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Xianjie Hao,Zhuowen Sun,Yixin Zhao,Yiqiang Kang,Qian Zhang,Jinguo Cheng,Yingnan Wei,Zeyu Chen 대한토목학회 2021 KSCE Journal of Civil Engineering Vol.25 No.11
As a long-term urban transportation infrastructure, the stability of metro construction is very important. With the continuous expansion of urban metro network, metro adjacent construction is more and more frequently encountered. In this paper, taking the double-line adjacent construction problems encountered during excavation of Beijing New Airport Line metro in sandy cobble stratum as an example, the surface settlement caused by excavation of single-line metro and double-line adjacent metro is studied by computed tomography scan, electron microscope scanning, laboratory mechanical tests, orthogonal inversion and numerical simulation and other methods. The results show that 1) the sandy cobble particle size and sandy cobble distribution of Beijing sandy cobble samples are relatively dispersed, and the sandy cobble particle size is from 3 to 20 cm, of which the largest proportion is the sandy cobble particle size from 5 to 8 cm. 2) The internal friction angle of Beijing sandy cobble samples with different moisture content is from 27° to 40°, which is much larger than that of other soil samples. Even at the post-peak stage, the shear stress of some sandy cobble samples does not gradually tend to be gentle, but continuously increases or has secondary peaks. 3) For the excavation of double-line adjacent metro, the maximum settlement difference and the impact range of excavation are proposed as indicators to investigate the degree of interaction of the adjacent metro. 4) The results of numerical orthogonal analysis show that the width of surface settlement zone increases significantly with the increase of tunnel diameter and spacing when excavating adjacent metro in sandy cobble stratum, but the rate of increase with tunnel diameter (from 6 m to 14 m) almost reaches 2 times of the rate of increase with the spacing (from 3 m to 15 m). 5) The maximum settlement value of sandy cobble stratum increases with the increase of tunnel diameter and decreases with the increase of spacing. The orthogonal linear analysis shows that the influence of tunnel diameter on the maximum settlement value is much greater than the spacing. The maximum settlement increases with the increase of tunnel diameter, which is about 3.6 times of that with the decrease of spacing.
Congcong Zeng,Zhengzhong Yuan,Jiahui Zhu,Yintong Wang,Yongyong Xie,Ren Ye,Jinguo Cheng 한국한의학연구원 2021 Integrative Medicine Research Vol.10 No.-
Background Wenzhou has achieved great progress in the prevention and control of the growing coronavirus disease 2019 (COVID-19) pandemic, and traditional Chinese medicine (TCM) has played an indispensable role in this fight. This study aimed to investigate the efficacy of Maxingshigan-Weijing decoction (MWD) in treating infected patients. Methods This study was an open-label randomized controlled trial. Inpatients with mild or moderate symptoms caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection were randomly treated with routine supportive care alone or a combination of routine supportive care and MWD. The primary outcome was the rate of symptom (fever, fatigue, cough and difficulty breathing) recovery. Results Fifty-nine inpatients were enrolled, of whom 29 received routine supportive care alone (control group) and 30 received combination therapy (treatment group). The rate of symptom recovery was significantly higher in the treatment group than in the control group. The time to recovery of fever (3 vs. 7 days), fatigue (9 vs. 12 days), coughing (9 vs. 14 days) and difficulty breathing (4.5 vs. 9.5 days) was also significantly shorter in the treatment group (all p < 0.001). The syndrome score was lower after MWD treatment. However, neither group differed in the viral assay findings, hospitalization days, medication time or the rate of conversion to severe cases. Conclusions MWD increased the rate of symptom recovery and shortened the time to recovery of clinical symptoms without deterioration to death or critical care. These findings may provide opportunities for the use of complementary medicine in treating this infection. Clinical trial registration Chinese Clinical Trial Registry, ChiCTR2000030759. Background Wenzhou has achieved great progress in the prevention and control of the growing coronavirus disease 2019 (COVID-19) pandemic, and traditional Chinese medicine (TCM) has played an indispensable role in this fight. This study aimed to investigate the efficacy of Maxingshigan-Weijing decoction (MWD) in treating infected patients. Methods This study was an open-label randomized controlled trial. Inpatients with mild or moderate symptoms caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection were randomly treated with routine supportive care alone or a combination of routine supportive care and MWD. The primary outcome was the rate of symptom (fever, fatigue, cough and difficulty breathing) recovery. Results Fifty-nine inpatients were enrolled, of whom 29 received routine supportive care alone (control group) and 30 received combination therapy (treatment group). The rate of symptom recovery was significantly higher in the treatment group than in the control group. The time to recovery of fever (3 vs. 7 days), fatigue (9 vs. 12 days), coughing (9 vs. 14 days) and difficulty breathing (4.5 vs. 9.5 days) was also significantly shorter in the treatment group (all p < 0.001). The syndrome score was lower after MWD treatment. However, neither group differed in the viral assay findings, hospitalization days, medication time or the rate of conversion to severe cases. Conclusions MWD increased the rate of symptom recovery and shortened the time to recovery of clinical symptoms without deterioration to death or critical care. These findings may provide opportunities for the use of complementary medicine in treating this infection. Clinical trial registration Chinese Clinical Trial Registry, ChiCTR2000030759.
Numerical study of rock-breaking performance of cutters in heterogeneous sand cobble ground
Jin Guo,Xiangwei Kong,Liu Cheng,Xueyi Li 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.6
Further research into tunneling performance in heterogeneous sand cobble ground demands an accurate numerical model of actual formation. In this paper, the ground model composed of spherical sand and ellipsoidal cobble was constructed to study the rockbreaking performance by using the discrete element method. The shape and physical parameters of sand and cobble were obtained on the basis of field test data. Then, the ground model was constructed to simulate the rock-breaking process of the cutterhead. The results show that the center cutter has a high flat wear percentage. With the decrease in cobble content (CC), the cracks between cutters are not connected effectively, thereby resulting in lower rock-breaking quantity. Finally, the influences of CC on the optimal parameters and crack propagation were analyzed. The results indicate that the rock-breaking performance in the ground with a low CC can be improved by increasing penetration and reducing cutter spacing.