Effect of earthquake on stability of subway station and ground motions of surrounding rock masses

The effect of earthquakes on the stability of the subway station and ground motions of surrounding rock masses, plays a key role in the seismic design of the subway station to avoid severe damage to subway station itself and adjacent structures. Most of the reported cases in the literatures on the effect of earthquake on ground motions focused on the ground motions without considering underground structures. In this study, the effect of earthquakes on the stability of the subway station, and ground motions of surrounding rock masses were investigated by using the Flac3d. The ground acceleration and safety factor of tunnel lining were highlighted. The results of the numerical analysis indicated the presence of a subway station has a great influence on ground motions, especially for the vertical ground acceleration. The ground acceleration increases with the decrease of buried depth. The amplification factor of ground acceleration is about 1.42. It exists an amplification region above the subway station with the width of 15 m. The safety factor of tunnel lining in subway station has a significant decrease in the maximum decrease rate of 67 %. The safety factor of tunnel lining except for tunnel crown and bottom changes periodic. Ground acceleration will induce extrusion or detach between surrounding rock masses and tunnel lining, and the direction of ground acceleration has a great influence on distribution of safety factor. The side wall and arch feet of tunnel lining is the most unfavorable part. Special attention should be paid to the side wall and arch feet of the subway station during seismic design

Effect of soft layer on seismic response of subway station in layered stratum

The seismic behavior of subway and highway tunnel has been an important topic followed the seismic damages of several structures in recent large earthquakes. Soft layer is often encountered in engineering site, and it is often located with normal strata. There have been limited literatures concerned on seismic performance of subway station with the presence of soft layer. Flac3D is employed to investigate the effect of soft layer on seismic response of subway station structure in earthquake. The effect of soft layer locating below subway station is firstly studied. Then the seismic response of subway station against location of soft layer is further investigated. The relative displacement, acceleration and safety factor of secondary lining, and internal force of central column are highlighted. It is found from numerical results that effects of the two cases are similar when soft layer locates below or above subway station and both beneficial for improving the safety of subway station compared with the case without soft layer. The case when soft layer locates below subway station is more preferable than the case above. It is also found that in the case when soft layer is within the range of subway station, it will greatly amplify the acceleration and internal force of secondary lining, especially for the part that is close to soft layer, and the influence degree gradually decreases with the increase of relative distance to soft layer. As a result, soft layer is generally beneficial for improving stability of subway station, but it should be avoided to be located within the range of subway station to ensure the stability of subway station

Effect of earthquake on stability of subway station and ground motions of surrounding rock masses

The effect of earthquakes on the stability of the subway station and ground motions of surrounding rock masses, plays a key role in the seismic design of the subway station to avoid severe damage to subway station itself and adjacent structures. Most of the reported cases in the literatures on the effect of earthquake on ground motions focused on the ground motions without considering underground structures. In this study, the effect of earthquakes on the stability of the subway station, and ground motions of surrounding rock masses were investigated by using the Flac3d. The ground acceleration and safety factor of tunnel lining were highlighted. The results of the numerical analysis indicated the presence of a subway station has a great influence on ground motions, especially for the vertical ground acceleration. The ground acceleration increases with the decrease of buried depth. The amplification factor of ground acceleration is about 1.42. It exists an amplification region above the subway station with the width of 15 m. The safety factor of tunnel lining in subway station has a significant decrease in the maximum decrease rate of 67 %. The safety factor of tunnel lining except for tunnel crown and bottom changes periodic. Ground acceleration will induce extrusion or detach between surrounding rock masses and tunnel lining, and the direction of ground acceleration has a great influence on distribution of safety factor. The side wall and arch feet of tunnel lining is the most unfavorable part. Special attention should be paid to the side wall and arch feet of the subway station during seismic design

Effect of earthquake on stability of subway station and ground motions of surrounding rock masses

