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In situ analysis performed by portable X-ray fluorescence (pXRF) spectroscopy was used to measure two different contact interfaces of dyke and marble in the Baiyinnuo'er Zn–Pb deposit located in Inner Mongolia, China. The limit of detection (LOD) standardisation method was used to assess pXRF readings through dividing readings into low, medium and high concentrations, and readings were screened according to the concentration range distribution. Spatial trend analysis and enrichment factor calculation were used for data processing. In both profiles of quartz porphyry−marble (Q−M) and granodiorite−marble (G−M), high values of Ca and Mg, and Si, Al and K, respectively, could be used to distinguish the distribution of marble and dykes. However, there were significant differences in the distributions of ore-forming elements between the two profiles. No ore-forming elements were enriched near the contact interface of the Q−M profile, but all ore-forming elements, such as Zn, Pb, Cu and Fe, were significantly enriched in the skarns located between granodiorite and marble. Therefore, the intrusion of granodiorite resulted in the enrichment of ore-forming elements, and provided metals for mineralisation. Based on the results of the calculated enrichment factor for the G−M profile, the enrichment degree of selected elements in descending order was Pb, Zn > Ca > Fe > Al, Si > K in skarns relative to granodiorite, and Pb, Fe > Si, Al > Zn > K > Ca in skarns relative to marble. Zn and Pb were enriched in skarns relative to granodiorite but partially depleted relative to marble, indicating the high background Zn and Pb in marble; therefore, marble could provide at least part of the Zn and Pb. As a consequence, the intrusion of granodiorite resulted in skarnisation and mineralisation, and introduced ore-forming elements including Zn, Pb, Cu and Fe, but marble also provided at least part of the Zn and Pb, and the deposit was considered to be a skarn Zn–Pb deposit. In situ geochemical analysis at the outcrop scale is a useful approach for research into geological processes including skarnisation and mineralisation, as well as determining the source of ore-forming materials.

With the acceleration of urban metro construction in the Midwest of China, the metro tunnel is inevitably crossing the collapsible loess site. For the metro tunnels in loess area, if the around potential water source is induced by external disturbance, the tunnel structure which is constructed or being built will be influenced in the affected area of loess collapsibility. In view of this, model tests were designed according to the different water source positions and tunnel lining forms to study the collapsibility of loess and the failure behavior of metro tunnel under high-pressure water environment. And fluid–solid coupling calculation was conducted under different conditions of water source pressure, water source distance and water source location. Furthermore, the results were compared and perfected by numerical analysis, and the distribution law of water pressure field, displacement field and the stress field of the tunnel were investigated. Based on the calculated results, the safety distance between the water source and the tunnel was extracted, and the influence degree of water gushing on the tunnel was divided, which provides the safety evaluation index for the loess tunnel in local-high-pressure water environment.

The influence of metro shield construction in congested urban areas on nearby buildings is of great concern in practice. In this study, 3D-FEM model, validated through comparison with field monitoring results were used to investigate the influence of Xi’an Metro Line 4 excavation on existing city wall of the Ming Dynasty at Heping Gate in loess ground. The research results were found to be in good agreement with field measurement results. Furthermore, the results indicated that because of pre-reinforcement by sleeve valve pipe grouting and supporting by I-shaped steel at openings, the surface settlement within the foundation area on the city wall is reduced by 4 mm compared with that without the reinforcement, and the settlement of the city wall structure is reduced by approximately 2.2 mm, which prevents excessive local heave of the city wall foundation and out-of-limit of inclination. Additionally, the settlement-time curves of the city wall structure and change laws of surface settlement slot were also obtained. This study provides a valid reference value for protecting historical buildings adjacent shield construction in similar loess areas.

