reference) sequential extraction analysis showed that these metals mainly existed in residual fraction, with averaged percentages of 42.0 ± 18 %, 70.3 ± 8.1 %, 76.6 ± 18 %, 30.2 ± 14 %, 52.5 ± 11 % and 61.0 ± 9.7 % for Cu, Zn, Cr, Cd, Pb and Ni, respectively. Geo-accumulation index indicates that the soil was moderately contaminated by Cu, practically uncontaminated or uncontaminated to moderately contaminated by Zn, while practically uncontaminated by Cr, Cd, Pb and Ni. There were just significant relationships between Zn and Cd and between Cd and Pb, indicating that Cd in the soil investigated possibly had at least two sources and for most of the elements the sources were different. The effects of pit depth and major soil composition on the distribution of trace metals varied depending on the element itself and its chemical forms.

Microtextures on quartz and zircon grain surfaces in the Barra del Tordo and Tesoro beaches, northwestern Gulf of Mexico

Surface features of quartz and zircon grains in the Barra del Tordo (PBT) and Tesoro (PT) beaches, NW Gulf of Mexico (GoM), were analyzed. The microtextures in the PBT and PT beaches were classified into mechanical, chemical, and mechanical/chemical origin. The quartz grains from the two beach areas were subrounded to rounded in shape. Rounded zircon grains in PT suggest that the sediments were derived by wind, long transport distance, and long residence time relative to PBT. Rounded quartz grains with the combination of bulbous and broken edges indicated a recycled provenance. Mechanical features such as V-shaped marks, impact scars, conchoidal fractures, and straight-curved grooves indicated a fluvial environment. Chemical features such as solution pits, crystal overgrowth, and adhering particles in quartz and zircon grains indicated a diagenetic environment and silica re-precipitation in a coastal environment. The association of mechanical (bulbous edge) and chemical (silica overgrowth, small and large solution pits) features in a single grain suggested a dual environment, that is, the combination of littoral and coastal environments. The sediments were also partly supplied by the coastal dunes located along the GoM coastal region and were redistributed by wave energy and littoral currents. Euhedral, subhedral, and unetched zircon grains in PBT and PT were mixed with rounded and etched grains, indicating a diverse provenance from crystalline rocks. In general, the microtextures identified on zircon and quartz grains reveal that sediments are influenced by wind, fluvial, and subaqueous marine environment and derived by nearby and distal sources.

The Borek Forest Camp: ‘Aktion 1005’ in the context of ‘Aktion Erntefest’

The text by the German historian Jens Hoffmann recalls how the SS concluded Aktion Reinhardt, with the mass extermination of the last Jewish internees of the forced labour camps on 3-4 November 1943, by Aktion Erntefest. About 43,000 Jews were then murdered, in Majdanek (18,000), Poniatowa (15,000), Trawniki (6,000). It tells the story of a labour Kommando of 61 Jews selected by the SS on the day of the Operation in Majdanek, to travel to the Borek forest near Chełm, sixty kilometres east of Lublin, and set about the task of opening six large pits and cremating the remains of 25,000 Soviet prisoners of war who had been executed there. Aktion 1005, decided by Heinrich Himmler and Heinrich Müller, head of the Gestapo, was carried out on the entire territory of the General Government, as well as on that of the occupied USSR, after the first tests carried out in Chełmno during the summer of 1942, and was entrusted to Paul Blobel, who was already responsible for the Babi Yar massacre (in September 1941).

Integrative taxonomy uncovers a new Culicoides (Diptera: Ceratopogonidae) biting midge species from Thailand

Fully understanding biodiversity often requires an integrated approach especially for small insects because species diagnostic morphological characters are limited. In this study, morphological characters and DNA barcodes were used to examine previously recognized genetically divergent lineages detected in the biting midge, Culicoides arakawae (Arakawa), from Thailand. Morphological examinations revealed that specimens belonging to one lineage are morphologically different from C. arakawae in shape of the paramere in males, and in the leg color pattern of both sexes. Therefore, a formal description is provided for this new species, Culicoides mahasarakhamense sp. nov. Based on morphological characters including a large and shallow palpal pit, one sac like spermatheca and male with parameres bent at base with large basal knob, the new species was assigned into the subgenus Meijerehelea Wirth and Hubert. Morphological differentiation including wing pattern and shape of spermatheca of the new species are discussed and compared with other members of this subgenus. Mitochondrial cytochrome c oxidase I sequence analysis indicated that this new species is different from other members of the subgenus Meijerehelea with minimum interspecific genetic divergence of 3.92%. Automatic Barcode Gap Discovery species delimitation analysis also supported the recognition of a new species. Phylogenetic analyses revealed that the new species is closely related to C. arakawae, consistent with morphological similarity of these species. Results of this study highlight the necessity of using integrated approach for Culicoides taxonomy.