The effect of earthquakes on the stability of the subway station and ground motions of surrounding rock masses, plays a key role in the seismic design of the subway station to avoid severe damage to subway station itself and adjacent structures. Most of the reported cases in the literatures on the effect of earthquake on ground motions focused on the ground motions without considering underground structures. In this study, the effect of earthquakes on the stability of the subway station, and ground motions of surrounding rock masses were investigated by using the Flac3d. The ground acceleration and safety factor of tunnel lining were highlighted. The results of the numerical analysis indicated the presence of a subway station has a great influence on ground motions, especially for the vertical ground acceleration. The ground acceleration increases with the decrease of buried depth. The amplification factor of ground acceleration is about 1.42. It exists an amplification region above the subway station with the width of 15 m. The safety factor of tunnel lining in subway station has a significant decrease in the maximum decrease rate of 67 %. The safety factor of tunnel lining except for tunnel crown and bottom changes periodic. Ground acceleration will induce extrusion or detach between surrounding rock masses and tunnel lining, and the direction of ground acceleration has a great influence on distribution of safety factor. The side wall and arch feet of tunnel lining is the most unfavorable part. Special attention should be paid to the side wall and arch feet of the subway station during seismic design

Effect of earthquake on stability of subway station and ground motions of surrounding rock masses

The effect of earthquakes on the stability of the subway station and ground motions of surrounding rock masses, plays a key role in the seismic design of the subway station to avoid severe damage to subway station itself and adjacent structures. Most of the reported cases in the literatures on the effect of earthquake on ground motions focused on the ground motions without considering underground structures. In this study, the effect of earthquakes on the stability of the subway station, and ground motions of surrounding rock masses were investigated by using the Flac3d. The ground acceleration and safety factor of tunnel lining were highlighted. The results of the numerical analysis indicated the presence of a subway station has a great influence on ground motions, especially for the vertical ground acceleration. The ground acceleration increases with the decrease of buried depth. The amplification factor of ground acceleration is about 1.42. It exists an amplification region above the subway station with the width of 15 m. The safety factor of tunnel lining in subway station has a significant decrease in the maximum decrease rate of 67 %. The safety factor of tunnel lining except for tunnel crown and bottom changes periodic. Ground acceleration will induce extrusion or detach between surrounding rock masses and tunnel lining, and the direction of ground acceleration has a great influence on distribution of safety factor. The side wall and arch feet of tunnel lining is the most unfavorable part. Special attention should be paid to the side wall and arch feet of the subway station during seismic design

Validity and applicability of the global leadership initiative on malnutrition criteria in non-dialysis patients with chronic kidney disease

IntroductionThere are no standardized assessment criteria for selecting nutritional risk screening tools or indicators to assess reduced muscle mass (RMM) in the Global Leadership Initiative on Malnutrition (GLIM) criteria. We aimed to compare the consistency of different GLIM criteria with Subjective Global Assessment (SGA) and protein-energy wasting (PEW).MethodsIn this study, nutritional risk screening 2002 first four questions (NRS-2002-4Q), Nutritional Risk Screening 2002 (NRS-2002), Malnutrition Universal Screening Tool (MUST), and Mini-Nutritional Assessment Short-Form (MNA-SF) tools were used as the first step of nutritional risk screening for the GLIM. The RMM is expressed using different metrics. The SGA and PEW were used to diagnose patients and classify them as malnourished and non-malnourished. Kappa (κ) tests were used to compare the concordance between the SGA, PEW, and GLIM of each combination of screening tools.ResultsA total of 157 patients were included. Patients with Chronic kidney disease (CKD) stage 1–3 accounted for a large proportion (79.0%). The prevalence rates of malnutrition diagnosed using the SGA and PEW were 18.5% and 19.7%, respectively. The prevalence of GLIM-diagnosed malnutrition ranges from 5.1% to 37.6%, depending on the different screening methods for nutritional risk and the different indicators denoting RMM. The SGA was moderately consistent with the PEW (κ = 0.423, p < 0.001). The consistency among the GLIM, SGA, and PEW was generally low. Using the NRS-2002-4Q to screen for nutritional risk, GLIM had the best agreement with SGA and PEW when skeletal muscle index (SMI), fat-free mass index (FFMI), and hand grip strength (HGS) indicated a reduction in muscle mass (SGA: κ = 0.464, 95% CI 0.28–0.65; PEW: κ = 0.306, 95% CI 0.12–0.49).ConclusionThe concordance between the GLIM criteria and the SGA and PEW depended on the screening tool used in the GLIM process. The inclusion of RMM in the GLIM framework is important. The addition of HGS could further improve the performance of the GLIM standard compared to the use of body composition measurements