Laying thermal insulation is one of the common thermal insulation measures to prevent frost damage of tunnels in cold regions and the performance of thermal insulation material directly determines the effectiveness of freeze-proofing and insulation of thermal insulation layer. As an important parameter for evaluating the performance of thermal insulation materials, thermal conductivity is generally affected by density, humidity, temperature and other factors, therefore this paper will mainly focus on when the air humidity in the tunnel is too high, the moisture absorption of insulation materials may occur in the humid environment for a long time, which will lead to the increase of moisture content of insulation materials. Hence tunnels in cold regions, generally exhibit lower temperature conditions, thus the water inside the insulation material is easy to freeze, which will greatly improve the thermal conductivity of the material and reduce its thermal insulation effect. Therefore, it is of great significance to study the thermal insulation performance of cold-regions tunnel thermal insulation materials after moisture absorption and complete freezing.

BACKGROUND: Autophagy plays an important role in cellular homeostasis. Epigallocatechin gallate (EGCG), a polyphenol derived from green tea, has been shown to elicit vascular protective effects. Our study aimed to investigate the protective effect of EGCG in an endothelial injury model induced by hydrogen peroxide (H(2)O(2)) and reveal the possible mechanisms. METHODS: Human vascular endothelial cells (HUVECs) were pretreatment with different concentration of EGCG, then exposed to H(2)O(2). Cell viability was measured with MTS assay. Apoptosis was evaluated with TUNEL staining and apoptosis-related protein was determined by western blot. Autophagy flux was assessed by transmission electron microscopy and LC3 plasmid transfection. Besides, the role mTOR in EGCG-mediated antioxidant responses was validated with siRNA transfection. RESULTS: The results showed that pretreatment with EGCG significantly improved the survival of HUVECs from H(2)O(2)-induced cell death. After exposed to H(2)O(2), EGCG upregulated the levels of Atg5, Atg7, LC3 II/I, and the Atg5–Atg12 complex in HUVECs, while downregulated apoptosis-related protein. Besides, EGCG inhibited the PI3K-AKT-mTOR signaling pathway. Knockdown of mTOR partially promoted EGCG-induced autophagy. CONCLUSIONS: These results suggest that EGCG induces autophagy by targeting the mTOR pathway, indicating that EGCG has the potential to prevent and treat oxidative stress-related cardiovascular diseases.

The Qingling–Bashan (QB) mountain region in southern Shaanxi mainly consists of strongly compressive zones from east to west, with tight folds and compressive fractures. There is a wide distribution of soft rocks of various types, such as phyllite and slate, accompanied by complex geological structures. Ironically, tunnel construction in these difficult grounds with complicated geological conditions embraces a high risk of extreme deformation due to various unpredictable reasons, which can frequently cause collapse and result in budget overruns during the construction period. Therefore, it is crucial to conduct effective countermeasures to eliminate or avoid such adverse impacts. This paper provides a case study on the “Yingfeng tunnel” (a tunnel constructed in soft rock consisting of a slate ground) based on a geological survey, indoor experiments and in situ monitoring. A successive rock mass deformation resulted in the tunnel lining seriously intruding into construction clearance and some other sections, even collapsing during the construction. The maximum displacement amount was 62.5 cm, while the maximum deformation speed reached as high as 34.18 mm/day. Additionally, to evaluate the construction impacts of tunnelling-induced geo-hazards, an investigation on extreme deformation was conducted. Considering the time-dependent features of the rock mass deformation, the constraint-convergence method was used to put forward applicable countermeasures in this paper. Finally, from the feedbacks of monitoring results, extreme deformation of the Yingfeng tunnel was effectively controlled.

Postconstruction settlement that occurs before a tunnel is in operation may significantly influence the tunnel’s long-term stability. The current study investigates such a tunnel, a three-l...

Over the past couple of decades, as a new mathematical tool for addressing a number of tough problems, fractional calculus has been gaining a continually increasing interest in diverse scientific fields, including geotechnical engineering due primarily to geotechnical rheology phenomenon. Unlike the classical constitutive models in which simulation analysis gradually fails to meet the reasonable accuracy of requirement, the fractional derivative models have shown the merits of hereditary phenomena with long memory. Additionally, it is traced that the fractional derivative model is one of the most effective and accurate approaches to describe the rheology phenomenon. In relation to this, an overview aimed first at model structure and parameter determination in combination with application cases based on fractional calculus was provided. Furthermore, this review paper shed light on the practical application aspects of deformation analysis of circular tunnel, rheological settlement of subgrade, and relevant loess researches subjected to the achievements acquired in geotechnical engineering. Finally, concluding remarks and important future investigation directions were pointed out.