Effect of amoxicillin on the enamel mineralization of SD rats

Objective: To determine whether amoxicillin had an effect on the enamel mineralization of SD rats. Methods: Eighteen SD rats were randomly divided into three groups. The rats in the control group were given distilled water. The rats in two experimental groups were administered 50 or 100 mg/kg amoxicillin by intragastric administration from day 3 to day 17 after birth. The general condition, the structure of liver and kidney, the enamel surface changes of mandibular first molars and incisors were observed. The changes of Ca/P ratio on enamel surface were analyzed by X-ray energy dispersive spectrometer (EDS). The surface morphology after phosphoric acid treatment was examined by scanning electron microscopy (SEM). Histological changes in the ameloblasts of mandibular incisors were analyzed by hematoxylin and eosin (HE) staining. Results: Compared with the control group, the general conditions as well as liver and kidney structures of SD rats in 50 and 100 mg amoxicillin groups had no significant differences. There was no obvious chalky changes on the first mandibular molars of SD rats in each group. All the incisors in 50 and 100 mg groups showed different degrees of chalkiness in the labial incisal 1/3 enamel. X-ray EDS analysis showed that the Ca/P ratios of occlusal and incisal 1/3 enamel in 50 and 100 mg groups (occlusal 1/3 of mandibular first molars: 1.51±0.03 and 1.52±0.02, incisal 1/3 of mandibular incisors: 1.46±0.01 and 1.43±0.01) was significantly lower than that in the control group (occlusal 1/3 of mandibular first molars: 1.67±0.41, incisal1/3 of mandibular incisors: 1.73±0.07) (P<0.05). However, there was no significant differences in the cervical 1/3 Ca/P ratio of mandibular first molars and incisors among the three groups (mandibular first molars: 1.56±0.04 for control group, 1.59±0.05 for 50 mg group and 1.57±0.04 for 100 mg group; incisors: 1.52±0.02 for control group, 1.47±0.01 for 50 mg group and 1.51±0.03 for 100 mg group) (P>0.05). SEM observation showed that the enamel rods of the first molars and incisors in the 50 and 100 mg group varied in size and arranged disorderly. The spaces between the enamel rods were larger than that in the control group and some areas even appeared large pits. HE staining showed that the gaps between ameloblasts in 50 and 100 mg groups were significantly wider than that in the control group. Conclusions: Intake of amoxicillin during the period of enamel development of SD rats might affect enamel mineralization.

Application Analysis and Problem Prevention of Cast-in-Situ Beamless Hollow Floor Construction Technique in Large Deep Foundation Pit

Cast-in-place concrete beamless hollow floor is more and more widely used in engineering, especially in basement engineering, due to its characteristics like increase of the structure height, enhancement of heat preservation, heat insulation, noise reduction, rapid construction speed and others. Based on engineering practice, the application of cast-in-situ beamless hollow floor cover in large deep foundation pit is studied. In order to improve the construction quality, the deformation and stress state of long-span hollow plate are analyzed by finite element simulation. By optimizing and improving the process and comparing the results, the process method which is helpful to improve the quality of finished products of beam-less floor under this condition is extracted.

Anchoring of a retaining structure with glass fibre strand anchors

In Copenhagen, Denmark, a large construction pit has been designed to facilitate the excavation for the basement of a new district in the city called “Postgrunden”. The retaining wall is constructed by sheet piles installed into the Copenhagen Limestone with the use of pre-drilling and with ground anchors in two levels. The construction pit as well as the anchors are temporary, however, both parts are left in the ground after construction of the basement has been concluded. Most of the anchors were constructed as normal steel strand anchors, however, at one location glass fibre anchors were found to be the best solution due to restrictions concerning installation under third party property. Therefore 82 ground anchors with glass fibre strands were installed. These anchors were the first of their type used in production in Denmark. However, in Denmark there is no Eurocode or National Annex on composite materials at the time of the design and therefore the designers had no direct standard to design by. The design of the glass fibre anchors was therefore based on the index of safety method from Eurocode 0 along with a set of fracture tests made in a laboratory. The tests were used for a statistical analysis that along with a required index of safety gave the characteristic ultimate resistance of the strands and the elastic modulus. During installation the contractor had to consider the different material behaviour of the glass fibre strands compared to the traditional steel strands, e.g. the brittle shear tolerance, that dictates the assembly of the glass fibre strands to steel strand couplers to allow for testing and prestressing of the anchors. Further, the glass fibre anchors are not as heavy and stiff as the traditional steel anchors, which added an extra challenge during installation below the ground water table. Anchor testing was performed using traditional anchor testing equipment. The hollow plunger jacks were chosen in respect to the long piston stroke required for the extra elongation of glass fibre strands due to a low modulus of elasticity. All anchors were tested with either suitability or acceptance test to a factor of 1.43 or 1.30 above the design load, respectively.

