scholarly journals Stability Analysis of Tunnel Face Reinforced with Longitudinal Fiberglass Dowels Together with Steel Pipe Umbrella

Symmetry ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2069
Author(s):  
Kaihang Han ◽  
Xuetao Wang ◽  
Beibei Hou ◽  
Cheng-yong Cao ◽  
Xing-Tao Lin
Keyword(s):  
Prediction Model ◽  
Urban Areas ◽  
Steel Pipe ◽  
Analytical Prediction ◽  
Tunnel Face ◽  
Reinforcement Density ◽  
Face Stability ◽  
Adjacent Structures ◽  
Tunnel Face Stability ◽  
The Impact

When tunnels are constructed under difficult geotechnical conditions in urban areas, tunnel face stability is one of the main issues to be addressed. To ensure tunnel face stability and reduce the impact of tunneling on adjacent structures, a few alternative procedures of ground reinforcement should be adopted, which includes reinforcing the soil ahead of the face using longitudinal fiberglass dowels alone or together with a steel pipe umbrella. It is of great academic value and engineering signification to reasonably determine the limit reinforcement density of these ground reinforcements. In this paper, an analytical prediction model is proposed by using the limit analysis method to analyze the tunnel face stability, and the favorable effects of longitudinal fiberglass dowels and steel pipe umbrella on tunnel face stability are investigated quantitatively. The analytical prediction model consists of a wedge ahead of the tunnel face, distributed force acting on the wedge exerted by overlying ground, and the support forces stem from the longitudinal fiberglass dowels. Moreover, sensitivity analysis is conducted to study the effect of the depth of cover, the tunnel shape, the reinforcement installation interval and the reduction factor on the required limit reinforcement density.

Tunnel Face Stability Study in Soft Shallow Tunnel

2014 ◽  
Vol 1079-1080 ◽  
pp. 170-176
Author(s):  
Jun Du ◽  
Zhi Rong Mei ◽  
Yong Zhao Chen
Keyword(s):  
Three Dimensional ◽  
Horizontal Displacement ◽  
Stability Study ◽  
Plastic State ◽  
Shallow Tunnel ◽  
Tunnel Face ◽  
Maximum Displacement ◽  
Face Stability ◽  
Tunnel Face Stability ◽  
The Impact

With Xiamen Jiaheyuan underground access as the project background, tunnel face stability of soft shallow tunnel was analyzed under the condition of no pre-reinforcement by means of three-dimensional finite element method. The results indicated that the ground was relaxed because the tensile stress appeared in front and top of tunnel face after excavation, at the same time, the ground into the plastic state around the tunnel face. From the point of view of deformation, the displacement of tunnel face were such as the longitudinal horizontal displacement reached the maximum, the vertical deposition following by, and the lateral horizontal displacement being the least. Further analysis showed that the longitudinal horizontal displacement in front of tunnel face mostly produced at 1.0D (one excavation width) distance before tunnel face, the maximum displacement was located at the center of tunnel face. The conclusions remind that engineers also pay attention to the tunnel face reinforcement in front and top of tunnel face to minimize the impact of surface environment during tunnel construction in soft shallow tunnels.

Abstract MP41: Implications of the Use of the New ACC/AHA Guidelines for Cardiovascular Disease Prevention in a Brazilian Cohort - The Elsa Brasil Study

Circulation ◽  
2015 ◽  
Vol 131 (suppl_1) ◽  
Author(s):  
Marcio S Bittencourt ◽  
Isabela Bensenor ◽  
Dora Chor ◽  
Paulo Vasconcelos ◽  
Paulo Lotufo
Keyword(s):  
Cardiovascular Disease ◽  
Primary Prevention ◽  
Prediction Model ◽  
Urban Areas ◽  
Absolute Risk ◽  
Adult Health ◽  
Older Individuals ◽  
Cvd Risk ◽  
The Impact ◽  
Brazilian Cohort

Introduction: The 2013 American College of Cardiology / American Heart Association (ACC/AHA) guidelines developed a new prediction model for cardiovascular disease (CVD) and suggested the use of a lower threshold of 7.5% 10 year hard CVD risk for primary prevention. The implications of the use of this model in other cohort and admixed races has not yet been tested. The current study sought to evaluate the potential impact of its use in a large Brazilian cohort. Methods: We have included 15105 participants of the (Brazilian Longitudinal Study of Adult Health) ELSA-Brasil study, a multicenter prospective study that enrolled civil servants aged 35 to 74 years in 6 different urban areas in brazil. We have calculated the both the Framingham risk score (FRS) and the new risk prediction model to the entire cohort, and estimated the impact of changing current recommendations based on the FRS and lipid targets to the new recommendations based on the absolute risk estimated by the new model. Results: The mean age was 52±9.1 years, with 8218 (54%) women. The race distribution included 52% white, 16% black, 28% mixed (brown), and 4% of other. While 19.2% (95% CI: 18.4 to 19.6) of the cohort would require statins for primary prevention accordion to prior recommendations, the new guidelines would recommend treatment for approximately 40.2% (95%CI: 39.4 to 41.0) of the cohort. A substantial increase in the population in whom statins are recommended occurred for males, from 23.3% (95%CI: 22.6 to 24.0%) to 55.7% (95%CI: 54.9 to 56.5), as well as females, from 16.6 (95%CI: 16.0 to 17.2) to 27.1 (95%CI: 26.4 to 27.8), and across all races and age levels (figure). Conclusion: The new ACC/AHA guidelines for primary prevention would approximately double the proportion of Brazilian adults in whom statins are indicated, mostly among older individuals. The epidemiological and economical impact of this changes are not yet known.

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