The classical shell theory (CST) without considering the shear deformation has been commonly used in the calculation of shells structures recently. However, the impact of theory of plates and shells subjected to the shear deformation on the calculation is increasingly pronounced along with the wide use of composite laminated structures. In this paper, based on first-order shear deformation theory (FSDT) of cylindrical shells, the displacement control differential equation of moderately thick cylindrical shells has been obtained, so has been the edge force at longitudinal of the shells. Meanwhile, a group of unit force is introduced to deduce the displacement of edge beam under the action of edge force. A join condition of moderately thick cylindrical ribbed shells is established according to the continuity of displacement as well. Most notably, the displacement analytical solution of bending problems of moderately thick cylindrical ribbed shells is obtained, which has profound theoretical significance for further improving the analytical solution of moderately thick cylindrical shells.

A great concern for the safety of large cross-section tunnels, which are being or to be built in the loess strata of China, is attracted. Generally, loess is a multi-phase porous medium and develops complex stress and strain variation while executing a tunnel project. Another problem is that the soil surrounding both tunnel arches is subjected to a complex loading due to the double excavation. To obtain an in-depth knowledge of the mechanism of tunnel deformation induced by the twin-tunnelling, we conducted comprehensive centrifuge tests, which can simulate and reproduce strictly the action process of twin-tunnelling. Through the model tests, the response of twin-tunnelling on loess stratum deformation was obtained. The investigations showed that with the increase of tunnel spacing, the stratum deformation distribution near the vault changes from a single-peak V shape to a double-peak W shape. Additionally, the height of the stratum pressure arch effect increases significantly. The settlement of the preceding tunnel is slightly larger than that of the latter tunnel, and the twin-tunnelling effect gradually decreases with the increase of tunnel spacing. Through comparative analysis of the different combinations of tunnel spacing and tunnel interval, the interaction between two tunnels with different spacing and interval during tunnelling was investigated, further optimizing the reasonable tunnel spacing and construction steps, as well as providing reference for tunnel route selection in the loess strata.

Centrifugal modeling technology has been applied to geotechnical engineering for more than half a century. It has been an important and indispensible means to simulate the geotechnical behavior because it has the same material, the similar boundary conditions and the same stress level. And it is also commonly used in tunnel-related research. Centrifugal tests of pipe-roof and small pipe grouting in tunnel were analyzed, the important effects of centrifugal tests on preliminary support of the tunnel were also emphasized. Problems often met in model tests of tunnelling were solved, such as structure model, modeling soil, preliminary support model and general programming of experiment proposal. The future development of centrifuges in tunnelling is also presented.

Structural health assessment is one of the key activities in maintaining the performance of a tunnel during its service life. Due to the development of modern detection technology, comprehensive structural health assessment system is being established for operating tunnels. To evaluate the actual operational state of Shitigou tunnel, overall detection of the liner crack, tunnel seepage, and liner void was conducted by employing the modern detection technology, such as crack width monitoring technology, concrete strength monitoring technology, and electromagnetic wave nondestructive monitoring technology. Through the statistical analysis of the detection results, the distribution characteristic, development law, and damage grade of structural defects were obtained. Tunnel liner cracks are mainly located on the middle wall; serious water leakage is encountered on the side wall, middle wall, and vault; the strength of foundation and liner structure of left tunnel does not meet the design requirement; the liner voids are mostly located at the tunnel entrance section, especially, on the tunnel vault; and the proportion of influence factors of structural defects should be considered. The research results presented for this study can serve as references for effective design and health assessment of existing multiarch tunnel projects.