Growth and Physiology of Two Psammophytes to Precipitation Manipulation in Horqin Sandy Land, Eastern China

The availability of water is the critical factor driving plant growth, physiological responses, population and community succession in arid and semiarid regions, thus a precipitation addition-reduction platform with five experimental treatments, was established to explore the growth and physiology of two psammophytes (also known as psammophiles) to precipitation manipulation in Horqin Sandy Land. Changes in coverage and density were measured, and antioxidant enzymes and osmoregulatory substances in both of the studied species were determined. Investigation results showed that the average vegetation coverage increased with an increasing precipitation, and reached a maximum in July. Under the −60% precipitation treatment, Tribulus terrestris accounted for a large proportion of the area, but Bassia dasyphylla was the dominant species in the +60% treatment. T. terrestris was found to have higher a drought stress resistance than B. dasyphylla. From days 4 to 7 after rainfall, B. dasyphylla under precipitation reduction showed obvious water stress. The malondialdehyde (MDA) content of B. dasyphylla was higher than that of T. terrestris, but that of B. dasyphylla had the lower relative water content (RWC). The MDA content in the precipitation reduction treatments of the two studied species was higher than that in the precipitation addition treatments from days 4 to 10. Peroxidase (POD) and superoxide dismutase (SOD) activity and the soluble proteins and free proline content of T. terrestris were higher than those of B. dasyphylla. The free proline content of T. terrestris and B. dasyphylla increased with increasing drought stress. Our data illustrated that T. terrestris had a higher drought stress resistance than B. dasyphylla, which was correlated with the augmentation of some antioxidant enzymes and osmoregulatory substance. The adaptive mechanism provides solid physiological support for an understanding of psammophyte adaptation to drought stress, and of community succession or species manipulation for desertified land restoration

Photosynthesis and Growth of Pennisetum centrasiaticum (C4) is Superior to Calamagrostis pseudophragmites (C3) during Drought and Recovery

Global warming and changes in rainfall patterns may put many ecosystems at risk of drought. These stressors could be particularly destructive in arid systems where species are already water-limited. Understanding plant responses in terms of photosynthesis and growth to drought and rewatering is essential for predicting ecosystem-level responses to climate change. Different drought responses of C3 and C4 species could have important ecological implications affecting interspecific competition and distribution of plant communities in the future. For this study, C4 plant Pennisetum centrasiaticum and C3 plant Calamagrostis pseudophragmites were subjected to progressive drought and subsequent rewatering in order to better understand their differential responses to regional climate changes. We tracked responses in gas exchange, chlorophyll fluorescence, biomass as well as soil water status in order to investigate the ecophysiological responses of these two plant functional types. Similar patterns of photosynthetic regulations were observed during drought and rewatering for both psammophytes. They experienced stomatal restriction and nonstomatal restriction successively during drought. Photosynthetic performance recovered to the levels in well-watered plants after rewatering for 6–8 days. The C4 plant, P. centrasiaticum, exhibited the classic CO2-concentrating mechanism and more efficient thermal dissipation in the leaves, which confers more efficient CO2 assimilation and water use efficiency, alleviating drought stress, maintaining their photosynthetic advantage until water deficits became severe and quicker recovery after rewatering. In addition, P. centrasiaticum can allocate a greater proportion of root biomass in case of adequate water supply and a greater proportion of above-ground biomass in case of drought stress. This physiological adaptability and morphological adjustment underline the capacity of C4 plant P. centrasiaticum to withstand drought more efficiently and recover upon rewatering more quickly than C. pseudophragmites and dominate in the Horqin Sandy Land