Assessing cutter-rock interaction during TBM tunnelling in granite:Large-scale standing rotary cutting tests and 3D DEM simulations

The widespread utilisation of tunnel boring machines(TBMs)in underground construction engineering requires a detailed investigation of the cutter-rock interaction.In this paper,we conduct a series of largescale standing rotary cutting tests on granite in conjunction with high-fidelity numerical simulations based on a particle-type discrete element method(DEM)to explore the effects of key cutting parameters on the TBM cutter performance and the distribution of cutter-rock contact stresses.The assessment results of cutter performance obtained from the cutting tests and numerical simulations reveal similar dependencies on the key cutting parameters.More specifically,the normal and rolling forces exhibit a positive correlation with penetration but are slightly influenced by the cutting radius.In contrast,the side force decreases as the cutting radius increases.Additionally,the side force shows a positive relationship with the penetration for smaller cutting radii but tends to become negative as the cutting radius increases.The cutter's relative effectiveness in rock breaking is significantly impacted by the penetration but shows little dependency on the cutting radius.Consequently,an optimal penetration is identified,leading to a low boreability index and specific energy.A combined Hertz-Weibull function is developed to fit the cutter-rock contact stress distribution obtained in DEM simulations,whereby an improved CSM(Colorado School of Mines)model is proposed by replacing the original monotonic cutting force distribution with this combined Hertz-Weibull model.The proposed model outperforms the original CSM model as demonstrated by a comparison of the estimated cutting forces with those from the tests/simulations.The findings from this work that advance our understanding of TBM cutter performance have important implications for improving the efficiency and reliability of TBM tunnelling in granite.

Improving school physical education to increase physical activity and promote healthy growth of Chinese school-aged children Time for action

Throughout its more than 5000-year history, China has a long tradition of encouraging active engagement in physical and sport activities This enduring tradition, however, has been facing some major headwinds as China continues to expe- rience demographic and environmental changes related to aging, urbanization, and lifestyle shifts.

The study of college secondary department student status management and countermeasures——as KunmingUniversity of engineering secondary departments for case analysis

The management of College Students’ status is a professional policy work. The point of regulating college students’learningbehavior is registration management. According to the analysis on the issue of popular education stage of college registration management,it’s important to reinforce the registration management of affi liated college and put forward work ideas, formulate detailed measures. Thatcan regulate and optimize students’ learning behavior and promote school spirit, teaching style, study style, improve the effectiveness of theeducation of students.

Teachers' Reflective Practices in Implementing Assessment for Learning Skills in Classroom Teaching

Purpose:This article examines how 34 teachers self-assessed their work with the nine Assessment for Learning(AfL)strategies in teaching and their own suggestions for improvement as evidenced by the reflective statements given on reflection forms.Design/Approach/Methods:The sample was a group of 34 teachers from 10 primary schools and 10 kindergartens who have participated in the project.School Development Officers(SDOs)were assigned to conduct class observations in the schools,in which they recorded whether the teachers had used the AfL strategies in teaching.The SDOs would also share and discuss the comments with the teachers who had returned the self-reflection forms in which they wrote their feedback on the research questions.Findings:The findings show that teachers in kindergartens and teachers in primary schools might have different emphases on the nine AfL strategies in teaching.Their own suggested room for improvement in practicing AfL skills has provided insights for enhancing teaching effectiveness.Originality/Value:We propose that reflective practices can generate a"reflective spiral"of planning,acting,observing,and then reflecting.The study shows that reflective practitioners become professional experts who are able to assure thequality of teaching by self-enhancement and self-improvement.