Over the past few years, accompanied by big and frequent earthquakes, more attention was paid to the tunnel earthquake resistance. To reduce tunnel seismic damage and explore the reasonable aseismic measures, the tunnel earthquake disaster investigation was employed to analyze and summarize the tunnel seismic damage on the basis of Wenchuan earthquake. Fifty-two tunnels near the epicenter of Sichuan Province were investigated: Only 7 tunnels did not show structure damage, 6 tunnels suffered the most serious damage, and the rest appeared damage to various extents. It indicates that most serious seismic damage happens to fault fracture zone, followed by entrance and common section of the tunnel. Additionally, the results display that the typical seismic damage of tunnels is lining cracking, collapsing, dislocation, construction joints cracking, and uplifting of invert, and usually lining cracking and collapsing account for a larger proportion. Therefore, the tunnel aseismic design should emphasize the fault fracture zone and tunnel entrance. Tunnel design should adopt the composite lining structure with shock absorber and whole chain alternative grouting to prevent the lining cracking and collapsing in the seismic fortification zone.

Xi’an Bell Tower (the Bell Tower) is a state-level ancient relic in China. The vibration caused by metro will exert adverse effect on the Bell Tower. This paper aims at presenting 3D-FEM models to predict the peak period velocity (PPV) of rammed earth base when the metro passing through the Bell Tower. The calculation results are compared with those of field test. Both results were found to be in good agreement. Furthermore, the results indicated that the effect of shock absorption measures is significant. The shock absorption tracks can obviously decrease the vibration of the Bell Tower, and the maximum decrease of PPV of the rammed earth base is 78.91 %. The proposed prediction has the potential to be developed as a decision and management tool for the evaluation of the risk associated with the influence of vibration caused by metro on buildings in urban areas.

Compared with electrical strain gauges, fiber Bragg grating (FBG) sensing technology is a relatively novel method for tunnel structural health monitoring, which has a number of advantages including high accuracy, multiplexing, electromagnetic interference resistance, and good repeatability. In order to study the internal force of the tunnel liner and detect the potential safety hazards, series of strain monitoring tests of a loess tunnel, taking into account the complex stress and strain variation of the loess during tunnelling, were performed by employing the tandem linear FBG sensor arrays controlled by the wavelength division multiplexing (WDM) technology. The concrete strain has obvious linear characteristics over time in the early stage and then gradually tends to a stable value. Moreover, after the necessary temperature compensation, loess tunnel structure safety was assessed through the analysis of real-time strain and internal force of the liner concrete, and the FBG monitoring data and safety assessment results indicate that the safety factors of various liner sections all meet the code requirements, which verify the safety and stability of the tunnel liner structure. The FBG sensors-based in situ monitoring technology can be well applied in the loess tunnel structure safety assessment.

The performance of the ground treatment is always critical for a tunnel excavated in unstable stratum. Laodongnanlu Xiangjiang Tunnel (Changsha, China) across the Xiangjiang River will be constructed in a sandy gravel ground which is characterized by loose structure, extensive porosity, elevated sensitivity, poor stability, and a high groundwater table. Permeation grouting will be employed to improve the bearing capacity and mitigate groundwater movement into the excavation. In order to seek suitable injection parameters and grouting method, a field trial of vertical grouting was conducted in the sandy gravel stratum in river floodplain. A series of tests focusing on grout material, grouting sequence of boreholes, injection pressure, and grouting volume were performed to improve the sandy gravel mass strength and reduce water permeability. The examination of the results obtained during water pressure testing and core drilling on completion of the grouting trial successfully demonstrated that the specified injection criteria had led to an expected effect. Grouting control method of this saturated sandy gravel stratum was concluded after the test, which would contribute to the future pregrouting work during the tunnelling.

Due to an oversight, four references were cited incorrectly in the reference list of the original publication as well as in the text of the publication. The first names were used instead of the last names of the authors. In addition some author names were omitted inadvertently. The correct presentation of these references is shown below.