Stability evaluation method of large cross-section tunnel considering modification of thickness-span ratio in mechanized operation

Purpose-This study aims to research the large cross-section tunnel stability evaluation method corrected after considering the thickness-span ratio.Design/methodology/approach-First,taking the Liuyuan Tunnel of Huanggang-Huangmei High-Speed Railway as an example and taking deflection of the third principal stress of the surrounding rock at a vault after tunnel excavation as the criterion,the critical buried depth of the large section tunnel was determined.Then,the strength reduction method was employed to calculate the tunnel safety factor under different rock classes and thickness-span ratios,and mathematical statistics was conducted to identify the relationships of the tunnel safety factor with the thickness-span ratio and the basic quality(BQ)index of the rock for different rock classes.Finally,the influences of thickness-span ratio,groundwater,initial stress of rock and structural attitude factors were considered to obtain the corrected BQ,based on which the stability of a large cross-section tunnel with a depth of more than 100 m during mechanized operation was analyzed.This evaluation method was then applied to Liuyuan Tunnel and Cimushan No.2 Tunnel of Chongqing Urban Expressway for verification.Findings-This study shows that under different rock classes,the tunnel safety factor is a strict power function of the thickness-span ratio,while a linear function of the BQ to some extent.It is more suitable to use the corrected BQ as a quantitative index to evaluate tunnel stability according to the actual conditions of the site.Originality/value-The existing industry standards do not consider the influence of buried depth and span in the evaluation of tunnel stability.The stability evaluation method of large section tunnel considering the correction of overburden span ratio proposed in this paper achieves higher accuracy for the stability evaluation of surrounding rock in a full or large-section mechanized excavation of double line high-speed railway tunnels.

Analytical study on pretensioned bolt-cable combined support of large cross-section tunnel

To study the mechanical responses of large cross-section tunnel reinforced by pretensioned rock bolts and anchor cables, an analytical model is proposed. Considering the interaction between rock mass and bolt-cable support, the strain softening characteristic of rock mass, the elastic-plastic characteristic of bolt-cable support, and the delay effect of installation are considered in the model. To solve the different mechanical cases of tunneling reinforced by bolt-cable support, an analytical approach has been put forward to get the solutions of stress and displacement associated with tunneling. The proposed analytical model is verified by numerical simulation. Moreover, parametric analysis is performed to study the effects of pretension force,cross-section area, length, and supporting density of bolt-cable support on tunnel reinforcement, which can provide references for determining these parameters in tunnel design. Based on the analytical model, a new Ground Response Curve(GRC)considering the reinforcement of bolt-cable support is obtained, which shows the pretension forces and the timely installation are important in bolt-cable support. In addition, the proposed model is applied to the analysis of the Great Wall Station Tunnel, a high-speed railway tunnel with a super large cross-section, which shows that the analytical model of bolt-cable support was a useful tool for preliminary design of large cross-section tunnel.

Leakage of an eagle flight feather and its influence on the aerodynamics

We investigate how the barb of bird feathers is changed along both the rachis and barb.To investigate the microstructures and the mechanical behaviors of barbs,a series of barbs are manually cut from an eagle’s primary feather to observe the cross sections.Aλ-like cross section with a tiny hook is observed at the right feet at each section.Afterwards,a measurement of the setup system is developed to evaluate the leakage ratio of a feather followed by a numerical predicting approach based on the CFD method.It is found that the air leakage increases linearly against the pressure,and the predicted results coincide well with the experimental results.Finally,the influences of leakage of the flight feather on both steady and unsteady aerodynamics are studied.

Changing profile of lung cancer clinical characteristics in China:Over 8-year population-based study

Background:Although examinations and therapies for bronchial lung cancer,also called lung cancer(LC),have become more effective and precise,the morbidity and mortality of LC remain high worldwide.Describing the changing profile of LC characteristics over time is indispensable.This study aimed to understand the changes in real-world settings of LC and its characteristics in China.Methods:In this study,119,785 patients were enrolled from 2012 to 2020 in the Shanghai Pulmonary Hospital.The patients’medical records were extracted from the hospital’s database.Demographic characteristics,general clinicopathological information,and blood coagulation indices at the initial diagnoses were analyzed using the Kruskal-Wallis,Nemenyi,chi-squared,and Bonferroni tests.Changes in demographic characteristics during the 8-year study period,namely dynamic changes among different stages and different pathological types,were evaluated.Results:The percentages of female(from 38.50%[323/839]in 2012 to 48.29%[5112/10,585]in 2020)and non-smoking LC(from 69.34%[475/685]to 80.48%[8055/10,009])patients increased significantly during the study period,with a trend toward a younger age at diagnosis(from 3.58%[30/839]to 8.99%[952/10,585]).Over the study period,the proportion and absolute number of lung adenocarcinoma cases increased(from 67.97%[433/637]to 76.31%[6606/8657])while the proportion of lung squamous cell carcinoma decreased(from 21.19%[135/637]to 12.08%[1046/8657]).Comprehensive driver gene mutation examination became more common,and epidermal growth factor receptor(EGFR)mutation occurred more frequently in female vs.male(62.03%[12793/20625]vs.29.90%[8207/27,447])and non-smoking vs.smoking(53.54%[17,203/32,134]vs.23.73%[3322/13,997])patients(both P<0.001).The distribution of the common driver genes differed among different stages of LC.EGFR mutation was detected most frequently at each stage,and other driver gene alterations were more common in advanced stages(P<0.001).The combination of chemotherapy,targeted ther-apy,and immunotherapy,as a comprehensive management regimen,gradually became predominant over the study period(P<0.001).A hypercoagulable state was shown in advanced-stage LC patients and patients with the anaplastic lymphoma kinase fusion,indicated by significantly elevated levels of d-dimer,fibrinogen,and fibrinogen degradation products.Conclusions:This study comprehensively depicted the changing characteristics of Chinese LC patients over an 8-year period to provide preliminary insights into LC treatment.Trial registration:ClinicalTrials.gov,NCT05423236.