Influence of surface condition on the degradation behaviour and biocompatibility of additively manufactured WE43

The further development of future Magnesium based biodegradable implants must consider not only the freedom of design, but also comprise implant volume reduction, as both aspects are crucial for the development of higher functionalised implants, such as plate systems or scaffold grafts in bone replacement therapy. As conventional manufacturing methods such as turning and milling are often accompanied by limitations concerning implant design and functionality, the process of laser powder bed fusion (LPBF) specifically for Magnesium alloys was recently introduced. In addition, the control of the degradation rate remains a key aspect regarding biodegradable implants. Recent studies focusing on the degradation behaviour of additively manufactured Magnesium scaffolds disclosed additional intricacies when compared to conventionally manufactured Magnesium parts, as a notably larger surface area was exposed to the immersion medium and scaffold struts degraded non-uniformly. Moreover, chemical etching as post processing technique is applied to remove sintered powder particles from the surface, altering surface chemistry. In this study, cylindrical Magnesium specimens were manufactured by LPBF and surfaces were consecutively modified by phosphoric etching and machining. Degradation behaviour and biocompatibility were then investigated, revealing that etched samples exhibited the overall lowest degradation rates, but experienced large pit formation, while the reduction of surface roughness resulted in a delay of degradation.

A Numerical Investigation of the Deformation Mechanism of a Large Metro Station Foundation Pit under the Influence of Hydromechanical Processes

Considering the unique conditions of deep and large subway foundation pit excavation affected by heavy rainfall in soil-rock composite strata, this paper employs finite element numerical simulation methods to study foundation pit instability under the influence of heavy rainfall. According to the hydraulic coupling conditions caused by rainfall, a fluid-solid coupling numerical model for a deep and large subway foundation pit in soil-rock composite strata is established in this paper. By selecting the Anshan road station of Qingdao subway line 4 as the engineering background, various parameters related to foundation pit excavation affected by heavy rainfall at different excavation depths were analyzed. The study found that after the foundation pit was excavated, the surrounding pore water pressure decreased and the pore water pressure near the ground surface increased rapidly due to rainfall. As the horizontal distance from the foundation pit increased, the pore water pressure at the same depth also increased. The excavation of the foundation pit caused uplift of the bottom of the pit. After rainfall, the uplift value decreased compared with that before rainfall. With increasing excavation depth, the decreased value of the bottom uplift decreased and then increased. The rainfall caused the horizontal displacement of the pit walls on both sides of the pit to increase. When the excavation depth was 10 m, the horizontal displacements on both sides of the pit were equivalent. When the excavation depth was 20 m, the horizontal displacement was concentrated in the first 10 m; when the excavation depths were 30 m and 40 m, the horizontal displacement was concentrated in the first 13 m. This finding shows that when the foundation pit was affected by rainfall, the sidewall collapsed at a distance of 13 meters from the ground. As the excavation depth increased, the depth of excavation instability was closer to the bottom of the pit. The research in this paper can provide a reference for the construction of deep and large foundation pits in similar composite ground conditions that are affected by rainfall.

Impact of the Surface and Microstructure on the Lubricative Properties of MoS2 Aging under Different Environments.

Molybdenum disulfide (MoS2) with a hydrophobic property and layered structure possesses an excellent lubricative property and has been widely used as a lubricant in various areas, including satellites, aircraft, and new energy vehicles. Aging is a ubiquitous phenomenon in MoS2 and plays a key role in its tribological application for shortening its service life. The effect of the surface and microstructure on the lubricative properties of MoS2 aging under different environments, including deionized water (DI water), ultraviolet/ozone (UV/Ozone), and high-temperature, was investigated. First, the lubrication of MoS2 transiently degrades because of physical adsorption and recovers after mechanical removal. The lubrication of MoS2 also degrades slightly when its surface becomes hydrophilic, thereby enhancing the adhesion energy due to atomic oxygen interaction under UV/Ozone exposure. Second, the lubrication of MoS2 degrades irreversibly because of the formation of stripes with the destroyed structures under accelerated aging. The lubrication of MoS2 further degrades with the formation of small triangular pits under high-temperature annealing. Finally, the lubrication of MoS2 deteriorates due to the destroyed structure and complete oxidation. The severe aging of MoS2 is accompanied with large triangular pits due to anisotropic oxidation etching of MoS2. The lubrication failure of MoS2 was determined on the basis of structural defect formation and surface property degradation induced by the extent of oxygen diffusion. The enhanced out-of-plane deformation due to the reduced out-of-plane stiffness and the increased energy barriers of defects are fundamentally responsible for the lubrication degradation of MoS2 at the atomic scale. These findings can provide new insights into the atomic-scale mechanism underlying the lubrication failure of MoS2 and pave the way for the realization of MoS2-based lubrication application under various environments.

Construction Technique of Vertical Shafts Excavation Above Subway Tunnel

Taking the foundation pit construction of the section K0 + 700 ~ + 900 of Shuangjiehe Road, Tinghai Road and other underground roads in Qianhai District of Shenzhen as an example, this paper introduces a new key construction technology of deep and large foundation pit excavation in the coastal area of reclamation to control the uplift and deformation of underground subway, which effectively utilizes the principle of space–time effect. Based on the number of finite difference software FLAC 3D numerical analysis, the skip excavation method and key construction parameters are simulated and optimized. The monitoring data show that the excavation method, sequence and construction protection measures have significant effect on the deformation control of subway tunnel, which can provide reference for similar projects.